draft-ietf-tls-protocol-03.txt   draft-ietf-tls-protocol-04.txt 
Transport Layer Security Working Group Tim Dierks Transport Layer Security Working Group Tim Dierks
INTERNET-DRAFT Consensus Development INTERNET-DRAFT Consensus Development
Expires September 22, 1997 Christopher Allen Expires April 28, 1998 Christopher Allen
Consensus Development Consensus Development
May 21, 1997 October 28, 1997
The TLS Protocol The TLS Protocol
Version 1.0 Version 1.0
<draft-ietf-tls-protocol-03.txt> <draft-ietf-tls-protocol-04.txt>
Status of this memo Status of this memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or made obsolete by other months and may be updated, replaced, or made obsolete by other
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To learn the current status of any Internet-Draft, please check the To learn the current status of any Internet-Draft, please check the
1id-abstracts.txt listing contained in the Internet Drafts Shadow 1id-abstracts.txt listing contained in the Internet Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim). Rim).
Abstract Abstract
This document specifies Version 1.0 of the Transport Layer Security This document specifies Version 1.0 of the Transport Layer Security
(TLS) protocol, which is at this stage is strictly based on the (TLS) protocol. The TLS protocol provides communications privacy
Secure Sockets Layer (SSL) version 3.0 protocol, and is to serve as over the Internet. The protocol allows client/server applications to
a basis for future discussions. The TLS protocol provides communicate in a way that is designed to prevent eavesdropping,
communications privacy over the Internet. The protocol allows tampering, or message forgery.
client/server applications to communicate in a way that is designed
to prevent eavesdropping, tampering, or message forgery.
Table of Contents Table of Contents
Status of this memo 1 Status of this memo 1
Abstract 1 Abstract 1
Table of Contents 2 Table of Contents 2
1. Introduction 3 1. Introduction 3
2. Goals 4 2. Goals 4
3. Goals of this document 5 3. Goals of this document 5
4. Presentation language 5 4. Presentation language 5
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4.4. Numbers 7 4.4. Numbers 7
4.5. Enumerateds 7 4.5. Enumerateds 7
4.6. Constructed types 8 4.6. Constructed types 8
4.6.1. Variants 8 4.6.1. Variants 8
4.7. Cryptographic attributes 9 4.7. Cryptographic attributes 9
4.8. Constants 10 4.8. Constants 10
5. HMAC and the pseudorandom function 11 5. HMAC and the pseudorandom function 11
6. The TLS Record Protocol 12 6. The TLS Record Protocol 12
6.1. Connection states 13 6.1. Connection states 13
6.2. Record layer 15 6.2. Record layer 15
6.2.1. Fragmentation 15 6.2.1. Fragmentation 16
6.2.2. Record compression and decompression 16 6.2.2. Record compression and decompression 16
6.2.3. Record payload protection 17 6.2.3. Record payload protection 17
6.2.3.1. Null or standard stream cipher 18 6.2.3.1. Null or standard stream cipher 18
6.2.3.2. CBC block cipher 18 6.2.3.2. CBC block cipher 18
6.3. Key calculation 19 6.3. Key calculation 19
6.3.1. Export key generation example 21 6.3.1. Export key generation example 21
7. The TLS Handshake Protocol 21 7. The TLS Handshake Protocol 21
7.1. Change cipher spec protocol 22 7.1. Change cipher spec protocol 22
7.2. Alert protocol 23 7.2. Alert protocol 23
7.2.1. Closure alerts 24 7.2.1. Closure alerts 24
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7.4.6. Client certificate 39 7.4.6. Client certificate 39
7.4.7. Client key exchange message 40 7.4.7. Client key exchange message 40
7.4.7.1. RSA encrypted premaster secret message 40 7.4.7.1. RSA encrypted premaster secret message 40
7.4.7.2. Client Diffie-Hellman public value 41 7.4.7.2. Client Diffie-Hellman public value 41
7.4.8. Certificate verify 42 7.4.8. Certificate verify 42
7.4.9. Finished 42 7.4.9. Finished 42
8. Cryptographic computations 43 8. Cryptographic computations 43
8.1. Computing the master secret 43 8.1. Computing the master secret 43
8.1.1. RSA 44 8.1.1. RSA 44
8.1.2. Diffie-Hellman 44 8.1.2. Diffie-Hellman 44
9. Application data protocol 44 9. Mandatory Cipher Suites 44
10. Application data protocol 44
A. Protocol constant values 44 A. Protocol constant values 44
A.1. Reserved port assignments 44 A.1. Record layer 44
A.2. Record layer 45 A.2. Change cipher specs message 45
A.3. Change cipher specs message 46 A.3. Alert messages 46
A.4. Alert messages 46 A.4. Handshake protocol 46
A.5. Handshake protocol 47 A.4.1. Hello messages 47
A.5.1. Hello messages 47 A.4.2. Server authentication and key exchange messages 47
A.5.2. Server authentication and key exchange messages 48 A.4.3. Client authentication and key exchange messages 49
A.5.3. Client authentication and key exchange messages 49 A.4.4. Handshake finalization message 49
A.5.4. Handshake finalization message 50 A.5. The CipherSuite 49
A.6. The CipherSuite 50 A.6. The Security Parameters 51
A.7. The Security Parameters 51
B. Glossary 52 B. Glossary 52
C. CipherSuite definitions 55 C. CipherSuite definitions 55
D. Implementation Notes 57 D. Implementation Notes 57
D.1. Temporary RSA keys 58 D.1. Temporary RSA keys 57
D.2. Random Number Generation and Seeding 58 D.2. Random Number Generation and Seeding 58
D.3. Certificates and authentication 59 D.3. Certificates and authentication 58
D.4. CipherSuites 59 D.4. CipherSuites 58
E. Backward Compatibility With SSL 59 E. Backward Compatibility With SSL 59
E.1. Version 2 client hello 60 E.1. Version 2 client hello 60
E.2. Avoiding man-in-the-middle version rollback 61 E.2. Avoiding man-in-the-middle version rollback 61
F. Security analysis 62 F. Security analysis 61
F.1. Handshake protocol 62 F.1. Handshake protocol 62
F.1.1. Authentication and key exchange 62 F.1.1. Authentication and key exchange 62
F.1.1.1. Anonymous key exchange 63 F.1.1.1. Anonymous key exchange 62
F.1.1.2. RSA key exchange and authentication 63 F.1.1.2. RSA key exchange and authentication 63
F.1.1.3. Diffie-Hellman key exchange with authentication 64 F.1.1.3. Diffie-Hellman key exchange with authentication 63
F.1.2. Version rollback attacks 64 F.1.2. Version rollback attacks 64
F.1.3. Detecting attacks against the handshake protocol 65 F.1.3. Detecting attacks against the handshake protocol 64
F.1.4. Resuming sessions 65 F.1.4. Resuming sessions 64
F.1.5. MD5 and SHA 65 F.1.5. MD5 and SHA 65
F.2. Protecting application data 65 F.2. Protecting application data 65
F.3. Final notes 66 F.3. Final notes 66
G. Patent Statement 66 G. Patent Statement 66
References 67 References 67
Credits 69 Credits 70
Comments 70 Comments 71
1. Introduction 1. Introduction
| The primary goal of the TLS Protocol is to provide privacy and data The primary goal of the TLS Protocol is to provide privacy and data
| integrity between two communicating applications. The protocol is integrity between two communicating applications. The protocol is
composed of two layers: the TLS Record Protocol and the TLS composed of two layers: the TLS Record Protocol and the TLS
Handshake Protocol. At the lowest level, layered on top of some Handshake Protocol. At the lowest level, layered on top of some
reliable transport protocol (e.g., TCP[TCP]), is the TLS Record reliable transport protocol (e.g., TCP[TCP]), is the TLS Record
Protocol. The TLS Record Protocol provides connection security that Protocol. The TLS Record Protocol provides connection security that
has two basic properties: has two basic properties:
- The connection is private. Symmetric cryptography is used for - The connection is private. Symmetric cryptography is used for
data encryption (e.g., DES[DES], RC4[RC4], etc.) The keys for data encryption (e.g., DES[DES], RC4[RC4], etc.) The keys for
this symmetric encryption are generated uniquely for each this symmetric encryption are generated uniquely for each
connection and are based on a secret negotiated by another connection and are based on a secret negotiated by another
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secret is unavailable to eavesdroppers, and for any secret is unavailable to eavesdroppers, and for any
authenticated connection the secret cannot be obtained, even by authenticated connection the secret cannot be obtained, even by
an attacker who can place himself in the middle of the an attacker who can place himself in the middle of the
connection. connection.
- The negotiation is reliable: no attacker can modify the - The negotiation is reliable: no attacker can modify the
negotiation communication without being detected by the parties negotiation communication without being detected by the parties
to the communication. to the communication.
One advantage of TLS is that it is application protocol independent. One advantage of TLS is that it is application protocol independent.
] Higher level protocols can layer on top of the TLS Protocol Higher level protocols can layer on top of the TLS Protocol
] transparently. The TLS standard, however, does not specify how transparently. The TLS standard, however, does not specify how
] protocols add security with TLS; the decisions on how to initiate protocols add security with TLS; the decisions on how to initiate
] TLS handshaking and how to interpret the authentication certificates TLS handshaking and how to interpret the authentication certificates
] exchanged are left up to the judgment of the designers and exchanged are left up to the judgment of the designers and
] implementors of protocols which run on top of TLS. implementors of protocols which run on top of TLS.
2. Goals 2. Goals
The goals of TLS Protocol, in order of their priority, are: The goals of TLS Protocol, in order of their priority, are:
1. Cryptographic security: TLS should be used to establish a secure 1. Cryptographic security: TLS should be used to establish a secure
connection between two parties. connection between two parties.
2. Interoperability: Independent programmers should be able to 2. Interoperability: Independent programmers should be able to
develop applications utilizing TLS that will then be able to develop applications utilizing TLS that will then be able to
successfully exchange cryptographic parameters without knowledge successfully exchange cryptographic parameters without knowledge
of one another's code. of one another's code.
Note: It is not the case that all instances of TLS (even in the same Note: It is not the case that all instances of TLS (even in the same
application domain) will be able to successfully connect. For application domain) will be able to successfully connect. For
instance, if the server supports a particular hardware token, instance, if the server supports a particular hardware token,
and the client does not have access to such a token, then the and the client does not have access to such a token, then the
] connection will not succeed. There is no required set of ciphers connection will not succeed. There is no required set of ciphers
] for minimal compliance, so some implementations may be unable to for minimal compliance, so some implementations may be unable to
] communicate. communicate.
3. Extensibility: TLS seeks to provide a framework into which new 3. Extensibility: TLS seeks to provide a framework into which new
public key and bulk encryption methods can be incorporated as public key and bulk encryption methods can be incorporated as
necessary. This will also accomplish two sub-goals: to prevent necessary. This will also accomplish two sub-goals: to prevent
the need to create a new protocol (and risking the introduction the need to create a new protocol (and risking the introduction
of possible new weaknesses) and to avoid the need to implement of possible new weaknesses) and to avoid the need to implement
an entire new security library. an entire new security library.
4. Relative efficiency: Cryptographic operations tend to be highly 4. Relative efficiency: Cryptographic operations tend to be highly
CPU intensive, particularly public key operations. For this CPU intensive, particularly public key operations. For this
reason, the TLS protocol has incorporated an optional session reason, the TLS protocol has incorporated an optional session
caching scheme to reduce the number of connections that need to caching scheme to reduce the number of connections that need to
be established from scratch. Additionally, care has been taken be established from scratch. Additionally, care has been taken
to reduce network activity. to reduce network activity.
3. Goals of this document 3. Goals of this document
] This document and the TLS protocol itself are based on the SSL 3.0 This document and the TLS protocol itself are based on the SSL 3.0
] Protocol Specification as published by Netscape. The differences Protocol Specification as published by Netscape. The differences
] between this protocol and SSL 3.0 are not dramatic, but they are between this protocol and SSL 3.0 are not dramatic, but they are
] significant enough that TLS 1.0 and SSL 3.0 do not interoperate significant enough that TLS 1.0 and SSL 3.0 do not interoperate
] (although TLS 1.0 does incorporate a mechanism by which a TLS (although TLS 1.0 does incorporate a mechanism by which a TLS
] implementation can back down to SSL 3.0). This document is intended implementation can back down to SSL 3.0). This document is intended
] primarily for readers who will be implementing the protocol and primarily for readers who will be implementing the protocol and
] those doing cryptographic analysis of it. The specification has been those doing cryptographic analysis of it. The specification has been
] written with this in mind, and it is intended to reflect the needs written with this in mind, and it is intended to reflect the needs
] of those two groups. For that reason, many of the of those two groups. For that reason, many of the
] algorithm-dependent data structures and rules are included in the algorithm-dependent data structures and rules are included in the
] body of the text (as opposed to in an appendix), providing easier body of the text (as opposed to in an appendix), providing easier
] access to them. access to them.
This document is not intended to supply any details of service This document is not intended to supply any details of service
definition nor interface definition, although it does cover select definition nor interface definition, although it does cover select
areas of policy as they are required for the maintenance of solid areas of policy as they are required for the maintenance of solid
security. security.
4. Presentation language 4. Presentation language
This document deals with the formatting of data in an external This document deals with the formatting of data in an external
representation. The following very basic and somewhat casually representation. The following very basic and somewhat casually
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length field of zero is referred to as an empty vector. length field of zero is referred to as an empty vector.
T T'<floor..ceiling>; T T'<floor..ceiling>;
In the following example, mandatory is a vector that must contain In the following example, mandatory is a vector that must contain
between 300 and 400 bytes of type opaque. It can never be empty. The between 300 and 400 bytes of type opaque. It can never be empty. The
actual length field consumes two bytes, a uint16, sufficient to actual length field consumes two bytes, a uint16, sufficient to
represent the value 400 (see Section 4.4). On the other hand, longer represent the value 400 (see Section 4.4). On the other hand, longer
can represent up to 800 bytes of data, or 400 uint16 elements, and can represent up to 800 bytes of data, or 400 uint16 elements, and
it may be empty. Its encoding will include a two byte actual length it may be empty. Its encoding will include a two byte actual length
| field prepended to the vector. The length of an encoded vector must field prepended to the vector. The length of an encoded vector must
| be an even multiple of the length of a single element (for example, be an even multiple of the length of a single element (for example,
| a 17 byte vector of uint16 would be illegal). a 17 byte vector of uint16 would be illegal).
opaque mandatory<300..400>; opaque mandatory<300..400>;
/* length field is 2 bytes, cannot be empty */ /* length field is 2 bytes, cannot be empty */
uint16 longer<0..800>; uint16 longer<0..800>;
/* zero to 400 16-bit unsigned integers */ /* zero to 400 16-bit unsigned integers */
4.4. Numbers 4.4. Numbers
The basic numeric data type is an unsigned byte (uint8). All larger The basic numeric data type is an unsigned byte (uint8). All larger
numeric data types are formed from fixed length series of bytes numeric data types are formed from fixed length series of bytes
concatenated as described in Section 4.1 and are also unsigned. The concatenated as described in Section 4.1 and are also unsigned. The
following numeric types are predefined. following numeric types are predefined.
uint8 uint16[2]; uint8 uint16[2];
uint8 uint24[3]; uint8 uint24[3];
uint8 uint32[4]; uint8 uint32[4];
uint8 uint64[8]; uint8 uint64[8];
] All values, here and elsewhere in the specification, are stored in All values, here and elsewhere in the specification, are stored in
] "network" or "big-endian" order; the uint32 represented by the hex "network" or "big-endian" order; the uint32 represented by the hex
] bytes 01 02 03 04 is equivalent to the decimal value 16909060. bytes 01 02 03 04 is equivalent to the decimal value 16909060.
4.5. Enumerateds 4.5. Enumerateds
An additional sparse data type is available called enum. A field of An additional sparse data type is available called enum. A field of
type enum can only assume the values declared in the definition. type enum can only assume the values declared in the definition.
Each definition is a different type. Only enumerateds of the same Each definition is a different type. Only enumerateds of the same
type may be assigned or compared. Every element of an enumerated type may be assigned or compared. Every element of an enumerated
must be assigned a value, as demonstrated in the following example. must be assigned a value, as demonstrated in the following example.
Since the elements of the enumerated are not ordered, they can be Since the elements of the enumerated are not ordered, they can be
assigned any unique value, in any order. assigned any unique value, in any order.
enum { e1(v1), e2(v2), ... , en(vn), [[(n)]] } Te; enum { e1(v1), e2(v2), ... , en(vn) [[, (n)]] } Te;
Enumerateds occupy as much space in the byte stream as would its Enumerateds occupy as much space in the byte stream as would its
maximal defined ordinal value. The following definition would cause maximal defined ordinal value. The following definition would cause
one byte to be used to carry fields of type Color. one byte to be used to carry fields of type Color.
enum { red(3), blue(5), white(7) } Color; enum { red(3), blue(5), white(7) } Color;
One may optionally specify a value without its associated tag to One may optionally specify a value without its associated tag to
force the width definition without defining a superfluous element. force the width definition without defining a superfluous element.
In the following example, Taste will consume two bytes in the data In the following example, Taste will consume two bytes in the data
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struct { struct {
uint8 f1; uint8 f1;
uint8 f2; uint8 f2;
} Example1; } Example1;
Example1 ex1 = {1, 4}; /* assigns f1 = 1, f2 = 4 */ Example1 ex1 = {1, 4}; /* assigns f1 = 1, f2 = 4 */
5. HMAC and the pseudorandom function 5. HMAC and the pseudorandom function
] A number of operations in the TLS record and handshake layer A number of operations in the TLS record and handshake layer
] required a keyed MAC; this is a secure digest of some data protected required a keyed MAC; this is a secure digest of some data protected
] by a secret. Forging the MAC is infeasible without knowledge of the by a secret. Forging the MAC is infeasible without knowledge of the
] MAC secret. Finding two data messages which have the same MAC is MAC secret. Finding two data messages which have the same MAC is
] also cryptographically infeasible. The construction we use for this also cryptographically infeasible. The construction we use for this
] operation is known as HMAC, described in [HMAC]. operation is known as HMAC, described in [HMAC].
] HMAC can be used with a variety of different hash algorithms. TLS HMAC can be used with a variety of different hash algorithms. TLS
] uses it in the handshake with two different algorithms: MD5 and uses it in the handshake with two different algorithms: MD5 and
] SHA-1, denoting these as HMAC_MD5(secret, data) and HMAC_SHA(secret, SHA-1, denoting these as HMAC_MD5(secret, data) and HMAC_SHA(secret,
] data). Additional hash algorithms can be defined by cipher suites data). Additional hash algorithms can be defined by cipher suites
] and used to protect record data, but MD5 and SHA-1 are hard coded and used to protect record data, but MD5 and SHA-1 are hard coded
] into the description of the handshaking for this version of the into the description of the handshaking for this version of the
] protocol. protocol.
] In addition, a construction is required to do expansion of secrets In addition, a construction is required to do expansion of secrets
] into blocks of data for the purposes of key generation or into blocks of data for the purposes of key generation or
] validation. This pseudo-random function (PRF) takes as input a validation. This pseudo-random function (PRF) takes as input a
| secret, a seed, and an identifying label and produces an output of secret, a seed, and an identifying label and produces an output of
| arbitrary length. arbitrary length.
] In order to make the PRF as secure as possible, it uses two hash In order to make the PRF as secure as possible, it uses two hash
] algorithms in a way which should guarantee its security if either algorithms in a way which should guarantee its security if either
] algorithm remains secure. algorithm remains secure.
] First, we define a data expansion function, P_hash(secret, data) First, we define a data expansion function, P_hash(secret, data)
] which uses a single hash function to expand a secret and seed into which uses a single hash function to expand a secret and seed into
] an arbitrary quantity of output: an arbitrary quantity of output:
] P_hash(secret, seed) = HMAC_hash(secret, A(1) + seed) + P_hash(secret, seed) = HMAC_hash(secret, A(1) + seed) +
] HMAC_hash(secret, A(2) + seed) + HMAC_hash(secret, A(2) + seed) +
] HMAC_hash(secret, A(3) + seed) + ... HMAC_hash(secret, A(3) + seed) + ...
] Where + indicates concatenation. Where + indicates concatenation.
] A() is defined as: A() is defined as:
] A(0) = seed A(0) = seed
] A(i) = HMAC_hash(secret, A(i-1)) A(i) = HMAC_hash(secret, A(i-1))
P_hash can be iterated as many times as is necessary to produce the
required quantity of data. For example, if P_SHA-1 was being used to
create 64 bytes of data, it would have to be iterated 4 times
(through A(4)), creating 80 bytes of output data; the last 16 bytes
of the final iteration would then be discarded, leaving 64 bytes of
output data.
] P_hash can be iterated as many times as is necessary to produce the TLS's PRF is created by splitting the secret into two halves and
] required quantity of data. For example, if P_SHA-1 was being used to using one half to generate data with P_MD5 and the other half to
] create 64 bytes of data, it would have to be iterated 4 times generate data with P_SHA-1, then exclusive-or'ing the outputs of
] (through A(4)), creating 80 bytes of output data; the last 16 bytes these two expansion functions together.
] of the final iteration would then be discarded, leaving 64 bytes of
] output data.
] TLS's PRF is created by splitting the secret into two halves and S1 and S2 are the two halves of the secret and each is the same
] using one half to generate data with P_MD5 and the other half to length. S1 is taken from the first half of the secret, S2 from the
] generate data with P_SHA1, then exclusive-or'ing the outputs of second half. Their length is created by rounding up the length of
] these two expansion functions together. the overall secret divided by two; thus, if the original secret is
an odd number of bytes long, the last byte of S1 will be the same as
the first byte of S2.
] S1 and S2 are the two halves of the secret and each is the same L_S = length in bytes of secret;
] length. S1 is taken from the first half of the secret, S2 from the L_S1 = L_S2 = ceil(L_S / 2);
] second half. Their length is created by rounding up the length of
] the overall secret divided by two; thus, if the original secret is
] an odd number of bytes long, the last byte of S1 will be the same as
] the first byte of S2.
] L_S = length in bytes of secret; The secret is partitioned into two halves (with the possibility of
] L_S1 = L_S2 = ceil(L_S / 2); one shared byte) as described above, S1 taking the first L_S1 bytes
and S2 the last L_S2 bytes.
] The secret is partitioned into two halves (with the possibility of The PRF is then defined as the result of mixing the two pseudorandom
] one shared byte) as described above, S1 taking the first L_S1 bytes streams by exclusive-or'ing them together.
] and S2 the last L_S2 bytes.
] The PRF is then defined as the result of mixing the two pseudorandom PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
] streams by exclusive-or'ing them together. P_SHA-1(S2, label + seed);
| PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR The label is an ASCII string. It should be included in the exact
| P_SHA-1(S2, label + seed); form it is given without a length byte or trailing null character.
For example, the label "slithy toves" would be processed by hashing
the following bytes:
] Note that because MD5 produces 16 byte outputs and SHA-1 produces 20 73 6C 69 74 68 79 20 74 6F 76 65 73
] byte outputs, the boundaries of their internal iterations will not
] be aligned; to generate a 80 byte output will involve P_MD5 being Note that because MD5 produces 16 byte outputs and SHA-1 produces 20
] iterated through A(5), while P_SHA-1 will only iterate through A(4). byte outputs, the boundaries of their internal iterations will not
be aligned; to generate a 80 byte output will involve P_MD5 being
iterated through A(5), while P_SHA-1 will only iterate through A(4).
6. The TLS Record Protocol 6. The TLS Record Protocol
The TLS Record Protocol is a layered protocol. At each layer, The TLS Record Protocol is a layered protocol. At each layer,
messages may include fields for length, description, and content. messages may include fields for length, description, and content.
The Record Protocol takes messages to be transmitted, fragments the The Record Protocol takes messages to be transmitted, fragments the
data into manageable blocks, optionally compresses the data, applies data into manageable blocks, optionally compresses the data, applies
a MAC, encrypts, and transmits the result. Received data is a MAC, encrypts, and transmits the result. Received data is
decrypted, verified, decompressed, and reassembled, then delivered decrypted, verified, decompressed, and reassembled, then delivered
to higher level clients. to higher level clients.
] Four record protocol clients are described in this document: the Four record protocol clients are described in this document: the
] handshake protocol, the alert protocol, the change cipher spec handshake protocol, the alert protocol, the change cipher spec
] protocol, and the application data protocol. In order to allow protocol, and the application data protocol. In order to allow
] extension of the TLS protocol, additional record types can be extension of the TLS protocol, additional record types can be
] supported by the record protocol. Any new record types should supported by the record protocol. Any new record types should
allocate type values immediately beyond the ContentType values for
] allocate type values immediately beyond the ContentType values for the four record types described here (see Appendix A.2). If a TLS
] the four record types described here (see Appendix A.2). If a TLS implementation receives a record type it does not understand, it
] implementation receives a record type it does not understand, it should just ignore it. Any protocol designed for use over TLS must
] should just ignore it. Any protocol designed for use over TLS must be carefully designed to deal with all possible attacks against it.
] be carefully designed to deal with all possible attacks against it. Note that because the type and length of a record are not protected
| Note that because the type and length of a record are not protected by encryption, care should be take to minimize the value of traffic
| by encryption, care should be take to minimize the value of traffic analysis of these values.
| analysis of these values.
6.1. Connection states 6.1. Connection states
A TLS connection state is the operating environment of the TLS A TLS connection state is the operating environment of the TLS
Record Protocol. It specifies a compression algorithm, encryption Record Protocol. It specifies a compression algorithm, encryption
algorithm, and MAC algorithm. In addition, the parameters for these algorithm, and MAC algorithm. In addition, the parameters for these
algorithms are known: the MAC secret and the bulk encryption keys algorithms are known: the MAC secret and the bulk encryption keys
and IVs for the connection in both the read and the write and IVs for the connection in both the read and the write
directions. Logically, there are always four connection states directions. Logically, there are always four connection states
outstanding: the current read and write states, and the pending read outstanding: the current read and write states, and the pending read
and write states. All records are processed under the current read and write states. All records are processed under the current read
and write states. The security parameters for the pending states can and write states. The security parameters for the pending states can
be set by the TLS Handshake Protocol, and the Handshake Protocol can be set by the TLS Handshake Protocol, and the Handshake Protocol can
selectively make either of the pending states current, in which case selectively make either of the pending states current, in which case
the appropriate current state is disposed of and replaced with the the appropriate current state is disposed of and replaced with the
pending state; the pending state is then reinitialized to an empty pending state; the pending state is then reinitialized to an empty
state. It is illegal to make a state which has not been initialized state. It is illegal to make a state which has not been initialized
| with security parameters a current state. The initial current state with security parameters a current state. The initial current state
| always specifies that no encryption, compression, or MAC will be always specifies that no encryption, compression, or MAC will be
| used. used.
The security parameters for a TLS Connection read and write state The security parameters for a TLS Connection read and write state
are set by providing the following values: are set by providing the following values:
connection end connection end
Whether this entity is considered the "client" or the "server" Whether this entity is considered the "client" or the "server"
in this connection. in this connection.
bulk encryption algorithm bulk encryption algorithm
An algorithm to be used for bulk encryption. This specification An algorithm to be used for bulk encryption. This specification
skipping to change at page 15, line 21 skipping to change at page 15, line 31
the current states. These current states must be updated for each the current states. These current states must be updated for each
record processed. Each connection state includes the following record processed. Each connection state includes the following
elements: elements:
compression state compression state
The current state of the compression algorithm. The current state of the compression algorithm.
cipher state cipher state
The current state of the encryption algorithm. This will consist The current state of the encryption algorithm. This will consist
of the scheduled key for that connection. In addition, for block of the scheduled key for that connection. In addition, for block
| ciphers running in CBC mode (the only mode specified for TLS), ciphers running in CBC mode (the only mode specified for TLS),
| this will initially contain the IV for that connection state and this will initially contain the IV for that connection state and
| be updated to contain the ciphertext of the last block encrypted be updated to contain the ciphertext of the last block encrypted
| or decrypted as records are processed. For stream ciphers, this or decrypted as records are processed. For stream ciphers, this
| will contain whatever the necessary state information is to will contain whatever the necessary state information is to
| allow the stream to continue to encrypt or decrypt data. allow the stream to continue to encrypt or decrypt data.
MAC secret MAC secret
The MAC secret for this connection as generated above. The MAC secret for this connection as generated above.
sequence number sequence number
Each connection state contains a sequence number, which is Each connection state contains a sequence number, which is
maintained separately for read and write states. The sequence maintained separately for read and write states. The sequence
number must be set to zero whenever a connection state is made number must be set to zero whenever a connection state is made
the active state. Sequence numbers are of type uint64 and may the active state. Sequence numbers are of type uint64 and may
not exceed 2^64-1. A sequence number is incremented after each not exceed 2^64-1. A sequence number is incremented after each
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ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
opaque fragment[TLSPlaintext.length]; opaque fragment[TLSPlaintext.length];
} TLSPlaintext; } TLSPlaintext;
type type
The higher level protocol used to process the enclosed fragment. The higher level protocol used to process the enclosed fragment.
version version
The version of the protocol being employed. This document The version of the protocol being employed. This document
] describes TLS Version 1.0, which uses the version { 3, 1 }. The describes TLS Version 1.0, which uses the version { 3, 1 }. The
] version value 3.1 is historical: TLS version 1.0 is a minor version value 3.1 is historical: TLS version 1.0 is a minor
] modification to the SSL 3.0 protocol, which bears the version modification to the SSL 3.0 protocol, which bears the version
] value 3.0. (See Appendix A.1.1). value 3.0. (See Appendix A.1).
length length
The length (in bytes) of the following TLSPlaintext.fragment. The length (in bytes) of the following TLSPlaintext.fragment.
The length should not exceed 2^14. The length should not exceed 2^14.
fragment fragment
The application data. This data is transparent and treated as an The application data. This data is transparent and treated as an
independent block to be dealt with by the higher level protocol independent block to be dealt with by the higher level protocol
specified by the type field. specified by the type field.
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fields are altered. fields are altered.
Implementation note: Implementation note:
Decompression functions are responsible for ensuring that Decompression functions are responsible for ensuring that
messages cannot cause internal buffer overflows. messages cannot cause internal buffer overflows.
6.2.3. Record payload protection 6.2.3. Record payload protection
The encryption and MAC functions translate a TLSCompressed structure The encryption and MAC functions translate a TLSCompressed structure
into a TLSCiphertext. The decryption functions reverse the process. into a TLSCiphertext. The decryption functions reverse the process.
| Transmissions also include a sequence number so that missing, extra The MAC of the record also includes a sequence number so that
| or repeated messages are detectable. missing, extra or repeated messages are detectable.
struct { struct {
ContentType type; ContentType type;
ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
select (CipherSpec.cipher_type) { select (CipherSpec.cipher_type) {
case stream: GenericStreamCipher; case stream: GenericStreamCipher;
case block: GenericBlockCipher; case block: GenericBlockCipher;
} fragment; } fragment;
} TLSCiphertext; } TLSCiphertext;
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length length
The length (in bytes) of the following TLSCiphertext.fragment. The length (in bytes) of the following TLSCiphertext.fragment.
The length may not exceed 2^14 + 2048. The length may not exceed 2^14 + 2048.
fragment fragment
The encrypted form of TLSCompressed.fragment, with the MAC. The encrypted form of TLSCompressed.fragment, with the MAC.
6.2.3.1. Null or standard stream cipher 6.2.3.1. Null or standard stream cipher
Stream ciphers (including BulkCipherAlgorithm.null - see Appendix Stream ciphers (including BulkCipherAlgorithm.null - see Appendix
A.7) convert TLSCompressed.fragment structures to and from stream A.6) convert TLSCompressed.fragment structures to and from stream
TLSCiphertext.fragment structures. TLSCiphertext.fragment structures.
stream-ciphered struct { stream-ciphered struct {
opaque content[TLSCompressed.length]; opaque content[TLSCompressed.length];
opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
} GenericStreamCipher; } GenericStreamCipher;
The MAC is generated as: The MAC is generated as:
| HMAC_hash(MAC_write_secret, seq_num + TLSCompressed.type + HMAC_hash(MAC_write_secret, seq_num + TLSCompressed.type +
| TLSCompressed.version + TLSCompressed.length + TLSCompressed.version + TLSCompressed.length +
TLSCompressed.fragment)); TLSCompressed.fragment));
where "+" denotes concatenation. where "+" denotes concatenation.
seq_num seq_num
The sequence number for this record. The sequence number for this record.
hash hash
The hashing algorithm specified by The hashing algorithm specified by
SecurityParameters.mac_algorithm. SecurityParameters.mac_algorithm.
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For block ciphers (such as RC2 or DES), the encryption and MAC For block ciphers (such as RC2 or DES), the encryption and MAC
functions convert TLSCompressed.fragment structures to and from functions convert TLSCompressed.fragment structures to and from
block TLSCiphertext.fragment structures. block TLSCiphertext.fragment structures.
block-ciphered struct { block-ciphered struct {
opaque content[TLSCompressed.length]; opaque content[TLSCompressed.length];
opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
uint8 padding[GenericBlockCipher.padding_length]; uint8 padding[GenericBlockCipher.padding_length];
uint8 padding_length; uint8 padding_length;
} GenericBlockCipher; } GenericBlockCipher;
The MAC is generated as described in Section 6.2.3.1. The MAC is generated as described in Section 6.2.3.1.
padding padding
Padding that is added to force the length of the plaintext to be Padding that is added to force the length of the plaintext to be
] an even multiple of the block cipher's block length. The padding an even multiple of the block cipher's block length. The padding
] may be any length up to 255 bytes long, as long as it results in may be any length up to 255 bytes long, as long as it results in
] the TLSCiphertext.length being an even multiple of the block the TLSCiphertext.length being an even multiple of the block
] length. Lengths longer than necessary might be desirable to length. Lengths longer than necessary might be desirable to
] frustrate attacks on a protocol based on analysis of the lengths frustrate attacks on a protocol based on analysis of the lengths
| of exchanged messages. Each uint8 in the padding data vector of exchanged messages. Each uint8 in the padding data vector
| must be filled with the padding length value. must be filled with the padding length value.
padding_length padding_length
| The padding length should be such that the total size of the The padding length should be such that the total size of the
| GenericBlockCipher structure is a multiple of the cipher's block GenericBlockCipher structure is a multiple of the cipher's block
| length. Legal values range from zero to 255, inclusive. length. Legal values range from zero to 255, inclusive.
The encrypted data length (TLSCiphertext.length) is one more than The encrypted data length (TLSCiphertext.length) is one more than
the sum of TLSCompressed.length, CipherSpec.hash_size, and the sum of TLSCompressed.length, CipherSpec.hash_size, and
padding_length. padding_length.
Example: If the block length is 8 bytes, the content length Example: If the block length is 8 bytes, the content length
] (TLSCompressed.length) is 61 bytes, and the MAC length is 20 (TLSCompressed.length) is 61 bytes, and the MAC length is 20
] bytes, the length before padding is 82 bytes. Thus, the bytes, the length before padding is 82 bytes. Thus, the
] padding length modulo 8 must be equal to 6 in order to make padding length modulo 8 must be equal to 6 in order to make
] the total length an even multiple of 8 bytes (the block the total length an even multiple of 8 bytes (the block
] length). The padding length can be 6, 14, 22, and so on, length). The padding length can be 6, 14, 22, and so on,
] through 254. If the padding length were the minimum necessary, through 254. If the padding length were the minimum necessary,
] 6, the padding would be 6 bytes, each containing the value 6. 6, the padding would be 6 bytes, each containing the value 6.
Note: With block ciphers in CBC mode (Cipher Block Chaining) the Note: With block ciphers in CBC mode (Cipher Block Chaining) the
initialization vector (IV) for the first record is generated initialization vector (IV) for the first record is generated
with the other keys and secrets when the security parameters are with the other keys and secrets when the security parameters are
set. The IV for subsequent records is the last ciphertext block set. The IV for subsequent records is the last ciphertext block
from the previous record. from the previous record.
6.3. Key calculation 6.3. Key calculation
The Record Protocol requires an algorithm to generate keys, IVs, and The Record Protocol requires an algorithm to generate keys, IVs, and
MAC secrets from the security parameters provided by the handshake MAC secrets from the security parameters provided by the handshake
protocol. protocol.
The master secret is hashed into a sequence of secure bytes, which The master secret is hashed into a sequence of secure bytes, which
are assigned to the MAC secrets, keys, and non-export IVs required are assigned to the MAC secrets, keys, and non-export IVs required
by the current connection state (see Appendix A.7). CipherSpecs by the current connection state (see Appendix A.6). CipherSpecs
require a client write MAC secret, a server write MAC secret, a require a client write MAC secret, a server write MAC secret, a
client write key, a server write key, a client write IV, and a client write key, a server write key, a client write IV, and a
server write IV, which are generated from the master secret in that server write IV, which are generated from the master secret in that
order. Unused values are empty. order. Unused values are empty.
When generating keys and MAC secrets, the master secret is used as When generating keys and MAC secrets, the master secret is used as
an entropy source, and the random values provide unencrypted salt an entropy source, and the random values provide unencrypted salt
material and IVs for exportable ciphers. material and IVs for exportable ciphers.
To generate the key material, compute To generate the key material, compute
] key_block = PRF(SecurityParameters.master_secret, key_block = PRF(SecurityParameters.master_secret,
| "key expansion", "key expansion",
] SecurityParameters.server_random + SecurityParameters.server_random +
] SecurityParameters.client_random); SecurityParameters.client_random);
until enough output has been generated. Then the key_block is until enough output has been generated. Then the key_block is
partitioned as follows: partitioned as follows:
client_write_MAC_secret[SecurityParameters.hash_size] client_write_MAC_secret[SecurityParameters.hash_size]
server_write_MAC_secret[SecurityParameters.hash_size] server_write_MAC_secret[SecurityParameters.hash_size]
client_write_key[SecurityParameters.key_material] client_write_key[SecurityParameters.key_material]
server_write_key[SecurityParameters.key_material] server_write_key[SecurityParameters.key_material]
client_write_IV[SecurityParameters.IV_size] client_write_IV[SecurityParameters.IV_size]
server_write_IV[SecurityParameters.IV_size] server_write_IV[SecurityParameters.IV_size]
The client_write_IV and server_write_IV are only generated for The client_write_IV and server_write_IV are only generated for
non-export block ciphers. For exportable block ciphers, the non-export block ciphers. For exportable block ciphers, the
initialization vectors are generated later, as described below. Any initialization vectors are generated later, as described below. Any
extra key_block material is discarded. extra key_block material is discarded.
Implementation note: Implementation note:
The cipher spec which is defined in this document which requires The cipher spec which is defined in this document which requires
the most material is 3DES_EDE_CBC_SHA: it requires 2 x 24 byte the most material is 3DES_EDE_CBC_SHA: it requires 2 x 24 byte
keys, 2 x 20 byte MAC secrets, and 2 x 8 byte IVs, for a total keys, 2 x 20 byte MAC secrets, and 2 x 8 byte IVs, for a total
| of 104 bytes of key material. of 104 bytes of key material.
Exportable encryption algorithms (for which CipherSpec.is_exportable Exportable encryption algorithms (for which CipherSpec.is_exportable
is true) require additional processing as follows to derive their is true) require additional processing as follows to derive their
final write keys: final write keys:
] final_client_write_key = final_client_write_key =
] PRF(SecurityParameters.client_write_key, PRF(SecurityParameters.client_write_key,
| "client write key", "client write key",
] SecurityParameters.client_random + SecurityParameters.client_random +
] SecurityParameters.server_random); SecurityParameters.server_random);
] final_server_write_key = final_server_write_key =
] PRF(SecurityParameters.server_write_key, PRF(SecurityParameters.server_write_key,
| "server write key", "server write key",
] SecurityParameters.client_random + SecurityParameters.client_random +
] SecurityParameters.server_random); SecurityParameters.server_random);
Exportable encryption algorithms derive their IVs solely from the
] Exportable encryption algorithms derive their IVs solely from the random values from the hello messages:
] random values from the hello messages:
| iv_block = PRF("", "IV block", SecurityParameters.client_random iv_block = PRF("", "IV block", SecurityParameters.client_random
] + SecurityParameters.server_random); +
SecurityParameters.server_random);
] The iv_block is partitioned into two initialization vectors as the The iv_block is partitioned into two initialization vectors as the
] key_block was above: key_block was above:
] client_write_IV[SecurityParameters.IV_size] client_write_IV[SecurityParameters.IV_size]
] server_write_IV[SecurityParameters.IV_size] server_write_IV[SecurityParameters.IV_size]
] Note that the PRF is used without a secret in this case: this just Note that the PRF is used without a secret in this case: this just
] means that the secret has a length of zero bytes and contributes means that the secret has a length of zero bytes and contributes
] nothing to the hashing in the PRF. nothing to the hashing in the PRF.
6.3.1. Export key generation example 6.3.1. Export key generation example
TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5 requires five random bytes for TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5 requires five random bytes for
each of the two encryption keys and 16 bytes for each of the MAC each of the two encryption keys and 16 bytes for each of the MAC
| keys, for a total of 42 bytes of key material. The PRF output is keys, for a total of 42 bytes of key material. The PRF output is
| stored in the key_block. The key_block is partitioned, and the write stored in the key_block. The key_block is partitioned, and the write
| keys are salted because this is an exportable encryption algorithm. keys are salted because this is an exportable encryption algorithm.
] key_block = PRF(master_secret, key_block = PRF(master_secret,
| "key expansion", "key expansion",
] master_secret + master_secret +
] server_random + server_random +
] client_random)[0..41] client_random)[0..41]
client_write_MAC_secret = key_block[0..15] client_write_MAC_secret = key_block[0..15]
server_write_MAC_secret = key_block[16..31] server_write_MAC_secret = key_block[16..31]
client_write_key = key_block[32..36] client_write_key = key_block[32..36]
server_write_key = key_block[37..41] server_write_key = key_block[37..41]
] final_client_write_key = PRF(client_write_key, final_client_write_key = PRF(client_write_key,
| "client write key", "client write key",
] client_random + client_random +
] server_random)[0..15] server_random)[0..15]
] final_server_write_key = PRF(server_write_key, final_server_write_key = PRF(server_write_key,
| "server write key", "server write key",
] client_random + client_random +
] server_random)[0..15] server_random)[0..15]
| iv_block = PRF("", "IV block", client_random + iv_block = PRF("", "IV block", client_random +
] server_random)[0..15] server_random)[0..15]
] client_write_IV = iv_block[0..7] client_write_IV = iv_block[0..7]
] server_write_IV = iv_block[8..15] server_write_IV = iv_block[8..15]
7. The TLS Handshake Protocol 7. The TLS Handshake Protocol
The TLS Handshake Protocol consists of a suite of three The TLS Handshake Protocol consists of a suite of three
sub-protocols which are used to allow peers to agree upon security sub-protocols which are used to allow peers to agree upon security
parameters for the record layer, authenticate themselves, parameters for the record layer, authenticate themselves,
instantiate negotiated security parameters, and report error instantiate negotiated security parameters, and report error
conditions to each other. conditions to each other.
The Handshake Protocol is responsible for negotiating a session, The Handshake Protocol is responsible for negotiating a session,
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X509v3[X509] certificate of the peer. This element of the state X509v3[X509] certificate of the peer. This element of the state
may be null. may be null.
compression method compression method
The algorithm used to compress data prior to encryption. The algorithm used to compress data prior to encryption.
cipher spec cipher spec
Specifies the bulk data encryption algorithm (such as null, DES, Specifies the bulk data encryption algorithm (such as null, DES,
etc.) and a MAC algorithm (such as MD5 or SHA). It also defines etc.) and a MAC algorithm (such as MD5 or SHA). It also defines
cryptographic attributes such as the hash_size. (See Appendix cryptographic attributes such as the hash_size. (See Appendix
A.7 for formal definition) A.6 for formal definition)
master secret master secret
48-byte secret shared between the client and server. 48-byte secret shared between the client and server.
is resumable is resumable
A flag indicating whether the session can be used to initiate A flag indicating whether the session can be used to initiate
new connections. new connections.
These items are then used to create security parameters for use by These items are then used to create security parameters for use by
the Record Layer when protecting application data. Many connections the Record Layer when protecting application data. Many connections
skipping to change at page 23, line 26 skipping to change at page 23, line 30
session from being used to establish new connections. Like other session from being used to establish new connections. Like other
messages, alert messages are encrypted and compressed, as specified messages, alert messages are encrypted and compressed, as specified
by the current connection state. by the current connection state.
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
enum { enum {
close_notify(0), close_notify(0),
unexpected_message(10), unexpected_message(10),
bad_record_mac(20), bad_record_mac(20),
] decryption_failed(21), decryption_failed(21),
] record_overflow(22), record_overflow(22),
decompression_failure(30), decompression_failure(30),
handshake_failure(40), handshake_failure(40),
bad_certificate(42), bad_certificate(42),
unsupported_certificate(43), unsupported_certificate(43),
certificate_revoked(44), certificate_revoked(44),
certificate_expired(45), certificate_expired(45),
certificate_unknown(46), certificate_unknown(46),
illegal_parameter(47), illegal_parameter(47),
] unknown_ca(48), unknown_ca(48),
] access_denied(49), access_denied(49),
] decode_error(50), decode_error(50),
] decrypt_error(51), decrypt_error(51),
] export_restriction(60), export_restriction(60),
] protocol_version(70), protocol_version(70),
] insufficient_security(71), insufficient_security(71),
] internal_error(80), internal_error(80),
] user_canceled(90), user_canceled(90),
] no_renegotiation(100), no_renegotiation(100),
(255) (255)
} AlertDescription; } AlertDescription;
struct { struct {
AlertLevel level; AlertLevel level;
AlertDescription description; AlertDescription description;
} Alert; } Alert;
7.2.1. Closure alerts 7.2.1. Closure alerts
skipping to change at page 24, line 49 skipping to change at page 24, line 49
unexpected_message unexpected_message
An inappropriate message was received. This alert is always An inappropriate message was received. This alert is always
fatal and should never be observed in communication between fatal and should never be observed in communication between
proper implementations. proper implementations.
bad_record_mac bad_record_mac
This alert is returned if a record is received with an incorrect This alert is returned if a record is received with an incorrect
MAC. This message is always fatal. MAC. This message is always fatal.
] decryption_failed decryption_failed
] A TLSCiphertext decrypted in an invalid way: either it wasn`t an A TLSCiphertext decrypted in an invalid way: either it wasn`t an
] even multiple of the block length or its padding values, when even multiple of the block length or its padding values, when
] checked, weren`t correct. This message is always fatal. checked, weren`t correct. This message is always fatal.
] record_overflow
] A TLSCiphertext record was received which had a length more than
] 2^14+2048 bytes, or a record decrypted to a TLSCompressed record
] with more than 2^14+1024 bytes. This message is always fatal. record_overflow
A TLSCiphertext record was received which had a length more than
2^14+2048 bytes, or a record decrypted to a TLSCompressed record
with more than 2^14+1024 bytes. This message is always fatal.
decompression_failure decompression_failure
The decompression function received improper input (e.g. data The decompression function received improper input (e.g. data
that would expand to excessive length). This message is always that would expand to excessive length). This message is always
fatal. fatal.
handshake_failure handshake_failure
Reception of a handshake_failure alert message indicates that Reception of a handshake_failure alert message indicates that
the sender was unable to negotiate an acceptable set of security the sender was unable to negotiate an acceptable set of security
parameters given the options available. This is a fatal error. parameters given the options available. This is a fatal error.
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A certificate has expired or is not currently valid. A certificate has expired or is not currently valid.
certificate_unknown certificate_unknown
Some other (unspecified) issue arose in processing the Some other (unspecified) issue arose in processing the
certificate, rendering it unacceptable. certificate, rendering it unacceptable.
illegal_parameter illegal_parameter
A field in the handshake was out of range or inconsistent with A field in the handshake was out of range or inconsistent with
other fields. This is always fatal. other fields. This is always fatal.
] unknown_ca unknown_ca
] A valid certificate chain or partial chain was received, but the A valid certificate chain or partial chain was received, but the
] certificate was not accepted because the CA certificate could certificate was not accepted because the CA certificate could
] not be located or couldn`t be matched with a known, trusted CA. not be located or couldn`t be matched with a known, trusted CA.
] This message is always fatal. This message is always fatal.
] access_denied
] A valid certificate was received, but when access control was
] applied, the sender decided not to proceed with negotiation.
] This message is always fatal.
] decode_error access_denied
] A message could not be decoded because some field was out of the A valid certificate was received, but when access control was
] specified range or the length of the message was incorrect. This applied, the sender decided not to proceed with negotiation.
] message is always fatal. This message is always fatal.
| decrypt_error decode_error
| A handshake cryptographic operation failed, including being A message could not be decoded because some field was out of the
| unable to correctly verify a signature, decrypt a key exchange, specified range or the length of the message was incorrect. This
message is always fatal.
| or validate a finished message. decrypt_error
A handshake cryptographic operation failed, including being
unable to correctly verify a signature, decrypt a key exchange,
or validate a finished message.
] export_restriction export_restriction
] A negotiation not in compliance with export restrictions was A negotiation not in compliance with export restrictions was
] detected; for example, attempting to transfer a 1024 bit detected; for example, attempting to transfer a 1024 bit
] ephemeral RSA key for the RSA_EXPORT handshake method. This ephemeral RSA key for the RSA_EXPORT handshake method. This
] message is always fatal. message is always fatal.
] protocol_version protocol_version
] The protocol version the client has attempted to negotiate is The protocol version the client has attempted to negotiate is
] recognized, but not supported. (For example, old protocol recognized, but not supported. (For example, old protocol
] versions might be avoided for security reasons). This message is versions might be avoided for security reasons). This message is
] always fatal. always fatal.
] insufficient_security insufficient_security
] Returned instead of handshake_failure when a negotiation has Returned instead of handshake_failure when a negotiation has
] failed specifically because the server requires ciphers more failed specifically because the server requires ciphers more
] secure than those supported by the client. This message is secure than those supported by the client. This message is
] always fatal. always fatal.
] internal_error internal_error
] An internal error unrelated to the peer or the correctness of An internal error unrelated to the peer or the correctness of
] the protocol makes it impossible to continue (such as a memory the protocol makes it impossible to continue (such as a memory
] allocation failure). This message is always fatal. allocation failure). This message is always fatal.
] user_canceled user_canceled
] This handshake is being canceled for some reason unrelated to a This handshake is being canceled for some reason unrelated to a
] protocol failure. If the user cancels an operation after the protocol failure. If the user cancels an operation after the
] handshake is complete, just closing the connection by sending a handshake is complete, just closing the connection by sending a
] close_notify is more appropriate. This alert should be followed close_notify is more appropriate. This alert should be followed
] by a close_notify. This message is generally a warning. by a close_notify. This message is generally a warning.
] no_renegotiation no_renegotiation
] Sent by the client in response to a hello request or by the Sent by the client in response to a hello request or by the
] server in response to a client hello after initial handshaking. server in response to a client hello after initial handshaking.
] Either of these would normally lead to renegotiation; when that Either of these would normally lead to renegotiation; when that
] is not appropriate, the recipient should respond with this is not appropriate, the recipient should respond with this
] alert; at that point, the original requester can decide whether alert; at that point, the original requester can decide whether
] to proceed with the connection. One case where this would be to proceed with the connection. One case where this would be
] appropriate would be where a server has spawned a process to appropriate would be where a server has spawned a process to
] satisfy a request; the process might receive security parameters satisfy a request; the process might receive security parameters
] (key length, authentication, etc.) at startup and it might be (key length, authentication, etc.) at startup and it might be
] difficult to communicate changes to these parameters after that difficult to communicate changes to these parameters after that
] point. This message is always a warning. point. This message is always a warning.
For all errors where an alert level is not explicitly specified, the For all errors where an alert level is not explicitly specified, the
sending party may determine at its discretion whether this is a sending party may determine at its discretion whether this is a
fatal error or not; if an alert with a level of warning is received, fatal error or not; if an alert with a level of warning is received,
the receiving party may decide at its discretion whether to treat the receiving party may decide at its discretion whether to treat
this as a fatal error or not. However, all messages which are this as a fatal error or not. However, all messages which are
transmitted with a level of fatal must be treated as fatal messages. transmitted with a level of fatal must be treated as fatal messages.
7.3. Handshake Protocol overview 7.3. Handshake Protocol overview
The cryptographic parameters of the session state are produced by The cryptographic parameters of the session state are produced by
the TLS Handshake Protocol, which operates on top of the TLS Record the TLS Handshake Protocol, which operates on top of the TLS Record
Layer. When a TLS client and server first start communicating, they Layer. When a TLS client and server first start communicating, they
agree on a protocol version, select cryptographic algorithms, agree on a protocol version, select cryptographic algorithms,
optionally authenticate each other, and use public-key encryption optionally authenticate each other, and use public-key encryption
techniques to generate shared secrets. techniques to generate shared secrets.
| The TLS Handshake Protocol involves the following steps: The TLS Handshake Protocol involves the following steps:
- Exchange hello messages to agree on algorithms, exchange random - Exchange hello messages to agree on algorithms, exchange random
values, and check for session resumption. values, and check for session resumption.
- Exchange the necessary cryptographic parameters to allow the - Exchange the necessary cryptographic parameters to allow the
client and server to agree on a premaster secret. client and server to agree on a premaster secret.
- Exchange certificates and cryptographic information to allow the - Exchange certificates and cryptographic information to allow the
client and server to authenticate themselves. client and server to authenticate themselves.
- Generate a master secret from the premaster secret and exchanged - Generate a master secret from the premaster secret and exchanged
random values. random values.
- Provide security parameters to the record layer. - Provide security parameters to the record layer.
- Allow the client and server to verify that their peer has - Allow the client and server to verify that their peer has
calculated the same security parameters and that the handshake calculated the same security parameters and that the handshake
occurred without tampering by an attacker. occurred without tampering by an attacker.
] Note that higher layers should not be overly reliant on TLS always Note that higher layers should not be overly reliant on TLS always
] negotiating the strongest possible connection between two peers: negotiating the strongest possible connection between two peers:
] there are a number of ways a man in the middle attacker can attempt there are a number of ways a man in the middle attacker can attempt
] to make two entities drop down to the least secure method they to make two entities drop down to the least secure method they
] support. The protocol has been designed to minimize this risk, but support. The protocol has been designed to minimize this risk, but
] there are still attacks available: for example, an attacker could there are still attacks available: for example, an attacker could
] block access to the port a secure service runs on, or attempt to get block access to the port a secure service runs on, or attempt to get
] the peers to negotiate an unauthenticated connection. The the peers to negotiate an unauthenticated connection. The
] fundamental rule is that higher levels must be cognizant of what fundamental rule is that higher levels must be cognizant of what
] their security requirements are and never transmit information over their security requirements are and never transmit information over
] a channel less secure than what they require. The TLS protocol is a channel less secure than what they require. The TLS protocol is
] secure, in that any cipher suite offers its promised level of secure, in that any cipher suite offers its promised level of
] security: if you negotiate 3DES with a 1024 bit RSA key exchange security: if you negotiate 3DES with a 1024 bit RSA key exchange
] with a host whose certificate you have verified, you can expect to with a host whose certificate you have verified, you can expect to
] be that secure. However, you should never send data over a link be that secure. However, you should never send data over a link
] encrypted with 40 bit security unless you feel that data is worth no encrypted with 40 bit security unless you feel that data is worth no
] more than the effort required to break that encryption. more than the effort required to break that encryption.
These goals are achieved by the handshake protocol, which can be These goals are achieved by the handshake protocol, which can be
summarized as follows: The client sends a client hello message to summarized as follows: The client sends a client hello message to
which the server must respond with a server hello message, or else a which the server must respond with a server hello message, or else a
fatal error will occur and the connection will fail. The client fatal error will occur and the connection will fail. The client
hello and server hello are used to establish security enhancement hello and server hello are used to establish security enhancement
capabilities between client and server. The client hello and server capabilities between client and server. The client hello and server
hello establish the following attributes: Protocol Version, Session hello establish the following attributes: Protocol Version, Session
ID, Cipher Suite, and Compression Method. Additionally, two random ID, Cipher Suite, and Compression Method. Additionally, two random
values are generated and exchanged: ClientHello.random and values are generated and exchanged: ClientHello.random and
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Following the hello messages, the server will send its certificate, Following the hello messages, the server will send its certificate,
if it is to be authenticated. Additionally, a server key exchange if it is to be authenticated. Additionally, a server key exchange
message may be sent, if it is required (e.g. if their server has no message may be sent, if it is required (e.g. if their server has no
certificate, or if its certificate is for signing only). If the certificate, or if its certificate is for signing only). If the
server is authenticated, it may request a certificate from the server is authenticated, it may request a certificate from the
client, if that is appropriate to the cipher suite selected. Now the client, if that is appropriate to the cipher suite selected. Now the
server will send the server hello done message, indicating that the server will send the server hello done message, indicating that the
hello-message phase of the handshake is complete. The server will hello-message phase of the handshake is complete. The server will
then wait for a client response. If the server has sent a then wait for a client response. If the server has sent a
| certificate request message, the client must send the certificate certificate request message, the client must send the certificate
| message. The client key exchange message is now sent, and the message. The client key exchange message is now sent, and the
content of that message will depend on the public key algorithm content of that message will depend on the public key algorithm
selected between the client hello and the server hello. If the selected between the client hello and the server hello. If the
client has sent a certificate with signing ability, a client has sent a certificate with signing ability, a
digitally-signed certificate verify message is sent to explicitly digitally-signed certificate verify message is sent to explicitly
verify the certificate. verify the certificate.
At this point, a change cipher spec message is sent by the client, At this point, a change cipher spec message is sent by the client,
and the client copies the pending Cipher Spec into the current and the client copies the pending Cipher Spec into the current
Cipher Spec. The client then immediately sends the finished message Cipher Spec. The client then immediately sends the finished message
under the new algorithms, keys, and secrets. In response, the server under the new algorithms, keys, and secrets. In response, the server
skipping to change at page 29, line 11 skipping to change at page 29, line 11
<-------- ServerHelloDone <-------- ServerHelloDone
Certificate* Certificate*
ClientKeyExchange ClientKeyExchange
CertificateVerify* CertificateVerify*
[ChangeCipherSpec] [ChangeCipherSpec]
Finished --------> Finished -------->
[ChangeCipherSpec] [ChangeCipherSpec]
<-------- Finished <-------- Finished
Application Data <-------> Application Data Application Data <-------> Application Data
| Fig. 1 - Message flow for a full handshake Fig. 1 - Message flow for a full handshake
* Indicates optional or situation-dependent messages that are not * Indicates optional or situation-dependent messages that are not
always sent. always sent.
Note: To help avoid pipeline stalls, ChangeCipherSpec is an Note: To help avoid pipeline stalls, ChangeCipherSpec is an
independent TLS Protocol content type, and is not actually a TLS independent TLS Protocol content type, and is not actually a TLS
handshake message. handshake message.
When the client and server decide to resume a previous session or When the client and server decide to resume a previous session or
duplicate an existing session (instead of negotiating new security duplicate an existing session (instead of negotiating new security
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Client Server Client Server
ClientHello --------> ClientHello -------->
ServerHello ServerHello
[ChangeCipherSpec] [ChangeCipherSpec]
<-------- Finished <-------- Finished
[ChangeCipherSpec] [ChangeCipherSpec]
Finished --------> Finished -------->
Application Data <-------> Application Data Application Data <-------> Application Data
| Fig. 2 - Message flow for an abbreviated handshake Fig. 2 - Message flow for an abbreviated handshake
The contents and significance of each message will be presented in The contents and significance of each message will be presented in
detail in the following sections. detail in the following sections.
7.4. Handshake protocol 7.4. Handshake protocol
The TLS Handshake Protocol is one of the defined higher level The TLS Handshake Protocol is one of the defined higher level
clients of the TLS Record Protocol. This protocol is used to clients of the TLS Record Protocol. This protocol is used to
negotiate the secure attributes of a session. Handshake messages are negotiate the secure attributes of a session. Handshake messages are
supplied to the TLS Record Layer, where they are encapsulated within supplied to the TLS Record Layer, where they are encapsulated within
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case server_hello_done: ServerHelloDone; case server_hello_done: ServerHelloDone;
case certificate_verify: CertificateVerify; case certificate_verify: CertificateVerify;
case client_key_exchange: ClientKeyExchange; case client_key_exchange: ClientKeyExchange;
case finished: Finished; case finished: Finished;
} body; } body;
} Handshake; } Handshake;
The handshake protocol messages are presented below in the order The handshake protocol messages are presented below in the order
they must be sent; sending handshake messages in an unexpected order they must be sent; sending handshake messages in an unexpected order
results in a fatal error. Unneeded handshake messages can be results in a fatal error. Unneeded handshake messages can be
| omitted, however. Note one exception to the ordering: the omitted, however. Note one exception to the ordering: the
| Certificate message is used twice in the handshake (from server to Certificate message is used twice in the handshake (from server to
| client, then from client to server), but described only in its first client, then from client to server), but described only in its first
| position. The one message which is not bound by these ordering rules position. The one message which is not bound by these ordering rules
| in the Hello Request message, which can be sent at any time, but in the Hello Request message, which can be sent at any time, but
| which should be ignored by the client if it arrives in the middle of which should be ignored by the client if it arrives in the middle of
| a handshake. a handshake.
7.4.1. Hello messages 7.4.1. Hello messages
The hello phase messages are used to exchange security enhancement The hello phase messages are used to exchange security enhancement
capabilities between the client and server. When a new session capabilities between the client and server. When a new session
begins, the Record Layer's connection state encryption, hash, and begins, the Record Layer's connection state encryption, hash, and
compression algorithms are initialized to null. The current compression algorithms are initialized to null. The current
connection state is used for renegotiation messages. connection state is used for renegotiation messages.
7.4.1.1. Hello request 7.4.1.1. Hello request
When this message will be sent: When this message will be sent:
The hello request message may be sent by the server at any time. The hello request message may be sent by the server at any time.
Meaning of this message: Meaning of this message:
Hello request is a simple notification that the client should Hello request is a simple notification that the client should
begin the negotiation process anew by sending a client hello begin the negotiation process anew by sending a client hello
message when convenient. This message will be ignored by the message when convenient. This message will be ignored by the
client if the client is currently negotiating a session. This client if the client is currently negotiating a session. This
message may be ignored by the client if it does not wish to message may be ignored by the client if it does not wish to
| renegotiate a session, or the client may, if it wishes, respond renegotiate a session, or the client may, if it wishes, respond
| with a no_renegotiation alert. Since handshake messages are with a no_renegotiation alert. Since handshake messages are
intended to have transmission precedence over application data, intended to have transmission precedence over application data,
it is expected that the negotiation will begin before no more it is expected that the negotiation will begin before no more
than a few records are received from the client. If the server than a few records are received from the client. If the server
sends a hello request but does not receive a client hello in sends a hello request but does not receive a client hello in
response, it may close the connection with a fatal alert. response, it may close the connection with a fatal alert.
After sending a hello request, servers should not repeat the request After sending a hello request, servers should not repeat the request
until the subsequent handshake negotiation is complete. until the subsequent handshake negotiation is complete.
Structure of this message: Structure of this message:
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The client hello message includes a random structure, which is The client hello message includes a random structure, which is
used later in the protocol. used later in the protocol.
struct { struct {
uint32 gmt_unix_time; uint32 gmt_unix_time;
opaque random_bytes[28]; opaque random_bytes[28];
} Random; } Random;
gmt_unix_time gmt_unix_time
The current time and date in standard UNIX 32-bit format The current time and date in standard UNIX 32-bit format
| (seconds since the midnight starting Jan 1, 1970, GMT) according (seconds since the midnight starting Jan 1, 1970, GMT) according
to the sender's internal clock. Clocks are not required to be to the sender's internal clock. Clocks are not required to be
set correctly by the basic TLS Protocol; higher level or set correctly by the basic TLS Protocol; higher level or
application protocols may define additional requirements. application protocols may define additional requirements.
random_bytes random_bytes
28 bytes generated by a secure random number generator. 28 bytes generated by a secure random number generator.
The client hello message includes a variable length session The client hello message includes a variable length session
identifier. If not empty, the value identifies a session between the identifier. If not empty, the value identifies a session between the
same client and server whose security parameters the client wishes same client and server whose security parameters the client wishes
to reuse. The session identifier may be from an earlier connection, to reuse. The session identifier may be from an earlier connection,
this connection, or another currently active connection. The second this connection, or another currently active connection. The second
option is useful if the client only wishes to update the random option is useful if the client only wishes to update the random
structures and derived values of a connection, while the third structures and derived values of a connection, while the third
option makes it possible to establish several independent secure option makes it possible to establish several independent secure
connections without repeating the full handshake protocol. These connections without repeating the full handshake protocol. These
] independent connections may occur sequentially or simultaneously; a independent connections may occur sequentially or simultaneously; a
] SessionID becomes valid when the handshake negotiating it completes SessionID becomes valid when the handshake negotiating it completes
] with the exchange of Finished messages and persists until removed with the exchange of Finished messages and persists until removed
] due to aging or because a fatal error was encountered on a due to aging or because a fatal error was encountered on a
] connection associated with the session. The actual contents of the connection associated with the session. The actual contents of the
SessionID are defined by the server. SessionID are defined by the server.
opaque SessionID<0..32>; opaque SessionID<0..32>;
Warning: Warning:
] Because the SessionID is transmitted without encryption or Because the SessionID is transmitted without encryption or
] immediate MAC protection, servers must not place confidential immediate MAC protection, servers must not place confidential
] information in session identifiers or let the contents of fake information in session identifiers or let the contents of fake
] session identifiers cause any breach of security. (Note that the session identifiers cause any breach of security. (Note that the
] content of the handshake as a whole, including the SessionID, is content of the handshake as a whole, including the SessionID, is
] protected by the Finished messages exchanged at the end of the protected by the Finished messages exchanged at the end of the
] handshake.) handshake.)
The CipherSuite list, passed from the client to the server in the The CipherSuite list, passed from the client to the server in the
client hello message, contains the combinations of cryptographic client hello message, contains the combinations of cryptographic
algorithms supported by the client in order of the client's algorithms supported by the client in order of the client's
preference (favorite choice first). Each CipherSuite defines a key preference (favorite choice first). Each CipherSuite defines a key
exchange algorithm, a bulk encryption algorithm (including secret exchange algorithm, a bulk encryption algorithm (including secret
key length) and a MAC algorithm. The server will select a cipher key length) and a MAC algorithm. The server will select a cipher
suite or, if no acceptable choices are presented, return a handshake suite or, if no acceptable choices are presented, return a handshake
failure alert and close the connection. failure alert and close the connection.
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ProtocolVersion client_version; ProtocolVersion client_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suites<2..2^16-1>; CipherSuite cipher_suites<2..2^16-1>;
CompressionMethod compression_methods<1..2^8-1>; CompressionMethod compression_methods<1..2^8-1>;
} ClientHello; } ClientHello;
client_version client_version
The version of the TLS protocol by which the client wishes to The version of the TLS protocol by which the client wishes to
communicate during this session. This should be the latest communicate during this session. This should be the latest
(highest valued) version supported by the client. For this (highest valued) version supported by the client. For this
] version of the specification, the version will be 3.1 (See version of the specification, the version will be 3.1 (See
Appendix E for details about backward compatibility). Appendix E for details about backward compatibility).
random random
A client-generated random structure. A client-generated random structure.
session_id session_id
The ID of a session the client wishes to use for this The ID of a session the client wishes to use for this
connection. This field should be empty if no session_id is connection. This field should be empty if no session_id is
available or the client wishes to generate new security available or the client wishes to generate new security
parameters. parameters.
cipher_suites cipher_suites
This is a list of the cryptographic options supported by the This is a list of the cryptographic options supported by the
client, with the client's first preference first. If the client, with the client's first preference first. If the
session_id field is not empty (implying a session resumption session_id field is not empty (implying a session resumption
request) this vector must include at least the cipher_suite from request) this vector must include at least the cipher_suite from
that session. Values are defined in Appendix A.6. that session. Values are defined in Appendix A.5.
compression_methods compression_methods
This is a list of the compression methods supported by the This is a list of the compression methods supported by the
client, sorted by client preference. If the session_id field is client, sorted by client preference. If the session_id field is
not empty (implying a session resumption request) it must not empty (implying a session resumption request) it must
include the compression_method from that session. This vector include the compression_method from that session. This vector
must contain, and all implementations must support, must contain, and all implementations must support,
CompressionMethod.null. Thus, a client and server will always be CompressionMethod.null. Thus, a client and server will always be
able to agree on a compression method. able to agree on a compression method.
skipping to change at page 34, line 17 skipping to change at page 34, line 17
ProtocolVersion server_version; ProtocolVersion server_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suite; CipherSuite cipher_suite;
CompressionMethod compression_method; CompressionMethod compression_method;
} ServerHello; } ServerHello;
server_version server_version
This field will contain the lower of that suggested by the This field will contain the lower of that suggested by the
client in the client hello and the highest supported by the client in the client hello and the highest supported by the
] server. For this version of the specification, the version is server. For this version of the specification, the version is
] 3.1 (See Appendix E for details about backward compatibility). 3.1 (See Appendix E for details about backward compatibility).
random random
This structure is generated by the server and must be different This structure is generated by the server and must be different
from (and independent of) ClientHello.random. from (and independent of) ClientHello.random.
session_id session_id
This is the identity of the session corresponding to this This is the identity of the session corresponding to this
connection. If the ClientHello.session_id was non-empty, the connection. If the ClientHello.session_id was non-empty, the
server will look in its session cache for a match. If a match is server will look in its session cache for a match. If a match is
found and the server is willing to establish the new connection found and the server is willing to establish the new connection
using the specified session state, the server will respond with using the specified session state, the server will respond with
the same value as was supplied by the client. This indicates a the same value as was supplied by the client. This indicates a
resumed session and dictates that the parties must proceed resumed session and dictates that the parties must proceed
directly to the finished messages. Otherwise this field will directly to the finished messages. Otherwise this field will
contain a different value identifying the new session. The contain a different value identifying the new session. The
server may return an empty session_id to indicate that the server may return an empty session_id to indicate that the
] session will not be cached and therefore cannot be resumed. If a session will not be cached and therefore cannot be resumed. If a
] session is resumed, it must be resumed using the same cipher session is resumed, it must be resumed using the same cipher
] suite it was originally negotiated with. suite it was originally negotiated with.
cipher_suite cipher_suite
The single cipher suite selected by the server from the list in The single cipher suite selected by the server from the list in
ClientHello.cipher_suites. For resumed sessions this field is ClientHello.cipher_suites. For resumed sessions this field is
the value from the state of the session being resumed. the value from the state of the session being resumed.
compression_method compression_method
The single compression algorithm selected by the server from the The single compression algorithm selected by the server from the
list in ClientHello.compression_methods. For resumed sessions list in ClientHello.compression_methods. For resumed sessions
this field is the value from the resumed session state. this field is the value from the resumed session state.
skipping to change at page 35, line 41 skipping to change at page 35, line 41
DHE_RSA_EXPORT RSA public key which can be used for DHE_RSA_EXPORT RSA public key which can be used for
signing. signing.
DH_DSS Diffie-Hellman key. The algorithm used DH_DSS Diffie-Hellman key. The algorithm used
to sign the certificate should be DSS. to sign the certificate should be DSS.
DH_RSA Diffie-Hellman key. The algorithm used DH_RSA Diffie-Hellman key. The algorithm used
to sign the certificate should be RSA. to sign the certificate should be RSA.
] All certificate profiles, key and cryptographic formats are defined All certificate profiles, key and cryptographic formats are defined
| by the IETF PKIX working group [PKIX]. When a key usage extension is by the IETF PKIX working group [PKIX]. When a key usage extension is
| present, the digitalSignature bit must be set for the key to be present, the digitalSignature bit must be set for the key to be
| eligible for signing, as described above, and the keyEncipherment eligible for signing, as described above, and the keyEncipherment
| bit must be present to allow encryption, as described above. The bit must be present to allow encryption, as described above. The
| keyAgreement bit must be set on Diffie-Hellman certificates. keyAgreement bit must be set on Diffie-Hellman certificates.
As CipherSuites which specify new key exchange methods are specified As CipherSuites which specify new key exchange methods are specified
for the TLS Protocol, they will imply certificate format and the for the TLS Protocol, they will imply certificate format and the
required encoded keying information. required encoded keying information.
Structure of this message: Structure of this message:
opaque ASN.1Cert<1..2^24-1>; opaque ASN.1Cert<1..2^24-1>;
struct { struct {
ASN.1Cert certificate_list<0..2^24-1>; ASN.1Cert certificate_list<0..2^24-1>;
} Certificate; } Certificate;
certificate_list certificate_list
] This is a sequence (chain) of X.509v3 certificates. The sender's This is a sequence (chain) of X.509v3 certificates. The sender's
] certificate must come first in the list. Each following certificate must come first in the list. Each following
] certificate must directly certify the one preceding it. Because certificate must directly certify the one preceding it. Because
] certificate validation requires that root keys be distributed certificate validation requires that root keys be distributed
] independently, the self-signed certificate which specifies the independently, the self-signed certificate which specifies the
] root certificate authority may optionally be omitted from the root certificate authority may optionally be omitted from the
] chain, under the assumption that the remote end must already chain, under the assumption that the remote end must already
] possess it in order to validate it in any case. possess it in order to validate it in any case.
The same message type and structure will be used for the client's The same message type and structure will be used for the client's
] response to a certificate request message. Note that a client may response to a certificate request message. Note that a client may
] send no certificates if it does not have an appropriate certificate send no certificates if it does not have an appropriate certificate
] to send in response to the server's authentication request. to send in response to the server's authentication request.
Note: PKCS #7 [PKCS7] is not used as the format for the certificate Note: PKCS #7 [PKCS7] is not used as the format for the certificate
vector because PKCS #6 [PKCS6] extended certificates are not vector because PKCS #6 [PKCS6] extended certificates are not
used. Also PKCS #7 defines a SET rather than a SEQUENCE, making used. Also PKCS #7 defines a SET rather than a SEQUENCE, making
the task of parsing the list more difficult. the task of parsing the list more difficult.
7.4.3. Server key exchange message 7.4.3. Server key exchange message
] When this message will be sent: When this message will be sent:
] This message will be sent immediately after the server This message will be sent immediately after the server
] certificate message (or the server hello message, if this is an certificate message (or the server hello message, if this is an
] anonymous negotiation). anonymous negotiation).
The server key exchange message is sent by the server only when The server key exchange message is sent by the server only when
the server certificate message (if sent) does not contain enough the server certificate message (if sent) does not contain enough
data to allow the client to exchange a premaster secret. This is data to allow the client to exchange a premaster secret. This is
true for the following key exchange methods: true for the following key exchange methods:
RSA_EXPORT (if the public key in the server certificate is RSA_EXPORT (if the public key in the server certificate is
longer than 512 bits) longer than 512 bits)
DHE_DSS DHE_DSS
DHE_DSS_EXPORT DHE_DSS_EXPORT
skipping to change at page 38, line 44 skipping to change at page 38, line 44
case dsa: case dsa:
digitally-signed struct { digitally-signed struct {
opaque sha_hash[20]; opaque sha_hash[20];
}; };
} Signature; } Signature;
7.4.4. Certificate request 7.4.4. Certificate request
When this message will be sent: When this message will be sent:
A non-anonymous server can optionally request a certificate from A non-anonymous server can optionally request a certificate from
] the client, if appropriate for the selected cipher suite. This the client, if appropriate for the selected cipher suite. This
] message, if sent, will immediately follow the Server Key message, if sent, will immediately follow the Server Key
] Exchange message (if it is sent; otherwise, the Server Exchange message (if it is sent; otherwise, the Server
] Certificate message). Certificate message).
Structure of this message: Structure of this message:
enum { enum {
rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4), rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4),
(255) (255)
} ClientCertificateType; } ClientCertificateType;
opaque DistinguishedName<1..2^16-1>; opaque DistinguishedName<1..2^16-1>;
struct { struct {
ClientCertificateType certificate_types<1..2^8-1>; ClientCertificateType certificate_types<1..2^8-1>;
DistinguishedName certificate_authorities<3..2^16-1>; DistinguishedName certificate_authorities<3..2^16-1>;
} CertificateRequest; } CertificateRequest;
certificate_types certificate_types
This field is a list of the types of certificates requested, This field is a list of the types of certificates requested,
sorted in order of the server's preference. sorted in order of the server's preference.
certificate_authorities certificate_authorities
A list of the distinguished names of acceptable certificate A list of the distinguished names of acceptable certificate
] authorities. These distinguished names may specify a desired authorities. These distinguished names may specify a desired
] distinguished name for a root CA or for a subordinate CA; distinguished name for a root CA or for a subordinate CA;
] thus, this message can be used both to describe known roots thus, this message can be used both to describe known roots
] and a desired authorization space. and a desired authorization space.
Note: DistinguishedName is derived from [X509]. Note: DistinguishedName is derived from [X509].
Note: It is a fatal handshake_failure alert for an anonymous server to Note: It is a fatal handshake_failure alert for an anonymous server to
request client identification. request client identification.
7.4.5. Server hello done 7.4.5. Server hello done
When this message will be sent: When this message will be sent:
The server hello done message is sent by the server to indicate The server hello done message is sent by the server to indicate
skipping to change at page 39, line 52 skipping to change at page 39, line 52
Structure of this message: Structure of this message:
struct { } ServerHelloDone; struct { } ServerHelloDone;
7.4.6. Client certificate 7.4.6. Client certificate
When this message will be sent: When this message will be sent:
This is the first message the client can send after receiving a This is the first message the client can send after receiving a
server hello done message. This message is only sent if the server hello done message. This message is only sent if the
server requests a certificate. If no suitable certificate is server requests a certificate. If no suitable certificate is
] available, the client should send a certificate message available, the client should send a certificate message
] containing no certificates. If client authentication is required containing no certificates. If client authentication is required
] by the server for the handshake to continue, it may respond with by the server for the handshake to continue, it may respond with
] a fatal handshake failure alert. Client certificates are sent a fatal handshake failure alert. Client certificates are sent
using the Certificate structure defined in Section 7.4.2.
] using the Certificate structure defined in Section 7.4.2.
Note: When using a static Diffie-Hellman based key exchange method Note: When using a static Diffie-Hellman based key exchange method
(DH_DSS or DH_RSA), if client authentication is requested, the (DH_DSS or DH_RSA), if client authentication is requested, the
Diffie-Hellman group and generator encoded in the client's Diffie-Hellman group and generator encoded in the client's
certificate must match the server specified Diffie-Hellman certificate must match the server specified Diffie-Hellman
parameters if the client's parameters are to be used for the key parameters if the client's parameters are to be used for the key
exchange. exchange.
7.4.7. Client key exchange message 7.4.7. Client key exchange message
When this message will be sent: When this message will be sent:
This message is always sent by the client. It will immediately This message is always sent by the client. It will immediately
] follow the client certificate message, if it is sent. Otherwise follow the client certificate message, if it is sent. Otherwise
] it will be the first message sent by the client after it it will be the first message sent by the client after it
] receives the server hello done message. receives the server hello done message.
Meaning of this message: Meaning of this message:
With this message, the premaster secret is set, either though With this message, the premaster secret is set, either though
direct transmission of the RSA-encrypted secret, or by the direct transmission of the RSA-encrypted secret, or by the
transmission of Diffie-Hellman parameters which will allow each transmission of Diffie-Hellman parameters which will allow each
side to agree upon the same premaster secret. When the key side to agree upon the same premaster secret. When the key
exchange method is DH_RSA or DH_DSS, client certification has exchange method is DH_RSA or DH_DSS, client certification has
been requested, and the client was able to respond with a been requested, and the client was able to respond with a
certificate which contained a Diffie-Hellman public key whose certificate which contained a Diffie-Hellman public key whose
parameters (group and generator) matched those specified by the parameters (group and generator) matched those specified by the
skipping to change at page 41, line 13 skipping to change at page 41, line 13
in itself. in itself.
Structure of this message: Structure of this message:
struct { struct {
ProtocolVersion client_version; ProtocolVersion client_version;
opaque random[46]; opaque random[46];
} PreMasterSecret; } PreMasterSecret;
client_version client_version
The latest (newest) version supported by the client. This is The latest (newest) version supported by the client. This is
] used to detect version roll-back attacks. Upon receiving the used to detect version roll-back attacks. Upon receiving the
] premaster secret, the server should check that this value premaster secret, the server should check that this value
] matches the value transmitted by the client in the client matches the value transmitted by the client in the client
] hello message. hello message.
random random
46 securely-generated random bytes. 46 securely-generated random bytes.
struct { struct {
public-key-encrypted PreMasterSecret pre_master_secret; public-key-encrypted PreMasterSecret pre_master_secret;
} EncryptedPreMasterSecret; } EncryptedPreMasterSecret;
pre_master_secret pre_master_secret
This random value is generated by the client and is used to This random value is generated by the client and is used to
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The encoding used for Yc is determined by the enumerated The encoding used for Yc is determined by the enumerated
PublicValueEncoding. This structure is a variant of the client PublicValueEncoding. This structure is a variant of the client
key exchange message, not a message in itself. key exchange message, not a message in itself.
Structure of this message: Structure of this message:
enum { implicit, explicit } PublicValueEncoding; enum { implicit, explicit } PublicValueEncoding;
implicit implicit
If the client certificate already contains a suitable If the client certificate already contains a suitable
Diffie-Hellman key, then Yc is implicit and does not need to Diffie-Hellman key, then Yc is implicit and does not need to
] be sent again. In this case, the Client Key Exchange message be sent again. In this case, the Client Key Exchange message
] will be sent, but will be empty. will be sent, but will be empty.
explicit explicit
Yc needs to be sent. Yc needs to be sent.
struct { struct {
select (PublicValueEncoding) { select (PublicValueEncoding) {
case implicit: struct { }; case implicit: struct { };
case explicit: opaque dh_Yc<1..2^16-1>; case explicit: opaque dh_Yc<1..2^16-1>;
} dh_public; } dh_public;
} ClientDiffieHellmanPublic; } ClientDiffieHellmanPublic;
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message. message.
Structure of this message: Structure of this message:
struct { struct {
Signature signature; Signature signature;
} CertificateVerify; } CertificateVerify;
The Signature type is defined in 6.4.3. The Signature type is defined in 6.4.3.
CertificateVerify.signature.md5_hash CertificateVerify.signature.md5_hash
| MD5(handshake_messages); MD5(handshake_messages);
Certificate.signature.sha_hash Certificate.signature.sha_hash
| SHA(handshake_messages); SHA(handshake_messages);
Here handshake_messages refers to all handshake messages sent or Here handshake_messages refers to all handshake messages sent or
received starting at client hello up to but not including this received starting at client hello up to but not including this
message, including the type and length fields of the handshake message, including the type and length fields of the handshake
messages. This is the concatenation of all the Handshake structures messages. This is the concatenation of all the Handshake structures
as defined in 7.4 exchanged thus far. as defined in 7.4 exchanged thus far.
7.4.9. Finished 7.4.9. Finished
When this message will be sent: When this message will be sent:
A finished message is always sent immediately after a change A finished message is always sent immediately after a change
cipher spec message to verify that the key exchange and cipher spec message to verify that the key exchange and
authentication processes were successful. It is essential that a authentication processes were successful. It is essential that a
change cipher spec message be received between the other change cipher spec message be received between the other
handshake messages and the Finished message. handshake messages and the Finished message.
Meaning of this message: Meaning of this message:
The finished message is the first protected with the The finished message is the first protected with the
] just-negotiated algorithms, keys, and secrets. Recipients of just-negotiated algorithms, keys, and secrets. Recipients of
] finished messages must verify that the contents are correct. finished messages must verify that the contents are correct.
] Once a side has sent its Finished message and received and Once a side has sent its Finished message and received and
] validated the Finished message from its peer, it may begin to validated the Finished message from its peer, it may begin to
] send and receive application data over the connection. send and receive application data over the connection.
| struct {
| opaque verify_data[12];
| } Finished;
| verify_data struct {
| PRF(master_secret, finished_label, MD5(handshake_messages) + opaque verify_data[12];
| SHA-1(handshake_messages)) [0..11]; } Finished;
verify_data
PRF(master_secret, finished_label, MD5(handshake_messages) +
SHA-1(handshake_messages)) [0..11];
| finished_label finished_label
| For Finished messages sent by the client, the string "client For Finished messages sent by the client, the string "client
| finished". For Finished messages sent by the server, the finished". For Finished messages sent by the server, the
| string "server finished". string "server finished".
handshake_messages handshake_messages
All of the data from all handshake messages up to but not All of the data from all handshake messages up to but not
including this message. This is only data visible at the including this message. This is only data visible at the
handshake layer and does not include record layer headers. handshake layer and does not include record layer headers.
This is the concatenation of all the Handshake structures as This is the concatenation of all the Handshake structures as
defined in 7.4 exchanged thus far. defined in 7.4 exchanged thus far.
It is a fatal error if a finished message is not preceded by a It is a fatal error if a finished message is not preceded by a
change cipher spec message at the appropriate point in the change cipher spec message at the appropriate point in the
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incorporate Sender.server; those sent by the client incorporate incorporate Sender.server; those sent by the client incorporate
Sender.client. The value handshake_messages includes all handshake Sender.client. The value handshake_messages includes all handshake
messages starting at client hello up to, but not including, this messages starting at client hello up to, but not including, this
finished message. This may be different from handshake_messages in finished message. This may be different from handshake_messages in
Section 7.4.8 because it would include the certificate verify Section 7.4.8 because it would include the certificate verify
message (if sent). Also, the handshake_messages for the finished message (if sent). Also, the handshake_messages for the finished
message sent by the client will be different from that for the message sent by the client will be different from that for the
finished message sent by the server, because the one which is sent finished message sent by the server, because the one which is sent
second will include the prior one. second will include the prior one.
|Note: Change cipher spec messages, alerts and any other record types Note: Change cipher spec messages, alerts and any other record types
are not handshake messages and are not included in the hash are not handshake messages and are not included in the hash
] computations. Also, Hello Request messages are omitted from computations. Also, Hello Request messages are omitted from
] handshake hashes. handshake hashes.
8. Cryptographic computations 8. Cryptographic computations
In order to begin connection protection, the TLS Record Protocol In order to begin connection protection, the TLS Record Protocol
requires specification of a suite of algorithms, a master secret, requires specification of a suite of algorithms, a master secret,
and the client and server random values. The authentication, and the client and server random values. The authentication,
encryption, and MAC algorithms are determined by the cipher_suite encryption, and MAC algorithms are determined by the cipher_suite
selected by the server and revealed in the server hello message. The selected by the server and revealed in the server hello message. The
compression algorithm is negotiated in the hello messages, and the compression algorithm is negotiated in the hello messages, and the
random values are exchanged in the hello messages. All that remains random values are exchanged in the hello messages. All that remains
is to calculate the master secret. is to calculate the master secret.
8.1. Computing the master secret 8.1. Computing the master secret
For all key exchange methods, the same algorithm is used to convert For all key exchange methods, the same algorithm is used to convert
the pre_master_secret into the master_secret. The pre_master_secret the pre_master_secret into the master_secret. The pre_master_secret
should be deleted from memory once the master_secret has been should be deleted from memory once the master_secret has been
computed. computed.
| master_secret = PRF(pre_master_secret, "master secret", master_secret = PRF(pre_master_secret, "master secret",
| ClientHello.random + ServerHello.random) [0..47]; ClientHello.random + ServerHello.random)
[0..47];
The master secret is always exactly 48 bytes in length. The length The master secret is always exactly 48 bytes in length. The length
of the premaster secret will vary depending on key exchange method. of the premaster secret will vary depending on key exchange method.
8.1.1. RSA 8.1.1. RSA
When RSA is used for server authentication and key exchange, a When RSA is used for server authentication and key exchange, a
48-byte pre_master_secret is generated by the client, encrypted 48-byte pre_master_secret is generated by the client, encrypted
under the server's public key, and sent to the server. The server under the server's public key, and sent to the server. The server
uses its private key to decrypt the pre_master_secret. Both parties uses its private key to decrypt the pre_master_secret. Both parties
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8.1.2. Diffie-Hellman 8.1.2. Diffie-Hellman
A conventional Diffie-Hellman computation is performed. The A conventional Diffie-Hellman computation is performed. The
negotiated key (Z) is used as the pre_master_secret, and is negotiated key (Z) is used as the pre_master_secret, and is
converted into the master_secret, as specified above. converted into the master_secret, as specified above.
Note: Diffie-Hellman parameters are specified by the server, and may Note: Diffie-Hellman parameters are specified by the server, and may
be either ephemeral or contained within the server's be either ephemeral or contained within the server's
certificate. certificate.
9. Application data protocol 9. Mandatory Cipher Suites
In the absence of an application profile standard specifying
otherwise, a TLS compliant application MUST implement the cipher
suite TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA.
10. Application data protocol
Application data messages are carried by the Record Layer and are Application data messages are carried by the Record Layer and are
fragmented, compressed and encrypted based on the current connection fragmented, compressed and encrypted based on the current connection
state. The messages are treated as transparent data to the record state. The messages are treated as transparent data to the record
layer. layer.
A. Protocol constant values A. Protocol constant values
This section describes protocol types and constants. This section describes protocol types and constants.
A.1. Reserved port assignments A.1. Record layer
At the present time TLS is implemented using TCP/IP as the base
] networking technology, although the protocol should be useful over
] any transport which can provide a reliable stream connection. The
IANA reserved the following Internet Protocol [IP] port numbers for
use in conjunction with the SSL 3.0 Protocol, which we presume will
be used by TLS as well.
| While we describe these existing port assignments for completeness,
| in general, protocol designers and implementors should be the ones
| to decide on how security can be incorporated into their protocol
| using TLS, including the mechanisms for negotiating to start TLS and
| the requirements and meaning of that connection (such as
| interpretation of exchanged certificates).
443 Reserved for use by Hypertext Transfer Protocol with SSL (https)
465 Reserved for use by Simple Mail Transfer Protocol with SSL
(ssmtp).
563 Reserved for use by Network News Transfer Protocol with SSL
(snntp).
636 Reserved for Light Directory Access Protocol with SSL (ssl-ldap)
990 Reserved (pending) for File Transfer Protocol with SSL (ftps)
995 Reserved for Post Office Protocol with SSL (spop3)
A.2. Record layer
struct { struct {
uint8 major, minor; uint8 major, minor;
} ProtocolVersion; } ProtocolVersion;
ProtocolVersion version = { 3, 1 }; /* TLS v1.0 */ ProtocolVersion version = { 3, 1 }; /* TLS v1.0 */
enum { enum {
change_cipher_spec(20), alert(21), handshake(22), change_cipher_spec(20), alert(21), handshake(22),
application_data(23), (255) application_data(23), (255)
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opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
} GenericStreamCipher; } GenericStreamCipher;
block-ciphered struct { block-ciphered struct {
opaque content[TLSCompressed.length]; opaque content[TLSCompressed.length];
opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
uint8 padding[GenericBlockCipher.padding_length]; uint8 padding[GenericBlockCipher.padding_length];
uint8 padding_length; uint8 padding_length;
} GenericBlockCipher; } GenericBlockCipher;
A.3. Change cipher specs message A.2. Change cipher specs message
struct { struct {
enum { change_cipher_spec(1), (255) } type; enum { change_cipher_spec(1), (255) } type;
} ChangeCipherSpec; } ChangeCipherSpec;
A.4. Alert messages A.3. Alert messages
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
enum { enum {
close_notify(0), close_notify(0),
unexpected_message(10), unexpected_message(10),
bad_record_mac(20), bad_record_mac(20),
] decryption_failed(21), decryption_failed(21),
] record_overflow(22), record_overflow(22),
decompression_failure(30), decompression_failure(30),
handshake_failure(40), handshake_failure(40),
bad_certificate(42), bad_certificate(42),
unsupported_certificate(43), unsupported_certificate(43),
certificate_revoked(44), certificate_revoked(44),
certificate_expired(45), certificate_expired(45),
certificate_unknown(46), certificate_unknown(46),
illegal_parameter(47), illegal_parameter(47),
] unknown_ca(48), unknown_ca(48),
] access_denied(49), access_denied(49),
] decode_error(50), decode_error(50),
] decrypt_error(51), decrypt_error(51),
] export_restriction(60), export_restriction(60),
] protocol_version(70), protocol_version(70),
] insufficient_security(71), insufficient_security(71),
] internal_error(80), internal_error(80),
] user_canceled(90), user_canceled(90),
] no_renegotiation(100), no_renegotiation(100),
(255) (255)
} AlertDescription; } AlertDescription;
struct { struct {
AlertLevel level; AlertLevel level;
AlertDescription description; AlertDescription description;
} Alert; } Alert;
A.5. Handshake protocol A.4. Handshake protocol
enum { enum {
hello_request(0), client_hello(1), server_hello(2), hello_request(0), client_hello(1), server_hello(2),
certificate(11), server_key_exchange (12), certificate(11), server_key_exchange (12),
certificate_request(13), server_hello_done(14), certificate_request(13), server_hello_done(14),
certificate_verify(15), client_key_exchange(16), certificate_verify(15), client_key_exchange(16),
finished(20), (255) finished(20), (255)
} HandshakeType; } HandshakeType;
struct { struct {
skipping to change at page 47, line 39 skipping to change at page 47, line 15
case certificate: Certificate; case certificate: Certificate;
case server_key_exchange: ServerKeyExchange; case server_key_exchange: ServerKeyExchange;
case certificate_request: CertificateRequest; case certificate_request: CertificateRequest;
case server_hello_done: ServerHelloDone; case server_hello_done: ServerHelloDone;
case certificate_verify: CertificateVerify; case certificate_verify: CertificateVerify;
case client_key_exchange: ClientKeyExchange; case client_key_exchange: ClientKeyExchange;
case finished: Finished; case finished: Finished;
} body; } body;
} Handshake; } Handshake;
A.5.1. Hello messages A.4.1. Hello messages
struct { } HelloRequest; struct { } HelloRequest;
struct { struct {
uint32 gmt_unix_time; uint32 gmt_unix_time;
opaque random_bytes[28]; opaque random_bytes[28];
} Random; } Random;
opaque SessionID<0..32>; opaque SessionID<0..32>;
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} ClientHello; } ClientHello;
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suite; CipherSuite cipher_suite;
CompressionMethod compression_method; CompressionMethod compression_method;
} ServerHello; } ServerHello;
A.5.2. Server authentication and key exchange messages A.4.2. Server authentication and key exchange messages
opaque ASN.1Cert<2^24-1>; opaque ASN.1Cert<2^24-1>;
struct { struct {
ASN.1Cert certificate_list<1..2^24-1>; ASN.1Cert certificate_list<1..2^24-1>;
} Certificate; } Certificate;
enum { rsa, diffie_hellman } KeyExchangeAlgorithm; enum { rsa, diffie_hellman } KeyExchangeAlgorithm;
struct { struct {
opaque RSA_modulus<1..2^16-1>; opaque RSA_modulus<1..2^16-1>;
opaque RSA_exponent<1..2^16-1>; opaque RSA_exponent<1..2^16-1>;
} ServerRSAParams; } ServerRSAParams;
struct { struct {
opaque DH_p<1..2^16-1>; opaque DH_p<1..2^16-1>;
opaque DH_g<1..2^16-1>; opaque DH_g<1..2^16-1>;
opaque DH_Ys<1..2^16-1>; opaque DH_Ys<1..2^16-1>;
} ServerDHParams; } ServerDHParams;
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opaque DistinguishedName<1..2^16-1>; opaque DistinguishedName<1..2^16-1>;
struct { struct {
ClientCertificateType certificate_types<1..2^8-1>; ClientCertificateType certificate_types<1..2^8-1>;
DistinguishedName certificate_authorities<3..2^16-1>; DistinguishedName certificate_authorities<3..2^16-1>;
} CertificateRequest; } CertificateRequest;
struct { } ServerHelloDone; struct { } ServerHelloDone;
A.5.3. Client authentication and key exchange messages A.4.3. Client authentication and key exchange messages
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
case rsa: EncryptedPreMasterSecret; case rsa: EncryptedPreMasterSecret;
case diffie_hellman: DiffieHellmanClientPublicValue; case diffie_hellman: DiffieHellmanClientPublicValue;
} exchange_keys; } exchange_keys;
} ClientKeyExchange; } ClientKeyExchange;
struct { struct {
ProtocolVersion client_version; ProtocolVersion client_version;
skipping to change at page 50, line 6 skipping to change at page 49, line 36
select (PublicValueEncoding) { select (PublicValueEncoding) {
case implicit: struct {}; case implicit: struct {};
case explicit: opaque DH_Yc<1..2^16-1>; case explicit: opaque DH_Yc<1..2^16-1>;
} dh_public; } dh_public;
} ClientDiffieHellmanPublic; } ClientDiffieHellmanPublic;
struct { struct {
Signature signature; Signature signature;
} CertificateVerify; } CertificateVerify;
A.5.4. Handshake finalization message A.4.4. Handshake finalization message
struct { struct {
| opaque verify_data[12]; opaque verify_data[12];
} Finished; } Finished;
A.6. The CipherSuite A.5. The CipherSuite
The following values define the CipherSuite codes used in the client The following values define the CipherSuite codes used in the client
hello and server hello messages. hello and server hello messages.
A CipherSuite defines a cipher specification supported in TLS A CipherSuite defines a cipher specification supported in TLS
Version 1.0. Version 1.0.
| TLS_NULL_WITH_NULL_NULL is specified and is the initial state of a TLS_NULL_WITH_NULL_NULL is specified and is the initial state of a
| TLS connection during the first handshake on that channel, but TLS connection during the first handshake on that channel, but must
| should not be negotiated, as it provides no more protection than an not be negotiated, as it provides no more protection than an
| unsecured connection. unsecured connection.
CipherSuite TLS_NULL_WITH_NULL_NULL = { 0x00,0x00 }; CipherSuite TLS_NULL_WITH_NULL_NULL = { 0x00,0x00 };
The following CipherSuite definitions require that the server The following CipherSuite definitions require that the server
provide an RSA certificate that can be used for key exchange. The provide an RSA certificate that can be used for key exchange. The
server may request either an RSA or a DSS signature-capable server may request either an RSA or a DSS signature-capable
certificate in the certificate request message. certificate in the certificate request message.
CipherSuite TLS_RSA_WITH_NULL_MD5 = { 0x00,0x01 }; CipherSuite TLS_RSA_WITH_NULL_MD5 = { 0x00,0x01 };
CipherSuite TLS_RSA_WITH_NULL_SHA = { 0x00,0x02 }; CipherSuite TLS_RSA_WITH_NULL_SHA = { 0x00,0x02 };
skipping to change at page 50, line 50 skipping to change at page 50, line 30
CipherSuite TLS_RSA_WITH_DES_CBC_SHA = { 0x00,0x09 }; CipherSuite TLS_RSA_WITH_DES_CBC_SHA = { 0x00,0x09 };
CipherSuite TLS_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0A }; CipherSuite TLS_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0A };
The following CipherSuite definitions are used for The following CipherSuite definitions are used for
server-authenticated (and optionally client-authenticated) server-authenticated (and optionally client-authenticated)
Diffie-Hellman. DH denotes cipher suites in which the server's Diffie-Hellman. DH denotes cipher suites in which the server's
certificate contains the Diffie-Hellman parameters signed by the certificate contains the Diffie-Hellman parameters signed by the
certificate authority (CA). DHE denotes ephemeral Diffie-Hellman, certificate authority (CA). DHE denotes ephemeral Diffie-Hellman,
where the Diffie-Hellman parameters are signed by a DSS or RSA where the Diffie-Hellman parameters are signed by a DSS or RSA
certificate, which has been signed by the CA. The signing algorithm certificate, which has been signed by the CA. The signing algorithm
] used is specified after the DH or DHE parameter. The server can used is specified after the DH or DHE parameter. The server can
] request an RSA or DSS signature-capable certificate from the client request an RSA or DSS signature-capable certificate from the client
] for client authentication or it may request a Diffie-Hellman for client authentication or it may request a Diffie-Hellman
] certificate. Any Diffie-Hellman certificate provided by the client certificate. Any Diffie-Hellman certificate provided by the client
] must use the parameters (group and generator) described by the must use the parameters (group and generator) described by the
] server. server.
CipherSuite TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0B }; CipherSuite TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0B };
CipherSuite TLS_DH_DSS_WITH_DES_CBC_SHA = { 0x00,0x0C }; CipherSuite TLS_DH_DSS_WITH_DES_CBC_SHA = { 0x00,0x0C };
CipherSuite TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0D }; CipherSuite TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x0D };
CipherSuite TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0E }; CipherSuite TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x0E };
CipherSuite TLS_DH_RSA_WITH_DES_CBC_SHA = { 0x00,0x0F }; CipherSuite TLS_DH_RSA_WITH_DES_CBC_SHA = { 0x00,0x0F };
CipherSuite TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x10 }; CipherSuite TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00,0x10 };
CipherSuite TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x11 }; CipherSuite TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x11 };
CipherSuite TLS_DHE_DSS_WITH_DES_CBC_SHA = { 0x00,0x12 }; CipherSuite TLS_DHE_DSS_WITH_DES_CBC_SHA = { 0x00,0x12 };
CipherSuite TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x13 }; CipherSuite TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA = { 0x00,0x13 };
skipping to change at page 51, line 35 skipping to change at page 51, line 17
CipherSuite TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x19 }; CipherSuite TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA = { 0x00,0x19 };
CipherSuite TLS_DH_anon_WITH_DES_CBC_SHA = { 0x00,0x1A }; CipherSuite TLS_DH_anon_WITH_DES_CBC_SHA = { 0x00,0x1A };
CipherSuite TLS_DH_anon_WITH_3DES_EDE_CBC_SHA = { 0x00,0x1B }; CipherSuite TLS_DH_anon_WITH_3DES_EDE_CBC_SHA = { 0x00,0x1B };
Note: All cipher suites whose first byte is 0xFF are considered Note: All cipher suites whose first byte is 0xFF are considered
private and can be used for defining local/experimental private and can be used for defining local/experimental
algorithms. Interoperability of such types is a local matter. algorithms. Interoperability of such types is a local matter.
Note: Additional cipher suites will be considered for implementation Note: Additional cipher suites will be considered for implementation
only with submission of notarized letters from two independent only with submission of notarized letters from two independent
] entities. Consensus Development Corp. will act as an interim entities. Consensus Development Corp. will act as an interim
registration office, until a public standards body assumes registration office, until a public standards body assumes
control of TLS cipher suites. control of TLS cipher suites.
A.7. The Security Parameters A.6. The Security Parameters
These security parameters are determined by the TLS Handshake These security parameters are determined by the TLS Handshake
Protocol and provided as parameters to the TLS Record Layer in order Protocol and provided as parameters to the TLS Record Layer in order
to initialize a connection state. SecurityParameters includes: to initialize a connection state. SecurityParameters includes:
enum { null(0), (255) } CompressionMethod; enum { null(0), (255) } CompressionMethod;
enum { server, client } ConnectionEnd; enum { server, client } ConnectionEnd;
enum { null, rc4, rc2, des, 3des, des40, idea } enum { null, rc4, rc2, des, 3des, des40, idea }
skipping to change at page 52, line 50 skipping to change at page 52, line 31
groups of bits, called blocks. 64 bits is a common block size. groups of bits, called blocks. 64 bits is a common block size.
bulk cipher bulk cipher
A symmetric encryption algorithm used to encrypt large A symmetric encryption algorithm used to encrypt large
quantities of data. quantities of data.
cipher block chaining (CBC) cipher block chaining (CBC)
CBC is a mode in which every plaintext block encrypted with a CBC is a mode in which every plaintext block encrypted with a
block cipher is first exclusive-ORed with the previous block cipher is first exclusive-ORed with the previous
ciphertext block (or, in the case of the first block, with the ciphertext block (or, in the case of the first block, with the
] initialization vector). For decryption, every block is first initialization vector). For decryption, every block is first
] decrypted, then exclusive-ORed with the previous ciphertext decrypted, then exclusive-ORed with the previous ciphertext
] block (or IV). block (or IV).
certificate certificate
As part of the X.509 protocol (a.k.a. ISO Authentication As part of the X.509 protocol (a.k.a. ISO Authentication
framework), certificates are assigned by a trusted Certificate framework), certificates are assigned by a trusted Certificate
| Authority and provide a strong binding between a party's Authority and provide a strong binding between a party's
| identity or some other attributes and its public key. identity or some other attributes and its public key.
client client
| The application entity that initiates a TLS connection to a The application entity that initiates a TLS connection to a
| server. This may or may not imply that the client initiated the server. This may or may not imply that the client initiated the
| underlying transport connection. The primary operational underlying transport connection. The primary operational
| difference between the server and client is that the server is difference between the server and client is that the server is
| generally authenticated, while the client is only optionally generally authenticated, while the client is only optionally
| authenticated. authenticated.
client write key client write key
The key used to encrypt data written by the client. The key used to encrypt data written by the client.
client write MAC secret client write MAC secret
The secret data used to authenticate data written by the client. The secret data used to authenticate data written by the client.
connection connection
A connection is a transport (in the OSI layering model A connection is a transport (in the OSI layering model
definition) that provides a suitable type of service. For TLS, definition) that provides a suitable type of service. For TLS,
such connections are peer to peer relationships. The connections such connections are peer to peer relationships. The connections
are transient. Every connection is associated with one session. are transient. Every connection is associated with one session.
Data Encryption Standard Data Encryption Standard
DES is a very widely used symmetric encryption algorithm. DES is DES is a very widely used symmetric encryption algorithm. DES is
] a block cipher with a 56 bit key and an 8 byte block size. Note a block cipher with a 56 bit key and an 8 byte block size. Note
] that in TLS, for key generation purposes, DES is treated as that in TLS, for key generation purposes, DES is treated as
] having an 8 byte key length (64 bits), but it still only having an 8 byte key length (64 bits), but it still only
] provides 56 bits of protection. DES can also be operated in a provides 56 bits of protection. DES can also be operated in a
] mode where three independent keys and three encryptions are used mode where three independent keys and three encryptions are used
] for each block of data; this uses 168 bits of key (24 bytes in for each block of data; this uses 168 bits of key (24 bytes in
] the TLS key generation method) and provides the equivalent of the TLS key generation method) and provides the equivalent of
] 112 bits of security. [DES], [3DES] 112 bits of security. [DES], [3DES]
Digital Signature Standard (DSS) Digital Signature Standard (DSS)
A standard for digital signing, including the Digital Signing A standard for digital signing, including the Digital Signing
Algorithm, approved by the National Institute of Standards and Algorithm, approved by the National Institute of Standards and
Technology, defined in NIST FIPS PUB 186, "Digital Signature Technology, defined in NIST FIPS PUB 186, "Digital Signature
Standard," published May, 1994 by the U.S. Dept. of Commerce. Standard," published May, 1994 by the U.S. Dept. of Commerce.
[DSS] [DSS]
digital signatures digital signatures
Digital signatures utilize public key cryptography and one-way Digital signatures utilize public key cryptography and one-way
skipping to change at page 54, line 16 skipping to change at page 53, line 49
When a block cipher is used in CBC mode, the initialization When a block cipher is used in CBC mode, the initialization
vector is exclusive-ORed with the first plaintext block prior to vector is exclusive-ORed with the first plaintext block prior to
encryption. encryption.
IDEA IDEA
A 64-bit block cipher designed by Xuejia Lai and James Massey. A 64-bit block cipher designed by Xuejia Lai and James Massey.
[IDEA] [IDEA]
Message Authentication Code (MAC) Message Authentication Code (MAC)
A Message Authentication Code is a one-way hash computed from a A Message Authentication Code is a one-way hash computed from a
] message and some secret data. It is difficult to forge without message and some secret data. It is difficult to forge without
] knowing the secret data and it is difficult to find messages knowing the secret data and it is difficult to find messages
] which hash to the same MAC. Its purpose is to detect if the which hash to the same MAC. Its purpose is to detect if the
message has been altered. message has been altered.
master secret master secret
Secure secret data used for generating encryption keys, MAC Secure secret data used for generating encryption keys, MAC
secrets, and IVs. secrets, and IVs.
MD5 MD5
MD5 is a secure hashing function that converts an arbitrarily MD5 is a secure hashing function that converts an arbitrarily
long data stream into a digest of fixed size (16 bytes). [MD5] long data stream into a digest of fixed size (16 bytes). [MD5]
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Messages encrypted with the public key can only be decrypted Messages encrypted with the public key can only be decrypted
with the associated private key. Conversely, messages signed with the associated private key. Conversely, messages signed
with the private key can be verified with the public key. with the private key can be verified with the public key.
one-way hash function one-way hash function
A one-way transformation that converts an arbitrary amount of A one-way transformation that converts an arbitrary amount of
data into a fixed-length hash. It is computationally hard to data into a fixed-length hash. It is computationally hard to
reverse the transformation or to find collisions. MD5 and SHA reverse the transformation or to find collisions. MD5 and SHA
are examples of one-way hash functions. are examples of one-way hash functions.
| RC2 RC2
| A proprietary block cipher from RSA Data Security, Inc. A block cipher developed by Ron Rivest at RSA Data Security,
| [RSADSI]. Inc. [RSADSI] described in [RC2].
| RC4 RC4
| A stream cipher licensed by RSA Data Security [RSADSI]. A A stream cipher licensed by RSA Data Security [RSADSI]. A
| compatible cipher is described in [RC4]. compatible cipher is described in [RC4].
RSA RSA
A very widely used public-key algorithm that can be used for A very widely used public-key algorithm that can be used for
either encryption or digital signing. [RSA] either encryption or digital signing. [RSA]
salt salt
Non-secret random data used to make export encryption keys Non-secret random data used to make export encryption keys
resist precomputation attacks. resist precomputation attacks.
server server
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identifies a particular session. identifies a particular session.
server write key server write key
The key used to encrypt data written by the server. The key used to encrypt data written by the server.
server write MAC secret server write MAC secret
The secret data used to authenticate data written by the server. The secret data used to authenticate data written by the server.
SHA SHA
The Secure Hash Algorithm is defined in FIPS PUB 180-1. It The Secure Hash Algorithm is defined in FIPS PUB 180-1. It
] produces a 20-byte output. Note that all references to SHA produces a 20-byte output. Note that all references to SHA
] actually use the modified SHA-1 algorithm. [SHA] actually use the modified SHA-1 algorithm. [SHA]
SSL SSL
Netscape's Secure Socket Layer protocol [SSL3]. TLS is based on Netscape's Secure Socket Layer protocol [SSL3]. TLS is based on
SSL Version 3.0 SSL Version 3.0
stream cipher stream cipher
An encryption algorithm that converts a key into a An encryption algorithm that converts a key into a
cryptographically-strong keystream, which is then exclusive-ORed cryptographically-strong keystream, which is then exclusive-ORed
with the plaintext. with the plaintext.
symmetric cipher symmetric cipher
See bulk cipher. See bulk cipher.
] Transport Layer Security (TLS) Transport Layer Security (TLS)
] This protocol; also, the Transport Layer Security working group This protocol; also, the Transport Layer Security working group
] of the Internet Engineering Task Force (IETF). See "Comments" at of the Internet Engineering Task Force (IETF). See "Comments" at
] the end of this document. the end of this document.
C. CipherSuite definitions C. CipherSuite definitions
CipherSuite Is Key Cipher Hash CipherSuite Is Key Cipher Hash
Exportable Exchange Exportable Exchange
TLS_NULL_WITH_NULL_NULL * NULL NULL NULL TLS_NULL_WITH_NULL_NULL * NULL NULL NULL
TLS_RSA_WITH_NULL_MD5 * RSA NULL MD5 TLS_RSA_WITH_NULL_MD5 * RSA NULL MD5
TLS_RSA_WITH_NULL_SHA * RSA NULL SHA TLS_RSA_WITH_NULL_SHA * RSA NULL SHA
TLS_RSA_EXPORT_WITH_RC4_40_MD5 * RSA_EXPORT RC4_40 MD5 TLS_RSA_EXPORT_WITH_RC4_40_MD5 * RSA_EXPORT RC4_40 MD5
TLS_RSA_WITH_RC4_128_MD5 RSA RC4_128 MD5 TLS_RSA_WITH_RC4_128_MD5 RSA RC4_128 MD5
TLS_RSA_WITH_RC4_128_SHA RSA RC4_128 SHA TLS_RSA_WITH_RC4_128_SHA RSA RC4_128 SHA
TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5 * RSA_EXPORT RC2_CBC_40 MD5 TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5 * RSA_EXPORT RC2_CBC_40 MD5
TLS_RSA_WITH_IDEA_CBC_SHA RSA IDEA_CBC SHA TLS_RSA_WITH_IDEA_CBC_SHA RSA IDEA_CBC SHA
TLS_RSA_EXPORT_WITH_DES40_CBC_SHA * RSA_EXPORT DES40_CBC SHA TLS_RSA_EXPORT_WITH_DES40_CBC_SHA * RSA_EXPORT DES40_CBC SHA
TLS_RSA_WITH_DES_CBC_SHA RSA DES_CBC SHA TLS_RSA_WITH_DES_CBC_SHA RSA DES_CBC SHA
TLS_RSA_WITH_3DES_EDE_CBC_SHA RSA 3DES_EDE_CBC SHA TLS_RSA_WITH_3DES_EDE_CBC_SHA RSA 3DES_EDE_CBC SHA
TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA * DH_DSS_EXPORT DES40_CBC SHA TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA * DH_DSS_EXPORT DES40_CBC SHA
TLS_DH_DSS_WITH_DES_CBC_SHA DH_DSS DES_CBC SHA TLS_DH_DSS_WITH_DES_CBC_SHA DH_DSS DES_CBC SHA
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IDEA_CBC Block 16 16 128 8 8 IDEA_CBC Block 16 16 128 8 8
RC2_CBC_40 * Block 5 16 40 8 8 RC2_CBC_40 * Block 5 16 40 8 8
RC4_40 * Stream 5 16 40 0 N/A RC4_40 * Stream 5 16 40 0 N/A
RC4_128 Stream 16 16 128 0 N/A RC4_128 Stream 16 16 128 0 N/A
DES40_CBC * Block 5 8 40 8 8 DES40_CBC * Block 5 8 40 8 8
DES_CBC Block 8 8 56 8 8 DES_CBC Block 8 8 56 8 8
3DES_EDE_CBC Block 24 24 168 8 8 3DES_EDE_CBC Block 24 24 168 8 8
* Indicates IsExportable is true. * Indicates IsExportable is true.
| Type Type
| Indicates whether this is a stream cipher or a block cipher Indicates whether this is a stream cipher or a block cipher
| running in CBC mode. running in CBC mode.
Key Material Key Material
The number of bytes from the key_block that are used for The number of bytes from the key_block that are used for
generating the write keys. generating the write keys.
Expanded Key Material Expanded Key Material
The number of bytes actually fed into the encryption algorithm The number of bytes actually fed into the encryption algorithm
Effective Key Bits Effective Key Bits
How much entropy material is in the key material being fed into How much entropy material is in the key material being fed into
the encryption routines. the encryption routines.
| IV Size IV Size
| How much data needs to be generated for the initialization How much data needs to be generated for the initialization
| vector. Zero for stream ciphers; equal to the block size for vector. Zero for stream ciphers; equal to the block size for
| block ciphers. block ciphers.
| Block Size Block Size
| The amount of data a block cipher enciphers in one chunk; a The amount of data a block cipher enciphers in one chunk; a
| block cipher running in CBC mode can only encrypt an even block cipher running in CBC mode can only encrypt an even
| multiple of its block size. multiple of its block size.
Hash Hash Padding Hash Hash Padding
function Size Size function Size Size
NULL 0 0 NULL 0 0
MD5 16 48 MD5 16 48
SHA 20 40 SHA 20 40
Appendix D Appendix D
D. Implementation Notes D. Implementation Notes
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of the counter value is 16 bits or more. To seed a 128-bit PRNG, one of the counter value is 16 bits or more. To seed a 128-bit PRNG, one
would thus require approximately 100 such timer values. would thus require approximately 100 such timer values.
Warning: The seeding functions in RSAREF and versions of BSAFE prior to Warning: The seeding functions in RSAREF and versions of BSAFE prior to
3.0 are order-independent. For example, if 1000 seed bits are 3.0 are order-independent. For example, if 1000 seed bits are
supplied, one at a time, in 1000 separate calls to the seed supplied, one at a time, in 1000 separate calls to the seed
function, the PRNG will end up in a state which depends only function, the PRNG will end up in a state which depends only
on the number of 0 or 1 seed bits in the seed data (i.e., on the number of 0 or 1 seed bits in the seed data (i.e.,
there are 1001 possible final states). Applications using there are 1001 possible final states). Applications using
BSAFE or RSAREF must take extra care to ensure proper seeding. BSAFE or RSAREF must take extra care to ensure proper seeding.
] This may be accomplished by accumulating seed bits into a This may be accomplished by accumulating seed bits into a
] buffer and processing them all at once or by processing an buffer and processing them all at once or by processing an
incrementing counter with every seed bit; either method will
] incrementing counter with every seed bit; either method will reintroduce order dependence into the seeding process.
] reintroduce order dependence into the seeding process.
D.3. Certificates and authentication D.3. Certificates and authentication
Implementations are responsible for verifying the integrity of Implementations are responsible for verifying the integrity of
certificates and should generally support certificate revocation certificates and should generally support certificate revocation
messages. Certificates should always be verified to ensure proper messages. Certificates should always be verified to ensure proper
signing by a trusted Certificate Authority (CA). The selection and signing by a trusted Certificate Authority (CA). The selection and
addition of trusted CAs should be done very carefully. Users should addition of trusted CAs should be done very carefully. Users should
be able to view information about the certificate and root CA. be able to view information about the certificate and root CA.
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encryption is easily broken, so implementations requiring strong encryption is easily broken, so implementations requiring strong
security should not allow 40-bit keys. Similarly, anonymous security should not allow 40-bit keys. Similarly, anonymous
Diffie-Hellman is strongly discouraged because it cannot prevent Diffie-Hellman is strongly discouraged because it cannot prevent
man-in-the-middle attacks. Applications should also enforce minimum man-in-the-middle attacks. Applications should also enforce minimum
and maximum key sizes. For example, certificate chains containing and maximum key sizes. For example, certificate chains containing
512-bit RSA keys or signatures are not appropriate for high-security 512-bit RSA keys or signatures are not appropriate for high-security
applications. applications.
E. Backward Compatibility With SSL E. Backward Compatibility With SSL
] For historical reasons and in order to avoid a profligate For historical reasons and in order to avoid a profligate
] consumption of reserved port numbers, application protocols which consumption of reserved port numbers, application protocols which
] are secured by TLS 1.0, SSL 3.0, and SSL 2.0 all frequently share are secured by TLS 1.0, SSL 3.0, and SSL 2.0 all frequently share
] the same connection port: for example, the https protocol (HTTP the same connection port: for example, the https protocol (HTTP
] secured by SSL or TLS) uses port 443 regardless of which security secured by SSL or TLS) uses port 443 regardless of which security
] protocol it is using. Thus, some mechanism must be determined to protocol it is using. Thus, some mechanism must be determined to
] distinguish and negotiate among the various protocols. distinguish and negotiate among the various protocols.
] TLS version 1.0 and SSL 3.0 are very similar; thus, supporting both TLS version 1.0 and SSL 3.0 are very similar; thus, supporting both
] is easy. TLS clients who wish to negotiate with SSL 3.0 servers is easy. TLS clients who wish to negotiate with SSL 3.0 servers
] should send client hello messages using the SSL 3.0 record format should send client hello messages using the SSL 3.0 record format
] and client hello structure, sending {3, 1} for the version field to and client hello structure, sending {3, 1} for the version field to
] note that they support TLS 1.0. If the server supports only SSL 3.0, note that they support TLS 1.0. If the server supports only SSL 3.0,
] it will respond with an SSL 3.0 server hello; if it supports TLS, it will respond with an SSL 3.0 server hello; if it supports TLS,
] with a TLS server hello. The negotiation then proceeds as with a TLS server hello. The negotiation then proceeds as
] appropriate for the negotiated protocol. appropriate for the negotiated protocol.
] Similarly, a TLS server which wishes to interoperate with SSL 3.0 Similarly, a TLS server which wishes to interoperate with SSL 3.0
] clients should accept SSL 3.0 client hello messages and respond with clients should accept SSL 3.0 client hello messages and respond with
] an SSL 3.0 server hello if an SSL 3.0 client hello is received which an SSL 3.0 server hello if an SSL 3.0 client hello is received which
] has a version field of {3, 0}, denoting that this client does not has a version field of {3, 0}, denoting that this client does not
] support TLS. support TLS.
] Whenever a client already knows the highest protocol known to a Whenever a client already knows the highest protocol known to a
] server (for example, when resuming a session), it should initiate server (for example, when resuming a session), it should initiate
] the connection in that native protocol. the connection in that native protocol.
] TLS 1.0 clients that support SSL Version 2.0 servers must send SSL TLS 1.0 clients that support SSL Version 2.0 servers must send SSL
] Version 2.0 client hello messages [SSL2]. TLS servers should accept Version 2.0 client hello messages [SSL2]. TLS servers should accept
] either client hello format if they wish to support SSL 2.0 clients either client hello format if they wish to support SSL 2.0 clients
] on the same connection port. The only deviations from the Version on the same connection port. The only deviations from the Version
] 2.0 specification are the ability to specify a version with a value 2.0 specification are the ability to specify a version with a value
] of three and the support for more ciphering types in the CipherSpec. of three and the support for more ciphering types in the CipherSpec.
Warning: The ability to send Version 2.0 client hello messages will be Warning: The ability to send Version 2.0 client hello messages will be
phased out with all due haste. Implementors should make every phased out with all due haste. Implementors should make every
effort to move forward as quickly as possible. Version 3.0 effort to move forward as quickly as possible. Version 3.0
provides better mechanisms for moving to newer versions. provides better mechanisms for moving to newer versions.
The following cipher specifications are carryovers from SSL Version The following cipher specifications are carryovers from SSL Version
2.0. These are assumed to use RSA for key exchange and 2.0. These are assumed to use RSA for key exchange and
authentication. authentication.
skipping to change at page 62, line 43 skipping to change at page 62, line 23
generating a Master Secret, which together comprise the primary generating a Master Secret, which together comprise the primary
cryptographic parameters associated with a secure session. The cryptographic parameters associated with a secure session. The
handshake protocol can also optionally authenticate parties who have handshake protocol can also optionally authenticate parties who have
certificates signed by a trusted certificate authority. certificates signed by a trusted certificate authority.
F.1.1. Authentication and key exchange F.1.1. Authentication and key exchange
TLS supports three authentication modes: authentication of both TLS supports three authentication modes: authentication of both
parties, server authentication with an unauthenticated client, and parties, server authentication with an unauthenticated client, and
total anonymity. Whenever the server is authenticated, the channel total anonymity. Whenever the server is authenticated, the channel
should be secure against man-in-the-middle attacks, but completely is secure against man-in-the-middle attacks, but completely
anonymous sessions are inherently vulnerable to such attacks. anonymous sessions are inherently vulnerable to such attacks.
| Anonymous servers cannot authenticate clients. If the server is Anonymous servers cannot authenticate clients. If the server is
authenticated, its certificate message must provide a valid authenticated, its certificate message must provide a valid
certificate chain leading to an acceptable certificate authority. certificate chain leading to an acceptable certificate authority.
Similarly, authenticated clients must supply an acceptable Similarly, authenticated clients must supply an acceptable
certificate to the server. Each party is responsible for verifying certificate to the server. Each party is responsible for verifying
that the other's certificate is valid and has not expired or been that the other's certificate is valid and has not expired or been
revoked. revoked.
The general goal of the key exchange process is to create a The general goal of the key exchange process is to create a
pre_master_secret known to the communicating parties and not to pre_master_secret known to the communicating parties and not to
attackers. The pre_master_secret will be used to generate the attackers. The pre_master_secret will be used to generate the
skipping to change at page 66, line 48 skipping to change at page 66, line 30
Appendix G Appendix G
G. Patent Statement G. Patent Statement
This version of the TLS protocol relies on the use of patented This version of the TLS protocol relies on the use of patented
public key encryption technology for authentication and encryption. public key encryption technology for authentication and encryption.
The Internet Standards Process as defined in RFC 1310 requires a The Internet Standards Process as defined in RFC 1310 requires a
written statement from the Patent holder that a license will be made written statement from the Patent holder that a license will be made
available to applicants under reasonable terms and conditions prior available to applicants under reasonable terms and conditions prior
to approving a specification as a Proposed, Draft or Internet to approving a specification as a Proposed, Draft or Internet
Standard. The Massachusetts Institute of Technology has granted RSA Standard.
Data Security, Inc., exclusive sub-licensing rights to the following
The Massachusetts Institute of Technology has granted RSA Data
Security, Inc., exclusive sub-licensing rights to the following
patent issued in the United States: patent issued in the United States:
Cryptographic Communications System and Method ("RSA"), No. Cryptographic Communications System and Method ("RSA"), No.
4,405,829 4,405,829
The Board of Trustees of the Leland Stanford Junior University have
granted Caro-Kann Corporation, a wholly owned subsidiary
corporation, exclusive sub-licensing rights to the following patents
issued in the United States, and all of their corresponding foreign
patents:
Cryptographic Apparatus and Method ("Diffie-Hellman"), No. Netscape Communications Corporation has been issued the following
4,200,770 patent in the United States:
Public Key Cryptographic Apparatus and Method Secure Socket Layer Application Program Apparatus And Method
("Hellman-Merkle"), No. 4,218,582 ("SSL"), No. 5,657,390
Netscape Communications has issued the following statement:
Intellectual Property Rights
Secure Sockets Layer
The United States Patent and Trademark Office ("the PTO")
recently issued U.S. Patent No. 5,657,390 ("the SSL Patent") to
Netscape for inventions described as Secure Sockets Layers
("SSL"). The IETF is currently considering adopting SSL as a
transport protocol with security features. Netscape encourages
the royalty-free adoption and use of the SSL protocol upon the
following terms and conditions:
* If you already have a valid SSL Ref license today which
includes source code from Netscape, an additional patent
license under the SSL patent is not required.
* If you don't have an SSL Ref license, you may have a royalty
free license to build implementations covered by the SSL
Patent Claims or the IETF TLS specification provided that
you do not to assert any patent rights against Netscape or
other companies for the implementation of SSL or the IETF
TLS recommendation.
What are "Patent Claims":
Patent claims are claims in an issued foreign or domestic patent
that:
1) must be infringed in order to implement methods or build
products according to the IETF TLS specification; or
2) patent claims which require the elements of the SSL patent
claims and/or their equivalents to be infringed.
The Internet Society, Internet Architecture Board, Internet The Internet Society, Internet Architecture Board, Internet
Engineering Steering Group and the Corporation for National Research Engineering Steering Group and the Corporation for National Research
Initiatives take no position on the validity or scope of the patents Initiatives take no position on the validity or scope of the patents
and patent applications, nor on the appropriateness of the terms of and patent applications, nor on the appropriateness of the terms of
the assurance. The Internet Society and other groups mentioned above the assurance. The Internet Society and other groups mentioned above
have not made any determination as to any other intellectual have not made any determination as to any other intellectual
property rights which may apply to the practice of this standard. property rights which may apply to the practice of this standard.
Any further consideration of these matters is the user's own Any further consideration of these matters is the user's own
responsibility. responsibility.
skipping to change at page 67, line 41 skipping to change at page 67, line 53
[DES] ANSI X3.106, "American National Standard for Information [DES] ANSI X3.106, "American National Standard for Information
Systems-Data Link Encryption," American National Standards Systems-Data Link Encryption," American National Standards
Institute, 1983. Institute, 1983.
[DH1] W. Diffie and M. E. Hellman, "New Directions in Cryptography," [DH1] W. Diffie and M. E. Hellman, "New Directions in Cryptography,"
IEEE Transactions on Information Theory, V. IT-22, n. 6, Jun 1977, IEEE Transactions on Information Theory, V. IT-22, n. 6, Jun 1977,
pp. 74-84. pp. 74-84.
[DSS] NIST FIPS PUB 186, "Digital Signature Standard," National [DSS] NIST FIPS PUB 186, "Digital Signature Standard," National
Institute of Standards and Technology, U.S. Department of Commerce, Institute of Standards and Technology, U.S. Department of Commerce,
18 May 1994. May 18, 1994.
[FTP] J. Postel and J. Reynolds, RFC 959: File Transfer Protocol, [FTP] J. Postel and J. Reynolds, RFC 959: File Transfer Protocol,
October 1985. October 1985.
[HTTP] T. Berners-Lee, R. Fielding, H. Frystyk, Hypertext Transfer [HTTP] T. Berners-Lee, R. Fielding, H. Frystyk, Hypertext Transfer
Protocol -- HTTP/1.0, October, 1995. Protocol -- HTTP/1.0, October, 1995.
| [HMAC] H. Krawczyk, M. Bellare, and R. Canetti, RFC 2104, HMAC: [HMAC] H. Krawczyk, M. Bellare, and R. Canetti, RFC 2104, HMAC:
| Keyed-Hashing for Message Authentication, February, 1997. Keyed-Hashing for Message Authentication, February, 1997.
[IDEA] X. Lai, "On the Design and Security of Block Ciphers," ETH [IDEA] X. Lai, "On the Design and Security of Block Ciphers," ETH
Series in Information Processing, v. 1, Konstanz: Hartung-Gorre Series in Information Processing, v. 1, Konstanz: Hartung-Gorre
Verlag, 1992. Verlag, 1992.
[MD2] R. Rivest. RFC 1319: The MD2 Message Digest Algorithm. April [MD2] R. Rivest. RFC 1319: The MD2 Message Digest Algorithm. April
1992. 1992.
[MD5] R. Rivest. RFC 1321: The MD5 Message Digest Algorithm. April [MD5] R. Rivest. RFC 1321: The MD5 Message Digest Algorithm. April
1992. 1992.
[PKCS1] RSA Laboratories, "PKCS #1: RSA Encryption Standard," [PKCS1] RSA Laboratories, "PKCS #1: RSA Encryption Standard,"
version 1.5, November 1993. version 1.5, November 1993.
[PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate Syntax [PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate Syntax
Standard," version 1.5, November 1993. Standard," version 1.5, November 1993.
[PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message Syntax [PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message Syntax
Standard," version 1.5, November 1993. Standard," version 1.5, November 1993.
] [PKIX] R. Housley, W. Ford, W. Polk, D. Solo, Internet Public Key [PKIX] R. Housley, W. Ford, W. Polk, D. Solo, Internet Public Key
] Infrastructure: Part I: X.509 Certificate and CRL Profile, Infrastructure: Part I: X.509 Certificate and CRL Profile,
] <draft-ietf-pkix-ipki-part1-03.txt>, December 1996. <draft-ietf-pkix-ipki-part1-06.txt>, October 1997.
| [RC4] R. Thayer, A Stream Cipher Encryption Algorithm, [RC2] R. Rivest, A Description of the RC2(r) Encryption Algorithm
| <draft-thayer-cipher-00.txt>, February 1997. <draft-rivest-rc2desc-00.txt>
[RC4] R. Thayer and K. Kaukonen, A Stream Cipher Encryption
Algorithm, <draft-kaukonen-cipher-arcfour-01.txt>, July 1997.
[RSA] R. Rivest, A. Shamir, and L. M. Adleman, "A Method for [RSA] R. Rivest, A. Shamir, and L. M. Adleman, "A Method for
Obtaining Digital Signatures and Public-Key Cryptosystems," Obtaining Digital Signatures and Public-Key Cryptosystems,"
Communications of the ACM, v. 21, n. 2, Feb 1978, pp. 120-126. Communications of the ACM, v. 21, n. 2, Feb 1978, pp. 120-126.
[RSADSI] Contact RSA Data Security, Inc., Tel: 415-595-8782 [SCH] B. [RSADSI] Contact RSA Data Security, Inc., Tel: 415-595-8782 [SCH] B.
Schneier. Applied Cryptography: Protocols, Algorithms, and Source Schneier. Applied Cryptography: Protocols, Algorithms, and Source
Code in C, Published by John Wiley & Sons, Inc. 1994. Code in C, Published by John Wiley & Sons, Inc. 1994.
[SHA] NIST FIPS PUB 180-1, "Secure Hash Standard," National [SHA] NIST FIPS PUB 180-1, "Secure Hash Standard," National
Institute of Standards and Technology, U.S. Department of Commerce, Institute of Standards and Technology, U.S. Department of Commerce,
DRAFT, 31 May 1994. DRAFT, May 31, 1994.
| [SSL2] Hickman, Kipp, "The SSL Protocol", Netscape Communications [SSL2] Hickman, Kipp, "The SSL Protocol", Netscape Communications
| Corp., Feb 9th, 1995. Corp., Feb 9, 1995.
[SSL3] Frier, Karton and Kocher, [SSL3] A. Frier, P. Karlton, and P. Kocher, "The SSL 3.0 Protocol",
internet-draft-tls-ssl-version3-00.txt: "The SSL 3.0 Protocol", Nov Netscape Communications Corp., Nov 18, 1996.
18 1996.
[TCP] ISI for DARPA, RFC 793: Transport Control Protocol, September [TCP] ISI for DARPA, RFC 793: Transport Control Protocol, September
1981. 1981.
[TEL] J. Postel and J. Reynolds, RFC 854/5, May, 1993. [TEL] J. Postel and J. Reynolds, RFC 854/5, May, 1993.
[X509] CCITT. Recommendation X.509: "The Directory - Authentication [X509] CCITT. Recommendation X.509: "The Directory - Authentication
Framework". 1988. Framework". 1988.
[XDR] R. Srinivansan, Sun Microsystems, RFC-1832: XDR: External Data [XDR] R. Srinivansan, Sun Microsystems, RFC-1832: XDR: External Data
Representation Standard, August 1995. Representation Standard, August 1995.
Credits Credits
Working Group Chair Working Group Chair
Win Treese Win Treese
Open Market Open Market
| treese@openmarket.com treese@openmarket.com
Editors Editors
Christopher Allen Tim Dierks Christopher Allen Tim Dierks
Consensus Development Consensus Development Consensus Development Consensus Development
christophera@consensus.com timd@consensus.com christophera@consensus.com timd@consensus.com
Authors Authors
Tim Dierks Philip L. Karlton Tim Dierks Philip L. Karlton
skipping to change at page 69, line 35 skipping to change at page 70, line 35
Alan O. Freier Paul C. Kocher Alan O. Freier Paul C. Kocher
Netscape Communications Independent Consultant Netscape Communications Independent Consultant
freier@netscape.com pck@netcom.com freier@netscape.com pck@netcom.com
Other contributors Other contributors
Martin Abadi Robert Relyea Martin Abadi Robert Relyea
Digital Equipment Corporation Netscape Communications Digital Equipment Corporation Netscape Communications
ma@pa.dec.com relyea@netscape.com ma@pa.dec.com relyea@netscape.com
| Ran Canetti Jim Roskind Ran Canetti Jim Roskind
| IBM Watson Research Center Netscape Communications IBM Watson Research Center Netscape Communications
| canetti@watson.ibm.com jar@netscape.com canetti@watson.ibm.com jar@netscape.com
Taher Elgamal Micheal J. Sabin, Ph. D. Taher Elgamal Micheal J. Sabin, Ph. D.
Netscape Communications Consulting Engineer Netscape Communications Consulting Engineer
elgamal@netscape.com msabin@netcom.com elgamal@netscape.com msabin@netcom.com
| Anil Gangolli Dan Simon Anil Gangolli Dan Simon
| Netscape Communications Microsoft Netscape Communications Microsoft
| gangolli@netscape.com dansimon@microsoft.com gangolli@netscape.com dansimon@microsoft.com
Kipp E.B. Hickman Tom Weinstein Kipp E.B. Hickman Tom Weinstein
Netscape Communications Netscape Communications Netscape Communications Netscape Communications
kipp@netscape.com tomw@netscape.com kipp@netscape.com tomw@netscape.com
| Hugo Krawczyk Hugo Krawczyk
| IBM Watson Research Center IBM Watson Research Center
| hugo@watson.ibm.com hugo@watson.ibm.com
Comments Comments
] Comments on this draft should be sent to the editors, Tim Dierks and Comments on this draft should be sent to the editors, Tim Dierks and
] Christopher Allen at the address <ietf-tls-editors@consensus.com>, Christopher Allen at the address <ietf-tls-editors@consensus.com>,
] or to the IETF Transport Layer Security (TLS) Working Group. or to the IETF Transport Layer Security (TLS) Working Group.
] The discussion list for the IETF TLS working group is located at the The discussion list for the IETF TLS working group is located at the
] e-mail address <ietf-tls@consensus.com>. Information on the group e-mail address <ietf-tls@consensus.com>. Information on the group
] and information on how to subscribe to the list is at and information on how to subscribe to the list is at
] <http://www.consensus.com/ietf-tls/>. <http://www.consensus.com/ietf-tls/>.
] You can subscribe to the list by sending a message to You can subscribe to the list by sending a message to
] <ietf-tls@consensus.com> with the subject "SUBSCRIBE". You can <ietf-tls@consensus.com> with the subject "SUBSCRIBE". You can
] subscribe to a digested variant of the list by sending a message to subscribe to a digested variant of the list by sending a message to
] <ietf-tls@consensus.com> with the subject "SUBSCRIBE DIGEST". To <ietf-tls@consensus.com> with the subject "SUBSCRIBE DIGEST". To
] remove yourself from the list, send a message to remove yourself from the list, send a message to
] <ietf-tls@consensus.com> with the subject "UNSUBSCRIBE". <ietf-tls@consensus.com> with the subject "UNSUBSCRIBE".
Archives of the list are at: Archives of the list are at:
] <http://www.imc.org/ietf-tls/mail-archive/> <http://www.imc.org/ietf-tls/mail-archive/>
 End of changes. 

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