draft-ietf-tls-oob-pubkey-06.txt   draft-ietf-tls-oob-pubkey-07.txt 
TLS P. Wouters, Ed. TLS P. Wouters, Ed.
Internet-Draft Red Hat Internet-Draft Red Hat
Intended status: Standards Track H. Tschofenig, Ed. Intended status: Standards Track H. Tschofenig, Ed.
Expires: April 25, 2013 Nokia Siemens Networks Expires: August 19, 2013 Nokia Siemens Networks
J. Gilmore J. Gilmore
S. Weiler S. Weiler
SPARTA, Inc. SPARTA, Inc.
T. Kivinen T. Kivinen
AuthenTec AuthenTec
October 22, 2012 February 15, 2013
Out-of-Band Public Key Validation for Transport Layer Security (TLS) Out-of-Band Public Key Validation for Transport Layer Security (TLS)
draft-ietf-tls-oob-pubkey-06.txt draft-ietf-tls-oob-pubkey-07.txt
Abstract Abstract
This document specifies a new certificate type for exchanging raw This document specifies a new certificate type for exchanging raw
public keys in Transport Layer Security (TLS) and Datagram Transport public keys in Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS) for use with out-of-band public key validation. Layer Security (DTLS) for use with out-of-band public key validation.
Currently, TLS authentication can only occur via X.509-based Public Currently, TLS authentication can only occur via X.509-based Public
Key Infrastructure (PKI) or OpenPGP certificates. By specifying a Key Infrastructure (PKI) or OpenPGP certificates. By specifying a
minimum resource for raw public key exchange, implementations can use minimum resource for raw public key exchange, implementations can use
alternative public key validation methods. alternative public key validation methods.
skipping to change at page 2, line 6 skipping to change at page 2, line 6
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 25, 2013. This Internet-Draft will expire on August 19, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. New TLS Extension . . . . . . . . . . . . . . . . . . . . . . 4 3. New TLS Extension . . . . . . . . . . . . . . . . . . . . . . 5
4. TLS Handshake Extension . . . . . . . . . . . . . . . . . . . 7 4. TLS Handshake Extension . . . . . . . . . . . . . . . . . . . 8
4.1. Client Hello . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Client Hello . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Server Hello . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Server Hello . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Certificate Request . . . . . . . . . . . . . . . . . . . 8 4.3. Certificate Request . . . . . . . . . . . . . . . . . . . 9
4.4. Other Handshake Messages . . . . . . . . . . . . . . . . . 8 4.4. Other Handshake Messages . . . . . . . . . . . . . . . . . 9
4.5. Client authentication . . . . . . . . . . . . . . . . . . 8 4.5. Client authentication . . . . . . . . . . . . . . . . . . 9
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 13 9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Appendix A. Example Encoding . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
Traditionally, TLS server public keys are obtained in PKIX containers Traditionally, TLS server public keys are obtained in PKIX containers
in-band using the TLS handshake and validated using trust anchors in-band using the TLS handshake and validated using trust anchors
based on a [PKIX] certification authority (CA). This method can add based on a [PKIX] certification authority (CA). This method can add
a complicated trust relationship that is difficult to validate. a complicated trust relationship that is difficult to validate.
Examples of such complexity can be seen in [Defeating-SSL]. Examples of such complexity can be seen in [Defeating-SSL].
Alternative methods are available that allow a TLS client to obtain Alternative methods are available that allow a TLS client to obtain
skipping to change at page 4, line 39 skipping to change at page 4, line 39
CoAP [I-D.ietf-core-coap] can utilize DTLS for securing the client- CoAP [I-D.ietf-core-coap] can utilize DTLS for securing the client-
to-server communication. As part of the manufacturing process, the to-server communication. As part of the manufacturing process, the
embeded device may be configured with the address and the public key embeded device may be configured with the address and the public key
of a dedicated CoAP server, as well as a public key for the client of a dedicated CoAP server, as well as a public key for the client
itself. The usage of X.509-based PKIX certificates [PKIX] may not itself. The usage of X.509-based PKIX certificates [PKIX] may not
suit all smart object deployments and would therefore be an suit all smart object deployments and would therefore be an
unneccesarry burden. unneccesarry burden.
The Transport Layer Security (TLS) Protocol Version 1.2 [RFC5246] The Transport Layer Security (TLS) Protocol Version 1.2 [RFC5246]
provides a framework for extensions to TLS as well as guidelines for provides a framework for extensions to TLS as well as guidelines for
designing such extensions. This document defines an extension to designing such extensions. This document registers a new value to
indicate the support for raw public keys. the IANA certificate types registry for the support of raw public
keys.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
3. New TLS Extension 3. New TLS Extension
This section describes the changes to the TLS handshake message This section describes the changes to the TLS handshake message
contents when raw public key certificates are to be used. Figure 3 contents when raw public key certificates are to be used. Figure 4
illustrates the exchange of messages as described in the sub-sections illustrates the exchange of messages as described in the sub-sections
below. The client and the server exchange the newly defined below. The client and the server exchange make use of two new TLS
certificate_type extension to indicate their ability and desire to extensions, namely 'client_certificate_type' and
exchange raw public keys. These raw public keys, in the form of a 'server_certificate_type', and an already available IANA TLS
SubjectPublicKeyInfo structure, are then carried inside the Certificate Type registry [TLS-Certificate-Types-Registry] to
certificate payload. The SubjectPublicKeyInfo structure is defined indicate their ability and desire to exchange raw public keys. These
in Section 4.1 of RFC 5280. Note that the SubjectPublicKeyInfo block raw public keys, in the form of a SubjectPublicKeyInfo structure, are
does not only contain the raw keys, such as the public exponent and then carried inside the Certificate payload. The Certificate and the
the modulus of an RSA public key, but also an algorithm identifier. SubjectPublicKeyInfo structure is shown in Figure 1.
The structure, as shown in Figure 1, is encoded in an ASN.1 format
and therefore contains length information as well. opaque ASN.1Cert<1..2^24-1>;
struct {
select(certificate_type){
// certificate type defined in this document.
case RawPublicKey:
opaque ASN.1_subjectPublicKeyInfo<1..2^24-1>;
// X.509 certificate defined in RFC 5246
case X.509:
ASN.1Cert certificate_list<0..2^24-1>;
// Additional certificate type based on TLS
// Certificate Type Registry
};
} Certificate;
Figure 1: TLS Certificate Structure.
The SubjectPublicKeyInfo structure is defined in Section 4.1 of RFC
5280 [PKIX] and does not only contain the raw keys, such as the
public exponent and the modulus of an RSA public key, but also an
algorithm identifier. The structure, as shown in Figure 2, is
encoded in an ASN.1 format and therefore contains length information
as well. An example is provided in Appendix A.
SubjectPublicKeyInfo ::= SEQUENCE { SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier, algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING } subjectPublicKey BIT STRING }
Figure 1: SubjectPublicKeyInfo ASN.1 Structure. Figure 2: SubjectPublicKeyInfo ASN.1 Structure.
The algorithm identifiers are Object Identifiers (OIDs). RFC 3279 The algorithm identifiers are Object Identifiers (OIDs). RFC 3279
[RFC3279], for example, defines the following OIDs shown in Figure 2. [RFC3279], for example, defines the following OIDs shown in Figure 3.
Key Type | Document | OID Key Type | Document | OID
-----------------------+----------------------------+------------------- -----------------------+----------------------------+-------------------
RSA | Section 2.3.1 of RFC 3279 | 1.2.840.113549.1.1 RSA | Section 2.3.1 of RFC 3279 | 1.2.840.113549.1.1
.......................|............................|................... .......................|............................|...................
Digital Signature | | Digital Signature | |
Algorithm (DSS) | Section 2.3.2 of RFC 3279 | 1.2.840.10040.4.1 Algorithm (DSS) | Section 2.3.2 of RFC 3279 | 1.2.840.10040.4.1
.......................|............................|................... .......................|............................|...................
Elliptic Curve | | Elliptic Curve | |
Digital Signature | | Digital Signature | |
Algorithm (ECDSA) | Section 2.3.5 of RFC 3279 | 1.2.840.10045.2.1 Algorithm (ECDSA) | Section 2.3.5 of RFC 3279 | 1.2.840.10045.2.1
-----------------------+----------------------------+------------------- -----------------------+----------------------------+-------------------
Figure 2: Example Algorithm Identifiers. Figure 3: Example Algorithm Identifiers.
The message exchange in Figure 4 shows the 'client_certificate_type'
and 'server_certificate_type' extensions added to the client and
server hello messages.
client_hello, client_hello,
certificate_type -> client_certificate_type
server_certificate_type ->
<- server_hello, <- server_hello,
certificate_type, client_certificate_type,
server_certificate_type,
certificate, certificate,
server_key_exchange, server_key_exchange,
certificate_request, certificate_request,
server_hello_done server_hello_done
certificate, certificate,
client_key_exchange, client_key_exchange,
certificate_verify, certificate_verify,
change_cipher_spec, change_cipher_spec,
finished -> finished ->
<- change_cipher_spec, <- change_cipher_spec,
finished finished
Application Data <-------> Application Data Application Data <-------> Application Data
Figure 3: Basic Raw Public Key TLS Exchange. Figure 4: Basic Raw Public Key TLS Exchange.
The "certificate_type" TLS extension carries a list of supported
certificate types the client can send and receive, sorted by client
preference. Two values are defined for each certificate types to
differentiate whether a client or a server is able to process a
certificate of a specific type or can also send it. This extension
MUST be omitted if the client only supports X.509 certificates. The
"extension_data" field of this extension contains a CertTypeExtension
structure.
Note that the CertTypeExtension structure is being used both by the The semantic of the two extensions is defined as follows:
client and the server, even though the structure is only specified
once in this document.
The structure of the CertTypeExtension is defined as follows: The 'client_certificate_type' and 'server_certificate_type' sent
in the client hello, may carry a list of supported certificate
types, sorted by client preference. It is a list in the case
where the client supports multiple certificate types. These
extension MUST be omitted if the client only supports X.509
certificates. The 'client_certificate_type' sent in the client
hello indicates the certificate types the client is able to
provide to the server, when requested using a certificate_request
message. The 'server_certificate_type' in the client hello
indicates the type of certificates the client is able to process
when provided by the server in a subsequent certificate payload.
enum { client, server } ClientOrServerExtension; The 'client_certificate_type' returned in the server hello
indicates the certificate type found in the attached certificate
payload. Only a single value is permitted. The
'server_certificate_type' in the server hello indicates the type
of certificates the client is requested to provide in a subsequent
certificate payload. The value conveyed in the
'server_certificate_type' MUST be selected from one of the values
provided in the 'server_certificate_type' sent in the client
hello. If the server does not send a certificate_request payload
or none of the certificates supported by the client (as indicated
in the 'server_certificate_type' in the client hello) match the
server-supported certificate types the 'server_certificate_type'
payload sent in the server hello is omitted.
enum { X.509-Accept (0), The "extension_data" field of this extension contains the
X.509-Offer (1), ClientCertTypeExtension or the ServerCertTypeExtension structure, as
RawPublicKey-Accept (2), shown in Figure 5. The CertificateType structure is an enum with
RawPublicKey-Offer (3), with values from TLS Certificate Type Registry.
(255)
} CertificateType;
struct { struct {
select(ClientOrServerExtension) select(ClientOrServerExtension)
case client: case client:
CertificateType certificate_types<1..2^8-1>; CertificateType client_certificate_types<1..2^8-1>;
case server: case server:
CertificateType certificate_type; CertificateType client_certificate_type;
} }
} CertTypeExtension; } ClientCertTypeExtension;
Figure 4: CertTypeExtension Structure. struct {
select(ClientOrServerExtension)
case client:
CertificateType server_certificate_types<1..2^8-1>;
case server:
CertificateType server_certificate_type;
}
} ServerCertTypeExtension;
The '-Offer' postfix indicates that a TLS entity is able to send the Figure 5: CertTypeExtension Structure.
indicated certificate type to the other communication partner. The
'-Accept' postfix indicates that a TLS entity is able to receive the
indicated certificate type.
No new cipher suites are required to use raw public keys. All No new cipher suites are required to use raw public keys. All
existing cipher suites that support a key exchange method compatible existing cipher suites that support a key exchange method compatible
with the defined extension can be used. with the defined extension can be used.
4. TLS Handshake Extension 4. TLS Handshake Extension
4.1. Client Hello 4.1. Client Hello
In order to indicate the support of out-of-band raw public keys, In order to indicate the support of out-of-band raw public keys,
clients MUST include an extension of type "certificate_type" to the clients MUST include the 'client_certificate_type' and
extended client hello message. The "certificate_type" TLS extension 'server_certificate_type' extensions extended client hello message.
is assigned the value of [TBD] from the TLS ExtensionType registry. The hello extension mechanism is described in TLS 1.2 [RFC5246].
This value is used as the extension number for the extensions in both
the client hello message and the server hello message. The hello
extension mechanism is described in TLS 1.2 [RFC5246].
4.2. Server Hello 4.2. Server Hello
If the server receives a client hello that contains the If the server receives a client hello that contains the
"certificate_type" extension and chooses a cipher suite then two 'client_certificate_type' and 'server_certificate_type' extensions
outcomes are possible. The server MUST either select a certificate and chooses a cipher suite then three outcomes are possible:
type from the CertificateType field in the extended client hello or
terminate the session with a fatal alert of type
"unsupported_certificate".
The certificate type selected by the server is encoded in a 1. The server does not support the extension defined in this
CertTypeExtension structure, which is included in the extended server document. In this case the server returns the server hello
hello message using an extension of type "certificate_type". Servers without the extensions defined in this document.
that only support X.509 certificates MAY omit including the
"certificate_type" extension in the extended server hello.
If the client supports the receiption of raw public keys and the 2. The server supports the extension defined in this document and
server is able to provide such a raw public key then the TLS server has at least one certificate type in common with the client. In
this case it returns the 'server_certificate_type' and indicates
the selected certificate type value.
3. The server supports the extension defined in this document but
does not have a certificate type in common with the client. In
this case the server terminate the session with a fatal alert of
type "unsupported_certificate".
If the TLS server also requests a certificate from the client (via
the certificate_request) it MUST include the
'client_certificate_type' extension with a value chosen from the list
of client-supported certificates types (as provided in the
'client_certificate_type' of the client hello).
If the client indicated the support of raw public keys in the
'client_certificate_type' extension in the client hello and the
server is able to provide such raw public key then the TLS server
MUST place the SubjectPublicKeyInfo structure into the Certificate MUST place the SubjectPublicKeyInfo structure into the Certificate
payload. The public key MUST match the selected key exchange payload. The public key algorithm MUST match the selected key
algorithm. exchange algorithm.
4.3. Certificate Request 4.3. Certificate Request
The semantics of this message remain the same as in the TLS The semantics of this message remain the same as in the TLS
specification. specification.
4.4. Other Handshake Messages 4.4. Other Handshake Messages
All the other handshake messages are identical to the TLS All the other handshake messages are identical to the TLS
specification. specification.
4.5. Client authentication 4.5. Client authentication
Client authentication by the TLS server is supported only through Client authentication by the TLS server is supported only through
authentication of the received client SubjectPublicKeyInfo via an authentication of the received client SubjectPublicKeyInfo via an
out-of-band method out-of-band method.
5. Examples 5. Examples
Figure 5, Figure 6, and Figure 7 illustrate example exchanges. Figure 6, Figure 7, and Figure 8 illustrate example exchanges.
The first example shows an exchange where the TLS client indicates The first example shows an exchange where the TLS client indicates
its ability to receive raw public keys. This client is quite its ability to receive and validate raw public keys from the server.
restricted since it is unable to process other certificate types sent In our example the client is quite restricted since it is unable to
by the server. It also does not have credentials it could send. The process other certificate types sent by the server. It also does not
'certificate_type' extension indicates this in [1]. When the TLS have credentials (at the TLS layer) it could send. The
server receives the client hello it processes the certificate_type 'client_certificate_type' extension indicates this in [1]. When the
extension. Since it also has a raw public key it indicates in [2] TLS server receives the client hello it processes the
that it had choosen to place the SubjectPublicKeyInfo structure into 'client_certificate_type' extension. Since it also has a raw public
the Certificate payload [3]. The client uses this raw public key in key it indicates in [2] that it had choosen to place the
the TLS handshake and an out-of-band technique, such as DANE, to SubjectPublicKeyInfo structure into the Certificate payload [3]. The
verify its validity. client uses this raw public key in the TLS handshake and an out-of-
band technique, such as DANE, to verify its validity.
client_hello, client_hello,
certificate_type=(RawPublicKey-Accept) -> // [1] server_certificate_type=(RawPublicKey) -> // [1]
<- server_hello, <- server_hello,
certificate_type=(RawPublicKey-Offer), // [2] server_certificate_type=(RawPublicKey), // [2]
certificate, // [3] certificate, // [3]
server_key_exchange, server_key_exchange,
server_hello_done server_hello_done
client_key_exchange, client_key_exchange,
change_cipher_spec, change_cipher_spec,
finished -> finished ->
<- change_cipher_spec, <- change_cipher_spec,
finished finished
Application Data <-------> Application Data Application Data <-------> Application Data
Figure 5: Example with Raw Public Key provided by the TLS Server Figure 6: Example with Raw Public Key provided by the TLS Server
In our second example the TLS client as well as the TLS server use In our second example the TLS client as well as the TLS server use
raw public keys. This is a use case envisioned for smart object raw public keys. This is a use case envisioned for smart object
networking. The TLS client in this case is an embedded device that networking. The TLS client in this case is an embedded device that
is configured with a raw public key for use with TLS and is also able is configured with a raw public key for use with TLS and is also able
to process raw public keys sent by the server. Therefore, it to process raw public keys sent by the server. Therefore, it
indicates these capabilities in the 'certificate_type' extension in indicates these capabilities in [1]. As in the previously shown
[1]. As in the previously shown example the server fulfills the example the server fulfills the client's request, indicates this via
client's request, indicates this via the 'RawPublicKey-Offer'in the the "RawPublicKey" value in the server_certificate_type payload, and
certificate_type payload, and provides a raw public key into the provides a raw public key into the Certificate payload back to the
Certificate payload back to the client (see [3]). The TLS server, client (see [3]). The TLS server, however, demands client
however, demands client authentication and therefore a authentication and therefore a certificate_request is added [4]. The
certificate_request is added [4]. The certificate_type payload in certificate_type payload in [2] indicates that the TLS server accepts
[2] indicates that the TLS server accepts raw public keys. The TLS raw public keys. The TLS client, who has a raw public key pre-
client, who has a raw public key pre-provisioned, returns it in the provisioned, returns it in the Certificate payload [5] to the server.
Certificate payload [5] to the server.
client_hello,
certificate_type=(RawPublicKey-Offer, RawPublicKey-Accept) -> // [1]
<- server_hello, client_hello,
certificate_type=(RawPublicKey-Offer, client_certificate_type=(RawPublicKey) // [1]
RawPublicKey-Accept) // [2] server_certificate_type=(RawPublicKey) // [1]
certificate, // [3] ->
certificate_request, // [4] <- server_hello,
server_key_exchange, server_certificate_type=(RawPublicKey)//[2]
server_hello_done certificate, // [3]
client_certificate_type=(RawPublicKey)//[4]
certificate_request, // [4]
server_key_exchange,
server_hello_done
certificate, // [5] certificate, // [5]
client_key_exchange, client_key_exchange,
change_cipher_spec, change_cipher_spec,
finished -> finished ->
<- change_cipher_spec, <- change_cipher_spec,
finished finished
Application Data <-------> Application Data Application Data <-------> Application Data
Figure 6: Example with Raw Public Key provided by the TLS Server and Figure 7: Example with Raw Public Key provided by the TLS Server and
the Client the Client
In our last example we illustrate a combination of raw public key and In our last example we illustrate a combination of raw public key and
X.509 usage. The client uses a raw public key for client X.509 usage. The client uses a raw public key for client
authentication but the server provides an X.509 certificate. This authentication but the server provides an X.509 certificate. This
exchange starts with the client indicating its ability to process exchange starts with the client indicating its ability to process
X.509 certificates provided by the server, and the ability to send X.509 certificates provided by the server, and the ability to send
raw public keys. The server provides the X.509 certificate in [3] raw public keys (see [1]). The server provides the X.509 certificate
with the indication present in [2]. For client authentication, in [3] with the indication present in [2]. For client authentication
however, the server indicates in [2] that it is able to support raw the server indicates in [4] that it selected the raw public key
public keys and requests a certificate from the client in [4]. The format and requests a certificate from the client in [5]. The TLS
TLS client provides a raw public key in [5] after receiving and client provides a raw public key in [6] after receiving and
processing the TLS server hello message. processing the TLS server hello message.
client_hello, client_hello,
certificate_type=(X.509-Accept, RawPublicKey-Offer) -> // [1] server_certificate_type=(X.509)
client_certificate_type=(RawPublicKey) // [1]
<- server_hello, ->
certificate_type=(X.509-Offer, <- server_hello,
RawPublicKey-Accept), // [2] server_certificate_type=(X.509)//[2]
certificate, // [3] certificate, // [3]
certificate_request, // [4] client_certificate_type=(RawPublicKey)//[4]
server_key_exchange, certificate_request, // [5]
server_hello_done server_key_exchange,
certificate, // [5] server_hello_done
client_key_exchange, certificate, // [6]
change_cipher_spec, client_key_exchange,
finished -> change_cipher_spec,
finished ->
<- change_cipher_spec, <- change_cipher_spec,
finished finished
Application Data <-------> Application Data Application Data <-------> Application Data
Figure 7: Hybrid Certificate Example Figure 8: Hybrid Certificate Example
6. Security Considerations 6. Security Considerations
The transmission of raw public keys, as described in this document, The transmission of raw public keys, as described in this document,
provides benefits by lowering the over-the-air transmission overhead provides benefits by lowering the over-the-air transmission overhead
since raw public keys are quite naturally smaller than an entire since raw public keys are quite naturally smaller than an entire
certificate. There are also advantages from a codesize point of view certificate. There are also advantages from a codesize point of view
for parsing and processing these keys. The crytographic procedures for parsing and processing these keys. The crytographic procedures
for assocating the public key with the possession of a private key for assocating the public key with the possession of a private key
also follows standard procedures. also follows standard procedures.
skipping to change at page 12, line 9 skipping to change at page 13, line 10
suitable for a generic Web-based e-commerce environment such keys are suitable for a generic Web-based e-commerce environment such keys are
a reasonable approach for many smart object deployments where there a reasonable approach for many smart object deployments where there
is a close relationship between the software running on the device is a close relationship between the software running on the device
and the server-side communication endpoint. Regardless of the chosen and the server-side communication endpoint. Regardless of the chosen
mechanism for out-of-band public key validation an assessment of the mechanism for out-of-band public key validation an assessment of the
most suitable approach has to be made prior to the start of a most suitable approach has to be made prior to the start of a
deployment to ensure the security of the system. deployment to ensure the security of the system.
7. IANA Considerations 7. IANA Considerations
This document defines a new TLS extension, "certificate_type", IANA is asked to register a new value in the "TLS Certificate Types"
assigned a value of [TBD] from the TLS ExtensionType registry defined registry of Transport Layer Security (TLS) Extensions
in [RFC5246]. This value is used as the extension number for the [TLS-Certificate-Types-Registry], as follows:
extensions in both the client hello message and the server hello
message. The new extension type is used for certificate type
negotiation.
The "certificate_type" extension contains an 8-bit CertificateType
field, for which a new registry, named "TLS Certificate Types", is
established in this document, to be maintained by IANA. The registry
is segmented in the following way:
1. The values 0 - 3 are defined in Figure 4.
2. Values from 3 through 223 decimal inclusive are assigned via IETF Value: 2
Consensus [RFC5226]. Description: Raw Public Key
Reference: [[THIS RFC]]
3. Values from 224 decimal through 255 decimal inclusive are This document asks IANA to allocate two new TLS extensions,
reserved for Private Use [RFC5226]. "client_certificate_type" and "server_certificate_type", from the TLS
ExtensionType registry defined in [RFC5246]. These extensions are
used in both the client hello message and the server hello message.
The new extension type is used for certificate type negotiation. The
values carried in these extensions are taken from the TLS Certificate
Types registry [TLS-Certificate-Types-Registry].
8. Acknowledgements 8. Acknowledgements
The feedback from the TLS working group meeting at IETF#81 has The feedback from the TLS working group meeting at IETF#81 has
substantially shaped the document and we would like to thank the substantially shaped the document and we would like to thank the
meeting participants for their input. The support for hashes of meeting participants for their input. The support for hashes of
public keys has been moved to [I-D.ietf-tls-cached-info] after the public keys has been moved to [I-D.ietf-tls-cached-info] after the
discussions at the IETF#82 meeting and the feedback from Eric discussions at the IETF#82 meeting.
Rescorla.
We would like to thank the following persons for their review We would like to thank the following persons for their review
comments: Martin Rex, Bill Frantz, Zach Shelby, Carsten Bormann, comments: Martin Rex, Bill Frantz, Zach Shelby, Carsten Bormann,
Cullen Jennings, Rene Struik, Alper Yegin, Jim Schaad, Paul Hoffman, Cullen Jennings, Rene Struik, Alper Yegin, Jim Schaad, Barry Leiba,
Robert Cragie, Nikos Mavrogiannopoulos, Phil Hunt, John Bradley, Paul Hoffman, Robert Cragie, Nikos Mavrogiannopoulos, Phil Hunt, John
Klaus Hartke, Stefan Jucker, and James Manger. Bradley, Klaus Hartke, Stefan Jucker, Kovatsch Matthias, Daniel Kahn
Gillmor, and James Manger. Nikos Mavrogiannopoulos contributed the
design for re-using the certificate type registry. Barry Leiba
contributed guidance for the IANA consideration text. Stefan Jucker,
Kovatsch Matthias, and Klaus Hartke provided implementation feedback
regarding the SubjectPublicKeyInfo structure.
Finally, we would like to thank our TLS working group chairs, Eric
Rescorla and Joe Salowey, for their guidance and support.
9. References 9. References
9.1. Normative References 9.1. Normative References
[PKIX] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [PKIX] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008. (CRL) Profile", RFC 5280, May 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
skipping to change at page 13, line 17 skipping to change at page 14, line 20
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008. (CRL) Profile", RFC 5280, May 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[TLS-Certificate-Types-Registry]
"TLS Certificate Types Registry", February 2013, <http://
www.iana.org/assignments/
tls-extensiontype-values#tls-extensiontype-values-2>.
9.2. Informative References 9.2. Informative References
[ASN.1-Dump]
Gutmann, P., "ASN.1 Object Dump Program", February 2013,
<http://www.cs.auckland.ac.nz/~pgut001/>.
[Defeating-SSL] [Defeating-SSL]
Marlinspike, M., "New Tricks for Defeating SSL in Marlinspike, M., "New Tricks for Defeating SSL in
Practice", February 2009, <http://www.blackhat.com/ Practice", February 2009, <http://www.blackhat.com/
presentations/bh-dc-09/Marlinspike/ presentations/bh-dc-09/Marlinspike/
BlackHat-DC-09-Marlinspike-Defeating-SSL.pdf>. BlackHat-DC-09-Marlinspike-Defeating-SSL.pdf>.
[I-D.ietf-core-coap] [I-D.ietf-core-coap]
Shelby, Z., Hartke, K., Bormann, C., and B. Frank, Shelby, Z., Hartke, K., Bormann, C., and B. Frank,
"Constrained Application Protocol (CoAP)", "Constrained Application Protocol (CoAP)",
draft-ietf-core-coap-12 (work in progress), October 2012. draft-ietf-core-coap-13 (work in progress), December 2012.
[I-D.ietf-tls-cached-info] [I-D.ietf-tls-cached-info]
Santesson, S. and H. Tschofenig, "Transport Layer Security Santesson, S. and H. Tschofenig, "Transport Layer Security
(TLS) Cached Information Extension", (TLS) Cached Information Extension",
draft-ietf-tls-cached-info-13 (work in progress), draft-ietf-tls-cached-info-13 (work in progress),
September 2012. September 2012.
[LDAP] Sermersheim, J., "Lightweight Directory Access Protocol [LDAP] Sermersheim, J., "Lightweight Directory Access Protocol
(LDAP): The Protocol", RFC 4511, June 2006. (LDAP): The Protocol", RFC 4511, June 2006.
[RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and [RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 3279, April 2002. (CRL) Profile", RFC 3279, April 2002.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication [RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS) of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, August 2012. Protocol: TLSA", RFC 6698, August 2012.
Appendix A. Example Encoding
For example, the following hex sequence describes a
SubjectPublicKeyInfo structure inside the certificate payload:
0 1 2 3 4 5 6 7 8 9
---+------+-----+-----+-----+-----+-----+-----+-----+-----+-----
1 | 0x30, 0x81, 0x9f, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48,
2 | 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x81,
3 | 0x8d, 0x00, 0x30, 0x81, 0x89, 0x02, 0x81, 0x81, 0x00, 0xcd,
4 | 0xfd, 0x89, 0x48, 0xbe, 0x36, 0xb9, 0x95, 0x76, 0xd4, 0x13,
5 | 0x30, 0x0e, 0xbf, 0xb2, 0xed, 0x67, 0x0a, 0xc0, 0x16, 0x3f,
6 | 0x51, 0x09, 0x9d, 0x29, 0x2f, 0xb2, 0x6d, 0x3f, 0x3e, 0x6c,
7 | 0x2f, 0x90, 0x80, 0xa1, 0x71, 0xdf, 0xbe, 0x38, 0xc5, 0xcb,
8 | 0xa9, 0x9a, 0x40, 0x14, 0x90, 0x0a, 0xf9, 0xb7, 0x07, 0x0b,
9 | 0xe1, 0xda, 0xe7, 0x09, 0xbf, 0x0d, 0x57, 0x41, 0x86, 0x60,
10 | 0xa1, 0xc1, 0x27, 0x91, 0x5b, 0x0a, 0x98, 0x46, 0x1b, 0xf6,
11 | 0xa2, 0x84, 0xf8, 0x65, 0xc7, 0xce, 0x2d, 0x96, 0x17, 0xaa,
12 | 0x91, 0xf8, 0x61, 0x04, 0x50, 0x70, 0xeb, 0xb4, 0x43, 0xb7,
13 | 0xdc, 0x9a, 0xcc, 0x31, 0x01, 0x14, 0xd4, 0xcd, 0xcc, 0xc2,
14 | 0x37, 0x6d, 0x69, 0x82, 0xd6, 0xc6, 0xc4, 0xbe, 0xf2, 0x34,
15 | 0xa5, 0xc9, 0xa6, 0x19, 0x53, 0x32, 0x7a, 0x86, 0x0e, 0x91,
16 | 0x82, 0x0f, 0xa1, 0x42, 0x54, 0xaa, 0x01, 0x02, 0x03, 0x01,
17 | 0x00, 0x01
Figure 9: Example SubjectPublicKeyInfo Structure Byte Sequence.
The decoded byte-sequence shown in Figure 9 (for example using
Peter's ASN.1 decoder [ASN.1-Dump]) illustrates the structure, as
shown in Figure 10.
Offset Length Description
-------------------------------------------------------------------
0 3+159: SEQUENCE {
3 2+13: SEQUENCE {
5 2+9: OBJECT IDENTIFIER Value (1 2 840 113549 1 1 1)
: PKCS #1, rsaEncryption
16 2+0: NULL
: }
18 3+141: BIT STRING, encapsulates {
22 3+137: SEQUENCE {
25 3+129: INTEGER Value (1024 bit)
157 2+3: INTEGER Value (65537)
: }
: }
: }
Figure 10: Decoding of Example SubjectPublicKeyInfo Structure.
Authors' Addresses Authors' Addresses
Paul Wouters (editor) Paul Wouters (editor)
Red Hat Red Hat
Email: paul@nohats.ca Email: paul@nohats.ca
Hannes Tschofenig (editor) Hannes Tschofenig (editor)
Nokia Siemens Networks Nokia Siemens Networks
Linnoitustie 6 Linnoitustie 6
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