draft-ietf-tls-dtls-rrc-00.txt   draft-ietf-tls-dtls-rrc-01.txt 
TLS H. Tschofenig, Ed. TLS H. Tschofenig, Ed.
Internet-Draft T. Fossati Internet-Draft T. Fossati
Updates: 6347 (if approved) Arm Limited Updates: 6347 (if approved) Arm Limited
Intended status: Standards Track 9 June 2021 Intended status: Standards Track 25 October 2021
Expires: 11 December 2021 Expires: 28 April 2022
Return Routability Check for DTLS 1.2 and DTLS 1.3 Return Routability Check for DTLS 1.2 and DTLS 1.3
draft-ietf-tls-dtls-rrc-00 draft-ietf-tls-dtls-rrc-01
Abstract Abstract
This document specifies a return routability check for use in context This document specifies a return routability check for use in context
of the Connection ID (CID) construct for the Datagram Transport Layer of the Connection ID (CID) construct for the Datagram Transport Layer
Security (DTLS) protocol versions 1.2 and 1.3. Security (DTLS) protocol versions 1.2 and 1.3.
Discussion Venues Discussion Venues
This note is to be removed before publishing as an RFC. This note is to be removed before publishing as an RFC.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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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 11 December 2021. This Internet-Draft will expire on 28 April 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
3. The Return Routability Check Message . . . . . . . . . . . . 4 3. RRC Extension . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. The Return Routability Check Message . . . . . . . . . . . . 4
5. Security and Privacy Considerations . . . . . . . . . . . . . 7 5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Security and Privacy Considerations . . . . . . . . . . . . . 8
7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 8. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
Appendix A. History . . . . . . . . . . . . . . . . . . . . . . 8 10. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Appendix A. History . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
In "classical" DTLS, selecting a security context of an incoming DTLS In "classical" DTLS, selecting a security context of an incoming DTLS
record is accomplished with the help of the 5-tuple, i.e. source IP record is accomplished with the help of the 5-tuple, i.e. source IP
address, source port, transport protocol, destination IP address, and address, source port, transport protocol, destination IP address, and
destination port. Changes to this 5 tuple can happen for a variety destination port. Changes to this 5 tuple can happen for a variety
reasons over the lifetime of the DTLS session. In the IoT context, reasons over the lifetime of the DTLS session. In the IoT context,
NAT rebinding is common with sleepy devices. Other examples include NAT rebinding is common with sleepy devices. Other examples include
end host mobility and multi-homing. Without CID, if the source IP end host mobility and multi-homing. Without CID, if the source IP
skipping to change at page 4, line 10 skipping to change at page 3, line 44
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This document assumes familiarity with the CID format and protocol This document assumes familiarity with the CID format and protocol
defined for DTLS 1.2 [I-D.ietf-tls-dtls-connection-id] and for DTLS defined for DTLS 1.2 [I-D.ietf-tls-dtls-connection-id] and for DTLS
1.3 [I-D.ietf-tls-dtls13]. The presentation language used in this 1.3 [I-D.ietf-tls-dtls13]. The presentation language used in this
document is described in Section 4 of [RFC8446]. document is described in Section 4 of [RFC8446].
3. The Return Routability Check Message 3. RRC Extension
This specification uses the tls_flags extension defined in
[I-D.ietf-tls-tlsflags] to allow a client and a server to negotiate
support for this extension.
The RRC flag is assigned the value (TBD1) and is used in the
ClientHello (CH) and the ServerHello (SH).
4. The Return Routability Check Message
When a record with CID is received that has the source address of the When a record with CID is received that has the source address of the
enclosing UDP datagram different from the one previously associated enclosing UDP datagram different from the one previously associated
with that CID, the receiver MUST NOT update its view of the peer's IP with that CID, the receiver MUST NOT update its view of the peer's IP
address and port number with the source specified in the UDP datagram address and port number with the source specified in the UDP datagram
before cryptographically validating the enclosed record(s) but before cryptographically validating the enclosed record(s) but
instead perform a return routability check. instead perform a return routability check.
enum { enum {
invalid(0), invalid(0),
change_cipher_spec(20), change_cipher_spec(20),
alert(21), alert(21),
handshake(22), handshake(22),
application_data(23), application_data(23),
heartbeat(24), /* RFC 6520 */ heartbeat(24), /* RFC 6520 */
return_routability_check(TBD), /* NEW */ return_routability_check(TBD), /* NEW */
(255) (255)
} ContentType; } ContentType;
struct { uint64 Cookie;
opaque cookie<1..2^16-1>;
} Cookie; enum {
path_challenge(0),
path_response(1),
reserved(2..255)
} rrc_msg_type;
struct { struct {
Cookie cookie; rrc_msg_type msg_type;
select (return_routability_check.msg_type) {
case path_challenge: Cookie;
case path_response: Cookie;
};
} return_routability_check; } return_routability_check;
The newly introduced return_routability_check message contains a The newly introduced return_routability_check message contains a
cookie. The semantic of the cookie is similar to the cookie used in cookie. The cookie is a 8-byte field containing arbitrary data.
the HelloRetryRequest message defined in [RFC8446].
The return_routability_check message MUST be authenticated and The return_routability_check message MUST be authenticated and
encrypted using the currently active security context. encrypted using the currently active security context.
The receiver that observes the peer's address and or port update MUST The receiver that observes the peer's address and or port update MUST
stop sending any buffered application data (or limit the sending rate stop sending any buffered application data (or limit the data sent to
to a TBD threshold) and initiate the return routability check that a TBD threshold) and initiate the return routability check that
proceeds as follows: proceeds as follows:
1. A cookie is placed in the return_routability_check message; 1. A cookie is placed in a return_routability_check message of type
path_challenge;
2. The message is sent to the observed new address and a timeout T 2. The message is sent to the observed new address and a timeout T
is started; is started;
3. The peer endpoint, after successfully verifying the received 3. The peer endpoint, after successfully verifying the received
return_routability_check message echoes it back; return_routability_check message echoes the cookie value in a
return_routability_check message of type path_response;
4. When the initiator receives and verifies the 4. When the initiator receives and verifies the
return_routability_check message, it updates the peer address return_routability_check message contains the sent cookie, it
binding; updates the peer address binding;
5. If T expires, or the address confirmation fails, the peer address 5. If T expires, or the address confirmation fails, the peer address
binding is not updated. binding is not updated.
After this point, any pending send operation is resumed to the bound After this point, any pending send operation is resumed to the bound
peer address. peer address.
4. Example 5. Example
The example shown in Figure 1 illustrates a client and a server The example TLS 1.3 handshake shown in Figure 1 shows a client and a
exchanging application payloads protected by DTLS with an server negotiating the support for CID and for the RRC extension.
unilaterally used CIDs. At some point in the communication
interaction the IP address used by the client changes and, thanks to Client Server
the CID usage, the security context to interpret the record is
successfully located by the server. However, the server wants to Key ^ ClientHello
test the reachability of the client at his new IP address, to avoid Exch | + key_share
being abused (e.g., as an amplifier) by an attacker impersonating the | + signature_algorithms
client. | + tls_flags (RRC)
v + connection_id=empty
-------->
ServerHello ^ Key
+ key_share | Exch
+ connection_id=100 |
+ tls_flags (RRC) v
{EncryptedExtensions} ^ Server
{CertificateRequest} v Params
{Certificate} ^
{CertificateVerify} | Auth
<-------- {Finished} v
^ {Certificate}
Auth | {CertificateVerify}
v {Finished} -------->
[Application Data] <-------> [Application Data]
+ Indicates noteworthy extensions sent in the
previously noted message.
* Indicates optional or situation-dependent
messages/extensions that are not always sent.
{} Indicates messages protected using keys
derived from a [sender]_handshake_traffic_secret.
[] Indicates messages protected using keys
derived from [sender]_application_traffic_secret_N.
Figure 1: Message Flow for Full TLS Handshake
Once a connection has been established the client and the server
exchange application payloads protected by DTLS with an unilaterally
used CIDs. In our case, the client is requested to use CID 100 for
records sent to the server.
At some point in the communication interaction the IP address used by
the client changes and, thanks to the CID usage, the security context
to interpret the record is successfully located by the server.
However, the server wants to test the reachability of the client at
his new IP address.
Client Server Client Server
------ ------ ------ ------
Application Data ========> Application Data ========>
<CID=100> <CID=100>
Src-IP=A Src-IP=A
Dst-IP=Z Dst-IP=Z
<======== Application Data <======== Application Data
Src-IP=Z Src-IP=Z
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Application Data ========> Application Data ========>
<CID=100> <CID=100>
Src-IP=B Src-IP=B
Dst-IP=Z Dst-IP=Z
<<< Unverified IP <<< Unverified IP
Address B >> Address B >>
<-------- Return Routability Check <-------- Return Routability Check
(cookie) path_challenge(cookie)
Src-IP=Z Src-IP=Z
Dst-IP=B Dst-IP=B
Return Routability Check --------> Return Routability Check -------->
(cookie) path_response(cookie)
Src-IP=B Src-IP=B
Dst-IP=Z Dst-IP=Z
<<< IP Address B <<< IP Address B
Verified >> Verified >>
<======== Application Data <======== Application Data
Src-IP=Z Src-IP=Z
Dst-IP=B Dst-IP=B
Figure 1: Return Routability Example Figure 2: Return Routability Example
5. Security and Privacy Considerations 6. Security and Privacy Considerations
Note that the return routability checks do not protect against Note that the return routability checks do not protect against
flooding of third-parties if the attacker is on-path, as the attacker flooding of third-parties if the attacker is on-path, as the attacker
can redirect the return routability checks to the real peer (even if can redirect the return routability checks to the real peer (even if
those datagrams are cryptographically authenticated). On-path those datagrams are cryptographically authenticated). On-path
adversaries can, in general, pose a harm to connectivity. adversaries can, in general, pose a harm to connectivity.
6. IANA Considerations 7. IANA Considerations
IANA is requested to allocate an entry to the existing TLS IANA is requested to allocate an entry to the TLS "ContentType"
"ContentType" registry, for the return_routability_check(TBD) defined registry, for the return_routability_check(TBD) defined in this
in this document. document.
7. Open Issues IANA is requested to allocate an entry to the TLS Flags registry in
the tls_flags type:
* Value: [[IANA please assign a value from the 32-63 value range.]]
* Flag Name: RRC
* Message: CH,SH
* Recommended: Y
* Reference: [[This document]]
8. Open Issues
Issues against this document are tracked at https://github.com/tlswg/ Issues against this document are tracked at https://github.com/tlswg/
dtls-rrc/issues dtls-rrc/issues
8. Acknowledgments 9. Acknowledgments
We would like to thank Achim Kraus, Hanno Becker and Manuel Pegourie- We would like to thank Achim Kraus, Hanno Becker, Hanno Boeck, Manuel
Gonnard for their input to this document. Pegourie-Gonnard, Mohit Sahni and Rich Salz for their input to this
document.
9. Normative References 10. Normative References
[I-D.ietf-tls-dtls-connection-id] [I-D.ietf-tls-dtls-connection-id]
Rescorla, E., Tschofenig, H., Fossati, T., and A. Kraus, Rescorla, E., Tschofenig, H., Fossati, T., and A. Kraus,
"Connection Identifiers for DTLS 1.2", Work in Progress, "Connection Identifiers for DTLS 1.2", Work in Progress,
Internet-Draft, draft-ietf-tls-dtls-connection-id-12, 11 Internet-Draft, draft-ietf-tls-dtls-connection-id-13, 22
May 2021, <https://tools.ietf.org/html/draft-ietf-tls- June 2021, <https://datatracker.ietf.org/doc/html/draft-
dtls-connection-id-12>. ietf-tls-dtls-connection-id-13>.
[I-D.ietf-tls-dtls13] [I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version Datagram Transport Layer Security (DTLS) Protocol Version
1.3", Work in Progress, Internet-Draft, draft-ietf-tls- 1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
dtls13-43, 30 April 2021, dtls13-43, 30 April 2021,
<https://tools.ietf.org/html/draft-ietf-tls-dtls13-43>. <https://datatracker.ietf.org/doc/html/draft-ietf-tls-
dtls13-43>.
[I-D.ietf-tls-tlsflags]
Nir, Y., "A Flags Extension for TLS 1.3", Work in
Progress, Internet-Draft, draft-ietf-tls-tlsflags-06, 13
July 2021, <https://datatracker.ietf.org/doc/html/draft-
ietf-tls-tlsflags-06>.
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>. <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>. <https://www.rfc-editor.org/rfc/rfc8446>.
Appendix A. History Appendix A. History
RFC EDITOR: PLEASE REMOVE THE THIS SECTION RFC EDITOR: PLEASE REMOVE THE THIS SECTION
draft-ietf-tls-dtls-rrc-00 draft-ietf-tls-dtls-rrc-01
* Draft name changed after WG adoption * Use the TLS flags extension for negotiating RRC
draft-tschofenig-tls-dtls-rrc-01 * Enhanced IANA consideration section
* Expanded example section
* Revamp message layout:
- Use 8-byte fixed size cookies
- Explicitly separate path challenge from response
draft-ietf-tls-dtls-rrc-00
* Draft name changed after WG adoption
* Removed text that overlapped with draft-ietf-tls-dtls-connection- * Removed text that overlapped with draft-ietf-tls-dtls-connection-
id id
draft-tschofenig-tls-dtls-rrc-00 draft-tschofenig-tls-dtls-rrc-00
* Initial version * Initial version
Authors' Addresses Authors' Addresses
Hannes Tschofenig (editor) Hannes Tschofenig (editor)
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