Network Working Group Y. Rosomakho
Internet-Draft Zscaler
Updates: 9001 (if approved) H. Tschofenig
Intended status: Standards Track H-BRS
Expires: 27 August 2025 23 February 2025
Extended Key Update for QUIC
draft-rosomakho-quic-extended-key-update-00
Abstract
This document specifies an Extended Key Update mechanism for the QUIC
protocol, building on the foundation of the TLS Extended Key Update.
The TLS Extended Key Update specification enhances the TLS protocol
by introducing key updates with forward secrecy, eliminating the need
to perform a full handshake. This feature is particularly beneficial
for maintaining security in scenarios involving long-lived
connections.
This specification replaces the QUIC Key Update mechanism described
in the "Using TLS to Secure QUIC" specification.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://yaroslavros.github.io/quic-extended-key-update/draft-
rosomakho-quic-extended-key-update.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-
rosomakho-quic-extended-key-update/.
Source for this draft and an issue tracker can be found at
https://github.com/yaroslavros/quic-extended-key-update.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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This Internet-Draft will expire on 27 August 2025.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Extended Key Update Negotiation . . . . . . . . . . . . . . . 3
4. Extended Key Update Messages . . . . . . . . . . . . . . . . 4
5. Updating the Traffic Secrets . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The QUIC protocol [QUIC] provides a secure, versatile transport for
various applications, suitable for long-lived sessions in
environments like industrial IoT, telecommunication networks or
Virtual Private Networks (VPN), as specified in [RFC9484].
The TLS Extended Key Update [I-D.ietf-tls-extended-key-update]
introduces a mechanism to enhance the security and flexibility of
encrypted communication protocols by enabling frequent key updates
without requiring a full handshake renegotiation. This approach
allows applications to refresh their encryption keys more often,
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improving forward secrecy and reducing the risk of key compromise
over long-lived connections. By separating key updates from the
computationally expensive handshake process, the specification
provides a lightweight method for maintaining robust encryption in
scenarios where connections need to remain secure for extended
periods.
This new TLS capability is particularly valuable in environments
where interruptions to perform a full key exchange would cause
significant disruption. Other encrypted communication protocols,
such as IPsec [IKEv2] and SSH [SSH-TRANSPORT], include mechanisms for
re-exchanging keys without interrupting active sessions. The TLS
Extended Key Update specification ensures that even in the face of
potential key compromise, sensitive data remains protected due to
frequent key rotation and the use of forward secrecy.
This specification builds on concepts from
[I-D.ietf-tls-extended-key-update] and applies them to the QUIC
protocol context. It thereby replaces the QUIC Key Update mechanism
described in Section 6 of [QUIC-TLS].
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Readers are assumed to be familiar with
[I-D.ietf-tls-extended-key-update].
3. Extended Key Update Negotiation
QUIC peers negotiate Extended Key Update through the TLS handshake
process, as outlined in Section 4 of
[I-D.ietf-tls-extended-key-update]. Extended Key Update MUST NOT be
used unless both QUIC peers include the TLS flags extension
[I-D.ietf-tls-tlsflags] in the handshake and set the
"Extended_Key_Update" flag.
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Once Extended Key Update has been succesfully negotiated, QUIC peers
MUST only use the Extended Key Update process defined in this
document. The standard QUIC Key Update mechanism from Section 6 of
[QUIC-TLS] MUST NOT be used for the duration of the session, as both
Key Update and Extended Key Update use the Key Phase bit to signal
the use of updated keys. The Key Phase bit is initially set to 0 and
toggled to indicate a key update following the succesful post-
handshake exchange of Extended Key Update messsages.
4. Extended Key Update Messages
Either party MAY initiate the Extended Key Update process by sending
an ExtendedKeyUpdateRequest TLS handshake message in a QUIC CRYPTO
frame. This message MUST NOT be sent before the QUIC handshake is
confirmed, as described in Section 4.1.2 of [QUIC-TLS], or before
previous Extended Key Update process is complete. If a QUIC
endpoints receives an ExtendedKeyUpdateRequest message before the
QUIC handshake is complete or during ongoing prior Extended Key
Update, it MUST terminate the connection with an error of type
0x010a, equivalent to TLS unexpected_message alert as specified in
Section 4.8 of [QUIC-TLS].
Upon receiving an ExtendedKeyUpdateRequest, the recipient MUST
respond with an ExtendedKeyUpdateResponse TLS handshake message
within a QUIC CRYPTO frame. If a QUIC endpoint receives an
unexpected ExtendedKeyUpdateResponse message from its peer, it MUST
treat this as a TLS protocol error and terminate the connection.
Specifications of the ExtendedKeyUpdateRequest and
ExtendedKeyUpdateResponse messages are provided in Section 5 of
[I-D.ietf-tls-extended-key-update]. Any mismatch between the
negotiated NamedGroup during the initial handshake and the group used
in the Extended Key Update message, or an incorrect length of the
encapsulated key MUST result in connection termination with error of
type 0x012f, equivalend to TLS illegal_parameter alert.
If the Extended Key Update initiator receives a retry or rejected
status in the ExtendedKeyUpdateResponse message, it MAY terminate the
connection with error of type 0x01TBD, equivalent to TLS
extended_key_update_required alert.
5. Updating the Traffic Secrets
After sending an ExtendedKeyUpdateResponse with accepted status, the
responder derives new packet protection traffic secrets. The
responder MUST continue using the previous secrets until it has
received a packet with the Key Phase bit flipped and has successfully
unprotected it using the new keys.
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After recieving and succesfully processing an
ExtendedKeyUpdateResponse with accepted status, the initiator derives
new packet protection traffic secrets, flips the Key Phase bit for
new packets, and uses the new write secret to protect them. The
initiator MUST retain the old read secret until it has received a
packet with a flipped Key Phase bit from the responder and
succesfully unprotected it using the new read secret.
Both endpoints SHOULD retain old read secrets for some time after
unprotecting a packet encrypted with the new keys. Discarding old
secret too early may cause delayed packets to be discarded, which the
peer may interpreted as packet loss, potentially impacting
performance.
Figure 1 shows this interaction graphically.
Initiator Responder
[ packet using old key
and prior Key Phase ] -------->
<-------- [ packet using old key
and prior Key Phase ]
...
[ExtendedKeyUpdateRequest] -------->
<-------- [ExtendedKeyUpdateResponse]
[ packet using new key
and updated Key Phase ] -------->
<-------- [ packet using new key
and updated Key Phase ]
...
Figure 1: Extended Key Update Process in QUIC.
QUIC endpoints MUST NOT send NewKeyUpdate TLS handshake messages,
defined in [I-D.ietf-tls-extended-key-update], and instead relies on
the use of the Key Phase bit. Endpoints MUST treat the receipt of a
TLS NewKeyUpdate message as a connection error of type 0x010a. QUIC
endpoints that have agreed to the Extended Key Update process MUST
NOT change the Key Phase bit without a succesful exchange of Extended
Key Update TLS messages. Receiving a packet with the Key Phase bit
changed without a success Extended Key Update exchange MUST be
treated as a connection error of type KEY_UPDATE_ERROR (0x0e).
The design of the key derivation function for computing the next
generation of secrets is corresponds to the one described in
Section 6 of [I-D.ietf-tls-extended-key-update] with the exception of
the use of a different label.
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sk = HKDF-Extract(Transcript-Hash(ExtendedKeyUpdateRequest,
ExtendedKeyUpdateResponse), secret)
secret_<n+1> = HKDF-Expand-Label(sk, "quic eku",
secret_<n>, Hash.length)
The corresponding key and IV are derived from the new secret as
defined in Section 5.1 of [QUIC-TLS]. The header protection key is
not updated.
6. Security Considerations
This specification describes an update to the key schedule of QUIC.
Therefore, implementations MUST ensure that peers adhere strictly to
the process described in this document. Packets with higher packet
numbers MUST NOT be protected using an older generation of secrets,
as this could compromise key synchronization and security.
As key exchange may be computationally intensive, responders SHOULD
consider rate-limiting Extended Key Exchange requests. This can be
done by responding with retry status as outlined in Section 5 of
[I-D.ietf-tls-extended-key-update] and terminating connections for
initiators that violate the back-off timer. This approach helps
prevent excessive load on endpoints and mitigates the risk of denial-
of-service attacks.
7. IANA Considerations
This document has no IANA actions.
8. References
8.1. Normative References
[I-D.ietf-tls-extended-key-update]
Tschofenig, H., Tüxen, M., Reddy.K, T., Fries, S., and Y.
Rosomakho, "Extended Key Update for Transport Layer
Security (TLS) 1.3", Work in Progress, Internet-Draft,
draft-ietf-tls-extended-key-update-03, 21 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
extended-key-update-03>.
[I-D.ietf-tls-tlsflags]
Nir, Y., "A Flags Extension for TLS 1.3", Work in
Progress, Internet-Draft, draft-ietf-tls-tlsflags-14, 13
September 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-tls-tlsflags-14>.
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[QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>.
[QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
<https://www.rfc-editor.org/rfc/rfc9001>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
8.2. Informative References
[IKEv2] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/rfc/rfc7296>.
[RFC9484] Pauly, T., Ed., Schinazi, D., Chernyakhovsky, A.,
Kühlewind, M., and M. Westerlund, "Proxying IP in HTTP",
RFC 9484, DOI 10.17487/RFC9484, October 2023,
<https://www.rfc-editor.org/rfc/rfc9484>.
[SSH-TRANSPORT]
Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, <https://www.rfc-editor.org/rfc/rfc4253>.
Acknowledgments
We would like to thank Martin Thomson and Sean Turner for their early
review of this design and their invaluable feedback.
Authors' Addresses
Yaroslav Rosomakho
Zscaler
Email: yrosomakho@zscaler.com
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Hannes Tschofenig
University of Applied Sciences Bonn-Rhein-Sieg
Germany
Email: Hannes.Tschofenig@gmx.net
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