Using TLS 1.3 with HTTP/2
draft-ietf-httpbis-http2-tls13-00

HTTP                                                         D. Benjamin
Internet-Draft                                                Google LLC
Updates: 7540 (if approved)                                 May 13, 2019
Intended status: Standards Track
Expires: November 14, 2019

                       Using TLS 1.3 with HTTP/2
                   draft-ietf-httpbis-http2-tls13-00

Abstract

   This document clarifies the use of TLS 1.3 post-handshake
   authentication and key update with HTTP/2.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on November 14, 2019.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   2
   3.  Post-Handshake Authentication in HTTP/2 . . . . . . . . . . .   2
   4.  Key Updates in HTTP/2 . . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   TLS 1.2 [RFC5246] and earlier support renegotiation, a mechanism for
   changing parameters and keys partway through a connection.  This was
   sometimes used to implement reactive client authentication in
   HTTP/1.1 [RFC7230], where the server decides whether to request a
   client certificate based on the HTTP request.

   HTTP/2 [RFC7540] multiplexes multiple HTTP requests over a single
   connection, which is incompatible with the mechanism above.  Clients
   cannot correlate the certificate request with the HTTP request which
   triggered it.  Thus, section 9.2.1 of [RFC7540] forbids
   renegotiation.

   TLS 1.3 [RFC8446] updates TLS 1.2 to remove renegotiation in favor of
   separate post-handshake authentication and key update mechanisms.
   The former shares the same problems with multiplexed protocols, but
   has a different name.  This makes it ambiguous whether post-handshake
   authentication is allowed in TLS 1.3.

   This document clarifies that the prohibition applies to post-
   handshake authentication but not to key updates.

2.  Requirements Language

   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.

3.  Post-Handshake Authentication in HTTP/2

   The prohibition on renegotiation in section 9.2.1 of [RFC7540]
   additionally applies to TLS 1.3 post-handshake authentication.
   HTTP/2 servers MUST NOT send post-handshake TLS 1.3
   CertificateRequest messages.  HTTP/2 clients MUST treat TLS 1.3 post-

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   handshake authentication as a connection error (see section 5.4.1 of
   [RFC7540]) of type PROTOCOL_ERROR.

   [RFC7540] permitted renegotiation before the HTTP/2 connection
   preface to provide confidentiality of the client certificate.  TLS
   1.3 encrypts the client certificate in the initial handshake, so this
   is no longer necessary.  HTTP/2 servers MUST NOT send post-handshake
   TLS 1.3 CertificateRequest messages before the connection preface.

   The above applies even if the client offered the
   "post_handshake_auth" TLS extension.  This extension is advertised
   independently of the selected ALPN protocol [RFC7301], so it is not
   sufficient to resolve the conflict with HTTP/2.  HTTP/2 clients that
   also offer other ALPN protocols, notably HTTP/1.1, in a TLS
   ClientHello MAY include the "post_handshake_auth" extension to
   support those other protocols.  This does not indicate support in
   HTTP/2.

4.  Key Updates in HTTP/2

   Section 9.2.1 of [RFC7540] does not extend to TLS 1.3 KeyUpdate
   messages.  HTTP/2 implementations MUST support key updates when TLS
   1.3 is negotiated.

5.  Security Considerations

   This document clarifies how to use HTTP/2 with TLS 1.3 and resolves a
   compatibility concern when supporting post-handshake authentication
   with HTTP/1.1.  This lowers the barrier for deploying TLS 1.3, a
   major security improvement over TLS 1.2.  Permitting key updates
   allows key material to be refreshed in long-lived HTTP/2 connections.

6.  IANA Considerations

   This document has no IANA actions.

7.  Normative References

   [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/info/rfc2119>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

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   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7301]  Friedl, S., Popov, A., Langley, A., and E. Stephan,
              "Transport Layer Security (TLS) Application-Layer Protocol
              Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
              July 2014, <https://www.rfc-editor.org/info/rfc7301>.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/info/rfc7540>.

   [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/info/rfc8174>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

Author's Address

   David Benjamin
   Google LLC

   Email: davidben@google.com

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