



HTTP                                                         D. Benjamin
Internet-Draft                                                Google LLC
Updates: 7540 (if approved)                             October 17, 2019
Intended status: Standards Track
Expires: April 19, 2020


                       Using TLS 1.3 with HTTP/2
                   draft-ietf-httpbis-http2-tls13-03

Abstract

   This document updates RFC 7540 by forbidding TLS 1.3 post-handshake
   authentication, as an analog to the existing TLS 1.2 renegotiation
   restriction.

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   Discussion of this draft takes place on the HTTP working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   https://lists.w3.org/Archives/Public/ietf-http-wg/ [1].

   Working Group information can be found at https://httpwg.org/ [2];
   source code and issues list for this draft can be found at
   https://github.com/httpwg/http-extensions/labels/http2-tls13 [3].

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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   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
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 19, 2020.







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Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Post-Handshake Authentication in HTTP/2 . . . . . . . . . . .   3
   4.  Other Post-Handshake TLS Messages in HTTP/2 . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
     7.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

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
   the prohibition in [RFC7540] only applies to TLS 1.2 renegotiation.




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   This document updates HTTP/2 to similarly forbid TLS 1.3 post-
   handshake authentication.

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

   HTTP/2 servers MUST NOT send post-handshake TLS 1.3
   CertificateRequest messages.  HTTP/2 clients MUST treat such messages
   as connection errors (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.  Other Post-Handshake TLS Messages in HTTP/2

   [RFC8446] defines two other messages that are exchanged after the
   handshake is complete, KeyUpdate and NewSessionTicket.

   KeyUpdate messages only affect TLS itself and do not require any
   interaction with the application protocol.  HTTP/2 implementations
   MUST support key updates when TLS 1.3 is negotiated.

   NewSessionTicket messages are also permitted.  Though these interact
   with HTTP when early data is enabled, these interactions are defined
   in [RFC8470] and allowed for in the design of HTTP/2.






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   Unless the use of a new type of TLS message depends on an interaction
   with the application-layer protocol, that TLS message can be sent
   after the handshake completes.

5.  Security Considerations

   This document resolves a compatibility concern between HTTP/2 and TLS
   1.3 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.

6.  IANA Considerations

   This document has no IANA actions.

7.  References

7.1.  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>.

   [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>.




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   [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>.

7.2.  Informative References

   [RFC8470]  Thomson, M., Nottingham, M., and W. Tarreau, "Using Early
              Data in HTTP", RFC 8470, DOI 10.17487/RFC8470, September
              2018, <https://www.rfc-editor.org/info/rfc8470>.

7.3.  URIs

   [1] https://lists.w3.org/Archives/Public/ietf-http-wg/

   [2] https://httpwg.org/

   [3] https://github.com/httpwg/http-extensions/labels/http2-tls13

Author's Address

   David Benjamin
   Google LLC

   Email: davidben@google.com



























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