Using TLS 1.3 with HTTP/2Google LLCdavidben@google.com
Applications and Real-Time
HTTPHTTPrenegotiationpost-handshake client authenticationThis document updates RFC 7540 by forbidding TLS 1.3 post-handshake
authentication, as an analog to the existing TLS 1.2 renegotiation restriction.Status of This Memo
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RFC 7841.
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Table of Contents
. Introduction
. Requirements Language
. Post-Handshake Authentication in HTTP/2
. Other Post-Handshake TLS Messages in HTTP/2
. Security Considerations
. IANA Considerations
. References
. Normative References
. Informative References
Author's Address
IntroductionTLS 1.2 and earlier
versions of TLS 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 , where the server decides whether or
not to request a client certificate based on the HTTP request.HTTP/2 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 that triggered it. Thus, forbids renegotiation.TLS 1.3 removes
renegotiation and replaces it with separate post-handshake
authentication and key update mechanisms. Post-handshake authentication
has the same problems with multiplexed protocols as TLS 1.2
renegotiation, but the prohibition in only applies to renegotiation.
This document updates HTTP/2 to similarly forbid TLS 1.3 post-handshake
authentication.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 when, and only when, they appear in all capitals,
as shown here.
Post-Handshake Authentication in HTTP/2HTTP/2 servers MUST NOT send post-handshake TLS 1.3 CertificateRequest messages.
HTTP/2 clients MUST treat such messages as connection errors (see ) of type PROTOCOL_ERROR. 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 Application-Layer Protocol Negotiation
(ALPN) protocol , 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.Other Post-Handshake TLS Messages in HTTP/2 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
and are allowed for in the
design of HTTP/2.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.Security ConsiderationsThis 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.IANA ConsiderationsThis document has no IANA actions.ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.The Transport Layer Security (TLS) Protocol Version 1.2This document specifies Version 1.2 of the Transport Layer Security (TLS) protocol. The TLS protocol provides communications security over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery. [STANDARDS-TRACK]Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and RoutingThe Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document provides an overview of HTTP architecture and its associated terminology, defines the "http" and "https" Uniform Resource Identifier (URI) schemes, defines the HTTP/1.1 message syntax and parsing requirements, and describes related security concerns for implementations.Transport Layer Security (TLS) Application-Layer Protocol Negotiation ExtensionThis document describes a Transport Layer Security (TLS) extension for application-layer protocol negotiation within the TLS handshake. For instances in which multiple application protocols are supported on the same TCP or UDP port, this extension allows the application layer to negotiate which protocol will be used within the TLS connection.Hypertext Transfer Protocol Version 2 (HTTP/2)This specification describes an optimized expression of the semantics of the Hypertext Transfer Protocol (HTTP), referred to as HTTP version 2 (HTTP/2). HTTP/2 enables a more efficient use of network resources and a reduced perception of latency by introducing header field compression and allowing multiple concurrent exchanges on the same connection. It also introduces unsolicited push of representations from servers to clients.This specification is an alternative to, but does not obsolete, the HTTP/1.1 message syntax. HTTP's existing semantics remain unchanged.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.The Transport Layer Security (TLS) Protocol Version 1.3This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery.This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations.Informative ReferencesUsing Early Data in HTTPUsing TLS early data creates an exposure to the possibility of a replay attack. This document defines mechanisms that allow clients to communicate with servers about HTTP requests that are sent in early data. Techniques are described that use these mechanisms to mitigate the risk of replay.Author's AddressGoogle LLCdavidben@google.com