HTTPBIS M. Thomson Internet-Draft Mozilla Intended status: Standards Track May 8, 2014 Expires: November 9, 2014 Client Authentication over New TLS Connection draft-thomson-httpbis-cant-00 Abstract This document defines an HTTP authentication scheme that can be added to an error response to indicate to a client that a successful response will only be provided over a new TLS connection, and only if the client has provided a certificate on that connection. 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- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any 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 November 9, 2014. Copyright Notice Copyright (c) 2014 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 (http://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. Thomson Expires November 9, 2014 [Page 1] Internet-Draft CANT May 2014 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions and Terminology . . . . . . . . . . . . . . . 2 2. Client Certificate Challenge . . . . . . . . . . . . . . . . 2 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 6.2. Informational References . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction Client authentication in HTTP sometimes relies on certificate-based authentication of clients in Transport Layer Security (TLS) [RFC5246]. Some uses of client authentication rely on TLS renegotiation, triggering renegotiation in response to a request for a particular resource. HTTP/2 [I-D.ietf-httpbis-http2] forbids the use of renegotiation, except for at the very beginning of a connection. This makes addressing some client authentication use cases difficult. This document defines a new authentication scheme, "ClientCertificate", for use in HTTP authentication challenges [I-D.ietf-httpbis-p7-auth]. In combination with the 401 (Unauthorized) status code, this indicates that the resource requires client authentication at the TLS layer in order to access it. 1.1. Conventions and Terminology At times, this document falls back on shorthands for establishing interoperability requirements on implementations: the capitalized words "MUST", "SHOULD" and "MAY". These terms are defined in [RFC2119]. 2. Client Certificate Challenge A new authentication scheme ([I-D.ietf-httpbis-p7-auth]) for the "WWW-Authenticate" and "Proxy-Authenticate" header fields is defined with the name "ClientCertificate". A challenge with this authentication scheme does not define any parameters except "realm". The "realm" can be used to select an appropriate certificate, or if a certificate is already in use, to indicate the need for a different certificate. Other challenge Thomson Expires November 9, 2014 [Page 2] Internet-Draft CANT May 2014 parameters MAY be used to provide a client with information it can use to select an appropriate certificate. Unknown parameters MUST be ignored. This challenge cannot be satisfied by constructing an Authorization header field [I-D.ietf-httpbis-p7-auth], it can only be satisfied by making the request on a TLS connection where an appropriate certificate has been provided by the client. To effectively use this authentication scheme, a new connection is needed for every protection space used by a given origin server. A client can use the "ClientCertificate" challenge as a trigger to open a new connection and to use client authentication on that connection. The client can use the mechanism in [I-D.thomson-tls-care] to prompt the server to request a client certificate, to avoid the problem where the server doesn't know to make this request. 3. Security Considerations Clients that support this authentication scheme will create a new connection each time that they see a challenge. This could be exploited in order to generate additional load in terms of connections on both server and client. Using new connections for client authentication has additional processing costs to the client in proving access to the private keys associated with the client certificate; and to the server in proving access to the private keys associated with their certificate twice in the case that the client opts for confidentiality protection on the client certificate. HTTP/2 [I-D.ietf-httpbis-http2] allows clients to use the same connection for multiple canonical root URIs. Certificate-based client authentication as defined by this specification is bound to a single origin. This could create issues whereby the security properties of a connection could become confused. Clients MUST ensure that a client-authenticated connection is only used for the origin for which it was created. 4. IANA Considerations IANA is requested to create an entry in the HTTP Authentication Scheme Registry with the following information: ClientCertificate This document Thomson Expires November 9, 2014 [Page 3] Internet-Draft CANT May 2014 This scheme does not rely on the Authorization header field. 5. Acknowledgements Eric Rescorla helped identify the problem and formulate this mechanism. Julian Reschke and Michael Koeller provided excellent feedback. 6. References 6.1. Normative References [I-D.ietf-httpbis-p7-auth] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Authentication", draft-ietf-httpbis-p7-auth-26 (work in progress), February 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, December 2011. 6.2. Informational References [I-D.ietf-httpbis-http2] Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer Protocol version 2", draft-ietf-httpbis-http2-12 (work in progress), April 2014. [I-D.thomson-tls-care] Thomson, M., draft-thomson-tls-care-00 (work in progress), March 2014. Author's Address Martin Thomson Mozilla Suite 300 650 Castro Street Mountain View, CA 94041 US Email: martin.thomson@gmail.com Thomson Expires November 9, 2014 [Page 4]