HTTP Strict Transport Security (HSTS)
RFC 6797

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Internet Engineering Task Force (IETF)                         J. Hodges
Request for Comments: 6797                                        PayPal
Category: Standards Track                                     C. Jackson
ISSN: 2070-1721                               Carnegie Mellon University
                                                                A. Barth
                                                            Google, Inc.
                                                           November 2012

                 HTTP Strict Transport Security (HSTS)

Abstract

   This specification defines a mechanism enabling web sites to declare
   themselves accessible only via secure connections and/or for users to
   be able to direct their user agent(s) to interact with given sites
   only over secure connections.  This overall policy is referred to as
   HTTP Strict Transport Security (HSTS).  The policy is declared by web
   sites via the Strict-Transport-Security HTTP response header field
   and/or by other means, such as user agent configuration, for example.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6797.

Hodges, et al.               Standards Track                    [Page 1]
RFC 6797          HTTP Strict Transport Security (HSTS)    November 2012

Copyright Notice

   Copyright (c) 2012 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.

Table of Contents

   1. Introduction ....................................................4
      1.1. Organization of This Specification .........................6
      1.2. Document Conventions .......................................6
   2. Overview ........................................................6
      2.1. Use Cases ..................................................6
      2.2. HTTP Strict Transport Security Policy Effects ..............6
      2.3. Threat Model ...............................................6
           2.3.1. Threats Addressed ...................................7
                  2.3.1.1. Passive Network Attackers ..................7
                  2.3.1.2. Active Network Attackers ...................7
                  2.3.1.3. Web Site Development and Deployment Bugs ...8
           2.3.2. Threats Not Addressed ...............................8
                  2.3.2.1. Phishing ...................................8
                  2.3.2.2. Malware and Browser Vulnerabilities ........8
      2.4. Requirements ...............................................9
           2.4.1. Overall Requirement .................................9
                  2.4.1.1. Detailed Core Requirements .................9
                  2.4.1.2. Detailed Ancillary Requirements ...........10
   3. Conformance Criteria ...........................................10
   4. Terminology ....................................................11
   5. HSTS Mechanism Overview ........................................13
      5.1. HSTS Host Declaration .....................................13
      5.2. HSTS Policy ...............................................13
      5.3. HSTS Policy Storage and Maintenance by User Agents ........14
      5.4. User Agent HSTS Policy Enforcement ........................14
   6. Syntax .........................................................14
      6.1. Strict-Transport-Security HTTP Response Header Field ......15
           6.1.1. The max-age Directive ..............................16
           6.1.2. The includeSubDomains Directive ....................16
      6.2. Examples ..................................................16

Hodges, et al.               Standards Track                    [Page 2]
RFC 6797          HTTP Strict Transport Security (HSTS)    November 2012

   7. Server Processing Model ........................................17
      7.1. HTTP-over-Secure-Transport Request Type ...................17