OAuth 2.0 Threat Model and Security Considerations
RFC 6819

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Internet Engineering Task Force (IETF)               T. Lodderstedt, Ed.
Request for Comments: 6819                           Deutsche Telekom AG
Category: Informational                                       M. McGloin
ISSN: 2070-1721                                                      IBM
                                                                 P. Hunt
                                                      Oracle Corporation
                                                            January 2013

           OAuth 2.0 Threat Model and Security Considerations

Abstract

   This document gives additional security considerations for OAuth,
   beyond those in the OAuth 2.0 specification, based on a comprehensive
   threat model for the OAuth 2.0 protocol.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc6819.

Copyright Notice

   Copyright (c) 2013 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
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   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.

Lodderstedt, et al.           Informational                     [Page 1]
RFC 6819                   OAuth 2.0 Security               January 2013

Table of Contents

   1. Introduction ....................................................6
   2. Overview ........................................................7
      2.1. Scope ......................................................7
      2.2. Attack Assumptions .........................................7
      2.3. Architectural Assumptions ..................................8
           2.3.1. Authorization Servers ...............................8
           2.3.2. Resource Server .....................................9
           2.3.3. Client ..............................................9
   3. Security Features ...............................................9
      3.1. Tokens ....................................................10
           3.1.1. Scope ..............................................11
           3.1.2. Limited Access Token Lifetime ......................11
      3.2. Access Token ..............................................11
      3.3. Refresh Token .............................................11
      3.4. Authorization "code" ......................................12
      3.5. Redirect URI ..............................................13
      3.6. "state" Parameter .........................................13
      3.7. Client Identifier .........................................13
   4. Threat Model ...................................................15
      4.1. Clients ...................................................16
           4.1.1. Threat: Obtaining Client Secrets ...................16
           4.1.2. Threat: Obtaining Refresh Tokens ...................17
           4.1.3. Threat: Obtaining Access Tokens ....................19
           4.1.4. Threat: End-User Credentials Phished Using
                  Compromised or Embedded Browser ....................19
           4.1.5. Threat: Open Redirectors on Client .................20
      4.2. Authorization Endpoint ....................................21
           4.2.1. Threat: Password Phishing by Counterfeit
                  Authorization Server ...............................21
           4.2.2. Threat: User Unintentionally Grants Too
                  Much Access Scope ..................................21
           4.2.3. Threat: Malicious Client Obtains Existing
                  Authorization by Fraud .............................22
           4.2.4. Threat: Open Redirector ............................22
      4.3. Token Endpoint ............................................23
           4.3.1. Threat: Eavesdropping Access Tokens ................23
           4.3.2. Threat: Obtaining Access Tokens from
                  Authorization Server Database ......................23