OAuth 2.0 Integrity Verification for Authorization Requests (IVAR)
draft-fett-oauth-ivar-00

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Web Authorization Protocol                                       D. Fett
Internet-Draft                                                   yes.com
Intended status: Standards Track                              J. Bradley
Expires: January 24, 2020                                         Yubico
                                                           July 23, 2019

   OAuth 2.0 Integrity Verification for Authorization Requests (IVAR)
                        draft-fett-oauth-ivar-00

Abstract

   This document describes a mechanism for the integrity protection of
   OAuth 2.0 authorization requests.

Status of This Memo

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   Copyright (c) 2019 IETF Trust and the persons identified as the
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions and Terminology . . . . . . . . . . . . . . .   3
   2.  Concept . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Client Metadata for IVAR  . . . . . . . . . . . . . . . . . .   3
   4.  Protocol  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Storing the Authorization Request . . . . . . . . . . . .   4
     4.2.  IVAR Verification . . . . . . . . . . . . . . . . . . . .   4
   5.  Fallback if JavaScript is unavailable . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   A number of attacks on OAuth 2.0 are based on the fact that the
   contents of the OAuth authorization request lack integrity and
   authenticity protection.  To launch an attack, an attacker might, for
   example, start an OAuth flow in his browser, use the authorization
   request URI created by the client, and send it to its victim (with or
   without manipulations).  The victim might then complete the
   authorization.  Since the attacker knows or has manipulated parts of
   the authorization request URI, certain security mechanisms in OAuth
   might then not work as expected --- undermining the security of OAuth
   or protocols based on OAuth, like OpenID Connect.

   Among others, the following attacks are facilitated by the lack of
   integrity and authenticity of the authorization request:

   o  Attacks on the redirection URI, in which an attacker manipulates
      the redirection URI and let it point either to a server controlled
      by the attacker or an endpoint at the client which discloses
      contents of the authorization response to the attacker.

   o  The PKCE Chosen Challenge Attack, described in [arXiv.1901.11520],
      wherein an attacker uses his access to the authorization response
      (see attacker model A3 in [I-D.ietf-oauth-security-topics]) to
      gain access to the user's resources.

   o  A variant of the AS Mix-Up attack in which a malicious AS
      redirects the user to an honest AS, re-using request parameters.
      (See [arXiv.1601.01229] for details.)

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   While TLS protects the integrity of the authorization request, these
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