Audit in OAuth 2.0
draft-tsitkov-oauth-audit-01

Network Working Group                                   Zh. Tsitkov, Ed.
Internet-Draft                                                       MIT
Intended status: Informational                          December 8, 2014
Expires: June 11, 2015

                           Audit in OAuth 2.0
                      draft-tsitkov-oauth-audit-01

Abstract

   This specification is an effort to provide guidelines for
   implementing the Audit functionality for OAuth 2.0 enabled
   environments.  The data of interest for the OAuth 2.0 audit includes
   scopes, permissions, policies and other authorization and
   authentication related information.  It can be used by resource and
   authorization servers for detecting security-related problems in real
   time and fast violation response, or by government agencies and
   various institutions for after-the-fact forensic and compliance
   analysis.

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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  Audit ID  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Audit log parameters  . . . . . . . . . . . . . . . . . . . .   4
   5.  Event selection . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Audit vs privacy  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Issues  . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   This specification is an effort to provide guidelines for
   implementing the Audit functionality for OAuth 2.0 [OAuth2] enabled
   environments.  The data of interest for the OAuth 2.0 audit includes
   permissions, scopes, policies and other authorization and
   authentication related information.  It can be used by resource and
   authorization servers for intrusion detection and fast violation
   response, or by government agencies and businesses for forensic
   analysis, verification of legal compliances, and similar purposes.

   The intention of this specification is:

   o  to address the quality of the content of audit logs.  This is done
      by identifying the mandatory, recommended and optional auditable
      information from the OAuth 2.0 perspective;

   o  to improve audit trails processing.  This is achieved by
      introducing an audit identifier that simplifies log querying;

   o  to encourage all OAuth 2.0 participants to securely store and
      protect information that is useful for the audit.

   The goal of this proposal is to provide a high quality feed to
   various audit processing facilities.  Identifying mechanisms of how
   the logs are processed is outside the scope of this document.  It can
   be done dynamically, and, for example, trigger that tokens to be
   revoked.  It can be done by resource owner's Audit Agent.  It can be
   done off-line when audit analysis is performed.

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2.  Notational Conventions

   The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
   'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
   document are to be interpreted as described in [RFC2119].

   Unless otherwise noted, all the protocol properties and values are
   case sensitive.

3.  Audit ID

   To optimize audit log handling this document introduces an identifier
   Audit ID (audit_id) with the following properties:

   o  It is unique and stays unchanged for a given OAuth 2.0 end-to-end
      communication;

   o  It is generated as part of OAuth 2.0 processing;

   o  It is protected against data tampering;

   o  It is available to all OAuth 2.0 participants to be recorded for
      their audit needs;

   The audit_id becomes useful when, for example, one of the OAuth 2.0
   participants (most likely resource server or authorization server)
   suspects some malicious activity.  It can then request the other
   participants to provide information from their audit logs that
   corresponds to the particular audit_id and, based on the acquired
   information, perform further analysis of the suspected attack and
   take an action to address the problem.  Alternatively, suspecting
   party can issue warning to the other participants about the
   suspicious activity associated with the particular audit_id.

   In addition, in more static use-case, such as security problem
   examination involving the reconstruction of events, the audit
   identifier makes it possible and simple to find out who was
   responsible for the violation, whether it was due to resource
   registration or misinterpreting the policies, implementation flaws,
   etc.

   The audit identifier can be an alphanumeric string, or a JSON
   structure.  It can be randomly generated, or constructed out of some
   unique parameters, such as "state" request parameter, components of
   the tokens, session ids, timestamps.

   The uniqueness of the audit_id is important especially in the cases
   when audit logs are processed dynamically.  Since randomizers on

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   clients or resource server's (RS) are commonly weaker and less
   collision-resistant when compared to authorization server's (AS)
   randomizers, in most environments, it should be the responsibility of
   AS to generate a high quality "strong" audit id.  However, it should
   be allowed for the client or resource server to have their own audit
   id's for internal bookkeeping.  These identifiers can be passed to
   the authorization server as part of the initial request and AS should
   include it in the reply messages together with the "strong" AS-
   selected audit identifier.

   Authorization server may adopt any audit identifier coming from the
   outside of AS as a "strong" audit ID if it believes that it is a high
   quality identifier.

   It is desirable for resource server, client and authorization server
   to record audit related information for all communications, at least
   for the mandatory set of parameters.  It makes analysis of audit
   trails more effective.

4.  Audit log parameters

   It is considered a good practice to keep the audit trails concise.
   Overloading logs with unnecessary information comes with the burden
   of extra storage allocation and protection, and less effective
   information processing (both time-wise and resource-wise).

   The following are the recommended parameters that, when applicable,
   should be included in the OAuth 2.0 audit logs for AS, RS and client.
   All security or privacy sensitive information should be either
   stripped and not logged or, alternatively, encrypted to preserve
   confidentiality.  The implementers have the opportunity to customize
   audit logs by extending auditable parameters and events.

   The following should be considered as mandatory parameters:

   audit_id
         Non-modifiable identifier that is used to track all
         participants on all stages of the OAuth 2.0 communication;

   event_type
         Type of event.  For example, "User consent";

   timestamp
         Timestamp when event occurred;

   event_outcome
         Indicates whether the event is reported on success or failure;

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   endpoint_uri
         URI of the authorization server;

   source
         Code specifying the type of source where event originated.

   client_id
         Unique identifier created for this client during registration;

   state
         Local "state" parameter provided by client in the authorization
         request (if applicable);

   resource_id
         Unique resource server identifier;

   redirect_uri
         URI used for access token;

   The following should be considered as optional parameters:

   event_category
         Type of action performed when audit is generated.  For example,
         "resource server processing";

   grand_type
         Type of grant that was used;

   requested_scopes
         Full list of the requested scopes;

   granted_scopes
         List of the granted scopes;

   token_status
         Full token status, including its value, type, validity periods,
         refresh token value.

   policies
         Policies that affected authorization decision.

   The content of the audit logs can be configurable.  If, for example,
   the performance or storage are a concern, the administrator may
   choose to log only basic mandatory information.  However, if this is
   not the case, or under violation alert, more detailed audit
   information may be useful.  In this case the administrator may switch
   the audit configuration from the basic level to the detailed.  There
   should be well defined mandatory set of parameters.

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5.  Event selection

   In general, all interections between authorization server, resource
   server, resource owner and client, successful or not, should be
   recorded in the audit log files.  This includes permission requests,
   token issuance, token introspection, etc.

6.  Audit vs privacy

   Privacy and auditing are closely related.  As it has been discussed
   in [Privacy-Considerations], audit trail can help to identify the
   misuse of information, such as unauthorized secondary use of data.
   On the other hand, stored audit logs may be compromised, data can be
   collected and analyzed.  To address the privacy risks one should make
   sure that the audit system is well protected, simple, transparent,
   and unambiguous.  Generally, audit designers should minimize the
   exposure of privacy related information in the logs.  Also, it should
   always be clear, if the audit logs are jeopardized, what privacy
   related information has leaked.

   One should notice, that introducing audit_id into audit log in OAuth
   2.0 enabled environments does not add any privacy related risks.

7.  IANA Considerations

   This document makes no request of IANA.

8.  Acknowledgments

   TBD

9.  Issues

10.  Normative References

   [OAuth2]   Hardt, D., "The OAuth 2.0 Authorization Framework",
              October 2012, <http://tools.ietf.org/html/rfc6749>.

   [Privacy-Considerations]
              Cooper, A., "Privacy Considerations for Internet
              Protocols", July 2013,
              <http://tools.ietf.org/html/rfc6973>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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Author's Address

   Zhanna Tsitkov (editor)
   MIT

   Email: tsitkova@mit.edu

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