PH47272: OIDC: DYNAMICALLY CHOOSE SIGATURE ALGORITHM INSTEAD OF REQUIRING A FIXED VALUE

APAR status

• Closed as program error.

Error description

• With the OpenID Connect (OIDC) Trust Association Interceptor
  (TAI), you currently must to hardcode the signature algorithm
  that is used to validate the ID token for the OIDC relying
  party (RP) or the JWT for JWT Authentication.  This causes
  usability problems with users, especially with the RP, which is
  defaulting to the less-used HS256 algorithm.
  
  The signature algorithm used to sign the token is in the
  object header.  The OIDC TAI should be able to use this
  signature algorithm for verification.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of IBM WebSphere Application      *
  *                  Server                                      *
  *                  and the OIDC TAI.                           *
  ****************************************************************
  * PROBLEM DESCRIPTION: The OIDC TAI requires that you hardcode *
  *                      the signature algorithm that is used to *
  *                      verify tokens.                          *
  ****************************************************************
  * RECOMMENDATION:  Install a fix pack or interim fix that      *
  *                  includes this APAR.                         *
  ****************************************************************
  The OIDC requires that you hardcode the
  provider_(id).signatureAlgorithm property. This causes
  usability problems with users, especially with the RP, which is
  defaulting to the less-used HS256 algorithm.
  This scheme also requires code update each time a new signature
  algorithm is required.
  

Problem conclusion

• The OIDC TAI is updated to dynamically choose the signature
  algorithm that is used to verify the ID token and JWT signature
  based on the header in the token.  This is controlled by setting
  signatureAlgorithm to HEADER.  The default setting for the
  provider_(id).signatureAlgorithm property is updated to be
  HEADER.
  
  As part of this APAR, an allow list and deny list are be added
  to give the administrator the option of using the algorithm in
  the header, but disallowing a set of algorithms, or only
  allowing a specific set of algorithms.
  
  Because HS256 is not secure, in most cases, HS256 is added to
  the deny list by default.
  
  ===================
  Updated properties:
  
  ==============================
  provider_(id).signatureAlgorithm
  
  Values:
  none
  HS256
  RS256
  RS512
  HEADER (default)
  
  Description:
  Specifies the algorithm that is used to secure messages from the
  OpenID Connect provider.  When this property is set to HEADER,
  the value is obtained from the header of each inbound token.
  
  ==============================
  provider_<id>.discoveryEndpointUrl
  
  The signatureAlgorithm property is no longer in the list of
  properties obtained from the discovery result.
  
  ===============
  New properties:
  
  ==============================
  provider_(id).signatureAllowList
  
  Values:
  You can specify a comma-separated list of signature algorithms.
  This property does not have a default value.
  
  Description:
  Specifies a comma separated list of signature algorithms that
  are allowed to secure messages from the OpenID Connect provider.
  If the provider_(id).signatureAlgorithm property is set to a
  value other than HEADER, this property is ignored.  A value
  cannot be provided for both this property and the
  provider_(id).signatureDenyList property.  This list can include
  any value that is supported by the jose4j open source project
  except HS256.  Besides ensuring that the HS256 signature
  algorithm is not in the list, the values for this property are
  not validated by the OIDC TAI.
  
  ==============================
  provider_(id).signatureDenyList
  
  Values:
  You can specify a comma-separated list of signature algorithms.
  See the description for the default value.
  
  Description:
  Specifies a comma separated list of signature algorithms that
  are not allowed to secure messages from the OpenID Connect
  provider.  If the provider_(id).signatureAlgorithm property is
  set to a value other than HEADER, this property is ignored.  A
  value cannot be provided for both this property and the
  provider_(id).signatureAllowList property.  This list can
  include any value that is supported by the jose4j open source
  project and the values are not validated by the OIDC TAI.
  
  The HS256 algorithm is not secure and we want to disallow it by
  default.  However, since the default for the OIDC RP was
  originally HS256, but it is now HEADER, this property cannot
  be defaulted to HS256 absolutely.
  
  If the configured list does not include HS256, HS256 is added to
  the list if any of the following conditions are true:
  
  * The provider_(id).useJwtFromRequest property is set to
  required.
  * The provider_(id).signatureAlgorithm property is set to
  HEADER.
  * Discovery is in use and HS256 is the only value for the
  id_token_signing_alg_values_supported claim in the OP's
  discovery result.
  
  The fix for this APAR is targeted for inclusion in fix pack
  8.5.5.23 and 9.0.5.13. For more information, see 'Recommended
  Updates for WebSphere Application Server':
  https://www.ibm.com/support/pages/node/715553
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  WEBS APP SERV N

• Fixed component ID

  5724H8800

Applicable component levels