PH49311: TLS1.3 CLIENT AUTHENTICATION FAILURES WITH RECENT GNUTLS CLIENTS

APAR status

• Closed as program error.

Error description

• When client authentication is used with TLS 1.3, recent
  GNUTLS-based clients may return a fatal error when IHS sends a
  mid-handshake CertificateRequest message with a non-zero length
  "context"
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of IBM HTTP Server with client    *
  *                  authentication enabled.                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: When TLS client authentication is       *
  *                      enabled, some clients may fail to       *
  *                      handshake over TLS                      *
  *                      1.3.                                    *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When TLS client authentication is used over TLS 1.3, the
  CertificateRequest message sent by the server
  should have a zero-length "Context" field if sent during the
  initial handshake and a non-zero length
  "Context" field when sent post-handshake.
  IHS only ever sends CertificateRequest messages during the
  handshake, never after.
  GSKit versions prior to 8.0.55.29 always send a non zero-length
  "Context" field when the client supports
  post handshake authentication, even if the server is not using
  it.
  Recent builds of the GNUTLS library fail when the context is
  unexpectedly non-empty.
  

Problem conclusion

• The included level of the IBM GSKit library was updated to
  8.0.55.29 or later, which includes a fix to send the empty
  "Context" parameter during mid-handshake CertificateRequest
  messages.
  
  Note: This cumulative GSKit update occurs in 8.5.5 as well, even
  though the problem described in this APAR cannot be reached in
  IHS 8.5.5 due to TLS 1.3 not being supported.
  
  The fix for this APAR is targeted for inclusion in IBM HTTP
  Server fix packs 8.5.5.23 and 9.0.5.14. 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

  IBM HTTP SERVER

• Fixed component ID

  5724J0801

Applicable component levels