[krbdev.mit.edu #8598] git commit

[Greg Hudson via RT]

Preserve GSS context on init/accept failure

After gss_init_sec_context() or gss_accept_sec_context() has created a
context, don't delete the mechglue context on failures from subsequent
calls, even if the mechanism deletes the mech-specific context (which
is allowed by RFC 2744 but not preferred).  Check for union contexts
with no mechanism context in each GSS function which accepts a
gss_ctx_id_t.

CVE-2017-11462:

RFC 2744 permits a GSS-API implementation to delete an existing
security context on a second or subsequent call to
gss_init_sec_context() or gss_accept_sec_context() if the call results
in an error.  This API behavior has been found to be dangerous,
leading to the possibility of memory errors in some callers.  For
safety, GSS-API implementations should instead preserve existing
security contexts on error until the caller deletes them.

All versions of MIT krb5 prior to this change may delete acceptor
contexts on error.  Versions 1.13.4 through 1.13.7, 1.14.1 through
1.14.5, and 1.15 through 1.15.1 may also delete initiator contexts on
error.

(cherry picked from commit 56f7b1bc95a2a3eeb420e069e7655fb181ade5cf)

https://github.com/krb5/krb5/commit/3659e55443962a50fdbe564bc5333e32dafd22f9
Author: Greg Hudson <ghudson at mit.edu>
Commit: 3659e55443962a50fdbe564bc5333e32dafd22f9
Branch: krb5-1.15
 src/lib/gssapi/mechglue/g_accept_sec_context.c  |   22 +++++++++++++++-------
 src/lib/gssapi/mechglue/g_complete_auth_token.c |    2 ++
 src/lib/gssapi/mechglue/g_context_time.c        |    2 ++
 src/lib/gssapi/mechglue/g_delete_sec_context.c  |   14 ++++++++------
 src/lib/gssapi/mechglue/g_exp_sec_context.c     |    2 ++
 src/lib/gssapi/mechglue/g_init_sec_context.c    |   19 +++++++++++--------
 src/lib/gssapi/mechglue/g_inq_context.c         |    2 ++
 src/lib/gssapi/mechglue/g_prf.c                 |    2 ++
 src/lib/gssapi/mechglue/g_process_context.c     |    2 ++
 src/lib/gssapi/mechglue/g_seal.c                |    4 ++++
 src/lib/gssapi/mechglue/g_sign.c                |    2 ++
 src/lib/gssapi/mechglue/g_unseal.c              |    2 ++
 src/lib/gssapi/mechglue/g_unwrap_aead.c         |    2 ++
 src/lib/gssapi/mechglue/g_unwrap_iov.c          |    4 ++++
 src/lib/gssapi/mechglue/g_verify.c              |    2 ++
 src/lib/gssapi/mechglue/g_wrap_aead.c           |    2 ++
 src/lib/gssapi/mechglue/g_wrap_iov.c            |    8 ++++++++
 17 files changed, 72 insertions(+), 21 deletions(-)