[krbdev.mit.edu #8282] git commit

[Tom Yu via RT]

Fix SPNEGO context aliasing bugs [CVE-2015-2695]

The SPNEGO mechanism currently replaces its context handle with the
mechanism context handle upon establishment, under the assumption that
most GSS functions are only called after context establishment.  This
assumption is incorrect, and can lead to aliasing violations for some
programs.  Maintain the SPNEGO context structure after context
establishment and refer to it in all GSS methods.  Add initiate and
opened flags to the SPNEGO context structure for use in
gss_inquire_context() prior to context establishment.

CVE-2015-2695:

In MIT krb5 1.5 and later, applications which call
gss_inquire_context() on a partially-established SPNEGO context can
cause the GSS-API library to read from a pointer using the wrong type,
generally causing a process crash.  This bug may go unnoticed, because
the most common SPNEGO authentication scenario establishes the context
after just one call to gss_accept_sec_context().  Java server
applications using the native JGSS provider are vulnerable to this
bug.  A carefully crafted SPNEGO packet might allow the
gss_inquire_context() call to succeed with attacker-determined
results, but applications should not make access control decisions
based on gss_inquire_context() results prior to context establishment.

    CVSSv2 Vector: AV:N/AC:M/Au:N/C:N/I:N/A:C/E:POC/RL:OF/RC:C

[ghudson at mit.edu: several bugfixes, style changes, and edge-case
behavior changes; commit message and CVE description]

(cherry picked from commit b51b33f2bc5d1497ddf5bd107f791c101695000d)
(cherry picked from commit 31fb730f1ad708f230e4387e02ed2f89b93c3607)

https://github.com/krb5/krb5/commit/1ff9a2ee449b194c48b8e40e329293a442e4c55c
Author: Nicolas Williams <nico at twosigma.com>
Committer: Tom Yu <tlyu at mit.edu>
Commit: 1ff9a2ee449b194c48b8e40e329293a442e4c55c
Branch: krb5-1.13
 src/lib/gssapi/spnego/gssapiP_spnego.h |    2 +
 src/lib/gssapi/spnego/spnego_mech.c    |  254 ++++++++++++++++++++++++--------
 2 files changed, 192 insertions(+), 64 deletions(-)