[Bug 988520] Re: After failed auth, subsequent auths in same context fail

[Russ Allbery]

Oh, wow, great job with the test case.  It wouldn't have occurred to me
to just do that.  (And yes, you have to use the Git version because I've
been adding a ton of new tests compared to the latest full release.)

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https://bugs.launchpad.net/bugs/988520

Title:
  After failed auth, subsequent auths in same context fail

Status in “krb5” package in Ubuntu:
  Triaged
Status in “krb5” package in Debian:
  Fix Released

Bug description:
  SRU Justification

  [Impact]

  If an authentication fails after preauth was requested, all subsequent
  preauth-required authentications in the same Kerberos context will
  also fail. This breaks password change when credentials have expired,
  and also breaks try_first_pass functionality in Kerberos PAM modules.

  [Development Fix]

  New upstream release. Updated in Debian. Pending sync in Ubuntu.
  Verified in Ubuntu manually.

  [Stable Fix]

  Upstream patch cherry-picked. Debdiff attached.

  [Test Case]

  testcase.sh attached.

  [Regression Potential]

  Low: one line patch for missing initialisation written by upstream.


  Original report by Russ Allbery:

  MIT Kerberos 1.10 (including pre-releases and betas) exposed a bug in
  the tracking of preauth mechanisms such that, if an authentication
  fails after preauth was requested, all subsequent preauth-required
  authentications in the same Kerberos context will also fail.

  This breaks password change when credentials have expired, and also
  breaks try_first_pass functionality in Kerberos PAM modules.

  Upstream has fixed this problem in their mainline with commit 25822.

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