Problem with MIT Kerberos v1.4, OpenSSH 3.9p1 and Active Directory

Sam Evans wintrmte at
Thu Feb 10 17:15:11 EST 2005

> Do you have any more of the sshd trace?

I do.  Here is the trace from start to finish (using sshd -ddd):

-- START --
debug2: input_userauth_request: try method keyboard-interactive
debug1: keyboard-interactive devs
debug1: auth2_challenge: user=testuser devs=
debug1: kbdint_alloc: devices 'pam'
debug2: auth2_challenge_start: devices pam
debug2: kbdint_next_device: devices <empty>
debug1: auth2_challenge_start: trying authentication method 'pam'
debug3: mm_sshpam_init_ctx
debug3: mm_request_send entering: type 46
debug3: monitor_read: checking request 46
debug3: mm_answer_pam_init_ctx
debug3: mm_request_send entering: type 47
debug3: mm_request_receive entering
debug3: mm_sshpam_init_ctx: waiting for MONITOR_ANS_PAM_INIT_CTX
debug3: mm_request_receive_expect entering: type 47
debug3: mm_request_receive entering
debug3: mm_sshpam_init_ctx: pam_init_ctx failed
Failed keyboard-interactive for testuser from port 33336 ssh2
debug1: userauth-request for user testuser service ssh-connection
method password
debug1: attempt 5 failures 5
debug2: input_userauth_request: try method password
debug3: mm_auth_password entering
debug3: mm_request_send entering: type 10
debug3: monitor_read: checking request 10
debug1: temporarily_use_uid: 500/500 (e=0/0)
debug3: mm_auth_password: waiting for MONITOR_ANS_AUTHPASSWORD
debug3: mm_request_receive_expect entering: type 11
debug3: mm_request_receive entering
debug1: restore_uid: 0/0
debug1: Kerberos password authentication failed: ASN.1 encoding ended
debug1: krb5_cleanup_proc called
debug3: mm_answer_authpassword: sending result 0
debug3: mm_request_send entering: type 11
debug3: mm_auth_password: user not authenticated
Failed password for testuser from port 33336 ssh2
Failed password for testuser from port 33336 ssh2
debug3: mm_request_receive entering
Connection closed by
debug1: Calling cleanup 0x806d410(0x0)
debug1: Calling cleanup 0x8060f88(0x8090c50)
debug1: krb5_cleanup_proc called

-- END --

> Sounds like a big ticket problem.  We have seen problems with AFS
> (which has been reported and fixed in the CVS) when the ticket is big.
> I have not seen this, and just did a test with my 2003 AD user which
> is in too many groups. It worked fine with OpenSSH-3.9p1 with MIT krb5-1.4
> running on Solaris. But maybe my test user is not in enough groups to cause
> this problem.

I think this is exactly what is happening.  We have some users who are
members of hundreds of groups (don't ask me why, long overdrawn story)
which is likely causing the problem.

> The OpenSSH may be finding an older krb5 shared library, that has problems.
> Does it also have PAM? Is the pam_krb5 loading an old Kerberos?
> Does "ldd sshd" show that all new krb5 libs are being used?

Yes, it is pointing to the MIT Kerberos v1.4 library, so all should be
good there.

> If you run Ethereal, how big is the bad ticket vs the good ticket.

The bad ticket appears about about ~70 bytes larger than the working
one.  With an additional 2 continuation packets as compared to the 1
continuation for the working ticket.

I think it is likely the same issue that you ran into with large
ticket sizes.  Perhaps I will try the version of OpenSSH that's
currently in CVS.

Thanks for your help!


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