Dovecot-imapd, PAM auth., krb auth with non-krb user causes crash

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please try to obtain a backtrace following the instructions at http://wiki.ubuntu.com/DebuggingProgramCrash and upload the backtrace (as an attachment) to the bug report. This will greatly help us in tracking down your problem.

Hi Chuck,

I have done backtraces before, but this one was a little more unusual for me. The last time I needed a backtrace, I was able to capture the daemon's full command line, then run it through GDB. In this case, I'm thinking the offending program is located at /usr/lib/dovecot/dovecot-auth, it is run by the dovecot daemon as needed, and then exits with a result (or, in this case, a crash) shortly after starting.

In this case, I stopped dovecot, sudo-ed into root, ran `ulimit -c unlimited`, ran dovecot manually, and had my IMAP client try a login. That caused dovecot-auth to die again (as expected), and dropped a core file in /var/run/dovecot. I installed both dovecot-common-dbgsym and libpam0g-dbgsym packages, ran `gdb /usr/lib/dovecot/dovecot-auth core`, and then ran the 5 GDB commands requested in https://wiki.ubuntu.com/Backtrace. Attached are the results!

Hmmmm, looks like I needed a couple more debug packages. Here's the GDB file again after installing libcomerr2-dbgsym, libpam-heimdal-dbgsym, and libkrb5-22-heimdal-dbgsym.

Thanks for the info.

Regards
chuck

Hi,

You went me from a 6.06 -> 8.04 directly?

Regards
chuck

Hello!

When I got the machine, I installed Ubuntu 6.06.1 LTS. From time to time, I installed additional packages, including Dovecot. Also from time to time, I'd do `apt-get update` followed by `apt-get upgrade`. Then, on 6 August, I ran:

apt-get update
apt-get install update-manager-core
do-release-upgrade

(I already had the dapper-updates repository in my APT sources.list when I did this)

I ran those commands based on the instructions at <https://help.ubuntu.com/community/HardyUpgrades#Network%20Upgrade%20from%206.06%20for%20Ubuntu%20Servers%20(Recommended)>.

I think this might be more of a pam problem.

Thanks
chuck

No, this segfault is happening in a specific PAM module, nothing to do with PAM itself. Reassigning to heimdal.

Hello again!

I've got another twist on this bug! Last night, I tried logging into a machine that is showing this problem. I was logging in using SSH, using the PuTTY Windows SSH client. At the time I made the connection, I entered the wrong username by mistake, but I did not catch my mistake until I had finished entering my password. After entering the password, PuTTY just sat for a while, waiting, and then reported that the remote side had closed the connection.

Once I got back into work, I did a test with this on my workstation (also running Ubuntu Hardy, fully up-to-date), and I discovered the following: If you have PAM configured to use Heimdal's pam_krb5.so module, and you try to log in with an invalid username, openssh-server's sshd will crash in the same place as dovecot-imapd.

Since I did the verification on my Linux workstation, I had apport running, and it grabbed a crash report. I processed the crash report with `appport-cli -c` and saved the report, so it has the core dump AND all of the information that is derived from the core dump. I really hope this extra info helps!

I wonder if this is a symbols clash - dovecot and sshd are both linked against MIT libkrb5. Your pam_krb5.so is linked against Heimdal's krb5 library, which has some overlapping symbols.

The version of Heimdal in hardy didn't yet use symbol versioning. It'd be interesting to hear if you can reproduce this with natty or later.