PAM modules; pthreads not reliably dispatching background threads :(.

[Jan Bramkamp]

On 09.02.20 12:25, Dr Josef Karthauser wrote:
> Hi Folks,
>
> Has anyone got any experience with PAM and pthreads?
>
> We’re using a 2FA module (pam_yubico https://www.freebsd.org/cgi/man.cgi?query=pam_yubico&sektion=8 <https://www.freebsd.org/cgi/man.cgi?query=pam_yubico&sektion=8>).
>
> It’s proving unreliable. Digging deeper it uses libcurl to communication to an HTTP endpoint, and libcurl is using pthreads for to make asynchronous DNS lookup requests.
>
> It seems that the pthreads are not being handled reliably within the PAM runtime context - the background threads do not complete or dispatch. It’s very strange.
>
> The problem doesn’t happen if we use the same code running from a user land process. The pthreads are reliably in this context.
>
> Is there a known issue with PAM and pthreads? Hints are that there are (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=214540 <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=214540>). But that problem was reported 3 years ago!
>
> HELP!
>
> If you know something I’d really appreciate a steer!
Is the "host" process multithreaded or at least built with Pthread support?