Segfault when using pam_gate.so

[seren]

I'm testing pam_gate.so on Ubuntu 14.04.5, and am getting segfaults:

$ sudo ls
[sudo] password for testuser:
Segmentation fault (core dumped)

This shows up in the syslog:

Aug  4 17:53:00 vpn-test2 kernel: [255650.618605] sudo[3775]: segfault at 0 ip 00007fc20776b467 sp 00007ffca3de53b0 error 4 in libc-2.19.so[7fc20772e000+1be000]

and then 2 minutes later this:

Aug  4 17:55:01 vpn-test2 kernel: [255771.640580] cron[3777]: segfault at 0 ip 00007f259d9123e8 sp 00007ffd676137b0 error 4 in pam_gate.so[7f259d911000+3000]

Interestingly, this doesn't segfault when the password is incorrect:

$ sudo ls
[sudo] password for testuser:
Sorry, try again.
[sudo] password for testuser:
Sorry, try again.
[sudo] password for testuser:
Sorry, try again.
sudo: 3 incorrect password attempts

My testing setup process (adapted from the setup.sh script) is:

$ apt-get update >/dev/null

$ apt-get install -y libpam0g-dev libcurl4-gnutls-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
libcurl4-gnutls-dev is already the newest version.
libpam0g-dev is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 28 not upgraded.

$ make
cc -Werror -Wall -o check_gate src/check_gate.c -lpam -lpam_misc
cc -Werror -Wall -fPIC -shared -Xlinker -x -o pam_gate.so src/pam_gate.c -lcurl

$ cp pam_gate.so /lib/*-linux-gnu/security/

$ cp pam_gate.so /lib/*-linux-gnu/

$ echo "auth sufficient pam_gate.so url=http://localhost:3000/profile/authenticate_pam" >> /etc/pam.d/common-auth
$ echo "account sufficient pam_gate.so" >> /etc/pam.d/common-auth

[theRustyKnife]

I ran into this issue as well and after some investigation I came to the following conclusion:

In src/pam_gate.c on line 260, there is a call to atoi where the parameter is not checked for NULL values. That, for some reason, is not throwing any meaningful error, but segfaulting instead.
What I did to fix it was changing the line from

pMinUserId = atoi(getArg("min_user_id", argc, argv));

to

const char *tmpPMinUserId = getArg("min_user_id", argc, argv);
pMinUserId = (tmpPMinUserId == NULL) ? 0 : atoi(tmpPMinUserId);

That being said, I have no idea if this is actually correct as I don't really know what pMinUserId means... It seems to work tho.

EDIT: Ok, I'm still getting segfaults, just on a different occasion. Also, this got thrown at me once:

shell-init: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
sh: 0: getcwd() failed: No such file or directory

EDIT2: Now I can't reproduce the second segfault again. I have no idea what's going on here...