Comment 2 for bug 1659592

Hi N-Ronny,
I have never debugged openvpn/pam in that regard myself.
But I hapened to find https://github.com/Yubico/yubico-pam/issues/26 which made me wonder.
The version is clearly older.

Now both (the yubico.so and openvpn) are build with -fstack-protector and -fstack-protector-strong.
https://launchpadlibrarian.net/294924689/buildlog_ubuntu-xenial-amd64.yubico-pam_2.24-1~ppa1~xenial1_BUILDING.txt.gz
https://launchpadlibrarian.net/236028083/buildlog_ubuntu-xenial-amd64.openvpn_2.3.10-1ubuntu2_BUILDING.txt.gz

One other thing you could do is enabling some other (than yubico) pam based auth for openvpn to at least sort out the question if it is yubico or openvpn where you need to look at.