...Failed to authenticate for an unknown error: 28
...cs_password error: User test is not authenticated
...Call returned with error: 28

Caused by not linking the required library at build time on Linux.


Add -f <path to pam module> to the link part of the makefile
e.g. to add support for -f /lib/security/pam_unix_passwd.so
gcc -g -export-dynamic -f /lib/security/pam_unix_passwd.so

This issue should be fixed in 0.4. Use these instructions for 0.3   