pam_usermatch is a Linux PAM module which provides a way to verify username against a regular expression that follows Egrep POSIX grammar.
If username matches the regular expression and the second argument is "allow", it succeeds.
If username does not matches the regular expression and the second argument is "deny", it succeeds.
On success it returns PAM_SUCCESS, otherwise it returns PAM_AUTH_ERR, PAM_SERVICE_ERR, PAM_BUF_ERR or PAM_PERM_DENIED.
No credentials are awarded by this module.
The source program is a single C++11(and newer) file.
Requires: pam-devel
g++ pam_usermatch.cpp -o pam_usermatch.so -shared -lpam -fPICpam_usermatch <reg_exp> allow|deny
Note that the reg_exp argument should be surrounded with square brackets if there are space, '[' or ']' characters included in it, and a ']' character should be written as '\]'. For more details please refer to Linux-PAM Manual.
Examples:
auth requisite pam_usermatch.so [^[a-z0-9_\.-\]{2,30}$] allow
auth requisite pam_usermatch.so \.(com|net|org)$ deny
pam_usermatch is licensed under the GPLv3 license.