Yes, PAM authentication seems to work as expected after applying the patch. I have not encountered any additional issues, but I did not conduct a full audit of the module for additional type issues.

I would love to see the patch included. Thanks!

The following patch seems to have fixed the issue for me:

--- /usr/lib/python3.6/site-packages/cobbler/modules/authentication/pam.py.orig	2020-08-24 22:12:16.178380466 +0000
+++ /usr/lib/python3.6/site-packages/cobbler/modules/authentication/pam.py	2020-08-24 22:19:34.634209255 +0000
@@ -124,7 +124,7 @@
         p_response[0] = cast(addr, POINTER(PamResponse))
         for i in range(n_messages):
             if messages[i].contents.msg_style == PAM_PROMPT_ECHO_OFF:
-                pw_copy = STRDUP(str(password))
+                pw_copy = STRDUP(password.encode())
                 p_response.contents[i].resp = cast(pw_copy, c_char_p)
                 p_response.contents[i].resp_retcode = 0
         return 0
@@ -138,7 +138,7 @@
 
     handle = PamHandle()
     conv = PamConv(my_conv, 0)
-    retval = PAM_START(service, username, pointer(conv), pointer(handle))
+    retval = PAM_START(service.encode(), username.encode(), pointer(conv), pointer(handle))
 
     if retval != 0:
         # TODO: This is not an authentication error, something

Describe the bug

<!--- A clear and concise description of what the bug is. -->

<!--- HINT: You can paste gist.github.com links for long logs or larger files --> Enabling authentication.pam module results in TypeError exception and failure to authenticate.

To Reproduce

1. Change authentication module to "authentication.pam" in modules.com
2. Restart cobbler service
3. Attempt to login via web UI
4. See error in cobbler.log

DEBUG | authn_pam: PAM service is login
INFO | Exception occured: <class 'ctypes.ArgumentError'>
INFO | Exception value: argument 1: <class 'TypeError'>: wrong type
INFO | Exception Info:
  File "/usr/lib/python3.6/site-packages/cobbler/remote.py", line 3477, in _dispatch
    return method_handle(*params)

  File "/usr/lib/python3.6/site-packages/cobbler/remote.py", line 3233, in login
    if self.__validate_user(login_user, login_password):

  File "/usr/lib/python3.6/site-packages/cobbler/remote.py", line 3113, in __validate_user
    return self.api.authenticate(input_user, input_password)

  File "/usr/lib/python3.6/site-packages/cobbler/api.py", line 1599, in authenticate
    rc = self.authn.authenticate(self, user, password)

  File "/usr/lib/python3.6/site-packages/cobbler/modules/authentication/pam.py", line 141, in authenticate
    retval = PAM_START(str(service), str(username), pointer(conv), pointer(handle))

Expected behavior

<!--- A clear and concise description of what you expected to happen. --> PAM authentication should succeed.

Version

<!--- Paste output from cobbler version -->

Cobbler 3.1.2
  source: ?, ?
  build time: Sun May 31 02:32:34 2020

Screenshots

<!--- If applicable, add screenshots to help explain your problem. -->

Additional context

<!--- Add any other context about the problem here. -->