user - Prevent user fact lookup failure if LOGNAME is set (#17029) (#73439)

The `UserFactCollector` queries the user login name via
`getpass.getuser()` and looks up the corresponding entry
in the password database.
The login name may differ from the actual user name,
eg. if the `LOGNAME` env variable is set. The lookup
fails in this case. Added a fallback in this case that
tries to get the entry via the user ID.

changelogs/fragments/17029-prevent-user-fact-lookup-failure-is-logname-is-set.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - Lookup user by UID in password database if login name is not found (https://github.com/ansible/ansible/issues/17029)

lib/ansible/module_utils/facts/system/user.py

@@ -35,7 +35,10 @@ class UserFactCollector(BaseFactCollector):
 
         user_facts['user_id'] = getpass.getuser()
 
-        pwent = pwd.getpwnam(getpass.getuser())
+        try:
+            pwent = pwd.getpwnam(getpass.getuser())
+        except KeyError:
+            pwent = pwd.getpwuid(os.getuid())
 
         user_facts['user_uid'] = pwent.pw_uid
         user_facts['user_gid'] = pwent.pw_gid

test/units/module_utils/facts/system/test_user.py

@@ -0,0 +1,40 @@
+# unit tests for ansible system lsb fact collectors
+# -*- coding: utf-8 -*-
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# Make coding more python3-ish
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+from ansible.module_utils.facts.system.user import UserFactCollector
+
+import os
+
+
+def test_logname():
+    """ Test if ``UserFactCollector`` still works with LOGNAME set """
+    collector = UserFactCollector()
+
+    unmodified_facts = collector.collect()
+    # Change logname env var and check if the collector still finds
+    # the pw entry.
+    os.environ["LOGNAME"] = "NONEXISTINGUSERDONTEXISTPLEASE"
+    modified_facts = collector.collect()
+
+    # Set logname should be different to the real name.
+    assert unmodified_facts['user_id'] != modified_facts['user_id']
+    # Actual UID is the same.
+    assert unmodified_facts['user_uid'] == modified_facts['user_uid']