Ubuntu 24.04: Implement rule 5.4.2.2 Ensure root is the only GID 0 account

controls/cis_ubuntu2404.yml

@@ -2134,10 +2134,12 @@ controls:
     levels:
       - l1_server
       - l1_workstation
-    related_rules:
+    rules:
       - accounts_root_gid_zero
-    status: planned
-    notes: TODO. Partial/incorrect implementation exists.See related rules. Analogous to ubuntu2204/5.5.3.
+    status: automated
+    notes: |
+      The remediation is not automated as the removal or modification
+      of group IDs from a system is too disruptive.
 
   - id: 5.4.2.3
     title: Ensure group root is the only GID 0 group (Automated)

linux_os/guide/system/accounts/accounts-restrictions/root_logins/accounts_root_gid_zero/oval/shared.xml

@@ -1,12 +1,15 @@
 <def-group>
   <definition class="compliance" id="{{{rule_id}}}" version="1">
     {{{ oval_metadata("The root account should have primary group of 0") }}}
-    <criteria>
+    <criteria operator="AND">
       <criterion comment="tests that the root account's gid is equal to 0" test_ref="test_{{{rule_id}}}" />
+      {{% if 'ubuntu' in product %}}
+      <criterion comment="no other users have primary group ID 0" test_ref="test_{{{rule_id}}}_no_other_gid_0" />
+      {{% endif %}}
     </criteria>
   </definition>
 
-  <ind:textfilecontent54_test id="test_{{{rule_id}}}" check="all" comment="test that there are no accounts with UID 0 except root in the /etc/passwd file" version="1">
+  <ind:textfilecontent54_test id="test_{{{rule_id}}}" check="all" comment="test that the root user has GID 0 in the /etc/passwd file" version="1">
     <ind:object object_ref="object_{{{rule_id}}}" />
     <ind:state state_ref="state_{{{rule_id}}}" />
   </ind:textfilecontent54_test>
@@ -20,4 +23,17 @@
   <ind:textfilecontent54_state id="state_{{{rule_id}}}" version="1" comment="root account's gid is equal to 0">
     <ind:subexpression operation="equals" datatype="int">0</ind:subexpression>
   </ind:textfilecontent54_state>
+
+  {{% if 'ubuntu' in product %}}
+  <!-- Test for other users with GID 0 (excluding sync, shutdown, halt, operator) -->
+  <ind:textfilecontent54_test id="test_{{{rule_id}}}_no_other_gid_0" check="all" check_existence="none_exist" comment="test that there are no other accounts with GID 0 except root" version="1">
+    <ind:object object_ref="object_{{{rule_id}}}_no_other_gid_0" />
+  </ind:textfilecontent54_test>
+
+  <ind:textfilecontent54_object id="object_{{{rule_id}}}_no_other_gid_0" version="1">
+    <ind:filepath>/etc/passwd</ind:filepath>
+    <ind:pattern operation="pattern match">^(?!\b(root|sync|shutdown|halt|operator)\b).+:.+:\d+:0:.+$</ind:pattern>
+    <ind:instance datatype="int">1</ind:instance>
+  </ind:textfilecontent54_object>
+  {{% endif %}}
 </def-group>

linux_os/guide/system/accounts/accounts-restrictions/root_logins/accounts_root_gid_zero/tests/correct_value.pass.sh

@@ -1,2 +1,6 @@
 #!/bin/bash
 # remediation = none
+
+{{% if 'ubuntu' in product %}}
+awk -F: '$4 == 0 && $1 !~ /^(root|sync|shutdown|halt|operator)$/ {print $1}' /etc/passwd | xargs --no-run-if-empty -I '{}' userdel -f '{}'
+{{% endif %}}

linux_os/guide/system/accounts/accounts-restrictions/root_logins/accounts_root_gid_zero/tests/other_user_uid_0.fail.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# Remediation doesn't fix the rule, only locks passwords
+# of non-root accounts with uid 0.
+# remediation = none
+
+useradd --gid 0 root2