cyberstrikeus 6.2.6 Ensure no duplicate GIDs exist (Automated)
Profile
- Level 1 - Server
- Level 1 - Workstation
Description
Although the groupadd program will not let you create a duplicate Group ID (GID), it is possible for an administrator to manually edit the /etc/group file and change the GID field.
Rationale
User groups must be assigned unique GIDs for accountability and to ensure appropriate access protections.
Audit Procedure
Command Line
Run the following script and verify no results are returned:
#!/usr/bin/env bash
{
while read -r l_count l_gid; do
if [ "$l_count" -gt 1 ]; then
echo -e "Duplicate GID: \"$l_gid\" Groups: \"$(awk -F: '($3 == n) { print $1 }' n=$l_gid /etc/group | xargs)\""
fi
done < <(cut -f3 -d":" /etc/group | sort -n | uniq -c)
}
Expected Result
No output should be returned.
Remediation
Command Line
Based on the results of the audit script, establish unique GIDs and review all files owned by the shared GID to determine which group they are supposed to belong to.
References
- NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5
Additional Information
You can also use the grpck command to check for other inconsistencies in the /etc/group file.
CIS Controls
- v8: 5.2 Use Unique Passwords
- v7: 4.4 Use Unique Passwords