6.2.16 Ensure no duplicate UIDs exist (Scored)

Level 1 - Server
Level 1 - Workstation 

Although the useradd program will not let you create a duplicate User ID (UID), it is possible for an administrator to manually edit the /etc/passwd file and change the UID field.

Users must be assigned unique UIDs for accountability and to ensure appropriate access protections.

Run the following script and verify no results are returned:

#!/bin/bash
cat /etc/passwd | cut -f3 -d":" | sort -n | uniq -c | while read x ; do
  [ -z "${x}" ] && break 
  set - $x 
  if [ $1 -gt 1 ]; then 
    users=`awk -F: '($3 == n) { print $1 }' n=$2 /etc/passwd | xargs` 
    echo "Duplicate UID ($2): ${users}" 
  fi 
done

Based on the results of the audit script, establish unique UIDs and review all files owned by the shared UIDs to determine which UID they are supposed to belong to.