Cis GCP Cos 6.2.10

6.2.10 Ensure users' dot files are not group or world writable (Automated)

Description

While the system administrator can establish secure permissions for users' "dot" files, the users can easily override these.

Rationale

Group or world-writable user configuration files may enable malicious users to steal or modify other users' data or to gain another user's system privileges.

Audit Procedure

Run the following script and verify no results are returned:

#!/bin/bash

grep -E -v '^(halt|sync|shutdown)' /etc/passwd | awk -F: '($7 != "'"$(which nologin)"'" && $7 != "/bin/false") { print $1 " " $6 }' | while read user dir; do
  if [ ! -d "$dir" ]; then
    echo "The home directory ($dir) of user $user does not exist."
  else
    for file in $dir/.[A-Za-z0-9]*; do
      if [ ! -h "$file" -a -f "$file" ]; then
        fileperm=$(ls -ld $file | cut -f1 -d" ")

        if [ $(echo $fileperm | cut -c6)  != "-" ]; then
          echo "Group Write permission set on file $file"
        fi
        if [ $(echo $fileperm | cut -c9)  != "-" ]; then
          echo "Other Write permission set on file $file"
        fi
      fi
    done
  fi
done

Expected Result

No results should be returned.

Remediation

Making global modifications to users' files without alerting the user community can result in unexpected outages and unhappy users. Therefore, it is recommended that a monitoring policy be established to report user dot file permissions and determine the action to be taken in accordance with site policy.

Additional Information

On some distributions the /sbin/nologin should be replaced with /usr/sbin/nologin.

CIS Controls

Profile

• Level 2 - Server