Cis Ubuntu2004 V300 5 4 2 5

5.4.2.5 Ensure root path integrity (Automated)

Profile

• Level 1 - Server
• Level 1 - Workstation

Description

The root user can execute any command on the system and could be fooled into executing programs unintentionally if the PATH is not set correctly.

Rationale

Including the current working directory (.) or other writable directory in root's executable path makes it likely that an attacker can gain superuser access by forcing an administrator operating as root to execute a Trojan horse program.

Audit Procedure

Command Line

Run the following script to verify root's path does not include:

• Locations that are not directories
• An empty directory (::)
• A trailing (:)
• Current working directory (.)
• Non root owned directories
• Directories that less restrictive than mode 0755

#!/usr/bin/env bash

{
  l_output2=""
  l_pmask="0022"
  l_maxperm="$( printf '%o' $(( 0777 & ~$l_pmask )) )"
  l_root_path="$(sudo -Hiu root env | grep '^PATH' | cut -d= -f2)"
  unset a_path_loc && IFS=":" read -ra a_path_loc <<< "$l_root_path"
  grep -q "::" <<< "$l_root_path" && l_output2="$l_output2\n - root's path contains a empty directory (::)"
  grep -Pq ":\h*$" <<< "$l_root_path" && l_output2="$l_output2\n - root's path contains a trailing (:)"
  grep -Pq '(\h+|:)\.(:|\h*$)' <<< "$l_root_path" && l_output2="$l_output2\n - root's path contains current working directory (.)"
  while read -r l_path; do
    if [ -d "$l_path" ]; then
      while read -r l_fmode l_fown; do
        [ "$l_fown" != "root" ] && l_output2="$l_output2\n - Directory: \"$l_path\" is owned by: \"$l_fown\" should be owned by \"root\""
        [ $(( $l_fmode & $l_pmask )) -gt 0 ] && l_output2="$l_output2\n - Directory: \"$l_path\" is mode: \"$l_fmode\" and should be mode: \"$l_maxperm\" or more restrictive"
        done <<< "$(stat -Lc '%#a %U' "$l_path")"
    else
      l_output2="$l_output2\n - \"$l_path\" is not a directory"
    fi
  done <<< "$(printf "%s\n" "${a_path_loc[@]}")"
  if [ -z "$l_output2" ]; then
    echo -e "\n- Audit Result:\n  *** PASS ***\n - Root's path is correctly configured\n"
  else
    echo -e "\n- Audit Result:\n  ** FAIL **\n - * Reasons for audit failure * :\n$l_output2\n"
  fi
}

Expected Result

- Audit Result:
  *** PASS ***
 - Root's path is correctly configured

Remediation

Command Line

Correct or justify any:

• Locations that are not directories
• Empty directories (::)
• Trailing (:)
• Current working directory (.)
• Non root owned directories
• Directories that less restrictive than mode 0755

Default Value

None specified.

References

1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5

CIS Controls

v8 - 0.0 Explicitly Not Mapped (IG 0)

v7 - 0.0 Explicitly Not Mapped (IG 0)

MITRE ATT&CK Mappings: T1204, T1204.002 - Tactics: TA0006 - Mitigations: M1022