Info on the xc backdoor

https://www.openwall.com/lists/oss-security/2024/03/29/4

https://tukaani.org/xz-backdoor/

https://www.tenable.com/blog/frequently-asked-questions-cve-2024-3094-supply-chain-backdoor-in-xz-utils

Kostas on Twitter posted a helpful one-liner to check the xz version without running the actual command.

https://twitter.com/kostastsale/status/1773890846250926445

Versions 5.6.0 and 5.6.1 are backdoored.

Bash one liner

The following Bash commands were taken and modified from the above Twitter link

Here is a one liner that will check the version of xz binaries and return if they are safe or vulnerable. You’ll need to run this in a Bash shell. May have issues in sh.

for xz_p in $(type -a xz | awk '{print $NF}' ); do  if ( strings "$xz_p" | grep "xz (XZ Utils)" | grep '5.6.0\|5.6.1' ); then echo $xz_p Vulnerable; else echo $xz_p Safe ; fi ; done 

Ansible Playbooks

Here are two different Ansible Playbooks to check if the xz package(s) are backdoored.

This one uses the above Bash commands to check the xz binaries.

---
- name: Check if XZ tools are compromised
# https://twitter.com/kostastsale/status/1773890846250926445
  hosts: all

  tasks: 
    - name: Run Bash command
      shell : 
        for xz_p in $(type -a xz | awk '{print $NF}' ); do 
          if ( strings "$xz_p" | grep "xz (XZ Utils)" | grep '5.6.0\|5.6.1' ); 
            then echo $xz_p Vulnerable!; 
          else 
            echo $xz_p Safe ; 
          fi ; 
        done
      args: 
        executable: /bin/bash
      register: result

    - name: Show output
      ansible.builtin.debug:
        msg: "{{ result.stdout_lines }}"

The following playbook uses the package manager to check the xz version. On RHEL/Fedora this is the xc package. On Debian/Ubuntu, it is part of the liblzma5 package.

---
- name: Check if XZ tools are compromised
  hosts: all

  tasks:
    - name: Collect package info
      ansible.builtin.package_facts:
        manager: auto

    - name: Check if liblzma5 is vulnerable (Ubuntu/Debian)
      ansible.builtin.debug:
        msg: "Installed version of liblzma5/xz: {{ ansible_facts.packages['liblzma5'] | map(attribute='version') | join(', ') }} Vulnerable!"
      when: ('liblzma5' in ansible_facts.packages) and (ansible_facts.packages['liblzma5'][0].version.split('-')[0] is version('5.6.0', '==') or ansible_facts.packages['liblzma5'][0].version.split('-')[0] is version('5.6.1', '=='))

    - name: Check if xz is vulnerable (RHEL/Fedora/Rocky/Alma)
      ansible.builtin.debug:
        msg: "Installed version of xz: {{ ansible_facts.packages['xz'] | map(attribute='version') | join(', ') }} is vulnerable"
      when: ('xz' in ansible_facts.packages) and (ansible_facts.packages['xz'][0].version is version('5.6.0', '==') or ansible_facts.packages['xz'][0].version is version('5.6.1', '=='))