Remove User Host-Based Authentication Files

An XCCDF Rule

Description

The ~/.shosts (in each user's home directory) files list remote hosts and users that are trusted by the local system. To remove these files, run the following command to delete them from any location:

$ sudo find / -name '.shosts' -type f -delete

Rationale

The .shosts files are used to configure host-based authentication for individual users or the system via SSH. Host-based authentication is not sufficient for preventing unauthorized access to the system, as it does not require interactive identification and authentication of a connection request, or for the use of two-factor authentication.

ID: xccdf_org.ssgproject.content_rule_no_user_host_based_files
Severity: High
References: CCI-000366

SRG-OS-000480-GPOS-00227

SV-204606r603261_rule
Updated: about 1 year ago

- name: Remove User Host-Based Authentication Files - Define Excluded (Non-Local)
    File Systems and Paths
  ansible.builtin.set_fact:
    excluded_fstypes:
    - afs
    - ceph    - cifs
    - smb3
    - smbfs
    - sshfs
    - ncpfs
    - ncp
    - nfs
    - nfs4
    - gfs
    - gfs2
    - glusterfs
    - gpfs
    - pvfs2
    - ocfs2
    - lustre
    - davfs
    - fuse.sshfs
    excluded_paths:
    - dev
    - proc
    - run
    - sys
    search_paths: []
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Find Relevant Root Directories
    Ignoring Pre-Defined Excluded Paths
  ansible.builtin.find:
    paths: /
    file_type: directory
    excludes: '{{ excluded_paths }}'
    hidden: true
    recurse: false
  register: result_relevant_root_dirs
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Include Relevant Root Directories
    in a List of Paths to be Searched
  ansible.builtin.set_fact:
    search_paths: '{{ search_paths | union([item.path]) }}'
  loop: '{{ result_relevant_root_dirs.files }}'
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Increment Search Paths List
    with Local Partitions Mount Points
  ansible.builtin.set_fact:
    search_paths: '{{ search_paths | union([item.mount]) }}'
  loop: '{{ ansible_mounts }}'
  when:
  - item.fstype not in excluded_fstypes
  - item.mount != '/'
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Increment Search Paths List
    with Local NFS File System Targets
  ansible.builtin.set_fact:
    search_paths: '{{ search_paths | union([item.device.split('':'')[1]]) }}'
  loop: '{{ ansible_mounts }}'
  when: item.device is search("localhost:")
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Define Rule Specific Facts
  ansible.builtin.set_fact:
    user_shosts_files:
    - /.shosts
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Find All .shosts Files in Local
    File Systems
  ansible.builtin.command:
    cmd: find {{ item }} -xdev -type f -name ".shosts"
  loop: '{{ search_paths }}'
  changed_when: false
  register: result_found_shosts_files
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Create List of .shosts Files
    Present in Local File Systems
  ansible.builtin.set_fact:
    user_shosts_files: '{{ user_shosts_files | union(item.stdout_lines) | list }}'
  loop: '{{ result_found_shosts_files.results }}'
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy

- name: Remove User Host-Based Authentication Files - Ensure No .shosts Files Are
    Present in the System
  ansible.builtin.file:
    path: '{{ item }}'
    state: absent
  loop: '{{ user_shosts_files }}'
  tags:
  - DISA-STIG-RHEL-07-040540
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - no_user_host_based_files
  - restrict_strategy


# Identify local mounts
MOUNT_LIST=$(df --local | awk '{ print $6 }')

# Find file on each listed mount point
for cur_mount in ${MOUNT_LIST}do
	find ${cur_mount} -xdev -type f -name ".shosts" -exec rm -f {} \;
done

Remove User Host-Based Authentication Files

Description

Rationale

Remediation - Ansible

Remediation - Shell Script