Configure GnuTLS library to use DoD-approved TLS Encryption

An XCCDF Rule

Description

Crypto Policies provide a centralized control over crypto algorithms usage of many packages. GnuTLS is supported by system crypto policy, but the GnuTLS configuration may be set up to ignore it. To check that Crypto Policies settings are configured correctly, ensure that /etc/crypto-policies/back-ends/gnutls.config contains the following line and is not commented out: +VERS-ALL:-VERS-DTLS0.9:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:-VERS-DTLS1.0

Rationale

Overriding the system crypto policy makes the behavior of the GnuTLS library violate expectations, and makes system configuration more fragmented.

ID: xccdf_org.ssgproject.content_rule_configure_gnutls_tls_crypto_policy
Severity: Medium
References: CCI-001453

AC-17(2)

SRG-OS-000250-GPOS-00093 SRG-OS-000423-GPOS-00187

OL08-00-010295

SV-248566r877394_rule
Updated: about 1 year ago

- name: 'Configure GnuTLS library to use DoD-approved TLS Encryption: set_fact'
  set_fact:
    path: /etc/crypto-policies/back-ends/gnutls.config
    correct_value: +VERS-ALL:-VERS-DTLS0.9:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:-VERS-DTLS1.0
    lineinfile_reg: \+VERS-ALL:-VERS-DTLS0\.9:-VERS-SSL3\.0:-VERS-TLS1\.0:-VERS-TLS1\.1:-VERS-DTLS1\.0
  tags:  - DISA-STIG-OL08-00-010295
  - NIST-800-53-AC-17(2)
  - configure_gnutls_tls_crypto_policy
  - low_complexity
  - low_disruption
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: 'Configure GnuTLS library to use DoD-approved TLS Encryption: stat'
  stat:
    path: '{{ path }}'
    follow: true
  register: gnutls_file
  tags:
  - DISA-STIG-OL08-00-010295
  - NIST-800-53-AC-17(2)
  - configure_gnutls_tls_crypto_policy
  - low_complexity
  - low_disruption
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: 'Configure GnuTLS library to use DoD-approved TLS Encryption: Add'
  lineinfile:
    path: '{{ path }}'
    regexp: '{{ lineinfile_reg }}'
    line: '{{ correct_value }}'
    create: true
  when: not gnutls_file.stat.exists or gnutls_file.stat.size <= correct_value|length
  tags:
  - DISA-STIG-OL08-00-010295
  - NIST-800-53-AC-17(2)
  - configure_gnutls_tls_crypto_policy
  - low_complexity
  - low_disruption
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Configure GnuTLS library to use DoD-approved TLS Encryption
  block:

  - name: 'Configure GnuTLS library to use DoD-approved TLS Encryption: Existing value
      check'
    lineinfile:
      path: '{{ path }}'
      create: false
      regexp: '{{ lineinfile_reg }}'
      state: absent
    check_mode: true
    changed_when: false
    register: gnutls

  - name: 'Configure GnuTLS library to use DoD-approved TLS Encryption: Update'
    replace:
      path: '{{ path }}'
      regexp: (\+VERS-ALL(?::-VERS-[A-Z]+\d\.\d)+)
      replace: '{{ correct_value }}'
    when: gnutls.found is defined and gnutls.found != 1
  when: gnutls_file.stat.exists and gnutls_file.stat.size > correct_value|length
  tags:
  - DISA-STIG-OL08-00-010295
  - NIST-800-53-AC-17(2)
  - configure_gnutls_tls_crypto_policy
  - low_complexity
  - low_disruption
  - medium_severity
  - reboot_required
  - restrict_strategy


CONF_FILE=/etc/crypto-policies/back-ends/gnutls.config
correct_value='+VERS-ALL:-VERS-DTLS0.9:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:-VERS-DTLS1.0'

grep -q ${correct_value} ${CONF_FILE}
if [[ $? -ne 0 ]]; then
    # We need to get the existing value, using PCRE to maintain same regex
    existing_value=$(grep -Po '(\+VERS-ALL(?::-VERS-[A-Z]+\d\.\d)+)' ${CONF_FILE})

    if [[ ! -z ${existing_value} ]]; then
        # replace existing_value with correct_value
        sed -i "s/${existing_value}/${correct_value}/g" ${CONF_FILE}
    else
        # ***NOTE*** #
        # This probably means this file is not here or it's been modified
        # unintentionally.
        # ********** #
        # echo correct_value to end
        echo ${correct_value} >> ${CONF_FILE}
    fi
fi

Configure GnuTLS library to use DoD-approved TLS Encryption

Description

Rationale

Remediation - Ansible

Remediation - Shell Script