Ensure PAM Enforces Password Requirements - Prevent the Use of Dictionary Words
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Description
The pam_pwquality module’s dictcheck
check if passwords contains dictionary words. When
dictcheck
is set to 1
passwords will be checked for dictionary words.
Rationale
Use of a complex password helps to increase the time and resources required to compromise the password.
Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at
guessing and brute-force attacks.
Password complexity is one factor of several that determines how long it takes to crack a password. The more
complex the password, the greater the number of possible combinations that need to be tested before the
password is compromised.
Passwords with dictionary words may be more vulnerable to password-guessing attacks.
Shell script
The following script can be run on the host to remediate the issue.
#!/bin/bash
# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q installed; then
var_password_pam_dictcheck='1'
# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^dictcheck")
# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_dictcheck"
# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^dictcheck\\>" "/etc/security/pwquality.conf"; then
escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
LC_ALL=C sed -i --follow-symlinks "s/^dictcheck\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
else
if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
fi
printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
fi
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
Ansible playbook
The following playbook can be run with Ansible to remediate the issue.
- name: Gather the package facts
package_facts:
manager: auto
tags:
- DISA-STIG-UBTU-20-010056
- NIST-800-53-CM-6(a)
- NIST-800-53-IA-5(1)(a)
- NIST-800-53-IA-5(4)
- NIST-800-53-IA-5(c)
- accounts_password_pam_dictcheck
- low_complexity
- low_disruption
- medium_severity
- no_reboot_needed
- restrict_strategy
- name: XCCDF Value var_password_pam_dictcheck # promote to variable
set_fact:
var_password_pam_dictcheck: !!str 1
tags:
- always
- name: Ensure PAM Enforces Password Requirements - Prevent the Use of Dictionary
Words - Ensure PAM variable dictcheck is set accordingly
ansible.builtin.lineinfile:
create: true
dest: /etc/security/pwquality.conf
regexp: ^#?\s*dictcheck
line: dictcheck = {{ var_password_pam_dictcheck }}
when: '"libpam-runtime" in ansible_facts.packages'
tags:
- DISA-STIG-UBTU-20-010056
- NIST-800-53-CM-6(a)
- NIST-800-53-IA-5(1)(a)
- NIST-800-53-IA-5(4)
- NIST-800-53-IA-5(c)
- accounts_password_pam_dictcheck
- low_complexity
- low_disruption
- medium_severity
- no_reboot_needed
- restrict_strategy