# Source: https://docs.datadoghq.com/security/default_rules/def-000-njm.md

---
title: Set Password Maximum Consecutive Repeating Characters
description: Datadog, the leading service for cloud-scale monitoring.
breadcrumbs: >-
  Docs > Datadog Security > OOTB Rules > Set Password Maximum Consecutive
  Repeating Characters
---

# Set Password Maximum Consecutive Repeating Characters
 
## Description{% #description %}

The pam_pwquality module's `maxrepeat` parameter controls requirements for consecutive repeating characters. When set to a positive number, it will reject passwords which contain more than that number of consecutive characters. Modify the `maxrepeat` setting in `/etc/security/pwquality.conf` to equal 3 to prevent a run of (3 + 1) or more identical characters.

## Rationale{% #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 excessive repeating characters may be more vulnerable to password-guessing attacks.

## Remediation{% #remediation %}

### Shell script{% #shell-script %}

The following script can be run on the host to remediate the issue.

```bash
#!/bin/bash

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}' 'libpwquality1' 2>/dev/null | grep -q '^installed$'; then

var_password_pam_maxrepeat='3'







conf_name=cac_pwquality
if [ ! -f /usr/share/pam-configs/"$conf_name" ]; then
    cat << EOF > /usr/share/pam-configs/"$conf_name"
Name: Pwquality password strength checking
Default: yes
Priority: 1025
Conflicts: cracklib, pwquality
Password-Type: Primary
Password:
    requisite                   pam_pwquality.so
EOF
fi

DEBIAN_FRONTEND=noninteractive pam-auth-update


# 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' <<< "^maxrepeat")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_maxrepeat"

# 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 "^maxrepeat\\>" "/etc/security/pwquality.conf"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^maxrepeat\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
else
    if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(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{% #ansible-playbook %}

The following playbook can be run with Ansible to remediate the issue.

```gdscript3
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
- name: XCCDF Value var_password_pam_maxrepeat # promote to variable
  set_fact:
    var_password_pam_maxrepeat: !!str 3
  tags:
    - always

- name: Set Password Maximum Consecutive Repeating Characters - Check if system relies
    on pam-auth-update tool
  ansible.builtin.stat:
    path: /usr/sbin/pam-auth-update
  register: result_pam_auth_update_present
  when: '"libpwquality1" in ansible_facts.packages'
  tags:
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Set Password Maximum Consecutive Repeating Characters - Remediation where
    pam-auth-update tool is present
  block:

  - name: Check if /usr/share/pam-configs/cac_pwquality exists
    stat:
      path: /usr/share/pam-configs/cac_pwquality
    register: pwquality_file_stat

  - name: Put the content into /usr/share/pam-configs/cac_pwquality if it does not
      exist
    copy:
      dest: /usr/share/pam-configs/cac_pwquality
      content: |
        Name: Pwquality password strength checking
        Default: yes
        Priority: 1024
        Conflicts: cracklib
        Password-Type: Primary
        Password:
          requisite           pam_pwquality.so retry=3
      force: true
    when: not pwquality_file_stat.stat.exists

  - name: Set Password Maximum Consecutive Repeating Characters - Ensure pam-auth-update
      profile changes are applied
    ansible.builtin.command:
      cmd: pam-auth-update --enable cac_pwquality
  when:
  - '"libpwquality1" in ansible_facts.packages'
  - result_pam_auth_update_present.stat.exists
  tags:
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Set Password Maximum Consecutive Repeating Characters - Ensure PAM variable
    maxrepeat is set accordingly
  ansible.builtin.lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*maxrepeat
    line: maxrepeat = {{ var_password_pam_maxrepeat }}
  when: '"libpwquality1" in ansible_facts.packages'
  tags:
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
```