Limit Password Reuse

이 페이지는 아직 한국어로 제공되지 않으며 번역 작업 중입니다. 번역에 관한 질문이나 의견이 있으시면 언제든지 저희에게 연락해 주십시오.

Description

Do not allow users to reuse recent passwords. This can be accomplished by using the remember option for the pam_pwhistory PAM modules.

In the file /etc/pam.d/common-password, make sure the parameters remember and use_authtok are present, and that the value for the remember parameter is 5 or greater. For example:

password requisite pam_pwhistory.so ...existing_options... remember=5 use_authtok

The DoD STIG requirement is 5 passwords.

Rationale

Preventing re-use of previous passwords helps ensure that a compromised password is not re-used by a user.

Remediation

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

declare -a VALUES=()
declare -a VALUE_NAMES=()
declare -a ARGS=()
declare -a NEW_ARGS=()
declare -a DEL_ARGS=()

var_password_pam_remember='5'

VALUES+=("$var_password_pam_remember")
VALUE_NAMES+=("remember")
ARGS+=("")
NEW_ARGS+=("")

VALUES+=("")
VALUE_NAMES+=("")
ARGS+=("use_authtok")
NEW_ARGS+=("use_authtok")


for idx in "${!VALUES[@]}"
do
    if [ -e "/etc/pam.d/common-password" ] ; then
        valueRegex="${VALUES[$idx]}" defaultValue="${VALUES[$idx]}"
        # non-empty values need to be preceded by an equals sign
        [ -n "${valueRegex}" ] && valueRegex="=${valueRegex}"
        # add an equals sign to non-empty values
        [ -n "${defaultValue}" ] && defaultValue="=${defaultValue}"

        # fix the value for 'option' if one exists but does not match 'valueRegex'
        if grep -q -P "^\\s*password\\s+requisite\\s+pam_pwhistory.so(\\s.+)?\\s+${VALUE_NAMES[$idx]}(?"'!'"${valueRegex}(\\s|\$))" < "/etc/pam.d/common-password" ; then
            sed --follow-symlinks -i -E -e "s/^(\\s*password\\s+requisite\\s+pam_pwhistory.so(\\s.+)?\\s)${VALUE_NAMES[$idx]}=[^[:space:]]*/\\1${VALUE_NAMES[$idx]}${defaultValue}/" "/etc/pam.d/common-password"

        # add 'option=default' if option is not set
        elif grep -q -E "^\\s*password\\s+requisite\\s+pam_pwhistory.so" < "/etc/pam.d/common-password" &&
                grep    -E "^\\s*password\\s+requisite\\s+pam_pwhistory.so" < "/etc/pam.d/common-password" | grep -q -E -v "\\s${VALUE_NAMES[$idx]}(=|\\s|\$)" ; then

            sed --follow-symlinks -i -E -e "s/^(\\s*password\\s+requisite\\s+pam_pwhistory.so[^\\n]*)/\\1 ${VALUE_NAMES[$idx]}${defaultValue}/" "/etc/pam.d/common-password"
        # add a new entry if none exists
        elif ! grep -q -P "^\\s*password\\s+requisite\\s+pam_pwhistory.so(\\s.+)?\\s+${VALUE_NAMES[$idx]}${valueRegex}(\\s|\$)" < "/etc/pam.d/common-password" ; then
            echo "password requisite pam_pwhistory.so ${VALUE_NAMES[$idx]}${defaultValue}" >> "/etc/pam.d/common-password"
        fi
    else
        echo "/etc/pam.d/common-password doesn't exist" >&2
    fi
done

for idx in "${!ARGS[@]}"
do
    if ! grep -q -P "^\s*password\s+requisite\s+pam_pwhistory.so.*\s+${ARGS[$idx]}\s*$" /etc/pam.d/common-password ; then
        sed --follow-symlinks -i -E -e "s/^\\s*password\\s+requisite\\s+pam_pwhistory.so.*\$/& ${NEW_ARGS[$idx]}/" /etc/pam.d/common-password
        if [ -n "${DEL_ARGS[$idx]}" ]; then
            sed --follow-symlinks -i -E -e "s/\s+${DEL_ARGS[$idx]}\S+\s+/ /g" /etc/pam.d/common-password
        fi
    fi
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi