Set Account Expiration Following Inactivity in system-auth

An XCCDF Rule

Description

Verify the account identifiers (individuals, groups, roles, and devices) are disabled after or less days of inactivity by checking the account inactivity value with the following command:

grep 'inactive\|pam_unix' /etc/pam.d/password-auth | grep -w auth

auth required pam_lastlog.so inactive=35
auth sufficient pam_unix.so

The line with the inactive parameter should be placed before pam_unix.so module as in the example output.

warning alert: Warning

If the system relies on authselect tool to manage PAM settings, the remediation will also use authselect tool. However, if any manual modification was made in PAM files, the authselect integrity check will fail and the remediation will be aborted in order to preserve intentional changes. In this case, an informative message will be shown in the remediation report.

Rationale

Inactive identifiers pose a risk to systems and applications because attackers may exploit an inactive identifier and potentially obtain undetected access to the system. Owners of inactive accounts will not notice if unauthorized access to their user account has been obtained.

ID: xccdf_org.ssgproject.content_rule_account_disable_inactivity_system_auth
Severity: Medium
References: CCI-000795

IA-4(e)

SRG-OS-000118-GPOS-00060
Updated: about 1 year ago

# Remediation is applicable only in certain platforms
if rpm --quiet -q pam; then

PAM_FILE_PATH="/etc/pam.d/system-auth"
if [ -f /usr/bin/authselect ]; then
    if ! authselect check; then    echo "
    authselect integrity check failed. Remediation aborted!
    This remediation could not be applied because an authselect profile was not selected or the selected profile is not intact.
    It is not recommended to manually edit the PAM files when authselect tool is available.
    In cases where the default authselect profile does not cover a specific demand, a custom authselect profile is recommended."
    exit 1
    fi
    CURRENT_PROFILE=$(authselect current -r | awk '{ print $1 }')
    # If not already in use, a custom profile is created preserving the enabled features.
    if [[ ! $CURRENT_PROFILE == custom/* ]]; then
        ENABLED_FEATURES=$(authselect current | tail -n+3 | awk '{ print $2 }')
        authselect create-profile hardening -b $CURRENT_PROFILE
        CURRENT_PROFILE="custom/hardening"
        
        authselect apply-changes -b --backup=before-hardening-custom-profile
        authselect select $CURRENT_PROFILE
        for feature in $ENABLED_FEATURES; do
            authselect enable-feature $feature;
        done
        
        authselect apply-changes -b --backup=after-hardening-custom-profile
    fi
    PAM_FILE_NAME=$(basename "$PAM_FILE_PATH")
    PAM_FILE_PATH="/etc/authselect/$CURRENT_PROFILE/$PAM_FILE_NAME"
    authselect apply-changes -b --backup=before-hardening-pam_lastlog.so-inactive.backup
fi
if ! grep -qP '^\s*auth\s+'"required"'\s+pam_lastlog.so\s*.*' "$PAM_FILE_PATH"; then
    # Line matching group + control + module was not found. Check group + module.
    if [ "$(grep -cP '^\s*auth\s+.*\s+pam_lastlog.so\s*' "$PAM_FILE_PATH")" -eq 1 ]; then
        # The control is updated only if one single line matches.
        sed -i -E --follow-symlinks 's/^(\s*auth\s+).*(\bpam_lastlog.so.*)/\1'"required"' \2/' "$PAM_FILE_PATH"
    else
        echo 'auth    '"required"'    pam_lastlog.so' >> "$PAM_FILE_PATH"
    fi
fi
# Check the option
if ! grep -qP '^\s*auth\s+'"required"'\s+pam_lastlog.so\s*.*\sinactive\b' "$PAM_FILE_PATH"; then
    sed -i -E --follow-symlinks '/\s*auth\s+'"required"'\s+pam_lastlog.so.*/ s/$/ inactive='"35"'/' "$PAM_FILE_PATH"
else
    sed -i -E --follow-symlinks 's/(\s*auth\s+'"required"'\s+pam_lastlog.so\s+.*)('"inactive"'=)[[:alnum:]]+\s*(.*)/\1\2'"35"' \3/' "$PAM_FILE_PATH"
fi
if ! grep -qP '^\s*auth\s+'"sufficient"'\s+pam_unix.so\s*.*' "$PAM_FILE_PATH"; then
    # Line matching group + control + module was not found. Check group + module.
    if [ "$(grep -cP '^\s*auth\s+.*\s+pam_unix.so\s*' "$PAM_FILE_PATH")" -eq 1 ]; then
        # The control is updated only if one single line matches.
        sed -i -E --follow-symlinks 's/^(\s*auth\s+).*(\bpam_unix.so.*)/\1'"sufficient"' \2/' "$PAM_FILE_PATH"
    else
        echo 'auth    '"sufficient"'    pam_unix.so' >> "$PAM_FILE_PATH"
    fi
fi
# Ensure pam_unix.so is configured after pam_lastlog.so
if ! grep -Pz \
    "auth\s*required\s*pam_lastlog\.so[^#]*inactive=35[\s\S]*\n\s*auth\s*sufficient\s*pam_unix\.so"\
    "$PAM_FILE_PATH"  ; then
    PAM_LASTLOG_LINE="$(grep -oP '^\s*auth.*pam_lastlog\.so.*' $PAM_FILE_PATH)"
    sed -i "0,/^\s*auth.*pam_unix\.so.*/i$PAM_LASTLOG_LINE" "$PAM_FILE_PATH"
fi
if [ -f /usr/bin/authselect ]; then
    authselect apply-changes -b --backup=after-hardening-pam_lastlog.so-inactive.backup
fi

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

Set Account Expiration Following Inactivity in system-auth

Description

Rationale

Remediation - Shell Script