debian-cis/bin/hardening/5.4.2_disable_system_accounts.sh

#!/bin/bash

# run-shellcheck
#
# CIS Debian Hardening
#

#
# 5.4.2 Ensure system accounts are non-login (Scored)
#

set -e # One error, it's over
set -u # One variable unset, it's over

# shellcheck disable=2034
HARDENING_LEVEL=3
# shellcheck disable=2034
DESCRIPTION="Disable system accounts, preventing them from interactive login."

ACCEPTED_SHELLS='/bin/false /usr/sbin/nologin /sbin/nologin'
SHELL_TO_APPLY='/bin/false'
FILE='/etc/passwd'
RESULT=''

ACCEPTED_SHELLS_GREP=''
# This function will be called if the script status is on enabled / audit mode
audit() {
    shells_to_grep_helper
    info "Checking if admin accounts have a login shell different than $ACCEPTED_SHELLS"
    # shellcheck disable=SC2086
    RESULT=$(grep -Ev "^\+" "$FILE" | awk -F: '($1!="root" && $1!="sync" && $1!="shutdown" && $1!="halt" && $3<1000 ) {print}' | grep -v $ACCEPTED_SHELLS_GREP || true)
    IFS_BAK=$IFS
    IFS=$'\n'
    for LINE in $RESULT; do
        debug "line : $LINE"
        ACCOUNT=$(echo "$LINE" | cut -d: -f 1)
        debug "Account : $ACCOUNT"
        debug "Exceptions : $EXCEPTIONS"
        debug "echo \"$EXCEPTIONS\" | grep -q $ACCOUNT"
        if echo "$EXCEPTIONS" | grep -q "$ACCOUNT"; then
            debug "$ACCOUNT is confirmed as an exception"
            # shellcheck disable=SC2001
            RESULT=$(sed "s!$LINE!!" <<<"$RESULT")
        else
            debug "$ACCOUNT not found in exceptions"
        fi
    done
    IFS=$IFS_BAK
    if [ -n "$RESULT" ]; then
        crit "Some admin accounts don't have any of $ACCEPTED_SHELLS as their login shell"
        crit "$RESULT"
    else
        ok "All admin accounts deactivated"
    fi
}

# This function will be called if the script status is on enabled mode
apply() {
    # shellcheck disable=SC2086
    RESULT=$(grep -Ev "^\+" "$FILE" | awk -F: '($1!="root" && $1!="sync" && $1!="shutdown" && $1!="halt" && $3<1000 ) {print}' | grep -v $ACCEPTED_SHELLS_GREP || true)
    IFS_BAK=$IFS
    IFS=$'\n'
    for LINE in $RESULT; do
        debug "line : $LINE"
        ACCOUNT=$(echo "$LINE" | cut -d: -f 1)
        debug "Account : $ACCOUNT"
        debug "Exceptions : $EXCEPTIONS"
        debug "echo \"$EXCEPTIONS\" | grep -q $ACCOUNT"
        if echo "$EXCEPTIONS" | grep -q "$ACCOUNT"; then
            debug "$ACCOUNT is confirmed as an exception"
            # shellcheck disable=SC2001
            RESULT=$(sed "s!$LINE!!" <<<"$RESULT")
        else
            debug "$ACCOUNT not found in exceptions"
        fi
    done
    IFS=$IFS_BAK
    if [ -n "$RESULT" ]; then
        warn "Some admin accounts don't have any of $ACCEPTED_SHELLS as their login shell -- Fixing"
        warn "$RESULT"
        for USER in $(echo "$RESULT" | cut -d: -f 1); do
            info "Setting $SHELL_TO_APPLY as $USER login shell"
            usermod -s "$SHELL_TO_APPLY" "$USER"
        done
    else
        ok "All admin accounts deactivated, nothing to apply"
    fi
}

shells_to_grep_helper() {
    for shell in $ACCEPTED_SHELLS; do
        ACCEPTED_SHELLS_GREP+=" -e $shell"
    done
}

# This function will create the config file for this check with default values
create_config() {
    cat <<EOF
status=audit
# Put here your exceptions concerning admin accounts shells separated by spaces
EXCEPTIONS=""
EOF
}

# This function will check config parameters required
check_config() {
    if [ -z "$EXCEPTIONS" ]; then
        EXCEPTIONS="@"
    fi
}

# Source Root Dir Parameter
if [ -r /etc/default/cis-hardening ]; then
    # shellcheck source=../../debian/default
    . /etc/default/cis-hardening
fi
if [ -z "$CIS_LIB_DIR" ]; then
    echo "There is no /etc/default/cis-hardening file nor cis-hardening directory in current environment."
    echo "Cannot source CIS_LIB_DIR variable, aborting."
    exit 128
fi

# Main function, will call the proper functions given the configuration (audit, enabled, disabled)
if [ -r "${CIS_LIB_DIR}"/main.sh ]; then
    # shellcheck source=../../lib/main.sh
    . "${CIS_LIB_DIR}"/main.sh
else
    echo "Cannot find main.sh, have you correctly defined your root directory? Current value is $CIS_LIB_DIR in /etc/default/cis-hardening"
    exit 128
fi