debian-cis/bin/hardening/99.5.1_ssh_auth_pubk_only.sh

#!/bin/bash
# run-shellcheck

#
# OVH Security audit
#

#
# Ensure that sshd only allows authentication through public key.
#

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

# shellcheck disable=2034
HARDENING_LEVEL=2
# shellcheck disable=2034
DESCRIPTION="Ensure that sshd only allows authentication through public key."

PACKAGE='openssh-server'
FILE='/etc/ssh/sshd_config'
OPTIONS='PubkeyAuthentication=yes PasswordAuthentication=no KbdInteractiveAuthentication=no KerberosAuthentication=no ChallengeResponseAuthentication=no HostbasedAuthentication=no GSSAPIAuthentication=no GSSAPIKeyExchange=no '

# This function will be called if the script status is on enabled / audit mode
audit () {
    is_pkg_installed $PACKAGE
    if [ "$FNRET" != 0 ]; then
        crit "$PACKAGE is not installed!"
    else
        ok "$PACKAGE is installed"
        for SSH_OPTION in $OPTIONS; do
            SSH_PARAM=$(echo "$SSH_OPTION" | cut -d= -f 1)
            SSH_VALUE=$(echo "$SSH_OPTION" | cut -d= -f 2)
            PATTERN="^$SSH_PARAM[[:space:]]+$SSH_VALUE"
            does_pattern_exist_in_file_nocase $FILE "$PATTERN"
            if [ "$FNRET" = 0 ]; then
                ok "$PATTERN is present in $FILE"
            else
                crit "$PATTERN is not present in $FILE"
            fi
        done
    fi
}

# This function will be called if the script status is on enabled mode
apply () {
    is_pkg_installed $PACKAGE
    if [ "$FNRET" = 0 ]; then
        ok "$PACKAGE is installed"
    else
        crit "$PACKAGE is absent, installing it"
        apt_install $PACKAGE
    fi
    for SSH_OPTION in $OPTIONS; do
            SSH_PARAM=$(echo "$SSH_OPTION" | cut -d= -f 1)
            SSH_VALUE=$(echo "$SSH_OPTION" | cut -d= -f 2)
            PATTERN="^$SSH_PARAM[[:space:]]+$SSH_VALUE"
            does_pattern_exist_in_file_nocase $FILE "$PATTERN"
            if [ "$FNRET" = 0 ]; then
                ok "$PATTERN is present in $FILE"
            else
                warn "$PATTERN is not present in $FILE, adding it"
                does_pattern_exist_in_file_nocase $FILE "^$SSH_PARAM"
                if [ "$FNRET" != 0 ]; then
                    add_end_of_file $FILE "$SSH_PARAM $SSH_VALUE"
                else
                    info "Parameter $SSH_PARAM is present but with the wrong value -- Fixing"
                    replace_in_file $FILE "^$SSH_PARAM[[:space:]]+.*" "$SSH_PARAM $SSH_VALUE"
                fi
                /etc/init.d/ssh reload > /dev/null 2>&1
            fi
    done
}

# This function will check config parameters required
check_config() {
    :
}

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

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