debian-cis/bin/hardening/5.2.15_ssh_cry_kex.sh
2020-11-27 09:29:11 +01:00

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#!/bin/bash
# run-shellcheck
#
# CIS Debian 7/8 Hardening
#
#
# 5.2.15 Ensure only strong Key Exchange algorithms are used (Scored)
#
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="Checking key exchange ciphers."
PACKAGE='openssh-server'
OPTIONS=''
FILE='/etc/ssh/sshd_config'
# 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
}
create_config() {
get_debian_major_version
set +u
debug "Debian version : $DEB_MAJ_VER "
if [[ -z $DEB_MAJ_VER ]] || [[ 7 -eq $DEB_MAJ_VER ]]; then
KEX='diffie-hellman-group-exchange-sha256'
elif [[ 8 -eq $DEB_MAJ_VER ]] || [[ 9 -eq $DEB_MAJ_VER ]]; then
KEX='curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256'
else
KEX='diffie-hellman-group-exchange-sha256'
fi
set -u
cat <<EOF
status=audit
# Put your KexAlgorithms
OPTIONS="KexAlgorithms=$KEX"
EOF
}
# This function will check config parameters required
check_config() {
:
}
# Source Root Dir Parameter
if [ -r /etc/default/cis-hardening ]; then
# shellcheck source=../../debian/default
. /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=../../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