Files
debian-cis/bin/hardening/enable_tcp_syn_cookies.sh
damcav35 be33848d81 Damcava35/set version (#257)
* feat: add "--set-version" option

This feature will allow to chose a specific cis version to run, like debian 11 or debian 12

* chore: configure current repository as a version

And use it as default version.

To this end, the scripts in bin/hardening have been made generic by removing the associated recommendation number.
Only impact is if you are used to execute scripts directly from bin/hardening.
In this case, please use the "bin/hardening.sh" wrapper as intended.

I had to rename 2.3.1_disable_nis.sh to uninstall_nis.sh, as it was conflicting with 2.3.1_disable_nis.sh

Also, there was a doublon between 1.1.1.8_disable_cramfs.sh and 99.1.1.1_disable_cramfs.sh ; the former was kept

* chore: remove CIS recommendation numbers from bin/hardening scripts

* fix: some tests are failing

find_ungrouped_files.sh and find_unowned_files.sh tests can not be executed multiple times:
- test repository is not cleaned
- configuration is updated multiple times

Those tests are also failing, because:
- the sed to change the status in the configuration was also changing the test folder path.
- missing /proc in EXCLUDED paths
- the EXCLUDED configuration doesn't have the correct format for egrep

---------

Co-authored-by: Damien Cavagnini <damien.cavagnini@corp.ovh.com>
2025-07-01 08:41:55 +02:00

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#!/bin/bash
# run-shellcheck
#
# CIS Debian Hardening
#
#
# Ensure TCP SYN Cookies is enabled (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="Enable TCP-SYN cookie to prevent TCP-SYN flood attack."
SYSCTL_PARAMS='net.ipv4.tcp_syncookies=1'
# This function will be called if the script status is on enabled / audit mode
audit() {
for SYSCTL_VALUES in $SYSCTL_PARAMS; do
SYSCTL_PARAM=$(echo "$SYSCTL_VALUES" | cut -d= -f 1)
SYSCTL_EXP_RESULT=$(echo "$SYSCTL_VALUES" | cut -d= -f 2)
debug "$SYSCTL_PARAM should be set to $SYSCTL_EXP_RESULT"
has_sysctl_param_expected_result "$SYSCTL_PARAM" "$SYSCTL_EXP_RESULT"
if [ "$FNRET" != 0 ]; then
crit "$SYSCTL_PARAM was not set to $SYSCTL_EXP_RESULT"
elif [ "$FNRET" = 255 ]; then
warn "$SYSCTL_PARAM does not exist -- Typo?"
else
ok "$SYSCTL_PARAM correctly set to $SYSCTL_EXP_RESULT"
fi
done
}
# This function will be called if the script status is on enabled mode
apply() {
for SYSCTL_VALUES in $SYSCTL_PARAMS; do
SYSCTL_PARAM=$(echo "$SYSCTL_VALUES" | cut -d= -f 1)
SYSCTL_EXP_RESULT=$(echo "$SYSCTL_VALUES" | cut -d= -f 2)
debug "$SYSCTL_PARAM should be set to $SYSCTL_EXP_RESULT"
has_sysctl_param_expected_result "$SYSCTL_PARAM" "$SYSCTL_EXP_RESULT"
if [ "$FNRET" != 0 ]; then
warn "$SYSCTL_PARAM was not set to $SYSCTL_EXP_RESULT -- Fixing"
set_sysctl_param "$SYSCTL_PARAM" "$SYSCTL_EXP_RESULT"
sysctl -w net.ipv4.route.flush=1 >/dev/null
elif [ "$FNRET" = 255 ]; then
warn "$SYSCTL_PARAM does not exist -- Typo?"
else
ok "$SYSCTL_PARAM correctly set to $SYSCTL_EXP_RESULT"
fi
done
}
# This function will check config parameters required
check_config() {
:
}
# Source Root Dir Parameter
if [ -r /etc/default/cis-hardening ]; then
# shellcheck source=../../debian/default
. /etc/default/cis-hardening
fi
if [ -z "$CIS_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