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3.2.4 Ensure sctp kernel module is not available
Information
The Stream Control Transmission Protocol (SCTP) is a transport layer protocol used to support message oriented communication, with several streams of messages in one connection. It serves a similar function as TCP and UDP, incorporating features of both. It is message-oriented like UDP, and ensures reliable in-sequence transport of messages with congestion control like TCP.- IF - the protocol is not being used, it is recommended that kernel module not be loaded, disabling the service to reduce the potential attack surface.
Solution
Run the following to unload and disable the sctp kernel module. This can also be done by running the script included below.Run the following commands to unload the sctp kernel module:
# modprobe -r sctp 2>/dev/null
# rmmod sctp 2>/dev/null
Perform the following to disable the sctp kernel module:
Create a file ending inconf with install sctp /bin/false in the /etc/modprobe.d/ directory
Example:
# printf '\n%s\n' "install sctp /bin/false" >> sctp.conf
Create a file ending inconf with blacklist sctp in the /etc/modprobe.d/ directory
Example:
# printf '\n%s\n' "blacklist sctp" >> sctp.conf
Optional remediation script:
This script will perform the above remediation as required by the system
#!/usr/bin/env bash
{
a_output2=() a_output3=() l_dl="" l_mod_name="sctp" l_mod_type="net"
l_mod_path="$(readlink -f /usr/lib/modules/**/kernel/$l_mod_type || readlink -f /lib/modules/**/kernel/$l_mod_type)"
f_module_fix()
{
l_dl="y" a_showconfig=()
while IFS= read -r l_showconfig; do
a_showconfig+=("$l_showconfig")
done < <(modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+'"${l_mod_chk_name//-/_}"'\b')
if lsmod | grep "$l_mod_chk_name" &> /dev/null; then
a_output2+=(" - unloading kernel module: \"$l_mod_name\"")
modprobe -r "$l_mod_chk_name" 2>/dev/null; rmmod "$l_mod_name" 2>/dev/null
fi
if ! grep -Pq -- '\binstall\h+'"${l_mod_chk_name//-/_}"'\h+(\/usr)?\/bin\/(true|false)\b' <<< "${a_showconfig[*]}"; then
a_output2+=(" - setting kernel module: \"$l_mod_name\" to \"$(readlink -f /bin/false)\"")
printf '%s\n' "install $l_mod_chk_name $(readlink -f /bin/false)" >> /etc/modprobe.d/"$l_mod_name".conf
fi
if ! grep -Pq -- '\bblacklist\h+'"${l_mod_chk_name//-/_}"'\b' <<< "${a_showconfig[*]}"; then
a_output2+=(" - denylisting kernel module: \"$l_mod_name\"")
printf '%s\n' "blacklist $l_mod_chk_name" >> /etc/modprobe.d/"$l_mod_name".conf
fi
}
for l_mod_base_directory in $l_mod_path; do # Check if the module exists on the system
if [ -d "$l_mod_base_directory/${l_mod_name/-/\/}" ] && [ -n "$(ls -A "$l_mod_base_directory/${l_mod_name/-/\/}")" ]; then
a_output3+=(" - \"$l_mod_base_directory\"")
l_mod_chk_name="$l_mod_name"
[[ "$l_mod_name" =~ overlay ]] && l_mod_chk_name="${l_mod_name::-2}"
[ "$l_dl" != "y" ] && f_module_fix
else
printf '%s\n' " - kernel module: \"$l_mod_name\" doesn't exist in \"$l_mod_base_directory\""
fi
done
[ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " -- INFO --" " - module: \"$l_mod_name\" exists in:" "${a_output3[@]}"
[ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" "${a_output2[@]}" || printf '%s\n' "" " - No changes needed"
printf '%s\n' "" " - remediation of kernel module: \"$l_mod_name\" complete" ""
}
See Also
Item Details
Category: CONFIGURATION MANAGEMENT
References: 800-53|CM-6, 800-53|CM-7, CSCv7|9.2
Plugin: Unix
Control ID: 4d145084d79c5599067abcce241d513a309fec78f8f266631ba0ee16067efa66