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3.2.1 Ensure dccp kernel module is not available

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This audit has been deprecated and will be removed in a future update.

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Information

The Datagram Congestion Control Protocol (DCCP) is a transport layer protocol that supports streaming media and telephony. DCCP provides a way to gain access to congestion control, without having to do it at the application layer, but does not provide in-sequence delivery.

- IF - the protocol is not required, it is recommended that the drivers not be installed to reduce the potential attack surface.

Solution

Run the following script to unload and disable the dccp module:

- IF - the dccp kernel module is available in ANY installed kernel:

 - Create a file ending inconf with install dccp /bin/false in the /etc/modprobe.d/ directory
 - Create a file ending inconf with blacklist dccp in the /etc/modprobe.d/ directory
 - Run modprobe -r dccp 2>/dev/null; rmmod dccp 2>/dev/null to remove dccp from the kernel

- IF - the dccp kernel module is not available on the system, or pre-compiled into the kernel, no remediation is necessary

#!/usr/bin/env bash

{
 a_output2=() a_output3=() l_dl="" l_mod_name="dccp" 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 "$l_mod_name" 2>/dev/null
 fi
 if ! grep -Pq -- 'binstallh+'"${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
' "install $l_mod_chk_name $(readlink -f /bin/false)" >> /etc/modprobe.d/"$l_mod_name".conf
 fi
 if ! grep -Pq -- 'bblacklisth+'"${l_mod_chk_name//-/_}"'b' <<< "${a_showconfig[*]}"; then
 a_output2+=(" - denylisting kernel module: \"$l_mod_name\"")
 printf '%s
' "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}"
 [ "$l_dl" != "y" ] && f_module_fix
 else
 printf '%s
' " - kernel module: \"$l_mod_name\" doesn't exist in \"$l_mod_base_directory\""
 fi
 done
 [ "${#a_output3[@]}" -gt 0 ] && printf '%s
' "" " -- INFO --" " - module: \"$l_mod_name\" exists in:" "${a_output3[@]}"
 [ "${#a_output2[@]}" -gt 0 ] && printf '%s
' "" "${a_output2[@]}" || printf '%s
' "" " - No changes needed"
 printf '%s
' "" " - remediation of kernel module: \"$l_mod_name\" complete" ""
}

See Also

https://workbench.cisecurity.org/benchmarks/20333

Item Details

References: CSCv7|9.2

Plugin: Unix

Control ID: 6b81ba90fbf03e8a96f7909c7f892ef6f0d87fea582e53603ef5f9d8d6b7bc08