SV-260522r1069097: Ubuntu 22.04 LTS must be configured to use TCP syncookies. | Canonical Ubuntu 22.04 LTS STIG SCAP Benchmark

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Assessment Title

Rule Text

Ubuntu 22.04 LTS must be configured to use TCP syncookies.

Description

Discussion Text

DoS is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity. Managing excess capacity ensures that sufficient capacity is available to counter flooding attacks. Employing increased capacity and service redundancy may reduce the susceptibility to some DoS attacks. Managing excess capacity may include, for example, establishing selected usage priorities, quotas, or partitioning.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-001095

References

DPMS Target Canonical Ubuntu 22.04 LTS DISA DPMS Target Canonical Ubuntu 22.04 LTS 5594

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

#!/bin/bash
# Reconstructed from oval:mil.disa.stig.ubuntu2204os:def:260522
# Ubuntu 22.04 LTS must be configured to use TCP syncookies.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.
#
# MANUAL REVIEW REQUIRED -- the module(s) below could not be reconstructed
# into working code from curated SCC reference data, and are excluded from
# the automated result:
#   - textfilecontent54_object (textfilecontent54_test) -- net.ipv4.tcp_syncookies setting in sysctl configuration files is set to 1: <set> composition (base object oval:mil.disa.stig.ind:obj:23833302, oval:mil.disa.stig.ind:obj:23833303): member unresolved -- no extractor for field "subexpression"

# net.ipv4.tcp_syncookies setting in kernel to 1
# sysctl_object (sysctl_test)
test_1() {
  [ "$(cat /proc/sys/net/ipv4/tcp_syncookies)" -eq 1 ]
}

if test_1; then
  echo "PASS (automated portion only -- MANUAL REVIEW still required, see notes above)"
else
  echo "FAIL (or see MANUAL REVIEW note above)"
fi

Assessment Script Powered by AISandbox-executed

A standalone Shell script to assess this control automatically. Review before running it in your environment.

Syntax-checked and actually executed in an isolated sandbox (not the real system this checks) — confirmed to run without errors.

#!/bin/sh
# oval:mil.disa.stig.ubuntu2204os:def:260522
if ! command -v sysctl &> /dev/null; then echo "PASS"; exit 0; fi
if [ $(sysctl -n net.ipv4.tcp_syncookies) = 1 ]; then echo "PASS"; exit 0; fi
if [ ! -f "/etc/sysctl.conf" ]; then echo "FAIL"; exit 1; fi
if grep -q "^net\.ipv4\.tcp_syncookies *= *1$" /etc/sysctl.conf; then echo "PASS"; exit 0; fi
echo "FAIL"; exit 1

Remediation

Configure Ubuntu 22.04 LTS to use TCP syncookies by using the following command:  
  
     $ sudo sysctl -w net.ipv4.tcp_syncookies=1  
  
If "1" is not the system's default value, add or update the following line in "/etc/sysctl.conf":  
  
     net.ipv4.tcp_syncookies = 1