SV-274004r1198253: Amazon Linux 2023 must disable access to network bpf system call from nonprivileged processes. | Amazon Linux 2023 STIG SCAP Benchmark

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Assessment Title

Rule Text

Amazon Linux 2023 must disable access to network bpf system call from nonprivileged processes.

Description

Discussion Text

Loading and accessing the packet filters programs and maps using the bpf() system call has the potential of revealing sensitive information about the kernel state.

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

IA Controls

NIST SP 800-53

Not mappedCCI-001082

References

DPMS Target Amazon Linux 2023 DISA DPMS Target Amazon Linux 2023 5700

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.amzlx23os:def:274004
# Amazon Linux 2023 must disable access to network bpf system call from nonprivileged processes.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# kernel.unprivileged_bpf_disabled setting in kernel is '1'.
# sysctl_object (sysctl_test)
test_1() {
  [ "$(cat /proc/sys/kernel/unprivileged_bpf_disabled)" -eq 1 ]
}

if test_1; then
  echo "PASS"
else
  echo "FAIL"
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
# DISA STIG / SCAP compliance check for Amazon Linux 2023 disabling bpf system call

# Check if sysctl command exists
if ! command -v sysctl &> /dev/null; then
  echo "FAIL"
  exit 1
fi

# Define the sysctl parameter to check
SYSCTL_PARAM="kernel.unprivileged_bpf_disabled"

# Check if the sysctl parameter exists
if ! sysctl -n -w "$SYSCTL_PARAM=1" &> /dev/null; then
  echo "FAIL"
  exit 1
fi

# Check the current value of the sysctl parameter
current_value=$(sysctl -n "$SYSCTL_PARAM")

# Check if the value is 1
if [ $current_value -eq 1 ]; then
  echo "PASS"
  exit 0
else
  echo "FAIL"
  exit 1
fi

Remediation

Configure Amazon Linux 2023 to prevent privilege escalation through the kernel by disabling access to the bpf syscall by adding the following line to a file, in the "/etc/sysctl.d" directory:

kernel.unprivileged_bpf_disabled = 1

The system configuration files must be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system