SV-258216r1155613: Successful/unsuccessful uses of the umount2 system call in RHEL 9 must generate an audit record. | Red Hat Enterprise Linux 9 STIG SCAP Benchmark

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Assessment Title

Rule Text

Successful/unsuccessful uses of the umount2 system call in RHEL 9 must generate an audit record.

Description

Discussion Text

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users. Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

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

IA Controls

NIST SP 800-53

Not mappedCCI-000130Not mappedCCI-000169Not mappedCCI-000172Not mappedCCI-002884

References

DPMS Target Red Hat Enterprise Linux 9 DISA DPMS Target Red Hat Enterprise Linux 9 5551

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.rhel9os:def:258216
# Successful/unsuccessful uses of the umount2 system call in RHEL 9 must generate an audit record.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# Audit 32-bit invocations of umount2 syscall
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  grep -Pq '^\s*-a\s+(always,exit|exit,always)\s+-F\s+arch=b32\s+(?:.*(-S\s+umount2\s+|(\s+|,)umount2(\s+|,))).*-F\s+auid>=1000\s+-F\s+auid!=(4294967295|-1|unset)(\s+(-k\s+|-F\s+key=)[-\w]+)*\s*$' '/etc/audit/audit.rules' &>/dev/null
}
# Audit 64-bit invocations of umount2 syscall
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  grep -Pq '^\s*-a\s+(always,exit|exit,always)\s+-F\s+arch=b64\s+(?:.*(-S\s+umount2\s+|(\s+|,)umount2(\s+|,))).*-F\s+auid>=1000\s+-F\s+auid!=(4294967295|-1|unset)(\s+(-k\s+|-F\s+key=)[-\w]+)*\s*$' '/etc/audit/audit.rules' &>/dev/null
}

if ( test_1 && test_2 ); 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
# OVAL definition: oval:mil.disa.stig.rhel9os:def:258216

if grep -qE "^\\s*-a\\s+(always,exit|exit,always)\\s+-F\\s+arch=b32\\s+(?:.*(-S\\s+umount2\\s+|(\\s+|,)umount2(\\s+|,))).*-F\\s+auid>=1000\\s+-F\\s+auid != (4294967295|-1|unset)(\\s+(-k\\s+|-F\\s+key=)[-\\w]+)*\\s*$" /etc/audit/rules.d/audit.rules && \
   grep -qE "^\\s*-a\\s+(always,exit|exit,always)\\s+-F\\s+arch=b64\\s+(?:.*(-S\\s+umount2\\s+|(\\s+|,)umount2(\\s+|,))).*-F\\s+auid>=1000\\s+-F\\s+auid != (4294967295|-1|unset)(\\s+(-k\\s+|-F\\s+key=)[-\\w]+)*\\s*$" /etc/audit/rules.d/audit.rules; then
    echo "PASS"
    exit 0
else
    echo "FAIL"
    exit 1
fi

Remediation

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "umount2" system call by adding or updating the following rules in a file in "/etc/audit/rules.d".

-a always,exit -F arch=b32 -S umount2 -F auid>=1000 -F auid!=unset -k privileged-umount
-a always,exit -F arch=b64 -S umount2 -F auid>=1000 -F auid!=unset -k privileged-umount

To load the rules to the kernel immediately, use the following command:

$ sudo augenrules --load