RHEL-09-213030 - RHEL 9 must enable kernel parameters to enforce discretionary access control on hardlinks.

Information

By enabling the fs.protected_hardlinks kernel parameter, users can no longer create soft or hard links to files they do not own. Disallowing such hardlinks mitigates vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().

Satisfies: SRG-OS-000312-GPOS-00123, SRG-OS-000324-GPOS-00125

Solution

Configure RHEL 9 to enable DAC on hardlinks with the following:

Add or edit the following line in a system configuration file in the '/etc/sysctl.d/' directory:

fs.protected_hardlinks = 1

Load settings from all system configuration files with the following command:

$ sudo sysctl --system

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_RHEL_9_V2R1_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-3(4), 800-53|AC-6(10), CAT|II, CCI|CCI-002165, CCI|CCI-002235, Rule-ID|SV-257801r958702_rule, STIG-ID|RHEL-09-213030, Vuln-ID|V-257801

Plugin: Unix

Control ID: 3b58f8e2fbdc14da9929c7956de3fe078e50ee96f3a8488c277333aa528b03fe