TOSS 5 must enable kernel parameters to enforce discretionary access control on hardlinks.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-282553 | SRG-OS-000312-GPOS-00123 | TOSS-05-000102 | SV-282553r1200639_rule | 2026-04-01 | 1 |
Description
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
ℹ️ Check
Verify TOSS 5 is configured to enable DAC on hardlinks using the following command:
$ sudo sysctl fs.protected_hardlinks
fs.protected_hardlinks = 1
If "fs.protected_hardlinks" is not set to "1" or is missing, this is a finding.
✔️ Fix
Configure TOSS 5 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 using the following command:
$ sudo sysctl --system