Check: RHEL-09-213030
RHEL 9 STIG:
RHEL-09-213030
(in versions v1 r3 through v1 r1)
Title
RHEL 9 must enable kernel parameters to enforce discretionary access control on hardlinks. (Cat II impact)
Discussion
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
Check Content
Verify RHEL 9 is configured to enable DAC on hardlinks. Check the status of the fs.protected_hardlinks kernel parameter with 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. Check that the configuration files are present to enable this kernel parameter. $ sudo /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F fs.protected_hardlinks | tail -1 fs.protected_hardlinks = 1 If "fs.protected_hardlinks" is not set to "1" or is missing, this is a finding.
Fix Text
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
Additional Identifiers
Rule ID: SV-257801r925390_rule
Vulnerability ID: V-257801
Group Title: SRG-OS-000312-GPOS-00123
Expert Comments
CCIs
| Number | Definition |
|---|---|
| CCI-002165 |
The information system enforces organization-defined discretionary access control policies over defined subjects and objects. |
| CCI-002235 |
The information system prevents non-privileged users from executing privileged functions to include disabling, circumventing, or altering implemented security safeguards/countermeasures. |