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V-282553

CAT II (Medium)

TOSS 5 must enable kernel parameters to enforce discretionary access control on hardlinks.

Rule ID

SV-282553r1200639_rule

STIG

Tri-Lab Operating System Stack (TOSS) 5 Security Technical Implementation Guide

Version

V1R1

CCIs

CCI-002165 CCI-002235

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 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 Text

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