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

V-282554

CAT II (Medium)

TOSS 5 must enable kernel parameters to enforce discretionary access control (DAC) on symlinks.

Rule ID

SV-282554r1201608_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_symlinks" kernel parameter, symbolic links are permitted to be followed only when outside a sticky world-writable directory, or when the user identifier (UID) of the link and follower match, or when the directory owner matches the symlink's owner. Disallowing such symlinks helps mitigate 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 symlinks using the following command:

$ sudo sysctl fs.protected_symlinks

fs.protected_symlinks = 1

If "fs.protected_symlinks " is not set to "1" or is missing, this is a finding.

Fix Text

Configure TOSS 5 to enable DAC on symlinks with the following:

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

fs.protected_symlinks = 1

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

$ sudo sysctl --system