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V-274170

CAT II (Medium)

Amazon Linux 2023 must enable kernel parameters to enforce discretionary access control on symlinks.

Rule ID

SV-274170r1120498_rule

STIG

Amazon Linux 2023 Security Technical Implementation Guide

Version

V1R3

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 Amazon Linux 2023 is configured to enable DAC on symlinks.

Check the status of the fs.protected_symlinks kernel parameter with 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 Amazon Linux 2023 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 with the following command:

$ sudo sysctl --system