RHEL-09-213035 - RHEL 9 must enable kernel parameters to enforce discretionary access control on symlinks.

Information

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

Solution

Configure RHEL 9 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

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_RHEL_9_V2R1_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-3(4), 800-53|AC-6(10), CAT|II, CCI|CCI-002165, CCI|CCI-002235, Rule-ID|SV-257802r958702_rule, STIG-ID|RHEL-09-213035, Vuln-ID|V-257802

Plugin: Unix

Control ID: 3f4864d3357015f7a866809fb4be76d379392edad4c17d139c9c418d075330b5