Bug 1197871 (CVE-2022-27650)

Summary: VUL-0: CVE-2022-27650: crun: Default inheritable capabilities for linux container should be empty
Product: [openSUSE] openSUSE Tumbleweed Reporter: Thomas Leroy <thomas.leroy>
Component: SecurityAssignee: Dario Faggioli <dfaggioli>
Status: NEW --- QA Contact: Security Team bot <security-team>
Severity: Normal    
Priority: P3 - Medium    
Version: Current   
Target Milestone: ---   
Hardware: Other   
OS: Other   
URL: https://smash.suse.de/issue/327613/
Whiteboard:
Found By: --- Services Priority:
Business Priority: Blocker: ---
Marketing QA Status: --- IT Deployment: ---

Description Thomas Leroy 2022-03-31 12:11:19 UTC
rh#2066845

A bug was found in Moby (Docker Engine) where containers were incorrectly started with non-empty inheritable Linux process capabilities, creating an atypical Linux environment and enabling programs with inheritable file capabilities to elevate those capabilities to the permitted set during execve(2). Normally, when executable programs have specified permitted file capabilities, otherwise unprivileged users and processes can execute those programs and gain the specified file capabilities up to the bounding set. Due to this bug, containers which included executable programs with inheritable file capabilities allowed otherwise unprivileged users and processes to additionally gain these inheritable file capabilities up to the container's bounding set. Containers which use Linux users and groups to perform privilege separation inside the container are most directly impacted.

This bug did not affect the container security sandbox as the inheritable set never contained more capabilities than were included in the container's bounding set.

Patches
This bug has been fixed in Moby (Docker Engine) 20.10.14. Users should update to this version as soon as possible. Running containers should be stopped, deleted, and recreated for the inheritable capabilities to be reset.

This fix changes Moby (Docker Engine) behavior such that containers are started with a more typical Linux environment. Refer to capabilities(7) for a description of how capabilities work. Note that permitted file capabilities continue to allow for privileges to be raised up to the container's bounding set and that processes may add capabilities to their own inheritable set up to the container's bounding set per the rules described in the manual page. In all cases the container's bounding set provides an upper bound on the capabilities that can be assumed and provides for the container security sandbox.

Workarounds
The entrypoint of a container can be modified to use a utility like capsh(1) to drop inheritable capabilities prior to the primary process starting.

References:
https://bugzilla.redhat.com/show_bug.cgi?id=2066845
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2022-27650
Comment 1 Thomas Leroy 2022-03-31 12:14:50 UTC
This is related to CVE-2022-27650.

openSUSE:Factory should be affected.

Upstream fix commits:
https://github.com/containers/crun/commit/1aeeed2e4fdeffb4875c0d0b439915894594c8c6
https://github.com/containers/crun/commit/b847d146d496c9d7beba166fd595488e85488562