CVE-2023-42456 (published 2023-09-21T16:15Z)

Sudo-rs, a memory safe implementation of sudo and su, allows users to not have to enter authentication at every sudo attempt, but instead only requiring authentication every once in a while in every terminal or process group. Only once a configurable timeout has passed will the user have to re-authenticate themselves. Supporting this functionality is a set of session files (timestamps) for each user, stored in `/var/run/sudo-rs/ts`. These files are named according to the username from which the sudo attempt is made (the origin user).\n\nAn issue was discovered in versions prior to 0.2.1 where usernames containing the `.` and `/` characters could result in the corruption of specific files on the filesystem. As usernames are generally not limited by the characters they can contain, a username appearing to be a relative path can be constructed. For example we could add a user to the system containing the username `../../../../bin/cp`. When logged in as a user with that name, that user could run `sudo -K` to clear their session record file. The session code then constructs the path to the session file by concatenating the username to the session file storage directory, resulting in a resolved path of `/bin/cp`. The code then clears that file, resulting in the `cp` binary effectively being removed from the system.\n\nAn attacker needs to be able to login as a user with a constructed username. Given that such a username is unlikely to exist on an existing system, they will also need to be able to create the users with the constructed usernames.\n\nThe issue is patched in version 0.2.1 of sudo-rs. Sudo-rs now uses the uid for the user instead of their username for determining the filename. Note that an upgrade to this version will result in existing session files being ignored and users will be forced to re-authenticate. It also fully eliminates any possibility of path traversal, given that uids are always integer values.\n\nThe `sudo -K` and `sudo -k` commands can run, even if a user has no sudo access. As a workaround, make sure that one's system does not contain any users with a specially crafted username. While this is the case and while untrusted users do not have the ability to create arbitrary users on the system, one should not be able to exploit this issue.

CVSS v3 base score: 8.1, HIGH (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H)

Weakness information:
cwe_id: CWE-22
cwe_name: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
description: The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
extended_description: 
            Many file operations are intended to take place within a restricted directory. By using special elements such as ".." and "/" separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the "../" sequence, which in most modern operating systems is interpreted as the parent directory of the current location. This is referred to as relative path traversal. Path traversal also covers the use of absolute pathnames such as "/usr/local/bin" to access unexpected files. This is referred to as absolute path traversal.
         
         
cwe_id: CWE-23
cwe_name: Relative Path Traversal
description: The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.
extended_description: This allows attackers to traverse the file system to access files or directories that are outside of the restricted directory.
         

Fix information:
repo_url: https://github.com/memorysafety/sudo-rs
commit_details: repo_url: https://github.com/memorysafety/sudo-rs
author: Ruben Nijveld
author_date: 2023-09-21 16:23:07+02:00
msg: Merge pull request from GHSA-2r3c-m6v7-9354

Use uid instead of username for storing session files
repository: repo_url: https://github.com/memorysafety/sudo-rs
repo_name: trifectatechfoundation/sudo-rs
description: A memory safe implementation of sudo and su.
repo_language: Rust
owner: memorysafety