rustsec-2023-0018
Vulnerability from osv_rustsec
The remove_dir_all crate is a Rust library that offers additional features over the Rust standard library fs::remove_dir_all function.
It was possible to trick a privileged process doing a recursive delete in an attacker controlled directory into deleting privileged files, on all operating systems.
For instance, consider deleting a tree called 'etc' in a parent directory
called 'p'. Between calling remove_dir_all("a") and remove_dir_all("a")
actually starting its work, the attacker can move 'p' to 'p-prime', and
replace 'p' with a symlink to '/'. Then the privileged process deletes 'p/etc'
which is actually /etc, and now your system is broken. There are some
mitigations for this exact scenario, such as CWD relative file lookup, but
they are not guaranteed - any code using absolute paths will not have that
protection in place.
The same attack could be performed at any point in the directory tree being deleted: if 'a' contains a child directory called 'etc', attacking the deletion by replacing 'a' with a link is possible.
The new code in this release mitigates the attack within the directory tree being deleted by using file-handle relative operations: to open 'a/etc', the path 'etc' relative to 'a' is opened, where 'a' is represented by a file descriptor (Unix) or handle (Windows). With the exception of the entry points into the directory deletion logic, this is robust against manipulation of the directory hierarchy, and remove_dir_all will only delete files and directories contained in the tree it is deleting.
The entry path however is a challenge - as described above, there are some potential mitigations, but since using them must be done by the calling code, it is hard to be confident about the security properties of the path based interface.
The new extension trait RemoveDir provides an interface where it is much
harder to get it wrong.
somedir.remove_dir_contents("name-of-child").
Callers can then make their own security evaluation about how to securely get
a directory handle. That is still not particularly obvious, and we're going to
follow up with a helper of some sort (probably in the fs_at crate). Once
that is available, the path based entry points will get deprecated.
In the interim, processes that might run with elevated privileges should
figure out how to securely identify the directory they are going to delete, to
avoid the initial race. Pragmatically, other processes should be fine with the
path based entry points : this is the same interface std::fs::remove_dir_all
offers, and an unprivileged process running in an attacker controlled
directory can't do anything that the attacker can't already do.
{
"affected": [
{
"database_specific": {
"categories": [],
"cvss": null,
"informational": null
},
"ecosystem_specific": {
"affected_functions": null,
"affects": {
"arch": [],
"functions": [
"remove_dir_all::ensure_empty_dir",
"remove_dir_all::remove_dir_all",
"remove_dir_all::remove_dir_contents"
],
"os": []
}
},
"package": {
"ecosystem": "crates.io",
"name": "remove_dir_all",
"purl": "pkg:cargo/remove_dir_all"
},
"ranges": [
{
"events": [
{
"introduced": "0.0.0-0"
},
{
"fixed": "0.8.0"
}
],
"type": "SEMVER"
}
],
"versions": []
}
],
"aliases": [
"GHSA-mc8h-8q98-g5hr"
],
"database_specific": {
"license": "CC0-1.0"
},
"details": "The remove_dir_all crate is a Rust library that offers additional features over the Rust\nstandard library fs::remove_dir_all function.\n\nIt was possible to trick a privileged process doing a recursive delete in an\nattacker controlled directory into deleting privileged files, on all operating systems.\n\nFor instance, consider deleting a tree called \u0027etc\u0027 in a parent directory\ncalled \u0027p\u0027. Between calling `remove_dir_all(\"a\")` and remove_dir_all(\"a\")\nactually starting its work, the attacker can move \u0027p\u0027 to \u0027p-prime\u0027, and\nreplace \u0027p\u0027 with a symlink to \u0027/\u0027. Then the privileged process deletes \u0027p/etc\u0027\nwhich is actually /etc, and now your system is broken. There are some\nmitigations for this exact scenario, such as CWD relative file lookup, but\nthey are not guaranteed - any code using absolute paths will not have that\nprotection in place.\n\nThe same attack could be performed at any point in the directory tree being\ndeleted: if \u0027a\u0027 contains a child directory called \u0027etc\u0027, attacking the\ndeletion by replacing \u0027a\u0027 with a link is possible.\n\nThe new code in this release mitigates the attack within the directory tree\nbeing deleted by using file-handle relative operations: to open \u0027a/etc\u0027, the\npath \u0027etc\u0027 relative to \u0027a\u0027 is opened, where \u0027a\u0027 is represented by a file\ndescriptor (Unix) or handle (Windows). With the exception of the entry points\ninto the directory deletion logic, this is robust against manipulation of the\ndirectory hierarchy, and remove_dir_all will only delete files and directories\ncontained in the tree it is deleting.\n\nThe entry path however is a challenge - as described above, there are some\npotential mitigations, but since using them must be done by the calling code,\nit is hard to be confident about the security properties of the path based\ninterface.\n\nThe new extension trait `RemoveDir` provides an interface where it is much\nharder to get it wrong.\n\n`somedir.remove_dir_contents(\"name-of-child\")`.\n\nCallers can then make their own security evaluation about how to securely get\na directory handle. That is still not particularly obvious, and we\u0027re going to\nfollow up with a helper of some sort (probably in the `fs_at` crate). Once\nthat is available, the path based entry points will get deprecated.\n\nIn the interim, processes that might run with elevated privileges should\nfigure out how to securely identify the directory they are going to delete, to\navoid the initial race. Pragmatically, other processes should be fine with the\npath based entry points : this is the same interface `std::fs::remove_dir_all`\noffers, and an unprivileged process running in an attacker controlled\ndirectory can\u0027t do anything that the attacker can\u0027t already do.",
"id": "RUSTSEC-2023-0018",
"modified": "2023-03-04T21:50:30Z",
"published": "2023-02-24T12:00:00Z",
"references": [
{
"type": "PACKAGE",
"url": "https://crates.io/crates/remove_dir_all"
},
{
"type": "ADVISORY",
"url": "https://rustsec.org/advisories/RUSTSEC-2023-0018.html"
},
{
"type": "WEB",
"url": "https://github.com/XAMPPRocky/remove_dir_all/commit/7247a8b6ee59fc99bbb69ca6b3ca4bfd8c809ead"
},
{
"type": "ADVISORY",
"url": "https://github.com/advisories/GHSA-mc8h-8q98-g5hr"
}
],
"related": [],
"severity": [],
"summary": "Race Condition Enabling Link Following and Time-of-check Time-of-use (TOCTOU)"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.