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Cargo extracting malicious crates can corrupt arbitrary files

Low severity GitHub Reviewed Published Sep 14, 2022 in rust-lang/cargo • Updated Aug 14, 2023

Package

cargo cargo (Rust)

Affected versions

< 0.65.0
= 0.66.0

Patched versions

0.65.0
0.67.0

Description

The Rust Security Response WG was notified that Cargo did not prevent extracting some malformed packages downloaded from alternate registries. An attacker able to upload packages to an alternate registry could corrupt arbitary files when Cargo downloaded the package.

The severity of this vulnerability is "low" for users of alternate registries. Users relying on crates.io are not affected.

Note that by design Cargo allows code execution at build time, due to build scripts and procedural macros. The vulnerabilities in this advisory allow performing a subset of the possible damage in a harder to track down way. Your dependencies must still be trusted if you want to be protected from attacks, as it's possible to perform the same attacks with build scripts and procedural macros.

Arbitrary file corruption

After a package is downloaded, Cargo extracts its source code in the ~/.cargo folder on disk, making it available to the Rust projects it builds. To record when an extraction is successfull, Cargo writes "ok" to the .cargo-ok file at the root of the extracted source code once it extracted all the files.

It was discovered that Cargo allowed packages to contain a .cargo-ok symbolic link, which Cargo would extract. Then, when Cargo attempted to write "ok" into .cargo-ok, it would actually replace the first two bytes of the file the symlink pointed to with ok. This would allow an attacker to corrupt one file on the machine using Cargo to extract the package.

Affected versions

The vulnerability is present in all versions of Cargo. Rust 1.64, to be released on September 22nd, will include a fix for it.

Since the vulnerability is just a more limited way to accomplish what a malicious build scripts or procedural macros can do, we decided not to publish Rust point releases backporting the security fix. Patch files are available for Rust 1.63.0 are available in the wg-security-response repository for people building their own toolchain.

Mitigations

We recommend users of alternate registries to excercise care in which package they download, by only including trusted dependencies in their projects. Please note that even with these vulnerabilities fixed, by design Cargo allows arbitrary code execution at build time thanks to build scripts and procedural macros: a malicious dependency will be able to cause damage regardless of these vulnerabilities.

crates.io implemented server-side checks to reject these kinds of packages years ago, and there are no packages on crates.io exploiting these vulnerabilities. crates.io users still need to excercise care in choosing their dependencies though, as remote code execution is allowed by design there as well.

Acknowledgements

We want to thank Ori Hollander from JFrog Security Research for responsibly disclosing this to us according to the Rust security policy.

We also want to thank Josh Triplett for developing the fixes, Weihang Lo for developing the tests, and Pietro Albini for writing this advisory. The disclosure was coordinated by Pietro Albini and Josh Stone.

References

@pietroalbini pietroalbini published to rust-lang/cargo Sep 14, 2022
Published by the National Vulnerability Database Sep 14, 2022
Published to the GitHub Advisory Database Sep 16, 2022
Reviewed Sep 16, 2022
Last updated Aug 14, 2023

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
High
User interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L

EPSS score

0.272%
(68th percentile)

CVE ID

CVE-2022-36113

GHSA ID

GHSA-rfj2-q3h3-hm5j

Source code

Credits

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