Path traversal in Reposilite javadoc file expansion

Summary

Reposilite is an open source, lightweight and easy-to-use repository manager for Maven based artifacts in JVM ecosystem. Reposilite provides support for JavaDocs files, which are archives that contain documentation for artifacts. Specifically, JavadocEndpoints.kt controller allows to expand the javadoc archive into the server's file system and return its content. The problem is in the way how the archives are expanded, specifically how the new filename is created. The `file.name` taken from the archive can contain path traversal characters, such as '/../../../anything.txt', so the resulting extraction path can be outside the target directory. If the archive is taken from an untrusted source, such as Maven Central or JitPack for example, an attacker can craft a special archive to overwrite any local file on Reposilite instance. This could lead to remote code execution, for example by placing a new plugin into the '$workspace$/plugins' directory. Alternatively, an attacker can overwrite the content of any other package. Note that the attacker can use its own malicious package from Maven Central to overwrite any other package on Reposilite. Reposilite has addressed this issue in version 3.5.12. Users are advised to upgrade. There are no known workarounds for this vulnerability. This issue was discovered and reported by the GitHub Security lab and is also tracked as GHSL-2024-073.