Fix a potential ZIP slip

[joehan]

Description

b/443293131 for context

[gemini-code-assist]

Summary of Changes

Hello @joehan, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the security of the application's file extraction process. By preventing a potential ZIP slip vulnerability, it safeguards against malicious archives attempting to write files to arbitrary locations on the filesystem, thereby improving overall system integrity and user safety.

Highlights

• Security Vulnerability Fix: Addressed a potential ZIP slip vulnerability in the unzip utility by implementing robust path validation to ensure extracted files remain within the designated output directory.

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[gemini-code-assist]

Code Review

This pull request aims to fix a potential ZIP slip vulnerability by validating that file paths from a ZIP archive are within the intended output directory. The approach is sound, but the implementation of the new isChildDir function contains a critical flaw. It attempts to resolve the real path of a destination file that hasn't been created yet, which will cause the unzip process to fail for every file. I've provided a detailed comment and a corrected implementation to address this issue.