Fix path traversal vulnerability in cache.go#1795
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antitree wants to merge 1 commit intochainguard-dev:mainfrom
Open
Fix path traversal vulnerability in cache.go#1795antitree wants to merge 1 commit intochainguard-dev:mainfrom
antitree wants to merge 1 commit intochainguard-dev:mainfrom
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Replace unsafe filepath.Clean + strings.HasPrefix validation with Go 1.24's os.Root for secure path resolution. This prevents path traversal attacks including symlink-based attacks. The previous validation could be bypassed with paths like "/cache-evil/file" which would pass the prefix check for root "/cache". 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>
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Aims to address https://github.com/chainguard-dev/internal-dev/issues/1593 |
tstromberg
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Aug 5, 2025
tstromberg
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To prevent a future regression, this should get a test.
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| // Return the absolute path for use by other functions | ||
| return filepath.Join(root, relativePath), nil |
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"root" isn't necessarily an absolute path; if this comment is to be accurate, you should use filepath.Abs.
| return "", fmt.Errorf("cache file %s is not within root %s", cacheFile, cleanroot) | ||
| relativePath := filepath.Join(repoDir, dir, filename) | ||
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| // Use os.Root for secure path validation to prevent path traversal |
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Look out for other calls to filepath.Join here to see whether or not they are similarly vulnerable - https://github.com/chainguard-dev/apko/pull/1795/files#diff-085f287e1519fcab77329f1fededeae7b771c1e18f0522e4c4f1fdbe3c202d3bR376 looks suspicious.
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Summary
pkg/apk/apk/cache.gofilepath.Clean+strings.HasPrefixvalidation with Go 1.24'sos.RootSecurity Issue
The previous validation in
cachePathFromURL()could be bypassed:Attack example: With root="/cache", a malicious path like "/cache-evil/file" would pass the prefix check.
Solution
Implemented Go 1.24's
os.Rootwhich provides:Test Plan
🤖 Generated with Claude Code