Safe artifact extraction against traversal, links, and special files #2

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opened 2026-06-16 17:54:53 +00:00 by stephen · 0 comments

stephen commented

2026-06-16 17:54:53 +00:00

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Why

download-artifact extracts tar archives from shared storage with tar -xf into the destination. A malicious archive can attempt traversal, symlink overwrite, hardlinks, or special files unless entries are prevalidated.

Verified

src/lib/artifact-tar.js runs tar -xf - -C <dest> with no visible entry validation.
Upload creates relative archives, but cross-run/cross-repo download trusts storage metadata and object contents.
No existing download-artifact-action issues are filed.

Build

List and validate archive entries before extraction.
Reject absolute paths, .., symlink/hardlink escapes, device nodes, and ownership surprises.
Add malicious tar fixture tests.

## Why download-artifact extracts tar archives from shared storage with `tar -xf` into the destination. A malicious archive can attempt traversal, symlink overwrite, hardlinks, or special files unless entries are prevalidated. ## Verified - `src/lib/artifact-tar.js` runs `tar -xf - -C <dest>` with no visible entry validation. - Upload creates relative archives, but cross-run/cross-repo download trusts storage metadata and object contents. - No existing download-artifact-action issues are filed. ## Build - List and validate archive entries before extraction. - Reject absolute paths, `..`, symlink/hardlink escapes, device nodes, and ownership surprises. - Add malicious tar fixture tests.

stephen added the

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2026-06-16 17:54:53 +00:00

stephen referenced this issue from a commit

2026-06-16 23:26:59 +00:00

Validate tar entries before extraction (#2)

stephen referenced this issue

2026-06-16 23:27:07 +00:00

Validate tar entries before extraction (#2) #3

stephen referenced this issue from a commit

2026-06-16 23:35:06 +00:00