fix: harden tarball extraction against symlink traversal and stderr OOM - #39
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## Why `src/rivet-fetch.js` invoked `tar -xz --strip-components=1 -C destDir` with no symlink guard. A malicious PR head ref could include a symlink in the tarball pointing outside `destDir`; subsequent `runRivetOracle` reads `rivet.yaml` from that target — a path-traversal vector. Additionally, unbounded `stderr` accumulation on pathological tar output could OOM the worker, and `tar.stdout` was piped but never drained — verbose tar output would block the child. ## What - Add `--no-same-owner` and `--no-same-permissions` to the tar invocation; defensive even though we run as a single user. - Drain `tar.stdout` (`.resume()`) so a verbose tar can't deadlock on a full pipe buffer. - Cap `stderr` accumulation at 64 KiB; mark the message `(stderr truncated)` on overflow. - Post-extract, walk `destDir` and reject any symlink whose `path.resolve`d target escapes the directory. Reject by `fs.unlinkSync` and throwing. - Export `assertNoEscapingSymlinks` for direct unit-testability. ## Source Wave-1 Security auditor flagged this as Bug #15 in `docs/agent-fleet/bugs.md`. ## Test plan - [x] 814 tests pass (was 806; +8 covering: hardening flags applied, stdout drained, stderr capped, escaping absolute symlink rejected, escaping relative `..` symlink rejected, benign tree accepted, in-bounds symlink accepted) - [x] eslint clean ## Risk & rollout - Risk: low. The rejected cases are anomalous (escaping symlinks); benign archives extract identically. - Rollout: self-update on merge. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Fixes Bug #15 from
docs/agent-fleet/bugs.md(wave-1 Security auditor).Hardens
src/rivet-fetch.js:--no-same-owner --no-same-permissionson tarDrain
tar.stdoutto prevent pipe-buffer deadlockCap
stderrat 64 KiBPost-extract symlink walk rejects any link escaping destDir
814 tests pass (+8)
eslint clean
🤖 Generated with Claude Code