fix: constrain extractFile reads to the unpacked directory#451
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readFileWithFd joined the requested filename onto the `<root>.unpacked` directory without checking containment, so a filename containing `..` segments could resolve to a path outside that directory. Route the read through the existing ensureWithin helper (matching readFileSync) so reads are constrained to the unpacked directory and an escaping filename throws. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_0155o3ELzXMVngciL3ZsqXgA
MarshallOfSound
approved these changes
Jun 28, 2026
ckerr
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Jun 29, 2026
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Requested by Samuel Attard · Slack thread
Before
When reading an unpacked file,
extractFile(viareadFileWithFd) joined the requestedfilenameonto<root>.unpackedwithpath.joinand no containment check. Afilenamecontaining..segments could therefore resolve to a path outside the.unpackeddirectory, causing the read to land somewhere it shouldn't.After
Reads are now constrained to the
.unpackeddirectory. Afilenamethat resolves outside it throws instead of reading the out-of-bounds path. This bringsreadFileWithFdin line withreadFileSync, which already routed its unpacked read through the containment check.How
readFileWithFdnow resolves the target through the existingensureWithin(base, filename)helper (wherebase =${filesystem.getRootPath()}.unpacked``), the same helperreadFileSyncalready uses. `ensureWithin` resolves the path with `path.resolve` and throws when the result is neither equal to the base nor under `base + path.sep`. Both unpacked-read call sites now go through this single helper.Added tests in
test/disk-spec.tscovering bothreadFileSyncandreadFileWithFd: each reads a normal file within.unpackedsuccessfully, and each throws when given a..-containing filename that resolves outside the unpacked directory.🤖 Generated with Claude Code
https://claude.ai/code/session_0155o3ELzXMVngciL3ZsqXgA