[overtrue]

AI-assisted; human review is pending.

Summary

s3s-fs normalizes object keys into filesystem paths, so deleting a key such as allowed/../victim can remove a different object. Reject dot segments, repeated separators and absolute paths before resolving them, and return per-key errors in batch deletion.

Changes

• Validate keys in the shared object-path helper, covering reads, writes, copies, multipart completion and deletion.
• Keep valid batch entries working before and after a rejected key; preserve the submitted key and version ID in the error.
• Add a regression that checks the bytes of sibling and other-bucket objects, plus path validation controls for ordinary filenames and Windows prefixes.

Behavior

The filesystem backend rejects these keys with InvalidArgument. Windows backslash keys are also rejected because they alias forward-slash paths on that platform. Dot filenames such as .config and report..txt, nested keys and directory objects remain accepted. Unix backslash filenames and other backends keep the existing S3 key rules.

Tests

• Red control on unmodified main: the batch regression fails because the seeded victim file is deleted. A separate red control on the previous PR head reproduces the repeated-separator deletion.
• just dev: passed; 3,609 tests passed, 5 existing tests ignored.
• just ci-rust: passed, including codegen idempotence and the clean-tree check.
• cargo +nightly clippy --workspace --all-targets --all-features -- -D warnings: passed (exit 0).

The local runs use macOS. Windows-specific path cases are included for CI.

AI

GPT-6 assisted with the investigation, patch and tests. The checks above ran locally; human review is pending.

[Copilot]

🟡 Changes recommended

Repeated separators remain a cross-key deletion alias despite the new validation.

1 open finding

• Reject repeated separators to prevent path alias authorization bypass · New

What changed in this PR

Hardens s3s-fs object-path handling and reports invalid batch-delete entries individually.

Changes:

• Rejects dot-segment and absolute object paths.
• Preserves valid batch deletions around rejected entries.
• Adds path-validation and deletion regressions.

File	Description
crates/​s3s-fs/​src/​fs.rs	Validates object paths and adds unit tests.
crates/​s3s-fs/​src/​s3.rs	Returns per-key deletion errors and adds regression coverage.

🧠 Review effort: Balanced

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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