Kjell Tore Guttormsen
58d2e8ad8d
PLAN § v8.1.3 tillegg a. The bash-evasion gallery's T8 comment held a complete base64-decode-into-shell line whose 16-char blob decodes to a home-directory deletion, under probe (b)'s 24-char floor. Probe (b2) found two more of the same shape, fixed here too: the gallery README's T8 row and tests/e2e/attack-chain.test.mjs (an /etc deletion). Chosen over an exception list because the gate should have none. The gallery and the e2e test now encode the blob at runtime from the same fragments; the README shows a placeholder. Gallery: 10/10 blocked. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
62 lines
2.7 KiB
Markdown
62 lines
2.7 KiB
Markdown
# Expected Findings — Bash Evasion Gallery
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This is the testable contract. `run-evasion-gallery.mjs` exits 0
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only when every T-tag produces a BLOCK.
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## Per-tag contract
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| Tag | Hook stderr must contain |
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|-----|--------------------------|
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| baseline | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T1 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T2 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T3 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T4 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T5 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T6 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T7 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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| T8 | `BLOCKED: Destructive command detected — T8 — base64-pipe-shell idiom (echo BLOB \| base64 -d \| sh)` |
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| T9 | `BLOCKED: Destructive command detected — Filesystem root destruction (rm -rf /)` |
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All cases must exit with code 2.
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## Why $HOME instead of /
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The "Filesystem root destruction" BLOCK_RULE regex requires a
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word-boundary anchor after the destination path:
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```
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\brm\s+(?:-[a-zA-Z]*f[a-zA-Z]*\s+|--force\s+)*-[a-zA-Z]*r[a-zA-Z]*\s+(?:\/|~|\$HOME)\b
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```
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`rm -rf /` ends with `/` followed by end-of-string; both `/` and
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EOL are non-word, so `\b` does not match. The variants
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`rm -rf /tmp`, `rm -rf $HOME`, and `rm -rf /etc` all match — the
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trailing word character provides the boundary.
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This gallery uses `$HOME` because it is unambiguously destructive
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and the regex fires deterministically. The literal `rm -rf /`
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edge case is not part of this contract — it is covered by Claude
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Code 2.1.98+ harness-level checks.
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## Side effects
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- No file is modified
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- No real `bash` is invoked — only `node hooks/scripts/...`
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- Each hook spawn has `tool_input.command` set to the disguised
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variant — bash never sees these strings
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- No mutation of `$HOME`, `/`, `/tmp`, or anywhere else
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## Notes for forks
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- If `bash-normalize.mjs` adds new T-tags (T10+), add a new case
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to `CASES` and a corresponding row above
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- If a BLOCK_RULE in `pre-bash-destructive.mjs` is renamed,
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update the stderr-pattern column above (the assertion lives
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in `expected-findings.md` for documentation; the run script
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only checks exit code 2, so it continues to pass after a
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rename)
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- The base64 blob in T8 (`T8_BLOB`) is built at runtime from the
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same fragments as the baseline command, so changing the
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canonical destructive target updates it too. No runnable
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base64-to-shell line is kept on disk (v8.1.3)
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