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fix(av-surface): no runnable base64-to-shell line on disk

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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>
This commit is contained in:
Kjell Tore Guttormsen 2026-09-23 11:35:50 +02:00
commit 58d2e8ad8d
Signed by: ktg
SSH key fingerprint: SHA256:JakMjO6FTBBzN0Bhfj9saOoEjaFxlSdYuZQQpM/lF9Q
4 changed files with 12 additions and 8 deletions
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examples/bash-evasion-gallery/README.md
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@ -35,7 +35,7 @@ techniques below are caught.
| T5 | IFS word-splitting | `rm${IFS}-rf${IFS}$HOME` | `rm -rf $HOME` |
| T6 | ANSI-C hex quoting | `$'\x72\x6d' -rf $HOME` | `rm -rf $HOME` |
| T7 | process substitution | `cat <(echo rm) -rf $HOME` | `cat echo rm -rf $HOME` |
| T8 | base64-pipe-shell idiom | `echo cm0gLXJmICRIT01F \| base64 -d \| sh` | (separate BLOCK_RULE — not normalization) |
| T8 | base64-pipe-shell idiom | `echo <base64 of the baseline command> \| base64 -d \| sh` | (separate BLOCK_RULE — not normalization) |
| T9 | eval-via-variable (one-level forward flow) | `X=rm; $X -rf $HOME` | `X=rm; rm -rf $HOME` |
The canonical destructive target throughout the gallery is