The two findings of the 18.09 PM checkpoint of `0f308c1`. Red tests landed
first in `3b587ea`; this is what turns them green.
BLOCKER -- `_check_inflated` read `filters[0]`, measured that one link and
returned, which is not a bound: a PDF decodes a stream through a LIST of
filters. Measured in paired subprocesses from two pinned trees, idle machine:
[/FlateDecode] 400 MB 408 516 B 59 232 256 -> 62 017 536 B
[/FlateDecode x2] 400 MB 1 636 B 886 554 624 -> 52 367 360 B
[/FlateDecode x3] 400 MB 1 070 B 889 393 152 -> 61 390 848 B
[/FlateDecode x2] 1,2 GB 2 927 B 2 567 204 864 -> 60 403 712 B
542 000x the file at two links, and the picture WAS refused at the end -- by
`check_payload` after `get_data()`, once the memory was spent. The single-link
row is the control and does not move. It also left the 16 corpus objects behind
an `[/ASCII85Decode /FlateDecode]` chain unmeasured, since `filters[0]` is not
`FlateDecode` there.
`_check_stream_cost` walks every link. THREE CLASSES and no fourth
(`extract.bounded_pdf_filters`, pinned by a test): `FlateDecode` MEASURED, a
link with another expanding link behind it inflated under the same bound and
handed on; `ASCII85Decode`/`ASCIIHexDecode` bounded by their own input because
they SHRINK; `DCTDecode`/`JPXDecode`/`JBIG2Decode` PASS THROUGH. Everything
else -- `LZWDecode`, `RunLengthDecode`, `CCITTFaxDecode`, `/Crypt`, anything
written later -- is refused UNREAD with a new code `asset_pdf_unbounded`,
decided before the FIRST link is decoded so a document cannot make the run pay
for the links in front of the one we cannot bound. An encrypted stream is
deciphered and then measured, where `stream.decipher is not None` used to
return unmeasured; 0 of 5 142 objects here are in an encrypted document, which
is why nothing caught it.
NOT ONE PICTURE CHANGES HANDS, AND IT IS MEASURED BY NAME. Every PDF on this
machine -- 78 documents, K2 in both trinn1 and trinn2, the shipped fixtures and
R761 -- run through `_pdf_images` page by page from both pinned trees:
images carried 9 356 -> 9 356
documents losing one 0 of 78
documents gaining one 0 of 78
asset_pdf_unsupported 322 -> 314
asset_pdf_unbounded 0 -> 8
The 8 are the 4 `CCITTFaxDecode` stencil masks (`/ImageMask true`,
`/BitsPerComponent 1`), counted twice because trinn1 and trinn2 hold the same
document. They were refused before and are refused now, one step earlier and
under a code that says why.
MAJOR -- `check_payload(len(data))` after `get_data()` is the counted refusal
four documentation surfaces point at, and deleting exactly that line passed all
2 132 tests. It is reachable through a stream pdfminer has ALREADY decoded
(`decode()` sets `rawdata` to `None`), which is now the ONLY case outside the
bound and has a test.
Eight mutations, one line each, every one DEAD, with the unmutated tree run
first as the control: first-link-only, loop dropped, inequality reversed,
encrypted skipped, backstop deleted, unknown filter passed through,
intermediate link not carried forward, whole check removed.
`tools/okf_accounting_gate.py` gains one line, the new code in
`REJECTION_CODES` -- what a rejection code requires and nothing more. Gate
unchanged: exit 1, GATE RED rows 2, 3, 6. Version stays 0.10.1, untagged.
Suite after `git add` against a clean tree: `uv run pytest -q` ->
2152 passed, 1 skipped (226 s). ruff, ruff format --check, mypy --strict clean.
Report: docs/2026-09-18-filterkjeden-og-backstoppen.md
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Kjell Tore Guttormsen
0c3c4904ee