[api-minor] Clear all caches in XRef.indexObjects, and improve /Root dictionary validation in XRef.parse (issue 14303)
#14338
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…t dictionary validation in `XRef.parse` (issue 14303) *This patch improves handling of a couple of PDF documents from issue 14303.* - Update `XRef.indexObjects` to actually clear *all* XRef-caches. Invalid XRef tables *usually* cause issues early enough during parsing that we've not populated the XRef-cache, however to prevent any issues we obviously need to clear that one as well. - Improve the /Root dictionary validation in `XRef.parse` (PR 9827 follow-up). In addition to checking that a /Pages entry exists, we'll now also check that it can be successfully fetched *and* that it's of the correct type. There's really no point trying to use a /Root dictionary that e.g. `Catalog.toplevelPagesDict` will reject, and this way we'll be able to fallback to indexing the objects in corrupt documents. - Throw an `InvalidPDFException`, rather than a general `FormatError`, in `XRef.parse` when no usable /Root dictionary could be found. That really seems more appropriate overall, since all attempts at parsing/recovery have failed. (This part of the patch is API-observable, hence the tag.) With these changes, two existing test-cases are improved and the unit-tests are updated/re-factored to highlight that. In particular `GHOSTSCRIPT-698804-1-fuzzed.pdf` will now both load and "render" correctly, whereas `poppler-395-0-fuzzed.pdf` will now fail immediately upon loading (rather than *appearing* to work).
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/botio test |
From: Bot.io (Linux m4)ReceivedCommand cmd_test from @Snuffleupagus received. Current queue size: 0 Live output at: http://54.241.84.105:8877/46932625e377ffb/output.txt |
From: Bot.io (Windows)ReceivedCommand cmd_test from @Snuffleupagus received. Current queue size: 0 Live output at: http://54.193.163.58:8877/12bada7e2c6d489/output.txt |
From: Bot.io (Linux m4)FailedFull output at http://54.241.84.105:8877/46932625e377ffb/output.txt Total script time: 21.03 mins
Image differences available at: http://54.241.84.105:8877/46932625e377ffb/reftest-analyzer.html#web=eq.log |
From: Bot.io (Windows)FailedFull output at http://54.193.163.58:8877/12bada7e2c6d489/output.txt Total script time: 42.10 mins
Image differences available at: http://54.193.163.58:8877/12bada7e2c6d489/reftest-analyzer.html#web=eq.log |
timvandermeij
approved these changes
Dec 4, 2021
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LGTM. Thank you for improving this! |
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This patch improves handling of a couple of PDF documents from issue #14303.
Update
XRef.indexObjectsto actually clear all XRef-caches. Invalid XRef tables usually cause issues early enough during parsing that we've not populated the XRef-cache, however to prevent any issues we obviously need to clear that one as well.Improve the /Root dictionary validation in
XRef.parse(PR Fix various corrupt PDF files (issue 9252, issue 9418) #9827 follow-up). In addition to checking that a /Pages entry exists, we'll now also check that it can be successfully fetched and that it's of the correct type. There's really no point trying to use a /Root dictionary that e.g.Catalog.toplevelPagesDictwill reject, and this way we'll be able to fallback to indexing the objects in corrupt documents.Throw an
InvalidPDFException, rather than a generalFormatError, inXRef.parsewhen no usable /Root dictionary could be found. That really seems more appropriate overall, since all attempts at parsing/recovery have failed. (This part of the patch is API-observable, hence the tag.)With these changes, two existing test-cases are improved and the unit-tests are updated/re-factored to highlight that. In particular
GHOSTSCRIPT-698804-1-fuzzed.pdfwill now both load and "render" correctly, whereaspoppler-395-0-fuzzed.pdfwill now fail immediately upon loading (rather than appearing to work).