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[api-minor] Clear all caches in XRef.indexObjects, and improve /Root dictionary validation in XRef.parse (issue 14303)

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*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).
This commit is contained in:
Jonas Jenwald 2021-12-02 16:40:31 +01:00
parent e9e4b913c0
commit ad3a271fc4
2 changed files with 66 additions and 43 deletions
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25
src/core/xref.js
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@ -107,14 +107,26 @@ class XRef {
}
warn(`XRef.parse - Invalid "Root" reference: "${ex}".`);
}
if (root instanceof Dict && root.has("Pages")) {
this.root = root;
} else {
if (!recoveryMode) {
throw new XRefParseException();
if (root instanceof Dict) {
try {
const pages = root.get("Pages");
if (pages instanceof Dict) {
this.root = root;
return;
}
} catch (ex) {
if (ex instanceof MissingDataException) {
throw ex;
}
warn(`XRef.parse - Invalid "Pages" reference: "${ex}".`);
}
throw new FormatError("Invalid root reference");
}
if (!recoveryMode) {
throw new XRefParseException();
}
// Even recovery failed, there's nothing more we can do here.
throw new InvalidPDFException("Invalid Root reference.");
}
processXRefTable(parser) {
@ -417,6 +429,7 @@ class XRef {
// Clear out any existing entries, since they may be bogus.
this.entries.length = 0;
this._cacheMap.clear();
const stream = this.stream;
stream.pos = 0;