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Add further sanity check to QPDF::reconstruct_xref

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If reconstruct_xref generates more than 1000 warnings give up because the
file is so severely damaged that there is very little point continuing.
This commit is contained in:
m-holger 2024-07-11 12:22:57 +01:00
parent c2c1618e08
commit e914bbbbbc
2 changed files with 15 additions and 19 deletions
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15
libqpdf/QPDF.cc
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@ -543,6 +543,10 @@ QPDF::reconstruct_xref(QPDFExc& e)
throw e; throw e;
} }
// If recovery generates more than 1000 warnings, the file is so severely damaged that there
// probably is no point trying to continue.
const auto max_warnings = m->warnings.size() + 1000U;
m->reconstructed_xref = true; m->reconstructed_xref = true;
// We may find more objects, which may contain dangling references. // We may find more objects, which may contain dangling references.
m->fixed_dangling_refs = false; m->fixed_dangling_refs = false;
@ -596,6 +600,9 @@ QPDF::reconstruct_xref(QPDFExc& e)
setTrailer(t); setTrailer(t);
} }
} }
if (m->warnings.size() > max_warnings) {
throw damagedPDF("", 0, "too many errors while reconstructing cross-reference table");
}
m->file->seek(next_line_start, SEEK_SET); m->file->seek(next_line_start, SEEK_SET);
line_start = next_line_start; line_start = next_line_start;
} }
@ -622,6 +629,10 @@ QPDF::reconstruct_xref(QPDFExc& e)
max_offset = offset; max_offset = offset;
setTrailer(oh.getDict()); setTrailer(oh.getDict());
} }
if (m->warnings.size() > max_warnings) {
throw damagedPDF(
"", 0, "too many errors while reconstructing cross-reference table");
}
} }
if (max_offset > 0) { if (max_offset > 0) {
try { try {
@ -646,7 +657,9 @@ QPDF::reconstruct_xref(QPDFExc& e)
// creating QPDF objects from JSON. // creating QPDF objects from JSON.
throw damagedPDF("", 0, "unable to find objects while recovering damaged file"); throw damagedPDF("", 0, "unable to find objects while recovering damaged file");
} }
if (m->warnings.size() > max_warnings) {
throw damagedPDF("", 0, "too many errors while reconstructing cross-reference table");
}
// We could iterate through the objects looking for streams and try to find objects inside of // We could iterate through the objects looking for streams and try to find objects inside of
// them, but it's probably not worth the trouble. Acrobat can't recover files with any errors // them, but it's probably not worth the trouble. Acrobat can't recover files with any errors
// in an xref stream, and this would be a real long shot anyway. If we wanted to do anything // in an xref stream, and this would be a real long shot anyway. If we wanted to do anything

19
qpdf/qtest/qpdf/issue-335a.out
View File

@ -1003,21 +1003,4 @@ WARNING: issue-335a.pdf (trailer, offset 20601): unexpected )
WARNING: issue-335a.pdf (trailer, offset 20602): unknown token while reading object; treating as string WARNING: issue-335a.pdf (trailer, offset 20602): unknown token while reading object; treating as string
WARNING: issue-335a.pdf (trailer, offset 20604): invalid character ({) in hexstring WARNING: issue-335a.pdf (trailer, offset 20604): invalid character ({) in hexstring
WARNING: issue-335a.pdf (trailer, offset 20604): too many errors; giving up on reading object WARNING: issue-335a.pdf (trailer, offset 20604): too many errors; giving up on reading object
WARNING: issue-335a.pdf (trailer, offset 20446): unknown token while reading object; treating as string qpdf: issue-335a.pdf: too many errors while reconstructing cross-reference table
WARNING: issue-335a.pdf (trailer, offset 20601): unexpected )
WARNING: issue-335a.pdf (trailer, offset 20602): unknown token while reading object; treating as string
WARNING: issue-335a.pdf (trailer, offset 20604): invalid character ({) in hexstring
WARNING: issue-335a.pdf (trailer, offset 20606): treating unexpected brace token as null
WARNING: issue-335a.pdf (trailer, offset 20607): treating unexpected brace token as null
WARNING: issue-335a.pdf (trailer, offset 20607): too many errors; giving up on reading object
WARNING: issue-335a.pdf (trailer, offset 20598): unknown token while reading object; treating as string
WARNING: issue-335a.pdf (trailer, offset 20600): unexpected )
WARNING: issue-335a.pdf (trailer, offset 20601): unexpected )
WARNING: issue-335a.pdf (trailer, offset 20602): unknown token while reading object; treating as string
WARNING: issue-335a.pdf (trailer, offset 20604): invalid character ({) in hexstring
WARNING: issue-335a.pdf (trailer, offset 20606): treating unexpected brace token as null
WARNING: issue-335a.pdf (trailer, offset 20606): too many errors; giving up on reading object
WARNING: issue-335a.pdf (trailer, offset 20684): unknown token while reading object; treating as string
WARNING: issue-335a.pdf (trailer, offset 20683): expected dictionary key but found non-name object; inserting key /QPDFFake1
WARNING: issue-335a.pdf (trailer, offset 20747): stream keyword found in trailer
qpdf: issue-335a.pdf: unable to find /Root dictionary