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LibPDF: Skip inline image data in operator stream

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Inline images can contain arbitrary binary data in the operator stream,
greatly confusing the operator parser.

Just skip them for now. They'll produce a
`Rendering of feature not supported: draw operation: inline_image_begin`
diag as usual, so we won't forget about it.

After #21536, reduces number of crashes on 300 random PDFs from the web
(the first 300 from 0000.zip from
https://pdfa.org/new-large-scale-pdf-corpus-now-publicly-available/)
from 23 (7%) to 22 (7%).

On a larger sample (`Meta/test_pdf.py -n 500 ~/Downloads/0000`),
reduces number of crashes from 53 (10.6%) with 36 distinct crash
stacks to 46 (9.2%) with 33 distinct stacks.
This commit is contained in:
Nico Weber 2023-10-21 22:19:06 -04:00 • committed by Andreas Kling
parent e108f394bf
commit a1f17bd643
1 changed files with 26 additions and 1 deletions
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27
Userland/Libraries/LibPDF/Parser.cpp
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@ -531,10 +531,35 @@ PDFErrorOr<Vector<Operator>> Parser::parse_operators()
}
auto operator_string = StringView(m_reader.bytes().slice(operator_start, m_reader.offset() - operator_start));
m_reader.consume_whitespace();
auto operator_type = Operator::operator_type_from_symbol(operator_string);
// Inline images contain a dictionary containing arbitrary values between BI and ID,
// and then arbitrary binary data between ID and EI.
// This means they need a special code path in the parser, so that image data in there doesn't confuse the operator parser.
if (operator_type == OperatorType::InlineImageBegin) {
if (!operator_args.is_empty())
return error("operator args not empty on start of inline image");
while (!m_reader.done()) {
if (m_reader.matches("EI")) {
break;
}
m_reader.consume();
}
if (m_reader.done())
return error("operator stream ended inside inline image");
m_reader.consume(2); // "EI"
m_reader.consume_whitespace();
// FIXME: Do more with inline images than just skipping them.
}
operators.append(Operator(operator_type, move(operator_args)));
operator_args = Vector<Value>();
m_reader.consume_whitespace();
continue;
}