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LibPDF: Don't consider the End of Data code as normal ASCII85 input

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Data encoded with ASCII85 is terminated with the EOD code 0x7E3E. This
should not be considered as normal input but rather discarded.
This commit is contained in:
Lucas CHOLLET 2023-11-11 18:26:44 -05:00 committed by Andreas Kling
parent 59a6d4b7bc
commit 1e8004734f
Notes: sideshowbarker 2024-07-17 18:46:30 +09:00 
Author: https://github.com/LucasChollet
Commit: https://github.com/SerenityOS/serenity/commit/1e8004734f
Pull-request: https://github.com/SerenityOS/serenity/pull/21900
Reviewed-by: https://github.com/nico ✅
1 changed files with 18 additions and 2 deletions
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20
Userland/Libraries/LibPDF/Filter.cpp
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@ -94,6 +94,8 @@ PDFErrorOr<ByteBuffer> Filter::decode_ascii_hex(ReadonlyBytes bytes)
PDFErrorOr<ByteBuffer> Filter::decode_ascii85(ReadonlyBytes bytes)
{
// 3.3.2 ASCII85Decode Filter
ByteBuffer buffer;
TRY(buffer.try_ensure_capacity(bytes.size()));
@ -114,10 +116,21 @@ PDFErrorOr<ByteBuffer> Filter::decode_ascii85(ReadonlyBytes bytes)
u32 number = 0;
auto const to_write = byte_index + 5 >= bytes.size() ? bytes.size() - byte_index : 5;
auto to_write = byte_index + 5 >= bytes.size() ? bytes.size() - byte_index : 5;
Optional<u32> end_of_data_index {};
for (int i = 0; i < 5; i++) {
auto byte = byte_index >= bytes.size() ? 'u' : bytes[byte_index++];
// We check for the EOD sequence '~>', but as '~' can only appear in
// this sequence, there is no need to check for '>'.
if (!end_of_data_index.has_value() && bytes[byte_index] == '~') {
end_of_data_index = i;
to_write = i + 1;
}
bool const should_fake_end = byte_index >= bytes.size() || end_of_data_index.has_value();
auto const byte = should_fake_end ? 'u' : bytes[byte_index++];
if (Reader::is_whitespace(byte)) {
i--;
continue;
@ -127,6 +140,9 @@ PDFErrorOr<ByteBuffer> Filter::decode_ascii85(ReadonlyBytes bytes)
for (size_t i = 0; i < to_write - 1; i++)
buffer.append(reinterpret_cast<u8*>(&number)[3 - i]);
if (end_of_data_index.has_value())
break;
}
return buffer;