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Fix integer overflow in CodedInputStream::ReadLengthAndPushLimit #29523

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Fix integer overflow in CodedInputStream::ReadLengthAndPushLimit #29523

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5 changes: 4 additions & 1 deletion src/google/protobuf/io/coded_stream.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -150,7 +150,10 @@ CodedInputStream::IncrementRecursionDepthAndPushLimit(int byte_limit) {

CodedInputStream::Limit CodedInputStream::ReadLengthAndPushLimit() {
uint32_t length;
return PushLimit(ReadVarint32(&length) ? length : 0);
return PushLimit(ReadVarint32(&length) &&
length <= static_cast<uint32_t>(INT_MAX)
? static_cast<int>(length)
: 0);
}

bool CodedInputStream::DecrementRecursionDepthAndPopLimit(Limit limit) {
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15 changes: 15 additions & 0 deletions src/google/protobuf/io/coded_stream_unittest.cc
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Expand Up @@ -1576,6 +1576,21 @@ TEST_F(CodedStreamTest, RecursionLimit) {
EXPECT_FALSE(coded_input.IncrementRecursionDepth()); // 7
}

TEST_F(CodedStreamTest, ReadLengthAndPushLimitOverflow) {
// Varint encoding of 0x80000000 (2147483648, which overflows signed int32)
uint8_t bytes[] = {0x80, 0x80, 0x80, 0x80, 0x08, 'h', 'e', 'l', 'l', 'o'};
ArrayInputStream input(bytes, sizeof(bytes));
CodedInputStream coded_input(&input);

// When ReadLengthAndPushLimit encounters a length > INT_MAX, it must push limit 0
// so the stream is immediately bounded at 0 remaining bytes instead of overflowing
// into an unconstrained negative limit.
CodedInputStream::Limit limit = coded_input.ReadLengthAndPushLimit();
EXPECT_EQ(0, coded_input.BytesUntilLimit());
EXPECT_TRUE(coded_input.ConsumedEntireMessage());
coded_input.PopLimit(limit);
}


class ReallyBigInputStream : public ZeroCopyInputStream {
public:
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