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Guard Parser::Deserialize BFBS identifier probes #9098

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22 changes: 16 additions & 6 deletions src/idl_parser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4421,14 +4421,24 @@ bool Definition::DeserializeAttributes(
/* DESERIALIZATION */
/************************************************************************/
bool Parser::Deserialize(const uint8_t* buf, const size_t size) {
if (!buf) return false;

flatbuffers::Verifier verifier(reinterpret_cast<const uint8_t*>(buf), size);
const size_t file_identifier_offset = sizeof(flatbuffers::uoffset_t);
const size_t size_prefixed_file_identifier_offset =
2 * sizeof(flatbuffers::uoffset_t);
const bool has_schema_identifier =
size >= file_identifier_offset + flatbuffers::kFileIdentifierLength &&
reflection::SchemaBufferHasIdentifier(buf);
const bool has_size_prefixed_schema_identifier =
size >= size_prefixed_file_identifier_offset +
flatbuffers::kFileIdentifierLength &&
flatbuffers::BufferHasIdentifier(buf, reflection::SchemaIdentifier(),
true);
bool size_prefixed = false;
if (!reflection::SchemaBufferHasIdentifier(buf)) {
if (!flatbuffers::BufferHasIdentifier(buf, reflection::SchemaIdentifier(),
true))
return false;
else
size_prefixed = true;
if (!has_schema_identifier) {
if (!has_size_prefixed_schema_identifier) return false;
size_prefixed = true;
}
auto verify_fn = size_prefixed
? &reflection::VerifySizePrefixedSchemaBuffer<false>
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19 changes: 19 additions & 0 deletions tests/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1171,6 +1171,24 @@ void TestEmbeddedBinarySchema(const std::string& tests_data_path) {
}
#endif

void TestDeserializeRejectsShortBinarySchemaBuffers() {
flatbuffers::Parser null_parser;
TEST_EQ(false, null_parser.Deserialize(nullptr, 0));
TEST_EQ(false,
null_parser.Deserialize(
nullptr, sizeof(flatbuffers::uoffset_t) +
flatbuffers::kFileIdentifierLength));

const size_t size_prefixed_identifier_size =
2 * sizeof(flatbuffers::uoffset_t) + flatbuffers::kFileIdentifierLength;
for (size_t size = 1; size < size_prefixed_identifier_size; size++) {
std::string buf(size, 'x');
flatbuffers::Parser parser;
TEST_EQ(false, parser.Deserialize(
reinterpret_cast<const uint8_t*>(buf.data()), size));
}
}

template <typename T>
void EmbeddedSchemaAccessByType() {
// Get the binary schema from the Type itself.
Expand Down Expand Up @@ -1765,6 +1783,7 @@ int FlatBufferTests(const std::string& tests_data_path) {
MiniReflectFixedLengthArrayTest();

SizePrefixedTest();
TestDeserializeRejectsShortBinarySchemaBuffers();

AlignmentTest();

Expand Down