[fuzzing] Fix chaotic good framer fuzzing bug (#36821)

Refines the test in the fuzzer to only check input == output if the frame was re-encodable.
Also tweaks some hpack encoder stuff to not crash but simply report errors where appropriate.

Closes #36821

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/36821 from ctiller:f-frame 1b08875c4e
PiperOrigin-RevId: 642311442

src/core/ext/transport/chaotic_good/chaotic_good_transport.h

@@ -52,7 +52,9 @@ class ChaoticGoodTransport : public RefCounted<ChaoticGoodTransport> {
   }
 
   auto WriteFrame(const FrameInterface& frame) {
-    auto buffers = frame.Serialize(&encoder_);
+    bool saw_encoding_errors = false;
+    auto buffers = frame.Serialize(&encoder_, saw_encoding_errors);
+    // ignore encoding errors: they will be logged separately already
     if (GRPC_TRACE_FLAG_ENABLED(chaotic_good)) {
       gpr_log(GPR_INFO, "CHAOTIC_GOOD: WriteFrame to:%s %s",
               ResolvedAddressToString(control_endpoint_.GetPeerAddress())

src/core/ext/transport/chaotic_good/client/chaotic_good_connector.cc

@@ -114,7 +114,10 @@ auto ChaoticGoodConnector::DataEndpointWriteSettingsFrame(
   frame.headers = SettingsMetadata{SettingsMetadata::ConnectionType::kData,
                                    self->connection_id_, kDataAlignmentBytes}
                       .ToMetadataBatch();
-  auto write_buffer = frame.Serialize(&self->hpack_compressor_);
+  bool saw_encoding_errors = false;
+  auto write_buffer =
+      frame.Serialize(&self->hpack_compressor_, saw_encoding_errors);
+  // ignore encoding errors: they will be logged separately already
   return self->data_endpoint_.Write(std::move(write_buffer.control));
 }
 
@@ -215,7 +218,10 @@ auto ChaoticGoodConnector::ControlEndpointWriteSettingsFrame(
   frame.headers = SettingsMetadata{SettingsMetadata::ConnectionType::kControl,
                                    absl::nullopt, absl::nullopt}
                       .ToMetadataBatch();
-  auto write_buffer = frame.Serialize(&self->hpack_compressor_);
+  bool saw_encoding_errors = false;
+  auto write_buffer =
+      frame.Serialize(&self->hpack_compressor_, saw_encoding_errors);
+  // ignore encoding errors: they will be logged separately already
   return self->control_endpoint_.Write(std::move(write_buffer.control));
 }
 

src/core/ext/transport/chaotic_good/frame.cc

@@ -218,10 +218,12 @@ absl::Status SettingsFrame::Deserialize(HPackParser* parser,
   return deserializer.Finish();
 }
 
-BufferPair SettingsFrame::Serialize(HPackCompressor* encoder) const {
+BufferPair SettingsFrame::Serialize(HPackCompressor* encoder,
+                                    bool& saw_encoding_errors) const {
   FrameSerializer serializer(FrameType::kSettings, 0);
   if (headers.get() != nullptr) {
-    encoder->EncodeRawHeaders(*headers.get(), serializer.AddHeaders());
+    saw_encoding_errors |=
+        !encoder->EncodeRawHeaders(*headers.get(), serializer.AddHeaders());
   }
   return serializer.Finish();
 }
@@ -275,11 +277,13 @@ absl::Status ClientFragmentFrame::Deserialize(HPackParser* parser,
   return deserializer.Finish();
 }
 
-BufferPair ClientFragmentFrame::Serialize(HPackCompressor* encoder) const {
+BufferPair ClientFragmentFrame::Serialize(HPackCompressor* encoder,
+                                          bool& saw_encoding_errors) const {
   CHECK_NE(stream_id, 0u);
   FrameSerializer serializer(FrameType::kFragment, stream_id);
   if (headers.get() != nullptr) {
-    encoder->EncodeRawHeaders(*headers.get(), serializer.AddHeaders());
+    saw_encoding_errors |=
+        !encoder->EncodeRawHeaders(*headers.get(), serializer.AddHeaders());
   }
   if (message.has_value()) {
     serializer.AddMessage(message.value());
@@ -354,17 +358,20 @@ absl::Status ServerFragmentFrame::Deserialize(HPackParser* parser,
   return deserializer.Finish();
 }
 
-BufferPair ServerFragmentFrame::Serialize(HPackCompressor* encoder) const {
+BufferPair ServerFragmentFrame::Serialize(HPackCompressor* encoder,
+                                          bool& saw_encoding_errors) const {
   CHECK_NE(stream_id, 0u);
   FrameSerializer serializer(FrameType::kFragment, stream_id);
   if (headers.get() != nullptr) {
-    encoder->EncodeRawHeaders(*headers.get(), serializer.AddHeaders());
+    saw_encoding_errors |=
+        !encoder->EncodeRawHeaders(*headers.get(), serializer.AddHeaders());
   }
   if (message.has_value()) {
     serializer.AddMessage(message.value());
   }
   if (trailers.get() != nullptr) {
-    encoder->EncodeRawHeaders(*trailers.get(), serializer.AddTrailers());
+    saw_encoding_errors |=
+        !encoder->EncodeRawHeaders(*trailers.get(), serializer.AddTrailers());
   }
   return serializer.Finish();
 }
@@ -399,7 +406,7 @@ absl::Status CancelFrame::Deserialize(HPackParser*, const FrameHeader& header,
   return deserializer.Finish();
 }
 
-BufferPair CancelFrame::Serialize(HPackCompressor*) const {
+BufferPair CancelFrame::Serialize(HPackCompressor*, bool&) const {
   CHECK_NE(stream_id, 0u);
   FrameSerializer serializer(FrameType::kCancel, stream_id);
   return serializer.Finish();

src/core/ext/transport/chaotic_good/frame.h

@@ -55,9 +55,15 @@ class FrameInterface {
                                    const FrameHeader& header,
                                    absl::BitGenRef bitsrc, Arena* arena,
                                    BufferPair buffers, FrameLimits limits) = 0;
-  virtual BufferPair Serialize(HPackCompressor* encoder) const = 0;
+  virtual BufferPair Serialize(HPackCompressor* encoder,
+                               bool& saw_encoding_errors) const = 0;
   virtual std::string ToString() const = 0;
 
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const FrameInterface& frame) {
+    sink.Append(frame.ToString());
+  }
+
  protected:
   static bool EqVal(const grpc_metadata_batch& a,
                     const grpc_metadata_batch& b) {
@@ -72,11 +78,16 @@ class FrameInterface {
   ~FrameInterface() = default;
 };
 
+inline std::ostream& operator<<(std::ostream& os, const FrameInterface& frame) {
+  return os << frame.ToString();
+}
+
 struct SettingsFrame final : public FrameInterface {
   absl::Status Deserialize(HPackParser* parser, const FrameHeader& header,
                            absl::BitGenRef bitsrc, Arena* arena,
                            BufferPair buffers, FrameLimits limits) override;
-  BufferPair Serialize(HPackCompressor* encoder) const override;
+  BufferPair Serialize(HPackCompressor* encoder,
+                       bool& saw_encoding_errors) const override;
   ClientMetadataHandle headers;
   std::string ToString() const override;
 
@@ -110,7 +121,8 @@ struct ClientFragmentFrame final : public FrameInterface {
   absl::Status Deserialize(HPackParser* parser, const FrameHeader& header,
                            absl::BitGenRef bitsrc, Arena* arena,
                            BufferPair buffers, FrameLimits limits) override;
-  BufferPair Serialize(HPackCompressor* encoder) const override;
+  BufferPair Serialize(HPackCompressor* encoder,
+                       bool& saw_encoding_errors) const override;
   std::string ToString() const override;
 
   uint32_t stream_id;
@@ -128,7 +140,8 @@ struct ServerFragmentFrame final : public FrameInterface {
   absl::Status Deserialize(HPackParser* parser, const FrameHeader& header,
                            absl::BitGenRef bitsrc, Arena* arena,
                            BufferPair buffers, FrameLimits limits) override;
-  BufferPair Serialize(HPackCompressor* encoder) const override;
+  BufferPair Serialize(HPackCompressor* encoder,
+                       bool& saw_encoding_errors) const override;
   std::string ToString() const override;
 
   uint32_t stream_id;
@@ -146,7 +159,8 @@ struct CancelFrame final : public FrameInterface {
   absl::Status Deserialize(HPackParser* parser, const FrameHeader& header,
                            absl::BitGenRef bitsrc, Arena* arena,
                            BufferPair buffers, FrameLimits limits) override;
-  BufferPair Serialize(HPackCompressor* encoder) const override;
+  BufferPair Serialize(HPackCompressor* encoder,
+                       bool& saw_encoding_errors) const override;
   std::string ToString() const override;
 
   uint32_t stream_id;

src/core/ext/transport/chaotic_good/frame_header.h

@@ -34,6 +34,19 @@ enum class FrameType : uint8_t {
   kCancel = 0x81,
 };
 
+inline std::ostream& operator<<(std::ostream& out, FrameType type) {
+  switch (type) {
+    case FrameType::kSettings:
+      return out << "Settings";
+    case FrameType::kFragment:
+      return out << "Fragment";
+    case FrameType::kCancel:
+      return out << "Cancel";
+    default:
+      return out << "Unknown[" << static_cast<int>(type) << "]";
+  }
+}
+
 struct FrameHeader {
   FrameType type = FrameType::kCancel;
   BitSet<3> flags;

src/core/ext/transport/chaotic_good/server/chaotic_good_server.cc

@@ -336,7 +336,10 @@ auto ChaoticGoodServerListener::ActiveConnection::HandshakingState::
       SettingsMetadata{absl::nullopt, self->connection_->connection_id_,
                        absl::nullopt}
           .ToMetadataBatch();
-  auto write_buffer = frame.Serialize(&self->connection_->hpack_compressor_);
+  bool saw_encoding_errors = false;
+  auto write_buffer = frame.Serialize(&self->connection_->hpack_compressor_,
+                                      saw_encoding_errors);
+  // ignore encoding errors: they will be logged separately already
   return TrySeq(
       self->connection_->endpoint_.Write(std::move(write_buffer.control)),
       WaitForDataEndpointSetup(self));
@@ -350,7 +353,10 @@ auto ChaoticGoodServerListener::ActiveConnection::HandshakingState::
       SettingsMetadata{absl::nullopt, self->connection_->connection_id_,
                        self->connection_->data_alignment_}
           .ToMetadataBatch();
-  auto write_buffer = frame.Serialize(&self->connection_->hpack_compressor_);
+  bool saw_encoding_errors = false;
+  auto write_buffer = frame.Serialize(&self->connection_->hpack_compressor_,
+                                      saw_encoding_errors);
+  // ignore encoding errors: they will be logged separately already
   return TrySeq(
       self->connection_->endpoint_.Write(std::move(write_buffer.control)),
       [self]() mutable {

src/core/ext/transport/chttp2/transport/hpack_encoder.cc

@@ -377,7 +377,8 @@ void Compressor<HttpSchemeMetadata, HttpSchemeCompressor>::EncodeWith(
       encoder->EmitIndexed(7);  // :scheme: https
       break;
     case HttpSchemeMetadata::ValueType::kInvalid:
-      Crash("invalid http scheme encoding");
+      LOG(ERROR) << "Not encoding bad http scheme";
+      encoder->NoteEncodingError();
       break;
   }
 }
@@ -434,7 +435,8 @@ void Compressor<HttpMethodMetadata, HttpMethodCompressor>::EncodeWith(
           Slice::FromStaticString(":method"), Slice::FromStaticString("PUT"));
       break;
     case HttpMethodMetadata::ValueType::kInvalid:
-      Crash("invalid http method encoding");
+      LOG(ERROR) << "Not encoding bad http method";
+      encoder->NoteEncodingError();
       break;
   }
 }

src/core/ext/transport/chttp2/transport/hpack_encoder.h

@@ -82,10 +82,14 @@ class Encoder {
                                  const Slice& slice, uint32_t* index,
                                  size_t max_compression_size);
 
+  void NoteEncodingError() { saw_encoding_errors_ = true; }
+  bool saw_encoding_errors() const { return saw_encoding_errors_; }
+
   HPackEncoderTable& hpack_table();
 
  private:
   const bool use_true_binary_metadata_;
+  bool saw_encoding_errors_ = false;
   HPackCompressor* const compressor_;
   SliceBuffer& output_;
 };
@@ -207,6 +211,7 @@ class Compressor<
       gpr_log(GPR_ERROR, "%s",
               absl::StrCat("Not encoding bad ", MetadataTrait::key(), " header")
                   .c_str());
+      encoder->NoteEncodingError();
       return;
     }
     Slice encoded(MetadataTrait::Encode(known_value));
@@ -354,19 +359,21 @@ class HPackCompressor {
   };
 
   template <typename HeaderSet>
-  void EncodeHeaders(const EncodeHeaderOptions& options,
+  bool EncodeHeaders(const EncodeHeaderOptions& options,
                      const HeaderSet& headers, grpc_slice_buffer* output) {
     SliceBuffer raw;
     hpack_encoder_detail::Encoder encoder(
         this, options.use_true_binary_metadata, raw);
     headers.Encode(&encoder);
     Frame(options, raw, output);
+    return !encoder.saw_encoding_errors();
   }
 
   template <typename HeaderSet>
-  void EncodeRawHeaders(const HeaderSet& headers, SliceBuffer& output) {
+  bool EncodeRawHeaders(const HeaderSet& headers, SliceBuffer& output) {
     hpack_encoder_detail::Encoder encoder(this, true, output);
     headers.Encode(&encoder);
+    return !encoder.saw_encoding_errors();
   }
 
  private:

test/core/transport/chaotic_good/frame_fuzzer.cc

@@ -55,7 +55,8 @@ FrameLimits FuzzerFrameLimits() { return FrameLimits{1024 * 1024 * 1024, 63}; }
 template <typename T>
 void AssertRoundTrips(const T& input, FrameType expected_frame_type) {
   HPackCompressor hpack_compressor;
-  auto serialized = input.Serialize(&hpack_compressor);
+  bool saw_encoding_errors = false;
+  auto serialized = input.Serialize(&hpack_compressor, saw_encoding_errors);
   CHECK(serialized.control.Length() >=
         24);  // Initial output buffer size is 64 byte.
   uint8_t header_bytes[24];
@@ -67,7 +68,7 @@ void AssertRoundTrips(const T& input, FrameType expected_frame_type) {
     }
     Crash("Failed to parse header");
   }
-  CHECK(header->type == expected_frame_type);
+  CHECK_EQ(header->type, expected_frame_type);
   T output;
   HPackParser hpack_parser;
   DeterministicBitGen bitgen;
@@ -75,7 +76,7 @@ void AssertRoundTrips(const T& input, FrameType expected_frame_type) {
                                   absl::BitGenRef(bitgen), GetContext<Arena>(),
                                   std::move(serialized), FuzzerFrameLimits());
   CHECK_OK(deser);
-  CHECK(output == input);
+  if (!saw_encoding_errors) CHECK_EQ(input, output);
 }
 
 template <typename T>

test/core/transport/chaotic_good/frame_fuzzer_corpus/clusterfuzz-testcase-minimized-frame_fuzzer-4558239670272000

@@ -0,0 +1 @@
+control: "\200\001\000\000\022z`:0\000\000\000\000\000\000\000\000\000:status\234@\000\000\000\000\000\000\010\2342393\\3\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\237\23777\\3\377\377\377\0037X1user-agentrol: b0\\0\000"

test/core/transport/chaotic_good/frame_test.cc

@@ -34,7 +34,8 @@ FrameLimits TestFrameLimits() { return FrameLimits{1024 * 1024 * 1024, 63}; }
 template <typename T>
 void AssertRoundTrips(const T& input, FrameType expected_frame_type) {
   HPackCompressor hpack_compressor;
-  auto serialized = input.Serialize(&hpack_compressor);
+  bool saw_encoding_errors = false;
+  auto serialized = input.Serialize(&hpack_compressor, saw_encoding_errors);
   CHECK_GE(serialized.control.Length(),
            24);  // Initial output buffer size is 64 byte.
   uint8_t header_bytes[24];
@@ -43,7 +44,7 @@ void AssertRoundTrips(const T& input, FrameType expected_frame_type) {
   if (!header.ok()) {
     Crash("Failed to parse header");
   }
-  CHECK(header->type == expected_frame_type);
+  CHECK_EQ(header->type, expected_frame_type);
   T output;
   HPackParser hpack_parser;
   absl::BitGen bitgen;
@@ -55,7 +56,7 @@ void AssertRoundTrips(const T& input, FrameType expected_frame_type) {
       output.Deserialize(&hpack_parser, header.value(), absl::BitGenRef(bitgen),
                          arena.get(), std::move(serialized), TestFrameLimits());
   CHECK_OK(deser);
-  CHECK(output == input);
+  if (!saw_encoding_errors) CHECK_EQ(output, input);
 }
 
 TEST(FrameTest, SettingsFrameRoundTrips) {