Vary the parameters to WebSocketDeflateStream in fuzzer

net/websockets/websocket_deflate_stream_fuzzer.cc

Index: net/websockets/websocket_deflate_stream_fuzzer.cc
diff --git a/net/websockets/websocket_deflate_stream_fuzzer.cc b/net/websockets/websocket_deflate_stream_fuzzer.cc
index ca401d14d5f0fc91df2890edcb4fc3ac50796cd1..4f9bed3b7df51804fa8449abe99a8f72ab1f851e 100644
--- a/net/websockets/websocket_deflate_stream_fuzzer.cc
+++ b/net/websockets/websocket_deflate_stream_fuzzer.cc
@@ -11,6 +11,7 @@
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/test/fuzzed_data_provider.h"
 #include "net/base/completion_callback.h"
@@ -28,16 +29,30 @@ namespace net {
 
 namespace {
 
+// If there are less random bytes left than MIN_BYTES_TO_CREATE_A_FRAME then
+// CreateFrame() will always create an empty frame. Since the fuzzer can create
+// the same empty frame with MIN_BYTES_TO_CREATE_A_FRAME bytes of input, save it
+// from exploring a large space of ways to do the same thing.
+constexpr size_t MIN_BYTES_TO_CREATE_A_FRAME = 3;
+
+constexpr size_t BYTES_CONSUMED_BY_PARAMS = 2;
+
+// If there are exactly BYTES_CONSUMED_BY_PARAMS + MIN_BYTES_TO_CREATE_A_FRAME
+// bytes of input, then the fuzzer will test a single frame. In order to also
+// test the case with zero frames, allow one less byte than this.
+constexpr size_t MIN_USEFUL_SIZE =
+    BYTES_CONSUMED_BY_PARAMS + MIN_BYTES_TO_CREATE_A_FRAME - 1;
+
 class WebSocketFuzzedStream final : public WebSocketStream {
  public:
-  WebSocketFuzzedStream(const uint8_t* data, size_t size)
-      : fuzzed_data_provider_(data, size) {}
+  WebSocketFuzzedStream(base::FuzzedDataProvider* fuzzed_data_provider)
+      : fuzzed_data_provider_(fuzzed_data_provider) {}
 
   int ReadFrames(std::vector<std::unique_ptr<WebSocketFrame>>* frames,
                  const CompletionCallback& callback) override {
-    if (fuzzed_data_provider_.remaining_bytes() == 0)
+    if (fuzzed_data_provider_->remaining_bytes() < MIN_BYTES_TO_CREATE_A_FRAME)
       return ERR_CONNECTION_CLOSED;
-    while (fuzzed_data_provider_.remaining_bytes() > 0)
+    while (fuzzed_data_provider_->remaining_bytes() > 0)
       frames->push_back(CreateFrame());
     return OK;
   }
@@ -54,38 +69,54 @@ class WebSocketFuzzedStream final : public WebSocketStream {
  private:
   std::unique_ptr<WebSocketFrame> CreateFrame() {
     WebSocketFrameHeader::OpCode opcode =
-        fuzzed_data_provider_.ConsumeInt32InRange(
+        fuzzed_data_provider_->ConsumeUint32InRange(
             WebSocketFrameHeader::kOpCodeContinuation,
             WebSocketFrameHeader::kOpCodeControlUnused);
     auto frame = base::MakeUnique<WebSocketFrame>(opcode);
     // Bad news: ConsumeBool actually consumes a whole byte per call, so do
     // something hacky to conserve precious bits.
-    uint8_t flags = fuzzed_data_provider_.ConsumeUint8();
+    uint8_t flags = fuzzed_data_provider_->ConsumeUint8();
     frame->header.final = flags & 0x1;
     frame->header.reserved1 = (flags >> 1) & 0x1;
     frame->header.reserved2 = (flags >> 2) & 0x1;
     frame->header.reserved3 = (flags >> 3) & 0x1;
     frame->header.masked = (flags >> 4) & 0x1;
-    uint64_t payload_length = fuzzed_data_provider_.ConsumeInt32InRange(0, 64);
-    std::string payload = fuzzed_data_provider_.ConsumeBytes(payload_length);
+    uint64_t payload_length =
+        fuzzed_data_provider_->ConsumeUint32InRange(0, 64);
+    std::string payload = fuzzed_data_provider_->ConsumeBytes(payload_length);
     frame->data = new StringIOBuffer(payload);
     frame->header.payload_length = payload.size();
     return frame;
   }
 
-  base::FuzzedDataProvider fuzzed_data_provider_;
+  base::FuzzedDataProvider* fuzzed_data_provider_;
 };
 
 void WebSocketDeflateStreamFuzz(const uint8_t* data, size_t size) {
+  base::FuzzedDataProvider fuzzed_data_provider(data, size);
+  uint8_t flags = fuzzed_data_provider.ConsumeUint8();
+  bool server_no_context_takeover = flags & 0x1;
+  bool client_no_context_takeover = (flags >> 1) & 0x1;
+  uint8_t window_bits = fuzzed_data_provider.ConsumeUint8();
+  int server_max_window_bits = (window_bits & 0x7) + 8;
+  int client_max_window_bits = ((window_bits >> 3) & 0x7) + 8;
   // WebSocketDeflateStream needs to be constructed on each call because it
   // has state.
+  WebSocketExtension params("permessage-deflate");
+  if (server_no_context_takeover)
+    params.Add(WebSocketExtension::Parameter("server_no_context_takeover"));
+  if (client_no_context_takeover)
+    params.Add(WebSocketExtension::Parameter("client_no_context_takeover"));
+  params.Add(WebSocketExtension::Parameter(
+      "server_max_window_bits", base::IntToString(server_max_window_bits)));
+  params.Add(WebSocketExtension::Parameter(
+      "client_max_window_bits", base::IntToString(client_max_window_bits)));
   std::string failure_message;
   WebSocketDeflateParameters parameters;
-  parameters.Initialize(WebSocketExtension("permessage-deflate"),
-                        &failure_message);
+  DCHECK(parameters.Initialize(params, &failure_message)) << failure_message;
   WebSocketDeflateStream deflate_stream(
-      base::MakeUnique<WebSocketFuzzedStream>(data, size), parameters,
-      base::MakeUnique<WebSocketDeflatePredictorImpl>());
+      base::MakeUnique<WebSocketFuzzedStream>(&fuzzed_data_provider),
+      parameters, base::MakeUnique<WebSocketDeflatePredictorImpl>());
   std::vector<std::unique_ptr<net::WebSocketFrame>> frames;
   deflate_stream.ReadFrames(&frames, CompletionCallback());
 }
@@ -96,6 +127,8 @@ void WebSocketDeflateStreamFuzz(const uint8_t* data, size_t size) {
 
 // Entry point for LibFuzzer.
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (size < net::MIN_USEFUL_SIZE)
+    return 0;
   net::WebSocketDeflateStreamFuzz(data, size);
 
   return 0;