Add SOCKS4 and SOCKS5 fuzzers.

net/socket/socks5_client_socket_fuzzer.cc

Index: net/socket/socks5_client_socket_fuzzer.cc
diff --git a/net/socket/socks5_client_socket_fuzzer.cc b/net/socket/socks5_client_socket_fuzzer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..290db9002c959de8e8dc83f4033a8d1f597c8071
--- /dev/null
+++ b/net/socket/socks5_client_socket_fuzzer.cc
@@ -0,0 +1,46 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/socket/socks5_client_socket.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop/message_loop.h"
+#include "net/base/address_list.h"
+#include "net/base/net_errors.h"
+#include "net/base/test_completion_callback.h"
+#include "net/log/test_net_log.h"
+#include "net/socket/client_socket_handle.h"
+#include "net/socket/fuzzed_socket.h"
+
+// Fuzzer for Socks5ClientSocket.  Only covers the SOCKS5 greeet and
+// handshake.
+//
+// |data| is used to create a FuzzedSocket to fuzz reads and writes, see that
+// class for details.
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  // Needed for thread checks and waits.
+  base::MessageLoopForIO message_loop;
+
+  // Use a test NetLog, to exercise logging code.
+  net::BoundTestNetLog bound_test_net_log;
+
+  net::TestCompletionCallback callback;
+  scoped_ptr<net::FuzzedSocket> fuzzed_socket(
+      new net::FuzzedSocket(data, size, bound_test_net_log.bound()));
+  CHECK_EQ(net::OK, fuzzed_socket->Connect(callback.callback()));
+
+  scoped_ptr<net::ClientSocketHandle> socket_handle(
+      new net::ClientSocketHandle());
+  socket_handle->SetSocket(std::move(fuzzed_socket));
+
+  net::HostResolver::RequestInfo request_info(net::HostPortPair("foo", 80));

[eroman, 2016/04/14 17:56:28]

Fuzzing different host portpairs would be a useful extension.

[mmenke, 2016/04/14 19:01:51]

Makes sense, but let's skip that, for now.  I'm not sure what sort of host names
we should allow - 0-length ones, characters that aren't normally allowed in host
names, etc.

[eroman, 2016/04/14 19:32:39]

In theory the hostname comes from a normalized GURL so should be valid. moreover
shouldn't make a difference to the socks (client) code. The only interesting
data would be a hostname over 255 bytes long, since that will trigger a
different codepath.

Yeah fine to not worry about this.

+  net::SOCKS5ClientSocket socket(std::move(socket_handle), request_info);
+  int result = socket.Connect(callback.callback());
+  callback.GetResult(result);
+  return 0;
+}