net: add a test to ensure that our TLS handshake doesn't get too large.

net/url_request/url_request_unittest.cc

Index: net/url_request/url_request_unittest.cc
diff --git a/net/url_request/url_request_unittest.cc b/net/url_request/url_request_unittest.cc
index 64f5ac1d477564c919086b72b468cc1a1c22242f..0ce397e67b39494d4d419ba887ed16e2ab9233e9 100644
--- a/net/url_request/url_request_unittest.cc
+++ b/net/url_request/url_request_unittest.cc
@@ -5405,6 +5405,48 @@ TEST_F(HTTPSRequestTest, SSLSessionCacheShardTest) {
   }
 }
 
+// Check that our ClientHello doesn't get too large because that's known to
+// cause issues.
+TEST_F(HTTPSRequestTest, ClientHelloTest) {
+  SpawnedTestServer::SSLOptions ssl_options;
+  SpawnedTestServer test_server(
+      SpawnedTestServer::TYPE_HTTPS,
+      ssl_options,
+      base::FilePath(FILE_PATH_LITERAL("net/data/ssl")));
+  ASSERT_TRUE(test_server.Start());
+
+  // NPN/ALPN strings need to be enabled in order for the size of the handshake
+  // to be accurate as ALPN includes these strings in the handshake. This will
+  // be reset by NetTestSuite.
+  HttpStreamFactory::EnableNpnSpdy4a2();
+
+  TestDelegate d;
+  URLRequest r(
+      test_server.GetURL("client-hello-length"), &d, &default_context_);
+
+  r.Start();
+  EXPECT_TRUE(r.is_pending());
+
+  base::MessageLoop::current()->Run();
+
+  // The response will be a single, base 10 number which is the number of bytes
+  // in the ClientHello, including the handshake message type byte and 3 byte
+  // length at the beginning.
+
+  EXPECT_EQ(1, d.response_started_count());
+  unsigned client_hello_length;
+  ASSERT_TRUE(base::StringToUint(d.data_received(), &client_hello_length));
+  // We add the overhead of an SNI extension because the request is sent to
+  // 127.0.0.1 and so doesn't have one otherwise.
+  const unsigned sni_overhead = 2 /* extension type */ +
+                                2 /* extension length */ +
+                                4 /* lengths in the server_name extension */ +
+                                strlen("www.wellsfargo.com");
+  static const unsigned session_id_overhead = 32;
+
+  EXPECT_GT(256u, client_hello_length + sni_overhead + session_id_overhead);
+}
+
 class TestSSLConfigService : public SSLConfigService {
  public:
   TestSSLConfigService(bool ev_enabled,