Fix the OpenSSL implementation of ExportKeyingMaterial.

The empty context and not using a context are different.

BUG=none

Review URL: https://codereview.chromium.org/1053233003

Cr-Commit-Position: refs/heads/master@{#323958}

net/socket/ssl_client_socket_openssl.cc

@@ -422,8 +422,8 @@ int SSLClientSocketOpenSSL::ExportKeyingMaterial(
 
   int rv = SSL_export_keying_material(
       ssl_, out, outlen, label.data(), label.size(),
-      reinterpret_cast<const unsigned char*>(context.data()),
-      context.length(), context.length() > 0);
+      reinterpret_cast<const unsigned char*>(context.data()), context.length(),
+      has_context ? 1 : 0);
 
   if (rv != 1) {
     int ssl_error = SSL_get_error(ssl_, rv);

net/socket/ssl_client_socket_unittest.cc

@@ -2331,18 +2331,32 @@ TEST_F(SSLClientSocketTest, ExportKeyingMaterial) {
 
   const int kKeyingMaterialSize = 32;
   const char kKeyingLabel1[] = "client-socket-test-1";
-  const char kKeyingContext[] = "";
+  const char kKeyingContext1[] = "";
   unsigned char client_out1[kKeyingMaterialSize];
   memset(client_out1, 0, sizeof(client_out1));
-  rv = sock->ExportKeyingMaterial(
-      kKeyingLabel1, false, kKeyingContext, client_out1, sizeof(client_out1));
+  rv = sock->ExportKeyingMaterial(kKeyingLabel1, false, kKeyingContext1,
+                                  client_out1, sizeof(client_out1));
   EXPECT_EQ(rv, OK);
 
   const char kKeyingLabel2[] = "client-socket-test-2";
   unsigned char client_out2[kKeyingMaterialSize];
   memset(client_out2, 0, sizeof(client_out2));
-  rv = sock->ExportKeyingMaterial(
-      kKeyingLabel2, false, kKeyingContext, client_out2, sizeof(client_out2));
+  rv = sock->ExportKeyingMaterial(kKeyingLabel2, false, kKeyingContext1,
+                                  client_out2, sizeof(client_out2));
+  EXPECT_EQ(rv, OK);
+  EXPECT_NE(memcmp(client_out1, client_out2, kKeyingMaterialSize), 0);
+
+  const char kKeyingContext2[] = "context";
+  rv = sock->ExportKeyingMaterial(kKeyingLabel1, true, kKeyingContext2,
+                                  client_out2, sizeof(client_out2));
+  EXPECT_EQ(rv, OK);
+  EXPECT_NE(memcmp(client_out1, client_out2, kKeyingMaterialSize), 0);
+
+  // Using an empty context should give different key material from not using a
+  // context at all.
+  memset(client_out2, 0, sizeof(client_out2));
+  rv = sock->ExportKeyingMaterial(kKeyingLabel1, true, kKeyingContext1,
+                                  client_out2, sizeof(client_out2));
   EXPECT_EQ(rv, OK);
   EXPECT_NE(memcmp(client_out1, client_out2, kKeyingMaterialSize), 0);
 }