[Cast MRP] Changed IsCastInternalNamespace to match legacy impl.

Bug: 1129217
Change-Id: I683aeee86f06a157255eae0c9db3948509ebcbf6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2438749
Commit-Queue: John Williams <jrw@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814806}

components/cast_channel/cast_message_handler.cc

@@ -277,7 +277,7 @@ Result CastMessageHandler::SendCastMessage(int channel_id,
 
 Result CastMessageHandler::SendAppMessage(int channel_id,
                                           const CastMessage& message) {
-  DCHECK(!IsCastInternalNamespace(message.namespace_()))
+  DCHECK(!IsCastReservedNamespace(message.namespace_()))
       << ": unexpected app message namespace: " << message.namespace_();
   if (message.ByteSizeLong() > kMaxCastMessagePayload) {
     return Result::kFailed;
@@ -354,7 +354,7 @@ void CastMessageHandler::OnMessage(const CastSocket& socket,
   // separate data type is pretty questionable, because it causes duplicated
   // code paths in the downstream logic (manifested as separate OnAppMessage and
   // OnInternalMessage methods).
-  if (IsCastInternalNamespace(message.namespace_())) {
+  if (IsCastReservedNamespace(message.namespace_())) {
     if (message.payload_type() ==
         cast::channel::CastMessage_PayloadType_STRING) {
       VLOG(1) << __func__ << ": channel_id: " << socket.id()

components/cast_channel/cast_message_util.cc

@@ -8,6 +8,7 @@
 
 #include "base/json/json_writer.h"
 #include "base/logging.h"
+#include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
@@ -18,6 +19,7 @@
 using base::Value;
 using cast_util::EnumToString;
 using cast_util::StringToEnum;
+
 namespace cast_util {
 
 using ::cast::channel::AuthChallenge;
@@ -99,6 +101,24 @@ namespace cast_channel {
 
 namespace {
 
+constexpr base::StringPiece kCastReservedNamespacePrefix =
+    "urn:x-cast:com.google.cast.";
+
+constexpr const char* kReservedNamespaces[] = {
+    kAuthNamespace,
+    kHeartbeatNamespace,
+    kConnectionNamespace,
+    kReceiverNamespace,
+    kBroadcastNamespace,
+    kMediaNamespace,
+
+    // mirroring::mojom::kRemotingNamespace
+    "urn:x-cast:com.google.cast.remoting",
+
+    // mirroring::mojom::kWebRtcNamespace
+    "urn:x-cast:com.google.cast.webrtc",
+};
+
 // The value used for "sdkType" in a virtual connect request. Historically, this
 // value is used in the Media Router extension, but here it is reused in Chrome.
 constexpr int kVirtualConnectSdkType = 2;
@@ -209,11 +229,31 @@ bool IsCastMessageValid(const CastMessage& message_proto) {
           message_proto.has_payload_binary());
 }
 
-bool IsCastInternalNamespace(const std::string& message_namespace) {
-  // Note: any namespace with the prefix is assumed to be reserved for internal
-  // messages.
-  return base::StartsWith(message_namespace, kCastInternalNamespacePrefix,
-                          base::CompareCase::SENSITIVE);
+bool IsCastReservedNamespace(base::StringPiece message_namespace) {
+  // Note: Any namespace with the prefix is theoretically reserved for internal
+  // messages, but there is at least one namespace in widespread use that uses
+  // the "reserved" prefix for app-level messages, so after matching the main
+  // prefix, we look for longer prefixes that really need to be reserved.
+  if (!base::StartsWith(message_namespace, kCastReservedNamespacePrefix))
+    return false;
+
+  const auto prefix_length = kCastReservedNamespacePrefix.length();
+  for (base::StringPiece reserved_namespace : kReservedNamespaces) {
+    DCHECK(base::StartsWith(reserved_namespace, kCastReservedNamespacePrefix));
+    // This comparison skips the first |prefix_length| characters
+    // because we already know they match.
+    if (base::StartsWith(message_namespace.substr(prefix_length),
+                         reserved_namespace.substr(prefix_length)) &&
+        // This condition allows |reserved_namespace| to be equal
+        // |message_namespace| or be a prefix of it, but if it's a
+        // prefix, it must be followed by a dot.  The subscript is
+        // never out of bounds because |message_namespace| must be
+        // at least as long as |reserved_namespace|.
+        (message_namespace.length() == reserved_namespace.length() ||
+         message_namespace[reserved_namespace.length()] == '.'))
+      return true;
+  }
+  return false;
 }
 
 CastMessageType ParseMessageTypeFromPayload(const base::Value& payload) {

components/cast_channel/cast_message_util.h

@@ -17,8 +17,6 @@ using ::cast::channel::CastMessage;
 using ::cast::channel::DeviceAuthMessage;
 
 // Reserved message namespaces for internal messages.
-static constexpr char kCastInternalNamespacePrefix[] =
-    "urn:x-cast:com.google.cast.";
 static constexpr char kAuthNamespace[] =
     "urn:x-cast:com.google.cast.tp.deviceauth";
 static constexpr char kHeartbeatNamespace[] =
@@ -164,7 +162,7 @@ bool IsCastMessageValid(const CastMessage& message_proto);
 
 // Returns true if |message_namespace| is a namespace reserved for internal
 // messages.
-bool IsCastInternalNamespace(const std::string& message_namespace);
+bool IsCastReservedNamespace(base::StringPiece message_namespace);
 
 // Returns the value in the "type" field or |kOther| if the field is not found.
 // The result is only valid if |payload| is a Cast application protocol message.

components/cast_channel/cast_message_util_fuzzer.cc

@@ -106,7 +106,7 @@ DEFINE_PROTO_FUZZER(const CastMessageUtilInputs& input_union) {
       break;
     }
     case CastMessageUtilInputs::kStringInput: {
-      IsCastInternalNamespace(input_union.string_input());
+      IsCastReservedNamespace(input_union.string_input());
       break;
     }
     case CastMessageUtilInputs::kCastMessage: {

components/cast_channel/cast_message_util_unittest.cc

@@ -15,12 +15,21 @@ using base::test::ParseJson;
 
 namespace cast_channel {
 
-TEST(CastMessageUtilTest, IsCastInternalNamespace) {
-  EXPECT_TRUE(IsCastInternalNamespace("urn:x-cast:com.google.cast.receiver"));
-  EXPECT_FALSE(IsCastInternalNamespace("urn:x-cast:com.google.youtube"));
-  EXPECT_FALSE(IsCastInternalNamespace("urn:x-cast:com.foo"));
-  EXPECT_FALSE(IsCastInternalNamespace("foo"));
-  EXPECT_FALSE(IsCastInternalNamespace(""));
+TEST(CastMessageUtilTest, IsCastReservedNamespace) {
+  EXPECT_TRUE(
+      IsCastReservedNamespace("urn:x-cast:com.google.cast.receiver.xyzzy"));
+  EXPECT_TRUE(IsCastReservedNamespace("urn:x-cast:com.google.cast.receiver"));
+  EXPECT_FALSE(IsCastReservedNamespace("urn:x-cast:com.google.cast"));
+  EXPECT_FALSE(IsCastReservedNamespace("urn:x-cast:com.google.cast."));
+  EXPECT_FALSE(
+      IsCastReservedNamespace("urn:x-cast:com.google.cast.foo.receiver"));
+  EXPECT_FALSE(
+      IsCastReservedNamespace("urn:x-cast:com.google.cast.receiverfoo"));
+  EXPECT_FALSE(IsCastReservedNamespace("urn:x-cast:com.google.cast.xyzzy"));
+  EXPECT_FALSE(IsCastReservedNamespace("urn:x-cast:com.google.youtube"));
+  EXPECT_FALSE(IsCastReservedNamespace("urn:x-cast:com.foo"));
+  EXPECT_FALSE(IsCastReservedNamespace("foo"));
+  EXPECT_FALSE(IsCastReservedNamespace(""));
 }
 
 TEST(CastMessageUtilTest, CastMessageType) {

components/cast_channel/proto/fuzzer_inputs.proto

@@ -139,7 +139,7 @@ message CastMessageUtilInputs {
 
   message GetLaunchSessionResponseInput { required JunkValue payload = 1; }
 
-  message IsCastInternalNamespaceInput {
+  message IsCastReservedNamespaceInput {
     required string message_namespace = 1;
   }