3 files changed, 75 insertions, 32 deletions

diff --git a/chromium/third_party/webrtc/pc/mediasession.cc b/chromium/third_party/webrtc/pc/mediasession.cc
index 8079ae140cb..835f76d1cf0 100644
--- a/chromium/third_party/webrtc/pc/mediasession.cc
+++ b/chromium/third_party/webrtc/pc/mediasession.cc
@@ -1860,7 +1860,7 @@ bool MediaSessionDescriptionFactory::AddAudioContentForOffer(
   AudioCodecs filtered_codecs;
   // Add the codecs from current content if exists.
   if (current_content) {
-    RTC_DCHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_AUDIO));
+    RTC_CHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_AUDIO));
     const AudioContentDescription* acd =
         static_cast<const AudioContentDescription*>(
             current_content->description);
@@ -1938,7 +1938,7 @@ bool MediaSessionDescriptionFactory::AddVideoContentForOffer(
   VideoCodecs filtered_codecs;
   // Add the codecs from current content if exists.
   if (current_content) {
-    RTC_DCHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_VIDEO));
+    RTC_CHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_VIDEO));
     const VideoContentDescription* vcd =
         static_cast<const VideoContentDescription*>(
             current_content->description);
@@ -2002,6 +2002,7 @@ bool MediaSessionDescriptionFactory::AddDataContentForOffer(
   // If the DataChannel type is not specified, use the DataChannel type in
   // the current description.
   if (session_options.data_channel_type == DCT_NONE && current_content) {
+    RTC_CHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_DATA));
     is_sctp = (static_cast<const DataContentDescription*>(
                    current_content->description)
                    ->protocol() == kMediaProtocolSctp);
@@ -2077,6 +2078,7 @@ bool MediaSessionDescriptionFactory::AddAudioContentForAnswer(
     const AudioCodecs& audio_codecs,
     StreamParamsVec* current_streams,
     SessionDescription* answer) const {
+  RTC_CHECK(IsMediaContentOfType(offer_content, MEDIA_TYPE_AUDIO));
   const AudioContentDescription* offer_audio_description =
       static_cast<const AudioContentDescription*>(offer_content->description);
 
@@ -2101,7 +2103,7 @@ bool MediaSessionDescriptionFactory::AddAudioContentForAnswer(
   AudioCodecs filtered_codecs;
   // Add the codecs from current content if exists.
   if (current_content) {
-    RTC_DCHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_AUDIO));
+    RTC_CHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_AUDIO));
     const AudioContentDescription* acd =
         static_cast<const AudioContentDescription*>(
             current_content->description);
@@ -2170,6 +2172,7 @@ bool MediaSessionDescriptionFactory::AddVideoContentForAnswer(
     const VideoCodecs& video_codecs,
     StreamParamsVec* current_streams,
     SessionDescription* answer) const {
+  RTC_CHECK(IsMediaContentOfType(offer_content, MEDIA_TYPE_VIDEO));
   const VideoContentDescription* offer_video_description =
       static_cast<const VideoContentDescription*>(offer_content->description);
 
@@ -2184,7 +2187,7 @@ bool MediaSessionDescriptionFactory::AddVideoContentForAnswer(
   VideoCodecs filtered_codecs;
   // Add the codecs from current content if exists.
   if (current_content) {
-    RTC_DCHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_VIDEO));
+    RTC_CHECK(IsMediaContentOfType(current_content, MEDIA_TYPE_VIDEO));
     const VideoContentDescription* vcd =
         static_cast<const VideoContentDescription*>(
             current_content->description);
@@ -2270,19 +2273,18 @@ bool MediaSessionDescriptionFactory::AddDataContentForAnswer(
       data_transport->secure() ? cricket::SEC_DISABLED : secure();
   bool bundle_enabled = offer_description->HasGroup(GROUP_TYPE_BUNDLE) &&
                         session_options.bundle_enabled;
+  RTC_CHECK(IsMediaContentOfType(offer_content, MEDIA_TYPE_DATA));
+  const DataContentDescription* offer_data_description =
+      static_cast<const DataContentDescription*>(offer_content->description);
   if (!CreateMediaContentAnswer(
-          static_cast<const DataContentDescription*>(
-              offer_content->description),
-          media_description_options, session_options, data_codecs, sdes_policy,
-          GetCryptos(current_content), RtpHeaderExtensions(),
-          enable_encrypted_rtp_header_extensions_, current_streams,
-          bundle_enabled, data_answer.get())) {
+          offer_data_description, media_description_options, session_options,
+          data_codecs, sdes_policy, GetCryptos(current_content),
+          RtpHeaderExtensions(), enable_encrypted_rtp_header_extensions_,
+          current_streams, bundle_enabled, data_answer.get())) {
     return false;  // Fails the session setup.
   }
 
   // Respond with sctpmap if the offer uses sctpmap.
-  const DataContentDescription* offer_data_description =
-      static_cast<const DataContentDescription*>(offer_content->description);
   bool offer_uses_sctpmap = offer_data_description->use_sctpmap();
   data_answer->set_use_sctpmap(offer_uses_sctpmap);
 
diff --git a/chromium/third_party/webrtc/pc/peerconnectioninterface_unittest.cc b/chromium/third_party/webrtc/pc/peerconnectioninterface_unittest.cc
index cc063b4f746..ac6c8b95667 100644
--- a/chromium/third_party/webrtc/pc/peerconnectioninterface_unittest.cc
+++ b/chromium/third_party/webrtc/pc/peerconnectioninterface_unittest.cc
@@ -3710,7 +3710,7 @@ TEST_F(PeerConnectionInterfaceTest, CreateAnswerWithoutRemoteDescription) {
   EXPECT_TRUE(DoCreateAnswer(&answer, nullptr));
 }
 
-// Test that an error is returned if a description is applied that doesn't
+// Tests that an error is returned if a description is applied that doesn't
 // respect the order of existing media sections.
 TEST_F(PeerConnectionInterfaceTest,
        MediaSectionOrderEnforcedForSubsequentOffers) {
@@ -3743,6 +3743,37 @@ TEST_F(PeerConnectionInterfaceTest,
   EXPECT_FALSE(DoSetLocalDescription(std::move(offer)));
 }
 
+// Tests that an error is returned if a description is applied that has fewer
+// media sections than the existing description.
+TEST_F(PeerConnectionInterfaceTest,
+       MediaSectionCountEnforcedForSubsequentOffer) {
+  CreatePeerConnection();
+  FakeConstraints constraints;
+  constraints.SetMandatoryReceiveAudio(true);
+  constraints.SetMandatoryReceiveVideo(true);
+  std::unique_ptr<SessionDescriptionInterface> offer;
+  ASSERT_TRUE(DoCreateOffer(&offer, &constraints));
+  EXPECT_TRUE(DoSetRemoteDescription(std::move(offer)));
+
+  // A remote offer with fewer media sections should be rejected.
+  ASSERT_TRUE(DoCreateOffer(&offer, &constraints));
+  offer->description()->contents().pop_back();
+  offer->description()->contents().pop_back();
+  ASSERT_TRUE(offer->description()->contents().empty());
+  EXPECT_FALSE(DoSetRemoteDescription(std::move(offer)));
+
+  std::unique_ptr<SessionDescriptionInterface> answer;
+  ASSERT_TRUE(DoCreateAnswer(&answer, nullptr));
+  EXPECT_TRUE(DoSetLocalDescription(std::move(answer)));
+
+  // A subsequent local offer with fewer media sections should be rejected.
+  ASSERT_TRUE(DoCreateOffer(&offer, &constraints));
+  offer->description()->contents().pop_back();
+  offer->description()->contents().pop_back();
+  ASSERT_TRUE(offer->description()->contents().empty());
+  EXPECT_FALSE(DoSetLocalDescription(std::move(offer)));
+}
+
 class PeerConnectionMediaConfigTest : public testing::Test {
  protected:
   void SetUp() override {
diff --git a/chromium/third_party/webrtc/pc/webrtcsession.cc b/chromium/third_party/webrtc/pc/webrtcsession.cc
index f556204c6c9..55d029608cb 100644
--- a/chromium/third_party/webrtc/pc/webrtcsession.cc
+++ b/chromium/third_party/webrtc/pc/webrtcsession.cc
@@ -140,25 +140,30 @@ IceCandidatePairType GetIceCandidatePairCounter(
   return kIceCandidatePairMax;
 }
 
-// Verify that the order of media sections in |desc1| matches |desc2|. The
-// number of m= sections could be different.
-static bool MediaSectionsInSameOrder(const SessionDescription* desc1,
-                                     const SessionDescription* desc2) {
-  if (!desc1 || !desc2) {
+// Verify that the order of media sections in |new_desc| matches
+// |existing_desc|. The number of m= sections in |new_desc| should be no less
+// than |existing_desc|.
+static bool MediaSectionsInSameOrder(const SessionDescription* existing_desc,
+                                     const SessionDescription* new_desc) {
+  if (!existing_desc || !new_desc) {
+    return false;
+  }
+
+  if (existing_desc->contents().size() > new_desc->contents().size()) {
     return false;
   }
-  for (size_t i = 0;
-       i < desc1->contents().size() && i < desc2->contents().size(); ++i) {
-    if ((desc2->contents()[i].name) != desc1->contents()[i].name) {
+
+  for (size_t i = 0; i < existing_desc->contents().size(); ++i) {
+    if (new_desc->contents()[i].name != existing_desc->contents()[i].name) {
       return false;
     }
-    const MediaContentDescription* desc2_mdesc =
+    const MediaContentDescription* new_desc_mdesc =
         static_cast<const MediaContentDescription*>(
-            desc2->contents()[i].description);
-    const MediaContentDescription* desc1_mdesc =
+            new_desc->contents()[i].description);
+    const MediaContentDescription* existing_desc_mdesc =
         static_cast<const MediaContentDescription*>(
-            desc1->contents()[i].description);
-    if (desc2_mdesc->type() != desc1_mdesc->type()) {
+            existing_desc->contents()[i].description);
+    if (new_desc_mdesc->type() != existing_desc_mdesc->type()) {
       return false;
     }
   }
@@ -2165,16 +2170,21 @@ bool WebRtcSession::ValidateSessionDescription(
     const cricket::SessionDescription* offer_desc =
         (source == cricket::CS_LOCAL) ? remote_description()->description()
                                       : local_description()->description();
-    if (!MediaSectionsHaveSameCount(sdesc->description(), offer_desc) ||
-        !MediaSectionsInSameOrder(sdesc->description(), offer_desc)) {
+    if (!MediaSectionsHaveSameCount(offer_desc, sdesc->description()) ||
+        !MediaSectionsInSameOrder(offer_desc, sdesc->description())) {
       return BadAnswerSdp(source, kMlineMismatchInAnswer, err_desc);
     }
   } else {
-    // The re-offers should respect the order of m= sections in current local
+    const cricket::SessionDescription* current_desc = nullptr;
+    if (source == cricket::CS_LOCAL && local_description()) {
+      current_desc = local_description()->description();
+    } else if (source == cricket::CS_REMOTE && remote_description()) {
+      current_desc = remote_description()->description();
+    }
+    // The re-offers should respect the order of m= sections in current
     // description. See RFC3264 Section 8 paragraph 4 for more details.
-    if (local_description() &&
-        !MediaSectionsInSameOrder(sdesc->description(),
-                                  local_description()->description())) {
+    if (current_desc &&
+        !MediaSectionsInSameOrder(current_desc, sdesc->description())) {
       return BadOfferSdp(source, kMlineMismatchInSubsequentOffer, err_desc);
     }
   }