Fix key frame (#394)

* fix 1st pkt decryption bug
finos · Dec 13, 2024 · b6af4db · b6af4db
1 parent 8ac44a3
commit b6af4db
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Showing 2 changed files with 30 additions and 1 deletion.
diff --git a/test/transport/SrtpTest.cpp b/test/transport/SrtpTest.cpp
@@ -555,6 +555,31 @@ TEST_F(SrtpTest, muteUntilRoc1)
     }
 }
 
+// sequence number starts close to 65535 and all packets with roc = 0 are lost.
+// First packet seen is on ROC 1 already
+TEST_F(SrtpTest, unprotect1st)
+{
+    setupDtls();
+    connect();
+
+    uint32_t roc = 0;
+
+    auto packet = memory::makeUniquePacket(_allocator, _audioPacket);
+    auto header = rtp::RtpHeader::fromPacket(*packet);
+    header->ssrc = 1;
+    header->sequenceNumber = 670;
+    header->timestamp = 160;
+    const auto audioPacketLength = packet->getLength();
+    const auto packetCopy = memory::makeUniquePacket(_allocator, *packet);
+
+    ASSERT_TRUE(_srtp1->protect(*packet));
+
+    ASSERT_TRUE(_srtp2->unprotectFirstRtp(*packet, roc));
+    EXPECT_EQ(roc, 0);
+    ASSERT_TRUE(packet->getLength() == audioPacketLength);
+    EXPECT_EQ(0, std::memcmp(packet->get(), packetCopy->get(), packetCopy->getLength()));
+}
+
 // sequence number starts close to 65535 and all packets with roc = 0 are lost.
 // First packet seen is on ROC 1 already
 TEST_F(SrtpTest, losePacketsBeforeRoc1)
@@ -573,6 +598,7 @@ TEST_F(SrtpTest, losePacketsBeforeRoc1)
         header->ssrc = 1;
         header->sequenceNumber = i & 0xFFFFu;
         header->timestamp = i * 160;
+        const auto audioPacketLength = packet->getLength();
 
         ASSERT_TRUE(_srtp1->protect(*packet));
         const uint32_t continuationPoint = 65550;
@@ -594,6 +620,7 @@ TEST_F(SrtpTest, losePacketsBeforeRoc1)
             EXPECT_EQ(roc, 1);
             unprotectedExtSeqNo = i;
             ++unprotectCount;
+            ASSERT_TRUE(packet->getLength() == audioPacketLength);
         }
     }
     EXPECT_EQ(unprotectedExtSeqNo, 65600);

diff --git a/transport/dtls/SrtpClient.cpp b/transport/dtls/SrtpClient.cpp
@@ -927,6 +927,7 @@ bool SrtpClient::unprotectFirstRtp(memory::Packet& packet, uint32_t& rolloverCou
     const auto result = srtp_unprotect(_remoteSrtp, packet.get(), &bufferLength);
     if (result == srtp_err_status_ok)
     {
+        packet.setLength(utils::checkedCast<size_t>(bufferLength));
         return true;
     }
 
@@ -936,8 +937,8 @@ bool SrtpClient::unprotectFirstRtp(memory::Packet& packet, uint32_t& rolloverCou
         assert(false);
         return false;
     }
-    const uint32_t ssrc = header->ssrc;
 
+    const uint32_t ssrc = header->ssrc;
     {
         // use remote srtp context to fake a packet with ROC=0
         alignas(sizeof(uint32_t)) uint8_t fakePacketRoc0[40]{0};
@@ -972,6 +973,7 @@ bool SrtpClient::unprotectFirstRtp(memory::Packet& packet, uint32_t& rolloverCou
 
         if (srtp_err_status_ok == srtp_unprotect(_remoteSrtp, packet.get(), &bufferLength))
         {
+            packet.setLength(utils::checkedCast<size_t>(bufferLength));
             return true;
         }
     }