From e6cb2a22f744801e9adb43fa4236d7e90132ebb3 Mon Sep 17 00:00:00 2001
From: Dmytro Bogovych <dmytro.bogovych@gmail.com>
Date: Sun, 24 Aug 2025 14:01:43 +0300
Subject: [PATCH] - improve SRTP decoder API

---
 src/engine/media/MT_AudioStream.cpp | 10 +++++++---
 src/engine/media/MT_AudioStream.h   |  3 ++-
 src/engine/media/MT_SrtpHelper.cpp  | 18 +++++++-----------
 src/engine/media/MT_SrtpHelper.h    |  4 ++--
 4 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/src/engine/media/MT_AudioStream.cpp b/src/engine/media/MT_AudioStream.cpp
index 8f5a2cda..707ab922 100644
--- a/src/engine/media/MT_AudioStream.cpp
+++ b/src/engine/media/MT_AudioStream.cpp
@@ -306,18 +306,22 @@ void AudioStream::dataArrived(PDatagramSocket s, const void* buffer, int length,
     int receiveLength = length;
     memcpy(mReceiveBuffer, buffer, length);
 
-    bool srtpResult;
     if (mSrtpSession.active())
     {
+        bool srtpResult;
+        size_t srcLength = length; size_t dstLength = sizeof mSrtpDecodeBuffer;
         if (RtpHelper::isRtp(mReceiveBuffer, receiveLength))
-            srtpResult = mSrtpSession.unprotectRtp(mReceiveBuffer, &receiveLength);
+            srtpResult = mSrtpSession.unprotectRtp(mReceiveBuffer, srcLength, mSrtpDecodeBuffer, &dstLength);
         else
-            srtpResult = mSrtpSession.unprotectRtcp(mReceiveBuffer, &receiveLength);
+            srtpResult = mSrtpSession.unprotectRtcp(mReceiveBuffer, srcLength, mSrtpDecodeBuffer, &dstLength);
         if (!srtpResult)
         {
             ICELogError(<<"Cannot decrypt SRTP packet.");
             return;
         }
+
+        memcpy(mReceiveBuffer, mSrtpDecodeBuffer, dstLength);
+        receiveLength = dstLength;
     }
 
     switch (source.family())
diff --git a/src/engine/media/MT_AudioStream.h b/src/engine/media/MT_AudioStream.h
index fbf35ba8..df810d8e 100644
--- a/src/engine/media/MT_AudioStream.h
+++ b/src/engine/media/MT_AudioStream.h
@@ -87,7 +87,8 @@ protected:
     mCaptureResampler32,
     mCaptureResampler48;
     DtmfContext mDtmfContext;
-    char mReceiveBuffer[MAX_VALID_UDPPACKET_SIZE];
+    char mReceiveBuffer[MAX_VALID_UDPPACKET_SIZE],
+         mSrtpDecodeBuffer[MAX_VALID_UDPPACKET_SIZE];
 
     struct
     {
diff --git a/src/engine/media/MT_SrtpHelper.cpp b/src/engine/media/MT_SrtpHelper.cpp
index 6daf298b..9abb58a3 100644
--- a/src/engine/media/MT_SrtpHelper.cpp
+++ b/src/engine/media/MT_SrtpHelper.cpp
@@ -209,36 +209,32 @@ bool SrtpSession::protectRtcp(void* buffer, int* length)
         return false;
 }
 
-bool SrtpSession::unprotectRtp(void* buffer, int* length)
+bool SrtpSession::unprotectRtp(const void* src, size_t srcLength, void* dst, size_t* dstLength)
 {
     //addSsrc(RtpHelper::findSsrc(buffer, *length), sdIncoming);
 
     Lock l(mGuard);
     if (mInboundSession)
     {
-        size_t rtp_len = MAX_VALID_UDPPACKET_SIZE;
-        auto code =  srtp_unprotect(mInboundSession,
-                                    (const uint8_t*)buffer, (size_t)*length,
-                                    (uint8_t*)buffer, &rtp_len);
-        *length = rtp_len;
+        auto code = srtp_unprotect(mInboundSession,
+                                   (const uint8_t*)src, srcLength,
+                                   (uint8_t*)dst, dstLength);
         return code == 0;
     }
     else
         return false;
 }
 
-bool SrtpSession::unprotectRtcp(void* buffer, int* length)
+bool SrtpSession::unprotectRtcp(const void* src, size_t srcLength, void* dst, size_t* dstLength)
 {
     //addSsrc(RtpHelper::findSsrc(buffer, *length), sdIncoming);
 
     Lock l(mGuard);
     if (mInboundSession)
     {
-        size_t rtp_len = MAX_VALID_UDPPACKET_SIZE;
         auto code = srtp_unprotect_rtcp(mInboundSession,
-                                        (const uint8_t*)buffer, (size_t)*length,
-                                        (uint8_t*)buffer, (size_t*)rtp_len);
-        *length = rtp_len;
+                                        (const uint8_t*)src, srcLength,
+                                        (uint8_t*)dst, dstLength);
         return code == 0;
     }
     else
diff --git a/src/engine/media/MT_SrtpHelper.h b/src/engine/media/MT_SrtpHelper.h
index 4d0cd262..aa3304e6 100644
--- a/src/engine/media/MT_SrtpHelper.h
+++ b/src/engine/media/MT_SrtpHelper.h
@@ -48,8 +48,8 @@ public:
   /* bufferPtr is RTP packet data i.e. header + payload. Buffer must be big enough to hold encrypted data. */
   bool protectRtp(void* buffer, int* length);
   bool protectRtcp(void* buffer, int* length);
-  bool unprotectRtp(void* buffer, int* length);
-  bool unprotectRtcp(void* buffer, int* length);
+  bool unprotectRtp(const void* src, size_t srcLength, void* dst, size_t* dstLength);
+  bool unprotectRtcp(const void* src, size_t srcLength, void* dst, size_t* dstLength);
   
 
   static void initSrtp();