How to decrypte the data in Wireshark，OR，how to turn off the DTLS

[lokenetwork]

[chobie]

FYI: #921

As one solution, when you don't set the MediaHandler, you can directly receive RTP packets.
You can export that packet data into something that can be imported with tools like text2pcap.

[paullouisageneau]

I think @lokenetwork refers to SCTP data from data channels transported over DTLS, not RTP, which is encrypted as SRTP instead.

[chobie]

I see, I haven't looked into SCTP before, so I'll check it out next time. thanks.

[paullouisageneau]

DTLS is mandatory for WebRTC connection establishment, so there is no way to disable it from the application. You can however dump SCTP packets in rtc::impl::SctpTransport::incoming() and rtc::impl::SctpTransport::outgoing() in a format you can import in Wireshark for debugging purposes.

[voluntas]

You can add an SSLKEYLOGFILE output mechanism to libdatachannel and have Wireshark's DTLS read it.

• https://wiki.wireshark.org/TLS#using-the-pre-master-secret
• https://datatracker.ietf.org/doc/html/draft-thomson-tls-keylogfile-01

[mglettig]

You can add an SSLKEYLOGFILE output mechanism to libdatachannel and have Wireshark's DTLS read it.

• https://wiki.wireshark.org/TLS#using-the-pre-master-secret
• https://datatracker.ietf.org/doc/html/draft-thomson-tls-keylogfile-01

In which format did you enter the Pre-Shared Key in Wireshark? Something like the following?
CLIENT_RANDOM 40db03ea1f61877df4ca74ee94446e4e4acd65e448cb53da4417b81fa33cced1 af41f78680ec068300a452c4bb499bfa0776809aa6c68ade8e7a85710f2d6722e286af276e5a2bf5b9f344fcdd3ad9ca

Unfortunately it seems like I'm not able to decrypt the traffic that I previously captured.

[chobie]

I'll make it a patch for now since it's for local development. It's convenient to easily check with Wireshark.

diff --git a/src/impl/dtlstransport.cpp b/src/impl/dtlstransport.cpp
index aa518241..0199df74 100644
--- a/src/impl/dtlstransport.cpp
+++ b/src/impl/dtlstransport.cpp
@@ -752,6 +752,7 @@ DtlsTransport::DtlsTransport(shared_ptr<IceTransport> lower, certificate_ptr cer
 		SSL_CTX_set_read_ahead(mCtx, 1);
 		SSL_CTX_set_quiet_shutdown(mCtx, 0); // send the close_notify alert
 		SSL_CTX_set_info_callback(mCtx, InfoCallback);
+		SSL_CTX_set_keylog_callback(mCtx, KeyLogCallback);
 
 		SSL_CTX_set_verify(mCtx, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
 		                   CertificateCallback);
@@ -1051,6 +1052,18 @@ void DtlsTransport::InfoCallback(const SSL *ssl, int where, int ret) {
 	}
 }
 
+void DtlsTransport::KeyLogCallback(const SSL *ssl, const char* line) {
+    const char* log_file_path = std::getenv("SSLKEYLOGFILE");
+    if (log_file_path != nullptr) {
+        FILE *log_file = fopen(log_file_path, "a");
+        if (log_file != nullptr) {
+            fprintf(log_file, "%s\n", line);
+            fclose(log_file);
+        }
+    }
+}
+
+
 int DtlsTransport::BioMethodNew(BIO *bio) {
 	BIO_set_init(bio, 1);
 	BIO_set_data(bio, NULL);
diff --git a/src/impl/dtlstransport.hpp b/src/impl/dtlstransport.hpp
index d84b312e..f4011c4a 100644
--- a/src/impl/dtlstransport.hpp
+++ b/src/impl/dtlstransport.hpp
@@ -110,6 +110,7 @@ protected:
 
 	static int CertificateCallback(int preverify_ok, X509_STORE_CTX *ctx);
 	static void InfoCallback(const SSL *ssl, int where, int ret);
+	static void KeyLogCallback(const SSL *ssl, const char* line);
 
 	static int BioMethodNew(BIO *bio);
 	static int BioMethodFree(BIO *bio);

[lokenetwork]

It work, Thank you so much