From 68cdc652fb37d49a73a9a9bc1bfa14aed16f2610 Mon Sep 17 00:00:00 2001
From: topworldcoder <63830798+topworldcoder@users.noreply.github.com>
Date: Mon, 18 Nov 2024 20:44:03 +0800
Subject: [PATCH] Update the usage of offerer

In webrtc, offerer usually acts the role of 'AGENT_MODE_CONTROLLING', and set 'a=setup:active' in sdp, and acts the role of 'DTLS_SRTP_ROLE_CLIENT'.
---
 src/agent.c                  |  2 +-
 src/dtls_srtp.c              | 59 ++++++++++++++++--------------------
 src/dtls_srtp.h              |  8 ++---
 src/peer_connection.c        | 55 +++++++++++++++++++--------------
 src/peer_connection.h        |  2 ++
 tests/test_peer_connection.c |  4 +--
 6 files changed, 68 insertions(+), 62 deletions(-)

diff --git a/src/agent.c b/src/agent.c
index c0942ac..525301f 100644
--- a/src/agent.c
+++ b/src/agent.c
@@ -321,7 +321,7 @@ static void agent_create_binding_response(Agent* agent, StunMessage* msg, Addres
 }
 
 static void agent_create_binding_request(Agent* agent, StunMessage* msg) {
-  uint64_t tie_breaker = 0;  // always be controlled
+  uint64_t tie_breaker = 1;  // always be controlled
   // send binding request
   stun_msg_create(msg, STUN_CLASS_REQUEST | STUN_METHOD_BINDING);
   char username[584];
diff --git a/src/dtls_srtp.c b/src/dtls_srtp.c
index a233fe8..622a95e 100644
--- a/src/dtls_srtp.c
+++ b/src/dtls_srtp.c
@@ -186,12 +186,6 @@ int dtls_srtp_init(DtlsSrtp* dtls_srtp, DtlsSrtpRole role, void* user_data) {
                                 MBEDTLS_SSL_TRANSPORT_DATAGRAM,
                                 MBEDTLS_SSL_PRESET_DEFAULT);
 
-    mbedtls_ssl_cookie_init(&dtls_srtp->cookie_ctx);
-
-    mbedtls_ssl_cookie_setup(&dtls_srtp->cookie_ctx, mbedtls_ctr_drbg_random, &dtls_srtp->ctr_drbg);
-
-    mbedtls_ssl_conf_dtls_cookies(&dtls_srtp->conf, mbedtls_ssl_cookie_write, mbedtls_ssl_cookie_check, &dtls_srtp->cookie_ctx);
-
   } else {
     mbedtls_ssl_config_defaults(&dtls_srtp->conf,
                                 MBEDTLS_SSL_IS_CLIENT,
@@ -199,6 +193,12 @@ int dtls_srtp_init(DtlsSrtp* dtls_srtp, DtlsSrtpRole role, void* user_data) {
                                 MBEDTLS_SSL_PRESET_DEFAULT);
   }
 
+  mbedtls_ssl_cookie_init(&dtls_srtp->cookie_ctx);
+
+  mbedtls_ssl_cookie_setup(&dtls_srtp->cookie_ctx, mbedtls_ctr_drbg_random, &dtls_srtp->ctr_drbg);
+
+  mbedtls_ssl_conf_dtls_cookies(&dtls_srtp->conf, mbedtls_ssl_cookie_write, mbedtls_ssl_cookie_check, &dtls_srtp->cookie_ctx);
+
   dtls_srtp_x509_digest(&dtls_srtp->cert, dtls_srtp->local_fingerprint);
 
   LOGD("local fingerprint: %s", dtls_srtp->local_fingerprint);
@@ -223,9 +223,7 @@ void dtls_srtp_deinit(DtlsSrtp* dtls_srtp) {
   mbedtls_entropy_free(&dtls_srtp->entropy);
   mbedtls_ctr_drbg_free(&dtls_srtp->ctr_drbg);
 
-  if (dtls_srtp->role == DTLS_SRTP_ROLE_SERVER) {
-    mbedtls_ssl_cookie_free(&dtls_srtp->cookie_ctx);
-  }
+  mbedtls_ssl_cookie_free(&dtls_srtp->cookie_ctx);
 
   if (dtls_srtp->state == DTLS_SRTP_STATE_CONNECTED) {
     srtp_dealloc(dtls_srtp->srtp_in);
@@ -267,40 +265,35 @@ static int dtls_srtp_key_derivation(DtlsSrtp* dtls_srtp, const unsigned char* ma
 #endif
 
   // derive inbounds keys
+  memset(&dtls_srtp->srtp_in_policy, 0, sizeof(dtls_srtp->srtp_in_policy));
+  // derive outbounds keys
+  memset(&dtls_srtp->srtp_out_policy, 0, sizeof(dtls_srtp->srtp_out_policy));
 
-  memset(&dtls_srtp->remote_policy, 0, sizeof(dtls_srtp->remote_policy));
-
-  srtp_crypto_policy_set_rtp_default(&dtls_srtp->remote_policy.rtp);
-  srtp_crypto_policy_set_rtcp_default(&dtls_srtp->remote_policy.rtcp);
-
-  memcpy(dtls_srtp->remote_policy_key, key_material, SRTP_MASTER_KEY_LENGTH);
-  memcpy(dtls_srtp->remote_policy_key + SRTP_MASTER_KEY_LENGTH, key_material + SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_KEY_LENGTH, SRTP_MASTER_SALT_LENGTH);
+  memcpy(dtls_srtp->client_policy_key, key_material, SRTP_MASTER_KEY_LENGTH);
+  memcpy(dtls_srtp->client_policy_key + SRTP_MASTER_KEY_LENGTH, key_material + SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_KEY_LENGTH, SRTP_MASTER_SALT_LENGTH);
+  memcpy(dtls_srtp->server_policy_key, key_material + SRTP_MASTER_KEY_LENGTH, SRTP_MASTER_KEY_LENGTH);
+  memcpy(dtls_srtp->server_policy_key + SRTP_MASTER_KEY_LENGTH, key_material + SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_SALT_LENGTH, SRTP_MASTER_SALT_LENGTH);
 
-  dtls_srtp->remote_policy.ssrc.type = ssrc_any_inbound;
-  dtls_srtp->remote_policy.key = dtls_srtp->remote_policy_key;
-  dtls_srtp->remote_policy.next = NULL;
+  srtp_crypto_policy_set_rtp_default(&dtls_srtp->srtp_in_policy.rtp);
+  srtp_crypto_policy_set_rtcp_default(&dtls_srtp->srtp_in_policy.rtcp);
+  dtls_srtp->srtp_in_policy.ssrc.type = ssrc_any_inbound;
+  dtls_srtp->srtp_in_policy.key = (dtls_srtp->role == DTLS_SRTP_ROLE_SERVER) ? dtls_srtp->client_policy_key : dtls_srtp->server_policy_key;
+  dtls_srtp->srtp_in_policy.next = NULL;
 
-  if (srtp_create(&dtls_srtp->srtp_in, &dtls_srtp->remote_policy) != srtp_err_status_ok) {
+  if (srtp_create(&dtls_srtp->srtp_in, &dtls_srtp->srtp_in_policy) != srtp_err_status_ok) {
     LOGD("Error creating inbound SRTP session for component");
     return -1;
   }
 
   LOGI("Created inbound SRTP session");
 
-  // derive outbounds keys
-  memset(&dtls_srtp->local_policy, 0, sizeof(dtls_srtp->local_policy));
-
-  srtp_crypto_policy_set_rtp_default(&dtls_srtp->local_policy.rtp);
-  srtp_crypto_policy_set_rtcp_default(&dtls_srtp->local_policy.rtcp);
-
-  memcpy(dtls_srtp->local_policy_key, key_material + SRTP_MASTER_KEY_LENGTH, SRTP_MASTER_KEY_LENGTH);
-  memcpy(dtls_srtp->local_policy_key + SRTP_MASTER_KEY_LENGTH, key_material + SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_SALT_LENGTH, SRTP_MASTER_SALT_LENGTH);
-
-  dtls_srtp->local_policy.ssrc.type = ssrc_any_outbound;
-  dtls_srtp->local_policy.key = dtls_srtp->local_policy_key;
-  dtls_srtp->local_policy.next = NULL;
+  srtp_crypto_policy_set_rtp_default(&dtls_srtp->srtp_out_policy.rtp);
+  srtp_crypto_policy_set_rtcp_default(&dtls_srtp->srtp_out_policy.rtcp);
+  dtls_srtp->srtp_out_policy.ssrc.type = ssrc_any_outbound;
+  dtls_srtp->srtp_out_policy.key = (dtls_srtp->role == DTLS_SRTP_ROLE_SERVER) ? dtls_srtp->server_policy_key : dtls_srtp->client_policy_key;
+  dtls_srtp->srtp_out_policy.next = NULL;
 
-  if (srtp_create(&dtls_srtp->srtp_out, &dtls_srtp->local_policy) != srtp_err_status_ok) {
+  if (srtp_create(&dtls_srtp->srtp_out, &dtls_srtp->srtp_out_policy) != srtp_err_status_ok) {
     LOGE("Error creating outbound SRTP session");
     return -1;
   }
diff --git a/src/dtls_srtp.h b/src/dtls_srtp.h
index 09d2401..650472c 100644
--- a/src/dtls_srtp.h
+++ b/src/dtls_srtp.h
@@ -48,12 +48,12 @@ typedef struct DtlsSrtp {
   mbedtls_ctr_drbg_context ctr_drbg;
 
   // SRTP
-  srtp_policy_t remote_policy;
-  srtp_policy_t local_policy;
+  srtp_policy_t srtp_in_policy;
+  srtp_policy_t srtp_out_policy;
   srtp_t srtp_in;
   srtp_t srtp_out;
-  unsigned char remote_policy_key[SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_SALT_LENGTH];
-  unsigned char local_policy_key[SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_SALT_LENGTH];
+  unsigned char client_policy_key[SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_SALT_LENGTH];
+  unsigned char server_policy_key[SRTP_MASTER_KEY_LENGTH + SRTP_MASTER_SALT_LENGTH];
 
   int (*udp_send)(void* ctx, const unsigned char* buf, size_t len);
   int (*udp_recv)(void* ctx, unsigned char* buf, size_t len);
diff --git a/src/peer_connection.c b/src/peer_connection.c
index 56ec655..49f4569 100644
--- a/src/peer_connection.c
+++ b/src/peer_connection.c
@@ -38,6 +38,7 @@ struct PeerConnection {
   uint8_t temp_buf[CONFIG_MTU];
   uint8_t agent_buf[CONFIG_MTU];
   int agent_ret;
+  int is_offerer;
   int b_local_description_created;
 
   Buffer* audio_rb;
@@ -165,6 +166,7 @@ PeerConnection* peer_connection_create(PeerConfiguration* config) {
     return NULL;
   }
 
+  pc->is_offerer = 1;
   memcpy(&pc->config, config, sizeof(PeerConfiguration));
 
   agent_create(&pc->agent);
@@ -206,6 +208,14 @@ PeerConnection* peer_connection_create(PeerConfiguration* config) {
   return pc;
 }
 
+PeerConnection* peer_connection_create_ex(int is_offerer, PeerConfiguration* config) {
+  PeerConnection* pc = peer_connection_create(config);
+  if (pc != NULL) {
+    pc->is_offerer = is_offerer;
+  }
+  return pc;
+}
+
 void peer_connection_destroy(PeerConnection* pc) {
   if (pc) {
     sctp_destroy_socket(&pc->sctp);
@@ -268,14 +278,20 @@ int peer_connection_datachannel_send_sid(PeerConnection* pc, char* message, size
 #endif
 }
 
-static char* peer_connection_dtls_role_setup_value(DtlsSrtpRole d) {
-  return d == DTLS_SRTP_ROLE_SERVER ? "a=setup:passive" : "a=setup:active";
+static char* peer_connection_dtls_role_setup_value(int is_offerer) {
+  return is_offerer == 0 ? "a=setup:passive" : "a=setup:active";
 }
 
-static void peer_connection_state_new(PeerConnection* pc, DtlsSrtpRole role, int isOfferer) {
-  char* description = (char*)pc->temp_buf;
-
-  memset(pc->temp_buf, 0, sizeof(pc->temp_buf));
+static void peer_connection_state_new(PeerConnection* pc, int is_offerer) {
+  DtlsSrtpRole role = DTLS_SRTP_ROLE_CLIENT;
+  if (is_offerer) {
+    role = DTLS_SRTP_ROLE_CLIENT;
+    agent_clear_candidates(&pc->agent);
+    pc->agent.mode = AGENT_MODE_CONTROLLING;
+  } else {
+    role = DTLS_SRTP_ROLE_SERVER;
+    pc->agent.mode = AGENT_MODE_CONTROLLED;
+  }
 
   dtls_srtp_reset_session(&pc->dtls_srtp);
   dtls_srtp_init(&pc->dtls_srtp, role, pc);
@@ -284,13 +300,6 @@ static void peer_connection_state_new(PeerConnection* pc, DtlsSrtpRole role, int
 
   pc->sctp.connected = 0;
 
-  if (isOfferer) {
-    agent_clear_candidates(&pc->agent);
-    pc->agent.mode = AGENT_MODE_CONTROLLING;
-  } else {
-    pc->agent.mode = AGENT_MODE_CONTROLLED;
-  }
-
   agent_gather_candidate(&pc->agent, NULL, NULL, NULL);  // host address
   for (int i = 0; i < sizeof(pc->config.ice_servers) / sizeof(pc->config.ice_servers[0]); ++i) {
     if (pc->config.ice_servers[i].urls) {
@@ -299,6 +308,8 @@ static void peer_connection_state_new(PeerConnection* pc, DtlsSrtpRole role, int
     }
   }
 
+  char* description = (char*)pc->temp_buf;
+  memset(pc->temp_buf, 0, sizeof(pc->temp_buf));
   agent_get_local_description(&pc->agent, description, sizeof(pc->temp_buf));
 
   memset(&pc->local_sdp, 0, sizeof(pc->local_sdp));
@@ -311,7 +322,7 @@ static void peer_connection_state_new(PeerConnection* pc, DtlsSrtpRole role, int
   if (pc->config.video_codec == CODEC_H264) {
     sdp_append_h264(&pc->local_sdp);
     sdp_append(&pc->local_sdp, "a=fingerprint:sha-256 %s", pc->dtls_srtp.local_fingerprint);
-    sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(role));
+    sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(is_offerer));
     strcat(pc->local_sdp.content, description);
   }
 
@@ -320,7 +331,7 @@ static void peer_connection_state_new(PeerConnection* pc, DtlsSrtpRole role, int
 
       sdp_append_pcma(&pc->local_sdp);
       sdp_append(&pc->local_sdp, "a=fingerprint:sha-256 %s", pc->dtls_srtp.local_fingerprint);
-      sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(role));
+      sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(is_offerer));
       strcat(pc->local_sdp.content, description);
       break;
 
@@ -328,14 +339,14 @@ static void peer_connection_state_new(PeerConnection* pc, DtlsSrtpRole role, int
 
       sdp_append_pcmu(&pc->local_sdp);
       sdp_append(&pc->local_sdp, "a=fingerprint:sha-256 %s", pc->dtls_srtp.local_fingerprint);
-      sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(role));
+      sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(is_offerer));
       strcat(pc->local_sdp.content, description);
       break;
 
     case CODEC_OPUS:
       sdp_append_opus(&pc->local_sdp);
       sdp_append(&pc->local_sdp, "a=fingerprint:sha-256 %s", pc->dtls_srtp.local_fingerprint);
-      sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(role));
+      sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(is_offerer));
       strcat(pc->local_sdp.content, description);
 
     default:
@@ -345,7 +356,7 @@ static void peer_connection_state_new(PeerConnection* pc, DtlsSrtpRole role, int
   if (pc->config.datachannel) {
     sdp_append_datachannel(&pc->local_sdp);
     sdp_append(&pc->local_sdp, "a=fingerprint:sha-256 %s", pc->dtls_srtp.local_fingerprint);
-    sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(role));
+    sdp_append(&pc->local_sdp, peer_connection_dtls_role_setup_value(is_offerer));
     strcat(pc->local_sdp.content, description);
   }
 
@@ -367,7 +378,7 @@ int peer_connection_loop(PeerConnection* pc) {
     case PEER_CONNECTION_NEW:
 
       if (!pc->b_local_description_created) {
-        peer_connection_state_new(pc, DTLS_SRTP_ROLE_SERVER, 1);
+        peer_connection_state_new(pc, pc->is_offerer);
       }
       break;
 
@@ -480,7 +491,7 @@ void peer_connection_set_remote_description(PeerConnection* pc, const char* sdp_
   char buf[256];
   char* val_start = NULL;
   uint32_t* ssrc = NULL;
-  DtlsSrtpRole role = DTLS_SRTP_ROLE_SERVER;
+  DtlsSrtpRole role = DTLS_SRTP_ROLE_CLIENT;
   int is_update = 0;
   Agent* agent = &pc->agent;
 
@@ -490,7 +501,7 @@ void peer_connection_set_remote_description(PeerConnection* pc, const char* sdp_
     buf[line - start] = '\0';
 
     if (strstr(buf, "a=setup:passive")) {
-      role = DTLS_SRTP_ROLE_CLIENT;
+      role = DTLS_SRTP_ROLE_SERVER;
     }
 
     if (strstr(buf, "a=fingerprint")) {
@@ -522,7 +533,7 @@ void peer_connection_set_remote_description(PeerConnection* pc, const char* sdp_
   }
 
   if (!pc->b_local_description_created) {
-    peer_connection_state_new(pc, role, 0);
+    peer_connection_state_new(pc, role == DTLS_SRTP_ROLE_CLIENT ? 0 : 1);
   }
 
   agent_set_remote_description(&pc->agent, (char*)sdp_text);
diff --git a/src/peer_connection.h b/src/peer_connection.h
index d917884..127a38f 100644
--- a/src/peer_connection.h
+++ b/src/peer_connection.h
@@ -79,6 +79,8 @@ void* peer_connection_get_sctp(PeerConnection* pc);
 
 PeerConnection* peer_connection_create(PeerConfiguration* config);
 
+PeerConnection* peer_connection_create_ex(int is_offerer, PeerConfiguration* config);
+
 void peer_connection_destroy(PeerConnection* pc);
 
 void peer_connection_close(PeerConnection* pc);
diff --git a/tests/test_peer_connection.c b/tests/test_peer_connection.c
index fa17832..c054d4e 100644
--- a/tests/test_peer_connection.c
+++ b/tests/test_peer_connection.c
@@ -64,8 +64,8 @@ int main(int argc, char* argv[]) {
 
   peer_init();
 
-  test_user_data.offer_peer_connection = peer_connection_create(&config);
-  test_user_data.answer_peer_connection = peer_connection_create(&config);
+  test_user_data.offer_peer_connection = peer_connection_create_ex(1, &config);
+  test_user_data.answer_peer_connection = peer_connection_create_ex(0, &config);
 
   peer_connection_oniceconnectionstatechange(test_user_data.offer_peer_connection, onconnectionstatechange_offerer_peer_connection);
   peer_connection_oniceconnectionstatechange(test_user_data.answer_peer_connection, onconnectionstatechange_answerer_peer_connection);