Connection-ID: Only change source port when CID has been negotiated

Only support changing the client's source port if the DTLS library
has support / configured for CID.

Used when debugging server handling source address changes and CID
is in use.

Add in support for TinyDTLS (Client only) if TinyDTLS is patched
appropriately (not currently available on TinyDTLS main branch).

Add in new function coap_dtls_cid_is_supported().

examples/coap-client.c

@@ -1924,8 +1924,12 @@ main(int argc, char **argv) {
   coap_register_nack_handler(ctx, nack_handler);
   if (the_token.length > COAP_TOKEN_DEFAULT_MAX)
     coap_context_set_max_token_size(ctx, the_token.length);
-  if (cid_every)
-    coap_context_set_cid_tuple_change(ctx, cid_every);
+  if (cid_every) {
+    if (!coap_context_set_cid_tuple_change(ctx, cid_every)) {
+      coap_log_warn("coap_context_set_cid_tuple_change: "
+                    "Unable to set CID tuple change\n");
+    }
+  }
 
   session = get_session(ctx,
                         node_str[0] ? node_str : NULL,

include/coap3/coap_dtls.h

@@ -29,6 +29,8 @@
  * @{
  */
 
+int coap_dtls_cid_is_supported(void);
+
 typedef struct coap_dtls_pki_t coap_dtls_pki_t;
 
 #ifndef COAP_DTLS_HINT_LENGTH

include/coap3/coap_dtls_internal.h

@@ -481,6 +481,17 @@ int coap_dtls_define_issue(coap_define_issue_key_t type,
                            coap_dtls_key_t *key,
                            const coap_dtls_role_t role,
                            int ret);
+
+/**
+ * Set the Connection ID client tuple frequency change for testing CIDs.
+ *
+ * @param context        The coap_context_t object.
+ * @param every          Change the client's source port @p every packets sent.
+ *
+ * @return @c 1 if frequency change set (CID supported), else @c 0.
+ */
+int coap_dtls_set_cid_tuple_change(coap_context_t *context, uint8_t every);
+
 /** @} */
 
 #endif /* COAP_DTLS_INTERNAL_H */

include/coap3/coap_net.h

@@ -235,8 +235,10 @@ void coap_context_set_keepalive(coap_context_t *context, unsigned int seconds);
  *
  * @param context        The coap_context_t object.
  * @param every          Change the client's source port @p every packets sent.
+ *
+ * @return @c 1 if frequency change set (CID supported), else @c 0.
  */
-void coap_context_set_cid_tuple_change(coap_context_t *context, uint8_t every);
+int coap_context_set_cid_tuple_change(coap_context_t *context, uint8_t every);
 
 /**
  * Set the maximum token size (RFC8974).

include/coap3/coap_session_internal.h

@@ -203,6 +203,10 @@ struct coap_session_t {
 #endif /* COAP_OSCORE_SUPPORT */
   volatile uint8_t max_token_checked; /**< Check for max token size
                                            coap_ext_token_check_t */
+#if COAP_CLIENT_SUPPORT
+  uint8_t negotiated_cid;         /**< Set for a client if CID negotiated */
+#endif /* COAP_CLIENT_SUPPORT */
+  uint8_t is_dtls13;              /**< Set if session is DTLS1.3 */
   coap_mid_t remote_test_mid;     /**< mid used for checking remote
                                        support */
   uint32_t max_token_size;        /**< Largest token size supported RFC8974 */

libcoap-3.map

@@ -81,6 +81,7 @@ global:
   coap_delete_str_const;
   coap_delete_string;
   coap_delete_uri;
+  coap_dtls_cid_is_supported;
   coap_dtls_get_log_level;
   coap_dtls_is_supported;
   coap_dtls_pkcs11_is_supported;

libcoap-3.sym

@@ -79,6 +79,7 @@ coap_delete_resource
 coap_delete_str_const
 coap_delete_string
 coap_delete_uri
+coap_dtls_cid_is_supported
 coap_dtls_get_log_level
 coap_dtls_is_supported
 coap_dtls_pkcs11_is_supported

man/coap_context.txt.in

@@ -65,7 +65,7 @@ size_t _max_token_size_);*
 
 *void *coap_context_get_app_data(const coap_context_t *_context_);*
 
-*void coap_context_set_cid_tuple_change(coap_context_t *_context_context, uint8_t _every_);*
+*int coap_context_set_cid_tuple_change(coap_context_t *_context_context, uint8_t _every_);*
 
 For specific (D)TLS library support, link with
 *-lcoap-@LIBCOAP_API_VERSION@-notls*, *-lcoap-@LIBCOAP_API_VERSION@-gnutls*,
@@ -190,7 +190,8 @@ pointer previously defined by *coap_context_set_app_data*().
 
 The *coap_context_set_cid_tuple_change*() function is used to define to a client
 to force the client's port to change _every_ packets sent, providing the ability
-to test a CID (RFC9146) enabled server.
+to test a CID (RFC9146) enabled server. Only supported by DTLS libraries that
+support CID.
 
 RETURN VALUES
 -------------
@@ -211,6 +212,8 @@ out an idle server session.
 
 *coap_context_get_app_data*() returns a previously defined pointer.
 
+*coap_context_set_cid_tuple_change*() returns 1 on success, else 0;
+
 SEE ALSO
 --------
 *coap_session*(3)

src/coap_debug.c

@@ -1233,6 +1233,7 @@ coap_string_tls_support(char *buffer, size_t bufsize) {
   const int have_pki = coap_dtls_pki_is_supported();
   const int have_pkcs11 = coap_dtls_pkcs11_is_supported();
   const int have_rpk = coap_dtls_rpk_is_supported();
+  const int have_cid = coap_dtls_cid_is_supported();
   const int have_oscore = coap_oscore_is_supported();
   const int have_ws = coap_ws_is_supported();
 
@@ -1241,13 +1242,14 @@ coap_string_tls_support(char *buffer, size_t bufsize) {
     return buffer;
   }
   snprintf(buffer, bufsize,
-           "(%sDTLS and %sTLS support; %sPSK, %sPKI, %sPKCS11, and %sRPK support)\n(%sOSCORE)\n(%sWebSockets)",
+           "(%sDTLS and %sTLS support; %sPSK, %sPKI, %sPKCS11, %sRPK and %sCID support)\n(%sOSCORE)\n(%sWebSockets)",
            have_dtls ? "" : "No ",
            have_tls ? "" : "no ",
            have_psk ? "" : "no ",
            have_pki ? "" : "no ",
            have_pkcs11 ? "" : "no ",
            have_rpk ? "" : "no ",
+           have_cid ? "" : "no ",
            have_oscore ? "Have " : "No ",
            have_ws ? "Have " : "No ");
   return buffer;

src/coap_gnutls.c

@@ -243,6 +243,24 @@ coap_dtls_rpk_is_supported(void) {
 #endif /* GNUTLS_VERSION_NUMBER < 0x030606 */
 }
 
+/*
+ * return 0 failed
+ *        1 passed
+ */
+int
+coap_dtls_cid_is_supported(void) {
+  return 0;
+}
+
+#if COAP_CLIENT_SUPPORT
+int
+coap_dtls_set_cid_tuple_change(coap_context_t *c_context, uint8_t every) {
+  (void)c_context;
+  (void)every;
+  return 0;
+}
+#endif /* COAP_CLIENT_SUPPORT */
+
 coap_tls_version_t *
 coap_get_tls_library_version(void) {
   static coap_tls_version_t version;

src/coap_io.c

@@ -782,8 +782,9 @@ static uint32_t cid_track_counter;
 static void
 coap_test_cid_tuple_change(coap_session_t *session) {
   if (session->type == COAP_SESSION_TYPE_CLIENT &&
+      session->negotiated_cid &&
       session->state == COAP_SESSION_STATE_ESTABLISHED &&
-      COAP_PROTO_NOT_RELIABLE(session->proto) && session->context->testing_cids) {
+      session->proto == COAP_PROTO_DTLS && session->context->testing_cids) {
     if ((++cid_track_counter) % session->context->testing_cids == 0) {
       coap_address_t local_if = session->addr_info.local;
       uint16_t port = coap_address_get_port(&local_if);

src/coap_mbedtls.c

@@ -1467,6 +1467,31 @@ do_mbedtls_handshake(coap_session_t *c_session,
     coap_log_debug("*  %s: Mbed TLS established\n",
                    coap_session_str(c_session));
     ret = 1;
+#ifdef MBEDTLS_SSL_DTLS_CONNECTION_ID
+#if COAP_CLIENT_SUPPORT
+    if (c_session->type == COAP_SESSION_TYPE_CLIENT &&
+        c_session->proto == COAP_PROTO_DTLS) {
+      coap_mbedtls_context_t *m_context;
+
+      m_context = (coap_mbedtls_context_t *)c_session->context->dtls_context;
+      if ((m_context->psk_pki_enabled & IS_PSK && c_session->cpsk_setup_data.use_cid) ||
+          m_context->setup_data.use_cid) {
+        unsigned char peer_cid[MBEDTLS_SSL_CID_OUT_LEN_MAX];
+        int enabled;
+        size_t peer_cid_len;
+
+        /* See whether CID was negotiated */
+        if (mbedtls_ssl_get_peer_cid(&m_env->ssl, &enabled, peer_cid, &peer_cid_len) == 0 &&
+            enabled == MBEDTLS_SSL_CID_ENABLED) {
+          c_session->negotiated_cid = 1;
+        } else {
+          coap_log_info("** %s: CID was not negotiated\n", coap_session_str(c_session));
+          c_session->negotiated_cid = 0;
+        }
+      }
+    }
+#endif /* COAP_CLIENT_SUPPORT */
+#endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */
     break;
   case MBEDTLS_ERR_SSL_WANT_READ:
   case MBEDTLS_ERR_SSL_WANT_WRITE:
@@ -1886,6 +1911,33 @@ coap_dtls_rpk_is_supported(void) {
   return 0;
 }
 
+/*
+ * return 0 failed
+ *        1 passed
+ */
+int
+coap_dtls_cid_is_supported(void) {
+#ifdef MBEDTLS_SSL_DTLS_CONNECTION_ID
+  return 1;
+#else /* ! MBEDTLS_SSL_DTLS_CONNECTION_ID */
+  return 0;
+#endif /* ! MBEDTLS_SSL_DTLS_CONNECTION_ID */
+}
+
+#if COAP_CLIENT_SUPPORT
+int
+coap_dtls_set_cid_tuple_change(coap_context_t *c_context, uint8_t every) {
+#ifdef MBEDTLS_SSL_DTLS_CONNECTION_ID
+  c_context->testing_cids = every;
+  return 1;
+#else /* ! MBEDTLS_SSL_DTLS_CONNECTION_ID */
+  (void)c_context;
+  (void)every;
+  return 0;
+#endif /* ! MBEDTLS_SSL_DTLS_CONNECTION_ID */
+}
+#endif /* COAP_CLIENT_SUPPORT */
+
 void *
 coap_dtls_new_context(coap_context_t *c_context) {
   coap_mbedtls_context_t *m_context;

src/coap_net.c

@@ -459,13 +459,14 @@ coap_context_set_keepalive(coap_context_t *context, unsigned int seconds) {
   context->ping_timeout = seconds;
 }
 
-void
+int
 coap_context_set_cid_tuple_change(coap_context_t *context, uint8_t every) {
 #if COAP_CLIENT_SUPPORT
-  context->testing_cids = every;
+  return coap_dtls_set_cid_tuple_change(context, every);
 #else /* ! COAP_CLIENT_SUPPORT */
   (void)context;
   (void)every;
+  return 0;
 #endif /* ! COAP_CLIENT_SUPPORT */
 }
 

src/coap_notls.c

@@ -78,6 +78,24 @@ coap_dtls_rpk_is_supported(void) {
   return 0;
 }
 
+/*
+ * return 0 failed
+ *        1 passed
+ */
+int
+coap_dtls_cid_is_supported(void) {
+  return 0;
+}
+
+#if COAP_CLIENT_SUPPORT
+int
+coap_dtls_set_cid_tuple_change(coap_context_t *c_context, uint8_t every) {
+  (void)c_context;
+  (void)every;
+  return 0;
+}
+#endif /* COAP_CLIENT_SUPPORT */
+
 coap_tls_version_t *
 coap_get_tls_library_version(void) {
   static coap_tls_version_t version;

src/coap_openssl.c

@@ -256,6 +256,24 @@ coap_dtls_rpk_is_supported(void) {
   return 0;
 }
 
+/*
+ * return 0 failed
+ *        1 passed
+ */
+int
+coap_dtls_cid_is_supported(void) {
+  return 0;
+}
+
+#if COAP_CLIENT_SUPPORT
+int
+coap_dtls_set_cid_tuple_change(coap_context_t *c_context, uint8_t every) {
+  (void)c_context;
+  (void)every;
+  return 0;
+}
+#endif /* COAP_CLIENT_SUPPORT */
+
 coap_tls_version_t *
 coap_get_tls_library_version(void) {
   static coap_tls_version_t version;

src/coap_session.c

@@ -1148,6 +1148,7 @@ coap_endpoint_get_session(coap_endpoint_t *endpoint,
 #define DTLS_HT_CLIENT_HELLO  1  /* Client Hello handshake type */
 #define DTLS_CT_CID          25  /* Content Type Connection ID */
 #define OFF_CID              11  /* offset of CID in dtls_record_handshake_t */
+#define OFF_CID_DTLS13        1  /* offset of CID in DTLS1.3 Unified Header */
 
     const uint8_t *payload = (const uint8_t *)packet->payload;
     size_t length = packet->length;
@@ -1157,18 +1158,24 @@ coap_endpoint_get_session(coap_endpoint_t *endpoint,
                      OFF_HANDSHAKE_TYPE + 1);
       return NULL;
     }
-    if (payload[OFF_CONTENT_TYPE] == DTLS_CT_CID) {
+    if ((payload[OFF_CONTENT_TYPE] & 0x30) == 0x30 ||
+        payload[OFF_CONTENT_TYPE] == DTLS_CT_CID) {
       /* Client may have changed its IP address */
       int changed = 0;
 
       SESSIONS_ITER(endpoint->sessions, session, rtmp) {
         if (session->client_cid) {
-          if (memcmp(session->client_cid->s, &payload[OFF_CID],
-                     session->client_cid->length) == 0) {
+          if ((session->is_dtls13 && (payload[OFF_CONTENT_TYPE] & 0x30) == 0x30 &&
+               memcmp(session->client_cid->s, &payload[OFF_CID_DTLS13],
+                      session->client_cid->length) == 0) ||
+              (!session->is_dtls13 && payload[OFF_CONTENT_TYPE] == DTLS_CT_CID &&
+               memcmp(session->client_cid->s, &payload[OFF_CID],
+                      session->client_cid->length) == 0)) {
             /* Updating IP address */
             coap_log_info("***%s: CID: Old Client Session\n", coap_session_str(session));
             SESSIONS_DELETE(endpoint->sessions, session);
             session->addr_info = packet->addr_info;
+            memcpy(&session->addr_hash, &addr_hash, sizeof(session->addr_hash));
             SESSIONS_ADD(endpoint->sessions, session);
             coap_log_info("***%s: CID: New Client Session\n", coap_session_str(session));
             return session;
@@ -1184,7 +1191,8 @@ coap_endpoint_get_session(coap_endpoint_t *endpoint,
       /* only log if not a late alert */
       if (payload[OFF_CONTENT_TYPE] != DTLS_CT_ALERT)
         coap_log_debug("coap_dtls_hello: ContentType %d Handshake %d dropped\n",
-                       payload[OFF_CONTENT_TYPE], payload[OFF_HANDSHAKE_TYPE]);
+                       payload[OFF_CONTENT_TYPE],
+                       payload[OFF_HANDSHAKE_TYPE]);
       return NULL;
     }
   }