TLS fix ECDSA and add 'SetOption165 1' to enable ECDSA in addition to RSA (#24000)

CHANGELOG.md

@@ -29,6 +29,7 @@ All notable changes to this project will be documented in this file.
 ### Fixed
 - Berry fixed 'be_top is non zero' warning when calling C mapped functions (#23989)
 - Berry fixed 'be_top is non zero' when `Br` command fails (#23990)
+- TLS fix ECDSA and add `SetOption165 1` to enable ECDSA in addition to RSA
 
 ## [15.0.1.4] 20251002
 ### Added

lib/lib_ssl/tls_mini/src/WiFiClientSecureLightBearSSL.cpp

@@ -930,8 +930,8 @@ extern "C" {
     br_ssl_engine_set_ghash(&cc->eng, &br_ghash_ctmul32);
 
     // we support only P256 EC curve for AWS IoT, no EC curve for Letsencrypt unless forced
-    br_ssl_engine_set_ec(&cc->eng, &br_ec_p256_m15); // TODO
+    br_ssl_engine_set_ec(&cc->eng, &br_ec_p256_m15);
-#ifndef ESP8266
+#ifdef ESP32
     br_ssl_engine_set_ecdsa(&cc->eng, &br_ecdsa_i15_vrfy_asn1);
 #endif
   }
@@ -986,6 +986,9 @@ bool WiFiClientSecure_light::_connectSSL(const char* hostName) {
       br_x509_minimal_init(x509_minimal, &br_sha256_vtable, _ta_P, _ta_size);
       br_x509_minimal_set_rsa(x509_minimal, br_ssl_engine_get_rsavrfy(_eng));
       br_x509_minimal_set_hash(x509_minimal, br_sha256_ID, &br_sha256_vtable);
+#ifdef ESP32
+      br_x509_minimal_set_ecdsa(x509_minimal, &br_ec_all_m15, &br_ecdsa_i15_vrfy_asn1);
+#endif // ESP32
       br_ssl_engine_set_x509(_eng, &x509_minimal->vtable);
       uint32_t now = UtcTime();
       uint32_t cfg_time = CfgTime();

lib/lib_ssl/tls_mini/src/WiFiClientSecureLightBearSSL.h

@@ -120,6 +120,9 @@ class WiFiClientSecure_light : public WiFiClient {
         return br_ssl_engine_last_error(_eng);
       }
     }
+    int32_t getLastCipherSuite(void) {
+      return _eng->session.cipher_suite;
+    }
     inline void setLastError(int32_t err) {
       _last_error = err;
     }
@@ -131,6 +134,9 @@ class WiFiClientSecure_light : public WiFiClient {
     }
 
     void setInsecure();
+    void setECDSA(bool ecdsa) {
+      _rsa_only = !ecdsa;
+    };
 
     void setDomainName(const char * domain) {
       _domain = domain;

tasmota/include/tasmota_types.h

@@ -199,7 +199,7 @@ typedef union {                            // Restricted by MISRA-C Rule 18.4 bu
     uint32_t no_export_energy_today : 1;   // bit 16 (v14.3.0.7) - SetOption162 - (Energy) Do not add export energy to energy today (1)
     uint32_t gui_device_name : 1;          // bit 17 (v14.4.1.1) - SetOption163 - GUI_NOSHOW_DEVICENAME - (GUI) Disable display of GUI device name (1)
     uint32_t wizmote_enabled : 1;          // bit 18 (v14.4.1.4) - SetOption164 - (WizMote) Enable WiZ Smart Remote support (1)
-    uint32_t spare19 : 1;                  // bit 19
+    uint32_t tls_use_ecdsa : 1;            // bit 19 (v15.0.1.0) - SetOption165 - (TLS) Enable ECDSA validation in addition to RSA
     uint32_t spare20 : 1;                  // bit 20
     uint32_t spare21 : 1;                  // bit 21
     uint32_t spare22 : 1;                  // bit 22

tasmota/my_user_config.h

@@ -173,8 +173,9 @@
 #define MQTT_INDEX_SEPARATOR   false             // [SetOption64] Enable "_" instead of "-" as sensor index separator
 #define MQTT_TUYA_RECEIVED     false             // [SetOption66] Enable TuyaMcuReceived messages over Mqtt
 #define MQTT_ONLY_JSON_OUTPUT  false             // [SetOption90] Disable non-json messages
-#define MQTT_TLS_ENABLED       false             // [SetOption103] Enable TLS mode (requires TLS version)
+#define MQTT_TLS_ENABLED       false             // [SetOption103] Enable TLS mode
-#define MQTT_TLS_FINGERPRINT   false             // [SetOption132] Force TLS fingerprint validation instead of CA (requires TLS version)
+#define MQTT_TLS_FINGERPRINT   false             // [SetOption132] Force TLS fingerprint validation instead of CA
+#define MQTT_TLS_ECDSA         false             // [SetOption165] Enable TLS ECDSA validation in addition to RSA, false by default but automatically set to 'true' in case of a cipher error '296'
 
 // -- HTTP ----------------------------------------
 #define WEB_SERVER             2                 // [WebServer] Web server (0 = Off, 1 = Start as User, 2 = Start as Admin)

tasmota/tasmota_support/settings.ino

@@ -1448,6 +1448,7 @@ void SettingsDefaultSet2(void) {
 
   // Matter
   flag6.matter_enabled |= MATTER_ENABLED;
+  flag6.tls_use_ecdsa |= MQTT_TLS_ECDSA;
 
   Settings->flag = flag;
   Settings->flag2 = flag2;

tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino

@@ -262,6 +262,7 @@ void MqttInit(void) {
     if (!Settings->flag5.tls_use_fingerprint) {
       tlsClient->setTrustAnchor(Tasmota_TA, nitems(Tasmota_TA));
     }
+    tlsClient->setECDSA(Settings->flag6.tls_use_ecdsa);
 
     MqttClient.setClient(*tlsClient);
   } else {
@@ -1391,6 +1392,14 @@ void MqttReconnect(void) {
       120 : 376 : BR_ALERT_NO_APPLICATION_PROTOCOL
 */
       AddLog(LOG_LEVEL_INFO, PSTR(D_LOG_MQTT "TLS connection error: %d"), tlsClient->getLastError());
+      if (tlsClient->getLastError() == 296) {
+        // in this special case of cipher mismatch, we force enable ECDSA
+        // this would be the case for newer letsencrypt certificates now defaulting
+        // to EC certificates requiring ECDSA instead of RSA
+        Settings->flag6.tls_use_ecdsa = true;
+        tlsClient->setECDSA(Settings->flag6.tls_use_ecdsa);
+        AddLog(LOG_LEVEL_INFO, PSTR(D_LOG_MQTT "TLS now enabling ECDSA 'SetOption165 1'"), tlsClient->getLastError());
+      }
     }
 #endif
 /*
@@ -1408,6 +1417,18 @@ void MqttReconnect(void) {
 */
     MqttDisconnected(MqttClient.state());
   }
+#ifdef USE_MQTT_TLS
+  if (Mqtt.mqtt_tls) {
+    int32_t cipher_suite = tlsClient->getLastCipherSuite();
+    if (BR_TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 == cipher_suite) {
+      AddLog(LOG_LEVEL_DEBUG, PSTR(D_LOG_MQTT "TLS cipher suite: %s"), PSTR("ECDHE_RSA_AES_128_GCM_SHA256"));
+    } else if (BR_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 == cipher_suite) {
+      AddLog(LOG_LEVEL_DEBUG, PSTR(D_LOG_MQTT "TLS cipher suite: %s"), PSTR("ECDHE_ECDSA_AES_128_GCM_SHA256"));
+    } else if (0 != cipher_suite) {
+      AddLog(LOG_LEVEL_DEBUG, PSTR(D_LOG_MQTT "TLS cipher suite: 0x%04X"), cipher_suite);
+    }
+  }
+#endif // USE_MQTT_TLS
 }
 
 void MqttCheck(void) {