Use SSL_CTX_up_ref() with MOSQ_OPT_SSL_CTX*.

This limits the use of those options to openssl 1.1.0 and greater.

lib/mosquitto.h

@@ -974,6 +974,7 @@ libmosq_EXPORT int mosquitto_threaded_set(struct mosquitto *mosq, bool threaded)
  *	          onus is on you to ensure that you are using secure settings.
  *	          Setting to NULL means that libmosquitto will use its own SSL_CTX
  *	          if TLS is to be used.
+ *	          This option is only available for openssl 1.1.0 and higher.
  *
  *	MOSQ_OPT_SSL_CTX_WITH_DEFAULTS
  *	          Value must be an int set to 1 or 0. If set to 1, then the user
@@ -983,6 +984,7 @@ libmosq_EXPORT int mosquitto_threaded_set(struct mosquitto *mosq, bool threaded)
  *	          option then you must configure the TLS options as normal, i.e.
  *	          you should use <mosquitto_tls_set> to configure the cafile/capath
  *	          as a minimum.
+ *	          This option is only available for openssl 1.1.0 and higher.
  */
 libmosq_EXPORT int mosquitto_opts_set(struct mosquitto *mosq, enum mosq_opt_t option, void *value);
 

lib/options.c

@@ -265,18 +265,21 @@ int mosquitto_opts_set(struct mosquitto *mosq, enum mosq_opt_t option, void *val
 			}
 			break;
 		case MOSQ_OPT_SSL_CTX:
-#ifdef WITH_TLS
+#if defined(WITH_TLS) && OPENSSL_VERSION_NUMBER >= 0x10100000L
 			mosq->ssl_ctx = (SSL_CTX *)value;
+			if(mosq->ssl_ctx){
+				SSL_CTX_up_ref(mosq->ssl_ctx);
+			}
 			break;
 #else
-			return MOSQ_ERR_UNSUPPORTED;
+			return MOSQ_ERR_NOT_SUPPORTED;
 #endif
 		case MOSQ_OPT_SSL_CTX_WITH_DEFAULTS:
-#ifdef WITH_TLS
+#if defined(WITH_TLS) && OPENSSL_VERSION_NUMBER >= 0x10100000L
 			mosq->ssl_ctx_defaults = true;
 			break;
 #else
-			return MOSQ_ERR_UNSUPPORTED;
+			return MOSQ_ERR_NOT_SUPPORTED;
 #endif
 		default:
 			return MOSQ_ERR_INVAL;