change(esp-tls): make wolfSSL backend send SNI and enable OCSP

Almost all sites these days are virtually hosted and hence
SNI (server name indicator TLS extension) should be enabled by
default.

In addition this change enables OCSP (online server status protocol)
support for esp-tls clients using the wolfSSL backend.
The 3 code lines enable OCSP stabling v1.
By default this feature is disabled.
(I will send another PR on esp-wolfssl repository to allow to
enable it easily.)

components/esp-tls/esp_tls_wolfssl.c

@@ -288,6 +288,11 @@ static esp_err_t set_client_config(const char *hostname, size_t hostlen, esp_tls
  free(use_host);
  return ESP_ERR_WOLFSSL_SSL_SET_HOSTNAME_FAILED;
  }
+ /* Mimic the semantics of mbedtls_ssl_set_hostname() */
+ if ((ret = wolfSSL_CTX_UseSNI(tls->priv_ctx, WOLFSSL_SNI_HOST_NAME, use_host, strlen(use_host))) != WOLFSSL_SUCCESS) {
+ ESP_LOGE(TAG, "wolfSSL_CTX_UseSNI failed, returned %d", ret);
+ return ESP_ERR_WOLFSSL_SSL_SET_HOSTNAME_FAILED;
+ }
  free(use_host);
  }
 
@@ -310,6 +315,24 @@ static esp_err_t set_client_config(const char *hostname, size_t hostlen, esp_tls
 #endif /* CONFIG_WOLFSSL_HAVE_ALPN */
  }
 
+#ifdef CONFIG_WOLFSSL_HAVE_OCSP
+ /* enable OCSP certificate status check for this TLS context */
+ if ((ret = wolfSSL_CTX_EnableOCSP((WOLFSSL_CTX *)tls->priv_ctx, WOLFSSL_OCSP_CHECKALL)) != WOLFSSL_SUCCESS) {
+ ESP_LOGE(TAG, "wolfSSL_CTX_EnableOCSP failed, returned %d", ret);
+ return ESP_ERR_WOLFSSL_CTX_SETUP_FAILED;
+ }
+ /* enable OCSP stapling for this TLS context */
+ if ((ret = wolfSSL_CTX_EnableOCSPStapling((WOLFSSL_CTX *)tls->priv_ctx )) != WOLFSSL_SUCCESS) {
+ ESP_LOGE(TAG, "wolfSSL_CTX_EnableOCSPStapling failed, returned %d", ret);
+ return ESP_ERR_WOLFSSL_CTX_SETUP_FAILED;
+ }
+ /* set option to use OCSP v1 stapling with nounce extension */
+ if ((ret = wolfSSL_UseOCSPStapling((WOLFSSL *)tls->priv_ssl, WOLFSSL_CSR_OCSP, WOLFSSL_CSR_OCSP_USE_NONCE)) != WOLFSSL_SUCCESS) {
+ ESP_LOGE(TAG, "wolfSSL_UseOCSPStapling failed, returned %d", ret);
+ return ESP_ERR_WOLFSSL_SSL_SETUP_FAILED;
+ }
+#endif /* CONFIG_WOLFSSL_HAVE_OCSP */
+
  wolfSSL_set_fd((WOLFSSL *)tls->priv_ssl, tls->sockfd);
  return ESP_OK;
 }
@@ -526,7 +549,7 @@ void esp_wolfssl_server_session_delete(esp_tls_t *tls)
 
 esp_err_t esp_wolfssl_init_global_ca_store(void)
 {
- /* This function is just to provide consistancy between function calls of esp_tls.h and wolfssl */
+ /* This function is just to provide consistency between function calls of esp_tls.h and wolfssl */
  return ESP_OK;
 }