fix(advanced_ota): Added support for cert bundle in advanced OTA

1. Added support for cert bundle in advanced OTA
2. This allows to easily test example with different public servers

examples/system/ota/advanced_https_ota/main/CMakeLists.txt

@@ -3,6 +3,6 @@ idf_component_register(SRCS "advanced_https_ota_example.c" "ble_helper/bluedroid
                     INCLUDE_DIRS "." "./ble_helper/include/"
                     PRIV_REQUIRES esp_http_client app_update esp_https_ota
                                   nvs_flash esp_netif esp_wifi efuse bt
-                                  protocomm
+                                  protocomm mbedtls
                     # Embed the server root certificate into the final binary
                     EMBED_TXTFILES ${project_dir}/server_certs/ca_cert.pem)

examples/system/ota/advanced_https_ota/main/Kconfig.projbuild

@@ -53,4 +53,13 @@ menu "Example Configuration"
             This option allows one to configure the OTA process to resume downloading the OTA image
             from where it left off in case of an error or reboot.
 
+    config EXAMPLE_USE_CERT_BUNDLE
+        bool "Enable certificate bundle"
+        default y
+        depends on MBEDTLS_CERTIFICATE_BUNDLE
+        help
+            Enable trusted root certificate bundle. This approach allows to have
+            OTA updates functional with any public server without requirement
+            to explicitly add its server certificate.
+
 endmenu

examples/system/ota/advanced_https_ota/main/advanced_https_ota_example.c

@@ -22,6 +22,11 @@
 #include "nvs_flash.h"
 #include "protocol_examples_common.h"
 
+
+#ifdef CONFIG_EXAMPLE_USE_CERT_BUNDLE
+#include "esp_crt_bundle.h"
+#endif
+
 #if CONFIG_BOOTLOADER_APP_ANTI_ROLLBACK
 #include "esp_efuse.h"
 #endif
@@ -221,7 +226,11 @@ void advanced_ota_example_task(void *pvParameter)
     esp_err_t ota_finish_err = ESP_OK;
     esp_http_client_config_t config = {
         .url = CONFIG_EXAMPLE_FIRMWARE_UPGRADE_URL,
+#ifdef CONFIG_EXAMPLE_USE_CERT_BUNDLE
+        .crt_bundle_attach = esp_crt_bundle_attach,
+#else
         .cert_pem = (char *)server_cert_pem_start,
+#endif
         .timeout_ms = CONFIG_EXAMPLE_OTA_RECV_TIMEOUT,
         .keep_alive_enable = true,
 #ifdef CONFIG_EXAMPLE_ENABLE_PARTIAL_HTTP_DOWNLOAD

examples/system/ota/advanced_https_ota/sdkconfig.defaults

@@ -2,3 +2,8 @@
 # partition table layout, with a 4MB flash size
 CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
 CONFIG_PARTITION_TABLE_TWO_OTA_LARGE=y
+
+# Certificate bundle configuration
+CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_DEFAULT_CMN=y
+CONFIG_MBEDTLS_CUSTOM_CERTIFICATE_BUNDLE=y
+CONFIG_MBEDTLS_CUSTOM_CERTIFICATE_BUNDLE_PATH="server_certs/ca_cert.pem"