ESP HTTPS OTA

Overview

esp_https_ota provides simplified APIs to perform firmware upgrades over HTTPS. It’s an abstraction layer over existing OTA APIs.

Application Example

esp_err_t do_firmware_upgrade()
{
    esp_http_client_config_t config = {
        .url = CONFIG_FIRMWARE_UPGRADE_URL,
        .cert_pem = (char *)server_cert_pem_start,
    };
    esp_https_ota_config_t ota_config = {
        .http_config = &config,
    };
    esp_err_t ret = esp_https_ota(&ota_config);
    if (ret == ESP_OK) {
        esp_restart();
    } else {
        return ESP_FAIL;
    }
    return ESP_OK;
}

Server Verification

Please refer to ESP-TLS: TLS Server Verification for more information on server verification. The root certificate (in PEM format) needs to be provided to the esp_http_client_config_t::cert_pem member.

备注

The server-endpoint root certificate should be used for verification instead of any intermediate ones from the certificate chain. The reason being that the root certificate has the maximum validity and usually remains the same for a long period of time. Users can also use the ESP x509 Certificate Bundle feature for verification, which covers most of the trusted root certificates (using the esp_http_client_config_t::crt_bundle_attach member).

Partial Image Download over HTTPS

To use partial image download feature, enable partial_http_download configuration in esp_https_ota_config_t. When this configuration is enabled, firmware image will be downloaded in multiple HTTP requests of specified size. Maximum content length of each request can be specified by setting max_http_request_size to required value.

This option is useful while fetching image from a service like AWS S3, where mbedTLS Rx buffer size (CONFIG_MBEDTLS_SSL_IN_CONTENT_LEN) can be set to lower value which is not possible without enabling this configuration.

Default value of mbedTLS Rx buffer size is set to 16K. By using partial_http_download with max_http_request_size of 4K, size of mbedTLS Rx buffer can be reduced to 4K. With this configuration, memory saving of around 12K is expected.

Signature Verification

For additional security, signature of OTA firmware images can be verified. For that, refer 没有安全启动的安全 OTA 升级

Advanced APIs

esp_https_ota also provides advanced APIs which can be used if more information and control is needed during the OTA process.

Example that uses advanced ESP_HTTPS_OTA APIs: system/ota/advanced_https_ota.

OTA Upgrades with Pre-Encrypted Firmware

To perform OTA upgrades with Pre-Encrypted Firmware, please enable CONFIG_ESP_HTTPS_OTA_DECRYPT_CB in component menuconfig.

Example that performs OTA upgrade with Pre-Encrypted Firmware: system/ota/pre_encrypted_ota.

API Reference

Header File

Functions

esp_err_t esp_https_ota(const esp_https_ota_config_t *ota_config)

HTTPS OTA Firmware upgrade.

This function allocates HTTPS OTA Firmware upgrade context, establishes HTTPS connection, reads image data from HTTP stream and writes it to OTA partition and finishes HTTPS OTA Firmware upgrade operation. This API supports URL redirection, but if CA cert of URLs differ then it should be appended to cert_pem member of ota_config->http_config.

备注

This API handles the entire OTA operation, so if this API is being used then no other APIs from esp_https_ota component should be called. If more information and control is needed during the HTTPS OTA process, then one can use esp_https_ota_begin and subsequent APIs. If this API returns successfully, esp_restart() must be called to boot from the new firmware image.

参数

ota_config[in] pointer to esp_https_ota_config_t structure.

返回

  • ESP_OK: OTA data updated, next reboot will use specified partition.

  • ESP_FAIL: For generic failure.

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_OTA_VALIDATE_FAILED: Invalid app image

  • ESP_ERR_NO_MEM: Cannot allocate memory for OTA operation.

  • ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash write failed.

  • For other return codes, refer OTA documentation in esp-idf’s app_update component.

esp_err_t esp_https_ota_begin(const esp_https_ota_config_t *ota_config, esp_https_ota_handle_t *handle)

Start HTTPS OTA Firmware upgrade.

This function initializes ESP HTTPS OTA context and establishes HTTPS connection. This function must be invoked first. If this function returns successfully, then esp_https_ota_perform should be called to continue with the OTA process and there should be a call to esp_https_ota_finish on completion of OTA operation or on failure in subsequent operations. This API supports URL redirection, but if CA cert of URLs differ then it should be appended to cert_pem member of http_config, which is a part of ota_config. In case of error, this API explicitly sets handle to NULL.

备注

This API is blocking, so setting is_async member of http_config structure will result in an error.

参数
  • ota_config[in] pointer to esp_https_ota_config_t structure

  • handle[out] pointer to an allocated data of type esp_https_ota_handle_t which will be initialised in this function

返回

  • ESP_OK: HTTPS OTA Firmware upgrade context initialised and HTTPS connection established

  • ESP_FAIL: For generic failure.

  • ESP_ERR_INVALID_ARG: Invalid argument (missing/incorrect config, certificate, etc.)

  • For other return codes, refer documentation in app_update component and esp_http_client component in esp-idf.

esp_err_t esp_https_ota_perform(esp_https_ota_handle_t https_ota_handle)

Read image data from HTTP stream and write it to OTA partition.

This function reads image data from HTTP stream and writes it to OTA partition. This function must be called only if esp_https_ota_begin() returns successfully. This function must be called in a loop since it returns after every HTTP read operation thus giving you the flexibility to stop OTA operation midway.

参数

https_ota_handle[in] pointer to esp_https_ota_handle_t structure

返回

  • ESP_ERR_HTTPS_OTA_IN_PROGRESS: OTA update is in progress, call this API again to continue.

  • ESP_OK: OTA update was successful

  • ESP_FAIL: OTA update failed

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_INVALID_VERSION: Invalid chip revision in image header

  • ESP_ERR_OTA_VALIDATE_FAILED: Invalid app image

  • ESP_ERR_NO_MEM: Cannot allocate memory for OTA operation.

  • ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash write failed.

  • For other return codes, refer OTA documentation in esp-idf’s app_update component.

bool esp_https_ota_is_complete_data_received(esp_https_ota_handle_t https_ota_handle)

Checks if complete data was received or not.

备注

This API can be called just before esp_https_ota_finish() to validate if the complete image was indeed received.

参数

https_ota_handle[in] pointer to esp_https_ota_handle_t structure

返回

  • false

  • true

esp_err_t esp_https_ota_finish(esp_https_ota_handle_t https_ota_handle)

Clean-up HTTPS OTA Firmware upgrade and close HTTPS connection.

This function closes the HTTP connection and frees the ESP HTTPS OTA context. This function switches the boot partition to the OTA partition containing the new firmware image.

备注

If this API returns successfully, esp_restart() must be called to boot from the new firmware image esp_https_ota_finish should not be called after calling esp_https_ota_abort

参数

https_ota_handle[in] pointer to esp_https_ota_handle_t structure

返回

  • ESP_OK: Clean-up successful

  • ESP_ERR_INVALID_STATE

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_OTA_VALIDATE_FAILED: Invalid app image

esp_err_t esp_https_ota_abort(esp_https_ota_handle_t https_ota_handle)

Clean-up HTTPS OTA Firmware upgrade and close HTTPS connection.

This function closes the HTTP connection and frees the ESP HTTPS OTA context.

备注

esp_https_ota_abort should not be called after calling esp_https_ota_finish

参数

https_ota_handle[in] pointer to esp_https_ota_handle_t structure

返回

  • ESP_OK: Clean-up successful

  • ESP_ERR_INVALID_STATE: Invalid ESP HTTPS OTA state

  • ESP_FAIL: OTA not started

  • ESP_ERR_NOT_FOUND: OTA handle not found

  • ESP_ERR_INVALID_ARG: Invalid argument

esp_err_t esp_https_ota_get_img_desc(esp_https_ota_handle_t https_ota_handle, esp_app_desc_t *new_app_info)

Reads app description from image header. The app description provides information like the “Firmware version” of the image.

备注

This API can be called only after esp_https_ota_begin() and before esp_https_ota_perform(). Calling this API is not mandatory.

参数
  • https_ota_handle[in] pointer to esp_https_ota_handle_t structure

  • new_app_info[out] pointer to an allocated esp_app_desc_t structure

返回

  • ESP_ERR_INVALID_ARG: Invalid arguments

  • ESP_ERR_INVALID_STATE: Invalid state to call this API. esp_https_ota_begin() not called yet.

  • ESP_FAIL: Failed to read image descriptor

  • ESP_OK: Successfully read image descriptor

int esp_https_ota_get_image_len_read(esp_https_ota_handle_t https_ota_handle)

This function returns OTA image data read so far.

备注

This API should be called only if esp_https_ota_perform() has been called atleast once or if esp_https_ota_get_img_desc has been called before.

参数

https_ota_handle[in] pointer to esp_https_ota_handle_t structure

返回

  • -1 On failure

  • total bytes read so far

int esp_https_ota_get_image_size(esp_https_ota_handle_t https_ota_handle)

This function returns OTA image total size.

备注

This API should be called after esp_https_ota_begin() has been already called. This can be used to create some sort of progress indication (in combination with esp_https_ota_get_image_len_read())

参数

https_ota_handle[in] pointer to esp_https_ota_handle_t structure

返回

  • -1 On failure or chunked encoding

  • total bytes of image

Structures

struct esp_https_ota_config_t

ESP HTTPS OTA configuration.

Public Members

const esp_http_client_config_t *http_config

ESP HTTP client configuration

http_client_init_cb_t http_client_init_cb

Callback after ESP HTTP client is initialised

bool bulk_flash_erase

Erase entire flash partition during initialization. By default flash partition is erased during write operation and in chunk of 4K sector size

bool partial_http_download

Enable Firmware image to be downloaded over multiple HTTP requests

int max_http_request_size

Maximum request size for partial HTTP download

Macros

ESP_ERR_HTTPS_OTA_BASE
ESP_ERR_HTTPS_OTA_IN_PROGRESS

Type Definitions

typedef void *esp_https_ota_handle_t
typedef esp_err_t (*http_client_init_cb_t)(esp_http_client_handle_t)

Enumerations

enum esp_https_ota_event_t

Events generated by OTA process.

备注

Expected data type for different OTA events:

  • ESP_HTTPS_OTA_START : NULL

  • ESP_HTTPS_OTA_CONNECTED : NULL

  • ESP_HTTPS_OTA_GET_IMG_DESC : NULL

  • ESP_HTTPS_OTA_VERIFY_CHIP_ID : esp_chip_id_t

  • ESP_HTTPS_OTA_DECRYPT_CB : NULL

  • ESP_HTTPS_OTA_WRITE_FLASH : int

  • ESP_HTTPS_OTA_UPDATE_BOOT_PARTITION : esp_partition_subtype_t

  • ESP_HTTPS_OTA_FINISH : NULL

  • ESP_HTTPS_OTA_ABORT : NULL

Values:

enumerator ESP_HTTPS_OTA_START

OTA started

enumerator ESP_HTTPS_OTA_CONNECTED

Connected to server

enumerator ESP_HTTPS_OTA_GET_IMG_DESC

Read app description from image header

enumerator ESP_HTTPS_OTA_VERIFY_CHIP_ID

Verify chip id of new image

enumerator ESP_HTTPS_OTA_DECRYPT_CB

Callback to decrypt function

enumerator ESP_HTTPS_OTA_WRITE_FLASH

Flash write operation

enumerator ESP_HTTPS_OTA_UPDATE_BOOT_PARTITION

Boot partition update after successful ota update

enumerator ESP_HTTPS_OTA_FINISH

OTA finished

enumerator ESP_HTTPS_OTA_ABORT

OTA aborted