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_err_t ret = esp_https_ota(&config);
    if (ret == ESP_OK) {
        esp_restart();
    } else {
        return ESP_FAIL;
    }
    return ESP_OK;
}

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 confiuration, memory saving of around 12K is expected.

Signature Verification

For additional security, signature of OTA firmware images can be verified. For that, refer Secure OTA Updates Without Secure boot

API Reference

Functions

esp_err_t esp_https_ota(const esp_http_client_config_t *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 config.

Note

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.

Parameters

config – [in] pointer to esp_http_client_config_t structure.

Returns

  • 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(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.

Note

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

Parameters

  • 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

Returns

  • 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.

Parameters

https_ota_handle – [in] pointer to esp_https_ota_handle_t structure

Returns

  • 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_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.

Note

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

Parameters

https_ota_handle – [in] pointer to esp_https_ota_handle_t structure

Returns

  • 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.

Note

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

Parameters

https_ota_handle – [in] pointer to esp_https_ota_handle_t structure

Returns

  • 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.

Note

esp_https_ota_abort should not be called after calling esp_https_ota_finish

Parameters

https_ota_handle – [in] pointer to esp_https_ota_handle_t structure

Returns

  • 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.

Note

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

Parameters

  • 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

Returns

  • ESP_ERR_INVALID_ARG: Invalid arguments

  • 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.

Note

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.

Parameters

https_ota_handle – [in] pointer to esp_https_ota_handle_t structure

Returns

  • -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.

Note

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())

Parameters

https_ota_handle – [in] pointer to esp_https_ota_handle_t structure

Returns

  • -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)

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