app_update: Add API for getting sha256_of_partition

Added bootloader_common_get_sha256_of_partition() and esp_partition_get_sha256() - get or calculate SHA-256
digest for app and data partitions.
Added bootloader_sha256_hex_to_str() - helps to print SHA-256 digest
Added esp_partition_check_identity() - compares two partitions by SHA-256 digest

Refactoring a function esp_image_load() in bootloader space to esp_image_verify() and
bootloader_load_image(). Old name function esp_image_load is deprecated
and will remove in V4.0 version.

spi_flash/sim: Fix error test_host. Add stub for bootloader_common_get_sha256_of_partition in sim/stubs

components/bootloader_support/include/bootloader_common.h

@@ -68,3 +68,26 @@ bool bootloader_common_erase_part_type_data(const char *list_erase, bool ota_dat
  * @return    Returns true if the list contains the label, false otherwise.
  */
 bool bootloader_common_label_search(const char *list, char *label);
+
+/**
+ * @brief Calculates a sha-256 for a given partition or returns a appended digest.
+ *
+ * This function can be used to return the SHA-256 digest of application, bootloader and data partitions.
+ * For apps with SHA-256 appended to the app image, the result is the appended SHA-256 value for the app image content.
+ * The hash is verified before returning, if app content is invalid then the function returns ESP_ERR_IMAGE_INVALID.
+ * For apps without SHA-256 appended to the image, the result is the SHA-256 of all bytes in the app image.
+ * For other partition types, the result is the SHA-256 of the entire partition.
+ *
+ * @param[in]  address      Address of partition.
+ * @param[in]  size         Size of partition.
+ * @param[in]  type         Type of partition. For applications the type is 0, otherwise type is data.
+ * @param[out] out_sha_256  Returned SHA-256 digest for a given partition.
+ *
+ * @return
+ *          - ESP_OK: In case of successful operation.
+ *          - ESP_ERR_INVALID_ARG: The size was 0 or the sha_256 was NULL.
+ *          - ESP_ERR_NO_MEM: Cannot allocate memory for sha256 operation.
+ *          - ESP_ERR_IMAGE_INVALID: App partition doesn't contain a valid app image.
+ *          - ESP_FAIL: An allocation error occurred.
+ */
+esp_err_t bootloader_common_get_sha256_of_partition(uint32_t address, uint32_t size, int type, uint8_t *out_sha_256);

components/bootloader_support/include/esp_image_format.h

@@ -96,11 +96,12 @@ typedef struct {
   esp_image_segment_header_t segments[ESP_IMAGE_MAX_SEGMENTS]; /* Per-segment header data */
   uint32_t segment_data[ESP_IMAGE_MAX_SEGMENTS]; /* Data offsets for each segment */
   uint32_t image_len; /* Length of image on flash, in bytes */
+  uint8_t image_digest[32]; /* appended SHA-256 digest */
 } esp_image_metadata_t;
 
 /* Mode selection for esp_image_load() */
 typedef enum {
-    ESP_IMAGE_VERIFY,        /* Verify image contents, load metadata. Print errorsors. */
+    ESP_IMAGE_VERIFY,        /* Verify image contents, load metadata. Print errors. */
     ESP_IMAGE_VERIFY_SILENT, /* Verify image contents, load metadata. Don't print errors. */
 #ifdef BOOTLOADER_BUILD
     ESP_IMAGE_LOAD,          /* Verify image contents, load to memory. Print errors. */
@@ -110,6 +111,11 @@ typedef enum {
 /**
  * @brief Verify and (optionally, in bootloader mode) load an app image.
  *
+ * This name is deprecated and is included for compatibility with the ESP-IDF v3.x API.
+ * It will be removed in V4.0 version.
+ * Function has been renamed to esp_image_verify().
+ * Use function esp_image_verify() to verify a image. And use function bootloader_load_image() to load image from a bootloader space.
+ *
  * If encryption is enabled, data will be transparently decrypted.
  *
  * @param mode Mode of operation (verify, silent verify, or load).
@@ -130,7 +136,60 @@ typedef enum {
  * - ESP_ERR_IMAGE_INVALID if the image appears invalid.
  * - ESP_ERR_INVALID_ARG if the partition or data pointers are invalid.
  */
-esp_err_t esp_image_load(esp_image_load_mode_t mode, const esp_partition_pos_t *part, esp_image_metadata_t *data);
+esp_err_t esp_image_load(esp_image_load_mode_t mode, const esp_partition_pos_t *part, esp_image_metadata_t *data) __attribute__((deprecated));
+
+/**
+ * @brief Verify an app image.
+ *
+ * If encryption is enabled, data will be transparently decrypted.
+ *
+ * @param mode Mode of operation (verify, silent verify, or load).
+ * @param part Partition to load the app from.
+ * @param[inout] data Pointer to the image metadata structure which is be filled in by this function.
+ *                    'start_addr' member should be set (to the start address of the image.)
+ *                    Other fields will all be initialised by this function.
+ *
+ * Image validation checks:
+ * - Magic byte.
+ * - Partition smaller than 16MB.
+ * - All segments & image fit in partition.
+ * - 8 bit image checksum is valid.
+ * - SHA-256 of image is valid (if image has this appended).
+ * - (Signature) if signature verification is enabled.
+ *
+ * @return
+ * - ESP_OK if verify or load was successful
+ * - ESP_ERR_IMAGE_FLASH_FAIL if a SPI flash error occurs
+ * - ESP_ERR_IMAGE_INVALID if the image appears invalid.
+ * - ESP_ERR_INVALID_ARG if the partition or data pointers are invalid.
+ */
+esp_err_t esp_image_verify(esp_image_load_mode_t mode, const esp_partition_pos_t *part, esp_image_metadata_t *data);
+
+/**
+ * @brief Verify and load an app image (available only in space of bootloader).
+ *
+ * If encryption is enabled, data will be transparently decrypted.
+ *
+ * @param part Partition to load the app from.
+ * @param[inout] data Pointer to the image metadata structure which is be filled in by this function.
+ *                    'start_addr' member should be set (to the start address of the image.)
+ *                    Other fields will all be initialised by this function.
+ *
+ * Image validation checks:
+ * - Magic byte.
+ * - Partition smaller than 16MB.
+ * - All segments & image fit in partition.
+ * - 8 bit image checksum is valid.
+ * - SHA-256 of image is valid (if image has this appended).
+ * - (Signature) if signature verification is enabled.
+ *
+ * @return
+ * - ESP_OK if verify or load was successful
+ * - ESP_ERR_IMAGE_FLASH_FAIL if a SPI flash error occurs
+ * - ESP_ERR_IMAGE_INVALID if the image appears invalid.
+ * - ESP_ERR_INVALID_ARG if the partition or data pointers are invalid.
+ */
+esp_err_t bootloader_load_image(const esp_partition_pos_t *part, esp_image_metadata_t *data);
 
 /**
  * @brief Verify the bootloader image.