OVMS3-idf/components/bootloader_support/include/esp_secure_boot.h
Angus Gratton b069b31a2c secure boot: Support secure boot signatures without hardware secure boot
Allows OTA updates to be secured via signature checks, without requiring the overhead or complexity
of a full secure boot implementation.

Uses same signing mechanisms (build system and/or espsecure.py as Secure Boot).

Requires:
* [ ] More testing
* [ ] Documentation
2018-09-04 19:10:02 +08:00

115 lines
3.9 KiB
C

// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#pragma once
#include <stdbool.h>
#include <esp_err.h>
#include "soc/efuse_reg.h"
#include "sdkconfig.h"
#ifdef CONFIG_SECURE_BOOT_ENABLED
#if !defined(CONFIG_SECURE_SIGNED_ON_BOOT) || !defined(CONFIG_SECURE_SIGNED_ON_UPDATE) || !defined(CONFIG_SECURE_SIGNED_APPS)
#error "internal sdkconfig error, secure boot should always enable all signature options"
#endif
#endif
#ifdef __cplusplus
extern "C" {
#endif
/* Support functions for secure boot features.
Can be compiled as part of app or bootloader code.
*/
/** @brief Is secure boot currently enabled in hardware?
*
* Secure boot is enabled if the ABS_DONE_0 efuse is blown. This means
* that the ROM bootloader code will only boot a verified secure
* bootloader digest from now on.
*
* @return true if secure boot is enabled.
*/
static inline bool esp_secure_boot_enabled(void) {
return REG_READ(EFUSE_BLK0_RDATA6_REG) & EFUSE_RD_ABS_DONE_0;
}
/** @brief Enable secure boot if it is not already enabled.
*
* @important If this function succeeds, secure boot is permanently
* enabled on the chip via efuse.
*
* @important This function is intended to be called from bootloader code only.
*
* If secure boot is not yet enabled for bootloader, this will
* generate the secure boot digest and enable secure boot by blowing
* the EFUSE_RD_ABS_DONE_0 efuse.
*
* This function does not verify secure boot of the bootloader (the
* ROM bootloader does this.)
*
* Will fail if efuses have been part-burned in a way that indicates
* secure boot should not or could not be correctly enabled.
*
*
* @return ESP_ERR_INVALID_STATE if efuse state doesn't allow
* secure boot to be enabled cleanly. ESP_OK if secure boot
* is enabled on this chip from now on.
*/
esp_err_t esp_secure_boot_permanently_enable(void);
/** @brief Verify the secure boot signature (determinstic ECDSA w/ SHA256) appended to some binary data in flash.
*
* Public key is compiled into the calling program. See docs/security/secure-boot.rst for details.
*
* @param src_addr Starting offset of the data in flash.
* @param length Length of data in bytes. Signature is appended -after- length bytes.
*
* If flash encryption is enabled, the image will be transparently decrypted while being verified.
*
* @return ESP_OK if signature is valid, ESP_ERR_INVALID_STATE if
* signature fails, ESP_FAIL for other failures (ie can't read flash).
*/
esp_err_t esp_secure_boot_verify_signature(uint32_t src_addr, uint32_t length);
/** @brief Verify the secure boot signature block (deterministic ECDSA w/ SHA256) based on the SHA256 hash of some data.
*
* Similar to esp_secure_boot_verify_signature(), but can be used when the digest is precalculated.
* @param sig_block Pointer to signature block data
* @param image_digest Pointer to 32 byte buffer holding SHA-256 hash.
*
*/
/** @brief Secure boot verification block, on-flash data format. */
typedef struct {
uint32_t version;
uint8_t signature[64];
} esp_secure_boot_sig_block_t;
esp_err_t esp_secure_boot_verify_signature_block(const esp_secure_boot_sig_block_t *sig_block, const uint8_t *image_digest);
#define FLASH_OFFS_SECURE_BOOT_IV_DIGEST 0
/** @brief Secure boot IV+digest header */
typedef struct {
uint8_t iv[128];
uint8_t digest[64];
} esp_secure_boot_iv_digest_t;
#ifdef __cplusplus
}
#endif