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bootloader: Add fault injection resistance to Secure Boot bootloader verification

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Goal is that multiple faults would be required to bypass a boot-time signature check.

- Also strengthens some address range checks for safe app memory addresses
- Change pre-enable logic to also check the bootloader signature before enabling SBV2 on ESP32

Add some additional checks for invalid sections:

- Sections only partially in DRAM or IRAM are invalid
- If a section is in D/IRAM, allow the possibility only some is in D/IRAM
- Only pass sections that are entirely in the same type of RTC memory region
This commit is contained in:
Angus Gratton
2020-02-16 16:51:42 +11:00
committed by Mahavir Jain
parent 0dacff4df4
commit d40c69375c
21 changed files with 712 additions and 119 deletions
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48
components/bootloader_support/include/esp_secure_boot.h
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@@ -25,6 +25,8 @@
#include "esp32/rom/secure_boot.h"
#endif
typedef struct ets_secure_boot_signature ets_secure_boot_signature_t;
#ifdef CONFIG_SECURE_BOOT_V1_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"
@@ -149,6 +151,9 @@ esp_err_t esp_secure_boot_v2_permanently_enable(const esp_image_metadata_t *imag
*
* If flash encryption is enabled, the image will be transparently decrypted while being verified.
*
* @note This function doesn't have any fault injection resistance so should not be called
* during a secure boot itself (but can be called when verifying an update, etc.)
*
* @return ESP_OK if signature is valid, ESP_ERR_INVALID_STATE if
* signature fails, ESP_FAIL for other failures (ie can't read flash).
*/
@@ -160,22 +165,43 @@ typedef struct {
uint8_t signature[64];
} esp_secure_boot_sig_block_t;
/** @brief Verify the secure boot signature block.
*
* For ECDSA Scheme (Secure Boot V1) - Deterministic ECDSA w/ SHA256 based on the SHA256 hash of the image.
* For RSA Scheme (Secure Boot V2) - RSA-PSS Verification of the SHA-256 image based on the public key
* in the signature block.
/** @brief Verify the ECDSA secure boot signature block for Secure Boot V1.
*
* Calculates Deterministic ECDSA w/ SHA256 based on the SHA256 hash of the image. ECDSA signature
* verification must be enabled in project configuration to use this function.
*
* Similar to esp_secure_boot_verify_signature(), but can be used when the digest is precalculated.
* @param sig_block Pointer to RSA or ECDSA signature block data
* @param sig_block Pointer to ECDSA signature block data
* @param image_digest Pointer to 32 byte buffer holding SHA-256 hash.
* @param verified_digest Pointer to 32 byte buffer that will receive verified digest if verification completes. (Used during bootloader implementation only, result is invalid otherwise.)
*
*/
#ifdef CONFIG_SECURE_SIGNED_APPS_ECDSA_SCHEME
esp_err_t esp_secure_boot_verify_signature_block(const esp_secure_boot_sig_block_t *sig_block, const uint8_t *image_digest);
#elif CONFIG_SECURE_SIGNED_APPS_RSA_SCHEME
esp_err_t esp_secure_boot_verify_signature_block(const ets_secure_boot_signature_t *sig_block, const uint8_t *image_digest);
#endif
esp_err_t esp_secure_boot_verify_ecdsa_signature_block(const esp_secure_boot_sig_block_t *sig_block, const uint8_t *image_digest, uint8_t *verified_digest);
/** @brief Verify the RSA secure boot signature block for Secure Boot V2.
*
* Performs RSA-PSS Verification of the SHA-256 image based on the public key
* in the signature block, compared against the public key digest stored in efuse.
*
* Similar to esp_secure_boot_verify_signature(), but can be used when the digest is precalculated.
* @param sig_block Pointer to RSA signature block data
* @param image_digest Pointer to 32 byte buffer holding SHA-256 hash.
* @param verified_digest Pointer to 32 byte buffer that will receive verified digest if verification completes. (Used during bootloader implementation only, result is invalid otherwise.)
*
*/
esp_err_t esp_secure_boot_verify_rsa_signature_block(const ets_secure_boot_signature_t *sig_block, const uint8_t *image_digest, uint8_t *verified_digest);
/** @brief Legacy ECDSA verification function
*
* @note Deprecated, call either esp_secure_boot_verify_ecdsa_signature_block() or esp_secure_boot_verify_rsa_signature_block() instead.
*
* @param sig_block Pointer to ECDSA signature block data
* @param image_digest Pointer to 32 byte buffer holding SHA-256 hash.
*/
esp_err_t esp_secure_boot_verify_signature_block(const esp_secure_boot_sig_block_t *sig_block, const uint8_t *image_digest)
__attribute__((deprecated("use esp_secure_boot_verify_ecdsa_signature_block instead")));
#define FLASH_OFFS_SECURE_BOOT_IV_DIGEST 0