OVMS3-idf/components/esp_rom/include/esp32s2beta/rom/digital_signature.h

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2019-12-26 07:25:24 +00:00
/*
ROM functions for hardware Digital Signature peripheral verification
*/
// Copyright 2019 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
#ifdef __cplusplus
extern "C" {
#endif
#include <stdint.h>
#include <stdbool.h>
#define ETS_DS_IV_LEN 16
/* Length of parameter 'C' stored in flash */
#define ETS_DS_C_LEN (12672 / 8)
/* Encrypted ETS data. Recommended to store in flash in this format.
*/
typedef struct {
/* RSA LENGTH register parameters
* (number of words in RSA key & operands, minus one).
*
* Max value 127 (for RSA 4096).
*
* This value must match the length field encrypted and stored in 'c',
* or invalid results will be returned. (The DS peripheral will
* always use the value in 'c', not this value, so an attacker can't
* alter the DS peripheral results this way, it will just truncate or
* extend the message and the resulting signature in software.)
*/
unsigned rsa_length;
/* IV value used to encrypt 'c' */
uint8_t iv[ETS_DS_IV_LEN];
/* Encrypted Digital Signature parameters. Result of AES-CBC encryption
of plaintext values. Includes an encrypted message digest.
*/
uint8_t c[ETS_DS_C_LEN];
} ets_ds_data_t;
typedef enum {
ETS_DS_OK,
ETS_DS_INVALID_PARAM, /* Supplied parameters are invalid */
ETS_DS_INVALID_KEY, /* HMAC peripheral failed to supply key */
ETS_DS_INVALID_PADDING, /* 'c' decrypted with invalid padding */
ETS_DS_INVALID_DIGEST, /* 'c' decrypted with invalid digest */
} ets_ds_result_t;
void ets_ds_enable(void);
void ets_ds_disable(void);
/*
* @brief Start signing a message (or padded message digest) using the Digital Signature peripheral
*
* - @param message Pointer to message (or padded digest) containing the message to sign. Should be
* (data->rsa_length + 1)*4 bytes long. @param data Pointer to DS data. Can be a pointer to data
* in flash.
*
* Caller must have already called ets_ds_enable() and ets_hmac_calculate_downstream() before calling
* this function, and is responsible for calling ets_ds_finish_sign() and then
* ets_hmac_invalidate_downstream() afterwards.
*
* @return ETS_DS_OK if signature is in progress, ETS_DS_INVALID_PARAM if param is invalid,
* EST_DS_INVALID_KEY if key or HMAC peripheral is configured incorrectly.
*/
ets_ds_result_t ets_ds_start_sign(const void *message, const ets_ds_data_t *data);
/*
* @brief Returns true if the DS peripheral is busy following a call to ets_ds_start_sign()
*
* A result of false indicates that a call to ets_ds_finish_sign() will not block.
*
* Only valid if ets_ds_enable() has been called.
*/
bool ets_ds_is_busy(void);
/* @brief Finish signing a message using the Digital Signature peripheral
*
* Must be called after ets_ds_start_sign(). Can use ets_ds_busy() to wait until
* peripheral is no longer busy.
*
* - @param signature Pointer to buffer to contain the signature. Should be
* (data->rsa_length + 1)*4 bytes long.
* - @param data Should match the 'data' parameter passed to ets_ds_start_sign()
*
* @param ETS_DS_OK if signing succeeded, ETS_DS_INVALID_PARAM if param is invalid,
* ETS_DS_INVALID_DIGEST or ETS_DS_INVALID_PADDING if there is a problem with the
* encrypted data digest or padding bytes (in case of ETS_DS_INVALID_PADDING, a
* digest is produced anyhow.)
*/
ets_ds_result_t ets_ds_finish_sign(void *signature, const ets_ds_data_t *data);
/* Plaintext parameters used by Digital Signature.
Not used for signing with DS peripheral, but can be encrypted
in-device by calling ets_ds_encrypt_params()
*/
typedef struct {
uint32_t Y[4096/32];
uint32_t M[4096/32];
uint32_t Rb[4096/32];
uint32_t M_prime;
uint32_t length;
} ets_ds_p_data_t;
typedef enum {
ETS_DS_KEY_HMAC, /* The HMAC key (as stored in efuse) */
ETS_DS_KEY_AES, /* The AES key (as derived from HMAC key by HMAC peripheral in downstream mode) */
} ets_ds_key_t;
/* @brief Encrypt DS parameters suitable for storing and later use with DS peripheral
*
* @param data Output buffer to store encrypted data, suitable for later use generating signatures.
* @param iv Pointer to 16 byte IV buffer, will be copied into 'data'. Should be randomly generated bytes each time.
* @param p_data Pointer to input plaintext key data. The expectation is this data will be deleted after this process is done and 'data' is stored.
* @param key Pointer to 32 bytes of key data. Type determined by key_type parameter. The expectation is the corresponding HMAC key will be stored to efuse and then permanently erased.
* @param key_type Type of key stored in 'key' (either the AES-256 DS key, or an HMAC DS key from which the AES DS key is derived using HMAC peripheral)
*
* @return ETS_DS_INVALID_PARAM if any parameter is invalid, or ETS_DS_OK if 'data' is successfully generated from the input parameters.
*/
ets_ds_result_t ets_ds_encrypt_params(ets_ds_data_t *data, const void *iv, const ets_ds_p_data_t *p_data, const void *key, ets_ds_key_t key_type);
#ifdef __cplusplus
}
#endif