esp-idf/components/esp32c3/include/esp_ds.h

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// Copyright 2020 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 "esp_hmac.h"
#include "esp_err.h"
#ifdef __cplusplus
extern "C" {
#endif
#define ESP32C3_ERR_HW_CRYPTO_DS_HMAC_FAIL ESP_ERR_HW_CRYPTO_BASE + 0x1 /*!< HMAC peripheral problem */
#define ESP32C3_ERR_HW_CRYPTO_DS_INVALID_KEY ESP_ERR_HW_CRYPTO_BASE + 0x2 /*!< given HMAC key isn't correct,
HMAC peripheral problem */
#define ESP32C3_ERR_HW_CRYPTO_DS_INVALID_DIGEST ESP_ERR_HW_CRYPTO_BASE + 0x4 /*!< message digest check failed,
result is invalid */
#define ESP32C3_ERR_HW_CRYPTO_DS_INVALID_PADDING ESP_ERR_HW_CRYPTO_BASE + 0x5 /*!< padding check failed, but result
is produced anyway and can be read*/
#define ESP_DS_IV_BIT_LEN 128
#define ESP_DS_IV_LEN (ESP_DS_IV_BIT_LEN / 8)
#define ESP_DS_SIGNATURE_MAX_BIT_LEN 3072
#define ESP_DS_SIGNATURE_MD_BIT_LEN 256
#define ESP_DS_SIGNATURE_M_PRIME_BIT_LEN 32
#define ESP_DS_SIGNATURE_L_BIT_LEN 32
#define ESP_DS_SIGNATURE_PADDING_BIT_LEN 64
/* Length of parameter 'C' stored in flash, in bytes
- Operands Y, M and r_bar; each 3072 bits
- Operand MD (message digest); 256 bits
- Operands M' and L; each 32 bits
- Operand beta (padding value; 64 bits
*/
#define ESP_DS_C_LEN (((ESP_DS_SIGNATURE_MAX_BIT_LEN * 3 \
+ ESP_DS_SIGNATURE_MD_BIT_LEN \
+ ESP_DS_SIGNATURE_M_PRIME_BIT_LEN \
+ ESP_DS_SIGNATURE_L_BIT_LEN \
+ ESP_DS_SIGNATURE_PADDING_BIT_LEN) / 8))
typedef struct esp_ds_context esp_ds_context_t;
typedef enum {
ESP_DS_RSA_1024 = (1024 / 32) - 1,
ESP_DS_RSA_2048 = (2048 / 32) - 1,
ESP_DS_RSA_3072 = (3072 / 32) - 1
} esp_digital_signature_length_t;
/**
* Encrypted private key data. Recommended to store in flash in this format.
*
* @note This struct has to match to one from the ROM code! This documentation is mostly taken from there.
*/
typedef struct esp_digital_signature_data {
/**
* RSA LENGTH register parameters
* (number of words in RSA key & operands, minus one).
*
* Max value 127 (for RSA 3072).
*
* 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.)
*
* @note In IDF, the enum type length is the same as of type unsigned, so they can be used interchangably.
* See the ROM code for the original declaration of struct \c ets_ds_data_t.
*/
esp_digital_signature_length_t rsa_length;
/**
* IV value used to encrypt 'c'
*/
uint32_t iv[ESP_DS_IV_BIT_LEN / 32];
/**
* Encrypted Digital Signature parameters. Result of AES-CBC encryption
* of plaintext values. Includes an encrypted message digest.
*/
uint8_t c[ESP_DS_C_LEN];
} esp_ds_data_t;
/**
* Plaintext parameters used by Digital Signature.
*
* This is only used for encrypting the RSA parameters by calling esp_ds_encrypt_params().
* Afterwards, the result can be stored in flash or in other persistent memory.
* The encryption is a prerequisite step before any signature operation can be done.
*/
typedef struct {
uint32_t Y[ESP_DS_SIGNATURE_MAX_BIT_LEN / 32]; //!< RSA exponent
uint32_t M[ESP_DS_SIGNATURE_MAX_BIT_LEN / 32]; //!< RSA modulus
uint32_t Rb[ESP_DS_SIGNATURE_MAX_BIT_LEN / 32]; //!< RSA r inverse operand
uint32_t M_prime; //!< RSA M prime operand
uint32_t length; //!< RSA length in words (32 bit)
} esp_ds_p_data_t;
/**
* @brief Sign the message with a hardware key from specific key slot.
*
* This function is a wrapper around \c esp_ds_finish_sign() and \c esp_ds_start_sign(), so do not use them
* in parallel.
* It blocks until the signing is finished and then returns the signature.
*
* @note This function locks the HMAC, SHA, AES and RSA components during its entire execution time.
*
* @param message the message to be signed; its length is determined by data->rsa_length
* @param data the encrypted signing key data (AES encrypted RSA key + IV)
* @param key_id the HMAC key ID determining the HMAC key of the HMAC which will be used to decrypt the
* signing key data
* @param signature the destination of the signature, should be (data->rsa_length + 1)*4 bytes long
*
* @return
* - ESP_OK if successful, the signature was written to the parameter \c signature.
* - ESP_ERR_INVALID_ARG if one of the parameters is NULL or data->rsa_length is too long or 0
* - ESP_ERR_HW_CRYPTO_DS_HMAC_FAIL if there was an HMAC failure during retrieval of the decryption key
* - ESP_ERR_NO_MEM if there hasn't been enough memory to allocate the context object
* - ESP_ERR_HW_CRYPTO_DS_INVALID_KEY if there's a problem with passing the HMAC key to the DS component
* - ESP_ERR_HW_CRYPTO_DS_INVALID_DIGEST if the message digest didn't match; the signature is invalid.
* - ESP_ERR_HW_CRYPTO_DS_INVALID_PADDING if the message padding is incorrect, the signature can be read though
* since the message digest matches.
*/
esp_err_t esp_ds_sign(const void *message,
const esp_ds_data_t *data,
hmac_key_id_t key_id,
void *signature);
/**
* @brief Start the signing process.
*
* This function yields a context object which needs to be passed to \c esp_ds_finish_sign() to finish the signing
* process.
*
* @note This function locks the HMAC, SHA, AES and RSA components, so the user has to ensure to call
* \c esp_ds_finish_sign() in a timely manner.
*
* @param message the message to be signed; its length is determined by data->rsa_length
* @param data the encrypted signing key data (AES encrypted RSA key + IV)
* @param key_id the HMAC key ID determining the HMAC key of the HMAC which will be used to decrypt the
* signing key data
* @param esp_ds_ctx the context object which is needed for finishing the signing process later
*
* @return
* - ESP_OK if successful, the ds operation was started now and has to be finished with \c esp_ds_finish_sign()
* - ESP_ERR_INVALID_ARG if one of the parameters is NULL or data->rsa_length is too long or 0
* - ESP_ERR_HW_CRYPTO_DS_HMAC_FAIL if there was an HMAC failure during retrieval of the decryption key
* - ESP_ERR_NO_MEM if there hasn't been enough memory to allocate the context object
* - ESP_ERR_HW_CRYPTO_DS_INVALID_KEY if there's a problem with passing the HMAC key to the DS component
*/
esp_err_t esp_ds_start_sign(const void *message,
const esp_ds_data_t *data,
hmac_key_id_t key_id,
esp_ds_context_t **esp_ds_ctx);
/**
* Return true if the DS peripheral is busy, otherwise false.
*
* @note Only valid if \c esp_ds_start_sign() was called before.
*/
bool esp_ds_is_busy(void);
/**
* @brief Finish the signing process.
*
* @param signature the destination of the signature, should be (data->rsa_length + 1)*4 bytes long
* @param esp_ds_ctx the context object retreived by \c esp_ds_start_sign()
*
* @return
* - ESP_OK if successful, the ds operation has been finished and the result is written to signature.
* - ESP_ERR_INVALID_ARG if one of the parameters is NULL
* - ESP_ERR_HW_CRYPTO_DS_INVALID_DIGEST if the message digest didn't match; the signature is invalid.
* This means that the encrypted RSA key parameters are invalid, indicating that they may have been tampered
* with or indicating a flash error, etc.
* - ESP_ERR_HW_CRYPTO_DS_INVALID_PADDING if the message padding is incorrect, the signature can be read though
* since the message digest matches (see TRM for more details).
*/
esp_err_t esp_ds_finish_sign(void *signature, esp_ds_context_t *esp_ds_ctx);
/**
* @brief Encrypt the private key parameters.
*
* The encryption is a prerequisite step before any signature operation can be done.
* It is not strictly necessary to use this encryption function, the encryption could also happen on an external
* device.
*
* @param data Output buffer to store encrypted data, suitable for later use generating signatures.
* The allocated memory must be in internal memory and word aligned since it's filled by DMA. Both is asserted
* at run time.
* @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.
*
* @return
* - ESP_OK if successful, the ds operation has been finished and the result is written to signature.
* - ESP_ERR_INVALID_ARG if one of the parameters is NULL or p_data->rsa_length is too long
*/
esp_err_t esp_ds_encrypt_params(esp_ds_data_t *data,
const void *iv,
const esp_ds_p_data_t *p_data,
const void *key);
#ifdef __cplusplus
}
#endif