2021-06-10 02:22:35 +00:00
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// Copyright 2015-2020 Espressif Systems (Shanghai) PTE LTD
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include <string.h>
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#include "driver/periph_ctrl.h"
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2021-06-10 02:28:23 +00:00
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#include "esp32h2/rom/hmac.h"
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#include "esp32h2/rom/ets_sys.h"
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2021-06-10 02:22:35 +00:00
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#include "esp_hmac.h"
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#include "esp_crypto_lock.h"
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#include "hal/hmac_hal.h"
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#define SHA256_BLOCK_SZ 64
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#define SHA256_PAD_SZ 8
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/**
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* @brief Apply the HMAC padding without the embedded length.
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*
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* @note This function does not check the data length, it is the responsibility of the other functions in this
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* module to make sure that \c data_len is at most SHA256_BLOCK_SZ - 1 so the padding fits in.
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* Otherwise, this function has undefined behavior.
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2021-06-10 02:28:23 +00:00
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* Note however, that for the actual HMAC implementation on ESP32H2, the length also needs to be applied at the end
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2021-06-10 02:22:35 +00:00
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* of the block. This function alone deosn't do that.
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*/
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static void write_and_padd(uint8_t *block, const uint8_t *data, uint16_t data_len)
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{
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memcpy(block, data, data_len);
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2021-06-10 02:28:23 +00:00
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// Apply a one bit, followed by zero bits (refer to the ESP32H2 TRM).
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2021-06-10 02:22:35 +00:00
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block[data_len] = 0x80;
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bzero(block + data_len + 1, SHA256_BLOCK_SZ - data_len - 1);
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}
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esp_err_t esp_hmac_calculate(hmac_key_id_t key_id,
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const void *message,
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size_t message_len,
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uint8_t *hmac)
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{
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const uint8_t *message_bytes = (const uint8_t *)message;
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if (!message || !hmac) {
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return ESP_ERR_INVALID_ARG;
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}
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if (key_id >= HMAC_KEY_MAX) {
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return ESP_ERR_INVALID_ARG;
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}
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esp_crypto_hmac_lock_acquire();
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// We also enable SHA and DS here. SHA is used by HMAC, DS will otherwise hold SHA in reset state.
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periph_module_enable(PERIPH_HMAC_MODULE);
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periph_module_enable(PERIPH_SHA_MODULE);
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periph_module_enable(PERIPH_DS_MODULE);
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hmac_hal_start();
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uint32_t conf_error = hmac_hal_configure(HMAC_OUTPUT_USER, key_id);
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if (conf_error) {
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esp_crypto_hmac_lock_release();
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return ESP_FAIL;
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}
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if (message_len + 1 + SHA256_PAD_SZ <= SHA256_BLOCK_SZ) {
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// If message including padding is only one block...
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// Last message block, so apply SHA-256 padding rules in software
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uint8_t block[SHA256_BLOCK_SZ];
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uint64_t bit_len = __builtin_bswap64(message_len * 8 + 512);
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write_and_padd(block, message_bytes, message_len);
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// Final block: append the bit length in this block and signal padding to peripheral
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memcpy(block + SHA256_BLOCK_SZ - sizeof(bit_len),
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&bit_len, sizeof(bit_len));
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hmac_hal_write_one_block_512(block);
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} else {
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// If message including padding is needs more than one block
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// write all blocks without padding except the last one
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size_t remaining_blocks = message_len / SHA256_BLOCK_SZ;
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for (int i = 1; i < remaining_blocks; i++) {
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hmac_hal_write_block_512(message_bytes);
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message_bytes += SHA256_BLOCK_SZ;
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hmac_hal_next_block_normal();
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}
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// If message fits into one block but without padding, we must not write another block.
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if (remaining_blocks) {
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hmac_hal_write_block_512(message_bytes);
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message_bytes += SHA256_BLOCK_SZ;
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}
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size_t remaining = message_len % SHA256_BLOCK_SZ;
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// Last message block, so apply SHA-256 padding rules in software
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uint8_t block[SHA256_BLOCK_SZ];
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uint64_t bit_len = __builtin_bswap64(message_len * 8 + 512);
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// If the remaining message and appended padding doesn't fit into a single block, we have to write an
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// extra block with the rest of the message and potential padding first.
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if (remaining >= SHA256_BLOCK_SZ - SHA256_PAD_SZ) {
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write_and_padd(block, message_bytes, remaining);
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hmac_hal_next_block_normal();
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hmac_hal_write_block_512(block);
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bzero(block, SHA256_BLOCK_SZ);
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} else {
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write_and_padd(block, message_bytes, remaining);
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}
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memcpy(block + SHA256_BLOCK_SZ - sizeof(bit_len),
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&bit_len, sizeof(bit_len));
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hmac_hal_next_block_padding();
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hmac_hal_write_block_512(block);
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}
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// Read back result (bit swapped)
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hmac_hal_read_result_256(hmac);
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periph_module_disable(PERIPH_DS_MODULE);
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periph_module_disable(PERIPH_SHA_MODULE);
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periph_module_disable(PERIPH_HMAC_MODULE);
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esp_crypto_hmac_lock_release();
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return ESP_OK;
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}
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