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597 lines
17 KiB
C
597 lines
17 KiB
C
/**
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* \brief Multi-precision integer library, ESP32C hardware accelerated parts
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*
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* based on mbedTLS implementation
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*
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* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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* Additions Copyright (C) 2016, Espressif Systems (Shanghai) PTE Ltd
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* 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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*
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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, WITHOUT
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* 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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*
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*/
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#include <stdio.h>
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#include <string.h>
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#include <malloc.h>
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#include <limits.h>
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#include <assert.h>
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#include <stdlib.h>
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#include <sys/param.h>
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#include "mbedtls/bignum.h"
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#include "esp32s2beta/rom/bigint.h"
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#include "soc/hwcrypto_reg.h"
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#include "esp_system.h"
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#include "esp_log.h"
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#include "esp_intr.h"
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#include "esp_intr_alloc.h"
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#include "esp_attr.h"
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#include "soc/dport_reg.h"
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#include "soc/periph_defs.h"
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#include "freertos/FreeRTOS.h"
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#include "freertos/task.h"
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#include "freertos/semphr.h"
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static const __attribute__((unused)) char *TAG = "bignum";
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#define ciL (sizeof(mbedtls_mpi_uint)) /* chars in limb */
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#define biL (ciL << 3) /* bits in limb */
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static _lock_t mpi_lock;
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void esp_mpi_acquire_hardware( void )
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{
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/* newlib locks lazy initialize on ESP-IDF */
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_lock_acquire(&mpi_lock);
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DPORT_REG_SET_BIT(DPORT_PERIP_CLK_EN1_REG, DPORT_CRYPTO_RSA_CLK_EN);
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/* also clear reset on digital signature, otherwise RSA is held in reset */
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DPORT_REG_CLR_BIT(DPORT_PERIP_RST_EN1_REG, DPORT_CRYPTO_RSA_RST
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| DPORT_CRYPTO_DS_RST);
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DPORT_REG_CLR_BIT(DPORT_RSA_PD_CTRL_REG, DPORT_RSA_MEM_PD);
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while (DPORT_REG_READ(RSA_QUERY_CLEAN_REG) != 1) {
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}
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// Note: from enabling RSA clock to here takes about 1.3us
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}
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void esp_mpi_release_hardware( void )
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{
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DPORT_REG_SET_BIT(DPORT_RSA_PD_CTRL_REG, DPORT_RSA_PD);
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/* don't reset digital signature unit, as this resets AES also */
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DPORT_REG_SET_BIT(DPORT_PERIP_RST_EN1_REG, DPORT_CRYPTO_RSA_RST);
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DPORT_REG_CLR_BIT(DPORT_PERIP_CLK_EN1_REG, DPORT_CRYPTO_RSA_CLK_EN);
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_lock_release(&mpi_lock);
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}
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/* Convert bit count to word count
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*/
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static inline size_t bits_to_words(size_t bits)
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{
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return (bits + 31) / 32;
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}
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/* Return the number of words actually used to represent an mpi
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number.
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*/
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static size_t mpi_words(const mbedtls_mpi *mpi)
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{
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for (size_t i = mpi->n; i > 0; i--) {
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if (mpi->p[i - 1] != 0) {
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return i;
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}
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}
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return 0;
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}
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/* Copy mbedTLS MPI bignum 'mpi' to hardware memory block at 'mem_base'.
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If num_words is higher than the number of words in the bignum then
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these additional words will be zeroed in the memory buffer.
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*/
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static inline void mpi_to_mem_block(uint32_t mem_base, const mbedtls_mpi *mpi, size_t num_words)
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{
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uint32_t *pbase = (uint32_t *)mem_base;
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uint32_t copy_words = num_words < mpi->n ? num_words : mpi->n;
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/* Copy MPI data to memory block registers */
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for (int i = 0; i < copy_words; i++) {
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pbase[i] = mpi->p[i];
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}
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/* Zero any remaining memory block data */
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for (int i = copy_words; i < num_words; i++) {
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pbase[i] = 0;
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}
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/* Note: not executing memw here, can do it before we start a bignum operation */
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}
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/* Read mbedTLS MPI bignum back from hardware memory block.
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Reads num_words words from block.
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Can return a failure result if fails to grow the MPI result.
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*/
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static inline int mem_block_to_mpi(mbedtls_mpi *x, uint32_t mem_base, int num_words)
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{
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int ret = 0;
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MBEDTLS_MPI_CHK( mbedtls_mpi_grow(x, num_words) );
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/* Copy data from memory block registers */
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esp_dport_access_read_buffer(x->p, mem_base, num_words);
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/* Zero any remaining limbs in the bignum, if the buffer is bigger
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than num_words */
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for (size_t i = num_words; i < x->n; i++) {
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x->p[i] = 0;
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}
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asm volatile ("memw");
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cleanup:
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return ret;
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}
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/**
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*
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* There is a need for the value of integer N' such that B^-1(B-1)-N^-1N'=1,
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* where B^-1(B-1) mod N=1. Actually, only the least significant part of
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* N' is needed, hence the definition N0'=N' mod b. We reproduce below the
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* simple algorithm from an article by Dusse and Kaliski to efficiently
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* find N0' from N0 and b
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*/
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static mbedtls_mpi_uint modular_inverse(const mbedtls_mpi *M)
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{
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int i;
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uint64_t t = 1;
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uint64_t two_2_i_minus_1 = 2; /* 2^(i-1) */
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uint64_t two_2_i = 4; /* 2^i */
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uint64_t N = M->p[0];
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for (i = 2; i <= 32; i++) {
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if ((mbedtls_mpi_uint) N * t % two_2_i >= two_2_i_minus_1) {
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t += two_2_i_minus_1;
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}
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two_2_i_minus_1 <<= 1;
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two_2_i <<= 1;
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}
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return (mbedtls_mpi_uint)(UINT32_MAX - t + 1);
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}
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/* Calculate Rinv = RR^2 mod M, where:
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*
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* R = b^n where b = 2^32, n=num_words,
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* R = 2^N (where N=num_bits)
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* RR = R^2 = 2^(2*N) (where N=num_bits=num_words*32)
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*
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* This calculation is computationally expensive (mbedtls_mpi_mod_mpi)
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* so caller should cache the result where possible.
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*
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* DO NOT call this function while holding esp_mpi_acquire_hardware().
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*
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*/
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static int calculate_rinv(mbedtls_mpi *Rinv, const mbedtls_mpi *M, int num_words)
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{
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int ret;
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size_t num_bits = num_words * 32;
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mbedtls_mpi RR;
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mbedtls_mpi_init(&RR);
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MBEDTLS_MPI_CHK(mbedtls_mpi_set_bit(&RR, num_bits * 2, 1));
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MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(Rinv, &RR, M));
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cleanup:
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mbedtls_mpi_free(&RR);
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return ret;
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}
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/* Begin an RSA operation. op_reg specifies which 'START' register
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to write to.
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*/
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static inline void start_op(uint32_t op_reg)
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{
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/* Clear interrupt status */
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DPORT_REG_WRITE(RSA_CLEAR_INTERRUPT_REG, 1);
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DPORT_REG_WRITE(RSA_INTERRUPT_REG, 1);
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/* Note: above REG_WRITE includes a memw, so we know any writes
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to the memory blocks are also complete. */
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DPORT_REG_WRITE(op_reg, 1);
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}
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/* Wait for an RSA operation to complete.
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*/
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static inline void wait_op_complete(uint32_t op_reg)
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{
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while(DPORT_REG_READ(RSA_QUERY_INTERRUPT_REG) != 1)
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{ }
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/* clear the interrupt */
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DPORT_REG_WRITE(RSA_CLEAR_INTERRUPT_REG, 1);
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}
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/* Z = (X * Y) mod M
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Not an mbedTLS function
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*/
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int esp_mpi_mul_mpi_mod(mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi *Y, const mbedtls_mpi *M)
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{
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int ret;
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size_t y_bits = mbedtls_mpi_bitlen(Y);
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size_t x_words = mpi_words(X);
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size_t y_words = mpi_words(Y);
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size_t m_words = mpi_words(M);
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mbedtls_mpi Rinv;
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mbedtls_mpi_uint Mprime;
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size_t num_words = MAX(MAX(m_words, x_words), y_words);
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if (num_words * 32 > 4096) {
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return MBEDTLS_ERR_MPI_NOT_ACCEPTABLE;
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}
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/* Calculate and load the first stage montgomery multiplication */
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mbedtls_mpi_init(&Rinv);
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MBEDTLS_MPI_CHK(calculate_rinv(&Rinv, M, num_words));
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Mprime = modular_inverse(M);
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esp_mpi_acquire_hardware();
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DPORT_REG_WRITE(RSA_LENGTH_REG, (num_words-1));
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DPORT_REG_WRITE(RSA_M_DASH_REG, (uint32_t)Mprime);
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/* Load M, X, Rinv, Mprime (Mprime is mod 2^32) */
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mpi_to_mem_block(RSA_MEM_M_BLOCK_BASE, M, num_words);
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mpi_to_mem_block(RSA_MEM_RB_BLOCK_BASE, &Rinv, num_words);
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mpi_to_mem_block(RSA_MEM_X_BLOCK_BASE, X, num_words);
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mpi_to_mem_block(RSA_MEM_Y_BLOCK_BASE, Y, num_words);
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/* Enable acceleration options */
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DPORT_REG_WRITE(RSA_CONSTANT_TIME_REG, 0);
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DPORT_REG_WRITE(RSA_SEARCH_OPEN_REG, 1);
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DPORT_REG_WRITE(RSA_SEARCH_POS_REG, y_bits - 1);
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/* Execute first stage montgomery multiplication */
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start_op(RSA_MOD_MULT_START_REG);
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wait_op_complete(RSA_MOD_MULT_START_REG);
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DPORT_REG_WRITE(RSA_SEARCH_OPEN_REG, 1);
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mem_block_to_mpi(Z, RSA_MEM_Z_BLOCK_BASE, m_words);
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esp_mpi_release_hardware();
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cleanup:
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mbedtls_mpi_free(&Rinv);
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return ret;
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}
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#if defined(MBEDTLS_MPI_EXP_MOD_ALT)
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/*
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* Sliding-window exponentiation: Z = X^Y mod M (HAC 14.85)
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*
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* _Rinv is optional pre-calculated version of Rinv (via calculate_rinv()).
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*
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* (See RSA Accelerator section in Technical Reference for more about Mprime, Rinv)
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*
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*/
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int mbedtls_mpi_exp_mod( mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi *Y, const mbedtls_mpi *M, mbedtls_mpi *_Rinv )
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{
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int ret = 0;
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size_t y_bits = mbedtls_mpi_bitlen(Y);
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size_t x_words = mpi_words(X);
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size_t y_words = mpi_words(Y);
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size_t m_words = mpi_words(M);
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size_t num_words;
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mbedtls_mpi Rinv_new; /* used if _Rinv == NULL */
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mbedtls_mpi *Rinv; /* points to _Rinv (if not NULL) othwerwise &RR_new */
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mbedtls_mpi_uint Mprime;
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/* "all numbers must be the same length", so choose longest number
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as cardinal length of operation...
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*/
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num_words = MAX(m_words, MAX(x_words, y_words));
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if (mbedtls_mpi_cmp_int(M, 0) <= 0 || (M->p[0] & 1) == 0) {
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return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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}
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if (mbedtls_mpi_cmp_int(Y, 0) < 0) {
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return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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}
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if (mbedtls_mpi_cmp_int(Y, 0) == 0) {
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return mbedtls_mpi_lset(Z, 1);
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}
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if (num_words * 32 > 4096) {
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return MBEDTLS_ERR_MPI_NOT_ACCEPTABLE;
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}
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/* Determine RR pointer, either _RR for cached value
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or local RR_new */
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if (_Rinv == NULL) {
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mbedtls_mpi_init(&Rinv_new);
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Rinv = &Rinv_new;
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} else {
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Rinv = _Rinv;
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}
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if (Rinv->p == NULL) {
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MBEDTLS_MPI_CHK(calculate_rinv(Rinv, M, num_words));
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}
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Mprime = modular_inverse(M);
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esp_mpi_acquire_hardware();
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DPORT_REG_WRITE(RSA_LENGTH_REG, num_words - 1);
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/* Load M, X, Rinv, M-prime (M-prime is mod 2^32) */
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mpi_to_mem_block(RSA_MEM_X_BLOCK_BASE, X, num_words);
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mpi_to_mem_block(RSA_MEM_Y_BLOCK_BASE, Y, num_words);
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mpi_to_mem_block(RSA_MEM_M_BLOCK_BASE, M, num_words);
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mpi_to_mem_block(RSA_MEM_RB_BLOCK_BASE, Rinv, num_words);
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DPORT_REG_WRITE(RSA_M_DASH_REG, Mprime);
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/* Enable acceleration options */
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DPORT_REG_WRITE(RSA_CONSTANT_TIME_REG, 0);
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DPORT_REG_WRITE(RSA_SEARCH_OPEN_REG, 1);
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DPORT_REG_WRITE(RSA_SEARCH_POS_REG, y_bits - 1);
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start_op(RSA_MODEXP_START_REG);
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wait_op_complete(RSA_MODEXP_START_REG);
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DPORT_REG_WRITE(RSA_SEARCH_OPEN_REG, 0);
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ret = mem_block_to_mpi(Z, RSA_MEM_Z_BLOCK_BASE, m_words);
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esp_mpi_release_hardware();
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// Compensate for negative X
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if (X->s == -1 && (Y->p[0] & 1) != 0) {
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Z->s = -1;
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MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(Z, M, Z));
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} else {
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Z->s = 1;
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}
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cleanup:
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if (_Rinv == NULL) {
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mbedtls_mpi_free(&Rinv_new);
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}
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return ret;
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}
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#endif /* MBEDTLS_MPI_EXP_MOD_ALT */
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#if defined(MBEDTLS_MPI_MUL_MPI_ALT) /* MBEDTLS_MPI_MUL_MPI_ALT */
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static int mpi_mult_mpi_failover_mod_mult(mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi *Y, size_t z_words);
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static int mpi_mult_mpi_overlong(mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi *Y, size_t y_words, size_t z_words);
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/* Z = X * Y */
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int mbedtls_mpi_mul_mpi( mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi *Y )
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{
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int ret = 0;
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size_t x_bits = mbedtls_mpi_bitlen(X);
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size_t y_bits = mbedtls_mpi_bitlen(Y);
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size_t x_words = bits_to_words(x_bits);
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size_t y_words = bits_to_words(y_bits);
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size_t num_words = MAX(x_words, y_words);
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size_t z_words = x_words + y_words;
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/* Short-circuit eval if either argument is 0 or 1.
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This is needed as the mpi modular division
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argument will sometimes call in here when one
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argument is too large for the hardware unit, but the other
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argument is zero or one.
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This leaks some timing information, although overall there is a
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lot less timing variation than a software MPI approach.
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*/
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if (x_bits == 0 || y_bits== 0) {
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mbedtls_mpi_lset(Z, 0);
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return 0;
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}
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if (x_bits == 1) {
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ret = mbedtls_mpi_copy(Z, Y);
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Z->s *= X->s;
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return ret;
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}
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if (y_bits == 1) {
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ret = mbedtls_mpi_copy(Z, X);
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Z->s *= Y->s;
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return ret;
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}
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/* If either factor is over 2048 bits, we can't use the standard hardware multiplier
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(it assumes result is double longest factor, and result is max 4096 bits.)
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However, we can fail over to mod_mult for up to 4096 bits of result (modulo
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multiplication doesn't have the same restriction, so result is simply the
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number of bits in X plus number of bits in in Y.)
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*/
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if (num_words * 32 > 2048) {
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if (z_words * 32 <= 4096) {
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/* Note: it's possible to use mpi_mult_mpi_overlong
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for this case as well, but it's very slightly
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slower and requires a memory allocation.
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*/
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return mpi_mult_mpi_failover_mod_mult(Z, X, Y, z_words);
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} else {
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/* Still too long for the hardware unit... */
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mbedtls_mpi_grow(Z, z_words);
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if(y_words > x_words) {
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return mpi_mult_mpi_overlong(Z, X, Y, y_words, z_words);
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} else {
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return mpi_mult_mpi_overlong(Z, Y, X, x_words, z_words);
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}
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}
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}
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/* Otherwise, we can use the (faster) multiply hardware unit */
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esp_mpi_acquire_hardware();
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/* Copy X (right-extended) & Y (left-extended) to memory block */
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mpi_to_mem_block(RSA_MEM_X_BLOCK_BASE, X, num_words);
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mpi_to_mem_block(RSA_MEM_Z_BLOCK_BASE + num_words * 4, Y, num_words);
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/* NB: as Y is left-extended, we don't zero the bottom words_mult words of Y block.
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This is OK for now because zeroing is done by hardware when we do esp_mpi_acquire_hardware().
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*/
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DPORT_REG_WRITE(RSA_M_DASH_REG, 0);
|
|
DPORT_REG_WRITE(RSA_LENGTH_REG, (num_words*2 - 1));
|
|
start_op(RSA_MULT_START_REG);
|
|
|
|
wait_op_complete(RSA_MULT_START_REG);
|
|
|
|
/* Read back the result */
|
|
ret = mem_block_to_mpi(Z, RSA_MEM_Z_BLOCK_BASE, z_words);
|
|
|
|
Z->s = X->s * Y->s;
|
|
|
|
esp_mpi_release_hardware();
|
|
|
|
return ret;
|
|
}
|
|
|
|
/* Special-case of mbedtls_mpi_mult_mpi(), where we use hardware montgomery mod
|
|
multiplication to calculate an mbedtls_mpi_mult_mpi result where either
|
|
A or B are >2048 bits so can't use the standard multiplication method.
|
|
|
|
Result (number of words, based on A bits + B bits) must still be less than 4096 bits.
|
|
|
|
This case is simpler than the general case modulo multiply of
|
|
esp_mpi_mul_mpi_mod() because we can control the other arguments:
|
|
|
|
* Modulus is chosen with M=(2^num_bits - 1) (ie M=R-1), so output
|
|
isn't actually modulo anything.
|
|
* Mprime and Rinv are therefore predictable as follows:
|
|
Mprime = 1
|
|
Rinv = 1
|
|
|
|
(See RSA Accelerator section in Technical Reference for more about Mprime, Rinv)
|
|
*/
|
|
static int mpi_mult_mpi_failover_mod_mult(mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi *Y, size_t num_words)
|
|
{
|
|
int ret = 0;
|
|
|
|
/* Load coefficients to hardware */
|
|
esp_mpi_acquire_hardware();
|
|
|
|
/* M = 2^num_words - 1, so block is entirely FF */
|
|
for (int i = 0; i < num_words; i++) {
|
|
DPORT_REG_WRITE(RSA_MEM_M_BLOCK_BASE + i * 4, UINT32_MAX);
|
|
}
|
|
|
|
/* Mprime = 1 */
|
|
DPORT_REG_WRITE(RSA_M_DASH_REG, 1);
|
|
DPORT_REG_WRITE(RSA_LENGTH_REG, num_words - 1);
|
|
|
|
/* Load X & Y */
|
|
mpi_to_mem_block(RSA_MEM_X_BLOCK_BASE, X, num_words);
|
|
mpi_to_mem_block(RSA_MEM_Y_BLOCK_BASE, Y, num_words);
|
|
|
|
/* Rinv = 1 */
|
|
DPORT_REG_WRITE(RSA_MEM_RB_BLOCK_BASE, 1);
|
|
for (int i = 1; i < num_words; i++) {
|
|
DPORT_REG_WRITE(RSA_MEM_RB_BLOCK_BASE + i * 4, 0);
|
|
}
|
|
|
|
start_op(RSA_MOD_MULT_START_REG);
|
|
wait_op_complete(RSA_MOD_MULT_START_REG);
|
|
|
|
mem_block_to_mpi(Z, RSA_MEM_Z_BLOCK_BASE, num_words);
|
|
|
|
esp_mpi_release_hardware();
|
|
|
|
return ret;
|
|
}
|
|
|
|
/* Deal with the case when X & Y are too long for the hardware unit, by splitting one operand
|
|
into two halves.
|
|
|
|
Y must be the longer operand
|
|
|
|
Slice Y into Yp, Ypp such that:
|
|
Yp = lower 'b' bits of Y
|
|
Ypp = upper 'b' bits of Y (right shifted)
|
|
|
|
Such that
|
|
Z = X * Y
|
|
Z = X * (Yp + Ypp<<b)
|
|
Z = (X * Yp) + (X * Ypp<<b)
|
|
|
|
Note that this function may recurse multiple times, if both X & Y
|
|
are too long for the hardware multiplication unit.
|
|
*/
|
|
static int mpi_mult_mpi_overlong(mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi *Y, size_t y_words, size_t z_words)
|
|
{
|
|
int ret = 0;
|
|
mbedtls_mpi Ztemp;
|
|
/* Rather than slicing in two on bits we slice on limbs (32 bit words) */
|
|
const size_t words_slice = y_words / 2;
|
|
/* Yp holds lower bits of Y (declared to reuse Y's array contents to save on copying) */
|
|
const mbedtls_mpi Yp = {
|
|
.p = Y->p,
|
|
.n = words_slice,
|
|
.s = Y->s
|
|
};
|
|
/* Ypp holds upper bits of Y, right shifted (also reuses Y's array contents) */
|
|
const mbedtls_mpi Ypp = {
|
|
.p = Y->p + words_slice,
|
|
.n = y_words - words_slice,
|
|
.s = Y->s
|
|
};
|
|
mbedtls_mpi_init(&Ztemp);
|
|
|
|
/* Get result Ztemp = Yp * X (need temporary variable Ztemp) */
|
|
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi(&Ztemp, X, &Yp) );
|
|
|
|
/* Z = Ypp * Y */
|
|
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi(Z, X, &Ypp) );
|
|
|
|
/* Z = Z << b */
|
|
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_l(Z, words_slice * 32) );
|
|
|
|
/* Z += Ztemp */
|
|
MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi(Z, Z, &Ztemp) );
|
|
|
|
cleanup:
|
|
mbedtls_mpi_free(&Ztemp);
|
|
|
|
return ret;
|
|
}
|
|
|
|
#endif /* MBEDTLS_MPI_MUL_MPI_ALT */
|
|
|