/** * \brief Multi-precision integer library, ESP32 S2 hardware accelerated parts * * based on mbedTLS implementation * * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved * Additions Copyright (C) 2016-2020, Espressif Systems (Shanghai) PTE Ltd * SPDX-License-Identifier: Apache-2.0 * * 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. * */ #include "soc/hwcrypto_periph.h" #include "driver/periph_ctrl.h" #include #include "bignum_impl.h" #include "soc/dport_reg.h" #include "soc/periph_defs.h" #include #include "esp_crypto_lock.h" size_t esp_mpi_hardware_words(size_t words) { return words; } void esp_mpi_enable_hardware_hw_op( void ) { esp_crypto_mpi_lock_acquire(); /* Enable RSA hardware */ periph_module_enable(PERIPH_RSA_MODULE); DPORT_REG_CLR_BIT(DPORT_RSA_PD_CTRL_REG, DPORT_RSA_MEM_PD); while (DPORT_REG_READ(RSA_QUERY_CLEAN_REG) != 1) { } // Note: from enabling RSA clock to here takes about 1.3us } void esp_mpi_disable_hardware_hw_op( void ) { DPORT_REG_SET_BIT(DPORT_RSA_PD_CTRL_REG, DPORT_RSA_PD); /* Disable RSA hardware */ periph_module_disable(PERIPH_RSA_MODULE); esp_crypto_mpi_lock_release(); } /* Copy mbedTLS MPI bignum 'mpi' to hardware memory block at 'mem_base'. If num_words is higher than the number of words in the bignum then these additional words will be zeroed in the memory buffer. */ static inline void mpi_to_mem_block(uint32_t mem_base, const mbedtls_mpi *mpi, size_t num_words) { uint32_t *pbase = (uint32_t *)mem_base; uint32_t copy_words = MIN(num_words, mpi->n); /* Copy MPI data to memory block registers */ for (int i = 0; i < copy_words; i++) { pbase[i] = mpi->p[i]; } /* Zero any remaining memory block data */ for (int i = copy_words; i < num_words; i++) { pbase[i] = 0; } } /* Read mbedTLS MPI bignum back from hardware memory block. Reads num_words words from block. */ static inline void mem_block_to_mpi(mbedtls_mpi *x, uint32_t mem_base, int num_words) { /* Copy data from memory block registers */ esp_dport_access_read_buffer(x->p, mem_base, num_words); /* Zero any remaining limbs in the bignum, if the buffer is bigger than num_words */ for (size_t i = num_words; i < x->n; i++) { x->p[i] = 0; } } /* Begin an RSA operation. op_reg specifies which 'START' register to write to. */ static inline void start_op(uint32_t op_reg) { /* Clear interrupt status */ DPORT_REG_WRITE(RSA_CLEAR_INTERRUPT_REG, 1); /* Note: above REG_WRITE includes a memw, so we know any writes to the memory blocks are also complete. */ DPORT_REG_WRITE(op_reg, 1); } /* Wait for an RSA operation to complete. */ static inline void wait_op_complete(void) { while (DPORT_REG_READ(RSA_QUERY_INTERRUPT_REG) != 1) { } /* clear the interrupt */ DPORT_REG_WRITE(RSA_CLEAR_INTERRUPT_REG, 1); } /* Read result from last MPI operation */ void esp_mpi_read_result_hw_op(mbedtls_mpi *Z, size_t z_words) { wait_op_complete(); mem_block_to_mpi(Z, RSA_MEM_Z_BLOCK_BASE, z_words); } /* Z = (X * Y) mod M Not an mbedTLS function */ void esp_mpi_mul_mpi_mod_hw_op(const mbedtls_mpi *X, const mbedtls_mpi *Y, const mbedtls_mpi *M, const mbedtls_mpi *Rinv, mbedtls_mpi_uint Mprime, size_t num_words) { DPORT_REG_WRITE(RSA_LENGTH_REG, (num_words - 1)); /* Load M, X, Rinv, Mprime (Mprime is mod 2^32) */ mpi_to_mem_block(RSA_MEM_X_BLOCK_BASE, X, num_words); mpi_to_mem_block(RSA_MEM_Y_BLOCK_BASE, Y, num_words); mpi_to_mem_block(RSA_MEM_M_BLOCK_BASE, M, num_words); mpi_to_mem_block(RSA_MEM_RB_BLOCK_BASE, Rinv, num_words); DPORT_REG_WRITE(RSA_M_DASH_REG, Mprime); start_op(RSA_MOD_MULT_START_REG); } /* Z = (X ^ Y) mod M */ void esp_mpi_exp_mpi_mod_hw_op(const mbedtls_mpi *X, const mbedtls_mpi *Y, const mbedtls_mpi *M, const mbedtls_mpi *Rinv, mbedtls_mpi_uint Mprime, size_t num_words) { size_t y_bits = mbedtls_mpi_bitlen(Y); DPORT_REG_WRITE(RSA_LENGTH_REG, (num_words - 1)); /* Load M, X, Rinv, Mprime (Mprime is mod 2^32) */ mpi_to_mem_block(RSA_MEM_X_BLOCK_BASE, X, num_words); mpi_to_mem_block(RSA_MEM_Y_BLOCK_BASE, Y, num_words); mpi_to_mem_block(RSA_MEM_M_BLOCK_BASE, M, num_words); mpi_to_mem_block(RSA_MEM_RB_BLOCK_BASE, Rinv, num_words); DPORT_REG_WRITE(RSA_M_DASH_REG, Mprime); /* Enable acceleration options */ DPORT_REG_WRITE(RSA_CONSTANT_TIME_REG, 0); DPORT_REG_WRITE(RSA_SEARCH_OPEN_REG, 1); DPORT_REG_WRITE(RSA_SEARCH_POS_REG, y_bits - 1); /* Execute first stage montgomery multiplication */ start_op(RSA_MODEXP_START_REG); DPORT_REG_WRITE(RSA_SEARCH_OPEN_REG, 0); } /* Z = X * Y */ void esp_mpi_mul_mpi_hw_op(const mbedtls_mpi *X, const mbedtls_mpi *Y, size_t num_words) { /* Copy X (right-extended) & Y (left-extended) to memory block */ mpi_to_mem_block(RSA_MEM_X_BLOCK_BASE, X, num_words); mpi_to_mem_block(RSA_MEM_Z_BLOCK_BASE + num_words * 4, Y, num_words); /* NB: as Y is left-extended, we don't zero the bottom words_mult words of Y block. This is OK for now because zeroing is done by hardware when we do esp_mpi_acquire_hardware(). */ DPORT_REG_WRITE(RSA_LENGTH_REG, (num_words * 2 - 1)); start_op(RSA_MULT_START_REG); } /** * @brief Special-case of (X * Y), where we use hardware montgomery mod multiplication to calculate result where either A or B are >2048 bits so can't use the standard multiplication method. * */ void esp_mpi_mult_mpi_failover_mod_mult_hw_op(const mbedtls_mpi *X, const mbedtls_mpi *Y, size_t num_words) { /* 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, write first word */ DPORT_REG_WRITE(RSA_MEM_RB_BLOCK_BASE, 1); /* Zero out rest of the Rinv words */ 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); }