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/*
* Copyright (c) 2024 Raspberry Pi (Trading) Ltd.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include "hardware/sha256.h"
#include "pico/bootrom/lock.h"
#include "pico/sha256.h"
#include "pico/time.h"
// We add one 0x80 byte, then 8 bytes for the size
#define SHA256_PADDING_DATA_BYTES 9
#define SHA256_BLOCK_SIZE_BYTES 64
bool __weak pico_sha256_lock(pico_sha256_state_t *state) {
if (!bootrom_try_acquire_lock(BOOTROM_LOCK_SHA_256))
return false;
state->locked = true;
return true;
}
void __weak pico_sha256_unlock(pico_sha256_state_t *state) {
assert(state->locked);
bootrom_release_lock(BOOTROM_LOCK_SHA_256);
state->locked = false;
}
int pico_sha256_try_start(pico_sha256_state_t *state, enum sha256_endianness endianness, bool use_dma) {
memset(state, 0, sizeof(*state));
if (!pico_sha256_lock(state)) return PICO_ERROR_RESOURCE_IN_USE;
state->endianness = endianness;
if (use_dma) {
state->channel = (int8_t)dma_claim_unused_channel(false);
if (state->channel < 0) {
pico_sha256_unlock(state);
return PICO_ERROR_INSUFFICIENT_RESOURCES;
}
state->config = dma_channel_get_default_config(state->channel);
channel_config_set_transfer_data_size(&state->config, DMA_SIZE_8);
channel_config_set_read_increment(&state->config, true);
channel_config_set_write_increment(&state->config, false);
channel_config_set_dreq(&state->config, DREQ_SHA256);
sha256_set_dma_size(1);
} else {
state->channel = -1;
}
sha256_err_not_ready_clear();
sha256_set_bswap(endianness == SHA256_BIG_ENDIAN);
sha256_start();
state->total_data_size = 0;
return PICO_OK;
}
int pico_sha256_start_blocking_until(pico_sha256_state_t *state, enum sha256_endianness endianness, bool use_dma, absolute_time_t until) {
int rc;
do {
rc = pico_sha256_try_start(state, endianness, use_dma);
if (rc != PICO_ERROR_RESOURCE_IN_USE) break;
if (time_reached(until)) {
rc = PICO_ERROR_TIMEOUT;
break;
}
} while (true);
return rc;
}
static void write_to_hardware(pico_sha256_state_t *state, const uint8_t *data, size_t data_size_bytes) {
if (state->channel >= 0) {
dma_channel_wait_for_finish_blocking(state->channel);
assert(!sha256_err_not_ready());
sha256_wait_ready_blocking();
dma_channel_configure(
state->channel,
&state->config,
sha256_get_write_addr(),
data,
data_size_bytes,
true
);
} else {
if (!state->cache_used && !(((uintptr_t)data)&3u)) {
GCC_Like_Pragma("GCC diagnostic ignored \"-Wcast-align\"")
const uint32_t *data32 = (const uint32_t *)data;
// aligned writes
while (data_size_bytes >= 4) {
// write a whole word
sha256_wait_ready_blocking();
sha256_put_word(*data32++);
data_size_bytes -= 4;
}
data = (const uint8_t *)data32;
}
while (data_size_bytes--) {
state->cache.bytes[state->cache_used++] = *data++;
if (state->cache_used == 4) {
state->cache_used = 0;
sha256_wait_ready_blocking();
sha256_put_word(state->cache.word);
}
}
}
}
static void update_internal(pico_sha256_state_t *state, const uint8_t *data, size_t data_size_bytes) {
assert(state->locked);
// must finish off the last 64 byte block first or else sha256_err_not_ready will be true
size_t bytes_left = ((state->total_data_size + (SHA256_BLOCK_SIZE_BYTES - 1)) & ~(SHA256_BLOCK_SIZE_BYTES - 1)) - state->total_data_size;
if (bytes_left > data_size_bytes) bytes_left = data_size_bytes;
if (bytes_left > 0) {
write_to_hardware(state, data, bytes_left);
state->total_data_size += bytes_left;
data_size_bytes -= bytes_left;
data += bytes_left;
}
// Write the rest of the data
if (data_size_bytes > 0) {
write_to_hardware(state, data, data_size_bytes);
state->total_data_size += data_size_bytes;
}
}
static void add_zero_bytes(pico_sha256_state_t *state, size_t data_size_bytes) {
uint32_t zero = 0;
// todo: can be done a bit more efficiently with dma?
assert(data_size_bytes < INT32_MAX);
while((int32_t)data_size_bytes > 0) {
update_internal(state, (uint8_t *)&zero, MIN(4, data_size_bytes));
data_size_bytes -= 4;
}
}
void pico_sha256_update(pico_sha256_state_t *state, const uint8_t *data, size_t data_size_bytes) {
update_internal(state, data, data_size_bytes);
}
void pico_sha256_update_blocking(pico_sha256_state_t *state, const uint8_t *data, size_t data_size_bytes) {
update_internal(state, data, data_size_bytes);
if (state->channel >= 0) {
dma_channel_wait_for_finish_blocking(state->channel);
}
}
// write the SHA-256 padding to hardware
static void write_padding(pico_sha256_state_t *state) {
// Has to be a multiple of 64 bytes
uint64_t size = (state->total_data_size + SHA256_PADDING_DATA_BYTES + (SHA256_BLOCK_SIZE_BYTES - 1)) & ~(SHA256_BLOCK_SIZE_BYTES - 1);
const size_t user_data_size = state->total_data_size;
const size_t padding_size_bytes = size - state->total_data_size;
// append a single '1' bit
const uint8_t one_bit = 0x80;
update_internal(state, &one_bit, 1);
// Zero unused padding
add_zero_bytes(state, padding_size_bytes - SHA256_PADDING_DATA_BYTES);
// Add size in bits, big endian
size = __builtin_bswap64(user_data_size * 8);
update_internal(state, (uint8_t*)&size, sizeof(uint64_t)); // last write
}
void pico_sha256_finish(pico_sha256_state_t *state, sha256_result_t *out) {
assert(state->locked);
// pass NULL to abandon the current hash in case of an error
if (out) {
write_padding(state);
if (state->channel >= 0) {
dma_channel_wait_for_finish_blocking(state->channel);
assert(!sha256_err_not_ready());
}
sha256_wait_valid_blocking();
sha256_get_result(out, state->endianness);
}
if (state->channel >= 0) {
dma_channel_cleanup(state->channel);
dma_channel_unclaim(state->channel);
state->channel = -1;
}
pico_sha256_unlock(state);
}
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