twr_aes.c

#include <twr_aes.h>
#include <twr_system.h>
#include <twr_tick.h>
#include <stm32l0xx.h>
 
#define _TWR_AES_DATATYPE AES_CR_DATATYPE_1
 
static void _twr_aes_set_key(const twr_aes_key_t key);
static void _twr_aes_set_iv(const twr_aes_iv_t iv);
static bool _twr_aes_process(void *buffer_out, const void *buffer_in, size_t length);
 
void twr_aes_init(void)
{
    RCC->AHBENR |= RCC_AHBENR_CRYPEN_Msk;
    // Errata workaround
    RCC->AHBENR;
}
 
bool twr_aes_key_derivation(twr_aes_key_t decryption_key, const twr_aes_key_t key)
{
    twr_system_pll_enable();
 
    AES->CR = AES_CR_MODE_0;
 
    _twr_aes_set_key(key);
 
    AES->CR |= AES_CR_EN;
 
    twr_tick_t timeout = twr_tick_get() + 100;
 
    while ((AES->SR & AES_SR_CCF) == 0)
    {
        if (timeout < twr_tick_get())
        {
            twr_system_pll_disable();
            return false;
        }
    }
 
    decryption_key[0] = AES->KEYR0;
    decryption_key[1] = AES->KEYR1;
    decryption_key[2] = AES->KEYR2;
    decryption_key[3] = AES->KEYR3;
 
    AES->CR |= AES_CR_CCFC;
 
    twr_system_pll_disable();
 
    return true;
}
 
bool twr_aes_ecb_encrypt(void *buffer_out, const void *buffer_in, const size_t length, const twr_aes_key_t key)
{
    if ((length % 16) != 0)
    {
        return false;
    }
 
    AES->CR = _TWR_AES_DATATYPE;
 
    _twr_aes_set_key(key);
 
    return _twr_aes_process(buffer_out, buffer_in, length);
}
 
bool twr_aes_ecb_decrypt(void *buffer_out, const void *buffer_in, size_t length, twr_aes_key_t key)
{
    if ((length % 16) != 0)
    {
        return false;
    }
 
    AES->CR = _TWR_AES_DATATYPE | AES_CR_MODE_1;
 
    _twr_aes_set_key(key);
 
    return _twr_aes_process(buffer_out, buffer_in, length);
}
 
bool twr_aes_ctwr_encrypt(void *buffer_out, const void *buffer_in, size_t length, twr_aes_key_t key, twr_aes_iv_t iv)
{
    if ((length % 16) != 0)
    {
        return false;
    }
 
    AES->CR = AES_CR_CHMOD_0 | _TWR_AES_DATATYPE;
 
    _twr_aes_set_key(key);
 
    _twr_aes_set_iv(iv);
 
    return _twr_aes_process(buffer_out, buffer_in, length);
}
 
bool twr_aes_ctwr_decrypt(void *buffer_out, const void *buffer_in, size_t length, twr_aes_key_t key, twr_aes_iv_t iv)
{
    if ((length % 16) != 0)
    {
        return false;
    }
 
    AES->CR = AES_CR_CHMOD_0 | _TWR_AES_DATATYPE | AES_CR_MODE_1;
 
    _twr_aes_set_key(key);
 
    _twr_aes_set_iv(iv);
 
    return _twr_aes_process(buffer_out, buffer_in, length);
}
 
void twr_aes_key_from_uint8(twr_aes_key_t key, const uint8_t *buffer)
{
    uint8_t *tmp = (uint8_t *) key;
 
    for (int i = 0; i < 16; i++)
    {
        tmp[15 - i] = buffer[i];
    }
}
 
void twr_aes_iv_from_uint8(twr_aes_iv_t iv, const uint8_t *buffer)
{
    uint8_t *tmp = (uint8_t *) iv;
 
    for (int i = 0; i < 16; i++)
    {
        tmp[15 - i] = buffer[i];
    }
}
 
static void _twr_aes_set_key(const twr_aes_key_t key)
{
    AES->KEYR0 = key[0];
    AES->KEYR1 = key[1];
    AES->KEYR2 = key[2];
    AES->KEYR3 = key[3];
}
 
static void _twr_aes_set_iv(const twr_aes_iv_t iv)
{
    AES->IVR0 = iv[0];
    AES->IVR1 = iv[1];
    AES->IVR2 = iv[2];
    AES->IVR3 = iv[3];
}
 
static bool _twr_aes_process(void *buffer_out, const void *buffer_in, size_t length)
{
    uint8_t buffer[16];
 
    uint32_t *inputaddr = (uint32_t *) buffer_in;
    uint32_t *outputaddr = (uint32_t *) buffer_out;
 
    twr_system_pll_enable();
 
    bool inputaddr_aligned = ((uint32_t) inputaddr & (uint32_t) 0x00000003U) == 0U;
    bool outputaddr_aligned = ((uint32_t) outputaddr & (uint32_t) 0x00000003U) == 0U;
 
    if (!outputaddr_aligned)
    {
        outputaddr = (uint32_t *) buffer;
    }
 
    AES->CR |= AES_CR_EN;
 
    for (size_t i = 0; i < length; i += 16)
    {
        if (!inputaddr_aligned)
        {
            memcpy(buffer, (uint8_t *) buffer_in + i, 16);
 
            inputaddr = (uint32_t *) buffer;
        }
 
        AES->DINR = *(inputaddr++);
        AES->DINR = *(inputaddr++);
        AES->DINR = *(inputaddr++);
        AES->DINR = *(inputaddr++);
 
        twr_tick_t timeout = twr_tick_get() + 100;
 
        while ((AES->SR & AES_SR_CCF) == 0)
        {
            if (timeout < twr_tick_get())
            {
                twr_system_pll_disable();
                return false;
            }
        }
 
        AES->CR |= AES_CR_CCFC;
 
        *(outputaddr++) = AES->DOUTR;
        *(outputaddr++) = AES->DOUTR;
        *(outputaddr++) = AES->DOUTR;
        *(outputaddr++) = AES->DOUTR;
 
        if (!outputaddr_aligned)
        {
            memcpy((uint8_t *) buffer_out + i, buffer, 16);
            outputaddr = (uint32_t *) buffer;
        }
    }
 
    AES->CR &= ~AES_CR_EN;
 
    twr_system_pll_disable();
 
    return true;
}