/*
* This function stir entropy pool with MD2 function hash.
*
*/
static void randpool_stir(EntropyPool *pool)
{
size_t entropy = pool->entropy; //Save current calue of entropy.
Md2Context context;
uint8_t tmp_buf[((sizeof(size_t) * 2) + sizeof(int)) * 2 + 1]; //Temporary buffer.
md2_init(&context); //Init MD2 algorithm.
randpool_add(pool, NULL, 0);
for (int i = 0; i < (CONFIG_SIZE_ENTROPY_POOL / MD2_DIGEST_LEN); i++)
{
sprintf((char *)tmp_buf, "%0x%0x%0x", pool->counter, i, pool->pos_add);
/*
* Hash with MD2 algorithm the entropy pool.
*/
md2_update(&context, pool->pool_entropy, CONFIG_SIZE_ENTROPY_POOL);
md2_update(&context, tmp_buf, sizeof(tmp_buf) - 1);
/*Insert a message digest in entropy pool.*/
randpool_push(pool, md2_end(&context), MD2_DIGEST_LEN);
pool->counter = pool->counter + 1;
}
/*Insert in pool the difference between a two call of this function (see above).*/
randpool_add(pool, NULL, 0);
pool->entropy = entropy; //Restore old value of entropy. We haven't add entropy.
}
/**
* MD2 test fuction.
* This function test MD2 algorithm with a standard string specified
* in RFC 1319.
*
* \note This test work with official array of 256 byte pemutation
* contructed from digits of pi, defined in the RFC 1319.
*
*/
bool md2_test(void)
{
Md2Context context;
const char *test[] =
{
"",
"message digest",
"abcdefghijklmnopqrstuvwxyz",
"12345678901234567890123456789012345678901234567890123456789012345678901234567890"
};
const char *result[] = {
"\x83\x50\xe5\xa3\xe2\x4c\x15\x3d\xf2\x27\x5c\x9f\x80\x69\x27\x73",
"\xab\x4f\x49\x6b\xfb\x2a\x53\x0b\x21\x9f\xf3\x30\x31\xfe\x06\xb0",
"\x4e\x8d\xdf\xf3\x65\x02\x92\xab\x5a\x41\x08\xc3\xaa\x47\x94\x0b",
"\xd5\x97\x6f\x79\xd8\x3d\x3a\x0d\xc9\x80\x6c\x3c\x66\xf3\xef\xd8",
};
for (size_t i = 0; i < countof(test); i++)
{
md2_init(&context);
md2_update(&context, test[i], strlen(test[i]));
if(memcmp(result[i], md2_end(&context), MD2_DIGEST_LEN))
return false;
}
return true;
}
/**
* Get \param n_byte from entropy pool. If n_byte is larger than number
* byte of entropy in entropy pool, randpool_get continue
* to generate pseudocasual value from previous state of
* pool.
* \param n_byte number fo bytes to read.
* \param pool is the pool entropy context.
* \param _data is the pointer to write the random data to.
*/
void randpool_get(EntropyPool *pool, void *_data, size_t n_byte)
{
Md2Context context;
size_t i = pool->pos_get;
size_t n = n_byte;
size_t pos_write = 0; //Number of block has been written in data.
size_t len = MIN((size_t)MD2_DIGEST_LEN, n_byte);
uint8_t *data;
data = (uint8_t *)_data;
/* Test if i + CONFIG_MD2_BLOCK_LEN is inside of entropy pool.*/
ASSERT((MD2_DIGEST_LEN + i) <= CONFIG_SIZE_ENTROPY_POOL);
md2_init(&context);
while(n > 0)
{
/*Hash previous state of pool*/
md2_update(&context, &pool->pool_entropy[i], MD2_DIGEST_LEN);
memcpy(&data[pos_write], md2_end(&context), len);
pos_write += len; //Update number of block has been written in data.
n -= len; //Number of byte copied in data.
len = MIN(n,(size_t)MD2_DIGEST_LEN);
i = (i + MD2_DIGEST_LEN) % CONFIG_SIZE_ENTROPY_POOL;
/* If we haven't more entropy pool to hash, we stir it.*/
if(i < MD2_DIGEST_LEN)
{
randpool_stir(pool);
i = pool->pos_get;
}
}
pool->pos_get = i; //Current number of byte we get from pool.
pool->entropy -= n_byte; //Update a entropy.
}