/*
* keylength in bits!
* message length in bits!
*/
void hmac_sha256(void* dest, void* key, uint16_t keylength_b, void* msg, uint64_t msglength_b){ /* a one-shot*/
sha256_ctx_t s;
uint8_t i;
uint8_t buffer[SHA256_HASH_BYTES];
memset(buffer, 0, SHA256_HASH_BYTES);
/* if key is larger than a block we have to hash it*/
if (keylength_b > SHA256_BLOCK_BITS){
sha256((void*)buffer, key, keylength_b);
} else {
memcpy(buffer, key, (keylength_b+7)/8);
}
for (i=0; i<SHA256_HASH_BYTES; ++i){
buffer[i] ^= IPAD;
}
sha256_init(&s);
sha256_nextBlock(&s, buffer);
while (msglength_b >= SHA256_BLOCK_BITS){
sha256_nextBlock(&s, msg);
msg = (uint8_t*)msg + SHA256_HASH_BYTES;
msglength_b -= SHA256_BLOCK_BITS;
}
sha256_lastBlock(&s, msg, msglength_b);
/* since buffer still contains key xor ipad we can do ... */
for (i=0; i<SHA256_HASH_BYTES; ++i){
buffer[i] ^= IPAD ^ OPAD;
}
sha256_ctx2hash(dest, &s); /* save inner hash temporary to dest */
sha256_init(&s);
sha256_nextBlock(&s, buffer);
sha256_lastBlock(&s, dest, SHA256_HASH_BITS);
sha256_ctx2hash(dest, &s);
}
void hmac_sha256_final(hmac_sha256_ctx_t *s, void* key, uint16_t keylength_b){
uint8_t buffer[SHA256_HASH_BYTES];
uint8_t i;
sha256_ctx_t a;
memset(buffer, 0, SHA256_HASH_BYTES);
if (keylength_b > SHA256_BLOCK_BITS){
sha256((void*)buffer, key, keylength_b);
} else {
memcpy(buffer, key, (keylength_b+7)/8);
}
for (i=0; i<SHA256_HASH_BYTES; ++i){
buffer[i] ^= OPAD;
}
sha256_init(&a);
sha256_nextBlock(&a, buffer); /* hash key ^ opad */
sha256_ctx2hash((void*)buffer, s); /* copy hash(key ^ ipad, msg) to buffer */
sha256_lastBlock(&a, buffer, SHA256_HASH_BITS);
memcpy(s, &a, sizeof(sha256_ctx_t));
#if defined SECURE_WIPE_BUFFER
memset(buffer, 0, SHA256_HASH_BYTES);
memset(a.h, 0, 8*4);
#endif
}
/*
* length in bits!
*/
void sha256(void* dest, const void* msg, uint32_t length_b){ /* length could be choosen longer but this is for µC */
sha256_ctx_t s;
sha256_init(&s);
while(length_b >= SHA256_BLOCK_BITS){
sha256_nextBlock(&s, msg);
msg = (uint8_t*)msg + SHA256_BLOCK_BITS/8;
length_b -= SHA256_BLOCK_BITS;
}
sha256_lastBlock(&s, msg, length_b);
sha256_ctx2hash(dest,&s);
}
void hmac_sha256_final(void* dest, hmac_sha256_ctx_t *s){
sha256_ctx2hash((sha256_hash_t*)dest, &(s->a));
sha256_lastBlock(&(s->b), dest, SHA256_HASH_BITS);
sha256_ctx2hash((sha256_hash_t*)dest, &(s->b));
}
