void
openvpn_hmac_calc (unsigned char *dest, unsigned char *src, uint16_t len)
{
const unsigned char *hmac_key = (const unsigned char *)CONF_OPENVPN_HMAC_KEY;
unsigned char buf[64];
/* perform inner part of hmac */
md5_ctx_t ctx_inner;
md5_init (&ctx_inner);
for (int i = 0; i < 16; i ++) buf[i] = hmac_key[i] ^ 0x36;
for (int i = 16; i < 64; i ++) buf[i] = 0x36;
md5_nextBlock (&ctx_inner, buf);
md5_lastBlock (&ctx_inner, src, len << 3);
/* perform outer part of hmac */
md5_ctx_t ctx_outer;
md5_init (&ctx_outer);
for (int i = 0; i < 16; i ++) buf[i] = hmac_key[i] ^ 0x5c;
for (int i = 16; i < 64; i ++) buf[i] = 0x5c;
md5_nextBlock (&ctx_outer, buf);
md5_lastBlock (&ctx_outer, (void *) &ctx_inner.a[0], 128);
memmove (dest, (void *) &ctx_outer.a[0], 16);
}
/*
* keylength in bits!
* message length in bits!
*/
void hmac_md5(void *dest, void *key, uint16_t keylength_b, void *msg, uint32_t msglength_b){ /* a one-shot*/
md5_ctx_t s;
uint8_t i;
uint8_t buffer[MD5_BLOCK_BYTES];
memset(buffer, 0, MD5_BLOCK_BYTES);
/* if key is larger than a block we have to hash it*/
if (keylength_b > MD5_BLOCK_BITS){
md5((void*)buffer, key, keylength_b);
} else {
memcpy(buffer, key, (keylength_b+7)/8);
}
for (i=0; i<MD5_BLOCK_BYTES; ++i){
buffer[i] ^= IPAD;
}
md5_init(&s);
md5_nextBlock(&s, buffer);
while (msglength_b >= MD5_BLOCK_BITS){
md5_nextBlock(&s, msg);
msg = (uint8_t*)msg + MD5_BLOCK_BYTES;
msglength_b -= MD5_BLOCK_BITS;
}
md5_lastBlock(&s, msg, msglength_b);
/* since buffer still contains key xor ipad we can do ... */
for (i=0; i<MD5_BLOCK_BYTES; ++i){
buffer[i] ^= IPAD ^ OPAD;
}
md5_ctx2hash(dest, &s); /* save inner hash temporary to dest */
md5_init(&s);
md5_nextBlock(&s, buffer);
md5_lastBlock(&s, dest, MD5_HASH_BITS);
md5_ctx2hash(dest, &s);
}
void hmac_md5_final(void *dest, hmac_md5_ctx_t *s){
md5_ctx2hash((md5_hash_t*)dest, &(s->a));
md5_lastBlock(&(s->b), dest, MD5_HASH_BITS);
md5_ctx2hash((md5_hash_t*)dest, &(s->b));
}
void hmac_md5_lastBlock(hmac_md5_ctx_t *s, const void *block, uint16_t length_b){
md5_lastBlock(&(s->a), block, length_b);
}
