void
dtls_hmac_init(dtls_hmac_context_t *ctx, const unsigned char *key, size_t klen) {
int i;
assert(ctx);
memset(ctx, 0, sizeof(dtls_hmac_context_t));
if (klen > DTLS_HMAC_BLOCKSIZE) {
dtls_hash_init(&ctx->data);
dtls_hash_update(&ctx->data, key, klen);
dtls_hash_finalize(ctx->pad, &ctx->data);
} else
memcpy(ctx->pad, key, klen);
/* create ipad: */
for (i=0; i < DTLS_HMAC_BLOCKSIZE; ++i)
ctx->pad[i] ^= 0x36;
dtls_hash_init(&ctx->data);
dtls_hmac_update(ctx, ctx->pad, DTLS_HMAC_BLOCKSIZE);
/* create opad by xor-ing pad[i] with 0x36 ^ 0x5C: */
for (i=0; i < DTLS_HMAC_BLOCKSIZE; ++i)
ctx->pad[i] ^= 0x6A;
}
int main(int argc, char **argv) {
static unsigned char buf[DTLS_HMAC_DIGEST_SIZE];
size_t len, i;
dtls_hmac_context_t *ctx;
if (argc < 3) {
fprintf(stderr, "usage: %s key text", argv[0]);
return -1;
}
dtls_hmac_storage_init();
ctx = dtls_hmac_new(argv[1], strlen(argv[1]));
assert(ctx);
dtls_hmac_update(ctx, argv[2], strlen(argv[2]));
len = dtls_hmac_finalize(ctx, buf);
for(i = 0; i < len; i++)
printf("%02x", buf[i]);
printf("\n");
dtls_hmac_free(ctx);
return 0;
}
void
dtls_mac(dtls_hmac_context_t *hmac_ctx,
const unsigned char *record,
const unsigned char *packet, size_t length,
unsigned char *buf) {
uint16 L;
dtls_int_to_uint16(L, length);
assert(hmac_ctx);
dtls_hmac_update(hmac_ctx, record +3, sizeof(uint16) + sizeof(uint48));
dtls_hmac_update(hmac_ctx, record, sizeof(uint8) + sizeof(uint16));
dtls_hmac_update(hmac_ctx, L, sizeof(uint16));
dtls_hmac_update(hmac_ctx, packet, length);
dtls_hmac_finalize(hmac_ctx, buf);
}
size_t
dtls_p_hash(dtls_hashfunc_t h,
const unsigned char *key, size_t keylen,
const unsigned char *label, size_t labellen,
const unsigned char *random1, size_t random1len,
const unsigned char *random2, size_t random2len,
unsigned char *buf, size_t buflen) {
dtls_hmac_context_t *hmac_a, *hmac_p;
unsigned char A[DTLS_HMAC_DIGEST_SIZE];
unsigned char tmp[DTLS_HMAC_DIGEST_SIZE];
size_t dlen; /* digest length */
size_t len = 0; /* result length */
hmac_a = dtls_hmac_new(key, keylen);
if (!hmac_a)
return 0;
/* calculate A(1) from A(0) == seed */
HMAC_UPDATE_SEED(hmac_a, label, labellen);
HMAC_UPDATE_SEED(hmac_a, random1, random1len);
HMAC_UPDATE_SEED(hmac_a, random2, random2len);
dlen = dtls_hmac_finalize(hmac_a, A);
hmac_p = dtls_hmac_new(key, keylen);
if (!hmac_p)
goto error;
while (len + dlen < buflen) {
/* FIXME: rewrite loop to avoid superflous call to dtls_hmac_init() */
dtls_hmac_init(hmac_p, key, keylen);
dtls_hmac_update(hmac_p, A, dlen);
HMAC_UPDATE_SEED(hmac_p, label, labellen);
HMAC_UPDATE_SEED(hmac_p, random1, random1len);
HMAC_UPDATE_SEED(hmac_p, random2, random2len);
len += dtls_hmac_finalize(hmac_p, tmp);
memcpy(buf, tmp, dlen);
buf += dlen;
/* calculate A(i+1) */
dtls_hmac_init(hmac_a, key, keylen);
dtls_hmac_update(hmac_a, A, dlen);
dtls_hmac_finalize(hmac_a, A);
}
dtls_hmac_init(hmac_p, key, keylen);
dtls_hmac_update(hmac_p, A, dlen);
HMAC_UPDATE_SEED(hmac_p, label, labellen);
HMAC_UPDATE_SEED(hmac_p, random1, random1len);
HMAC_UPDATE_SEED(hmac_p, random2, random2len);
dtls_hmac_finalize(hmac_p, tmp);
memcpy(buf, tmp, buflen - len);
error:
dtls_hmac_free(hmac_a);
dtls_hmac_free(hmac_p);
return buflen;
}