static byte[] doTLS12PRF(
byte[] secret,
byte[] labelBytes,
byte[] seed,
int outputLength,
String prfHash,
int prfHashLength,
int prfBlockSize)
throws NoSuchAlgorithmException, DigestException {
if (prfHash == null) {
throw new NoSuchAlgorithmException("Unspecified PRF algorithm");
}
MessageDigest prfMD = MessageDigest.getInstance(prfHash);
return doTLS12PRF(secret, labelBytes, seed, outputLength, prfMD, prfHashLength, prfBlockSize);
}
static byte[] doTLS12PRF(
byte[] secret,
byte[] labelBytes,
byte[] seed,
int outputLength,
MessageDigest mdPRF,
int mdPRFLen,
int mdPRFBlockSize)
throws DigestException {
if (secret == null) {
secret = B0;
}
// If we have a long secret, digest it first.
if (secret.length > mdPRFBlockSize) {
secret = mdPRF.digest(secret);
}
byte[] output = new byte[outputLength];
byte[] ipad;
byte[] opad;
switch (mdPRFBlockSize) {
case 64:
ipad = HMAC_ipad64.clone();
opad = HMAC_opad64.clone();
break;
case 128:
ipad = HMAC_ipad128.clone();
opad = HMAC_opad128.clone();
break;
default:
throw new DigestException("Unexpected block size.");
}
// P_HASH(Secret, label + seed)
expand(mdPRF, mdPRFLen, secret, 0, secret.length, labelBytes, seed, output, ipad, opad);
return output;
}
/*
* @param digest the MessageDigest to produce the HMAC
* @param hmacSize the HMAC size
* @param secret the secret
* @param secOff the offset into the secret
* @param secLen the secret length
* @param label the label
* @param seed the seed
* @param output the output array
*/
private static void expand(
MessageDigest digest,
int hmacSize,
byte[] secret,
int secOff,
int secLen,
byte[] label,
byte[] seed,
byte[] output,
byte[] pad1,
byte[] pad2)
throws DigestException {
/*
* modify the padding used, by XORing the key into our copy of that
* padding. That's to avoid doing that for each HMAC computation.
*/
for (int i = 0; i < secLen; i++) {
pad1[i] ^= secret[i + secOff];
pad2[i] ^= secret[i + secOff];
}
byte[] tmp = new byte[hmacSize];
byte[] aBytes = null;
/*
* compute:
*
* P_hash(secret, seed) = HMAC_hash(secret, A(1) + seed) +
* HMAC_hash(secret, A(2) + seed) +
* HMAC_hash(secret, A(3) + seed) + ...
* A() is defined as:
*
* A(0) = seed
* A(i) = HMAC_hash(secret, A(i-1))
*/
int remaining = output.length;
int ofs = 0;
while (remaining > 0) {
/*
* compute A() ...
*/
// inner digest
digest.update(pad1);
if (aBytes == null) {
digest.update(label);
digest.update(seed);
} else {
digest.update(aBytes);
}
digest.digest(tmp, 0, hmacSize);
// outer digest
digest.update(pad2);
digest.update(tmp);
if (aBytes == null) {
aBytes = new byte[hmacSize];
}
digest.digest(aBytes, 0, hmacSize);
/*
* compute HMAC_hash() ...
*/
// inner digest
digest.update(pad1);
digest.update(aBytes);
digest.update(label);
digest.update(seed);
digest.digest(tmp, 0, hmacSize);
// outer digest
digest.update(pad2);
digest.update(tmp);
digest.digest(tmp, 0, hmacSize);
int k = Math.min(hmacSize, remaining);
for (int i = 0; i < k; i++) {
output[ofs++] ^= tmp[i];
}
remaining -= k;
}
}
static byte[] doTLS10PRF(
byte[] secret,
byte[] labelBytes,
byte[] seed,
int outputLength,
MessageDigest md5,
MessageDigest sha)
throws DigestException {
/*
* Split the secret into two halves S1 and S2 of same length.
* S1 is taken from the first half of the secret, S2 from the
* second half.
* Their length is created by rounding up the length of the
* overall secret divided by two; thus, if the original secret
* is an odd number of bytes long, the last byte of S1 will be
* the same as the first byte of S2.
*
* Note: Instead of creating S1 and S2, we determine the offset into
* the overall secret where S2 starts.
*/
if (secret == null) {
secret = B0;
}
int off = secret.length >> 1;
int seclen = off + (secret.length & 1);
byte[] secKey = secret;
int keyLen = seclen;
byte[] output = new byte[outputLength];
// P_MD5(S1, label + seed)
// If we have a long secret, digest it first.
if (seclen > 64) { // 64: block size of HMAC-MD5
md5.update(secret, 0, seclen);
secKey = md5.digest();
keyLen = secKey.length;
}
expand(
md5,
16,
secKey,
0,
keyLen,
labelBytes,
seed,
output,
HMAC_ipad64.clone(),
HMAC_opad64.clone());
// P_SHA-1(S2, label + seed)
// If we have a long secret, digest it first.
if (seclen > 64) { // 64: block size of HMAC-SHA1
sha.update(secret, off, seclen);
secKey = sha.digest();
keyLen = secKey.length;
off = 0;
}
expand(
sha,
20,
secKey,
off,
keyLen,
labelBytes,
seed,
output,
HMAC_ipad64.clone(),
HMAC_opad64.clone());
return output;
}
static byte[] doTLS10PRF(byte[] secret, byte[] labelBytes, byte[] seed, int outputLength)
throws NoSuchAlgorithmException, DigestException {
MessageDigest md5 = MessageDigest.getInstance("MD5");
MessageDigest sha = MessageDigest.getInstance("SHA1");
return doTLS10PRF(secret, labelBytes, seed, outputLength, md5, sha);
}