in src/main/java/org/apache/commons/codec/digest/Sha2Crypt.java [172:546]
private static String sha2Crypt(final byte[] keyBytes, final String salt, final String saltPrefix,
final int blocksize, final String algorithm) {
final int keyLen = keyBytes.length;
// Extracts effective salt and the number of rounds from the given salt.
int rounds = ROUNDS_DEFAULT;
boolean roundsCustom = false;
if (salt == null) {
throw new IllegalArgumentException("Salt must not be null");
}
final Matcher m = SALT_PATTERN.matcher(salt);
if (!m.find()) {
throw new IllegalArgumentException("Invalid salt value: " + salt);
}
if (m.group(3) != null) {
rounds = Integer.parseInt(m.group(3));
rounds = Math.max(ROUNDS_MIN, Math.min(ROUNDS_MAX, rounds));
roundsCustom = true;
}
final String saltString = m.group(4);
final byte[] saltBytes = saltString.getBytes(StandardCharsets.UTF_8);
final int saltLen = saltBytes.length;
// 1. start digest A
// Prepare for the real work.
MessageDigest ctx = DigestUtils.getDigest(algorithm);
// 2. the password string is added to digest A
/*
* Add the key string.
*/
ctx.update(keyBytes);
// 3. the salt string is added to digest A. This is just the salt string
// itself without the enclosing '$', without the magic salt_prefix $5$ and
// $6$ respectively and without the rounds=<N> specification.
//
// NB: the MD5 algorithm did add the $1$ salt_prefix. This is not deemed
// necessary since it is a constant string and does not add security
// and /possibly/ allows a plain text attack. Since the rounds=<N>
// specification should never be added this would also create an
// inconsistency.
/*
* The last part is the salt string. This must be at most 16 characters and it ends at the first `$' character
* (for compatibility with existing implementations).
*/
ctx.update(saltBytes);
// 4. start digest B
/*
* Compute alternate sha512 sum with input KEY, SALT, and KEY. The final result will be added to the first
* context.
*/
MessageDigest altCtx = DigestUtils.getDigest(algorithm);
// 5. add the password to digest B
/*
* Add key.
*/
altCtx.update(keyBytes);
// 6. add the salt string to digest B
/*
* Add salt.
*/
altCtx.update(saltBytes);
// 7. add the password again to digest B
/*
* Add key again.
*/
altCtx.update(keyBytes);
// 8. finish digest B
/*
* Now get result of this (32 bytes) and add it to the other context.
*/
byte[] altResult = altCtx.digest();
// 9. For each block of 32 or 64 bytes in the password string (excluding
// the terminating NUL in the C representation), add digest B to digest A
/*
* Add for any character in the key one byte of the alternate sum.
*/
/*
* (Remark: the C code comment seems wrong for key length > 32!)
*/
int cnt = keyBytes.length;
while (cnt > blocksize) {
ctx.update(altResult, 0, blocksize);
cnt -= blocksize;
}
// 10. For the remaining N bytes of the password string add the first
// N bytes of digest B to digest A
ctx.update(altResult, 0, cnt);
// 11. For each bit of the binary representation of the length of the
// password string up to and including the highest 1-digit, starting
// from to the lowest bit position (numeric value 1):
//
// a) for a 1-digit add digest B to digest A
//
// b) for a 0-digit add the password string
//
// NB: this step differs significantly from the MD5 algorithm. It
// adds more randomness.
/*
* Take the binary representation of the length of the key and for every 1 add the alternate sum, for every 0
* the key.
*/
cnt = keyBytes.length;
while (cnt > 0) {
if ((cnt & 1) != 0) {
ctx.update(altResult, 0, blocksize);
} else {
ctx.update(keyBytes);
}
cnt >>= 1;
}
// 12. finish digest A
/*
* Create intermediate result.
*/
altResult = ctx.digest();
// 13. start digest DP
/*
* Start computation of P byte sequence.
*/
altCtx = DigestUtils.getDigest(algorithm);
// 14. for every byte in the password (excluding the terminating NUL byte
// in the C representation of the string)
//
// add the password to digest DP
/*
* For every character in the password add the entire password.
*/
for (int i = 1; i <= keyLen; i++) {
altCtx.update(keyBytes);
}
// 15. finish digest DP
/*
* Finish the digest.
*/
byte[] tempResult = altCtx.digest();
// 16. produce byte sequence P of the same length as the password where
//
// a) for each block of 32 or 64 bytes of length of the password string
// the entire digest DP is used
//
// b) for the remaining N (up to 31 or 63) bytes use the first N
// bytes of digest DP
/*
* Create byte sequence P.
*/
final byte[] pBytes = new byte[keyLen];
int cp = 0;
while (cp < keyLen - blocksize) {
System.arraycopy(tempResult, 0, pBytes, cp, blocksize);
cp += blocksize;
}
System.arraycopy(tempResult, 0, pBytes, cp, keyLen - cp);
// 17. start digest DS
/*
* Start computation of S byte sequence.
*/
altCtx = DigestUtils.getDigest(algorithm);
// 18. repeat the following 16+A[0] times, where A[0] represents the first
// byte in digest A interpreted as an 8-bit unsigned value
//
// add the salt to digest DS
/*
* For every character in the password add the entire password.
*/
for (int i = 1; i <= 16 + (altResult[0] & 0xff); i++) {
altCtx.update(saltBytes);
}
// 19. finish digest DS
/*
* Finish the digest.
*/
tempResult = altCtx.digest();
// 20. produce byte sequence S of the same length as the salt string where
//
// a) for each block of 32 or 64 bytes of length of the salt string
// the entire digest DS is used
//
// b) for the remaining N (up to 31 or 63) bytes use the first N
// bytes of digest DS
/*
* Create byte sequence S.
*/
// Remark: The salt is limited to 16 chars, how does this make sense?
final byte[] sBytes = new byte[saltLen];
cp = 0;
while (cp < saltLen - blocksize) {
System.arraycopy(tempResult, 0, sBytes, cp, blocksize);
cp += blocksize;
}
System.arraycopy(tempResult, 0, sBytes, cp, saltLen - cp);
// 21. repeat a loop according to the number specified in the rounds=<N>
// specification in the salt (or the default value if none is
// present). Each round is numbered, starting with 0 and up to N-1.
//
// The loop uses a digest as input. In the first round it is the
// digest produced in step 12. In the latter steps it is the digest
// produced in step 21.h. The following text uses the notation
// "digest A/C" to describe this behavior.
/*
* Repeatedly run the collected hash value through sha512 to burn CPU cycles.
*/
for (int i = 0; i <= rounds - 1; i++) {
// a) start digest C
/*
* New context.
*/
ctx = DigestUtils.getDigest(algorithm);
// b) for odd round numbers add the byte sequence P to digest C
// c) for even round numbers add digest A/C
/*
* Add key or last result.
*/
if ((i & 1) != 0) {
ctx.update(pBytes, 0, keyLen);
} else {
ctx.update(altResult, 0, blocksize);
}
// d) for all round numbers not divisible by 3 add the byte sequence S
/*
* Add salt for numbers not divisible by 3.
*/
if (i % 3 != 0) {
ctx.update(sBytes, 0, saltLen);
}
// e) for all round numbers not divisible by 7 add the byte sequence P
/*
* Add key for numbers not divisible by 7.
*/
if (i % 7 != 0) {
ctx.update(pBytes, 0, keyLen);
}
// f) for odd round numbers add digest A/C
// g) for even round numbers add the byte sequence P
/*
* Add key or last result.
*/
if ((i & 1) != 0) {
ctx.update(altResult, 0, blocksize);
} else {
ctx.update(pBytes, 0, keyLen);
}
// h) finish digest C.
/*
* Create intermediate result.
*/
altResult = ctx.digest();
}
// 22. Produce the output string. This is an ASCII string of the maximum
// size specified above, consisting of multiple pieces:
//
// a) the salt salt_prefix, $5$ or $6$ respectively
//
// b) the rounds=<N> specification, if one was present in the input
// salt string. A trailing '$' is added in this case to separate
// the rounds specification from the following text.
//
// c) the salt string truncated to 16 characters
//
// d) a '$' character
/*
* Now we can construct the result string. It consists of three parts.
*/
final StringBuilder buffer = new StringBuilder(saltPrefix);
if (roundsCustom) {
buffer.append(ROUNDS_PREFIX);
buffer.append(rounds);
buffer.append("$");
}
buffer.append(saltString);
buffer.append("$");
// e) the base-64 encoded final C digest. The encoding used is as
// follows:
// [...]
//
// Each group of three bytes from the digest produces four
// characters as output:
//
// 1. character: the six low bits of the first byte
// 2. character: the two high bits of the first byte and the
// four low bytes from the second byte
// 3. character: the four high bytes from the second byte and
// the two low bits from the third byte
// 4. character: the six high bits from the third byte
//
// The groups of three bytes are as follows (in this sequence).
// These are the indices into the byte array containing the
// digest, starting with index 0. For the last group there are
// not enough bytes left in the digest and the value zero is used
// in its place. This group also produces only three or two
// characters as output for SHA-512 and SHA-512 respectively.
// This was just a safeguard in the C implementation:
// int buflen = salt_prefix.length() - 1 + ROUNDS_PREFIX.length() + 9 + 1 + salt_string.length() + 1 + 86 + 1;
if (blocksize == 32) {
B64.b64from24bit(altResult[0], altResult[10], altResult[20], 4, buffer);
B64.b64from24bit(altResult[21], altResult[1], altResult[11], 4, buffer);
B64.b64from24bit(altResult[12], altResult[22], altResult[2], 4, buffer);
B64.b64from24bit(altResult[3], altResult[13], altResult[23], 4, buffer);
B64.b64from24bit(altResult[24], altResult[4], altResult[14], 4, buffer);
B64.b64from24bit(altResult[15], altResult[25], altResult[5], 4, buffer);
B64.b64from24bit(altResult[6], altResult[16], altResult[26], 4, buffer);
B64.b64from24bit(altResult[27], altResult[7], altResult[17], 4, buffer);
B64.b64from24bit(altResult[18], altResult[28], altResult[8], 4, buffer);
B64.b64from24bit(altResult[9], altResult[19], altResult[29], 4, buffer);
B64.b64from24bit((byte) 0, altResult[31], altResult[30], 3, buffer);
} else {
B64.b64from24bit(altResult[0], altResult[21], altResult[42], 4, buffer);
B64.b64from24bit(altResult[22], altResult[43], altResult[1], 4, buffer);
B64.b64from24bit(altResult[44], altResult[2], altResult[23], 4, buffer);
B64.b64from24bit(altResult[3], altResult[24], altResult[45], 4, buffer);
B64.b64from24bit(altResult[25], altResult[46], altResult[4], 4, buffer);
B64.b64from24bit(altResult[47], altResult[5], altResult[26], 4, buffer);
B64.b64from24bit(altResult[6], altResult[27], altResult[48], 4, buffer);
B64.b64from24bit(altResult[28], altResult[49], altResult[7], 4, buffer);
B64.b64from24bit(altResult[50], altResult[8], altResult[29], 4, buffer);
B64.b64from24bit(altResult[9], altResult[30], altResult[51], 4, buffer);
B64.b64from24bit(altResult[31], altResult[52], altResult[10], 4, buffer);
B64.b64from24bit(altResult[53], altResult[11], altResult[32], 4, buffer);
B64.b64from24bit(altResult[12], altResult[33], altResult[54], 4, buffer);
B64.b64from24bit(altResult[34], altResult[55], altResult[13], 4, buffer);
B64.b64from24bit(altResult[56], altResult[14], altResult[35], 4, buffer);
B64.b64from24bit(altResult[15], altResult[36], altResult[57], 4, buffer);
B64.b64from24bit(altResult[37], altResult[58], altResult[16], 4, buffer);
B64.b64from24bit(altResult[59], altResult[17], altResult[38], 4, buffer);
B64.b64from24bit(altResult[18], altResult[39], altResult[60], 4, buffer);
B64.b64from24bit(altResult[40], altResult[61], altResult[19], 4, buffer);
B64.b64from24bit(altResult[62], altResult[20], altResult[41], 4, buffer);
B64.b64from24bit((byte) 0, (byte) 0, altResult[63], 2, buffer);
}
/*
* Clear the buffer for the intermediate result so that people attaching to processes or reading core dumps
* cannot get any information.
*/
// Is there a better way to do this with the JVM?
Arrays.fill(tempResult, (byte) 0);
Arrays.fill(pBytes, (byte) 0);
Arrays.fill(sBytes, (byte) 0);
ctx.reset();
altCtx.reset();
Arrays.fill(keyBytes, (byte) 0);
Arrays.fill(saltBytes, (byte) 0);
return buffer.toString();
}