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package org.bouncycastle.crypto.prng.drbg;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.prng.EntropySource;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.encoders.Hex;
/**
* A SP800-90A CTR DRBG.
*/
public class CTRSP800DRBG
implements SP80090DRBG
{
private static final long TDEA_RESEED_MAX = 1L << (32 - 1);
private static final long AES_RESEED_MAX = 1L << (48 - 1);
private static final int TDEA_MAX_BITS_REQUEST = 1 << (13 - 1);
private static final int AES_MAX_BITS_REQUEST = 1 << (19 - 1);
private EntropySource _entropySource;
private BlockCipher _engine;
private int _keySizeInBits;
private int _seedLength;
private int _securityStrength;
// internal state
private byte[] _Key;
private byte[] _V;
private long _reseedCounter = 0;
private boolean _isTDEA = false;
/**
* Construct a SP800-90A CTR DRBG.
*
* Minimum entropy requirement is the security strength requested.
*
* @param engine underlying block cipher to use to support DRBG
* @param keySizeInBits size of the key to use with the block cipher.
* @param securityStrength security strength required (in bits)
* @param entropySource source of entropy to use for seeding/reseeding.
* @param personalizationString personalization string to distinguish this DRBG (may be null).
* @param nonce nonce to further distinguish this DRBG (may be null).
*/
public CTRSP800DRBG(BlockCipher engine, int keySizeInBits, int securityStrength, EntropySource entropySource, byte[] personalizationString, byte[] nonce)
{
_entropySource = entropySource;
_engine = engine;
_keySizeInBits = keySizeInBits;
_securityStrength = securityStrength;
_seedLength = keySizeInBits + engine.getBlockSize() * 8;
_isTDEA = isTDEA(engine);
if (securityStrength > 256)
{
throw new IllegalArgumentException("Requested security strength is not supported by the derivation function");
}
if (getMaxSecurityStrength(engine, keySizeInBits) < securityStrength)
{
throw new IllegalArgumentException("Requested security strength is not supported by block cipher and key size");
}
if (entropySource.entropySize() < securityStrength)
{
throw new IllegalArgumentException("Not enough entropy for security strength required");
}
byte[] entropy = getEntropy(); // Get_entropy_input
CTR_DRBG_Instantiate_algorithm(entropy, nonce, personalizationString);
}
private void CTR_DRBG_Instantiate_algorithm(byte[] entropy, byte[] nonce,
byte[] personalisationString)
{
byte[] seedMaterial = Arrays.concatenate(entropy, nonce, personalisationString);
byte[] seed = Block_Cipher_df(seedMaterial, _seedLength);
int outlen = _engine.getBlockSize();
_Key = new byte[(_keySizeInBits + 7) / 8];
_V = new byte[outlen];
// _Key & _V are modified by this call
CTR_DRBG_Update(seed, _Key, _V);
_reseedCounter = 1;
}
private void CTR_DRBG_Update(byte[] seed, byte[] key, byte[] v)
{
byte[] temp = new byte[seed.length];
byte[] outputBlock = new byte[_engine.getBlockSize()];
int i=0;
int outLen = _engine.getBlockSize();
_engine.init(true, new KeyParameter(expandKey(key)));
while (i*outLen < seed.length)
{
addOneTo(v);
_engine.processBlock(v, 0, outputBlock, 0);
int bytesToCopy = ((temp.length - i * outLen) > outLen)
? outLen : (temp.length - i * outLen);
System.arraycopy(outputBlock, 0, temp, i * outLen, bytesToCopy);
++i;
}
XOR(temp, seed, temp, 0);
System.arraycopy(temp, 0, key, 0, key.length);
System.arraycopy(temp, key.length, v, 0, v.length);
}
private void CTR_DRBG_Reseed_algorithm(byte[] additionalInput)
{
byte[] seedMaterial = Arrays.concatenate(getEntropy(), additionalInput);
seedMaterial = Block_Cipher_df(seedMaterial, _seedLength);
CTR_DRBG_Update(seedMaterial, _Key, _V);
_reseedCounter = 1;
}
private void XOR(byte[] out, byte[] a, byte[] b, int bOff)
{
for (int i=0; i< out.length; i++)
{
out[i] = (byte)(a[i] ^ b[i+bOff]);
}
}
private void addOneTo(byte[] longer)
{
int carry = 1;
for (int i = 1; i <= longer.length; i++) // warning
{
int res = (longer[longer.length - i] & 0xff) + carry;
carry = (res > 0xff) ? 1 : 0;
longer[longer.length - i] = (byte)res;
}
}
private byte[] getEntropy()
{
byte[] entropy = _entropySource.getEntropy();
if (entropy.length < (_securityStrength + 7) / 8)
{
throw new IllegalStateException("Insufficient entropy provided by entropy source");
}
return entropy;
}
// -- Internal state migration ---
private static final byte[] K_BITS = Hex.decodeStrict("000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F");
// 1. If (number_of_bits_to_return > max_number_of_bits), then return an
// ERROR_FLAG.
// 2. L = len (input_string)/8.
// 3. N = number_of_bits_to_return/8.
// Comment: L is the bitstring represention of
// the integer resulting from len (input_string)/8.
// L shall be represented as a 32-bit integer.
//
// Comment : N is the bitstring represention of
// the integer resulting from
// number_of_bits_to_return/8. N shall be
// represented as a 32-bit integer.
//
// 4. S = L || N || input_string || 0x80.
// 5. While (len (S) mod outlen)
// Comment : Pad S with zeros, if necessary.
// 0, S = S || 0x00.
//
// Comment : Compute the starting value.
// 6. temp = the Null string.
// 7. i = 0.
// 8. K = Leftmost keylen bits of 0x00010203...1D1E1F.
// 9. While len (temp) < keylen + outlen, do
//
// IV = i || 0outlen - len (i).
//
// 9.1
//
// temp = temp || BCC (K, (IV || S)).
//
// 9.2
//
// i = i + 1.
//
// 9.3
//
// Comment : i shall be represented as a 32-bit
// integer, i.e., len (i) = 32.
//
// Comment: The 32-bit integer represenation of
// i is padded with zeros to outlen bits.
//
// Comment: Compute the requested number of
// bits.
//
// 10. K = Leftmost keylen bits of temp.
//
// 11. X = Next outlen bits of temp.
//
// 12. temp = the Null string.
//
// 13. While len (temp) < number_of_bits_to_return, do
//
// 13.1 X = Block_Encrypt (K, X).
//
// 13.2 temp = temp || X.
//
// 14. requested_bits = Leftmost number_of_bits_to_return of temp.
//
// 15. Return SUCCESS and requested_bits.
private byte[] Block_Cipher_df(byte[] inputString, int bitLength)
{
int outLen = _engine.getBlockSize();
int L = inputString.length; // already in bytes
int N = bitLength / 8;
// 4 S = L || N || inputstring || 0x80
int sLen = 4 + 4 + L + 1;
int blockLen = ((sLen + outLen - 1) / outLen) * outLen;
byte[] S = new byte[blockLen];
copyIntToByteArray(S, L, 0);
copyIntToByteArray(S, N, 4);
System.arraycopy(inputString, 0, S, 8, L);
S[8 + L] = (byte)0x80;
// S already padded with zeros
byte[] temp = new byte[_keySizeInBits / 8 + outLen];
byte[] bccOut = new byte[outLen];
byte[] IV = new byte[outLen];
int i = 0;
byte[] K = new byte[_keySizeInBits / 8];
System.arraycopy(K_BITS, 0, K, 0, K.length);
while (i*outLen*8 < _keySizeInBits + outLen *8)
{
copyIntToByteArray(IV, i, 0);
BCC(bccOut, K, IV, S);
int bytesToCopy = ((temp.length - i * outLen) > outLen)
? outLen
: (temp.length - i * outLen);
System.arraycopy(bccOut, 0, temp, i * outLen, bytesToCopy);
++i;
}
byte[] X = new byte[outLen];
System.arraycopy(temp, 0, K, 0, K.length);
System.arraycopy(temp, K.length, X, 0, X.length);
temp = new byte[bitLength / 8];
i = 0;
_engine.init(true, new KeyParameter(expandKey(K)));
while (i * outLen < temp.length)
{
_engine.processBlock(X, 0, X, 0);
int bytesToCopy = ((temp.length - i * outLen) > outLen)
? outLen
: (temp.length - i * outLen);
System.arraycopy(X, 0, temp, i * outLen, bytesToCopy);
i++;
}
return temp;
}
/*
* 1. chaining_value = 0^outlen
* . Comment: Set the first chaining value to outlen zeros.
* 2. n = len (data)/outlen.
* 3. Starting with the leftmost bits of data, split the data into n blocks of outlen bits
* each, forming block(1) to block(n).
* 4. For i = 1 to n do
* 4.1 input_block = chaining_value ^ block(i) .
* 4.2 chaining_value = Block_Encrypt (Key, input_block).
* 5. output_block = chaining_value.
* 6. Return output_block.
*/
private void BCC(byte[] bccOut, byte[] k, byte[] iV, byte[] data)
{
int outlen = _engine.getBlockSize();
byte[] chainingValue = new byte[outlen]; // initial values = 0
int n = data.length / outlen;
byte[] inputBlock = new byte[outlen];
_engine.init(true, new KeyParameter(expandKey(k)));
_engine.processBlock(iV, 0, chainingValue, 0);
for (int i = 0; i < n; i++)
{
XOR(inputBlock, chainingValue, data, i*outlen);
_engine.processBlock(inputBlock, 0, chainingValue, 0);
}
System.arraycopy(chainingValue, 0, bccOut, 0, bccOut.length);
}
private void copyIntToByteArray(byte[] buf, int value, int offSet)
{
buf[offSet + 0] = ((byte)(value >> 24));
buf[offSet + 1] = ((byte)(value >> 16));
buf[offSet + 2] = ((byte)(value >> 8));
buf[offSet + 3] = ((byte)(value));
}
/**
* Return the block size (in bits) of the DRBG.
*
* @return the number of bits produced on each internal round of the DRBG.
*/
public int getBlockSize()
{
return _V.length * 8;
}
/**
* Populate a passed in array with random data.
*
* @param output output array for generated bits.
* @param additionalInput additional input to be added to the DRBG in this step.
* @param predictionResistant true if a reseed should be forced, false otherwise.
*
* @return number of bits generated, -1 if a reseed required.
*/
public int generate(byte[] output, byte[] additionalInput, boolean predictionResistant)
{
if (_isTDEA)
{
if (_reseedCounter > TDEA_RESEED_MAX)
{
return -1;
}
if (Utils.isTooLarge(output, TDEA_MAX_BITS_REQUEST / 8))
{
throw new IllegalArgumentException("Number of bits per request limited to " + TDEA_MAX_BITS_REQUEST);
}
}
else
{
if (_reseedCounter > AES_RESEED_MAX)
{
return -1;
}
if (Utils.isTooLarge(output, AES_MAX_BITS_REQUEST / 8))
{
throw new IllegalArgumentException("Number of bits per request limited to " + AES_MAX_BITS_REQUEST);
}
}
if (predictionResistant)
{
CTR_DRBG_Reseed_algorithm(additionalInput);
additionalInput = null;
}
if (additionalInput != null)
{
additionalInput = Block_Cipher_df(additionalInput, _seedLength);
CTR_DRBG_Update(additionalInput, _Key, _V);
}
else
{
additionalInput = new byte[_seedLength / 8];
}
byte[] out = new byte[_V.length];
_engine.init(true, new KeyParameter(expandKey(_Key)));
for (int i = 0; i <= output.length / out.length; i++)
{
int bytesToCopy = ((output.length - i * out.length) > out.length)
? out.length
: (output.length - i * _V.length);
if (bytesToCopy != 0)
{
addOneTo(_V);
_engine.processBlock(_V, 0, out, 0);
System.arraycopy(out, 0, output, i * out.length, bytesToCopy);
}
}
CTR_DRBG_Update(additionalInput, _Key, _V);
_reseedCounter++;
return output.length * 8;
}
/**
* Reseed the DRBG.
*
* @param additionalInput additional input to be added to the DRBG in this step.
*/
public void reseed(byte[] additionalInput)
{
CTR_DRBG_Reseed_algorithm(additionalInput);
}
private boolean isTDEA(BlockCipher cipher)
{
return cipher.getAlgorithmName().equals("DESede") || cipher.getAlgorithmName().equals("TDEA");
}
private int getMaxSecurityStrength(BlockCipher cipher, int keySizeInBits)
{
if (isTDEA(cipher) && keySizeInBits == 168)
{
return 112;
}
if (cipher.getAlgorithmName().equals("AES"))
{
return keySizeInBits;
}
return -1;
}
byte[] expandKey(byte[] key)
{
if (_isTDEA)
{
// expand key to 192 bits.
byte[] tmp = new byte[24];
padKey(key, 0, tmp, 0);
padKey(key, 7, tmp, 8);
padKey(key, 14, tmp, 16);
return tmp;
}
else
{
return key;
}
}
/**
* Pad out a key for TDEA, setting odd parity for each byte.
*
* @param keyMaster
* @param keyOff
* @param tmp
* @param tmpOff
*/
private void padKey(byte[] keyMaster, int keyOff, byte[] tmp, int tmpOff)
{
tmp[tmpOff + 0] = (byte)(keyMaster[keyOff + 0] & 0xfe);
tmp[tmpOff + 1] = (byte)((keyMaster[keyOff + 0] << 7) | ((keyMaster[keyOff + 1] & 0xfc) >>> 1));
tmp[tmpOff + 2] = (byte)((keyMaster[keyOff + 1] << 6) | ((keyMaster[keyOff + 2] & 0xf8) >>> 2));
tmp[tmpOff + 3] = (byte)((keyMaster[keyOff + 2] << 5) | ((keyMaster[keyOff + 3] & 0xf0) >>> 3));
tmp[tmpOff + 4] = (byte)((keyMaster[keyOff + 3] << 4) | ((keyMaster[keyOff + 4] & 0xe0) >>> 4));
tmp[tmpOff + 5] = (byte)((keyMaster[keyOff + 4] << 3) | ((keyMaster[keyOff + 5] & 0xc0) >>> 5));
tmp[tmpOff + 6] = (byte)((keyMaster[keyOff + 5] << 2) | ((keyMaster[keyOff + 6] & 0x80) >>> 6));
tmp[tmpOff + 7] = (byte)(keyMaster[keyOff + 6] << 1);
for (int i = tmpOff; i <= tmpOff + 7; i++)
{
int b = tmp[i];
tmp[i] = (byte)((b & 0xfe) |
((((b >> 1) ^
(b >> 2) ^
(b >> 3) ^
(b >> 4) ^
(b >> 5) ^
(b >> 6) ^
(b >> 7)) ^ 0x01) & 0x01));
}
}
}