/**
* RC2 implementation.
*
* @author Stefan Siegl
*
* Copyright (c) 2012 Stefan Siegl <stesie@brokenpipe.de>
*
* Information on the RC2 cipher is available from RFC #2268,
* http://www.ietf.org/rfc/rfc2268.txt
*/
var forge = require('./forge');
require('./util');
var piTable = [
0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed, 0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d,
0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e, 0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2,
0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13, 0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32,
0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b, 0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82,
0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c, 0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc,
0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1, 0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26,
0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57, 0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03,
0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7, 0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7,
0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7, 0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a,
0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74, 0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec,
0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc, 0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39,
0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a, 0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31,
0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae, 0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9,
0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c, 0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9,
0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0, 0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e,
0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77, 0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad
];
var s = [1, 2, 3, 5];
/**
* Rotate a word left by given number of bits.
*
* Bits that are shifted out on the left are put back in on the right
* hand side.
*
* @param word The word to shift left.
* @param bits The number of bits to shift by.
* @return The rotated word.
*/
var rol = function(word, bits) {
return ((word << bits) & 0xffff) | ((word & 0xffff) >> (16 - bits));
};
/**
* Rotate a word right by given number of bits.
*
* Bits that are shifted out on the right are put back in on the left
* hand side.
*
* @param word The word to shift right.
* @param bits The number of bits to shift by.
* @return The rotated word.
*/
var ror = function(word, bits) {
return ((word & 0xffff) >> bits) | ((word << (16 - bits)) & 0xffff);
};
/* RC2 API */
module.exports = forge.rc2 = forge.rc2 || {};
/**
* Perform RC2 key expansion as per RFC #2268, section 2.
*
* @param key variable-length user key (between 1 and 128 bytes)
* @param effKeyBits number of effective key bits (default: 128)
* @return the expanded RC2 key (ByteBuffer of 128 bytes)
*/
forge.rc2.expandKey = function(key, effKeyBits) {
if(typeof key === 'string') {
key = forge.util.createBuffer(key);
}
effKeyBits = effKeyBits || 128;
/* introduce variables that match the names used in RFC #2268 */
var L = key;
var T = key.length();
var T1 = effKeyBits;
var T8 = Math.ceil(T1 / 8);
var TM = 0xff >> (T1 & 0x07);
var i;
for(i = T; i < 128; i++) {
L.putByte(piTable[(L.at(i - 1) + L.at(i - T)) & 0xff]);
}
L.setAt(128 - T8, piTable[L.at(128 - T8) & TM]);
for(i = 127 - T8; i >= 0; i--) {
L.setAt(i, piTable[L.at(i + 1) ^ L.at(i + T8)]);
}
return L;
};
/**
* Creates a RC2 cipher object.
*
* @param key the symmetric key to use (as base for key generation).
* @param bits the number of effective key bits.
* @param encrypt false for decryption, true for encryption.
*
* @return the cipher.
*/
var createCipher = function(key, bits, encrypt) {
var _finish = false, _input = null, _output = null, _iv = null;
var mixRound, mashRound;
var i, j, K = [];
/* Expand key and fill into K[] Array */
key = forge.rc2.expandKey(key, bits);
for(i = 0; i < 64; i++) {
K.push(key.getInt16Le());
}
if(encrypt) {
/**
* Perform one mixing round "in place".
*
* @param R Array of four words to perform mixing on.
*/
mixRound = function(R) {
for(i = 0; i < 4; i++) {
R[i] += K[j] + (R[(i + 3) % 4] & R[(i + 2) % 4]) +
((~R[(i + 3) % 4]) & R[(i + 1) % 4]);
R[i] = rol(R[i], s[i]);
j++;
}
};
/**
* Perform one mashing round "in place".
*
* @param R Array of four words to perform mashing on.
*/
mashRound = function(R) {
for(i = 0; i < 4; i++) {
R[i] += K[R[(i + 3) % 4] & 63];
}
};
} else {
/**
* Perform one r-mixing round "in place".
*
* @param R Array of four words to perform mixing on.
*/
mixRound = function(R) {
for(i = 3; i >= 0; i--) {
R[i] = ror(R[i], s[i]);
R[i] -= K[j] + (R[(i + 3) % 4] & R[(i + 2) % 4]) +
((~R[(i + 3) % 4]) & R[(i + 1) % 4]);
j--;
}
};
/**
* Perform one r-mashing round "in place".
*
* @param R Array of four words to perform mashing on.
*/
mashRound = function(R) {
for(i = 3; i >= 0; i--) {
R[i] -= K[R[(i + 3) % 4] & 63];
}
};
}
/**
* Run the specified cipher execution plan.
*
* This function takes four words from the input buffer, applies the IV on
* it (if requested) and runs the provided execution plan.
*
* The plan must be put together in form of a array of arrays. Where the
* outer one is simply a list of steps to perform and the inner one needs
* to have two elements: the first one telling how many rounds to perform,
* the second one telling what to do (i.e. the function to call).
*
* @param {Array} plan The plan to execute.
*/
var runPlan = function(plan) {
var R = [];
/* Get data from input buffer and fill the four words into R */
for(i = 0; i < 4; i++) {
var val = _input.getInt16Le();
if(_iv !== null) {
if(encrypt) {
/* We're encrypting, apply the IV first. */
val ^= _iv.getInt16Le();
} else {
/* We're decryption, keep cipher text for next block. */
_iv.putInt16Le(val);
}
}
R.push(val & 0xffff);
}
/* Reset global "j" variable as per spec. */
j = encrypt ? 0 : 63;
/* Run execution plan. */
for(var ptr = 0; ptr < plan.length; ptr++) {
for(var ctr = 0; ctr < plan[ptr][0]; ctr++) {
plan[ptr][1](R);
}
}
/* Write back result to output buffer. */
for(i = 0; i < 4; i++) {
if(_iv !== null) {
if(encrypt) {
/* We're encrypting in CBC-mode, feed back encrypted bytes into
IV buffer to carry it forward to next block. */
_iv.putInt16Le(R[i]);
} else {
R[i] ^= _iv.getInt16Le();
}
}
_output.putInt16Le(R[i]);
}
};
/* Create cipher object */
var cipher = null;
cipher = {
/**
* Starts or restarts the encryption or decryption process, whichever
* was previously configured.
*
* To use the cipher in CBC mode, iv may be given either as a string
* of bytes, or as a byte buffer. For ECB mode, give null as iv.
*
* @param iv the initialization vector to use, null for ECB mode.
* @param output the output the buffer to write to, null to create one.
*/
start: function(iv, output) {
if(iv) {
/* CBC mode */
if(typeof iv === 'string') {
iv = forge.util.createBuffer(iv);
}
}
_finish = false;
_input = forge.util.createBuffer();
_output = output || new forge.util.createBuffer();
_iv = iv;
cipher.output = _output;
},
/**
* Updates the next block.
*
* @param input the buffer to read from.
*/
update: function(input) {
if(!_finish) {
// not finishing, so fill the input buffer with more input
_input.putBuffer(input);
}
while(_input.length() >= 8) {
runPlan([
[ 5, mixRound ],
[ 1, mashRound ],
[ 6, mixRound ],
[ 1, mashRound ],
[ 5, mixRound ]
]);
}
},
/**
* Finishes encrypting or decrypting.
*
* @param pad a padding function to use, null for PKCS#7 padding,
* signature(blockSize, buffer, decrypt).
*
* @return true if successful, false on error.
*/
finish: function(pad) {
var rval = true;
if(encrypt) {
if(pad) {
rval = pad(8, _input, !encrypt);
} else {
// add PKCS#7 padding to block (each pad byte is the
// value of the number of pad bytes)
var padding = (_input.length() === 8) ? 8 : (8 - _input.length());
_input.fillWithByte(padding, padding);
}
}
if(rval) {
// do final update
_finish = true;
cipher.update();
}
if(!encrypt) {
// check for error: input data not a multiple of block size
rval = (_input.length() === 0);
if(rval) {
if(pad) {
rval = pad(8, _output, !encrypt);
} else {
// ensure padding byte count is valid
var len = _output.length();
var count = _output.at(len - 1);
if(count > len) {
rval = false;
} else {
// trim off padding bytes
_output.truncate(count);
}
}
}
}
return rval;
}
};
return cipher;
};
/**
* Creates an RC2 cipher object to encrypt data in ECB or CBC mode using the
* given symmetric key. The output will be stored in the 'output' member
* of the returned cipher.
*
* The key and iv may be given as a string of bytes or a byte buffer.
* The cipher is initialized to use 128 effective key bits.
*
* @param key the symmetric key to use.
* @param iv the initialization vector to use.
* @param output the buffer to write to, null to create one.
*
* @return the cipher.
*/
forge.rc2.startEncrypting = function(key, iv, output) {
var cipher = forge.rc2.createEncryptionCipher(key, 128);
cipher.start(iv, output);
return cipher;
};
/**
* Creates an RC2 cipher object to encrypt data in ECB or CBC mode using the
* given symmetric key.
*
* The key may be given as a string of bytes or a byte buffer.
*
* To start encrypting call start() on the cipher with an iv and optional
* output buffer.
*
* @param key the symmetric key to use.
*
* @return the cipher.
*/
forge.rc2.createEncryptionCipher = function(key, bits) {
return createCipher(key, bits, true);
};
/**
* Creates an RC2 cipher object to decrypt data in ECB or CBC mode using the
* given symmetric key. The output will be stored in the 'output' member
* of the returned cipher.
*
* The key and iv may be given as a string of bytes or a byte buffer.
* The cipher is initialized to use 128 effective key bits.
*
* @param key the symmetric key to use.
* @param iv the initialization vector to use.
* @param output the buffer to write to, null to create one.
*
* @return the cipher.
*/
forge.rc2.startDecrypting = function(key, iv, output) {
var cipher = forge.rc2.createDecryptionCipher(key, 128);
cipher.start(iv, output);
return cipher;
};
/**
* Creates an RC2 cipher object to decrypt data in ECB or CBC mode using the
* given symmetric key.
*
* The key may be given as a string of bytes or a byte buffer.
*
* To start decrypting call start() on the cipher with an iv and optional
* output buffer.
*
* @param key the symmetric key to use.
*
* @return the cipher.
*/
forge.rc2.createDecryptionCipher = function(key, bits) {
return createCipher(key, bits, false);
};