/**
|
* Supported cipher modes.
|
*
|
* @author Dave Longley
|
*
|
* Copyright (c) 2010-2014 Digital Bazaar, Inc.
|
*/
|
var forge = require('./forge');
|
require('./util');
|
|
forge.cipher = forge.cipher || {};
|
|
// supported cipher modes
|
var modes = module.exports = forge.cipher.modes = forge.cipher.modes || {};
|
|
/** Electronic codebook (ECB) (Don't use this; it's not secure) **/
|
|
modes.ecb = function(options) {
|
options = options || {};
|
this.name = 'ECB';
|
this.cipher = options.cipher;
|
this.blockSize = options.blockSize || 16;
|
this._ints = this.blockSize / 4;
|
this._inBlock = new Array(this._ints);
|
this._outBlock = new Array(this._ints);
|
};
|
|
modes.ecb.prototype.start = function(options) {};
|
|
modes.ecb.prototype.encrypt = function(input, output, finish) {
|
// not enough input to encrypt
|
if(input.length() < this.blockSize && !(finish && input.length() > 0)) {
|
return true;
|
}
|
|
// get next block
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = input.getInt32();
|
}
|
|
// encrypt block
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// write output
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(this._outBlock[i]);
|
}
|
};
|
|
modes.ecb.prototype.decrypt = function(input, output, finish) {
|
// not enough input to decrypt
|
if(input.length() < this.blockSize && !(finish && input.length() > 0)) {
|
return true;
|
}
|
|
// get next block
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = input.getInt32();
|
}
|
|
// decrypt block
|
this.cipher.decrypt(this._inBlock, this._outBlock);
|
|
// write output
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(this._outBlock[i]);
|
}
|
};
|
|
modes.ecb.prototype.pad = function(input, options) {
|
// add PKCS#7 padding to block (each pad byte is the
|
// value of the number of pad bytes)
|
var padding = (input.length() === this.blockSize ?
|
this.blockSize : (this.blockSize - input.length()));
|
input.fillWithByte(padding, padding);
|
return true;
|
};
|
|
modes.ecb.prototype.unpad = function(output, options) {
|
// check for error: input data not a multiple of blockSize
|
if(options.overflow > 0) {
|
return false;
|
}
|
|
// ensure padding byte count is valid
|
var len = output.length();
|
var count = output.at(len - 1);
|
if(count > (this.blockSize << 2)) {
|
return false;
|
}
|
|
// trim off padding bytes
|
output.truncate(count);
|
return true;
|
};
|
|
/** Cipher-block Chaining (CBC) **/
|
|
modes.cbc = function(options) {
|
options = options || {};
|
this.name = 'CBC';
|
this.cipher = options.cipher;
|
this.blockSize = options.blockSize || 16;
|
this._ints = this.blockSize / 4;
|
this._inBlock = new Array(this._ints);
|
this._outBlock = new Array(this._ints);
|
};
|
|
modes.cbc.prototype.start = function(options) {
|
// Note: legacy support for using IV residue (has security flaws)
|
// if IV is null, reuse block from previous processing
|
if(options.iv === null) {
|
// must have a previous block
|
if(!this._prev) {
|
throw new Error('Invalid IV parameter.');
|
}
|
this._iv = this._prev.slice(0);
|
} else if(!('iv' in options)) {
|
throw new Error('Invalid IV parameter.');
|
} else {
|
// save IV as "previous" block
|
this._iv = transformIV(options.iv, this.blockSize);
|
this._prev = this._iv.slice(0);
|
}
|
};
|
|
modes.cbc.prototype.encrypt = function(input, output, finish) {
|
// not enough input to encrypt
|
if(input.length() < this.blockSize && !(finish && input.length() > 0)) {
|
return true;
|
}
|
|
// get next block
|
// CBC XOR's IV (or previous block) with plaintext
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = this._prev[i] ^ input.getInt32();
|
}
|
|
// encrypt block
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// write output, save previous block
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(this._outBlock[i]);
|
}
|
this._prev = this._outBlock;
|
};
|
|
modes.cbc.prototype.decrypt = function(input, output, finish) {
|
// not enough input to decrypt
|
if(input.length() < this.blockSize && !(finish && input.length() > 0)) {
|
return true;
|
}
|
|
// get next block
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = input.getInt32();
|
}
|
|
// decrypt block
|
this.cipher.decrypt(this._inBlock, this._outBlock);
|
|
// write output, save previous ciphered block
|
// CBC XOR's IV (or previous block) with ciphertext
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(this._prev[i] ^ this._outBlock[i]);
|
}
|
this._prev = this._inBlock.slice(0);
|
};
|
|
modes.cbc.prototype.pad = function(input, options) {
|
// add PKCS#7 padding to block (each pad byte is the
|
// value of the number of pad bytes)
|
var padding = (input.length() === this.blockSize ?
|
this.blockSize : (this.blockSize - input.length()));
|
input.fillWithByte(padding, padding);
|
return true;
|
};
|
|
modes.cbc.prototype.unpad = function(output, options) {
|
// check for error: input data not a multiple of blockSize
|
if(options.overflow > 0) {
|
return false;
|
}
|
|
// ensure padding byte count is valid
|
var len = output.length();
|
var count = output.at(len - 1);
|
if(count > (this.blockSize << 2)) {
|
return false;
|
}
|
|
// trim off padding bytes
|
output.truncate(count);
|
return true;
|
};
|
|
/** Cipher feedback (CFB) **/
|
|
modes.cfb = function(options) {
|
options = options || {};
|
this.name = 'CFB';
|
this.cipher = options.cipher;
|
this.blockSize = options.blockSize || 16;
|
this._ints = this.blockSize / 4;
|
this._inBlock = null;
|
this._outBlock = new Array(this._ints);
|
this._partialBlock = new Array(this._ints);
|
this._partialOutput = forge.util.createBuffer();
|
this._partialBytes = 0;
|
};
|
|
modes.cfb.prototype.start = function(options) {
|
if(!('iv' in options)) {
|
throw new Error('Invalid IV parameter.');
|
}
|
// use IV as first input
|
this._iv = transformIV(options.iv, this.blockSize);
|
this._inBlock = this._iv.slice(0);
|
this._partialBytes = 0;
|
};
|
|
modes.cfb.prototype.encrypt = function(input, output, finish) {
|
// not enough input to encrypt
|
var inputLength = input.length();
|
if(inputLength === 0) {
|
return true;
|
}
|
|
// encrypt block
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// handle full block
|
if(this._partialBytes === 0 && inputLength >= this.blockSize) {
|
// XOR input with output, write input as output
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = input.getInt32() ^ this._outBlock[i];
|
output.putInt32(this._inBlock[i]);
|
}
|
return;
|
}
|
|
// handle partial block
|
var partialBytes = (this.blockSize - inputLength) % this.blockSize;
|
if(partialBytes > 0) {
|
partialBytes = this.blockSize - partialBytes;
|
}
|
|
// XOR input with output, write input as partial output
|
this._partialOutput.clear();
|
for(var i = 0; i < this._ints; ++i) {
|
this._partialBlock[i] = input.getInt32() ^ this._outBlock[i];
|
this._partialOutput.putInt32(this._partialBlock[i]);
|
}
|
|
if(partialBytes > 0) {
|
// block still incomplete, restore input buffer
|
input.read -= this.blockSize;
|
} else {
|
// block complete, update input block
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = this._partialBlock[i];
|
}
|
}
|
|
// skip any previous partial bytes
|
if(this._partialBytes > 0) {
|
this._partialOutput.getBytes(this._partialBytes);
|
}
|
|
if(partialBytes > 0 && !finish) {
|
output.putBytes(this._partialOutput.getBytes(
|
partialBytes - this._partialBytes));
|
this._partialBytes = partialBytes;
|
return true;
|
}
|
|
output.putBytes(this._partialOutput.getBytes(
|
inputLength - this._partialBytes));
|
this._partialBytes = 0;
|
};
|
|
modes.cfb.prototype.decrypt = function(input, output, finish) {
|
// not enough input to decrypt
|
var inputLength = input.length();
|
if(inputLength === 0) {
|
return true;
|
}
|
|
// encrypt block (CFB always uses encryption mode)
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// handle full block
|
if(this._partialBytes === 0 && inputLength >= this.blockSize) {
|
// XOR input with output, write input as output
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = input.getInt32();
|
output.putInt32(this._inBlock[i] ^ this._outBlock[i]);
|
}
|
return;
|
}
|
|
// handle partial block
|
var partialBytes = (this.blockSize - inputLength) % this.blockSize;
|
if(partialBytes > 0) {
|
partialBytes = this.blockSize - partialBytes;
|
}
|
|
// XOR input with output, write input as partial output
|
this._partialOutput.clear();
|
for(var i = 0; i < this._ints; ++i) {
|
this._partialBlock[i] = input.getInt32();
|
this._partialOutput.putInt32(this._partialBlock[i] ^ this._outBlock[i]);
|
}
|
|
if(partialBytes > 0) {
|
// block still incomplete, restore input buffer
|
input.read -= this.blockSize;
|
} else {
|
// block complete, update input block
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = this._partialBlock[i];
|
}
|
}
|
|
// skip any previous partial bytes
|
if(this._partialBytes > 0) {
|
this._partialOutput.getBytes(this._partialBytes);
|
}
|
|
if(partialBytes > 0 && !finish) {
|
output.putBytes(this._partialOutput.getBytes(
|
partialBytes - this._partialBytes));
|
this._partialBytes = partialBytes;
|
return true;
|
}
|
|
output.putBytes(this._partialOutput.getBytes(
|
inputLength - this._partialBytes));
|
this._partialBytes = 0;
|
};
|
|
/** Output feedback (OFB) **/
|
|
modes.ofb = function(options) {
|
options = options || {};
|
this.name = 'OFB';
|
this.cipher = options.cipher;
|
this.blockSize = options.blockSize || 16;
|
this._ints = this.blockSize / 4;
|
this._inBlock = null;
|
this._outBlock = new Array(this._ints);
|
this._partialOutput = forge.util.createBuffer();
|
this._partialBytes = 0;
|
};
|
|
modes.ofb.prototype.start = function(options) {
|
if(!('iv' in options)) {
|
throw new Error('Invalid IV parameter.');
|
}
|
// use IV as first input
|
this._iv = transformIV(options.iv, this.blockSize);
|
this._inBlock = this._iv.slice(0);
|
this._partialBytes = 0;
|
};
|
|
modes.ofb.prototype.encrypt = function(input, output, finish) {
|
// not enough input to encrypt
|
var inputLength = input.length();
|
if(input.length() === 0) {
|
return true;
|
}
|
|
// encrypt block (OFB always uses encryption mode)
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// handle full block
|
if(this._partialBytes === 0 && inputLength >= this.blockSize) {
|
// XOR input with output and update next input
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(input.getInt32() ^ this._outBlock[i]);
|
this._inBlock[i] = this._outBlock[i];
|
}
|
return;
|
}
|
|
// handle partial block
|
var partialBytes = (this.blockSize - inputLength) % this.blockSize;
|
if(partialBytes > 0) {
|
partialBytes = this.blockSize - partialBytes;
|
}
|
|
// XOR input with output
|
this._partialOutput.clear();
|
for(var i = 0; i < this._ints; ++i) {
|
this._partialOutput.putInt32(input.getInt32() ^ this._outBlock[i]);
|
}
|
|
if(partialBytes > 0) {
|
// block still incomplete, restore input buffer
|
input.read -= this.blockSize;
|
} else {
|
// block complete, update input block
|
for(var i = 0; i < this._ints; ++i) {
|
this._inBlock[i] = this._outBlock[i];
|
}
|
}
|
|
// skip any previous partial bytes
|
if(this._partialBytes > 0) {
|
this._partialOutput.getBytes(this._partialBytes);
|
}
|
|
if(partialBytes > 0 && !finish) {
|
output.putBytes(this._partialOutput.getBytes(
|
partialBytes - this._partialBytes));
|
this._partialBytes = partialBytes;
|
return true;
|
}
|
|
output.putBytes(this._partialOutput.getBytes(
|
inputLength - this._partialBytes));
|
this._partialBytes = 0;
|
};
|
|
modes.ofb.prototype.decrypt = modes.ofb.prototype.encrypt;
|
|
/** Counter (CTR) **/
|
|
modes.ctr = function(options) {
|
options = options || {};
|
this.name = 'CTR';
|
this.cipher = options.cipher;
|
this.blockSize = options.blockSize || 16;
|
this._ints = this.blockSize / 4;
|
this._inBlock = null;
|
this._outBlock = new Array(this._ints);
|
this._partialOutput = forge.util.createBuffer();
|
this._partialBytes = 0;
|
};
|
|
modes.ctr.prototype.start = function(options) {
|
if(!('iv' in options)) {
|
throw new Error('Invalid IV parameter.');
|
}
|
// use IV as first input
|
this._iv = transformIV(options.iv, this.blockSize);
|
this._inBlock = this._iv.slice(0);
|
this._partialBytes = 0;
|
};
|
|
modes.ctr.prototype.encrypt = function(input, output, finish) {
|
// not enough input to encrypt
|
var inputLength = input.length();
|
if(inputLength === 0) {
|
return true;
|
}
|
|
// encrypt block (CTR always uses encryption mode)
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// handle full block
|
if(this._partialBytes === 0 && inputLength >= this.blockSize) {
|
// XOR input with output
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(input.getInt32() ^ this._outBlock[i]);
|
}
|
} else {
|
// handle partial block
|
var partialBytes = (this.blockSize - inputLength) % this.blockSize;
|
if(partialBytes > 0) {
|
partialBytes = this.blockSize - partialBytes;
|
}
|
|
// XOR input with output
|
this._partialOutput.clear();
|
for(var i = 0; i < this._ints; ++i) {
|
this._partialOutput.putInt32(input.getInt32() ^ this._outBlock[i]);
|
}
|
|
if(partialBytes > 0) {
|
// block still incomplete, restore input buffer
|
input.read -= this.blockSize;
|
}
|
|
// skip any previous partial bytes
|
if(this._partialBytes > 0) {
|
this._partialOutput.getBytes(this._partialBytes);
|
}
|
|
if(partialBytes > 0 && !finish) {
|
output.putBytes(this._partialOutput.getBytes(
|
partialBytes - this._partialBytes));
|
this._partialBytes = partialBytes;
|
return true;
|
}
|
|
output.putBytes(this._partialOutput.getBytes(
|
inputLength - this._partialBytes));
|
this._partialBytes = 0;
|
}
|
|
// block complete, increment counter (input block)
|
inc32(this._inBlock);
|
};
|
|
modes.ctr.prototype.decrypt = modes.ctr.prototype.encrypt;
|
|
/** Galois/Counter Mode (GCM) **/
|
|
modes.gcm = function(options) {
|
options = options || {};
|
this.name = 'GCM';
|
this.cipher = options.cipher;
|
this.blockSize = options.blockSize || 16;
|
this._ints = this.blockSize / 4;
|
this._inBlock = new Array(this._ints);
|
this._outBlock = new Array(this._ints);
|
this._partialOutput = forge.util.createBuffer();
|
this._partialBytes = 0;
|
|
// R is actually this value concatenated with 120 more zero bits, but
|
// we only XOR against R so the other zeros have no effect -- we just
|
// apply this value to the first integer in a block
|
this._R = 0xE1000000;
|
};
|
|
modes.gcm.prototype.start = function(options) {
|
if(!('iv' in options)) {
|
throw new Error('Invalid IV parameter.');
|
}
|
// ensure IV is a byte buffer
|
var iv = forge.util.createBuffer(options.iv);
|
|
// no ciphered data processed yet
|
this._cipherLength = 0;
|
|
// default additional data is none
|
var additionalData;
|
if('additionalData' in options) {
|
additionalData = forge.util.createBuffer(options.additionalData);
|
} else {
|
additionalData = forge.util.createBuffer();
|
}
|
|
// default tag length is 128 bits
|
if('tagLength' in options) {
|
this._tagLength = options.tagLength;
|
} else {
|
this._tagLength = 128;
|
}
|
|
// if tag is given, ensure tag matches tag length
|
this._tag = null;
|
if(options.decrypt) {
|
// save tag to check later
|
this._tag = forge.util.createBuffer(options.tag).getBytes();
|
if(this._tag.length !== (this._tagLength / 8)) {
|
throw new Error('Authentication tag does not match tag length.');
|
}
|
}
|
|
// create tmp storage for hash calculation
|
this._hashBlock = new Array(this._ints);
|
|
// no tag generated yet
|
this.tag = null;
|
|
// generate hash subkey
|
// (apply block cipher to "zero" block)
|
this._hashSubkey = new Array(this._ints);
|
this.cipher.encrypt([0, 0, 0, 0], this._hashSubkey);
|
|
// generate table M
|
// use 4-bit tables (32 component decomposition of a 16 byte value)
|
// 8-bit tables take more space and are known to have security
|
// vulnerabilities (in native implementations)
|
this.componentBits = 4;
|
this._m = this.generateHashTable(this._hashSubkey, this.componentBits);
|
|
// Note: support IV length different from 96 bits? (only supporting
|
// 96 bits is recommended by NIST SP-800-38D)
|
// generate J_0
|
var ivLength = iv.length();
|
if(ivLength === 12) {
|
// 96-bit IV
|
this._j0 = [iv.getInt32(), iv.getInt32(), iv.getInt32(), 1];
|
} else {
|
// IV is NOT 96-bits
|
this._j0 = [0, 0, 0, 0];
|
while(iv.length() > 0) {
|
this._j0 = this.ghash(
|
this._hashSubkey, this._j0,
|
[iv.getInt32(), iv.getInt32(), iv.getInt32(), iv.getInt32()]);
|
}
|
this._j0 = this.ghash(
|
this._hashSubkey, this._j0, [0, 0].concat(from64To32(ivLength * 8)));
|
}
|
|
// generate ICB (initial counter block)
|
this._inBlock = this._j0.slice(0);
|
inc32(this._inBlock);
|
this._partialBytes = 0;
|
|
// consume authentication data
|
additionalData = forge.util.createBuffer(additionalData);
|
// save additional data length as a BE 64-bit number
|
this._aDataLength = from64To32(additionalData.length() * 8);
|
// pad additional data to 128 bit (16 byte) block size
|
var overflow = additionalData.length() % this.blockSize;
|
if(overflow) {
|
additionalData.fillWithByte(0, this.blockSize - overflow);
|
}
|
this._s = [0, 0, 0, 0];
|
while(additionalData.length() > 0) {
|
this._s = this.ghash(this._hashSubkey, this._s, [
|
additionalData.getInt32(),
|
additionalData.getInt32(),
|
additionalData.getInt32(),
|
additionalData.getInt32()
|
]);
|
}
|
};
|
|
modes.gcm.prototype.encrypt = function(input, output, finish) {
|
// not enough input to encrypt
|
var inputLength = input.length();
|
if(inputLength === 0) {
|
return true;
|
}
|
|
// encrypt block
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// handle full block
|
if(this._partialBytes === 0 && inputLength >= this.blockSize) {
|
// XOR input with output
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(this._outBlock[i] ^= input.getInt32());
|
}
|
this._cipherLength += this.blockSize;
|
} else {
|
// handle partial block
|
var partialBytes = (this.blockSize - inputLength) % this.blockSize;
|
if(partialBytes > 0) {
|
partialBytes = this.blockSize - partialBytes;
|
}
|
|
// XOR input with output
|
this._partialOutput.clear();
|
for(var i = 0; i < this._ints; ++i) {
|
this._partialOutput.putInt32(input.getInt32() ^ this._outBlock[i]);
|
}
|
|
if(partialBytes <= 0 || finish) {
|
// handle overflow prior to hashing
|
if(finish) {
|
// get block overflow
|
var overflow = inputLength % this.blockSize;
|
this._cipherLength += overflow;
|
// truncate for hash function
|
this._partialOutput.truncate(this.blockSize - overflow);
|
} else {
|
this._cipherLength += this.blockSize;
|
}
|
|
// get output block for hashing
|
for(var i = 0; i < this._ints; ++i) {
|
this._outBlock[i] = this._partialOutput.getInt32();
|
}
|
this._partialOutput.read -= this.blockSize;
|
}
|
|
// skip any previous partial bytes
|
if(this._partialBytes > 0) {
|
this._partialOutput.getBytes(this._partialBytes);
|
}
|
|
if(partialBytes > 0 && !finish) {
|
// block still incomplete, restore input buffer, get partial output,
|
// and return early
|
input.read -= this.blockSize;
|
output.putBytes(this._partialOutput.getBytes(
|
partialBytes - this._partialBytes));
|
this._partialBytes = partialBytes;
|
return true;
|
}
|
|
output.putBytes(this._partialOutput.getBytes(
|
inputLength - this._partialBytes));
|
this._partialBytes = 0;
|
}
|
|
// update hash block S
|
this._s = this.ghash(this._hashSubkey, this._s, this._outBlock);
|
|
// increment counter (input block)
|
inc32(this._inBlock);
|
};
|
|
modes.gcm.prototype.decrypt = function(input, output, finish) {
|
// not enough input to decrypt
|
var inputLength = input.length();
|
if(inputLength < this.blockSize && !(finish && inputLength > 0)) {
|
return true;
|
}
|
|
// encrypt block (GCM always uses encryption mode)
|
this.cipher.encrypt(this._inBlock, this._outBlock);
|
|
// increment counter (input block)
|
inc32(this._inBlock);
|
|
// update hash block S
|
this._hashBlock[0] = input.getInt32();
|
this._hashBlock[1] = input.getInt32();
|
this._hashBlock[2] = input.getInt32();
|
this._hashBlock[3] = input.getInt32();
|
this._s = this.ghash(this._hashSubkey, this._s, this._hashBlock);
|
|
// XOR hash input with output
|
for(var i = 0; i < this._ints; ++i) {
|
output.putInt32(this._outBlock[i] ^ this._hashBlock[i]);
|
}
|
|
// increment cipher data length
|
if(inputLength < this.blockSize) {
|
this._cipherLength += inputLength % this.blockSize;
|
} else {
|
this._cipherLength += this.blockSize;
|
}
|
};
|
|
modes.gcm.prototype.afterFinish = function(output, options) {
|
var rval = true;
|
|
// handle overflow
|
if(options.decrypt && options.overflow) {
|
output.truncate(this.blockSize - options.overflow);
|
}
|
|
// handle authentication tag
|
this.tag = forge.util.createBuffer();
|
|
// concatenate additional data length with cipher length
|
var lengths = this._aDataLength.concat(from64To32(this._cipherLength * 8));
|
|
// include lengths in hash
|
this._s = this.ghash(this._hashSubkey, this._s, lengths);
|
|
// do GCTR(J_0, S)
|
var tag = [];
|
this.cipher.encrypt(this._j0, tag);
|
for(var i = 0; i < this._ints; ++i) {
|
this.tag.putInt32(this._s[i] ^ tag[i]);
|
}
|
|
// trim tag to length
|
this.tag.truncate(this.tag.length() % (this._tagLength / 8));
|
|
// check authentication tag
|
if(options.decrypt && this.tag.bytes() !== this._tag) {
|
rval = false;
|
}
|
|
return rval;
|
};
|
|
/**
|
* See NIST SP-800-38D 6.3 (Algorithm 1). This function performs Galois
|
* field multiplication. The field, GF(2^128), is defined by the polynomial:
|
*
|
* x^128 + x^7 + x^2 + x + 1
|
*
|
* Which is represented in little-endian binary form as: 11100001 (0xe1). When
|
* the value of a coefficient is 1, a bit is set. The value R, is the
|
* concatenation of this value and 120 zero bits, yielding a 128-bit value
|
* which matches the block size.
|
*
|
* This function will multiply two elements (vectors of bytes), X and Y, in
|
* the field GF(2^128). The result is initialized to zero. For each bit of
|
* X (out of 128), x_i, if x_i is set, then the result is multiplied (XOR'd)
|
* by the current value of Y. For each bit, the value of Y will be raised by
|
* a power of x (multiplied by the polynomial x). This can be achieved by
|
* shifting Y once to the right. If the current value of Y, prior to being
|
* multiplied by x, has 0 as its LSB, then it is a 127th degree polynomial.
|
* Otherwise, we must divide by R after shifting to find the remainder.
|
*
|
* @param x the first block to multiply by the second.
|
* @param y the second block to multiply by the first.
|
*
|
* @return the block result of the multiplication.
|
*/
|
modes.gcm.prototype.multiply = function(x, y) {
|
var z_i = [0, 0, 0, 0];
|
var v_i = y.slice(0);
|
|
// calculate Z_128 (block has 128 bits)
|
for(var i = 0; i < 128; ++i) {
|
// if x_i is 0, Z_{i+1} = Z_i (unchanged)
|
// else Z_{i+1} = Z_i ^ V_i
|
// get x_i by finding 32-bit int position, then left shift 1 by remainder
|
var x_i = x[(i / 32) | 0] & (1 << (31 - i % 32));
|
if(x_i) {
|
z_i[0] ^= v_i[0];
|
z_i[1] ^= v_i[1];
|
z_i[2] ^= v_i[2];
|
z_i[3] ^= v_i[3];
|
}
|
|
// if LSB(V_i) is 1, V_i = V_i >> 1
|
// else V_i = (V_i >> 1) ^ R
|
this.pow(v_i, v_i);
|
}
|
|
return z_i;
|
};
|
|
modes.gcm.prototype.pow = function(x, out) {
|
// if LSB(x) is 1, x = x >>> 1
|
// else x = (x >>> 1) ^ R
|
var lsb = x[3] & 1;
|
|
// always do x >>> 1:
|
// starting with the rightmost integer, shift each integer to the right
|
// one bit, pulling in the bit from the integer to the left as its top
|
// most bit (do this for the last 3 integers)
|
for(var i = 3; i > 0; --i) {
|
out[i] = (x[i] >>> 1) | ((x[i - 1] & 1) << 31);
|
}
|
// shift the first integer normally
|
out[0] = x[0] >>> 1;
|
|
// if lsb was not set, then polynomial had a degree of 127 and doesn't
|
// need to divided; otherwise, XOR with R to find the remainder; we only
|
// need to XOR the first integer since R technically ends w/120 zero bits
|
if(lsb) {
|
out[0] ^= this._R;
|
}
|
};
|
|
modes.gcm.prototype.tableMultiply = function(x) {
|
// assumes 4-bit tables are used
|
var z = [0, 0, 0, 0];
|
for(var i = 0; i < 32; ++i) {
|
var idx = (i / 8) | 0;
|
var x_i = (x[idx] >>> ((7 - (i % 8)) * 4)) & 0xF;
|
var ah = this._m[i][x_i];
|
z[0] ^= ah[0];
|
z[1] ^= ah[1];
|
z[2] ^= ah[2];
|
z[3] ^= ah[3];
|
}
|
return z;
|
};
|
|
/**
|
* A continuing version of the GHASH algorithm that operates on a single
|
* block. The hash block, last hash value (Ym) and the new block to hash
|
* are given.
|
*
|
* @param h the hash block.
|
* @param y the previous value for Ym, use [0, 0, 0, 0] for a new hash.
|
* @param x the block to hash.
|
*
|
* @return the hashed value (Ym).
|
*/
|
modes.gcm.prototype.ghash = function(h, y, x) {
|
y[0] ^= x[0];
|
y[1] ^= x[1];
|
y[2] ^= x[2];
|
y[3] ^= x[3];
|
return this.tableMultiply(y);
|
//return this.multiply(y, h);
|
};
|
|
/**
|
* Precomputes a table for multiplying against the hash subkey. This
|
* mechanism provides a substantial speed increase over multiplication
|
* performed without a table. The table-based multiplication this table is
|
* for solves X * H by multiplying each component of X by H and then
|
* composing the results together using XOR.
|
*
|
* This function can be used to generate tables with different bit sizes
|
* for the components, however, this implementation assumes there are
|
* 32 components of X (which is a 16 byte vector), therefore each component
|
* takes 4-bits (so the table is constructed with bits=4).
|
*
|
* @param h the hash subkey.
|
* @param bits the bit size for a component.
|
*/
|
modes.gcm.prototype.generateHashTable = function(h, bits) {
|
// TODO: There are further optimizations that would use only the
|
// first table M_0 (or some variant) along with a remainder table;
|
// this can be explored in the future
|
var multiplier = 8 / bits;
|
var perInt = 4 * multiplier;
|
var size = 16 * multiplier;
|
var m = new Array(size);
|
for(var i = 0; i < size; ++i) {
|
var tmp = [0, 0, 0, 0];
|
var idx = (i / perInt) | 0;
|
var shft = ((perInt - 1 - (i % perInt)) * bits);
|
tmp[idx] = (1 << (bits - 1)) << shft;
|
m[i] = this.generateSubHashTable(this.multiply(tmp, h), bits);
|
}
|
return m;
|
};
|
|
/**
|
* Generates a table for multiplying against the hash subkey for one
|
* particular component (out of all possible component values).
|
*
|
* @param mid the pre-multiplied value for the middle key of the table.
|
* @param bits the bit size for a component.
|
*/
|
modes.gcm.prototype.generateSubHashTable = function(mid, bits) {
|
// compute the table quickly by minimizing the number of
|
// POW operations -- they only need to be performed for powers of 2,
|
// all other entries can be composed from those powers using XOR
|
var size = 1 << bits;
|
var half = size >>> 1;
|
var m = new Array(size);
|
m[half] = mid.slice(0);
|
var i = half >>> 1;
|
while(i > 0) {
|
// raise m0[2 * i] and store in m0[i]
|
this.pow(m[2 * i], m[i] = []);
|
i >>= 1;
|
}
|
i = 2;
|
while(i < half) {
|
for(var j = 1; j < i; ++j) {
|
var m_i = m[i];
|
var m_j = m[j];
|
m[i + j] = [
|
m_i[0] ^ m_j[0],
|
m_i[1] ^ m_j[1],
|
m_i[2] ^ m_j[2],
|
m_i[3] ^ m_j[3]
|
];
|
}
|
i *= 2;
|
}
|
m[0] = [0, 0, 0, 0];
|
/* Note: We could avoid storing these by doing composition during multiply
|
calculate top half using composition by speed is preferred. */
|
for(i = half + 1; i < size; ++i) {
|
var c = m[i ^ half];
|
m[i] = [mid[0] ^ c[0], mid[1] ^ c[1], mid[2] ^ c[2], mid[3] ^ c[3]];
|
}
|
return m;
|
};
|
|
/** Utility functions */
|
|
function transformIV(iv, blockSize) {
|
if(typeof iv === 'string') {
|
// convert iv string into byte buffer
|
iv = forge.util.createBuffer(iv);
|
}
|
|
if(forge.util.isArray(iv) && iv.length > 4) {
|
// convert iv byte array into byte buffer
|
var tmp = iv;
|
iv = forge.util.createBuffer();
|
for(var i = 0; i < tmp.length; ++i) {
|
iv.putByte(tmp[i]);
|
}
|
}
|
|
if(iv.length() < blockSize) {
|
throw new Error(
|
'Invalid IV length; got ' + iv.length() +
|
' bytes and expected ' + blockSize + ' bytes.');
|
}
|
|
if(!forge.util.isArray(iv)) {
|
// convert iv byte buffer into 32-bit integer array
|
var ints = [];
|
var blocks = blockSize / 4;
|
for(var i = 0; i < blocks; ++i) {
|
ints.push(iv.getInt32());
|
}
|
iv = ints;
|
}
|
|
return iv;
|
}
|
|
function inc32(block) {
|
// increment last 32 bits of block only
|
block[block.length - 1] = (block[block.length - 1] + 1) & 0xFFFFFFFF;
|
}
|
|
function from64To32(num) {
|
// convert 64-bit number to two BE Int32s
|
return [(num / 0x100000000) | 0, num & 0xFFFFFFFF];
|
}
|
