/**
* 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];
}