ghash.js

// Parts of this file are derived from SJCL, which is LICENSED (BSD-2 or GPL-2), see https://github.com/bitwiseshiftleft/sjcl/blob/master/LICENSE.txt
//
// SJCL is open. You can use, modify and redistribute it under a BSD
// license or under the GNU GPL, version 2.0.
//
//---------------------------------------------------------------------
//
// http://opensource.org/licenses/BSD-2-Clause
//
// Copyright (c) 2009-2015, Emily Stark, Mike Hamburg and Dan Boneh at Stanford University. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
// 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// ---------------------------------------------------------------------
//
// http://opensource.org/licenses/GPL-2.0
//
// The Stanford Javascript Crypto Library (hosted here on GitHub) is a
// project by the Stanford Computer Security Lab to build a secure,
// powerful, fast, small, easy-to-use, cross-browser library for
// cryptography in Javascript.
// 
// Copyright (c) 2009-2015, Emily Stark, Mike Hamburg and Dan Boneh at
// Stanford University.
// 
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2 of the License, or (at your
// option) any later version.
// 
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
// Public License for more details.
// 
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

var Buffer = require('safe-buffer').Buffer
var ZEROES = Buffer.alloc(16, 0)

function toArray (buf) {
  return [
    buf.readUInt32BE(0),
    buf.readUInt32BE(4),
    buf.readUInt32BE(8),
    buf.readUInt32BE(12)
  ]
}

function fromArray (out) {
  var buf = Buffer.allocUnsafe(16)
  buf.writeUInt32BE(out[0] >>> 0, 0)
  buf.writeUInt32BE(out[1] >>> 0, 4)
  buf.writeUInt32BE(out[2] >>> 0, 8)
  buf.writeUInt32BE(out[3] >>> 0, 12)
  return buf
}

function GHASH (key) {
  this.h = key
  this.state = Buffer.alloc(16, 0)
  this.cache = Buffer.allocUnsafe(0)
}

// from http://bitwiseshiftleft.github.io/sjcl/doc/symbols/src/core_gcm.js.html
// by Juho Vähä-Herttua
GHASH.prototype.ghash = function (block) {
  var i = -1
  while (++i < block.length) {
    this.state[i] ^= block[i]
  }
  this._multiply()
}

GHASH.prototype._multiply = function () {
  var Vi = toArray(this.h)
  var Zi = [0, 0, 0, 0]
  var j, xi, lsbVi
  var i = -1
  while (++i < 128) {
    xi = (this.state[~~(i / 8)] & (1 << (7 - (i % 8)))) !== 0
    if (xi) {
      // Z_i+1 = Z_i ^ V_i
      Zi[0] ^= Vi[0]
      Zi[1] ^= Vi[1]
      Zi[2] ^= Vi[2]
      Zi[3] ^= Vi[3]
    }

    // Store the value of LSB(V_i)
    lsbVi = (Vi[3] & 1) !== 0

    // V_i+1 = V_i >> 1
    for (j = 3; j > 0; j--) {
      Vi[j] = (Vi[j] >>> 1) | ((Vi[j - 1] & 1) << 31)
    }
    Vi[0] = Vi[0] >>> 1

    // If LSB(V_i) is 1, V_i+1 = (V_i >> 1) ^ R
    if (lsbVi) {
      Vi[0] = Vi[0] ^ (0xe1 << 24)
    }
  }
  this.state = fromArray(Zi)
}

GHASH.prototype.update = function (buf) {
  this.cache = Buffer.concat([this.cache, buf])
  var chunk
  while (this.cache.length >= 16) {
    chunk = this.cache.slice(0, 16)
    this.cache = this.cache.slice(16)
    this.ghash(chunk)
  }
}

GHASH.prototype.final = function (abl, bl) {
  if (this.cache.length) {
    this.ghash(Buffer.concat([this.cache, ZEROES], 16))
  }

  this.ghash(fromArray([0, abl, 0, bl]))
  return this.state
}

module.exports = GHASH