nilsteampassnet / TeamPass

'use strict';

if (typeof module!='undefined' && module.exports) var Aes = require('./aes.js'); // ≡ import Aes from 'aes.js'

/**

 * Aes.Ctr: Counter-mode (CTR) wrapper for AES.

 *

 * This encrypts a Unicode string to produces a base64 ciphertext using 128/192/256-bit AES,

 * and the converse to decrypt an encrypted ciphertext.

 *

 * See http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf

 *

 * @augments Aes

 */

Aes.Ctr = {};

/**

 * Encrypt a text using AES encryption in Counter mode of operation.

 *

 * Unicode multi-byte character safe

 *

 * @param   {string} plaintext - Source text to be encrypted.

 * @param   {string} password - The password to use to generate a key for encryption.

 * @param   {number} nBits - Number of bits to be used in the key; 128 / 192 / 256.

 * @returns {string} Encrypted text.

 *

 * @example

 *   var encr = Aes.Ctr.encrypt('big secret', 'pāşšŵōřđ', 256); // 'lwGl66VVwVObKIr6of8HVqJr'

 */

Aes.Ctr.encrypt = function(plaintext, password, nBits) {

    var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES

    if (!(nBits==128 || nBits==192 || nBits==256)) throw new Error('Key size is not 128 / 192 / 256');

    plaintext = String(plaintext).utf8Encode();

    password = String(password).utf8Encode();

    // use AES itself to encrypt password to get cipher key (using plain password as source for key

    // expansion) - gives us well encrypted key (though hashed key might be preferred for prod'n use)

    var nBytes = nBits/8;  // no bytes in key (16/24/32)

    var pwBytes = new Array(nBytes);

    for (var i=0; i<nBytes; i++) {  // use 1st 16/24/32 chars of password for key

        pwBytes[i] = i<password.length ?  password.charCodeAt(i) : 0;

    }

    var key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes)); // gives us 16-byte key

    key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long

    // initialise 1st 8 bytes of counter block with nonce (NIST SP800-38A §B.2): [0-1] = millisec,

    // [2-3] = random, [4-7] = seconds, together giving full sub-millisec uniqueness up to Feb 2106

    var counterBlock = new Array(blockSize);

    var nonce = (new Date()).getTime();  // timestamp: milliseconds since 1-Jan-1970

    var nonceMs = nonce%1000;

    var nonceSec = Math.floor(nonce/1000);

    var nonceRnd = Math.floor(Math.random()*0xffff);

    // for debugging: nonce = nonceMs = nonceSec = nonceRnd = 0;

    for (var i=0; i<2; i++) counterBlock[i]   = (nonceMs  >>> i*8) & 0xff;

    for (var i=0; i<2; i++) counterBlock[i+2] = (nonceRnd >>> i*8) & 0xff;

    for (var i=0; i<4; i++) counterBlock[i+4] = (nonceSec >>> i*8) & 0xff;

    // and convert it to a string to go on the front of the ciphertext

    var ctrTxt = '';

    for (var i=0; i<8; i++) ctrTxt += String.fromCharCode(counterBlock[i]);

    // generate key schedule - an expansion of the key into distinct Key Rounds for each round

    var keySchedule = Aes.keyExpansion(key);

    var blockCount = Math.ceil(plaintext.length/blockSize);

    var ciphertext = '';

    for (var b=0; b<blockCount; b++) {

        // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)

        // done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB)

        for (var c=0; c<4; c++) counterBlock[15-c] = (b >>> c*8) & 0xff;

        for (var c=0; c<4; c++) counterBlock[15-c-4] = (b/0x100000000 >>> c*8);

        var cipherCntr = Aes.cipher(counterBlock, keySchedule);  // -- encrypt counter block --

        // block size is reduced on final block

        var blockLength = b<blockCount-1 ? blockSize : (plaintext.length-1)%blockSize+1;

        var cipherChar = new Array(blockLength);

        for (var i=0; i<blockLength; i++) {

            // -- xor plaintext with ciphered counter char-by-char --

            cipherChar[i] = cipherCntr[i] ^ plaintext.charCodeAt(b*blockSize+i);

            cipherChar[i] = String.fromCharCode(cipherChar[i]);

        }

        ciphertext += cipherChar.join('');

        // if within web worker, announce progress every 1000 blocks (roughly every 50ms)

        if (typeof WorkerGlobalScope != 'undefined' && self instanceof WorkerGlobalScope) {

            if (b%1000 == 0) self.postMessage({ progress: b/blockCount });

        }

    }

    ciphertext =  (ctrTxt+ciphertext).base64Encode();

    return ciphertext;

};

/**

 * Decrypt a text encrypted by AES in counter mode of operation

 *

 * @param   {string} ciphertext - Cipher text to be decrypted.

 * @param   {string} password - Password to use to generate a key for decryption.

 * @param   {number} nBits - Number of bits to be used in the key; 128 / 192 / 256.

 * @returns {string} Decrypted text

 *

 * @example

 *   var decr = Aes.Ctr.decrypt('lwGl66VVwVObKIr6of8HVqJr', 'pāşšŵōřđ', 256); // 'big secret'

 */

Aes.Ctr.decrypt = function(ciphertext, password, nBits) {

    var blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES

    if (!(nBits==128 || nBits==192 || nBits==256)) throw new Error('Key size is not 128 / 192 / 256');

    ciphertext = String(ciphertext).base64Decode();

    password = String(password).utf8Encode();

    // use AES to encrypt password (mirroring encrypt routine)

    var nBytes = nBits/8;  // no bytes in key

    var pwBytes = new Array(nBytes);

    for (var i=0; i<nBytes; i++) {

        pwBytes[i] = i<password.length ?  password.charCodeAt(i) : 0;

    }

    var key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes));

    key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long

    // recover nonce from 1st 8 bytes of ciphertext

    var counterBlock = new Array(8);

    var ctrTxt = ciphertext.slice(0, 8);

    for (var i=0; i<8; i++) counterBlock[i] = ctrTxt.charCodeAt(i);

    // generate key schedule

    var keySchedule = Aes.keyExpansion(key);

    // separate ciphertext into blocks (skipping past initial 8 bytes)

    var nBlocks = Math.ceil((ciphertext.length-8) / blockSize);

    var ct = new Array(nBlocks);

    for (var b=0; b<nBlocks; b++) ct[b] = ciphertext.slice(8+b*blockSize, 8+b*blockSize+blockSize);

    ciphertext = ct;  // ciphertext is now array of block-length strings

    // plaintext will get generated block-by-block into array of block-length strings

    var plaintext = '';

    for (var b=0; b<nBlocks; b++) {

        // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)

        for (var c=0; c<4; c++) counterBlock[15-c] = ((b) >>> c*8) & 0xff;

        for (var c=0; c<4; c++) counterBlock[15-c-4] = (((b+1)/0x100000000-1) >>> c*8) & 0xff;

        var cipherCntr = Aes.cipher(counterBlock, keySchedule);  // encrypt counter block

        var plaintxtByte = new Array(ciphertext[b].length);

        for (var i=0; i<ciphertext[b].length; i++) {

            // -- xor plaintext with ciphered counter byte-by-byte --

            plaintxtByte[i] = cipherCntr[i] ^ ciphertext[b].charCodeAt(i);

            plaintxtByte[i] = String.fromCharCode(plaintxtByte[i]);

        }

        plaintext += plaintxtByte.join('');

        // if within web worker, announce progress every 1000 blocks (roughly every 50ms)

        if (typeof WorkerGlobalScope != 'undefined' && self instanceof WorkerGlobalScope) {

            if (b%1000 == 0) self.postMessage({ progress: b/nBlocks });

        }

    }

    plaintext = plaintext.utf8Decode();  // decode from UTF8 back to Unicode multi-byte chars

    return plaintext;

};

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

/* Extend String object with method to encode multi-byte string to utf8

 * - monsur.hossa.in/2012/07/20/utf-8-in-javascript.html

 * - note utf8Encode is an identity function with 7-bit ascii strings, but not with 8-bit strings;

 * - utf8Encode('x') = 'x', but utf8Encode('ça') = 'ça', and utf8Encode('ça') = 'ça'*/

if (typeof String.prototype.utf8Encode == 'undefined') {

    String.prototype.utf8Encode = function() {

        return unescape( encodeURIComponent( this ) );

    };

}

/* Extend String object with method to decode utf8 string to multi-byte */

if (typeof String.prototype.utf8Decode == 'undefined') {

    String.prototype.utf8Decode = function() {

        try {

            return decodeURIComponent( escape( this ) );

        } catch (e) {

            return this; // invalid UTF-8? return as-is

        }

    };

}

/* Extend String object with method to encode base64

 * - developer.mozilla.org/en-US/docs/Web/API/window.btoa, nodejs.org/api/buffer.html

 * - note: btoa & Buffer/binary work on single-byte Unicode (C0/C1), so ok for utf8 strings, not for general Unicode...

 * - note: if btoa()/atob() are not available (eg IE9-), try github.com/davidchambers/Base64.js */

if (typeof String.prototype.base64Encode == 'undefined') {

    String.prototype.base64Encode = function() {

        if (typeof btoa != 'undefined') return btoa(this); // browser

        if (typeof Buffer != 'undefined') return new Buffer(this, 'binary').toString('base64'); // Node.js

        throw new Error('No Base64 Encode');

    };

}

/* Extend String object with method to decode base64 */

if (typeof String.prototype.base64Decode == 'undefined') {

    String.prototype.base64Decode = function() {

        if (typeof atob != 'undefined') return atob(this); // browser

        if (typeof Buffer != 'undefined') return new Buffer(this, 'base64').toString('binary'); // Node.js

        throw new Error('No Base64 Decode');

    };

}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

if (typeof module != 'undefined' && module.exports) module.exports = Aes.Ctr; // ≡ export default Aes.Ctr