139 lines
3.8 KiB
JavaScript
139 lines
3.8 KiB
JavaScript
var Random = require('../random');
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// Cipher Block Chaining
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// http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher-block_chaining_.28CBC.29
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var CBC = function CBC(blockcipher, cipherkeybuf, ivbuf) {
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if (!(this instanceof CBC))
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return new CBC(blockcipher, cipherkeybuf, ivbuf);
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this.blockcipher = blockcipher;
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this.cipherkeybuf = cipherkeybuf;
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this.ivbuf = ivbuf;
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};
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CBC.buf2blockbufs = function(buf, blocksize) {
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var bytesize = blocksize / 8;
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var blockbufs = [];
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for (var i = 0; i <= buf.length / bytesize; i++) {
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var blockbuf = buf.slice(i * bytesize, i * bytesize + bytesize);
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if (blockbuf.length < blocksize)
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blockbuf = CBC.pkcs7pad(blockbuf, blocksize);
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blockbufs.push(blockbuf);
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}
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return blockbufs;
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};
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CBC.blockbufs2buf = function(blockbufs, blocksize) {
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var bytesize = blocksize / 8;
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var last = blockbufs[blockbufs.length - 1];
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last = CBC.pkcs7unpad(last);
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blockbufs[blockbufs.length - 1] = last;
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var buf = Buffer.concat(blockbufs);
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return buf;
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};
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CBC.encrypt = function(messagebuf, ivbuf, blockcipher, cipherkeybuf) {
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var blocksize = ivbuf.length * 8;
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var blockbufs = CBC.buf2blockbufs(messagebuf, blocksize);
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var encbufs = CBC.encryptblocks(blockbufs, ivbuf, blockcipher, cipherkeybuf);
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var encbuf = Buffer.concat(encbufs);
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return encbuf;
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};
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CBC.decrypt = function(encbuf, ivbuf, blockcipher, cipherkeybuf) {
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var blocksize = ivbuf.length * 8;
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var bytesize = ivbuf.length;
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var encbufs = [];
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for (var i = 0; i < encbuf.length / bytesize; i++) {
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encbufs.push(encbuf.slice(i * bytesize, i * bytesize + bytesize));
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}
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var blockbufs = CBC.decryptblocks(encbufs, ivbuf, blockcipher, cipherkeybuf);
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var buf = CBC.blockbufs2buf(blockbufs, blocksize);
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return buf;
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};
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CBC.encryptblock = function(blockbuf, ivbuf, blockcipher, cipherkeybuf) {
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var xorbuf = CBC.xorbufs(blockbuf, ivbuf);
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var encbuf = blockcipher.encrypt(xorbuf, cipherkeybuf);
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return encbuf;
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};
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CBC.decryptblock = function(encbuf, ivbuf, blockcipher, cipherkeybuf) {
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var xorbuf = blockcipher.decrypt(encbuf, cipherkeybuf);
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var blockbuf = CBC.xorbufs(xorbuf, ivbuf);
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return blockbuf;
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};
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CBC.encryptblocks = function(blockbufs, ivbuf, blockcipher, cipherkeybuf) {
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var encbufs = [];
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for (var i = 0; i < blockbufs.length; i++) {
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var blockbuf = blockbufs[i];
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var encbuf = CBC.encryptblock(blockbuf, ivbuf, blockcipher, cipherkeybuf);
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encbufs.push(encbuf);
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ivbuf = encbuf;
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}
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return encbufs;
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};
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CBC.decryptblocks = function(encbufs, ivbuf, blockcipher, cipherkeybuf) {
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var blockbufs = [];
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for (var i = 0; i < encbufs.length; i++) {
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var encbuf = encbufs[i];
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var blockbuf = CBC.decryptblock(encbuf, ivbuf, blockcipher, cipherkeybuf);
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blockbufs.push(blockbuf);
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ivbuf = encbuf;
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}
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return blockbufs;
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};
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CBC.pkcs7pad = function(buf, blocksize) {
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var bytesize = blocksize / 8;
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var padbytesize = bytesize - buf.length;
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var pad = new Buffer(padbytesize);
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pad.fill(padbytesize);
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var paddedbuf = Buffer.concat([buf, pad]);
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return paddedbuf;
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};
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CBC.pkcs7unpad = function(paddedbuf, blocksize) {
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var bytesize = blocksize / 8;
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var padbytesize = bytesize - paddedbuf.length;
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var padlength = paddedbuf[paddedbuf.length - 1];
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var padbuf = paddedbuf.slice(paddedbuf.length - padlength, paddedbuf.length);
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var padbuf2 = new Buffer(padlength);
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padbuf2.fill(padlength);
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if (padbuf.toString('hex') !== padbuf2.toString('hex'))
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throw new Error('invalid padding');
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return paddedbuf.slice(0, paddedbuf.length - padlength);
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};
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CBC.xorbufs = function(buf1, buf2) {
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if (buf1.length !== buf2.length)
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throw new Error('bufs must have the same length');
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var buf = new Buffer(buf1.length);
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for (var i = 0; i < buf1.length; i++) {
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buf[i] = buf1[i] ^ buf2[i];
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}
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return buf;
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};
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module.exports = CBC;
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