108 lines
2.5 KiB
JavaScript
108 lines
2.5 KiB
JavaScript
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var parseKeys = require('parse-asn1');
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var mgf = require('./mgf');
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var xor = require('./xor');
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var bn = require('bn.js');
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var crt = require('browserify-rsa');
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var createHash = require('create-hash');
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var withPublic = require('./withPublic');
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module.exports = function privateDecrypt(private_key, enc, reverse) {
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var padding;
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if (private_key.padding) {
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padding = private_key.padding;
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} else if (reverse) {
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padding = 1;
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} else {
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padding = 4;
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}
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var key = parseKeys(private_key);
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var k = key.modulus.byteLength();
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if (enc.length > k || new bn(enc).cmp(key.modulus) >= 0) {
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throw new Error('decryption error');
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}
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var msg;
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if (reverse) {
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msg = withPublic(new bn(enc), key);
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} else {
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msg = crt(enc, key);
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}
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var zBuffer = new Buffer(k - msg.length);
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zBuffer.fill(0);
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msg = Buffer.concat([zBuffer, msg], k);
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if (padding === 4) {
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return oaep(key, msg);
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} else if (padding === 1) {
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return pkcs1(key, msg, reverse);
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} else if (padding === 3) {
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return msg;
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} else {
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throw new Error('unknown padding');
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}
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};
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function oaep(key, msg){
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var n = key.modulus;
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var k = key.modulus.byteLength();
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var mLen = msg.length;
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var iHash = createHash('sha1').update(new Buffer('')).digest();
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var hLen = iHash.length;
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var hLen2 = 2 * hLen;
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if (msg[0] !== 0) {
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throw new Error('decryption error');
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}
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var maskedSeed = msg.slice(1, hLen + 1);
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var maskedDb = msg.slice(hLen + 1);
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var seed = xor(maskedSeed, mgf(maskedDb, hLen));
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var db = xor(maskedDb, mgf(seed, k - hLen - 1));
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if (compare(iHash, db.slice(0, hLen))) {
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throw new Error('decryption error');
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}
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var i = hLen;
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while (db[i] === 0) {
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i++;
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}
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if (db[i++] !== 1) {
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throw new Error('decryption error');
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}
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return db.slice(i);
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}
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function pkcs1(key, msg, reverse){
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var p1 = msg.slice(0, 2);
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var i = 2;
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var status = 0;
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while (msg[i++] !== 0) {
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if (i >= msg.length) {
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status++;
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break;
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}
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}
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var ps = msg.slice(2, i - 1);
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var p2 = msg.slice(i - 1, i);
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if ((p1.toString('hex') !== '0002' && !reverse) || (p1.toString('hex') !== '0001' && reverse)){
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status++;
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}
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if (ps.length < 8) {
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status++;
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}
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if (status) {
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throw new Error('decryption error');
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}
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return msg.slice(i);
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}
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function compare(a, b){
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a = new Buffer(a);
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b = new Buffer(b);
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var dif = 0;
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var len = a.length;
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if (a.length !== b.length) {
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dif++;
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len = Math.min(a.length, b.length);
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}
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var i = -1;
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while (++i < len) {
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dif += (a[i] ^ b[i]);
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}
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return dif;
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}
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