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build/node_modules/public-encrypt/privateDecrypt.js

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