HDKeys: Modified to have immutable properties

lib/hdprivatekey.js

@@ -306,7 +306,10 @@ HDPrivateKey.prototype._buildFromBuffers = function(arg) {
   /* jshint maxstatements: 20 */
 
   HDPrivateKey._validateBufferArguments(arg);
-  this._buffers = arg;
+  Object.defineProperty(this, '_buffers', {
+    configurable: false,
+    value: arg
+  });
 
   var sequence = [
     arg.version, arg.depth, arg.parentFingerPrint, arg.childIndex, arg.chainCode,
@@ -321,21 +324,35 @@ HDPrivateKey.prototype._buildFromBuffers = function(arg) {
     }
   }
 
+  var xprivkey;
+
   if (!arg.xprivkey) {
-    this.xprivkey = Base58Check.encode(buffer.Buffer.concat(sequence));
+    xprivkey = Base58Check.encode(buffer.Buffer.concat(sequence));
   } else {
-    this.xprivkey = arg.xprivkey;
+    xprivkey = arg.xprivkey;
   }
-  this.network = Network.get(bufferUtil.integerFromBuffer(arg.version));
-  this.depth = bufferUtil.integerFromSingleByteBuffer(arg.depth);
-  this.privateKey = new PrivateKey(BN().fromBuffer(arg.privateKey));
-  this.publicKey = this.privateKey.toPublicKey();
 
-  this.fingerPrint = Hash.sha256ripemd160(this.publicKey.toBuffer()).slice(0, HDPrivateKey.ParentFingerPrintSize);
+  var privateKey = new PrivateKey(BN().fromBuffer(arg.privateKey));
+  var publicKey = privateKey.toPublicKey();
+  var size = HDPrivateKey.ParentFingerPrintSize;
+  var fingerPrint = Hash.sha256ripemd160(publicKey.toBuffer()).slice(0, size);
+
+  jsUtil.defineImmutable(this, {
+    xprivkey: xprivkey,
+    network: Network.get(bufferUtil.integerFromBuffer(arg.version)),
+    depth: bufferUtil.integerFromSingleByteBuffer(arg.depth),
+    privateKey: privateKey,
+    publicKey: publicKey,
+    fingerPrint: fingerPrint
+  });
 
   var HDPublicKey = require('./hdpublickey');
-  this.hdPublicKey = new HDPublicKey(this);
-  this.xpubkey = this.hdPublicKey.xpubkey;
+  var hdPublicKey = new HDPublicKey(this);
+
+  jsUtil.defineImmutable(this, {
+    hdPublicKey: hdPublicKey,
+    xpubkey: hdPublicKey.xpubkey
+  });
 
   return this;
 };

lib/hdpublickey.js

@@ -279,7 +279,11 @@ HDPublicKey.prototype._buildFromBuffers = function (arg) {
   /* jshint maxstatements: 20 */
 
   HDPublicKey._validateBufferArguments(arg);
-  this._buffers = arg;
+
+  Object.defineProperty(this, '_buffers', {
+    configurable: false,
+    value: arg
+  });
 
   var sequence = [
     arg.version, arg.depth, arg.parentFingerPrint, arg.childIndex, arg.chainCode,
@@ -295,16 +299,25 @@ HDPublicKey.prototype._buildFromBuffers = function (arg) {
     }
   }
 
+  var xpubkey;
+
   if (!arg.xpubkey) {
-    this.xpubkey = Base58Check.encode(bufferUtil.concat(sequence));
+    xpubkey = Base58Check.encode(bufferUtil.concat(sequence));
   } else {
-    this.xpubkey = arg.xpubkey;
+    xpubkey = arg.xpubkey;
   }
 
-  this.network = Network.get(bufferUtil.integerFromBuffer(arg.version));
-  this.depth = bufferUtil.integerFromSingleByteBuffer(arg.depth);
-  this.publicKey = PublicKey.fromString(arg.publicKey);
-  this.fingerPrint = Hash.sha256ripemd160(this.publicKey.toBuffer()).slice(0, HDPublicKey.ParentFingerPrintSize);
+  var publicKey = PublicKey.fromString(arg.publicKey);
+  var size = HDPublicKey.ParentFingerPrintSize;
+  var fingerPrint = Hash.sha256ripemd160(publicKey.toBuffer()).slice(0, size);
+
+  jsUtil.defineImmutable(this, {
+    xpubkey: xpubkey,
+    network: Network.get(bufferUtil.integerFromBuffer(arg.version)),
+    depth: bufferUtil.integerFromSingleByteBuffer(arg.depth),
+    publicKey: publicKey,
+    fingerPrint: fingerPrint
+  });
 
   return this;
 };

lib/util/js.js

@@ -31,5 +31,22 @@ module.exports = {
     }
   },
   isHexa: isHexa,
-  isHexaString: isHexa
+  isHexaString: isHexa,
+
+  /**
+   * Define immutable properties on a target object
+   *
+   * @param {Object} target - An object to be extended
+   * @param {Object} values - An object of properties
+   * @return {Object} The target object
+   */
+  defineImmutable: function defineImmutable(target, values){
+    Object.keys(values).forEach(function(key){
+      Object.defineProperty(target, key, {
+        configurable: false,
+        value: values[key]
+      });
+    });
+    return target;
+  }
 };

test/hdprivatekey.js

@@ -50,6 +50,13 @@ describe('HDPrivate key interface', function() {
     should.exist(new HDPrivateKey().xprivkey);
   });
 
+  it('should not be able to change read-only properties', function() {
+    var hdkey = new HDPrivateKey();
+    expect(function() {
+      hdkey.fingerPrint = 'notafingerprint';
+    }).to.throw(TypeError);
+  });
+
   it('should error with an invalid checksum', function() {
     expectFailBuilding(xprivkey + '1', errors.InvalidB58Checksum);
   });

test/hdpublickey.js

@@ -69,6 +69,13 @@ describe('HDPublicKey interface', function() {
       expectFailBuilding(null, hdErrors.MustSupplyArgument);
     });
 
+    it('should not be able to change read-only properties', function() {
+      var publicKey = new HDPublicKey(xprivkey);
+      expect(function() {
+        publicKey.fingerPrint = 'notafingerprint';
+      }).to.throw(TypeError);
+    });
+
     it('doesn\'t recognize an invalid argument', function() {
       expectFailBuilding(1, hdErrors.UnrecognizedArgument);
       expectFailBuilding(true, hdErrors.UnrecognizedArgument);