Change updater to use shared flx package.

This changes flutter's updater package to depend on and use the new flx
package. I also did a little cleanup of the Bundle interface.

packages/flx/lib/bundle.dart

@@ -7,7 +7,16 @@ import 'dart:convert';
 import 'dart:io';
 import 'dart:typed_data';
 
-const String kBundleMagic = '#!mojo ';
+import 'package:bignum/bignum.dart';
+
+import 'signing.dart';
+
+// Magic string we put at the top of all bundle files.
+const String kBundleMagic = '#!mojo mojo:sky_viewer\n';
+
+// Prefix of the above, used when reading bundle files. This allows us to be
+// more flexbile about what we accept.
+const String kBundleMagicPrefix = '#!mojo ';
 
 Future<List<int>> _readBytesWithLength(RandomAccessFile file) async {
   ByteData buffer = new ByteData(4);
@@ -29,6 +38,16 @@ Future<String> _readLine(RandomAccessFile file) async {
   return line;
 }
 
+// Writes a 32-bit length followed by the content of [bytes].
+void _writeBytesWithLengthSync(File outputFile, List<int> bytes) {
+  if (bytes == null)
+    bytes = new Uint8List(0);
+  assert(bytes.length < 0xffffffff);
+  ByteData length = new ByteData(4)..setUint32(0, bytes.length, Endianness.LITTLE_ENDIAN);
+  outputFile.writeAsBytesSync(length.buffer.asUint8List(), mode: FileMode.APPEND);
+  outputFile.writeAsBytesSync(bytes, mode: FileMode.APPEND);
+}
+
 // Represents a parsed .flx Bundle. Contains information from the bundle's
 // header, as well as an open File handle positioned where the zip content
 // begins.
@@ -46,30 +65,78 @@ Future<String> _readLine(RandomAccessFile file) async {
 //   ECDSA public key that was used to sign this manifest.
 // content-hash: an integer SHA-256 hash value of the <zip content>.
 class Bundle {
-  Bundle(this.path);
+  Bundle._fromFile(this.path);
+  Bundle.fromContent({
+    this.path,
+    this.manifest,
+    contentBytes,
+    KeyPair keyPair: null
+  }) : _contentBytes = contentBytes {
+    assert(path != null);
+    assert(manifest != null);
+    assert(_contentBytes != null);
+    manifestBytes = serializeManifest(manifest, keyPair?.publicKey, _contentBytes);
+    signatureBytes = signManifest(manifestBytes, keyPair?.privateKey);
+  }
 
   final String path;
   List<int> signatureBytes;
   List<int> manifestBytes;
   Map<String, dynamic> manifest;
-  RandomAccessFile content;
+
+  // File byte offset of the start of the zip content. Only valid when opened
+  // from a file.
+  int _contentOffset;
+
+  // Zip content bytes. Only valid when created in memory.
+  List<int> _contentBytes;
 
   Future<bool> _readHeader() async {
-    content = await new File(path).open();
-    String magic = await _readLine(content);
-    if (!magic.startsWith(kBundleMagic))
+    RandomAccessFile file = await new File(path).open();
+    String magic = await _readLine(file);
+    if (!magic.startsWith(kBundleMagicPrefix)) {
+      file.close();
       return false;
-    signatureBytes = await _readBytesWithLength(content);
-    manifestBytes = await _readBytesWithLength(content);
+    }
+    signatureBytes = await _readBytesWithLength(file);
+    manifestBytes = await _readBytesWithLength(file);
+    _contentOffset = await file.position();
+    file.close();
+
     String manifestString = UTF8.decode(manifestBytes);
     manifest = JSON.decode(manifestString);
     return true;
   }
 
   static Future<Bundle> readHeader(String path) async {
-    Bundle bundle = new Bundle(path);
+    Bundle bundle = new Bundle._fromFile(path);
     if (!await bundle._readHeader())
       return null;
     return bundle;
   }
+
+  // When opened from a file, verifies that the package has a valid signature
+  // and content.
+  Future<bool> verifyContent() async {
+    assert(_contentOffset != null);
+    if (!verifyManifestSignature(manifest, manifestBytes, signatureBytes))
+      return false;
+
+    Stream<List<int>> content = await new File(path).openRead(_contentOffset);
+    BigInteger expectedHash = new BigInteger(manifest['content-hash'], 10);
+    if (!await verifyContentHash(expectedHash, content))
+      return false;
+
+    return true;
+  }
+
+  // Writes the in-memory representation to disk.
+  void writeSync() {
+    assert(_contentBytes != null);
+    File outputFile = new File(path);
+    outputFile.writeAsStringSync('#!mojo mojo:sky_viewer\n');
+    _writeBytesWithLengthSync(outputFile, signatureBytes);
+    _writeBytesWithLengthSync(outputFile, manifestBytes);
+    outputFile.writeAsBytesSync(_contentBytes, mode: FileMode.APPEND, flush: true);
+  }
 }

packages/flx/lib/signing.dart

@@ -4,20 +4,23 @@
 
 import 'dart:async';
 import 'dart:convert';
+import 'dart:math';
 import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:asn1lib/asn1lib.dart';
 import 'package:bignum/bignum.dart';
 import 'package:cipher/cipher.dart';
+import 'package:cipher/impl/client.dart';
 
 // The ECDSA algorithm parameters we're using. These match the parameters used
 // by the Flutter updater package.
-final ECDomainParameters _ecDomain = new ECDomainParameters('prime256v1');
-final String kSignerAlgorithm = 'SHA-256/ECDSA';
-final String kHashAlgorithm = 'SHA-256';
-
-final SecureRandom _random = _initRandom();
+class CipherParameters {
+  final String signerAlgorithm = 'SHA-256/ECDSA';
+  final String hashAlgorithm = 'SHA-256';
+  final ECDomainParameters domain = new ECDomainParameters('prime256v1');
+  final SecureRandom random = _initRandom();
+}
 
 SecureRandom _initRandom() {
   // TODO(mpcomplete): Provide a better seed here. External entropy source?
@@ -29,6 +32,13 @@ SecureRandom _initRandom() {
   return random;
 }
 
+CipherParameters _initParams() {
+  initCipher();
+  return new CipherParameters();
+}
+
+final CipherParameters _params = _initParams();
+
 // Returns a serialized manifest, with the public key and hash of the content
 // included.
 Uint8List serializeManifest(Map manifestDescriptor, ECPublicKey publicKey, Uint8List zipBytes) {
@@ -48,7 +58,7 @@ Uint8List serializeManifest(Map manifestDescriptor, ECPublicKey publicKey, Uint8
   if (publicKey != null)
     outputManifest['key'] = BASE64.encode(publicKey.Q.getEncoded());
 
-  Uint8List zipHash = new Digest(kHashAlgorithm).process(zipBytes);
+  Uint8List zipHash = new Digest(_params.hashAlgorithm).process(zipBytes);
   BigInteger zipHashInt = new BigInteger.fromBytes(1, zipHash);
   outputManifest['content-hash'] = zipHashInt.intValue();
 
@@ -59,9 +69,9 @@ Uint8List serializeManifest(Map manifestDescriptor, ECPublicKey publicKey, Uint8
 List<int> signManifest(Uint8List manifestBytes, ECPrivateKey privateKey) {
   if (manifestBytes == null || privateKey == null)
     return [];
-  Signer signer = new Signer(kSignerAlgorithm);
+  Signer signer = new Signer(_params.signerAlgorithm);
   PrivateKeyParameter params = new PrivateKeyParameter(privateKey);
-  signer.init(true, new ParametersWithRandom(params, _random));
+  signer.init(true, new ParametersWithRandom(params, _params.random));
   ECSignature signature = signer.generateSignature(manifestBytes);
   ASN1Sequence asn1 = new ASN1Sequence()
     ..add(new ASN1Integer(signature.r))
@@ -69,6 +79,37 @@ List<int> signManifest(Uint8List manifestBytes, ECPrivateKey privateKey) {
   return asn1.encodedBytes;
 }
 
+bool verifyManifestSignature(Map<String, dynamic> manifest,
+                             Uint8List manifestBytes,
+                             Uint8List signatureBytes) {
+  ECSignature signature = _asn1ParseSignature(signatureBytes);
+  if (signature == null)
+    return false;
+
+  List<int> keyBytes = BASE64.decode(manifest['key']);
+  ECPoint q = _params.domain.curve.decodePoint(keyBytes);
+  ECPublicKey publicKey = new ECPublicKey(q, _params.domain);
+
+  Signer signer = new Signer(_params.signerAlgorithm);
+  signer.init(false, new PublicKeyParameter(publicKey));
+  return signer.verifySignature(manifestBytes, signature);
+}
+
+Future<bool> verifyContentHash(BigInteger expectedHash, Stream<List<int>> content) async {
+  // Hash the file incrementally.
+  Digest hasher = new Digest(_params.hashAlgorithm);
+  await content.forEach((List<int> chunk) {
+    hasher.update(chunk, 0, chunk.length);
+  });
+  Uint8List hashBytes = new Uint8List(hasher.digestSize);
+  int len = hasher.doFinal(hashBytes, 0);
+  hashBytes = hashBytes.sublist(0, len);
+  BigInteger actualHash = new BigInteger.fromBytes(1, hashBytes);
+
+  return expectedHash == actualHash;
+}
+
+// Parses a DER-encoded ASN.1 ECDSA private key block.
 ECPrivateKey _asn1ParsePrivateKey(ECDomainParameters ecDomain, Uint8List privateKey) {
   ASN1Parser parser = new ASN1Parser(privateKey);
   ASN1Sequence seq = parser.nextObject();
@@ -78,17 +119,47 @@ ECPrivateKey _asn1ParsePrivateKey(ECDomainParameters ecDomain, Uint8List private
   return new ECPrivateKey(d, ecDomain);
 }
 
-Future<ECPrivateKey> loadPrivateKey(String privateKeyPath) async {
+// Parses a DER-encoded ASN.1 ECDSA signature block.
+ECSignature _asn1ParseSignature(Uint8List signature) {
+  ASN1Parser parser = new ASN1Parser(signature);
+  ASN1Object object = parser.nextObject();
+  if (object is! ASN1Sequence)
+    return null;
+  ASN1Sequence sequence = object;
+  if (!(sequence.elements.length == 2 &&
+        sequence.elements[0] is ASN1Integer &&
+        sequence.elements[1] is ASN1Integer))
+    return null;
+  ASN1Integer r = sequence.elements[0];
+  ASN1Integer s = sequence.elements[1];
+  return new ECSignature(r.valueAsPositiveBigInteger, s.valueAsPositiveBigInteger);
+}
+
+ECPrivateKey _readPrivateKeySync(String privateKeyPath) {
   File file = new File(privateKeyPath);
   if (!file.existsSync())
     return null;
   List<int> bytes = file.readAsBytesSync();
-  return _asn1ParsePrivateKey(_ecDomain, new Uint8List.fromList(bytes));
+  return _asn1ParsePrivateKey(_params.domain, new Uint8List.fromList(bytes));
 }
 
-ECPublicKey publicKeyFromPrivateKey(ECPrivateKey privateKey) {
-  if (privateKey == null)
-    return null;
+ECPublicKey _publicKeyFromPrivateKey(ECPrivateKey privateKey) {
   ECPoint Q = privateKey.parameters.G * privateKey.d;
   return new ECPublicKey(Q, privateKey.parameters);
 }
+
+class KeyPair {
+  KeyPair(this.publicKey, this.privateKey);
+
+  ECPublicKey publicKey;
+  ECPrivateKey privateKey;
+
+  static KeyPair readFromPrivateKeySync(String path) {
+    ECPrivateKey privateKey = _readPrivateKeySync(path);
+    if (privateKey == null)
+      return null;
+
+    ECPublicKey publicKey = _publicKeyFromPrivateKey(privateKey);
+    return new KeyPair(publicKey, privateKey);
+  }
+}

packages/flx/pubspec.yaml

@@ -4,7 +4,7 @@ author: Flutter Authors <flutter-dev@googlegroups.com>
 description: Library for dealing with Flutter bundle (.flx) files
 homepage: http://flutter.io
 dependencies:
-  sky_services: 0.0.38
+  sky_services: ^0.0.40
   yaml: ^2.1.3
   asn1lib: ^0.4.1
   cipher: ^0.7.1

packages/updater/lib/bundle.dart

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'dart:async';
-import 'dart:convert';
-import 'dart:io';
-import 'dart:typed_data';
-
-const String kBundleMagic = '#!mojo ';
-
-Future<List<int>> _readBytesWithLength(RandomAccessFile file) async {
-  ByteData buffer = new ByteData(4);
-  await file.readInto(buffer.buffer.asUint8List());
-  int length = buffer.getUint32(0, Endianness.LITTLE_ENDIAN);
-  return await file.read(length);
-}
-
-const int kMaxLineLen = 10*1024;
-const int kNewline = 0x0A;
-Future<String> _readLine(RandomAccessFile file) async {
-  String line = '';
-  while (line.length < kMaxLineLen) {
-    int byte = await file.readByte();
-    if (byte == -1 || byte == kNewline)
-      break;
-    line += new String.fromCharCode(byte);
-  }
-  return line;
-}
-
-// Represents a parsed .flx Bundle. Contains information from the bundle's
-// header, as well as an open File handle positioned where the zip content
-// begins.
-// The bundle format is:
-// #!mojo <any string>\n
-// <32-bit length><signature of the manifest data>
-// <32-bit length><manifest data>
-// <zip content>
-//
-// The manifest is a JSON string containing the following keys:
-// (optional) name: the name of the package.
-// version: the package version.
-// update-url: the base URL to download a new manifest and bundle.
-// key: a BASE-64 encoded DER-encoded ASN.1 representation of the Q point of the
-//   ECDSA public key that was used to sign this manifest.
-// content-hash: an integer SHA-256 hash value of the <zip content>.
-class Bundle {
-  Bundle(this.path);
-
-  final String path;
-  List<int> signatureBytes;
-  List<int> manifestBytes;
-  Map<String, dynamic> manifest;
-  RandomAccessFile content;
-
-  Future<bool> _readHeader() async {
-    content = await new File(path).open();
-    String magic = await _readLine(content);
-    if (!magic.startsWith(kBundleMagic))
-      return false;
-    signatureBytes = await _readBytesWithLength(content);
-    manifestBytes = await _readBytesWithLength(content);
-    String manifestString = UTF8.decode(manifestBytes);
-    manifest = JSON.decode(manifestString);
-    return true;
-  }
-
-  static Future<Bundle> readHeader(String path) async {
-    Bundle bundle = new Bundle(path);
-    if (!await bundle._readHeader())
-      return null;
-    return bundle;
-  }
-}

packages/updater/lib/main.dart

@@ -9,33 +9,18 @@ import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:mojo/core.dart';
-// TODO(mpcomplete): Remove this 'hide' when we remove the conflicting
-// UpdateService from activity.mojom.
-import 'package:flutter/services.dart' hide UpdateServiceProxy;
+import 'package:flutter/services.dart';
+import 'package:flx/bundle.dart';
 import 'package:sky_services/updater/update_service.mojom.dart';
 import 'package:path/path.dart' as path;
 import 'package:yaml/yaml.dart' as yaml;
-import 'package:asn1lib/asn1lib.dart';
-import 'package:bignum/bignum.dart';
-import 'package:cipher/cipher.dart';
-import 'package:cipher/impl/client.dart';
 
-import 'bundle.dart';
 import 'pipe_to_file.dart';
 import 'version.dart';
 
 const String kManifestFile = 'sky.yaml';
 const String kBundleFile = 'app.flx';
 
-// Number of bytes to read at a time from a file.
-const int kReadBlockSize = 32*1024;
-
-// The ECDSA algorithm parameters we're using. These match the parameters used
-// by the signing tool in flutter_tools.
-final ECDomainParameters _ecDomain = new ECDomainParameters('prime256v1');
-final String kSignerAlgorithm = 'SHA-256/ECDSA';
-final String kHashAlgorithm = 'SHA-256';
-
 UpdateServiceProxy _initUpdateService() {
   UpdateServiceProxy updateService = new UpdateServiceProxy.unbound();
   shell.requestService(null, updateService);
@@ -51,22 +36,6 @@ Future<String> getDataDir() async {
   return cachedDataDir;
 }
 
-// Parses a DER-encoded ASN.1 ECDSA signature block.
-ECSignature _asn1ParseSignature(Uint8List signature) {
-  ASN1Parser parser = new ASN1Parser(signature);
-  ASN1Object object = parser.nextObject();
-  if (object is! ASN1Sequence)
-    return null;
-  ASN1Sequence sequence = object;
-  if (!(sequence.elements.length == 2 &&
-        sequence.elements[0] is ASN1Integer &&
-        sequence.elements[1] is ASN1Integer))
-    return null;
-  ASN1Integer r = sequence.elements[0];
-  ASN1Integer s = sequence.elements[1];
-  return new ECSignature(r.valueAsPositiveBigInteger, s.valueAsPositiveBigInteger);
-}
-
 class UpdateFailure extends Error {
   UpdateFailure(this._message);
   String _message;
@@ -112,7 +81,6 @@ class UpdateTask {
     String bundlePath = path.join(_dataDir, kBundleFile);
     Bundle bundle = await Bundle.readHeader(bundlePath);
     _currentManifest = bundle.manifest;
-    bundle.content.close();
   }
 
   Future<yaml.YamlMap> _fetchManifest() async {
@@ -144,47 +112,8 @@ class UpdateTask {
       throw new UpdateFailure('Remote package not a valid FLX file.');
     if (bundle.manifest['key'] != _currentManifest['key'])
       throw new UpdateFailure('Remote package key does not match.');
-
-    await _verifyManifestSignature(bundle);
-    await _verifyContentHash(bundle);
-
-    bundle.content.close();
-  }
-
-  Future _verifyManifestSignature(Bundle bundle) async {
-    ECSignature ecSignature = _asn1ParseSignature(bundle.signatureBytes);
-    if (ecSignature == null)
-      throw new UpdateFailure('Corrupt package signature.');
-
-    List keyBytes = BASE64.decode(_currentManifest['key']);
-    ECPoint q = _ecDomain.curve.decodePoint(keyBytes);
-    ECPublicKey ecPublicKey = new ECPublicKey(q, _ecDomain);
-
-    Signer signer = new Signer(kSignerAlgorithm);
-    signer.init(false, new PublicKeyParameter(ecPublicKey));
-    if (!signer.verifySignature(bundle.manifestBytes, ecSignature))
-      throw new UpdateFailure('Invalid package signature. This package has been tampered with.');
-  }
-
-  Future _verifyContentHash(Bundle bundle) async {
-    // Hash the bundle contents.
-    Digest hasher = new Digest(kHashAlgorithm);
-    RandomAccessFile content = bundle.content;
-    int remainingLen = await content.length() - await content.position();
-    while (remainingLen > 0) {
-      List<int> chunk = await content.read(min(remainingLen, kReadBlockSize));
-      hasher.update(chunk, 0, chunk.length);
-      remainingLen -= chunk.length;
-    }
-    Uint8List hashBytes = new Uint8List(hasher.digestSize);
-    int len = hasher.doFinal(hashBytes, 0);
-    hashBytes = hashBytes.sublist(0, len);
-    BigInteger actualHash = new BigInteger.fromBytes(1, hashBytes);
-
-    // Compare to our expected hash from the manifest.
-    BigInteger expectedHash = new BigInteger(bundle.manifest['content-hash'], 10);
-    if (expectedHash != actualHash)
-      throw new UpdateFailure('Invalid package content hash. This package has been tampered with.');
+    if (!await bundle.verifyContent())
+      throw new UpdateFailure('Invalid package signature or hash. This package has been tampered with.');
   }
 
   Future _replaceBundle() async {
@@ -194,7 +123,6 @@ class UpdateTask {
 }
 
 void main() {
-  initCipher();
   UpdateTask task = new UpdateTask();
   task.run();
 }

packages/updater/pubspec.yaml

@@ -6,13 +6,14 @@ homepage: http://flutter.io
 dependencies:
   mojo: 0.3.0
   flutter: ">=0.0.3 <0.1.0"
-  sky_services: any
-  path: any
-  yaml: any
-  cipher: any
-  asn1lib: any
+  sky_services: ^0.0.40
+  yaml: ^2.1.3
+  path: ^1.3.0
+  flx: 0.0.1
 dependency_overrides:
   flutter:
     path: ../sky
+  flx:
+    path: ../flx
 environment:
   sdk: '>=1.12.0 <2.0.0'