Downloading and installation of dynamic updates on Android

ci/licenses_golden/licenses_flutter

@@ -454,6 +454,7 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/view/FlutterView.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/view/ResourceCleaner.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/view/ResourceExtractor.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/view/ResourcePaths.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/view/ResourceUpdater.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/view/TextureRegistry.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/view/VsyncWaiter.java
 FILE: ../../../flutter/shell/platform/android/library_loader.cc

shell/platform/android/BUILD.gn

@@ -140,6 +140,7 @@ java_library("flutter_shell_java") {
     "io/flutter/view/ResourceCleaner.java",
     "io/flutter/view/ResourceExtractor.java",
     "io/flutter/view/ResourcePaths.java",
+    "io/flutter/view/ResourceUpdater.java",
     "io/flutter/view/TextureRegistry.java",
     "io/flutter/view/VsyncWaiter.java",
   ]

shell/platform/android/io/flutter/app/FlutterActivityDelegate.java

@@ -166,11 +166,17 @@ public void onCreate(Bundle savedInstanceState) {
         if (loadIntent(activity.getIntent())) {
             return;
         }
+
         if (!flutterView.getFlutterNativeView().isApplicationRunning()) {
           String appBundlePath = FlutterMain.findAppBundlePath(activity.getApplicationContext());
           if (appBundlePath != null) {
             FlutterRunArguments arguments = new FlutterRunArguments();
-            arguments.bundlePath = appBundlePath;
+            ArrayList<String> bundlePaths = new ArrayList<String>();
+            if (FlutterMain.getUpdateInstallationPath() != null) {
+                bundlePaths.add(FlutterMain.getUpdateInstallationPath());
+            }
+            bundlePaths.add(appBundlePath);
+            arguments.bundlePaths = bundlePaths.toArray(new String[0]);
             arguments.entrypoint = "main";
             flutterView.runFromBundle(arguments);
           }
@@ -337,7 +343,12 @@ private boolean loadIntent(Intent intent) {
             }
             if (!flutterView.getFlutterNativeView().isApplicationRunning()) {
               FlutterRunArguments args = new FlutterRunArguments();
-              args.bundlePath = appBundlePath;
+              ArrayList<String> bundlePaths = new ArrayList<String>();
+              if (FlutterMain.getUpdateInstallationPath() != null) {
+                  bundlePaths.add(FlutterMain.getUpdateInstallationPath());
+              }
+              bundlePaths.add(appBundlePath);
+              args.bundlePaths = bundlePaths.toArray(new String[0]);
               args.entrypoint = "main";
               flutterView.runFromBundle(args);
             }

shell/platform/android/io/flutter/view/FlutterMain.java

@@ -77,6 +77,7 @@ private static String fromFlutterAssets(String filePath) {
     private static String sFlutterAssetsDir = DEFAULT_FLUTTER_ASSETS_DIR;
 
     private static boolean sInitialized = false;
+    private static ResourceUpdater sResourceUpdater;
     private static ResourceExtractor sResourceExtractor;
     private static boolean sIsPrecompiledAsBlobs;
     private static boolean sIsPrecompiledAsSharedLibrary;
@@ -254,6 +255,21 @@ private static void initResources(Context applicationContext) {
         Context context = applicationContext;
         new ResourceCleaner(context).start();
 
+        Bundle metaData = null;
+        try {
+            metaData = context.getPackageManager().getApplicationInfo(
+                    context.getPackageName(), PackageManager.GET_META_DATA).metaData;
+
+        } catch (PackageManager.NameNotFoundException e) {
+            Log.e(TAG, "Unable to read application info", e);
+        }
+
+        if (metaData != null && metaData.getBoolean("DynamicUpdates")) {
+            sResourceUpdater = new ResourceUpdater(context);
+            sResourceUpdater.startUpdateDownloadOnce();
+            sResourceUpdater.waitForDownloadCompletion();
+        }
+
         sResourceExtractor = new ResourceExtractor(context);
 
         String icuAssetPath = SHARED_ASSET_DIR + File.separator + SHARED_ASSET_ICU_DATA;
@@ -321,6 +337,10 @@ public static String findAppBundlePath(Context applicationContext) {
         return appBundle.exists() ? appBundle.getPath() : null;
     }
 
+    public static String getUpdateInstallationPath() {
+        return sResourceUpdater == null ? null : sResourceUpdater.getUpdateInstallationPath();
+    }
+
     /**
      * Returns the file name for the given asset.
      * The returned file name can be used to access the asset in the APK

shell/platform/android/io/flutter/view/ResourceExtractor.java

@@ -11,15 +11,22 @@
 import android.os.AsyncTask;
 import android.util.Log;
 import io.flutter.util.PathUtils;
+import org.json.JSONException;
+import org.json.JSONObject;
 
 import java.io.*;
 import java.util.Collection;
 import java.util.HashSet;
+import java.util.Scanner;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.ExecutionException;
+import java.util.zip.CRC32;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipException;
+import java.util.zip.ZipFile;
 
 /**
- * A class to intialize the native code.
+ * A class to initialize the native code.
  **/
 class ResourceExtractor {
     private static final String TAG = "ResourceExtractor";
@@ -33,18 +40,46 @@ private class ExtractTask extends AsyncTask<Void, Void, Void> {
         private void extractResources() {
             final File dataDir = new File(PathUtils.getDataDirectory(mContext));
 
-            final String timestamp = checkTimestamp(dataDir);
+            JSONObject updateManifest = readUpdateManifest();
+            if (!validateUpdateManifest(updateManifest)) {
+                updateManifest = null;
+            }
+
+            final String timestamp = checkTimestamp(dataDir, updateManifest);
+            if (timestamp == null) {
+                return;
+            }
+
+            deleteFiles();
+
+            if (updateManifest != null) {
+                if (!extractUpdate(dataDir)) {
+                    return;
+                }
+            }
+
+            if (!extractAPK(dataDir)) {
+                return;
+            }
+
             if (timestamp != null) {
-                deleteFiles();
+                try {
+                    new File(dataDir, timestamp).createNewFile();
+                } catch (IOException e) {
+                    Log.w(TAG, "Failed to write resource timestamp");
+                }
             }
+        }
 
+        /// Returns true if successfully unpacked APK resources,
+        /// otherwise deletes all resources and returns false.
+        private boolean extractAPK(File dataDir) {
             final AssetManager manager = mContext.getResources().getAssets();
 
             byte[] buffer = null;
             for (String asset : mResources) {
                 try {
                     final File output = new File(dataDir, asset);
-
                     if (output.exists()) {
                         continue;
                     }
@@ -62,28 +97,99 @@ private void extractResources() {
                             while ((count = is.read(buffer, 0, BUFFER_SIZE)) != -1) {
                                 os.write(buffer, 0, count);
                             }
+
                             os.flush();
+                            Log.i(TAG, "Extracted baseline resource " + asset);
                         }
                     }
+
                 } catch (FileNotFoundException fnfe) {
                     continue;
+
                 } catch (IOException ioe) {
                     Log.w(TAG, "Exception unpacking resources: " + ioe.getMessage());
                     deleteFiles();
-                    return;
+                    return false;
                 }
             }
 
-            if (timestamp != null) {
-                try {
-                    new File(dataDir, timestamp).createNewFile();
-                } catch (IOException e) {
-                    Log.w(TAG, "Failed to write resource timestamp");
+            return true;
+        }
+
+        /// Returns true if successfully unpacked update resources or if there is no update,
+        /// otherwise deletes all resources and returns false.
+        private boolean extractUpdate(File dataDir) {
+            if (FlutterMain.getUpdateInstallationPath() == null) {
+                return true;
+            }
+
+            final File updateFile = new File(FlutterMain.getUpdateInstallationPath());
+            if (!updateFile.exists()) {
+                return true;
+            }
+
+            ZipFile zipFile;
+            try {
+                zipFile = new ZipFile(updateFile);
+
+            } catch (ZipException e) {
+                Log.w(TAG, "Exception unpacking resources: " + e.getMessage());
+                deleteFiles();
+                return false;
+
+            } catch (IOException e) {
+                Log.w(TAG, "Exception unpacking resources: " + e.getMessage());
+                deleteFiles();
+                return false;
+            }
+
+            byte[] buffer = null;
+            for (String asset : mResources) {
+                ZipEntry entry = zipFile.getEntry(asset);
+                if (entry == null) {
+                    continue;
+                }
+
+                final File output = new File(dataDir, asset);
+                if (output.exists()) {
+                    continue;
+                }
+                if (output.getParentFile() != null) {
+                    output.getParentFile().mkdirs();
+                }
+
+                try (InputStream is = zipFile.getInputStream(entry)) {
+                    try (OutputStream os = new FileOutputStream(output)) {
+                        if (buffer == null) {
+                            buffer = new byte[BUFFER_SIZE];
+                        }
+
+                        int count = 0;
+                        while ((count = is.read(buffer, 0, BUFFER_SIZE)) != -1) {
+                            os.write(buffer, 0, count);
+                        }
+
+                        os.flush();
+                        Log.i(TAG, "Extracted override resource " + asset);
+                    }
+
+                } catch (FileNotFoundException fnfe) {
+                    continue;
+
+                } catch (IOException ioe) {
+                    Log.w(TAG, "Exception unpacking resources: " + ioe.getMessage());
+                    deleteFiles();
+                    return false;
                 }
             }
+
+            return true;
         }
 
-        private String checkTimestamp(File dataDir) {
+        // Returns null if extracted resources are found and match the current APK version
+        // and update version if any, otherwise returns the current APK and update version.
+        private String checkTimestamp(File dataDir, JSONObject updateManifest) {
+
             PackageManager packageManager = mContext.getPackageManager();
             PackageInfo packageInfo = null;
 
@@ -100,20 +206,119 @@ private String checkTimestamp(File dataDir) {
             String expectedTimestamp =
                     TIMESTAMP_PREFIX + packageInfo.versionCode + "-" + packageInfo.lastUpdateTime;
 
+            if (updateManifest != null) {
+                String baselineVersion = updateManifest.optString("baselineVersion", null);
+                if (baselineVersion == null) {
+                    Log.w(TAG, "Invalid update manifest: baselineVersion");
+                }
+
+                String updateVersion = updateManifest.optString("updateVersion", null);
+                if (updateVersion == null) {
+                    Log.w(TAG, "Invalid update manifest: updateVersion");
+                }
+
+                if (baselineVersion != null && updateVersion != null) {
+                    if (!baselineVersion.equals(Integer.toString(packageInfo.versionCode))) {
+                        Log.w(TAG, "Outdated update file for " + packageInfo.versionCode);
+                    } else {
+                        final File updateFile = new File(FlutterMain.getUpdateInstallationPath());
+                        expectedTimestamp += "-" + updateVersion + "-" + updateFile.lastModified();
+                    }
+                }
+            }
+
             final String[] existingTimestamps = getExistingTimestamps(dataDir);
 
             if (existingTimestamps == null) {
-                return null;
+                Log.i(TAG, "No extracted resources found");
+                return expectedTimestamp;
+            }
+
+            if (existingTimestamps.length == 1) {
+                Log.i(TAG, "Found extracted resources " + existingTimestamps[0]);
             }
 
             if (existingTimestamps.length != 1
                     || !expectedTimestamp.equals(existingTimestamps[0])) {
+                Log.i(TAG, "Resource version mismatch " + expectedTimestamp);
                 return expectedTimestamp;
             }
 
             return null;
         }
 
+        /// Returns true if the downloaded update file was indeed built for this APK.
+        private boolean validateUpdateManifest(JSONObject updateManifest) {
+            if (updateManifest == null) {
+                return false;
+            }
+
+            String baselineChecksum = updateManifest.optString("baselineChecksum", null);
+            if (baselineChecksum == null) {
+                Log.w(TAG, "Invalid update manifest: baselineChecksum");
+                return false;
+            }
+
+            final AssetManager manager = mContext.getResources().getAssets();
+            try (InputStream is = manager.open("flutter_assets/isolate_snapshot_data")) {
+                CRC32 checksum = new CRC32();
+
+                int count = 0;
+                byte[] buffer = new byte[BUFFER_SIZE];
+                while ((count = is.read(buffer, 0, BUFFER_SIZE)) != -1) {
+                    checksum.update(buffer, 0, count);
+                }
+
+                if (!baselineChecksum.equals(String.valueOf(checksum.getValue()))) {
+                    Log.w(TAG, "Mismatched update file for APK");
+                    return false;
+                }
+
+                return true;
+
+            } catch (IOException e) {
+                Log.w(TAG, "Could not read APK: " + e);
+                return false;
+            }
+        }
+
+        /// Returns null if no update manifest is found.
+        private JSONObject readUpdateManifest() {
+            if (FlutterMain.getUpdateInstallationPath() == null) {
+                return null;
+            }
+
+            File updateFile = new File(FlutterMain.getUpdateInstallationPath());
+            if (!updateFile.exists()) {
+                return null;
+            }
+
+            try {
+                ZipFile zipFile = new ZipFile(updateFile);
+                ZipEntry entry = zipFile.getEntry("manifest.json");
+                if (entry == null) {
+                    Log.w(TAG, "Invalid update file: " + updateFile);
+                    return null;
+                }
+
+                // Read and parse the entire JSON file as single operation.
+                Scanner scanner = new Scanner(zipFile.getInputStream(entry));
+                return new JSONObject(scanner.useDelimiter("\\A").next());
+
+            } catch (ZipException e) {
+                Log.w(TAG, "Invalid update file: " + e);
+                return null;
+
+            } catch (IOException e) {
+                Log.w(TAG, "Invalid update file: " + e);
+                return null;
+
+            } catch (JSONException e) {
+                Log.w(TAG, "Invalid update file: " + e);
+                return null;
+            }
+        }
+
         @Override
         protected Void doInBackground(Void... unused) {
             extractResources();