Don't trust callers to supply app info to bindBackupAgent()

Get the canonical identity and metadata about the package from the
Package Manager at time of usage rather than rely on the caller to
have gotten things right, even when the caller has the system uid.

Bug 28795098

Change-Id: I215786bc894dedf7ca28e9c80cefabd0e40ca877

Merge conflict resolution for ag/1133474 (referencing ag/1148862)
- directly to mnc-mr2-release
(cherry picked from commit b2a6b594827da2f595bf48c04088fb98e71333aa)

Change-Id: Ie82264ad0512d0ab59de8a964e96866088cb1a33
diff --git a/core/java/android/app/ActivityManagerNative.java b/core/java/android/app/ActivityManagerNative.java
index f6e0735..b9d2595 100644
--- a/core/java/android/app/ActivityManagerNative.java
+++ b/core/java/android/app/ActivityManagerNative.java
@@ -1582,9 +1582,10 @@
 
         case START_BACKUP_AGENT_TRANSACTION: {
             data.enforceInterface(IActivityManager.descriptor);
-            ApplicationInfo info = ApplicationInfo.CREATOR.createFromParcel(data);
+            String packageName = data.readString();
             int backupRestoreMode = data.readInt();
-            boolean success = bindBackupAgent(info, backupRestoreMode);
+            int userId = data.readInt();
+            boolean success = bindBackupAgent(packageName, backupRestoreMode, userId);
             reply.writeNoException();
             reply.writeInt(success ? 1 : 0);
             return true;
@@ -3831,13 +3832,14 @@
         return binder;
     }
 
-    public boolean bindBackupAgent(ApplicationInfo app, int backupRestoreMode)
+    public boolean bindBackupAgent(String packageName, int backupRestoreMode, int userId)
             throws RemoteException {
         Parcel data = Parcel.obtain();
         Parcel reply = Parcel.obtain();
         data.writeInterfaceToken(IActivityManager.descriptor);
-        app.writeToParcel(data, 0);
+        data.writeString(packageName);
         data.writeInt(backupRestoreMode);
+        data.writeInt(userId);
         mRemote.transact(START_BACKUP_AGENT_TRANSACTION, data, reply, 0);
         reply.readException();
         boolean success = reply.readInt() != 0;
diff --git a/core/java/android/app/IActivityManager.java b/core/java/android/app/IActivityManager.java
index ef121ce..5ed839e 100644
--- a/core/java/android/app/IActivityManager.java
+++ b/core/java/android/app/IActivityManager.java
@@ -182,7 +182,7 @@
     public IBinder peekService(Intent service, String resolvedType, String callingPackage)
             throws RemoteException;
 
-    public boolean bindBackupAgent(ApplicationInfo appInfo, int backupRestoreMode)
+    public boolean bindBackupAgent(String packageName, int backupRestoreMode, int userId)
             throws RemoteException;
     public void clearPendingBackup() throws RemoteException;
     public void backupAgentCreated(String packageName, IBinder agent) throws RemoteException;
diff --git a/services/backup/java/com/android/server/backup/BackupManagerService.java b/services/backup/java/com/android/server/backup/BackupManagerService.java
index 30d90af..ac7c5ab 100644
--- a/services/backup/java/com/android/server/backup/BackupManagerService.java
+++ b/services/backup/java/com/android/server/backup/BackupManagerService.java
@@ -2235,7 +2235,8 @@
             mConnecting = true;
             mConnectedAgent = null;
             try {
-                if (mActivityManager.bindBackupAgent(app, mode)) {
+                if (mActivityManager.bindBackupAgent(app.packageName, mode,
+                        UserHandle.USER_OWNER)) {
                     Slog.d(TAG, "awaiting agent for " + app);
 
                     // success; wait for the agent to arrive
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 33d0a9f..daa4c13 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -16038,11 +16038,22 @@
     // Cause the target app to be launched if necessary and its backup agent
     // instantiated.  The backup agent will invoke backupAgentCreated() on the
     // activity manager to announce its creation.
-    public boolean bindBackupAgent(ApplicationInfo app, int backupMode) {
-        if (DEBUG_BACKUP) Slog.v(TAG_BACKUP,
-                "bindBackupAgent: app=" + app + " mode=" + backupMode);
+    public boolean bindBackupAgent(String packageName, int backupMode, int userId) {
+        if (DEBUG_BACKUP) Slog.v(TAG, "bindBackupAgent: app=" + packageName + " mode=" + backupMode);
         enforceCallingPermission("android.permission.CONFIRM_FULL_BACKUP", "bindBackupAgent");
 
+        IPackageManager pm = AppGlobals.getPackageManager();
+        ApplicationInfo app = null;
+        try {
+            app = pm.getApplicationInfo(packageName, 0, userId);
+        } catch (RemoteException e) {
+            // can't happen; package manager is process-local
+        }
+        if (app == null) {
+            Slog.w(TAG, "Unable to bind backup agent for " + packageName);
+            return false;
+        }
+
         synchronized(this) {
             // !!! TODO: currently no check here that we're already bound
             BatteryStatsImpl.Uid.Pkg.Serv ss = null;