Fix security hole in Google backup transport registration
Previously, it was conceivable that a 3rd party application on a non-GED
device could publish a service that supported the (hidden) IBackupTransport
interface and spoofed the Google backup transport's package and component
name. This could allow it to secretly intercept all data moved through the
backup mechanism.
Fix by ensuring that the package in question exists and is part of the
OS itself (FLAG_SYSTEM in its ApplicationInfo description) before binding
to it.
Fixes bug #2457063
Change-Id: I3487572be45c2014fa209beacfe3ac6f8270f872
diff --git a/services/java/com/android/server/BackupManagerService.java b/services/java/com/android/server/BackupManagerService.java
index 91dfaf3..d67dde0 100644
--- a/services/java/com/android/server/BackupManagerService.java
+++ b/services/java/com/android/server/BackupManagerService.java
@@ -479,10 +479,25 @@
// Attach to the Google backup transport. When this comes up, it will set
// itself as the current transport because we explicitly reset mCurrentTransport
// to null.
- Intent intent = new Intent().setComponent(new ComponentName(
- "com.google.android.backup",
- "com.google.android.backup.BackupTransportService"));
- context.bindService(intent, mGoogleConnection, Context.BIND_AUTO_CREATE);
+ ComponentName transportComponent = new ComponentName("com.google.android.backup",
+ "com.google.android.backup.BackupTransportService");
+ try {
+ // If there's something out there that is supposed to be the Google
+ // backup transport, make sure it's legitimately part of the OS build
+ // and not an app lying about its package name.
+ ApplicationInfo info = mPackageManager.getApplicationInfo(
+ transportComponent.getPackageName(), 0);
+ if ((info.flags & ApplicationInfo.FLAG_SYSTEM) != 0) {
+ if (DEBUG) Slog.v(TAG, "Binding to Google transport");
+ Intent intent = new Intent().setComponent(transportComponent);
+ context.bindService(intent, mGoogleConnection, Context.BIND_AUTO_CREATE);
+ } else {
+ Slog.w(TAG, "Possible Google transport spoof: ignoring " + info);
+ }
+ } catch (PackageManager.NameNotFoundException nnf) {
+ // No such package? No binding.
+ if (DEBUG) Slog.v(TAG, "Google transport not present");
+ }
// Now that we know about valid backup participants, parse any
// leftover journal files into the pending backup set
