DO NOT MERGE: Check provider access for content changes.

For an app to either send or receive content change notifications,
require that they have some level of access to the underlying
provider.

Without these checks, a malicious app could sniff sensitive user data
from the notifications of otherwise private providers.

Test: builds, boots, PoC app now fails
Bug: 32555637
Change-Id: If2dcd45cb0a9f1fb3b93e39fc7b8ae9c34c2fdef
(cherry picked from commit c813f5dae231bd8f01864227c5dba10d43a89249)
(cherry picked from commit db57376d6ccbd4d3e39fc35aa8cfb561bbca4bac)
mh0rst: Backport from android-7.1.1_r21

1 files changed, 43 insertions, 0 deletions

diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 23f34e6..317dea4 100755
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -9623,6 +9623,44 @@ public final class ActivityManagerService extends ActivityManagerNative
     }
 
     /**
+     * Check if the calling UID has a possible chance at accessing the provider
+     * at the given authority and user.
+     */
+    public String checkContentProviderAccess(String authority, int userId) {
+        if (userId == UserHandle.USER_ALL) {
+            mContext.enforceCallingOrSelfPermission(
+                    Manifest.permission.INTERACT_ACROSS_USERS_FULL, TAG);
+            userId = UserHandle.getCallingUserId();
+        }
+
+        ProviderInfo cpi = null;
+        try {
+            cpi = AppGlobals.getPackageManager().resolveContentProvider(authority,
+                    STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS,
+                    userId);
+        } catch (RemoteException ignored) {
+        }
+        if (cpi == null) {
+            // TODO: make this an outright failure in a future platform release;
+            // until then anonymous content notifications are unprotected
+            //return "Failed to find provider " + authority + " for user " + userId;
+            return null;
+        }
+
+        ProcessRecord r = null;
+        synchronized (mPidsSelfLocked) {
+            r = mPidsSelfLocked.get(Binder.getCallingPid());
+        }
+        if (r == null) {
+            return "Failed to find PID " + Binder.getCallingPid();
+        }
+
+        synchronized (this) {
+            return checkContentProviderPermissionLocked(cpi, r, userId, true);
+        }
+    }
+
+    /**
      * Check if {@link ProcessRecord} has a possible chance at accessing the
      * given {@link ProviderInfo}. Final permission checking is always done
      * in {@link ContentProvider}.
@@ -21136,6 +21174,11 @@ public final class ActivityManagerService extends ActivityManagerNative
 
     private final class LocalService extends ActivityManagerInternal {
         @Override
+        public String checkContentProviderAccess(String authority, int userId) {
+            return ActivityManagerService.this.checkContentProviderAccess(authority, userId);
+        }
+
+        @Override
         public void onWakefulnessChanged(int wakefulness) {
             ActivityManagerService.this.onWakefulnessChanged(wakefulness);
         }