From 91add43ae7d31d9f2ccd9a2e7a692289ea4d258f Mon Sep 17 00:00:00 2001 From: Jeff Sharkey Date: Fri, 18 Nov 2016 15:31:22 -0700 Subject: [PATCH] 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 --- .../android/app/ActivityManagerInternal.java | 5 ++ .../server/am/ActivityManagerService.java | 43 +++++++++++ .../server/content/ContentService.java | 72 ++++++++++++------- 3 files changed, 94 insertions(+), 26 deletions(-) diff --git a/core/java/android/app/ActivityManagerInternal.java b/core/java/android/app/ActivityManagerInternal.java index d56dc1e07f52d..44b564cb885c0 100644 --- a/core/java/android/app/ActivityManagerInternal.java +++ b/core/java/android/app/ActivityManagerInternal.java @@ -22,6 +22,11 @@ package android.app; * @hide Only for use within the system server. */ public abstract class ActivityManagerInternal { + /** + * Verify that calling app has access to the given provider. + */ + public abstract String checkContentProviderAccess(String authority, int userId); + // Called by the power manager. public abstract void onWakefulnessChanged(int wakefulness); diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java index 07bdd2347c2e9..dfe1f32103e18 100755 --- a/services/core/java/com/android/server/am/ActivityManagerService.java +++ b/services/core/java/com/android/server/am/ActivityManagerService.java @@ -8991,6 +8991,44 @@ public final class ActivityManagerService extends ActivityManagerNative return providers; } + /** + * 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 @@ -19653,6 +19691,11 @@ 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); diff --git a/services/core/java/com/android/server/content/ContentService.java b/services/core/java/com/android/server/content/ContentService.java index 22141dcb282de..d07d76a77d42e 100644 --- a/services/core/java/com/android/server/content/ContentService.java +++ b/services/core/java/com/android/server/content/ContentService.java @@ -19,11 +19,14 @@ package com.android.server.content; import android.Manifest; import android.accounts.Account; import android.app.ActivityManager; +import android.app.ActivityManagerInternal; +import android.app.ActivityManagerNative; import android.content.ComponentName; import android.content.ContentResolver; import android.content.Context; import android.content.IContentService; import android.content.ISyncStatusObserver; +import android.content.Intent; import android.content.PeriodicSync; import android.content.pm.PackageManager; import android.content.SyncAdapterType; @@ -46,6 +49,8 @@ import android.util.Log; import android.util.Slog; import android.util.SparseIntArray; +import com.android.server.LocalServices; + import java.io.FileDescriptor; import java.io.PrintWriter; import java.security.InvalidParameterException; @@ -172,16 +177,17 @@ public final class ContentService extends IContentService.Stub { throw new IllegalArgumentException("You must pass a valid uri and observer"); } - enforceCrossUserPermission(userHandle, - "no permission to observe other users' provider view"); + final int uid = Binder.getCallingUid(); + final int pid = Binder.getCallingPid(); - if (userHandle < 0) { - if (userHandle == UserHandle.USER_CURRENT) { - userHandle = ActivityManager.getCurrentUser(); - } else if (userHandle != UserHandle.USER_ALL) { - throw new InvalidParameterException("Bad user handle for registerContentObserver: " - + userHandle); - } + userHandle = handleIncomingUser(uri, pid, uid, + Intent.FLAG_GRANT_READ_URI_PERMISSION, userHandle); + + final String msg = LocalServices.getService(ActivityManagerInternal.class) + .checkContentProviderAccess(uri.getAuthority(), userHandle); + if (msg != null) { + Log.w(TAG, "Ignoring content changes for " + uri + " from " + uid + ": " + msg); + return; } synchronized (mRootNode) { @@ -224,24 +230,20 @@ public final class ContentService extends IContentService.Stub { + " from observer " + observer + ", syncToNetwork " + syncToNetwork); } - // Notify for any user other than the caller's own requires permission. - final int callingUserHandle = UserHandle.getCallingUserId(); - if (userHandle != callingUserHandle) { - mContext.enforceCallingOrSelfPermission(Manifest.permission.INTERACT_ACROSS_USERS, - "no permission to notify other users"); - } - - // We passed the permission check; resolve pseudouser targets as appropriate - if (userHandle < 0) { - if (userHandle == UserHandle.USER_CURRENT) { - userHandle = ActivityManager.getCurrentUser(); - } else if (userHandle != UserHandle.USER_ALL) { - throw new InvalidParameterException("Bad user handle for notifyChange: " - + userHandle); - } - } - final int uid = Binder.getCallingUid(); + final int pid = Binder.getCallingPid(); + final int callingUserHandle = UserHandle.getCallingUserId(); + + userHandle = handleIncomingUser(uri, pid, uid, + Intent.FLAG_GRANT_WRITE_URI_PERMISSION, userHandle); + + final String msg = LocalServices.getService(ActivityManagerInternal.class) + .checkContentProviderAccess(uri.getAuthority(), userHandle); + if (msg != null) { + Log.w(TAG, "Ignoring notify for " + uri + " from " + uid + ": " + msg); + return; + } + // This makes it so that future permission checks will be in the context of this // process rather than the caller's process. We will restore this before returning. long identityToken = clearCallingIdentity(); @@ -881,6 +883,24 @@ public final class ContentService extends IContentService.Stub { return service; } + private int handleIncomingUser(Uri uri, int pid, int uid, int modeFlags, int userId) { + if (userId == UserHandle.USER_CURRENT) { + userId = ActivityManager.getCurrentUser(); + } + + if (userId == UserHandle.USER_ALL) { + mContext.enforceCallingOrSelfPermission( + Manifest.permission.INTERACT_ACROSS_USERS_FULL, TAG); + } else if (userId < 0) { + throw new IllegalArgumentException("Invalid user: " + userId); + } else if (userId != UserHandle.getCallingUserId()) { + mContext.enforceCallingOrSelfPermission( + Manifest.permission.INTERACT_ACROSS_USERS_FULL, TAG); + } + + return userId; + } + /** * Checks if the request is from the system or an app that has INTERACT_ACROSS_USERS_FULL * permission, if the userHandle is not for the caller.