From 44cda6f5e47c33e91980ae35c8bc6d88e4d3763c Mon Sep 17 00:00:00 2001
From: Tad <tad@spotco.us>
Date: Thu, 24 Nov 2016 13:01:30 -0500
Subject: [PATCH] Allow packages to spoof their signature

Change-Id: I9acf48c7607804890d0d0fa7fe30bb36779cb40d
---
 core/res/AndroidManifest.xml                       |  7 +++++++
 core/res/res/values/config.xml                     |  2 ++
 core/res/res/values/strings.xml                    |  5 +++++
 .../android/server/pm/PackageManagerService.java   | 23 ++++++++++++++++++++--
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index b624305..43eec1f 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -1926,6 +1926,13 @@
         android:description="@string/permdesc_getPackageSize"
         android:protectionLevel="normal" />
 
+    <!-- @hide Allows an application to change the package signature as
+         seen by applications -->
+    <permission android:name="android.permission.FAKE_PACKAGE_SIGNATURE"
+        android:protectionLevel="dangerous"
+        android:label="@string/permlab_fakePackageSignature"
+        android:description="@string/permdesc_fakePackageSignature" />
+
     <!-- @deprecated No longer useful, see
          {@link android.content.pm.PackageManager#addPackageToPreferred}
          for details. -->
diff --git a/core/res/res/values/config.xml b/core/res/res/values/config.xml
index 4a95f6e..702e02a 100644
--- a/core/res/res/values/config.xml
+++ b/core/res/res/values/config.xml
@@ -1383,6 +1383,8 @@
     <string-array name="config_locationProviderPackageNames" translatable="false">
         <!-- The standard AOSP fused location provider -->
         <item>com.android.location.fused</item>
+        <!-- The (faked) microg fused location provider -->
+        <item>com.google.android.gms</item>
     </string-array>
 
     <!-- This string array can be overriden to enable test location providers initially. -->
diff --git a/core/res/res/values/strings.xml b/core/res/res/values/strings.xml
index 345d377..26814f1 100644
--- a/core/res/res/values/strings.xml
+++ b/core/res/res/values/strings.xml
@@ -660,6 +660,11 @@
 
     <!--  Permissions -->
 
+   <!-- Title of an application permission, listed so the user can choose whether they want to allow the application to do this. -->
+    <string name="permlab_fakePackageSignature">Spoof package signature</string>
+    <!-- Description of an application permission, listed so the user can choose whether they want to allow the application to do this. -->
+    <string name="permdesc_fakePackageSignature">Allows the app to pretend to be a different app. Malicious applications might be able to use this to access private application data. Grant this permission with caution only!</string>
+
     <!-- Title of an application permission, listed so the user can choose whether they want to allow the application to do this. -->
     <string name="permlab_statusBar">disable or modify status bar</string>
     <!-- Description of an application permission, listed so the user can choose whether they want to allow the application to do this. -->
diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index d450288..9194e69 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -3141,8 +3141,27 @@ public class PackageManagerService extends IPackageManager.Stub {
                 ? Collections.<String>emptySet() : permissionsState.getPermissions(userId);
         final PackageUserState state = ps.readUserState(userId);
 
-        return PackageParser.generatePackageInfo(p, gids, flags,
-                ps.firstInstallTime, ps.lastUpdateTime, permissions, state, userId);
+        return mayFakeSignature(p, PackageParser.generatePackageInfo(p, gids, flags,
+                ps.firstInstallTime, ps.lastUpdateTime, permissions, state, userId),
+                permissions);
+    }
+
+    private PackageInfo mayFakeSignature(PackageParser.Package p, PackageInfo pi,
+            Set<String> permissions) {
+        try {
+            if (permissions.contains("android.permission.FAKE_PACKAGE_SIGNATURE")
+                    && p.applicationInfo.targetSdkVersion > Build.VERSION_CODES.LOLLIPOP_MR1
+                    && p.mAppMetaData != null) {
+                String sig = p.mAppMetaData.getString("fake-signature");
+                if (sig != null) {
+                    pi.signatures = new Signature[] {new Signature(sig)};
+                }
+            }
+        } catch (Throwable t) {
+            // We should never die because of any failures, this is system code!
+            Log.w("PackageManagerService.FAKE_PACKAGE_SIGNATURE", t);
+        }
+        return pi;
     }
 
     @Override
-- 
2.9.3