From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Pranav Madapurmath <pmadapurmath@google.com>
Date: Wed, 5 Apr 2023 21:36:12 +0000
Subject: [PATCH] Resolve account image icon profile boundary exploit.

Because Telecom grants the INTERACT_ACROSS_USERS permission, an exploit
is possible where the user can upload an image icon (belonging to
another user) via registering a phone account. This CL provides a
lightweight solution for parsing the image URI to detect profile
exploitation.

Fixes: 273502295
Fixes: 296915211
Test: Unit test to enforce successful/failure path
(cherry picked from commit d0d1d38e37de54e58a7532a0020582fbd7d476b7)
(cherry picked from commit e7d0ca3fe5be6e393f643f565792ea5e7ed05f48)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:a604311f86ea8136ca2ac9f9ff0af7fa57ee3f42)
Merged-In: I2b6418f019a373ee9f02ba8683e5b694e7ab80a5
Change-Id: I2b6418f019a373ee9f02ba8683e5b694e7ab80a5
---
 .../server/telecom/TelecomServiceImpl.java    | 22 +++++++++++++++++++
 .../telecom/tests/TelecomServiceImplTest.java | 21 ++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/src/com/android/server/telecom/TelecomServiceImpl.java b/src/com/android/server/telecom/TelecomServiceImpl.java
index 74a7d840b..14804f0d3 100644
--- a/src/com/android/server/telecom/TelecomServiceImpl.java
+++ b/src/com/android/server/telecom/TelecomServiceImpl.java
@@ -36,6 +36,7 @@ import android.content.pm.PackageManager;
 import android.content.res.Resources;
 import android.content.pm.ParceledListSlice;
 import android.content.pm.ResolveInfo;
+import android.graphics.drawable.Icon;
 import android.net.Uri;
 import android.os.Binder;
 import android.os.Bundle;
@@ -469,6 +470,9 @@ public class TelecomServiceImpl {
                             enforceRegisterMultiUser();
                         }
                         enforceUserHandleMatchesCaller(account.getAccountHandle());
+                        // Validate the profile boundary of the given image URI.
+                        validateAccountIconUserBoundary(account.getIcon());
+
                         final long token = Binder.clearCallingIdentity();
                         try {
                             mPhoneAccountRegistrar.registerPhoneAccount(account);
@@ -1820,4 +1824,22 @@ public class TelecomServiceImpl {
         // If only TX or RX were set (or neither), the video state is valid.
         return remainingState == 0;
     }
+
+    private void validateAccountIconUserBoundary(Icon icon) {
+        // Refer to Icon#getUriString for context. The URI string is invalid for icons of
+        // incompatible types.
+        if (icon != null && (icon.getType() == Icon.TYPE_URI
+                /*|| icon.getType() == Icon.TYPE_URI_ADAPTIVE_BITMAP*/)) {
+            String encodedUser = icon.getUri().getEncodedUserInfo();
+            // If there is no encoded user, the URI is calling into the calling user space
+            if (encodedUser != null) {
+                int userId = Integer.parseInt(encodedUser);
+                if (userId != UserHandle.getUserId(Binder.getCallingUid())) {
+                    // If we are transcending the profile boundary, throw an error.
+                    throw new IllegalArgumentException("Attempting to register a phone account with"
+                            + " an image icon belonging to another user.");
+                }
+            }
+        }
+    }
 }
diff --git a/tests/src/com/android/server/telecom/tests/TelecomServiceImplTest.java b/tests/src/com/android/server/telecom/tests/TelecomServiceImplTest.java
index 521d05aae..8aa6f806c 100644
--- a/tests/src/com/android/server/telecom/tests/TelecomServiceImplTest.java
+++ b/tests/src/com/android/server/telecom/tests/TelecomServiceImplTest.java
@@ -29,6 +29,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
+import android.graphics.drawable.Icon;
 import android.net.Uri;
 import android.os.Binder;
 import android.os.Bundle;
@@ -501,6 +502,26 @@ public class TelecomServiceImplTest extends TelecomTestCase {
         }
     }
 
+    @SmallTest
+    @Test
+    public void testRegisterPhoneAccountImageIconCrossUser() throws RemoteException {
+        String packageNameToUse = "com.android.officialpackage";
+        PhoneAccountHandle phHandle = new PhoneAccountHandle(new ComponentName(
+                packageNameToUse, "cs"), "test", Binder.getCallingUserHandle());
+        Icon icon = Icon.createWithContentUri("content://10@media/external/images/media/");
+        PhoneAccount phoneAccount = makePhoneAccount(phHandle).setIcon(icon).build();
+        doReturn(PackageManager.PERMISSION_GRANTED)
+                .when(mContext).checkCallingOrSelfPermission(MODIFY_PHONE_STATE);
+
+        // This should fail; security exception will be thrown.
+        registerPhoneAccountTestHelper(phoneAccount, false);
+
+        icon = Icon.createWithContentUri("content://0@media/external/images/media/");
+        phoneAccount = makePhoneAccount(phHandle).setIcon(icon).build();
+        // This should succeed.
+        registerPhoneAccountTestHelper(phoneAccount, true);
+    }
+
     @SmallTest
     @Test
     public void testUnregisterPhoneAccount() throws RemoteException {