From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Grace Jia <xiaotonj@google.com>
Date: Thu, 22 Sep 2022 14:20:57 -0700
Subject: [PATCH] Fix security vulnerability when register phone accounts.

Currently if the registered self-managed phone account updated to a call
provider phone account, the enable state will be directly copied to the
updated one so that malicious app can perform call spoofing attack
without any permission requirements. Fix this by disallowing change a
self-managed phone account to a managed phone account.

Bug: 246930197
Test: CtsTelecomTestCases:SelfManagedConnectionSreviceTest
Change-Id: I8f7984cd491632b3219133044438b82ca4dec80e
Merged-In: I8f7984cd491632b3219133044438b82ca4dec80e
(cherry picked from commit 833dd8480adc773e36d388521a14fd8cd11d6a30)
Merged-In: I8f7984cd491632b3219133044438b82ca4dec80e
---
 .../server/telecom/PhoneAccountRegistrar.java     | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/com/android/server/telecom/PhoneAccountRegistrar.java b/src/com/android/server/telecom/PhoneAccountRegistrar.java
index 5323a9669..4bcd2e5c3 100644
--- a/src/com/android/server/telecom/PhoneAccountRegistrar.java
+++ b/src/com/android/server/telecom/PhoneAccountRegistrar.java
@@ -48,6 +48,7 @@ import android.telephony.TelephonyManager;
 import android.text.TextUtils;
 import android.util.AtomicFile;
 import android.util.Base64;
+import android.util.EventLog;
 import android.util.Xml;
 
 // TODO: Needed for move to system service: import com.android.internal.R;
@@ -680,6 +681,7 @@ public class PhoneAccountRegistrar {
 
         PhoneAccount oldAccount = getPhoneAccountUnchecked(account.getAccountHandle());
         if (oldAccount != null) {
+            enforceSelfManagedAccountUnmodified(account, oldAccount);
             mState.accounts.remove(oldAccount);
             isEnabled = oldAccount.isEnabled();
             Log.i(this, "Modify account: %s", getAccountDiffString(account, oldAccount));
@@ -738,6 +740,19 @@ public class PhoneAccountRegistrar {
         }
     }
 
+    private void enforceSelfManagedAccountUnmodified(PhoneAccount newAccount,
+            PhoneAccount oldAccount) {
+        if (oldAccount.hasCapabilities(PhoneAccount.CAPABILITY_SELF_MANAGED) &&
+                (!newAccount.hasCapabilities(PhoneAccount.CAPABILITY_SELF_MANAGED))) {
+            EventLog.writeEvent(0x534e4554, "246930197");
+            Log.w(this, "Self-managed phone account %s replaced by a non self-managed one",
+                    newAccount.getAccountHandle());
+            throw new IllegalArgumentException("Error, cannot change a self-managed "
+                    + "phone account " + newAccount.getAccountHandle()
+                    + " to other kinds of phone account");
+        }
+    }
+
     /**
      * Un-registers all phone accounts associated with a specified package.
      *
