From 113f3a4a1d9171db7456aa9ae8b0a2b50545c326 Mon Sep 17 00:00:00 2001
From: chloedai <chloedai@google.com>
Date: Tue, 11 Jan 2022 04:11:19 +0000
Subject: [PATCH] Add tag availability checking mechanism

Set a cookie to the tag objects when they are constructed, the
cookie could be used to check the availability before returning
the tag service

Bug: 199291025
Test: test with some reader apps, test pass
Merged-In: Iabaab1f6d2d22e15966d31dd79099369d828f4c6
Change-Id: Iabaab1f6d2d22e15966d31dd79099369d828f4c6
---
 core/java/android/nfc/INfcTag.aidl |  3 +++
 core/java/android/nfc/Tag.java     | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/core/java/android/nfc/INfcTag.aidl b/core/java/android/nfc/INfcTag.aidl
index 539fd4adb0a06..e1ccc4fb740be 100644
--- a/core/java/android/nfc/INfcTag.aidl
+++ b/core/java/android/nfc/INfcTag.aidl
@@ -45,4 +45,7 @@ interface INfcTag
     boolean canMakeReadOnly(int ndefType);
     int getMaxTransceiveLength(int technology);
     boolean getExtendedLengthApdusSupported();
+
+    void setTagUpToDate(long cookie);
+    boolean isTagUpToDate(long cookie);
 }
diff --git a/core/java/android/nfc/Tag.java b/core/java/android/nfc/Tag.java
index 398ec63a931b1..0ce9c70569b54 100644
--- a/core/java/android/nfc/Tag.java
+++ b/core/java/android/nfc/Tag.java
@@ -34,6 +34,7 @@ import android.os.Bundle;
 import android.os.Parcel;
 import android.os.Parcelable;
 import android.os.RemoteException;
+import android.os.SystemClock;
 
 import java.io.IOException;
 import java.util.Arrays;
@@ -121,6 +122,7 @@ public final class Tag implements Parcelable {
     final INfcTag mTagService; // interface to NFC service, will be null if mock tag
 
     int mConnectedTechnology;
+    long mCookie;
 
     /**
      * Hidden constructor to be used by NFC service and internal classes.
@@ -140,6 +142,13 @@ public final class Tag implements Parcelable {
         mTagService = tagService;
 
         mConnectedTechnology = -1;
+
+        try {
+            mCookie = SystemClock.elapsedRealtime();
+            tagService.setTagUpToDate(mCookie);
+        } catch (RemoteException e) {
+            throw e.rethrowAsRuntimeException();
+        }
     }
 
     /**
@@ -361,6 +370,18 @@ public final class Tag implements Parcelable {
     /** @hide */
     @UnsupportedAppUsage
     public INfcTag getTagService() {
+        try {
+            if (!mTagService.isTagUpToDate(mCookie)) {
+                String id_str = "";
+                for (int i = 0; i < mId.length; i++) {
+                    id_str = id_str + String.format("%02X ", mId[i]);
+                }
+                String msg = "Permission Denial: Tag ( ID: " + id_str + ") is out of date";
+                throw new SecurityException(msg);
+            }
+        } catch (RemoteException e) {
+            throw e.rethrowAsRuntimeException();
+        }
         return mTagService;
     }