Home | History | Annotate | Download | only in telephony 
      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.internal.telephony;
     18 
     19 import android.app.AppOpsManager;
     20 import android.app.PendingIntent;
     21 import android.content.Context;
     22 import android.content.Intent;
     23 import android.os.Binder;
     24 import android.provider.Telephony.Sms.Intents;
     25 import android.telephony.SmsMessage;
     26 import android.util.ArrayMap;
     27 import android.util.Base64;
     28 import android.util.Log;
     29 
     30 import com.android.internal.annotations.GuardedBy;
     31 
     32 import java.security.SecureRandom;
     33 import java.util.Map;
     34 
     35 
     36 /**
     37  *  Manager for app specific incoming SMS requests. This can be used to implement SMS based
     38  *  communication channels (e.g. for SMS based phone number verification) without needing the
     39  *  {@link Manifest.permission#RECEIVE_SMS} permission.
     40  *
     41  *  {@link #createAppSpecificSmsRequest} allows an application to provide a {@link PendingIntent}
     42  *  that is triggered when an incoming SMS is received that contains the provided token.
     43  */
     44 public class AppSmsManager {
     45     private static final String LOG_TAG = "AppSmsManager";
     46 
     47     private final SecureRandom mRandom;
     48     private final Context mContext;
     49     private final Object mLock = new Object();
     50 
     51     @GuardedBy("mLock")
     52     private final Map<String, AppRequestInfo> mTokenMap;
     53     @GuardedBy("mLock")
     54     private final Map<String, AppRequestInfo> mPackageMap;
     55 
     56     public AppSmsManager(Context context) {
     57         mRandom = new SecureRandom();
     58         mTokenMap = new ArrayMap<>();
     59         mPackageMap = new ArrayMap<>();
     60         mContext = context;
     61     }
     62 
     63     /**
     64      * Create an app specific incoming SMS request for the the calling package.
     65      *
     66      * This method returns a token that if included in a subsequent incoming SMS message the
     67      * {@link Intents.SMS_RECEIVED_ACTION} intent will be delivered only to the calling package and
     68      * will not require the application have the {@link Manifest.permission#RECEIVE_SMS} permission.
     69      *
     70      * An app can only have one request at a time, if the app already has a request it will be
     71      * dropped and the new one will be added.
     72      *
     73      * @return Token to include in an SMS to have it delivered directly to the app.
     74      */
     75     public String createAppSpecificSmsToken(String callingPkg, PendingIntent intent) {
     76         // Check calling uid matches callingpkg.
     77         AppOpsManager appOps = (AppOpsManager) mContext.getSystemService(Context.APP_OPS_SERVICE);
     78         appOps.checkPackage(Binder.getCallingUid(), callingPkg);
     79 
     80         // Generate a nonce to store the request under.
     81         String token = generateNonce();
     82         synchronized (mLock) {
     83             // Only allow one request in flight from a package.
     84             if (mPackageMap.containsKey(callingPkg)) {
     85                 removeRequestLocked(mPackageMap.get(callingPkg));
     86             }
     87             // Store state.
     88             AppRequestInfo info = new AppRequestInfo(callingPkg, intent, token);
     89             addRequestLocked(info);
     90         }
     91         return token;
     92     }
     93 
     94     /**
     95      * Handle an incoming SMS_DELIVER_ACTION intent if it is an app-only SMS.
     96      */
     97     public boolean handleSmsReceivedIntent(Intent intent) {
     98         // Sanity check the action.
     99         if (intent.getAction() != Intents.SMS_DELIVER_ACTION) {
    100             Log.wtf(LOG_TAG, "Got intent with incorrect action: " + intent.getAction());
    101             return false;
    102         }
    103 
    104         synchronized (mLock) {
    105             AppRequestInfo info = findAppRequestInfoSmsIntentLocked(intent);
    106             if (info == null) {
    107                 // The message didn't contain a token -- nothing to do.
    108                 return false;
    109             }
    110             try {
    111                 Intent fillIn = new Intent();
    112                 fillIn.putExtras(intent.getExtras());
    113                 info.pendingIntent.send(mContext, 0, fillIn);
    114             } catch (PendingIntent.CanceledException e) {
    115                 // The pending intent is canceled, send this SMS as normal.
    116                 removeRequestLocked(info);
    117                 return false;
    118             }
    119 
    120             removeRequestLocked(info);
    121             return true;
    122         }
    123     }
    124 
    125     private AppRequestInfo findAppRequestInfoSmsIntentLocked(Intent intent) {
    126         SmsMessage[] messages = Intents.getMessagesFromIntent(intent);
    127         if (messages == null) {
    128             return null;
    129         }
    130         StringBuilder fullMessageBuilder = new StringBuilder();
    131         for (SmsMessage message : messages) {
    132             if (message == null || message.getMessageBody() == null) {
    133                 continue;
    134             }
    135             fullMessageBuilder.append(message.getMessageBody());
    136         }
    137 
    138         String fullMessage = fullMessageBuilder.toString();
    139 
    140         // Look for any tokens in the full message.
    141         for (String token : mTokenMap.keySet()) {
    142             if (fullMessage.contains(token)) {
    143                 return mTokenMap.get(token);
    144             }
    145         }
    146         return null;
    147     }
    148 
    149     private String generateNonce() {
    150         byte[] bytes = new byte[8];
    151         mRandom.nextBytes(bytes);
    152         return Base64.encodeToString(bytes, Base64.URL_SAFE | Base64.NO_WRAP | Base64.NO_PADDING);
    153     }
    154 
    155     private void removeRequestLocked(AppRequestInfo info) {
    156         mTokenMap.remove(info.token);
    157         mPackageMap.remove(info.packageName);
    158     }
    159 
    160     private void addRequestLocked(AppRequestInfo info) {
    161         mTokenMap.put(info.token, info);
    162         mPackageMap.put(info.packageName, info);
    163     }
    164 
    165     private final class AppRequestInfo {
    166         public final String packageName;
    167         public final PendingIntent pendingIntent;
    168         public final String token;
    169 
    170         AppRequestInfo(String packageName, PendingIntent pendingIntent, String token) {
    171             this.packageName = packageName;
    172             this.pendingIntent = pendingIntent;
    173             this.token = token;
    174         }
    175     }
    176 
    177 }
    178