4.4.1.3 创建/使用伙伴服务-安卓应用安全指南(Android Application Secure Design/Secure Coding Guidebook)

4.4.1.2 创建/..

4.4.1.4 创建/..

安卓应用安全指南 (Android Application Secure Design/Secure Coding Guidebook)

4.4.1.3 创建/使用伙伴服务

伙伴服务是只能由特定应用使用的服务。系统由伙伴公司的应用和内部应用组成，用于保护在伙伴应用和内部应用之间处理的信息和功能。

以下是 AIDL 绑定类型服务的示例。

要点（创建服务）：

不要定义意图过滤器，并将导出属性显式设置为true。
验证请求应用的证书是否已在自己的白名单中注册。
请勿（无法）通过onBind(onStartCommand, onHandleIntent)识别请求应用是否为伙伴。
小心并安全地处理接收到的意图，即使意图是从伙伴应用发送的。
仅返回公开给伙伴应用的信息。

另外，请参阅“5.2.1.3 如何验证应用证书的哈希值”，来了解如何验证目标应用的哈希值，它在白名单中指定。

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.jssec.android.service.partnerservice.aidl" >
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:allowBackup="false" >
        <!-- Service using AIDL -->
        <!-- *** POINT 1 *** Do not define the intent filter and explicitly set the exported attribute to
        true. -->
        <service
        android:name="org.jssec.android.service.partnerservice.aidl.PartnerAIDLService"
        android:exported="true" />
    </application>
</manifest>

在这个例子中，将创建 2 个 AIDL 文件。一个是回调接口，将数据从服务提供给活动。另一个接口将数据从活动提供给服务，并获取信息。另外，AIDL 文件中描述的包名称，应与 AIDL 文件的目录层次一致，与java文件中描述的包名称相同。

IExclusiveAIDLServiceCallback.aidl

package org.jssec.android.service.exclusiveservice.aidl;

interface IExclusiveAIDLServiceCallback {
    
    /**
    * It's called when the value is changed.
    */
    void valueChanged(String info);
}

IExclusiveAIDLService.aidl

package org.jssec.android.service.exclusiveservice.aidl;

import org.jssec.android.service.exclusiveservice.aidl.IExclusiveAIDLServiceCallback;

interface IExclusiveAIDLService {
    
    /**
    * Register Callback.
    */
    void registerCallback(IExclusiveAIDLServiceCallback cb);
    
    /**
    * Get Information
    */
    String getInfo(String param);
    
    /**
    * Unregister Callback
    */
    void unregisterCallback(IExclusiveAIDLServiceCallback cb);
}

PartnerAIDLService.java

package org.jssec.android.service.partnerservice.aidl;

import org.jssec.android.shared.PkgCertWhitelists;
import org.jssec.android.shared.Utils;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.RemoteCallbackList;
import android.os.RemoteException;
import android.widget.Toast;

public class PartnerAIDLService extends Service {

    private static final int REPORT_MSG = 1;
    private static final int GETINFO_MSG = 2;
    // The value which this service informs to client
    private int mValue = 0;
    // *** POINT 2 *** Verify that the certificate of the requesting application has been registered in the own white list.
    private static PkgCertWhitelists sWhitelists = null;
    
    private static void buildWhitelists(Context context) {
        boolean isdebug = Utils.isDebuggable(context);
        sWhitelists = new PkgCertWhitelists();
        // Register certificate hash value of partner application "org.jssec.android.service.partnerservice.aidluser"
        sWhitelists.add("org.jssec.android.service.partnerservice.aidluser", isdebug ?
        // Certificate hash value of debug.keystore "androiddebugkey"
            "0EFB7236 328348A9 89718BAD DF57F544 D5CCB4AE B9DB34BC 1E29DD26 F77C8255" :
            // Certificate hash value of keystore "partner key"
            "1F039BB5 7861C27A 3916C778 8E78CE00 690B3974 3EB8259F E2627B8D 4C0EC35A");
            // Register other partner applications in the same way
    }
    
    private static boolean checkPartner(Context context, String pkgname) {
        if (sWhitelists == null) buildWhitelists(context);
        return sWhitelists.test(context, pkgname);
    }
    
    // Object to register callback
    // Methods which RemoteCallbackList provides are thread-safe.
    private final RemoteCallbackList<IPartnerAIDLServiceCallback> mCallbacks =
        new RemoteCallbackList<IPartnerAIDLServiceCallback>();
    
    // Handler to send data when callback is called.
    private static class ServiceHandler extends Handler{
    private Context mContext;
    private RemoteCallbackList<IPartnerAIDLServiceCallback> mCallbacks;
    private int mValue = 0;
    
    public ServiceHandler(Context context, RemoteCallbackList<IPartnerAIDLServiceCallback> callback, int value){
        this.mContext = context;
        this.mCallbacks = callback;
        this.mValue = value;
    }
    
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case REPORT_MSG: {
                if(mCallbacks == null){
                    return;
                }
                // Start broadcast
                // To call back on to the registered clients, use beginBroadcast().
                // beginBroadcast() makes a copy of the currently registered callback list.
                final int N = mCallbacks.beginBroadcast();
                for (int i = 0; i < N; i++) {
                    IPartnerAIDLServiceCallback target = mCallbacks.getBroadcastItem(i);
                    try {
                        // *** POINT 5 *** Information that is granted to disclose to partner applications can be returned.
                        target.valueChanged("Information disclosed to partner application (callback from Service) No." + (++mValue));
                    } catch (RemoteException e) {
                        // Callbacks are managed by RemoteCallbackList, do not unregister callbacks here.
                        // RemoteCallbackList.kill() unregister all callbacks
                    }
                }
                // finishBroadcast() cleans up the state of a broadcast previously initiated by calling beginBroadcast().
                mCallbacks.finishBroadcast();
                // Repeat after 10 seconds
                sendEmptyMessageDelayed(REPORT_MSG, 10000);
                break;
            }
            case GETINFO_MSG: {
                if(mContext != null) {
                    Toast.makeText(mContext,
                        (String) msg.obj, Toast.LENGTH_LONG).show();
                }
                break;
            }
            default:
                super.handleMessage(msg);
                break;
        } // switch
    }
    
    protected final ServiceHandler mHandler = new ServiceHandler(this, mCallbacks, mValue);
    
    // Interfaces defined in AIDL
    private final IPartnerAIDLService.Stub mBinder = new IPartnerAIDLService.Stub() {
        private boolean checkPartner() {
            Context ctx = PartnerAIDLService.this;
            if (!PartnerAIDLService.checkPartner(ctx, Utils.getPackageNameFromUid(ctx, getCallingUid()))) {
                mHandler.post(new Runnable(){
                    @Override
                    public void run(){
                        Toast.makeText(PartnerAIDLService.this, "Requesting application is not partner application.", Toast.LENGTH_LONG).show();
                    }
                });
                return false;
            }
            return true;
        }
        
        public String getInfo(String param) {
            // *** POINT 2 *** Verify that the certificate of the requesting application has been registered in the own white list.
            if (!checkPartner()) {
                return null;
            }
            // *** POINT 4 *** Handle the received intent carefully and securely,
            // even though the intent was sent from a partner application
            // Omitted, since this is a sample. Please refer to "3.2 Handling Input Data Carefully and Securely."
            Message msg = new Message();
            msg.what = GETINFO_MSG;
            msg.obj = String.format("Method calling from partner application. Recieved ¥"%s¥"", param);
            PartnerAIDLService.this.mHandler.sendMessage(msg);
            // *** POINT 5 *** Return only information that is granted to be disclosed to a partner application.
            return "Information disclosed to partner application (method from Service)";
        }
        
        public void unregisterCallback(IPartnerAIDLServiceCallback cb) {
            // *** POINT 2 *** Verify that the certificate of the requesting application has been registered in the own white list.
            if (!checkPartner()) {
                return;
            }
            if (cb != null) mCallbacks.unregister(cb);
        }
    };
    
    @Override
    public IBinder onBind(Intent intent) {
        // *** POINT 3 *** Verify that the certificate of the requesting application has been registered in the own white list.
        // So requesting application must be validated in methods defined in AIDL every time.
        return mBinder;
    }
    
    @Override
    public void onCreate() {
        Toast.makeText(this, this.getClass().getSimpleName() + " - onCreate()", Toast.LENGTH_SHORT).show();
        // During service is running, inform the incremented number periodically.
        mHandler.sendEmptyMessage(REPORT_MSG);
    }
    
    @Override
    public void onDestroy() {
        Toast.makeText(this, this.getClass().getSimpleName() + " - onDestroy()", Toast.LENGTH_SHORT).show();
        // Unregister all callbacks
        mCallbacks.kill();
        mHandler.removeMessages(REPORT_MSG);
    }
}

PkgCertWhitelists.java

package org.jssec.android.shared;

import java.util.HashMap;
import java.util.Map;
import android.content.Context;

public class PkgCertWhitelists {

    private Map<String, String> mWhitelists = new HashMap<String, String>();

    public boolean add(String pkgname, String sha256) {
        if (pkgname == null) return false;
        if (sha256 == null) return false;
        sha256 = sha256.replaceAll(" ", "");
        if (sha256.length() != 64) return false; // SHA-256 -> 32 bytes -> 64 chars
        sha256 = sha256.toUpperCase();
        if (sha256.replaceAll("[0-9A-F]+", "").length() != 0) return false; // found non hex char
        mWhitelists.put(pkgname, sha256);
        return true;
    }
    
    public boolean test(Context ctx, String pkgname) {
        // Get the correct hash value which corresponds to pkgname.
        String correctHash = mWhitelists.get(pkgname);
        // Compare the actual hash value of pkgname with the correct hash value.
        return PkgCert.test(ctx, pkgname, correctHash);
    }
}

PkgCert.java

package org.jssec.android.shared;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.Signature;

public class PkgCert {

    public static boolean test(Context ctx, String pkgname, String correctHash) {
        if (correctHash == null) return false;
        correctHash = correctHash.replaceAll(" ", "");
        return correctHash.equals(hash(ctx, pkgname));
    }
    
    public static String hash(Context ctx, String pkgname) {
        if (pkgname == null) return null;
        try {
            PackageManager pm = ctx.getPackageManager();
            PackageInfo pkginfo = pm.getPackageInfo(pkgname, PackageManager.GET_SIGNATURES);
            if (pkginfo.signatures.length != 1) return null; // Will not handle multiple signatures.
            Signature sig = pkginfo.signatures[0];
            byte[] cert = sig.toByteArray();
            byte[] sha256 = computeSha256(cert);
            return byte2hex(sha256);
        } catch (NameNotFoundException e) {
            return null;
        }
    }

    private static byte[] computeSha256(byte[] data) {
        try {
            return MessageDigest.getInstance("SHA-256").digest(data);
        } catch (NoSuchAlgorithmException e) {
            return null;
        }
    }
    
    private static String byte2hex(byte[] data) {
        if (data == null) return null;
        final StringBuilder hexadecimal = new StringBuilder();
        for (final byte b : data) {
            hexadecimal.append(String.format("%02X", b));
        }
        return hexadecimal.toString();
    }
}

下面是使用伙伴服务的活动代码：

要点（使用服务）：

验证目标应用的证书是否已在自己的白名单中注册。
仅返回公开给伙伴应用的信息。
使用显式意图调用伙伴服务。
即使数据来自伙伴应用，也要小心并安全地处理收到的结果数据。

ExclusiveAIDLUserActivity.java

package org.jssec.android.service.partnerservice.aidluser;

import org.jssec.android.service.partnerservice.aidl.IPartnerAIDLService;
import org.jssec.android.service.partnerservice.aidl.IPartnerAIDLServiceCallback;
import org.jssec.android.shared.PkgCertWhitelists;
import org.jssec.android.shared.Utils;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.RemoteException;
import android.view.View;
import android.widget.Toast;

public class PartnerAIDLUserActivity extends Activity {
    
    private boolean mIsBound;
    private Context mContext;
    private final static int MGS_VALUE_CHANGED = 1;
    // *** POINT 6 *** Verify if the certificate of the target application has been registered in the own white list.
    private static PkgCertWhitelists sWhitelists = null;
    
    private static void buildWhitelists(Context context) {
        boolean isdebug = Utils.isDebuggable(context);
        sWhitelists = new PkgCertWhitelists();
        // Register certificate hash value of partner service application "org.jssec.android.service.partnerservice.aidl"
        sWhitelists.add("org.jssec.android.service.partnerservice.aidl", isdebug ?
            // Certificate hash value of debug.keystore "androiddebugkey"
            "0EFB7236 328348A9 89718BAD DF57F544 D5CCB4AE B9DB34BC 1E29DD26 F77C8255" :
            // Certificate hash value of keystore "my company key"
            "D397D343 A5CBC10F 4EDDEB7C A10062DE 5690984F 1FB9E88B D7B3A7C2 42E142CA");
            // Register other partner service applications in the same way
    }
    
    private static boolean checkPartner(Context context, String pkgname) {
        if (sWhitelists == null) buildWhitelists(context);
        return sWhitelists.test(context, pkgname);
    }
    
    // Information about destination (requested) partner activity.
    private static final String TARGET_PACKAGE = "org.jssec.android.service.partnerservice.aidl";
    private static final String TARGET_CLASS = "org.jssec.android.service.partnerservice.aidl.PartnerAIDLService";
    
    private static class ReceiveHandler extends Handler{
        private Context mContext;
        public ReceiveHandler(Context context){
        this.mContext = context;
    }
    
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MGS_VALUE_CHANGED: {
                String info = (String)msg.obj;
                Toast.makeText(mContext, String.format("Received ¥"%s¥" with callback.", info), Toast.LENGTH_SHORT).show();
                break;
            }
            default:
                super.handleMessage(msg);
                break;
        } // switch
    }
    
    private final ReceiveHandler mHandler = new ReceiveHandler(this);
    
    // Interfaces defined in AIDL. Receive notice from service
    private final IPartnerAIDLServiceCallback.Stub mCallback =
    new IPartnerAIDLServiceCallback.Stub() {
        @Override
        public void valueChanged(String info) throws RemoteException {
            Message msg = mHandler.obtainMessage(MGS_VALUE_CHANGED, info);
            mHandler.sendMessage(msg);
        }
    };

    // Interfaces defined in AIDL. Inform service.
    private IPartnerAIDLService mService = null;
    // Connection used to connect with service. This is necessary when service is implemented with bindService().
    private ServiceConnection mConnection = new ServiceConnection() {
        // This is called when the connection with the service has been established.
        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {
            mService = IPartnerAIDLService.Stub.asInterface(service);
            try{
                // connect to service
                mService.registerCallback(mCallback);
            }catch(RemoteException e){
                // service stopped abnormally
            }
            Toast.makeText(mContext, "Connected to service", Toast.LENGTH_SHORT).show();
        }
        
        // This is called when the service stopped abnormally and connection is disconnected.
        @Override
        public void onServiceDisconnected(ComponentName className) {
            Toast.makeText(mContext, "Disconnected from service", Toast.LENGTH_SHORT).show();
        }
    };
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.partnerservice_activity);
        mContext = this;
    }
    
    // --- StartService control ---
    public void onStartServiceClick(View v) {
        // Start bindService
        doBindService();
    }
    
    public void onGetInfoClick(View v) {
        getServiceinfo();
    }
    
    public void onStopServiceClick(View v) {
        doUnbindService();
    }
    
    @Override
    public void onDestroy() {
        super.onDestroy();
        doUnbindService();
    }
    
    /**
    * Connect to service
    */
    private void doBindService() {
        if (!mIsBound){
        // *** POINT 6 *** Verify if the certificate of the target application has been registered in the own white list.
        if (!checkPartner(this, TARGET_PACKAGE)) {
            Toast.makeText(this, "Destination(Requested) sevice application is not registered in white list.", Toast.LENGTH_LONG).show();
            return;
        }
        Intent intent = new Intent();
        // *** POINT 7 *** Return only information that is granted to be disclosed to a partner application.
        intent.putExtra("PARAM", "Information disclosed to partner application");
        // *** POINT 8 *** Use the explicit intent to call a partner service.
        intent.setClassName(TARGET_PACKAGE, TARGET_CLASS);
        bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
        mIsBound = true;
        }
    }
    
    /**
    * Disconnect service
    */
    private void doUnbindService() {
        if (mIsBound) {
            // Unregister callbacks which have been registered.
            if(mService != null){
                try{
                    mService.unregisterCallback(mCallback);
                }catch(RemoteException e){
                    // Service stopped abnormally
                    // Omitted, since it' s sample.
                }
            }
            unbindService(mConnection);
            Intent intent = new Intent();
            // *** POINT 8 *** Use the explicit intent to call a partner service.
            intent.setClassName(TARGET_PACKAGE, TARGET_CLASS);
            stopService(intent);
            mIsBound = false;
        }
    }
    
    /**
    * Get information from service
    */
    void getServiceinfo() {
        if (mIsBound && mService != null) {
            String info = null;
            try {
                // *** POINT 7 *** Return only information that is granted to be disclosed to a partner application.
                info = mService.getInfo("Information disclosed to partner application (method from activity)");
            } catch (RemoteException e) {
                e.printStackTrace();
            }
            // *** POINT 9 *** Handle the received result data carefully and securely,
            // even though the data came from a partner application.
            // Omitted, since this is a sample. Please refer to "3.2 Handling Input Data Carefully and Securely."
            Toast.makeText(mContext, String.format("Received ¥"%s¥" from service.", info), Toast.LENGTH_SHORT).show();
        }
    }
}

PkgCertWhitelists.java

package org.jssec.android.shared;

import java.util.HashMap;
import java.util.Map;
import android.content.Context;

public class PkgCertWhitelists {

    private Map<String, String> mWhitelists = new HashMap<String, String>();
    
    public boolean add(String pkgname, String sha256) {
        if (pkgname == null) return false;
        if (sha256 == null) return false;
        sha256 = sha256.replaceAll(" ", "");
        if (sha256.length() != 64) return false; // SHA-256 -> 32 bytes -> 64 chars
        sha256 = sha256.toUpperCase();
        if (sha256.replaceAll("[0-9A-F]+", "").length() != 0) return false; // found non hex char
        mWhitelists.put(pkgname, sha256);
        return true;
    }
    
    public boolean test(Context ctx, String pkgname) {
        // Get the correct hash value which corresponds to pkgname.
        String correctHash = mWhitelists.get(pkgname);
        // Compare the actual hash value of pkgname with the correct hash value.
        return PkgCert.test(ctx, pkgname, correctHash);
    }
}

PkgCert.java

package org.jssec.android.shared;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.Signature;

public class PkgCert {

    public static boolean test(Context ctx, String pkgname, String correctHash) {
        if (correctHash == null) return false;
        correctHash = correctHash.replaceAll(" ", "");
        return correctHash.equals(hash(ctx, pkgname));
    }
    
    public static String hash(Context ctx, String pkgname) {
        if (pkgname == null) return null;
        try {
            PackageManager pm = ctx.getPackageManager();
            PackageInfo pkginfo = pm.getPackageInfo(pkgname, PackageManager.GET_SIGNATURES);
            if (pkginfo.signatures.length != 1) return null; // Will not handle multiple signatures.
            Signature sig = pkginfo.signatures[0];
            byte[] cert = sig.toByteArray();
            byte[] sha256 = computeSha256(cert);
            return byte2hex(sha256);
        } catch (NameNotFoundException e) {
            return null;
        }
    }
    
    private static byte[] computeSha256(byte[] data) {
        try {
            return MessageDigest.getInstance("SHA-256").digest(data);
        } catch (NoSuchAlgorithmException e) {
            return null;
        }
    }
    
    private static String byte2hex(byte[] data) {
        if (data == null) return null;
        final StringBuilder hexadecimal = new StringBuilder();
        for (final byte b : data) {
            hexadecimal.append(String.format("%02X", b));
        }
        return hexadecimal.toString();
    }
}

安卓应用安全指南 (Android Application Secure Design/Secure Coding Guidebook)

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