4.3.1 示例代码
4.3.1.2 创建/..

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

4.3.1.1 创建/使用私有内容供应器

私有内容供应器是只由单一应用使用的内容提供者，它是最安全的内容供应器 [8]。

下面展示了如何实现私有内容供应器的示例代码。

要点（创建内容供应器）：

  1. 将导出属性显式设置为false。

  2. 即使数据来自相同应用，也应该小心并安全地处理收到的请求数据。

  3. 可以发送敏感信息，因为它在同一应用内发送和接收所有信息。

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.jssec.android.provider.privateprovider">
    
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".PrivateUserActivity"
            android:label="@string/app_name"
            android:exported="true" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <!-- *** POINT 1 *** Explicitly set the exported attribute to false. -->
        <provider
        android:name=".PrivateProvider"
        android:authorities="org.jssec.android.provider.privateprovider"
        android:exported="false" />
    </application>
</manifest>

PrivateProvider.java

package org.jssec.android.provider.privateprovider;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.net.Uri;

public class PrivateProvider extends ContentProvider {

    public static final String AUTHORITY = "org.jssec.android.provider.privateprovider";
    public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.org.jssec.contenttype";
    public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.org.jssec.contenttype";
    // Expose the interface that the Content Provider provides.

    public interface Download {
        public static final String PATH = "downloads";
        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/" + PATH);
    }

    public interface Address {
        public static final String PATH = "addresses";
        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/" + PATH);
    }

    // UriMatcher
    private static final int DOWNLOADS_CODE = 1;
    private static final int DOWNLOADS_ID_CODE = 2;
    private static final int ADDRESSES_CODE = 3;
    private static final int ADDRESSES_ID_CODE = 4;
    private static UriMatcher sUriMatcher;

    static {
        sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        sUriMatcher.addURI(AUTHORITY, Download.PATH, DOWNLOADS_CODE);
        sUriMatcher.addURI(AUTHORITY, Download.PATH + "/#", DOWNLOADS_ID_CODE);
        sUriMatcher.addURI(AUTHORITY, Address.PATH, ADDRESSES_CODE);
        sUriMatcher.addURI(AUTHORITY, Address.PATH + "/#", ADDRESSES_ID_CODE);
    }

    // Since this is a sample program,
    // query method returns the following fixed result always without using database.
    private static MatrixCursor sAddressCursor = new MatrixCursor(new String[] { "_id", "city" });

    static {
        sAddressCursor.addRow(new String[] { "1", "New York" });
        sAddressCursor.addRow(new String[] { "2", "Longon" });
        sAddressCursor.addRow(new String[] { "3", "Paris" });
    }

    private static MatrixCursor sDownloadCursor = new MatrixCursor(new String[] { "_id", "path" });

    static {
        sDownloadCursor.addRow(new String[] { "1", "/sdcard/downloads/sample.jpg" });
        sDownloadCursor.addRow(new String[] { "2", "/sdcard/downloads/sample.txt" });
    }

    @Override
    public boolean onCreate() {
        return true;
    }

    @Override
    public String getType(Uri uri) {
        // *** POINT 2 *** Handle the received request data carefully and securely,
        // even though the data comes from the same application.
        // Here, whether uri is within expectations or not, is verified by UriMatcher#match() and switch case.
        // Checking for other parameters are omitted here, due to sample.
        // Please refer to "3.2 Handle Input Data Carefully and Securely."
        // *** POINT 3 *** Sensitive information can be sent since it is sending and receiving all within the same application.
        // However, the result of getType rarely has the sensitive meaning.
        switch (sUriMatcher.match(uri)) {
            case DOWNLOADS_CODE:
            case ADDRESSES_CODE:
                return CONTENT_TYPE;
            case DOWNLOADS_ID_CODE:
            case ADDRESSES_ID_CODE:
                return CONTENT_ITEM_TYPE;
            default:
                throw new IllegalArgumentException("Invalid URI:" + uri);
        }
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
        String[] selectionArgs, String sortOrder) {
        // *** POINT 2 *** Handle the received request data carefully and securely,
        // even though the data comes from the same application.
        // Here, whether uri is within expectations or not, is verified by UriMatcher#match() and switch case.
        // Checking for other parameters are omitted here, due to sample.
        // Please refer to "3.2 Handle Input Data Carefully and Securely."
        // *** POINT 3 *** Sensitive information can be sent since it is sending and receiving all within the same application.
        // It depends on application whether the query result has sensitive meaning or not.
        switch (sUriMatcher.match(uri)) {
            case DOWNLOADS_CODE:
            case DOWNLOADS_ID_CODE:
                return sDownloadCursor;
            case ADDRESSES_CODE:
            case ADDRESSES_ID_CODE:
                return sAddressCursor;
            default:
                throw new IllegalArgumentException("Invalid URI:" + uri);
        }
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // *** POINT 2 *** Handle the received request data carefully and securely,
        // even though the data comes from the same application.
        // Here, whether uri is within expectations or not, is verified by UriMatcher#match() and switch case.
        // Checking for other parameters are omitted here, due to sample.
        // Please refer to "3.2 Handle Input Data Carefully and Securely."
        // *** POINT 3 *** Sensitive information can be sent since it is sending and receiving all within the same application.
        // It depends on application whether the issued ID has sensitive meaning or not.
        switch (sUriMatcher.match(uri)) {
            case DOWNLOADS_CODE:
                return ContentUris.withAppendedId(Download.CONTENT_URI, 3);
            case ADDRESSES_CODE:
                return ContentUris.withAppendedId(Address.CONTENT_URI, 4);
            default:
                throw new IllegalArgumentException("Invalid URI:" + uri);
        }
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
        String[] selectionArgs) {
        // *** POINT 2 *** Handle the received request data carefully and securely,
        // even though the data comes from the same application.
        // Here, whether uri is within expectations or not, is verified by UriMatcher#match() and switch case.
        // Checking for other parameters are omitted here, due to sample.
        // Please refer to "3.2 Handle Input Data Carefully and Securely."
        // *** POINT 3 *** Sensitive information can be sent since it is sending and receiving all within the same application.
        // It depends on application whether the number of updated records has sensitive meaning or not.
        switch (sUriMatcher.match(uri)) {
            case DOWNLOADS_CODE:
                return 5; // Return number of updated records
            case DOWNLOADS_ID_CODE:
                return 1;
            case ADDRESSES_CODE:
                return 15;
            case ADDRESSES_ID_CODE:
                return 1;
            default:
                throw new IllegalArgumentException("Invalid URI:" + uri);
        }
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // *** POINT 2 *** Handle the received request data carefully and securely,
        // even though the data comes from the same application.
        // Here, whether uri is within expectations or not, is verified by UriMatcher#match() and switch case.
        // Checking for other parameters are omitted here, due to sample.
        // Please refer to "3.2 Handle Input Data Carefully and Securely."
        // *** POINT 3 *** Sensitive information can be sent since it is sending and receiving all within the same application.
        // It depends on application whether the number of deleted records has sensitive meaning or not.
        switch (sUriMatcher.match(uri)) {
            case DOWNLOADS_CODE:
                return 10; // Return number of deleted records
            case DOWNLOADS_ID_CODE:
                return 1;
            case ADDRESSES_CODE:
                return 20;
            case ADDRESSES_ID_CODE:
                return 1;
            default:
                throw new IllegalArgumentException("Invalid URI:" + uri);
        }
    }

}

下面是活动的示例，它使用私有内容供应器。

要点（使用内容供应器）：

  1. 敏感信息可以发送，因为目标供应器在相同应用中。

  2. 小心和安全地处理收到的结果数据，即使数据来自相同应用。

PrivateUserActivity.java

package org.jssec.android.provider.privateprovider;

import android.app.Activity;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class PrivateUserActivity extends Activity {
    
    public void onQueryClick(View view) {
        logLine("[Query]");
        Cursor cursor = null;
        try {
            // *** POINT 4 *** Sensitive information can be sent since the destination provider is in the same application.
            cursor = getContentResolver().query(
                PrivateProvider.Download.CONTENT_URI, null, null, null, null);
            // *** POINT 5 *** Handle received result data carefully and securely,
            // even though the data comes from the same application.
            // Omitted, since this is a sample. Please refer to "3.2 Handling Input Data Carefully and Securely."
            if (cursor == null) {
                logLine(" null cursor");
            } else {
                boolean moved = cursor.moveToFirst();
                while (moved) {
                    logLine(String.format(" %d, %s", cursor.getInt(0), cursor.getString(1)));
                    moved = cursor.moveToNext();
                }
            }
        }
        finally {
            if (cursor != null) cursor.close();
        }
    }
    
    public void onInsertClick(View view) {
        logLine("[Insert]");
        // *** POINT 4 *** Sensitive information can be sent since the destination provider is in the same application.
        Uri uri = getContentResolver().insert(PrivateProvider.Download.CONTENT_URI, null);
        // *** POINT 5 *** Handle received result data carefully and securely,
        // even though the data comes from the same application.
        // Omitted, since this is a sample. Please refer to "3.2 Handling Input Data Carefully and Securely."
        logLine(" uri:" + uri);
    }
    
    public void onUpdateClick(View view) {
    logLine("[Update]");
        // *** POINT 4 *** Sensitive information can be sent since the destination provider is in the same application.
        int count = getContentResolver().update(PrivateProvider.Download.CONTENT_URI, null, null, null);
        // *** POINT 5 *** Handle received result data carefully and securely,
        // even though the data comes from the same application.
        // Omitted, since this is a sample. Please refer to "3.2 Handling Input Data Carefully and Securely."
        logLine(String.format(" %s records updated", count));
    }
    
    public void onDeleteClick(View view) {
    logLine("[Delete]");
        // *** POINT 4 *** Sensitive information can be sent since the destination provider is in the same application.
        int count = getContentResolver().delete(
        PrivateProvider.Download.CONTENT_URI, null, null);
        // *** POINT 5 *** Handle received result data carefully and securely,
        // even though the data comes from the same application.
        // Omitted, since this is a sample. Please refer to "3.2 Handling Input Data Carefully and Securely."
        logLine(String.format(" %s records deleted", count));
    }
    
    private TextView mLogView;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mLogView = (TextView)findViewById(R.id.logview);
    }
    
    private void logLine(String line) {
        mLogView.append(line);
        mLogView.append("¥n");
    }
}
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