最近隐私政策真是让人头疼，开始针对敏感API了，经过一番折腾之后，改了不少问题，起初看到 这样的一个报告：

App首次启动，同意隐私政策前，存在读取存储信息的行为。 有点不可理解，看了下堆栈信息：

image.png

emu，竟然是AndPermission 开源库搞的。然后开始分析：

我们先找到这个所谓的FileProvider的源码看看：

/*
 * Copyright 2018 Zhenjie Yan
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.yanzhenjie.permission;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.Context;
import android.content.pm.PackageManager;
import android.content.pm.ProviderInfo;
import android.content.res.XmlResourceParser;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.os.ParcelFileDescriptor;
import android.provider.OpenableColumns;
import android.text.TextUtils;
import android.webkit.MimeTypeMap;

import org.xmlpull.v1.XmlPullParserException;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import static org.xmlpull.v1.XmlPullParser.END_DOCUMENT;
import static org.xmlpull.v1.XmlPullParser.START_TAG;

/**
 * <p>Copied from the support library v27.1.1.</p>
 * Created by YanZhenjie on 2018/4/28.
 */
public class FileProvider extends ContentProvider {

    private static final String[] COLUMNS = {OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE};

    private static final String META_DATA_FILE_PROVIDER_PATHS = "android.support.FILE_PROVIDER_PATHS";

    private static final String TAG_ROOT_PATH = "root-path";
    private static final String TAG_FILES_PATH = "files-path";
    private static final String TAG_CACHE_PATH = "cache-path";
    private static final String TAG_EXTERNAL = "external-path";
    private static final String TAG_EXTERNAL_FILES = "external-files-path";
    private static final String TAG_EXTERNAL_CACHE = "external-cache-path";
    private static final String TAG_EXTERNAL_MEDIA = "external-media-path";

    private static final String ATTR_NAME = "name";
    private static final String ATTR_PATH = "path";

    private static final File DEVICE_ROOT = new File("/");

    private static final HashMap<String, PathStrategy> sCache = new HashMap<>();

    private PathStrategy mStrategy;

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

    @Override
    public void attachInfo(Context context, ProviderInfo info) {
        super.attachInfo(context, info);
        if (info.exported) {
            throw new SecurityException("Provider must not be exported");
        }
        if (!info.grantUriPermissions) {
            throw new SecurityException("Provider must grant uri permissions");
        }

        mStrategy = getPathStrategy(context, info.authority);
    }

    public static Uri getUriForFile(Context context, String authority, File file) {
        final PathStrategy strategy = getPathStrategy(context, authority);
        return strategy.getUriForFile(file);
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        final File file = mStrategy.getFileForUri(uri);
        if (projection == null) {
            projection = COLUMNS;
        }

        String[] cols = new String[projection.length];
        Object[] values = new Object[projection.length];
        int i = 0;
        for (String col : projection) {
            if (OpenableColumns.DISPLAY_NAME.equals(col)) {
                cols[i] = OpenableColumns.DISPLAY_NAME;
                values[i++] = file.getName();
            } else if (OpenableColumns.SIZE.equals(col)) {
                cols[i] = OpenableColumns.SIZE;
                values[i++] = file.length();
            }
        }

        cols = copyOf(cols, i);
        values = copyOf(values, i);

        final MatrixCursor cursor = new MatrixCursor(cols, 1);
        cursor.addRow(values);
        return cursor;
    }

    @Override
    public String getType(Uri uri) {
        final File file = mStrategy.getFileForUri(uri);

        final int lastDot = file.getName().lastIndexOf('.');
        if (lastDot >= 0) {
            final String extension = file.getName().substring(lastDot + 1);
            final String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
            if (mime != null) {
                return mime;
            }
        }
        return "application/octet-stream";
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        throw new UnsupportedOperationException("No external inserts");
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        throw new UnsupportedOperationException("No external updates");
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        final File file = mStrategy.getFileForUri(uri);
        return file.delete() ? 1 : 0;
    }

    @Override
    public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException {
        final File file = mStrategy.getFileForUri(uri);
        final int fileMode = modeToMode(mode);
        return ParcelFileDescriptor.open(file, fileMode);
    }

    private static PathStrategy getPathStrategy(Context context, String authority) {
        PathStrategy strategy;
        synchronized (sCache) {
            strategy = sCache.get(authority);
            if (strategy == null) {
                try {
                    strategy = parsePathStrategy(context, authority);
                } catch (IOException e) {
                    throw new IllegalArgumentException(
                        "Failed to parse " + META_DATA_FILE_PROVIDER_PATHS + " meta-data", e);
                } catch (XmlPullParserException e) {
                    throw new IllegalArgumentException(
                        "Failed to parse " + META_DATA_FILE_PROVIDER_PATHS + " meta-data", e);
                }
                sCache.put(authority, strategy);
            }
        }
        return strategy;
    }

    private static PathStrategy parsePathStrategy(Context context, String authority)
        throws IOException, XmlPullParserException {
        final SimplePathStrategy strategy = new SimplePathStrategy(authority);
        final ProviderInfo info = context.getPackageManager()
            .resolveContentProvider(authority, PackageManager.GET_META_DATA);
        final XmlResourceParser in = info.loadXmlMetaData(context.getPackageManager(), META_DATA_FILE_PROVIDER_PATHS);
        if (in == null) {
            throw new IllegalArgumentException("Missing " + META_DATA_FILE_PROVIDER_PATHS + " meta-data");
        }

        int type;
        while ((type = in.next()) != END_DOCUMENT) {
            if (type == START_TAG) {
                final String tag = in.getName();

                final String name = in.getAttributeValue(null, ATTR_NAME);
                String path = in.getAttributeValue(null, ATTR_PATH);

                File target = null;
                if (TAG_ROOT_PATH.equals(tag)) {
                    target = DEVICE_ROOT;
                } else if (TAG_FILES_PATH.equals(tag)) {
                    target = context.getFilesDir();
                } else if (TAG_CACHE_PATH.equals(tag)) {
                    target = context.getCacheDir();
                } else if (TAG_EXTERNAL.equals(tag)) {
                    target = Environment.getExternalStorageDirectory();
                } else if (TAG_EXTERNAL_FILES.equals(tag)) {
                    File[] externalFilesDirs = getExternalFilesDirs(context, null);
                    if (externalFilesDirs.length > 0) {
                        target = externalFilesDirs[0];
                    }
                } else if (TAG_EXTERNAL_CACHE.equals(tag)) {
                    File[] externalCacheDirs = getExternalCacheDirs(context);
                    if (externalCacheDirs.length > 0) {
                        target = externalCacheDirs[0];
                    }
                } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && TAG_EXTERNAL_MEDIA.equals(tag)) {
                    File[] externalMediaDirs = context.getExternalMediaDirs();
                    if (externalMediaDirs.length > 0) {
                        target = externalMediaDirs[0];
                    }
                }

                if (target != null) {
                    strategy.addRoot(name, buildPath(target, path));
                }
            }
        }

        return strategy;
    }

    interface PathStrategy {

        Uri getUriForFile(File file);

        File getFileForUri(Uri uri);
    }

    static class SimplePathStrategy implements PathStrategy {

        private final String mAuthority;
        private final HashMap<String, File> mRoots = new HashMap<String, File>();

        SimplePathStrategy(String authority) {
            mAuthority = authority;
        }

        void addRoot(String name, File root) {
            if (TextUtils.isEmpty(name)) {
                throw new IllegalArgumentException("Name must not be empty");
            }

            try {
                root = root.getCanonicalFile();
            } catch (IOException e) {
                throw new IllegalArgumentException("Failed to resolve canonical path for " + root, e);
            }

            mRoots.put(name, root);
        }

        @Override
        public Uri getUriForFile(File file) {
            String path;
            try {
                path = file.getCanonicalPath();
            } catch (IOException e) {
                throw new IllegalArgumentException("Failed to resolve canonical path for " + file);
            }

            Map.Entry<String, File> mostSpecific = null;
            for (Map.Entry<String, File> root : mRoots.entrySet()) {
                final String rootPath = root.getValue().getPath();
                boolean invalidMost = mostSpecific == null ||
                    rootPath.length() > mostSpecific.getValue().getPath().length();
                if (path.startsWith(rootPath) && invalidMost) {
                    mostSpecific = root;
                }
            }

            if (mostSpecific == null) {
                throw new IllegalArgumentException("Failed to find configured root that contains " + path);
            }

            final String rootPath = mostSpecific.getValue().getPath();
            if (rootPath.endsWith("/")) {
                path = path.substring(rootPath.length());
            } else {
                path = path.substring(rootPath.length() + 1);
            }

            path = Uri.encode(mostSpecific.getKey()) + '/' + Uri.encode(path, "/");
            return new Uri.Builder().scheme("content").authority(mAuthority).encodedPath(path).build();
        }

        @Override
        public File getFileForUri(Uri uri) {
            String path = uri.getEncodedPath();

            final int splitIndex = path.indexOf('/', 1);
            final String tag = Uri.decode(path.substring(1, splitIndex));
            path = Uri.decode(path.substring(splitIndex + 1));

            final File root = mRoots.get(tag);
            if (root == null) {
                throw new IllegalArgumentException("Unable to find configured root for " + uri);
            }

            File file = new File(root, path);
            try {
                file = file.getCanonicalFile();
            } catch (IOException e) {
                throw new IllegalArgumentException("Failed to resolve canonical path for " + file);
            }

            if (!file.getPath().startsWith(root.getPath())) {
                throw new SecurityException("Resolved path jumped beyond configured root");
            }
            return file;
        }
    }

    private static int modeToMode(String mode) {
        int modeBits;
        if ("r".equals(mode)) {
            modeBits = ParcelFileDescriptor.MODE_READ_ONLY;
        } else if ("w".equals(mode) || "wt".equals(mode)) {
            modeBits = ParcelFileDescriptor.MODE_WRITE_ONLY | ParcelFileDescriptor.MODE_CREATE |
                ParcelFileDescriptor.MODE_TRUNCATE;
        } else if ("wa".equals(mode)) {
            modeBits = ParcelFileDescriptor.MODE_WRITE_ONLY | ParcelFileDescriptor.MODE_CREATE |
                ParcelFileDescriptor.MODE_APPEND;
        } else if ("rw".equals(mode)) {
            modeBits = ParcelFileDescriptor.MODE_READ_WRITE | ParcelFileDescriptor.MODE_CREATE;
        } else if ("rwt".equals(mode)) {
            modeBits = ParcelFileDescriptor.MODE_READ_WRITE | ParcelFileDescriptor.MODE_CREATE |
                ParcelFileDescriptor.MODE_TRUNCATE;
        } else {
            throw new IllegalArgumentException("Invalid mode: " + mode);
        }
        return modeBits;
    }

    private static File buildPath(File base, String... segments) {
        File cur = base;
        for (String segment : segments) {
            if (segment != null) {
                cur = new File(cur, segment);
            }
        }
        return cur;
    }

    private static String[] copyOf(String[] original, int newLength) {
        final String[] result = new String[newLength];
        System.arraycopy(original, 0, result, 0, newLength);
        return result;
    }

    private static Object[] copyOf(Object[] original, int newLength) {
        final Object[] result = new Object[newLength];
        System.arraycopy(original, 0, result, 0, newLength);
        return result;
    }

    private static File[] getExternalFilesDirs(Context context, String type) {
        if (Build.VERSION.SDK_INT >= 19) {
            return context.getExternalFilesDirs(type);
        } else {
            return new File[] {context.getExternalFilesDir(type)};
        }
    }

    public static File[] getExternalCacheDirs(Context context) {
        if (Build.VERSION.SDK_INT >= 19) {
            return context.getExternalCacheDirs();
        } else {
            return new File[] {context.getExternalCacheDir()};
        }
    }
}

通过阅读，确实，在相应位置API，进行了调用，只要你的APP中声明了 xml 外部存储的配置， 然后匹配到了他在query 函数里的tag，那他就会调用到该敏感API。那发现问题了，如何解决呢？

思路有两个：

第一：看下是否有可以配置的地方。翻阅了github，该工程已经4年没更新了，emu...有点惆怅，那只能自己搞了，那去除xml 中external-files-path 配置是否可行呢，当然，如果应用是内部存储处理，那当然可行，这也不失为一种解决方法。那如果没有呢？

第二：还记得AndroidManifest node 属性吗，可以将该FileProvider 移除掉，然后自己用到FileProvider的地方，采用自定义的进行处理。阅读了源码之后，你会发现，这个定义的FilerProvider，并没有啥鸟用，只是在AndPermission中提供了一个便捷的API，让使用者使用而已。贴上解决方案，结束战斗：

     <provider
            android:name="com.yanzhenjie.permission.FileProvider"
            tools:node="remove"
            />