1 /* 2 * Copyright 2022 Google LLC 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 package com.google.android.libraries.mobiledatadownload.file.openers; 17 18 import android.annotation.SuppressLint; 19 import android.net.Uri; 20 import android.util.Base64; 21 import com.google.android.libraries.mobiledatadownload.file.OpenContext; 22 import com.google.android.libraries.mobiledatadownload.file.Opener; 23 import com.google.common.io.ByteStreams; 24 import com.google.errorprone.annotations.CanIgnoreReturnValue; 25 import java.io.File; 26 import java.io.FileNotFoundException; 27 import java.io.IOException; 28 import java.io.InputStream; 29 import java.io.OutputStream; 30 import java.security.MessageDigest; 31 import java.security.NoSuchAlgorithmException; 32 import javax.annotation.Nullable; 33 34 /** 35 * Opener for loading URIs as shared libraries. 36 * 37 * <p>In many cases, the URI cannot be loaded directly and must be copied to a cache directory 38 * first. Caller is responsible for ensuring that this cache directory is cleaned periodically, but 39 * they can do so using a MobStore URI with TTL, LRU, or other garbage collection method. 40 * 41 * <p>WARNING: This opener does no validation and assumes that the data it receives is good. Note 42 * that MobStore can validate a checksum present in the URI. 43 * 44 * <p>TODO Consider requiring validation of checksum. 45 * 46 * <p>Usage: <code> 47 * storage.open(uri, SystemLibraryOpener.create().withCacheDirectory(cacheRootUri)) 48 * </code> 49 */ 50 public final class SystemLibraryOpener implements Opener<Void> { 51 52 @Nullable private Uri cacheDirectory; 53 SystemLibraryOpener()54 private SystemLibraryOpener() {} 55 56 @CanIgnoreReturnValue withCacheDirectory(Uri dir)57 public SystemLibraryOpener withCacheDirectory(Uri dir) { 58 this.cacheDirectory = dir; 59 return this; 60 } 61 create()62 public static SystemLibraryOpener create() { 63 return new SystemLibraryOpener(); 64 } 65 66 @Override 67 @SuppressLint("UnsafeDynamicallyLoadedCode") // System.load is needed to load from arbitrary Uris open(OpenContext openContext)68 public Void open(OpenContext openContext) throws IOException { 69 File file = null; 70 try { 71 // NOTE: could be backend().openFile() if we added to Backend interface. 72 file = ReadFileOpener.create().open(openContext); 73 System.load(file.getAbsolutePath()); 74 } catch (IOException e) { 75 if (cacheDirectory == null) { 76 throw new IOException("Cannot directly open file and no cache directory available."); 77 } 78 Uri cachedUri = 79 cacheDirectory 80 .buildUpon() 81 .appendPath(hashedLibraryName(openContext.originalUri())) 82 .build(); 83 try { 84 file = openContext.storage().open(cachedUri, ReadFileOpener.create()); 85 System.load(file.getAbsolutePath()); 86 } catch (FileNotFoundException e2) { 87 // NOTE: this could be extracted as CopyOpener if the need arises 88 try (InputStream from = 89 openContext.storage().open(openContext.originalUri(), ReadStreamOpener.create()); 90 OutputStream to = openContext.storage().open(cachedUri, WriteStreamOpener.create())) { 91 ByteStreams.copy(from, to); 92 to.flush(); 93 } 94 file = openContext.storage().open(cachedUri, ReadFileOpener.create()); 95 System.load(file.getAbsolutePath()); 96 } 97 } 98 return null; // Required by Void return type. 99 } 100 hashedLibraryName(Uri uri)101 private static String hashedLibraryName(Uri uri) { 102 try { 103 MessageDigest digest = MessageDigest.getInstance("MD5"); 104 byte[] bytes = digest.digest(uri.toString().getBytes()); 105 String hash = Base64.encodeToString(bytes, Base64.NO_WRAP | Base64.URL_SAFE); 106 return ".mobstore-lib." + hash + ".so"; 107 } catch (NoSuchAlgorithmException e) { 108 // Unreachable. 109 throw new RuntimeException("Missing MD5 algorithm implementation", e); 110 } 111 } 112 } 113