1/* 2 * Copyright (C) 2013 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 17package android.support.v4.content; 18 19import static org.xmlpull.v1.XmlPullParser.END_DOCUMENT; 20import static org.xmlpull.v1.XmlPullParser.START_TAG; 21 22import android.content.ContentProvider; 23import android.content.ContentValues; 24import android.content.Context; 25import android.content.Intent; 26import android.content.pm.PackageManager; 27import android.content.pm.ProviderInfo; 28import android.content.res.XmlResourceParser; 29import android.database.Cursor; 30import android.database.MatrixCursor; 31import android.net.Uri; 32import android.os.Environment; 33import android.os.ParcelFileDescriptor; 34import android.provider.OpenableColumns; 35import android.support.annotation.GuardedBy; 36import android.text.TextUtils; 37import android.webkit.MimeTypeMap; 38 39import org.xmlpull.v1.XmlPullParserException; 40 41import java.io.File; 42import java.io.FileNotFoundException; 43import java.io.IOException; 44import java.util.HashMap; 45import java.util.Map; 46 47/** 48 * FileProvider is a special subclass of {@link ContentProvider} that facilitates secure sharing 49 * of files associated with an app by creating a <code>content://</code> {@link Uri} for a file 50 * instead of a <code>file:///</code> {@link Uri}. 51 * <p> 52 * A content URI allows you to grant read and write access using 53 * temporary access permissions. When you create an {@link Intent} containing 54 * a content URI, in order to send the content URI 55 * to a client app, you can also call {@link Intent#setFlags(int) Intent.setFlags()} to add 56 * permissions. These permissions are available to the client app for as long as the stack for 57 * a receiving {@link android.app.Activity} is active. For an {@link Intent} going to a 58 * {@link android.app.Service}, the permissions are available as long as the 59 * {@link android.app.Service} is running. 60 * <p> 61 * In comparison, to control access to a <code>file:///</code> {@link Uri} you have to modify the 62 * file system permissions of the underlying file. The permissions you provide become available to 63 * <em>any</em> app, and remain in effect until you change them. This level of access is 64 * fundamentally insecure. 65 * <p> 66 * The increased level of file access security offered by a content URI 67 * makes FileProvider a key part of Android's security infrastructure. 68 * <p> 69 * This overview of FileProvider includes the following topics: 70 * </p> 71 * <ol> 72 * <li><a href="#ProviderDefinition">Defining a FileProvider</a></li> 73 * <li><a href="#SpecifyFiles">Specifying Available Files</a></li> 74 * <li><a href="#GetUri">Retrieving the Content URI for a File</li> 75 * <li><a href="#Permissions">Granting Temporary Permissions to a URI</a></li> 76 * <li><a href="#ServeUri">Serving a Content URI to Another App</a></li> 77 * </ol> 78 * <h3 id="ProviderDefinition">Defining a FileProvider</h3> 79 * <p> 80 * Since the default functionality of FileProvider includes content URI generation for files, you 81 * don't need to define a subclass in code. Instead, you can include a FileProvider in your app 82 * by specifying it entirely in XML. To specify the FileProvider component itself, add a 83 * <code><a href="{@docRoot}guide/topics/manifest/provider-element.html"><provider></a></code> 84 * element to your app manifest. Set the <code>android:name</code> attribute to 85 * <code>android.support.v4.content.FileProvider</code>. Set the <code>android:authorities</code> 86 * attribute to a URI authority based on a domain you control; for example, if you control the 87 * domain <code>mydomain.com</code> you should use the authority 88 * <code>com.mydomain.fileprovider</code>. Set the <code>android:exported</code> attribute to 89 * <code>false</code>; the FileProvider does not need to be public. Set the 90 * <a href="{@docRoot}guide/topics/manifest/provider-element.html#gprmsn" 91 * >android:grantUriPermissions</a> attribute to <code>true</code>, to allow you 92 * to grant temporary access to files. For example: 93 * <pre class="prettyprint"> 94 *<manifest> 95 * ... 96 * <application> 97 * ... 98 * <provider 99 * android:name="android.support.v4.content.FileProvider" 100 * android:authorities="com.mydomain.fileprovider" 101 * android:exported="false" 102 * android:grantUriPermissions="true"> 103 * ... 104 * </provider> 105 * ... 106 * </application> 107 *</manifest></pre> 108 * <p> 109 * If you want to override any of the default behavior of FileProvider methods, extend 110 * the FileProvider class and use the fully-qualified class name in the <code>android:name</code> 111 * attribute of the <code><provider></code> element. 112 * <h3 id="SpecifyFiles">Specifying Available Files</h3> 113 * A FileProvider can only generate a content URI for files in directories that you specify 114 * beforehand. To specify a directory, specify the its storage area and path in XML, using child 115 * elements of the <code><paths></code> element. 116 * For example, the following <code>paths</code> element tells FileProvider that you intend to 117 * request content URIs for the <code>images/</code> subdirectory of your private file area. 118 * <pre class="prettyprint"> 119 *<paths xmlns:android="http://schemas.android.com/apk/res/android"> 120 * <files-path name="my_images" path="images/"/> 121 * ... 122 *</paths> 123 *</pre> 124 * <p> 125 * The <code><paths></code> element must contain one or more of the following child elements: 126 * </p> 127 * <dl> 128 * <dt> 129 * <pre class="prettyprint"> 130 *<files-path name="<i>name</i>" path="<i>path</i>" /> 131 *</pre> 132 * </dt> 133 * <dd> 134 * Represents files in the <code>files/</code> subdirectory of your app's internal storage 135 * area. This subdirectory is the same as the value returned by {@link Context#getFilesDir() 136 * Context.getFilesDir()}. 137 * </dd> 138 * <dt> 139 * <pre> 140 *<cache-path name="<i>name</i>" path="<i>path</i>" /> 141 *</pre> 142 * <dt> 143 * <dd> 144 * Represents files in the cache subdirectory of your app's internal storage area. The root path 145 * of this subdirectory is the same as the value returned by {@link Context#getCacheDir() 146 * getCacheDir()}. 147 * </dd> 148 * <dt> 149 * <pre class="prettyprint"> 150 *<external-path name="<i>name</i>" path="<i>path</i>" /> 151 *</pre> 152 * </dt> 153 * <dd> 154 * Represents files in the root of the external storage area. The root path of this subdirectory 155 * is the same as the value returned by 156 * {@link Environment#getExternalStorageDirectory() Environment.getExternalStorageDirectory()}. 157 * </dd> 158 * <dt> 159 * <pre class="prettyprint"> 160 *<external-files-path name="<i>name</i>" path="<i>path</i>" /> 161 *</pre> 162 * </dt> 163 * <dd> 164 * Represents files in the root of your app's external storage area. The root path of this 165 * subdirectory is the same as the value returned by 166 * {@code Context#getExternalFilesDir(String) Context.getExternalFilesDir(null)}. 167 * </dd> 168 * <dt> 169 * <pre class="prettyprint"> 170 *<external-cache-path name="<i>name</i>" path="<i>path</i>" /> 171 *</pre> 172 * </dt> 173 * <dd> 174 * Represents files in the root of your app's external cache area. The root path of this 175 * subdirectory is the same as the value returned by 176 * {@link Context#getExternalCacheDir() Context.getExternalCacheDir()}. 177 * </dd> 178 * </dl> 179 * <p> 180 * These child elements all use the same attributes: 181 * </p> 182 * <dl> 183 * <dt> 184 * <code>name="<i>name</i>"</code> 185 * </dt> 186 * <dd> 187 * A URI path segment. To enforce security, this value hides the name of the subdirectory 188 * you're sharing. The subdirectory name for this value is contained in the 189 * <code>path</code> attribute. 190 * </dd> 191 * <dt> 192 * <code>path="<i>path</i>"</code> 193 * </dt> 194 * <dd> 195 * The subdirectory you're sharing. While the <code>name</code> attribute is a URI path 196 * segment, the <code>path</code> value is an actual subdirectory name. Notice that the 197 * value refers to a <b>subdirectory</b>, not an individual file or files. You can't 198 * share a single file by its file name, nor can you specify a subset of files using 199 * wildcards. 200 * </dd> 201 * </dl> 202 * <p> 203 * You must specify a child element of <code><paths></code> for each directory that contains 204 * files for which you want content URIs. For example, these XML elements specify two directories: 205 * <pre class="prettyprint"> 206 *<paths xmlns:android="http://schemas.android.com/apk/res/android"> 207 * <files-path name="my_images" path="images/"/> 208 * <files-path name="my_docs" path="docs/"/> 209 *</paths> 210 *</pre> 211 * <p> 212 * Put the <code><paths></code> element and its children in an XML file in your project. 213 * For example, you can add them to a new file called <code>res/xml/file_paths.xml</code>. 214 * To link this file to the FileProvider, add a 215 * <a href="{@docRoot}guide/topics/manifest/meta-data-element.html"><meta-data></a> element 216 * as a child of the <code><provider></code> element that defines the FileProvider. Set the 217 * <code><meta-data></code> element's "android:name" attribute to 218 * <code>android.support.FILE_PROVIDER_PATHS</code>. Set the element's "android:resource" attribute 219 * to <code>@xml/file_paths</code> (notice that you don't specify the <code>.xml</code> 220 * extension). For example: 221 * <pre class="prettyprint"> 222 *<provider 223 * android:name="android.support.v4.content.FileProvider" 224 * android:authorities="com.mydomain.fileprovider" 225 * android:exported="false" 226 * android:grantUriPermissions="true"> 227 * <meta-data 228 * android:name="android.support.FILE_PROVIDER_PATHS" 229 * android:resource="@xml/file_paths" /> 230 *</provider> 231 *</pre> 232 * <h3 id="GetUri">Generating the Content URI for a File</h3> 233 * <p> 234 * To share a file with another app using a content URI, your app has to generate the content URI. 235 * To generate the content URI, create a new {@link File} for the file, then pass the {@link File} 236 * to {@link #getUriForFile(Context, String, File) getUriForFile()}. You can send the content URI 237 * returned by {@link #getUriForFile(Context, String, File) getUriForFile()} to another app in an 238 * {@link android.content.Intent}. The client app that receives the content URI can open the file 239 * and access its contents by calling 240 * {@link android.content.ContentResolver#openFileDescriptor(Uri, String) 241 * ContentResolver.openFileDescriptor} to get a {@link ParcelFileDescriptor}. 242 * <p> 243 * For example, suppose your app is offering files to other apps with a FileProvider that has the 244 * authority <code>com.mydomain.fileprovider</code>. To get a content URI for the file 245 * <code>default_image.jpg</code> in the <code>images/</code> subdirectory of your internal storage 246 * add the following code: 247 * <pre class="prettyprint"> 248 *File imagePath = new File(Context.getFilesDir(), "images"); 249 *File newFile = new File(imagePath, "default_image.jpg"); 250 *Uri contentUri = getUriForFile(getContext(), "com.mydomain.fileprovider", newFile); 251 *</pre> 252 * As a result of the previous snippet, 253 * {@link #getUriForFile(Context, String, File) getUriForFile()} returns the content URI 254 * <code>content://com.mydomain.fileprovider/my_images/default_image.jpg</code>. 255 * <h3 id="Permissions">Granting Temporary Permissions to a URI</h3> 256 * To grant an access permission to a content URI returned from 257 * {@link #getUriForFile(Context, String, File) getUriForFile()}, do one of the following: 258 * <ul> 259 * <li> 260 * Call the method 261 * {@link Context#grantUriPermission(String, Uri, int) 262 * Context.grantUriPermission(package, Uri, mode_flags)} for the <code>content://</code> 263 * {@link Uri}, using the desired mode flags. This grants temporary access permission for the 264 * content URI to the specified package, according to the value of the 265 * the <code>mode_flags</code> parameter, which you can set to 266 * {@link Intent#FLAG_GRANT_READ_URI_PERMISSION}, {@link Intent#FLAG_GRANT_WRITE_URI_PERMISSION} 267 * or both. The permission remains in effect until you revoke it by calling 268 * {@link Context#revokeUriPermission(Uri, int) revokeUriPermission()} or until the device 269 * reboots. 270 * </li> 271 * <li> 272 * Put the content URI in an {@link Intent} by calling {@link Intent#setData(Uri) setData()}. 273 * </li> 274 * <li> 275 * Next, call the method {@link Intent#setFlags(int) Intent.setFlags()} with either 276 * {@link Intent#FLAG_GRANT_READ_URI_PERMISSION} or 277 * {@link Intent#FLAG_GRANT_WRITE_URI_PERMISSION} or both. 278 * </li> 279 * <li> 280 * Finally, send the {@link Intent} to 281 * another app. Most often, you do this by calling 282 * {@link android.app.Activity#setResult(int, android.content.Intent) setResult()}. 283 * <p> 284 * Permissions granted in an {@link Intent} remain in effect while the stack of the receiving 285 * {@link android.app.Activity} is active. When the stack finishes, the permissions are 286 * automatically removed. Permissions granted to one {@link android.app.Activity} in a client 287 * app are automatically extended to other components of that app. 288 * </p> 289 * </li> 290 * </ul> 291 * <h3 id="ServeUri">Serving a Content URI to Another App</h3> 292 * <p> 293 * There are a variety of ways to serve the content URI for a file to a client app. One common way 294 * is for the client app to start your app by calling 295 * {@link android.app.Activity#startActivityForResult(Intent, int, Bundle) startActivityResult()}, 296 * which sends an {@link Intent} to your app to start an {@link android.app.Activity} in your app. 297 * In response, your app can immediately return a content URI to the client app or present a user 298 * interface that allows the user to pick a file. In the latter case, once the user picks the file 299 * your app can return its content URI. In both cases, your app returns the content URI in an 300 * {@link Intent} sent via {@link android.app.Activity#setResult(int, Intent) setResult()}. 301 * </p> 302 * <p> 303 * You can also put the content URI in a {@link android.content.ClipData} object and then add the 304 * object to an {@link Intent} you send to a client app. To do this, call 305 * {@link Intent#setClipData(ClipData) Intent.setClipData()}. When you use this approach, you can 306 * add multiple {@link android.content.ClipData} objects to the {@link Intent}, each with its own 307 * content URI. When you call {@link Intent#setFlags(int) Intent.setFlags()} on the {@link Intent} 308 * to set temporary access permissions, the same permissions are applied to all of the content 309 * URIs. 310 * </p> 311 * <p class="note"> 312 * <strong>Note:</strong> The {@link Intent#setClipData(ClipData) Intent.setClipData()} method is 313 * only available in platform version 16 (Android 4.1) and later. If you want to maintain 314 * compatibility with previous versions, you should send one content URI at a time in the 315 * {@link Intent}. Set the action to {@link Intent#ACTION_SEND} and put the URI in data by calling 316 * {@link Intent#setData setData()}. 317 * </p> 318 * <h3 id="">More Information</h3> 319 * <p> 320 * To learn more about FileProvider, see the Android training class 321 * <a href="{@docRoot}training/secure-file-sharing/index.html">Sharing Files Securely with URIs</a>. 322 * </p> 323 */ 324public class FileProvider extends ContentProvider { 325 private static final String[] COLUMNS = { 326 OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE }; 327 328 private static final String 329 META_DATA_FILE_PROVIDER_PATHS = "android.support.FILE_PROVIDER_PATHS"; 330 331 private static final String TAG_ROOT_PATH = "root-path"; 332 private static final String TAG_FILES_PATH = "files-path"; 333 private static final String TAG_CACHE_PATH = "cache-path"; 334 private static final String TAG_EXTERNAL = "external-path"; 335 private static final String TAG_EXTERNAL_FILES = "external-files-path"; 336 private static final String TAG_EXTERNAL_CACHE = "external-cache-path"; 337 338 private static final String ATTR_NAME = "name"; 339 private static final String ATTR_PATH = "path"; 340 341 private static final File DEVICE_ROOT = new File("/"); 342 343 @GuardedBy("sCache") 344 private static HashMap<String, PathStrategy> sCache = new HashMap<String, PathStrategy>(); 345 346 private PathStrategy mStrategy; 347 348 /** 349 * The default FileProvider implementation does not need to be initialized. If you want to 350 * override this method, you must provide your own subclass of FileProvider. 351 */ 352 @Override 353 public boolean onCreate() { 354 return true; 355 } 356 357 /** 358 * After the FileProvider is instantiated, this method is called to provide the system with 359 * information about the provider. 360 * 361 * @param context A {@link Context} for the current component. 362 * @param info A {@link ProviderInfo} for the new provider. 363 */ 364 @Override 365 public void attachInfo(Context context, ProviderInfo info) { 366 super.attachInfo(context, info); 367 368 // Sanity check our security 369 if (info.exported) { 370 throw new SecurityException("Provider must not be exported"); 371 } 372 if (!info.grantUriPermissions) { 373 throw new SecurityException("Provider must grant uri permissions"); 374 } 375 376 mStrategy = getPathStrategy(context, info.authority); 377 } 378 379 /** 380 * Return a content URI for a given {@link File}. Specific temporary 381 * permissions for the content URI can be set with 382 * {@link Context#grantUriPermission(String, Uri, int)}, or added 383 * to an {@link Intent} by calling {@link Intent#setData(Uri) setData()} and then 384 * {@link Intent#setFlags(int) setFlags()}; in both cases, the applicable flags are 385 * {@link Intent#FLAG_GRANT_READ_URI_PERMISSION} and 386 * {@link Intent#FLAG_GRANT_WRITE_URI_PERMISSION}. A FileProvider can only return a 387 * <code>content</code> {@link Uri} for file paths defined in their <code><paths></code> 388 * meta-data element. See the Class Overview for more information. 389 * 390 * @param context A {@link Context} for the current component. 391 * @param authority The authority of a {@link FileProvider} defined in a 392 * {@code <provider>} element in your app's manifest. 393 * @param file A {@link File} pointing to the filename for which you want a 394 * <code>content</code> {@link Uri}. 395 * @return A content URI for the file. 396 * @throws IllegalArgumentException When the given {@link File} is outside 397 * the paths supported by the provider. 398 */ 399 public static Uri getUriForFile(Context context, String authority, File file) { 400 final PathStrategy strategy = getPathStrategy(context, authority); 401 return strategy.getUriForFile(file); 402 } 403 404 /** 405 * Use a content URI returned by 406 * {@link #getUriForFile(Context, String, File) getUriForFile()} to get information about a file 407 * managed by the FileProvider. 408 * FileProvider reports the column names defined in {@link android.provider.OpenableColumns}: 409 * <ul> 410 * <li>{@link android.provider.OpenableColumns#DISPLAY_NAME}</li> 411 * <li>{@link android.provider.OpenableColumns#SIZE}</li> 412 * </ul> 413 * For more information, see 414 * {@link ContentProvider#query(Uri, String[], String, String[], String) 415 * ContentProvider.query()}. 416 * 417 * @param uri A content URI returned by {@link #getUriForFile}. 418 * @param projection The list of columns to put into the {@link Cursor}. If null all columns are 419 * included. 420 * @param selection Selection criteria to apply. If null then all data that matches the content 421 * URI is returned. 422 * @param selectionArgs An array of {@link java.lang.String}, containing arguments to bind to 423 * the <i>selection</i> parameter. The <i>query</i> method scans <i>selection</i> from left to 424 * right and iterates through <i>selectionArgs</i>, replacing the current "?" character in 425 * <i>selection</i> with the value at the current position in <i>selectionArgs</i>. The 426 * values are bound to <i>selection</i> as {@link java.lang.String} values. 427 * @param sortOrder A {@link java.lang.String} containing the column name(s) on which to sort 428 * the resulting {@link Cursor}. 429 * @return A {@link Cursor} containing the results of the query. 430 * 431 */ 432 @Override 433 public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, 434 String sortOrder) { 435 // ContentProvider has already checked granted permissions 436 final File file = mStrategy.getFileForUri(uri); 437 438 if (projection == null) { 439 projection = COLUMNS; 440 } 441 442 String[] cols = new String[projection.length]; 443 Object[] values = new Object[projection.length]; 444 int i = 0; 445 for (String col : projection) { 446 if (OpenableColumns.DISPLAY_NAME.equals(col)) { 447 cols[i] = OpenableColumns.DISPLAY_NAME; 448 values[i++] = file.getName(); 449 } else if (OpenableColumns.SIZE.equals(col)) { 450 cols[i] = OpenableColumns.SIZE; 451 values[i++] = file.length(); 452 } 453 } 454 455 cols = copyOf(cols, i); 456 values = copyOf(values, i); 457 458 final MatrixCursor cursor = new MatrixCursor(cols, 1); 459 cursor.addRow(values); 460 return cursor; 461 } 462 463 /** 464 * Returns the MIME type of a content URI returned by 465 * {@link #getUriForFile(Context, String, File) getUriForFile()}. 466 * 467 * @param uri A content URI returned by 468 * {@link #getUriForFile(Context, String, File) getUriForFile()}. 469 * @return If the associated file has an extension, the MIME type associated with that 470 * extension; otherwise <code>application/octet-stream</code>. 471 */ 472 @Override 473 public String getType(Uri uri) { 474 // ContentProvider has already checked granted permissions 475 final File file = mStrategy.getFileForUri(uri); 476 477 final int lastDot = file.getName().lastIndexOf('.'); 478 if (lastDot >= 0) { 479 final String extension = file.getName().substring(lastDot + 1); 480 final String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension); 481 if (mime != null) { 482 return mime; 483 } 484 } 485 486 return "application/octet-stream"; 487 } 488 489 /** 490 * By default, this method throws an {@link java.lang.UnsupportedOperationException}. You must 491 * subclass FileProvider if you want to provide different functionality. 492 */ 493 @Override 494 public Uri insert(Uri uri, ContentValues values) { 495 throw new UnsupportedOperationException("No external inserts"); 496 } 497 498 /** 499 * By default, this method throws an {@link java.lang.UnsupportedOperationException}. You must 500 * subclass FileProvider if you want to provide different functionality. 501 */ 502 @Override 503 public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { 504 throw new UnsupportedOperationException("No external updates"); 505 } 506 507 /** 508 * Deletes the file associated with the specified content URI, as 509 * returned by {@link #getUriForFile(Context, String, File) getUriForFile()}. Notice that this 510 * method does <b>not</b> throw an {@link java.io.IOException}; you must check its return value. 511 * 512 * @param uri A content URI for a file, as returned by 513 * {@link #getUriForFile(Context, String, File) getUriForFile()}. 514 * @param selection Ignored. Set to {@code null}. 515 * @param selectionArgs Ignored. Set to {@code null}. 516 * @return 1 if the delete succeeds; otherwise, 0. 517 */ 518 @Override 519 public int delete(Uri uri, String selection, String[] selectionArgs) { 520 // ContentProvider has already checked granted permissions 521 final File file = mStrategy.getFileForUri(uri); 522 return file.delete() ? 1 : 0; 523 } 524 525 /** 526 * By default, FileProvider automatically returns the 527 * {@link ParcelFileDescriptor} for a file associated with a <code>content://</code> 528 * {@link Uri}. To get the {@link ParcelFileDescriptor}, call 529 * {@link android.content.ContentResolver#openFileDescriptor(Uri, String) 530 * ContentResolver.openFileDescriptor}. 531 * 532 * To override this method, you must provide your own subclass of FileProvider. 533 * 534 * @param uri A content URI associated with a file, as returned by 535 * {@link #getUriForFile(Context, String, File) getUriForFile()}. 536 * @param mode Access mode for the file. May be "r" for read-only access, "rw" for read and 537 * write access, or "rwt" for read and write access that truncates any existing file. 538 * @return A new {@link ParcelFileDescriptor} with which you can access the file. 539 */ 540 @Override 541 public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException { 542 // ContentProvider has already checked granted permissions 543 final File file = mStrategy.getFileForUri(uri); 544 final int fileMode = modeToMode(mode); 545 return ParcelFileDescriptor.open(file, fileMode); 546 } 547 548 /** 549 * Return {@link PathStrategy} for given authority, either by parsing or 550 * returning from cache. 551 */ 552 private static PathStrategy getPathStrategy(Context context, String authority) { 553 PathStrategy strat; 554 synchronized (sCache) { 555 strat = sCache.get(authority); 556 if (strat == null) { 557 try { 558 strat = parsePathStrategy(context, authority); 559 } catch (IOException e) { 560 throw new IllegalArgumentException( 561 "Failed to parse " + META_DATA_FILE_PROVIDER_PATHS + " meta-data", e); 562 } catch (XmlPullParserException e) { 563 throw new IllegalArgumentException( 564 "Failed to parse " + META_DATA_FILE_PROVIDER_PATHS + " meta-data", e); 565 } 566 sCache.put(authority, strat); 567 } 568 } 569 return strat; 570 } 571 572 /** 573 * Parse and return {@link PathStrategy} for given authority as defined in 574 * {@link #META_DATA_FILE_PROVIDER_PATHS} {@code <meta-data>}. 575 * 576 * @see #getPathStrategy(Context, String) 577 */ 578 private static PathStrategy parsePathStrategy(Context context, String authority) 579 throws IOException, XmlPullParserException { 580 final SimplePathStrategy strat = new SimplePathStrategy(authority); 581 582 final ProviderInfo info = context.getPackageManager() 583 .resolveContentProvider(authority, PackageManager.GET_META_DATA); 584 final XmlResourceParser in = info.loadXmlMetaData( 585 context.getPackageManager(), META_DATA_FILE_PROVIDER_PATHS); 586 if (in == null) { 587 throw new IllegalArgumentException( 588 "Missing " + META_DATA_FILE_PROVIDER_PATHS + " meta-data"); 589 } 590 591 int type; 592 while ((type = in.next()) != END_DOCUMENT) { 593 if (type == START_TAG) { 594 final String tag = in.getName(); 595 596 final String name = in.getAttributeValue(null, ATTR_NAME); 597 String path = in.getAttributeValue(null, ATTR_PATH); 598 599 File target = null; 600 if (TAG_ROOT_PATH.equals(tag)) { 601 target = DEVICE_ROOT; 602 } else if (TAG_FILES_PATH.equals(tag)) { 603 target = context.getFilesDir(); 604 } else if (TAG_CACHE_PATH.equals(tag)) { 605 target = context.getCacheDir(); 606 } else if (TAG_EXTERNAL.equals(tag)) { 607 target = Environment.getExternalStorageDirectory(); 608 } else if (TAG_EXTERNAL_FILES.equals(tag)) { 609 File[] externalFilesDirs = ContextCompat.getExternalFilesDirs(context, null); 610 if (externalFilesDirs.length > 0) { 611 target = externalFilesDirs[0]; 612 } 613 } else if (TAG_EXTERNAL_CACHE.equals(tag)) { 614 File[] externalCacheDirs = ContextCompat.getExternalCacheDirs(context); 615 if (externalCacheDirs.length > 0) { 616 target = externalCacheDirs[0]; 617 } 618 } 619 620 if (target != null) { 621 strat.addRoot(name, buildPath(target, path)); 622 } 623 } 624 } 625 626 return strat; 627 } 628 629 /** 630 * Strategy for mapping between {@link File} and {@link Uri}. 631 * <p> 632 * Strategies must be symmetric so that mapping a {@link File} to a 633 * {@link Uri} and then back to a {@link File} points at the original 634 * target. 635 * <p> 636 * Strategies must remain consistent across app launches, and not rely on 637 * dynamic state. This ensures that any generated {@link Uri} can still be 638 * resolved if your process is killed and later restarted. 639 * 640 * @see SimplePathStrategy 641 */ 642 interface PathStrategy { 643 /** 644 * Return a {@link Uri} that represents the given {@link File}. 645 */ 646 public Uri getUriForFile(File file); 647 648 /** 649 * Return a {@link File} that represents the given {@link Uri}. 650 */ 651 public File getFileForUri(Uri uri); 652 } 653 654 /** 655 * Strategy that provides access to files living under a narrow whitelist of 656 * filesystem roots. It will throw {@link SecurityException} if callers try 657 * accessing files outside the configured roots. 658 * <p> 659 * For example, if configured with 660 * {@code addRoot("myfiles", context.getFilesDir())}, then 661 * {@code context.getFileStreamPath("foo.txt")} would map to 662 * {@code content://myauthority/myfiles/foo.txt}. 663 */ 664 static class SimplePathStrategy implements PathStrategy { 665 private final String mAuthority; 666 private final HashMap<String, File> mRoots = new HashMap<String, File>(); 667 668 public SimplePathStrategy(String authority) { 669 mAuthority = authority; 670 } 671 672 /** 673 * Add a mapping from a name to a filesystem root. The provider only offers 674 * access to files that live under configured roots. 675 */ 676 public void addRoot(String name, File root) { 677 if (TextUtils.isEmpty(name)) { 678 throw new IllegalArgumentException("Name must not be empty"); 679 } 680 681 try { 682 // Resolve to canonical path to keep path checking fast 683 root = root.getCanonicalFile(); 684 } catch (IOException e) { 685 throw new IllegalArgumentException( 686 "Failed to resolve canonical path for " + root, e); 687 } 688 689 mRoots.put(name, root); 690 } 691 692 @Override 693 public Uri getUriForFile(File file) { 694 String path; 695 try { 696 path = file.getCanonicalPath(); 697 } catch (IOException e) { 698 throw new IllegalArgumentException("Failed to resolve canonical path for " + file); 699 } 700 701 // Find the most-specific root path 702 Map.Entry<String, File> mostSpecific = null; 703 for (Map.Entry<String, File> root : mRoots.entrySet()) { 704 final String rootPath = root.getValue().getPath(); 705 if (path.startsWith(rootPath) && (mostSpecific == null 706 || rootPath.length() > mostSpecific.getValue().getPath().length())) { 707 mostSpecific = root; 708 } 709 } 710 711 if (mostSpecific == null) { 712 throw new IllegalArgumentException( 713 "Failed to find configured root that contains " + path); 714 } 715 716 // Start at first char of path under root 717 final String rootPath = mostSpecific.getValue().getPath(); 718 if (rootPath.endsWith("/")) { 719 path = path.substring(rootPath.length()); 720 } else { 721 path = path.substring(rootPath.length() + 1); 722 } 723 724 // Encode the tag and path separately 725 path = Uri.encode(mostSpecific.getKey()) + '/' + Uri.encode(path, "/"); 726 return new Uri.Builder().scheme("content") 727 .authority(mAuthority).encodedPath(path).build(); 728 } 729 730 @Override 731 public File getFileForUri(Uri uri) { 732 String path = uri.getEncodedPath(); 733 734 final int splitIndex = path.indexOf('/', 1); 735 final String tag = Uri.decode(path.substring(1, splitIndex)); 736 path = Uri.decode(path.substring(splitIndex + 1)); 737 738 final File root = mRoots.get(tag); 739 if (root == null) { 740 throw new IllegalArgumentException("Unable to find configured root for " + uri); 741 } 742 743 File file = new File(root, path); 744 try { 745 file = file.getCanonicalFile(); 746 } catch (IOException e) { 747 throw new IllegalArgumentException("Failed to resolve canonical path for " + file); 748 } 749 750 if (!file.getPath().startsWith(root.getPath())) { 751 throw new SecurityException("Resolved path jumped beyond configured root"); 752 } 753 754 return file; 755 } 756 } 757 758 /** 759 * Copied from ContentResolver.java 760 */ 761 private static int modeToMode(String mode) { 762 int modeBits; 763 if ("r".equals(mode)) { 764 modeBits = ParcelFileDescriptor.MODE_READ_ONLY; 765 } else if ("w".equals(mode) || "wt".equals(mode)) { 766 modeBits = ParcelFileDescriptor.MODE_WRITE_ONLY 767 | ParcelFileDescriptor.MODE_CREATE 768 | ParcelFileDescriptor.MODE_TRUNCATE; 769 } else if ("wa".equals(mode)) { 770 modeBits = ParcelFileDescriptor.MODE_WRITE_ONLY 771 | ParcelFileDescriptor.MODE_CREATE 772 | ParcelFileDescriptor.MODE_APPEND; 773 } else if ("rw".equals(mode)) { 774 modeBits = ParcelFileDescriptor.MODE_READ_WRITE 775 | ParcelFileDescriptor.MODE_CREATE; 776 } else if ("rwt".equals(mode)) { 777 modeBits = ParcelFileDescriptor.MODE_READ_WRITE 778 | ParcelFileDescriptor.MODE_CREATE 779 | ParcelFileDescriptor.MODE_TRUNCATE; 780 } else { 781 throw new IllegalArgumentException("Invalid mode: " + mode); 782 } 783 return modeBits; 784 } 785 786 private static File buildPath(File base, String... segments) { 787 File cur = base; 788 for (String segment : segments) { 789 if (segment != null) { 790 cur = new File(cur, segment); 791 } 792 } 793 return cur; 794 } 795 796 private static String[] copyOf(String[] original, int newLength) { 797 final String[] result = new String[newLength]; 798 System.arraycopy(original, 0, result, 0, newLength); 799 return result; 800 } 801 802 private static Object[] copyOf(Object[] original, int newLength) { 803 final Object[] result = new Object[newLength]; 804 System.arraycopy(original, 0, result, 0, newLength); 805 return result; 806 } 807} 808