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Document restricted app private file permissions

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Make the docs reflect changes in private file access permissions.

Starting with API level 24 app private files are exclusively accessible
to the owning app. Files can no longer be shared by name because apps
cannot relax the files system permissions.

Bug: 27636012
Change-Id: I0139b82547c6f6bede2503aa06b5d2a34cad5a49
This commit is contained in:
Janis Danisevskis
2016-03-22 11:04:55 +00:00
parent 0bee3d2997
commit 67688789fe
1 changed files with 50 additions and 1 deletions
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51
docs/html/preview/behavior-changes.jd
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@@ -18,7 +18,11 @@ page.image=images/cards/card-n-changes_2x.png
<li><a href="#bg-opt">Background Optimizations</a></li>
</ol>
</li>
<li><a href="#perm">Permissions Changes</a></li>
<li><a href="#perm">Permissions Changes</a>
<ol>
<li><a href="#permfilesys">File System Permission Changes</a></li>
</ol>
</li>
<li><a href="#accessibility">Accessibility Improvements</a>
<ol>
<li><a href="#screen-zoom">Screen Zoom</a></li>
@@ -200,7 +204,52 @@ page.image=images/cards/card-n-changes_2x.png
</ul>
<h3 id="permfilesys">File system permission changes</h3>
<p>
In order to improve the security of private files, the private directory of
apps targeting Android N or higher has restricted access (0700). This prevents
leakage of metadata of private files, such as their size or existence. This
has multiple side effects:
</p>
<ul>
<li>
Private files’ file permissions can no longer be relaxed by the owner, and
an attempt to do so using
{@link android.content.Context#MODE_WORLD_READABLE} and/or
{@link android.content.Context#MODE_WORLD_WRITEABLE}, will trigger a
{@link java.lang.SecurityException}.
</li>
<li>
Passing <code>file://</code> URIs outside the package domain may leave the
receiver with an unaccessible path. Therefore, attempts to pass a
<code>file://</code> URI trigger a
<code>FileUriExposedException</code>. The recommended way to share the
content of a private file is using the {@link
android.support.v4.content.FileProvider}.
</li>
<li>
The {@link android.app.DownloadManager} can no longer share privately
stored files by filename. Legacy applications may end up with an
unaccessible path when accessing {@link
android.app.DownloadManager#COLUMN_LOCAL_FILENAME}. Apps targeting
Android N or higher trigger a {@link java.lang.SecurityException} when
attempting to access
{@link android.app.DownloadManager#COLUMN_LOCAL_FILENAME}.
Legacy applications that set the download location to a public location by
using
{@link
android.app.DownloadManager.Request#setDestinationInExternalFilesDir} or
{@link
android.app.DownloadManager.Request#setDestinationInExternalPublicDir}
can still access the path in
{@link android.app.DownloadManager#COLUMN_LOCAL_FILENAME}, however, this
method is strongly discouraged. The preferred way of accessing a file
exposed by the {@link android.app.DownloadManager} is using
{@link android.content.ContentResolver#openFileDescriptor}.
</li>
</ul>
<h2 id="accessibility">Accessibility Improvements</h2>