tree 3f91b4825e402debfbd51064fb5e2e6b381e9e46
parent 259d98b1dd7946078d4d8c7cbcf6c8dd4159cdca
author Zim <zezeozue@google.com> 1591009495 +0100
committer Zim <zezeozue@google.com> 1591040032 +0100

Support apps sharing file:// URIs with the camera API

The camera API, MediaStore.ACTION_IMAGE_CAPTURE requires apps to pass
a content:// URI with write permissions to the camera. Unfortunately,
apps haven't been doing this and we only started hitting problems in R
for two reasons:
1. The FileUriExposedException that should crash apps when they try to
share file:// URIs acroos binder is skipped. This is because, the
image_capture intent is passed across binder as a field in a
ChooserActivity Intent and the child intents are not checked for
file URI exposed
2. Prior to R, when camera gets a file:// URI, camera issues a file
open(2) in its process. This open(2) succeeds because the camera had
write_external_storage permission which gave it write access to all
files on external storage

Now, camera targets R and (2) fails because camera does not have write
access to files owned by other apps. To workaround, we do the
following in the apps process when it targets < R:
a. When we detect a file:// URI for the camera in an Intent, we create
the file on disk if it is not already created.
b. Scan the file to insert it in the database and retrieve a
content:// URI
c. Replace the file:// URI with the content URI in the image_capture
intent

This works because, the system will ensure the camera is granted write
access to the content URI.

Test: Manual
Bug: 156336269
Change-Id: I4849ff5e806a8207650ff7534846c36ecdc6d3c0