Android - file provider - permission denial

Question

I have two apps : app1 and app2.

App2 has :

<provider
        android:name="android.support.v4.content.FileProvider"
        android:authorities="com.android.provider.ImageSharing"
        android:exported="false"
        android:grantUriPermissions="true" >
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/paths" />
</provider>

paths.xml :

<paths>

     <files-path name="my_images" path="images/"/>

</paths>

App2 receives request in its Activity from App1 to get URI for an image. The App2 Activity does the following once URI is decided :

Intent intent = new Intent();

intent.setDataAndType(contentUri, getContentResolver().getType(contentUri));

int uid = Binder.getCallingUid();
String callingPackage = getPackageManager().getNameForUid(uid);

getApplicationContext().grantUriPermission(callingPackage, contentUri,
                    Intent.FLAG_GRANT_READ_URI_PERMISSION);

setResult(Activity.RESULT_OK, intent);
finish();

On receiving the result back from App2, App1 does the following :

Uri imageUri = data.getData();
if(imageUri != null) {
    ImageView iv = (ImageView) layoutView.findViewById(R.id.imageReceived);
    iv.setImageURI(imageUri);
}

In App1, on returning from App2, I get the following exception :

java.lang.SecurityException: Permission Denial: opening provider android.support.v4.content.FileProvider from ProcessRecord{52a99eb0 3493:com.android.App1.app/u0a57} (pid=3493, uid=10057) that is not exported from uid 10058

What am I doing wrong ?

Answer 1

Turns out the only way to solve this is to grant permissions to all of the packages that might need it, like this:

List<ResolveInfo> resInfoList = context.getPackageManager().queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
for (ResolveInfo resolveInfo : resInfoList) {
    String packageName = resolveInfo.activityInfo.packageName;
    context.grantUriPermission(packageName, uri, Intent.FLAG_GRANT_WRITE_URI_PERMISSION | Intent.FLAG_GRANT_READ_URI_PERMISSION);
}