allow install history to be read from an ContentProvider

This allows a designated app to read the install history from F-Droid via a
ContentProvider.  The app is designated by the packageName defined in the
string install_history_reader_packageName.

app/src/main/AndroidManifest.xml

@@ -109,6 +109,15 @@
                 android:name="android.support.FILE_PROVIDER_PATHS"
                 android:resource="@xml/apk_file_provider" />
         </provider>
+        <provider
+            android:name="android.support.v4.content.FileProvider"
+            android:authorities="org.fdroid.fdroid.installer"
+            android:exported="false"
+            android:grantUriPermissions="true">
+            <meta-data
+                android:name="android.support.FILE_PROVIDER_PATHS"
+                android:resource="@xml/install_history_file_provider" />
+        </provider>
 
         <meta-data
             android:name="android.app.default_searchable"

app/src/main/java/org/fdroid/fdroid/FDroidApp.java

@@ -303,6 +303,17 @@ public class FDroidApp extends Application {
 
         // TODO enable this based on a preference
         InstallHistoryService.register(this);
+
+        String packageName = getString(R.string.install_history_reader_packageName);
+        String unset = getString(R.string.install_history_reader_packageName_UNSET);
+        if (!TextUtils.equals(packageName, unset)) {
+            int modeFlags = Intent.FLAG_GRANT_READ_URI_PERMISSION
+                    | Intent.FLAG_GRANT_WRITE_URI_PERMISSION;
+            if (Build.VERSION.SDK_INT >= 19) {
+                modeFlags |= Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION;
+            }
+            grantUriPermission(packageName, InstallHistoryService.LOG_URI, modeFlags);
+        }
     }
 
     @TargetApi(18)

app/src/main/java/org/fdroid/fdroid/installer/InstallHistoryService.java

@@ -24,11 +24,11 @@ import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.net.Uri;
 import android.os.Process;
 import android.support.v4.content.LocalBroadcastManager;
 import android.text.TextUtils;
 
-import org.fdroid.fdroid.R;
 import org.fdroid.fdroid.Utils;
 import org.fdroid.fdroid.data.Apk;
 
@@ -47,6 +47,8 @@ import java.util.List;
 public class InstallHistoryService extends IntentService {
     public static final String TAG = "InstallHistoryService";
 
+    public static final Uri LOG_URI = Uri.parse("content://org.fdroid.fdroid.installer/install_history/all");
+
     private static BroadcastReceiver broadcastReceiver;
 
     public static void register(Context context) {
@@ -107,7 +109,9 @@ public class InstallHistoryService extends IntentService {
         values.add(String.valueOf(versionCode));
         values.add(intent.getAction());
 
-        File logFile = new File(getFilesDir(), getString(R.string.install_history_log_file));
+        File installHistoryDir = new File(getCacheDir(), "install_history");
+        installHistoryDir.mkdir();
+        File logFile = new File(installHistoryDir, "all");
         FileWriter fw = null;
         PrintWriter out = null;
         try {

app/src/main/res/values/donottranslate.xml

@@ -15,7 +15,10 @@
 
     <string name="app_details_subject">%1$s on F-Droid</string>
 
-    <string name="install_history_log_file">all</string>
+    <!-- The unset value is set to a string that is impossible to be a valid Java package name. This
+     prevents abuse by creating malware with the same packageName as the unset string. -->
+    <string name="install_history_reader_packageName_UNSET">1-THIS MEANS NO APP IS GRANTED ACCESS!</string>
+    <string name="install_history_reader_packageName">@string/install_history_reader_packageName_UNSET</string>
 
     <string-array name="updateIntervalValues">
         <item>0</item>

app/src/main/res/xml/install_history_file_provider.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<paths>
+    <cache-path
+        name="install_history"
+        path="install_history" />
+</paths>