Add a token the filename for exported user data

Also redirect to it for download, for Amazon S3
compatibility.

Prior to this patch an attacker could obtain an
users export by guessing the filename with a high
chance of success. Fully authenticating the
download request is a lot harder due to our diverse
deployment scenarios.

This brings the used method in line with the photo
export feature.

Thanks to @tomekr for the report.

app/controllers/users_controller.rb

@@ -140,7 +140,7 @@ class UsersController < ApplicationController
   end
 
   def download_profile
-    send_data File.open(current_user.export.path).read, type: :json, filename: current_user.export.filename
+    redirect_to current_user.export.url
   end
 
   def export_photos

app/uploaders/exported_photos.rb

@@ -2,7 +2,7 @@
 #   licensed under the Affero General Public License version 3 or later.  See
 #   the COPYRIGHT file.
 
-class ExportedPhotos < CarrierWave::Uploader::Base
+class ExportedPhotos < SecureUploader
 
   def store_dir
     "uploads/users"
@@ -12,10 +12,6 @@ class ExportedPhotos < CarrierWave::Uploader::Base
     "#{model.username}_photos_#{secure_token}.zip" if original_filename.present?
   end
 
-  protected
-  def secure_token(bytes = 16)
-    var = :"@#{mounted_as}_secure_token"
-    model.instance_variable_get(var) or model.instance_variable_set(var, SecureRandom.urlsafe_base64(bytes))
-  end
+
 
 end

app/uploaders/exported_user.rb

@@ -2,7 +2,7 @@
 #   licensed under the Affero General Public License version 3 or later.  See
 #   the COPYRIGHT file.
 
-class ExportedUser < CarrierWave::Uploader::Base
+class ExportedUser < SecureUploader
 
   def store_dir
     "uploads/users"
@@ -13,7 +13,7 @@ class ExportedUser < CarrierWave::Uploader::Base
   end
 
   def filename
-    "#{model.username}_diaspora_data.json.gz"
+    "#{model.username}_diaspora_data_#{secure_token}.json.gz"
   end
 
 end

app/uploaders/secure_uploader.rb

@@ -0,0 +1,7 @@
+class SecureUploader < CarrierWave::Uploader::Base
+  protected
+  def secure_token(bytes = 16)
+    var = :"@#{mounted_as}_secure_token"
+    model.instance_variable_get(var) or model.instance_variable_set(var, SecureRandom.urlsafe_base64(bytes))
+  end
+end

spec/controllers/users_controller_spec.rb

@@ -24,8 +24,7 @@ describe UsersController, :type => :controller do
     it "downloads a user's export file" do
       @user.perform_export!
       get :download_profile
-      parsed = JSON.parse(ActiveSupport::Gzip.decompress(response.body))
-      expect(parsed['user']['username']).to eq @user.username
+      expect(response).to redirect_to(@user.export.url)
     end
   end
 
@@ -37,7 +36,7 @@ describe UsersController, :type => :controller do
       expect(response).to redirect_to(edit_user_path)
     end
   end
-  
+
   describe '#download_photos' do
     it "redirects to user's photos zip file"  do
       @user.perform_export_photos!
@@ -74,7 +73,7 @@ describe UsersController, :type => :controller do
       get :public, :username => @user.username, :format => :atom
       expect(response.body).to include('a href')
     end
-    
+
     it 'includes reshares in the atom feed' do
       reshare = FactoryGirl.create(:reshare, :author => @user.person)
       get :public, :username => @user.username, :format => :atom