Disable libvips unfuzzed operations (#226)

and add test coverage for (un)supported file types.

The avatar and logo variants move into the models and return nil for content
types that are no longer variable, so the controllers fall back to the initials
avatar and stock logo icon instead of raising `ActiveStorage::InvariableError`.

app/controllers/accounts/logos_controller.rb

@@ -8,9 +8,8 @@ class Accounts::LogosController < ApplicationController
     if stale?(etag: Current.account)
       expires_in 5.minutes, public: true, stale_while_revalidate: 1.week
 
-      if Current.account&.logo&.attached?
-        logo = Current.account.logo.variant(logo_variant).processed
-        send_png_file ActiveStorage::Blob.service.path_for(logo.key)
+      if (logo_variant = Current.account&.logo_variant(logo_size))
+        send_png_file ActiveStorage::Blob.service.path_for(logo_variant.key)
       else
         send_stock_icon
       end
@@ -23,9 +22,6 @@ class Accounts::LogosController < ApplicationController
   end
 
   private
-    LARGE_SQUARE_PNG_VARIANT = { resize_to_limit: [ 512, 512 ], format: :png }
-    SMALL_SQUARE_PNG_VARIANT = { resize_to_limit: [ 192, 192 ], format: :png }
-
     def send_png_file(path)
       send_file path, content_type: "image/png", disposition: :inline
     end
@@ -38,8 +34,8 @@ class Accounts::LogosController < ApplicationController
       end
     end
 
-    def logo_variant
-      small_logo? ? SMALL_SQUARE_PNG_VARIANT : LARGE_SQUARE_PNG_VARIANT
+    def logo_size
+      small_logo? ? :small : :large
     end
 
     def small_logo?

app/controllers/users/avatars_controller.rb

@@ -9,8 +9,7 @@ class Users::AvatarsController < ApplicationController
     if stale?(etag: @user)
       expires_in 30.minutes, public: true, stale_while_revalidate: 1.week
 
-      if @user.avatar.attached?
-        avatar_variant = @user.avatar.variant(SQUARE_WEBP_VARIANT).processed
+      if (avatar_variant = @user.avatar_variant)
         send_webp_blob_file avatar_variant.key
       elsif @user.bot?
         render_default_bot
@@ -26,8 +25,6 @@ class Users::AvatarsController < ApplicationController
   end
 
   private
-    SQUARE_WEBP_VARIANT = { resize_to_limit: [ 512, 512 ], format: :webp }
-
     def send_webp_blob_file(key)
       send_file ActiveStorage::Blob.service.path_for(key), content_type: "image/webp", disposition: :inline
     end

app/models/account.rb

@@ -1,6 +1,14 @@
 class Account < ApplicationRecord
   include Joinable
 
-  has_one_attached :logo
+  has_one_attached :logo do |attachable|
+    attachable.variant :large, resize_to_limit: [ 512, 512 ], format: :png
+    attachable.variant :small, resize_to_limit: [ 192, 192 ], format: :png
+  end
+
   has_json :settings, restrict_room_creation_to_administrators: false
+
+  def logo_variant(size)
+    logo.variant(size).processed if logo.variable?
+  end
 end

app/models/user/avatar.rb

@@ -2,7 +2,9 @@ module User::Avatar
   extend ActiveSupport::Concern
 
   included do
-    has_one_attached :avatar
+    has_one_attached :avatar do |attachable|
+      attachable.variant :square, resize_to_limit: [ 512, 512 ], format: :webp
+    end
   end
 
   class_methods do
@@ -14,4 +16,8 @@ module User::Avatar
   def avatar_token
     signed_id(purpose: :avatar)
   end
+
+  def avatar_variant
+    avatar.variant(:square).processed if avatar.variable?
+  end
 end