handle dangerous extensions

app/controllers/api/active_storage_blobs_proxy_controller.rb

@@ -11,6 +11,7 @@ module Api
     before_action :set_noindex_headers
     before_action :set_security_headers
 
+    # rubocop:disable Metrics
     def show
       blob_uuid, purp, exp = ApplicationRecord.signed_id_verifier.verified(params[:signed_uuid])
 
@@ -22,6 +23,12 @@ module Api
 
       blob = ActiveStorage::Blob.find_by!(uuid: blob_uuid)
 
+      if Submitters::DANGEROUS_EXTENSIONS.include?(blob.filename.extension.to_s.downcase)
+        Rollbar.error('Dangerous extension') if defined?(Rollbar)
+
+        return head :unprocessable_content
+      end
+
       attachment = blob.attachments.take
 
       @record = attachment.record
@@ -46,6 +53,7 @@ module Api
         end
       end
     end
+    # rubocop:enable Metrics
 
     private
 

app/controllers/api/active_storage_blobs_proxy_legacy_controller.rb

@@ -19,6 +19,12 @@ module Api
 
       return head :not_found unless blob
 
+      if Submitters::DANGEROUS_EXTENSIONS.include?(blob.filename.extension.to_s.downcase)
+        Rollbar.error('Dangerous extension') if defined?(Rollbar)
+
+        return head :unprocessable_content
+      end
+
       is_permitted = blob.attachments.any? do |a|
         (current_user && a.record.account.id == current_user.account_id) ||
           a.record.account.account_configs.any? { |e| e.key == 'legacy_blob_proxy' } ||

app/controllers/user_initials_controller.rb

@@ -11,6 +11,12 @@ class UserInitialsController < ApplicationController
 
     return redirect_to settings_profile_index_path, notice: I18n.t('unable_to_save_initials') if file.blank?
 
+    extension = File.extname(file.original_filename).delete_prefix('.').downcase
+
+    if Submitters::DANGEROUS_EXTENSIONS.include?(extension)
+      raise Submitters::MaliciousFileExtension, "File type '.#{extension}' is not allowed."
+    end
+
     blob = ActiveStorage::Blob.create_and_upload!(io: file.open,
                                                   filename: file.original_filename,
                                                   content_type: file.content_type)

app/controllers/user_signatures_controller.rb

@@ -11,6 +11,12 @@ class UserSignaturesController < ApplicationController
 
     return redirect_to settings_profile_index_path, notice: I18n.t('unable_to_save_signature') if file.blank?
 
+    extension = File.extname(file.original_filename).delete_prefix('.').downcase
+
+    if Submitters::DANGEROUS_EXTENSIONS.include?(extension)
+      raise Submitters::MaliciousFileExtension, "File type '.#{extension}' is not allowed."
+    end
+
     blob = ActiveStorage::Blob.create_and_upload!(io: file.open,
                                                   filename: file.original_filename,
                                                   content_type: file.content_type)