From 6da648227ef59e5c77dc9d2c89a39eb5496a153e Mon Sep 17 00:00:00 2001
From: Eugen Rochko <eugen@zeonfederated.com>
Date: Sun, 1 May 2022 00:37:46 +0200
Subject: [PATCH] Fix error caused by missing subject in Webfinger response
 (#18204)

---
 app/lib/webfinger.rb | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/app/lib/webfinger.rb b/app/lib/webfinger.rb
index 1ffb5b4bf3..a681e0815f 100644
--- a/app/lib/webfinger.rb
+++ b/app/lib/webfinger.rb
@@ -6,8 +6,13 @@ class Webfinger
   class RedirectError < StandardError; end
 
   class Response
-    def initialize(body)
+    attr_reader :uri
+
+    def initialize(uri, body)
+      @uri  = uri
       @json = Oj.load(body, mode: :strict)
+
+      validate_response!
     end
 
     def subject
@@ -23,6 +28,10 @@ class Webfinger
     def links
       @links ||= @json['links'].index_by { |link| link['rel'] }
     end
+
+    def validate_response!
+      raise Webfinger::Error, "Missing subject in response for #{@uri}" if subject.blank?
+    end
   end
 
   def initialize(uri)
@@ -34,7 +43,7 @@ class Webfinger
   end
 
   def perform
-    Response.new(body_from_webfinger)
+    Response.new(@uri, body_from_webfinger)
   rescue Oj::ParseError
     raise Webfinger::Error, "Invalid JSON in response for #{@uri}"
   rescue Addressable::URI::InvalidURIError