Gab Social. All are welcome.

app/services/verify_link_service.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+class VerifyLinkService < BaseService
+  def call(field)
+    @link_back = ActivityPub::TagManager.instance.url_for(field.account)
+    @url       = field.value_for_verification
+
+    perform_request!
+
+    return unless link_back_present?
+
+    field.mark_verified!
+  rescue OpenSSL::SSL::SSLError, HTTP::Error, Addressable::URI::InvalidURIError, GabSocial::HostValidationError, GabSocial::LengthValidationError => e
+    Rails.logger.debug "Error fetching link #{@url}: #{e}"
+    nil
+  end
+
+  private
+
+  def perform_request!
+    @body = Request.new(:get, @url).add_headers('Accept' => 'text/html').perform do |res|
+      res.code != 200 ? nil : res.body_with_limit
+    end
+  end
+
+  def link_back_present?
+    return false if @body.blank?
+
+    links = Nokogiri::HTML(@body).xpath('//a[contains(concat(" ", normalize-space(@rel), " "), " me ")]|//link[contains(concat(" ", normalize-space(@rel), " "), " me ")]')
+
+    if links.any? { |link| link['href'] == @link_back }
+      true
+    elsif links.empty?
+      false
+    else
+      link_redirects_back?(links.first['href'])
+    end
+  end
+
+  def link_redirects_back?(test_url)
+    redirect_to_url = Request.new(:head, test_url, follow: false).perform do |res|
+      res.headers['Location']
+    end
+
+    redirect_to_url == @link_back
+  end
+end