Fix being able to spoof link verification (#20217)

- Change verification to happen in `default` queue
- Change verification worker to only be queued if there's something to do
- Add `link` tags from metadata fields to page header of profiles

app/models/account.rb

@@ -295,7 +295,7 @@ class Account < ApplicationRecord
 
   def fields
     (self[:fields] || []).map do |f|
-      Field.new(self, f)
+      Account::Field.new(self, f)
     rescue
       nil
     end.compact
@@ -401,48 +401,6 @@ class Account < ApplicationRecord
     requires_review? && !requested_review?
   end
 
-  class Field < ActiveModelSerializers::Model
-    attributes :name, :value, :verified_at, :account
-
-    def initialize(account, attributes)
-      @original_field = attributes
-      string_limit = account.local? ? 255 : 2047
-      super(
-        account:     account,
-        name:        attributes['name'].strip[0, string_limit],
-        value:       attributes['value'].strip[0, string_limit],
-        verified_at: attributes['verified_at']&.to_datetime,
-      )
-    end
-
-    def verified?
-      verified_at.present?
-    end
-
-    def value_for_verification
-      @value_for_verification ||= begin
-        if account.local?
-          value
-        else
-          ActionController::Base.helpers.strip_tags(value)
-        end
-      end
-    end
-
-    def verifiable?
-      value_for_verification.present? && value_for_verification.start_with?('http://', 'https://')
-    end
-
-    def mark_verified!
-      self.verified_at = Time.now.utc
-      @original_field['verified_at'] = verified_at
-    end
-
-    def to_h
-      { name: name, value: value, verified_at: verified_at }
-    end
-  end
-
   class << self
     DISALLOWED_TSQUERY_CHARACTERS = /['?\\:‘’]/.freeze
     TEXTSEARCH = "(setweight(to_tsvector('simple', accounts.display_name), 'A') || setweight(to_tsvector('simple', accounts.username), 'B') || setweight(to_tsvector('simple', coalesce(accounts.domain, '')), 'C'))"

app/models/account/field.rb

@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+class Account::Field < ActiveModelSerializers::Model
+  MAX_CHARACTERS_LOCAL  = 255
+  MAX_CHARACTERS_COMPAT = 2_047
+
+  attributes :name, :value, :verified_at, :account
+
+  def initialize(account, attributes)
+    # Keeping this as reference allows us to update the field on the account
+    # from methods in this class, so that changes can be saved.
+    @original_field = attributes
+    @account        = account
+
+    super(
+      name:        sanitize(attributes['name']),
+      value:       sanitize(attributes['value']),
+      verified_at: attributes['verified_at']&.to_datetime,
+    )
+  end
+
+  def verified?
+    verified_at.present?
+  end
+
+  def value_for_verification
+    @value_for_verification ||= begin
+      if account.local?
+        value
+      else
+        extract_url_from_html
+      end
+    end
+  end
+
+  def verifiable?
+    value_for_verification.present? && /\A#{FetchLinkCardService::URL_PATTERN}\z/.match?(value_for_verification)
+  end
+
+  def requires_verification?
+    !verified? && verifiable?
+  end
+
+  def mark_verified!
+    @original_field['verified_at'] = self.verified_at = Time.now.utc
+  end
+
+  def to_h
+    { name: name, value: value, verified_at: verified_at }
+  end
+
+  private
+
+  def sanitize(str)
+    str.strip[0, character_limit]
+  end
+
+  def character_limit
+    account.local? ? MAX_CHARACTERS_LOCAL : MAX_CHARACTERS_COMPAT
+  end
+
+  def extract_url_from_html
+    doc = Nokogiri::HTML(value).at_xpath('//body')
+
+    return if doc.children.size > 1
+
+    element = doc.children.first
+
+    return if element.name != 'a' || element['href'] != element.text
+
+    element['href']
+  end
+end

app/services/activitypub/process_account_service.rb

@@ -40,7 +40,7 @@ class ActivityPub::ProcessAccountService < BaseService
     unless @options[:only_key] || @account.suspended?
       check_featured_collection! if @account.featured_collection_url.present?
       check_featured_tags_collection! if @json['featuredTags'].present?
-      check_links! unless @account.fields.empty?
+      check_links! if @account.fields.any?(&:requires_verification?)
     end
 
     @account

app/services/update_account_service.rb

@@ -28,7 +28,7 @@ class UpdateAccountService < BaseService
   end
 
   def check_links(account)
-    VerifyAccountLinksWorker.perform_async(account.id)
+    VerifyAccountLinksWorker.perform_async(account.id) if account.fields.any?(&:requires_verification?)
   end
 
   def process_hashtags(account)

app/views/accounts/show.html.haml

@@ -8,6 +8,9 @@
   %link{ rel: 'alternate', type: 'application/rss+xml', href: @rss_url }/
   %link{ rel: 'alternate', type: 'application/activity+json', href: ActivityPub::TagManager.instance.uri_for(@account) }/
 
+  - @account.fields.select(&:verifiable?).each do |field|
+    %link{ rel: 'me', type: 'text/html', href: field.value }/
+
   = opengraph 'og:type', 'profile'
   = render 'og', account: @account, url: short_account_url(@account, only_path: false)
 

app/workers/verify_account_links_worker.rb

@@ -3,14 +3,13 @@
 class VerifyAccountLinksWorker
   include Sidekiq::Worker
 
-  sidekiq_options queue: 'pull', retry: false, lock: :until_executed
+  sidekiq_options queue: 'default', retry: false, lock: :until_executed
 
   def perform(account_id)
     account = Account.find(account_id)
 
     account.fields.each do |field|
-      next unless !field.verified? && field.verifiable?
-      VerifyLinkService.new.call(field)
+      VerifyLinkService.new.call(field) if field.requires_verification?
     end
 
     account.save! if account.changed?

spec/models/account/field_spec.rb

@@ -0,0 +1,130 @@
+require 'rails_helper'
+
+RSpec.describe Account::Field, type: :model do
+  describe '#verified?' do
+    let(:account) { double('Account', local?: true) }
+
+    subject { described_class.new(account, 'name' => 'Foo', 'value' => 'Bar', 'verified_at' => verified_at) }
+
+    context 'when verified_at is set' do
+      let(:verified_at) { Time.now.utc.iso8601 }
+
+      it 'returns true' do
+        expect(subject.verified?).to be true
+      end
+    end
+
+    context 'when verified_at is not set' do
+      let(:verified_at) { nil }
+
+      it 'returns false' do
+        expect(subject.verified?).to be false
+      end
+    end
+  end
+
+  describe '#mark_verified!' do
+    let(:account) { double('Account', local?: true) }
+    let(:original_hash) { { 'name' => 'Foo', 'value' => 'Bar' } }
+
+    subject { described_class.new(account, original_hash) }
+
+    before do
+      subject.mark_verified!
+    end
+
+    it 'updates verified_at' do
+      expect(subject.verified_at).to_not be_nil
+    end
+
+    it 'updates original hash' do
+      expect(original_hash['verified_at']).to_not be_nil
+    end
+  end
+
+  describe '#verifiable?' do
+    let(:account) { double('Account', local?: local) }
+
+    subject { described_class.new(account, 'name' => 'Foo', 'value' => value) }
+
+    context 'for local accounts' do
+      let(:local) { true }
+
+      context 'for a URL with misleading authentication' do
+        let(:value) { 'https://spacex.com                                                                                            @h.43z.one' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
+
+      context 'for a URL' do
+        let(:value) { 'https://example.com' }
+
+        it 'returns true' do
+          expect(subject.verifiable?).to be true
+        end
+      end
+
+      context 'for text that is not a URL' do
+        let(:value) { 'Hello world' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
+
+      context 'for text that contains a URL' do
+        let(:value) { 'Hello https://example.com world' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
+    end
+
+    context 'for remote accounts' do
+      let(:local) { false }
+
+      context 'for a link' do
+        let(:value) { '<a href="https://www.patreon.com/mastodon" target="_blank" rel="nofollow noopener noreferrer me"><span class="invisible">https://www.</span><span class="">patreon.com/mastodon</span><span class="invisible"></span></a>' }
+
+        it 'returns true' do
+          expect(subject.verifiable?).to be true
+        end
+      end
+
+      context 'for a link with misleading authentication' do
+        let(:value) { '<a href="https://google.com                                                                                            @h.43z.one" target="_blank" rel="nofollow noopener noreferrer me"><span class="invisible">https://</span><span class="">google.com</span><span class="invisible">                                                                                            @h.43z.one</span></a>' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
+
+      context 'for HTML that has more than just a link' do
+        let(:value) { '<a href="https://google.com" target="_blank" rel="nofollow noopener noreferrer me"><span class="invisible">https://</span><span class="">google.com</span><span class="invisible"></span></a>                                                                                            @h.43z.one' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
+
+      context 'for a link with different visible text' do
+        let(:value) { '<a href="https://google.com/bar">https://example.com/foo</a>' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
+
+      context 'for text that is a URL but is not linked' do
+        let(:value) { 'https://example.com/foo' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
+    end
+  end
+end