Fix XSS in wiki author email and name

In this commit we fix a XSS when rendering the wiki
commit info in the header.

app/helpers/wiki_page_version_helper.rb

+# frozen_string_literal: true
+
+module WikiPageVersionHelper
+  def wiki_page_version_author_url(wiki_page_version)
+    user = wiki_page_version.author
+    user.nil? ? "mailto:#{wiki_page_version.author_email}" : Gitlab::UrlBuilder.build(user)
+  end
+
+  def wiki_page_version_author_avatar(wiki_page_version)
+    image_tag(avatar_icon_for_email(wiki_page_version.author_email, 24), class: "avatar s24 float-none gl-mr-0!")
+  end
+
+  def wiki_page_version_author_header(wiki_page_version)
+    avatar = wiki_page_version_author_avatar(wiki_page_version)
+    name = "<strong>".html_safe + wiki_page_version.author_name + "</strong>".html_safe
+    link_start = "<a href='".html_safe + wiki_page_version_author_url(wiki_page_version) + "'>".html_safe
+
+    html_escape(_("Last edited by %{link_start}%{avatar} %{name}%{link_end}")) % { avatar: avatar, name: name, link_start: link_start, link_end: '</a>'.html_safe }
+  end
+end

app/views/shared/wikis/show.html.haml

@@ -7,7 +7,7 @@
   .nav-text.flex-fill
     %span.wiki-last-edit-by
       - if @page.last_version
-        = html_escape(_("Last edited by %{link_start}%{avatar} %{name}%{link_end}")) % { avatar: image_tag(avatar_icon_for_email(@page.last_version.author_email, 24), class: "avatar s24 float-none gl-mr-0!"), name: "<strong>#{@page.last_version.author_name}</strong>".html_safe, link_start: "<a href='#{@page.last_version.author_url}'>".html_safe, link_end: '</a>'.html_safe }
+        = wiki_page_version_author_header(@page.last_version)
         = time_ago_with_tooltip(@page.last_version.authored_date)
 
   .nav-controls.pb-md-3.pb-lg-0

changelogs/unreleased/security-fj-fix-xss-wiki-email.yml

+---
+title: Fix XSS in wiki author email and name
+merge_request:
+author:
+type: security

lib/gitlab/git/wiki_page_version.rb

@@ -3,6 +3,8 @@
 module Gitlab
   module Git
     class WikiPageVersion
+      include Gitlab::Utils::StrongMemoize
+
       attr_reader :commit, :format
 
       def initialize(commit, format)
@@ -12,9 +14,10 @@ module Gitlab
 
       delegate :message, :sha, :id, :author_name, :author_email, :authored_date, to: :commit
 
-      def author_url
-        user = ::User.find_by_any_email(author_email)
-        user.nil? ? "mailto:#{author_email}" : Gitlab::UrlBuilder.build(user)
+      def author
+        strong_memoize(:author) do
+          ::User.find_by_any_email(author_email)
+        end
       end
     end
   end

spec/helpers/wiki_page_version_helper_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe WikiPageVersionHelper do
+  let_it_be(:project) { create(:project, :public, :repository) }
+  let_it_be(:user) { create(:user, username: 'foo') }
+
+  let(:commit_with_user) { create(:commit, project: project, author: user)}
+  let(:commit_without_user) { create(:commit, project: project, author_name: 'Foo', author_email: 'foo@example.com')}
+  let(:wiki_page_version) { Gitlab::Git::WikiPageVersion.new(commit, nil) }
+
+  describe '#wiki_page_version_author_url' do
+    subject { helper.wiki_page_version_author_url(wiki_page_version) }
+
+    context 'when user exists' do
+      let(:commit) { commit_with_user }
+
+      it 'returns the link to the user profile' do
+        expect(subject).to eq('http://localhost/foo')
+      end
+    end
+
+    context 'when user does not exist' do
+      let(:commit) { commit_without_user }
+
+      it 'returns the mailto link' do
+        expect(subject).to eq "mailto:#{commit_without_user.author_email}"
+      end
+    end
+  end
+
+  describe '#wiki_page_version_author_avatar' do
+    let(:commit) { commit_with_user }
+
+    subject { helper.wiki_page_version_author_avatar(wiki_page_version) }
+
+    it 'returns the user avatar', :aggregate_failures do
+      avatar = Nokogiri::HTML.parse(subject)
+
+      expect(avatar.css('img')[0].attr('class')).to eq('avatar s24 float-none gl-mr-0! lazy')
+      expect(avatar.css('img')[0].attr('data-src')).not_to be_empty
+      expect(avatar.css('img')[0].attr('src')).not_to be_empty
+    end
+  end
+
+  describe '#wiki_page_version_author_header', :aggregate_failures do
+    let(:commit_with_xss) { create(:commit, project: project, author_email: "#' style=animation-name:blinking-dot onanimationstart=alert(document.domain) other", author_name: "<i>foo</i>") }
+    let(:header) { Nokogiri::HTML.parse(subject) }
+
+    subject { helper.wiki_page_version_author_header(wiki_page_version) }
+
+    context 'when user exists' do
+      let(:commit) { commit_with_user }
+
+      it 'renders commit header with user info' do
+        expect(header.css('a')[0].attr('href')).to eq("http://localhost/foo")
+        expect(header.css('a')[0].children[2].to_s).to eq("<strong>#{user.name}</strong>")
+      end
+    end
+
+    context 'when user does not exist' do
+      let(:commit) { commit_without_user }
+
+      it 'renders commit header with info from commit' do
+        expect(header.css('a')[0].attr('href')).to eq("mailto:#{commit.author_email}")
+        expect(header.css('a')[0].children[2].to_s).to eq("<strong>#{wiki_page_version.author_name}</strong>")
+      end
+    end
+
+    context 'when user info has XSS' do
+      let(:commit) { commit_with_xss }
+
+      it 'sets the right href and escapes HTML chars' do
+        expect(header.css('a')[0].attr('href')).to eq("mailto:#{commit.author_email}")
+        expect(header.css('a')[0].children[2].to_s).to eq("<strong>&lt;i&gt;foo&lt;/i&gt;</strong>")
+      end
+    end
+  end
+end

spec/lib/gitlab/git/wiki_page_version_spec.rb

@@ -4,24 +4,24 @@ require 'spec_helper'
 
 RSpec.describe Gitlab::Git::WikiPageVersion do
   let_it_be(:project) { create(:project, :public, :repository) }
-  let(:user) { create(:user, username: 'someone') }
+  let_it_be(:user) { create(:user, username: 'someone') }
 
-  describe '#author_url' do
-    subject(:author_url) { described_class.new(commit, nil).author_url }
+  describe '#author' do
+    subject(:author) { described_class.new(commit, nil).author }
 
     context 'user exists in gitlab' do
       let(:commit) { create(:commit, project: project, author: user) }
 
-      it 'returns the profile link of the user' do
-        expect(author_url).to eq('http://localhost/someone')
+      it 'returns the user' do
+        expect(author).to eq user
       end
     end
 
     context 'user does not exist in gitlab' do
       let(:commit) { create(:commit, project: project, author_email: "someone@somewebsite.com") }
 
-      it 'returns a mailto: url' do
-        expect(author_url).to eq('mailto:someone@somewebsite.com')
+      it 'returns nil' do
+        expect(author).to be_nil
       end
     end
   end