Merge branch 'issue-63298-asciidoc-sanitization' into 'master'

Prevent excessive sanitization of AsciiDoc ouptut

Closes #63298

See merge request gitlab-org/gitlab-ce!30290

9 files changed, 326 insertions, 113 deletions

diff --git a/app/assets/stylesheets/framework.scss b/app/assets/stylesheets/framework.scss
index 9b1d9d51f9c..82b4ec750ff 100644
--- a/app/assets/stylesheets/framework.scss
+++ b/app/assets/stylesheets/framework.scss
@@ -9,7 +9,6 @@
 
 @import 'framework/animations';
 @import 'framework/vue_transitions';
-@import 'framework/asciidoctor';
 @import 'framework/banner';
 @import 'framework/blocks';
 @import 'framework/buttons';
diff --git a/app/assets/stylesheets/framework/asciidoctor.scss b/app/assets/stylesheets/framework/asciidoctor.scss
deleted file mode 100644
index 1586265d40e..00000000000
--- a/app/assets/stylesheets/framework/asciidoctor.scss
+++ /dev/null
@@ -1,27 +0,0 @@
-.admonitionblock td.icon {
-  width: 1%;
-
-  [class^='fa icon-'] {
-    @extend .fa-2x;
-  }
-
-  .icon-note {
-    @extend .fa-thumb-tack;
-  }
-
-  .icon-tip {
-    @extend .fa-lightbulb-o;
-  }
-
-  .icon-warning {
-    @extend .fa-exclamation-triangle;
-  }
-
-  .icon-caution {
-    @extend .fa-fire;
-  }
-
-  .icon-important {
-    @extend .fa-exclamation-circle;
-  }
-}
diff --git a/app/assets/stylesheets/framework/typography.scss b/app/assets/stylesheets/framework/typography.scss
index 7baab478034..c201605e83d 100644
--- a/app/assets/stylesheets/framework/typography.scss
+++ b/app/assets/stylesheets/framework/typography.scss
@@ -1,5 +1,5 @@
 /**
- * Apply Markdown typography
+ * Apply Markup (Markdown/AsciiDoc) typography
  *
  */
 .md:not(.use-csslab) {
@@ -245,6 +245,21 @@
     }
   }
 
+  ul.checklist,
+  ul.none,
+  ol.none,
+  ul.no-bullet,
+  ol.no-bullet,
+  ol.unnumbered,
+  ul.unstyled,
+  ol.unstyled {
+    list-style-type: none;
+
+    li {
+      margin-left: 0;
+    }
+  }
+
   li {
     line-height: 1.6em;
     margin-left: 25px;
@@ -321,6 +336,54 @@
       visibility: visible;
     }
   }
+
+  .big {
+    font-size: larger;
+  }
+
+  .small {
+    font-size: smaller;
+  }
+
+  .underline {
+    text-decoration: underline;
+  }
+
+  .overline {
+    text-decoration: overline;
+  }
+
+  .line-through {
+    text-decoration: line-through;
+  }
+
+  .admonitionblock td.icon {
+    width: 1%;
+
+    [class^='fa icon-'] {
+      @extend .fa-2x;
+    }
+
+    .icon-note {
+      @extend .fa-thumb-tack;
+    }
+
+    .icon-tip {
+      @extend .fa-lightbulb-o;
+    }
+
+    .icon-warning {
+      @extend .fa-exclamation-triangle;
+    }
+
+    .icon-caution {
+      @extend .fa-fire;
+    }
+
+    .icon-important {
+      @extend .fa-exclamation-circle;
+    }
+  }
 }
 
 
diff --git a/changelogs/unreleased/63298-prevent-excessive-sanitization-asciidoc.yml b/changelogs/unreleased/63298-prevent-excessive-sanitization-asciidoc.yml
new file mode 100644
index 00000000000..cd8206cdb99
--- /dev/null
+++ b/changelogs/unreleased/63298-prevent-excessive-sanitization-asciidoc.yml
@@ -0,0 +1,5 @@
+---
+title: "Prevent excessive sanitization of AsciiDoc ouptut"
+merge_request: 30290
+author: Guillaume Grossetie
+type: added
\ No newline at end of file
diff --git a/lib/banzai/filter/ascii_doc_sanitization_filter.rb b/lib/banzai/filter/ascii_doc_sanitization_filter.rb
new file mode 100644
index 00000000000..a78bb60103c
--- /dev/null
+++ b/lib/banzai/filter/ascii_doc_sanitization_filter.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    # Sanitize HTML produced by AsciiDoc/Asciidoctor.
+    #
+    # Extends Banzai::Filter::BaseSanitizationFilter with specific rules.
+    class AsciiDocSanitizationFilter < Banzai::Filter::BaseSanitizationFilter
+      # Classes used by Asciidoctor to style components
+      ADMONITION_CLASSES = %w(fa icon-note icon-tip icon-warning icon-caution icon-important).freeze
+      CALLOUT_CLASSES = ['conum'].freeze
+      CHECKLIST_CLASSES = %w(fa fa-check-square-o fa-square-o).freeze
+
+      LIST_CLASSES = %w(checklist none no-bullet unnumbered unstyled).freeze
+
+      ELEMENT_CLASSES_WHITELIST = {
+        span: %w(big small underline overline line-through).freeze,
+        div: ['admonitionblock'].freeze,
+        td: ['icon'].freeze,
+        i: ADMONITION_CLASSES + CALLOUT_CLASSES + CHECKLIST_CLASSES,
+        ul: LIST_CLASSES,
+        ol: LIST_CLASSES
+      }.freeze
+
+      def customize_whitelist(whitelist)
+        # Allow marks
+        whitelist[:elements].push('mark')
+
+        # Allow any classes in `span`, `i`, `div`, `td`, `ul` and `ol` elements
+        # but then remove any unknown classes
+        whitelist[:attributes]['span'] = %w(class)
+        whitelist[:attributes]['div'].push('class')
+        whitelist[:attributes]['td'] = %w(class)
+        whitelist[:attributes]['i'] = %w(class)
+        whitelist[:attributes]['ul'] = %w(class)
+        whitelist[:attributes]['ol'] = %w(class)
+        whitelist[:transformers].push(self.class.remove_element_classes)
+
+        whitelist
+      end
+
+      class << self
+        def remove_element_classes
+          lambda do |env|
+            node = env[:node]
+
+            return unless (classes_whitelist = ELEMENT_CLASSES_WHITELIST[node.name.to_sym])
+            return unless node.has_attribute?('class')
+
+            classes = node['class'].strip.split(' ')
+            allowed_classes = (classes & classes_whitelist)
+            if allowed_classes.empty?
+              node.remove_attribute('class')
+            else
+              node['class'] = allowed_classes.join(' ')
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/banzai/filter/base_sanitization_filter.rb b/lib/banzai/filter/base_sanitization_filter.rb
new file mode 100644
index 00000000000..420e92cb1e8
--- /dev/null
+++ b/lib/banzai/filter/base_sanitization_filter.rb
@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    # Sanitize HTML produced by markup languages (Markdown, AsciiDoc...).
+    # Specific rules are implemented in dedicated filters:
+    #
+    # - Banzai::Filter::SanitizationFilter (Markdown)
+    # - Banzai::Filter::AsciiDocSanitizationFilter (AsciiDoc/Asciidoctor)
+    #
+    # Extends HTML::Pipeline::SanitizationFilter with common rules.
+    class BaseSanitizationFilter < HTML::Pipeline::SanitizationFilter
+      include Gitlab::Utils::StrongMemoize
+
+      UNSAFE_PROTOCOLS = %w(data javascript vbscript).freeze
+
+      def whitelist
+        strong_memoize(:whitelist) do
+          whitelist = super.deep_dup
+
+          # Allow span elements
+          whitelist[:elements].push('span')
+
+          # Allow data-math-style attribute in order to support LaTeX formatting
+          whitelist[:attributes]['code'] = %w(data-math-style)
+          whitelist[:attributes]['pre'] = %w(data-math-style)
+
+          # Allow html5 details/summary elements
+          whitelist[:elements].push('details')
+          whitelist[:elements].push('summary')
+
+          # Allow abbr elements with title attribute
+          whitelist[:elements].push('abbr')
+          whitelist[:attributes]['abbr'] = %w(title)
+
+          # Disallow `name` attribute globally, allow on `a`
+          whitelist[:attributes][:all].delete('name')
+          whitelist[:attributes]['a'].push('name')
+
+          # Allow any protocol in `a` elements
+          # and then remove links with unsafe protocols
+          whitelist[:protocols].delete('a')
+          whitelist[:transformers].push(self.class.remove_unsafe_links)
+
+          # Remove `rel` attribute from `a` elements
+          whitelist[:transformers].push(self.class.remove_rel)
+
+          customize_whitelist(whitelist)
+        end
+      end
+
+      def customize_whitelist(whitelist)
+        raise NotImplementedError
+      end
+
+      class << self
+        def remove_unsafe_links
+          lambda do |env|
+            node = env[:node]
+
+            return unless node.name == 'a'
+            return unless node.has_attribute?('href')
+
+            begin
+              node['href'] = node['href'].strip
+              uri = Addressable::URI.parse(node['href'])
+
+              return unless uri.scheme
+
+              # Remove all invalid scheme characters before checking against the
+              # list of unsafe protocols.
+              #
+              # See https://tools.ietf.org/html/rfc3986#section-3.1
+              scheme = uri.scheme
+                           .strip
+                           .downcase
+                           .gsub(/[^A-Za-z0-9\+\.\-]+/, '')
+
+              node.remove_attribute('href') if UNSAFE_PROTOCOLS.include?(scheme)
+            rescue Addressable::URI::InvalidURIError
+              node.remove_attribute('href')
+            end
+          end
+        end
+
+        def remove_rel
+          lambda do |env|
+            if env[:node_name] == 'a'
+              env[:node].remove_attribute('rel')
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/banzai/filter/sanitization_filter.rb b/lib/banzai/filter/sanitization_filter.rb
index a4a06eae7b7..f57e57890f8 100644
--- a/lib/banzai/filter/sanitization_filter.rb
+++ b/lib/banzai/filter/sanitization_filter.rb
@@ -2,23 +2,13 @@
 
 module Banzai
   module Filter
-    # Sanitize HTML
+    # Sanitize HTML produced by Markdown.
     #
-    # Extends HTML::Pipeline::SanitizationFilter with a custom whitelist.
-    class SanitizationFilter < HTML::Pipeline::SanitizationFilter
-      include Gitlab::Utils::StrongMemoize
-
-      UNSAFE_PROTOCOLS        = %w(data javascript vbscript).freeze
+    # Extends Banzai::Filter::BaseSanitizationFilter with specific rules.
+    class SanitizationFilter < Banzai::Filter::BaseSanitizationFilter
+      # Styles used by Markdown for table alignment
       TABLE_ALIGNMENT_PATTERN = /text-align: (?<alignment>center|left|right)/.freeze
 
-      def whitelist
-        strong_memoize(:whitelist) do
-          customize_whitelist(super.deep_dup)
-        end
-      end
-
-      private
-
       def customize_whitelist(whitelist)
         # Allow table alignment; we whitelist specific text-align values in a
         # transformer below
@@ -26,36 +16,9 @@ module Banzai
         whitelist[:attributes]['td'] = %w(style)
         whitelist[:css] = { properties: ['text-align'] }
 
-        # Allow span elements
-        whitelist[:elements].push('span')
-
-        # Allow data-math-style attribute in order to support LaTeX formatting
-        whitelist[:attributes]['code'] = %w(data-math-style)
-        whitelist[:attributes]['pre'] = %w(data-math-style)
-
-        # Allow html5 details/summary elements
-        whitelist[:elements].push('details')
-        whitelist[:elements].push('summary')
-
-        # Allow abbr elements with title attribute
-        whitelist[:elements].push('abbr')
-        whitelist[:attributes]['abbr'] = %w(title)
-
         # Allow the 'data-sourcepos' from CommonMark on all elements
         whitelist[:attributes][:all].push('data-sourcepos')
 
-        # Disallow `name` attribute globally, allow on `a`
-        whitelist[:attributes][:all].delete('name')
-        whitelist[:attributes]['a'].push('name')
-
-        # Allow any protocol in `a` elements
-        # and then remove links with unsafe protocols
-        whitelist[:protocols].delete('a')
-        whitelist[:transformers].push(self.class.remove_unsafe_links)
-
-        # Remove `rel` attribute from `a` elements
-        whitelist[:transformers].push(self.class.remove_rel)
-
         # Remove any `style` properties not required for table alignment
         whitelist[:transformers].push(self.class.remove_unsafe_table_style)
 
@@ -69,43 +32,6 @@ module Banzai
       end
 
       class << self
-        def remove_unsafe_links
-          lambda do |env|
-            node = env[:node]
-
-            return unless node.name == 'a'
-            return unless node.has_attribute?('href')
-
-            begin
-              node['href'] = node['href'].strip
-              uri = Addressable::URI.parse(node['href'])
-
-              return unless uri.scheme
-
-              # Remove all invalid scheme characters before checking against the
-              # list of unsafe protocols.
-              #
-              # See https://tools.ietf.org/html/rfc3986#section-3.1
-              scheme = uri.scheme
-                .strip
-                .downcase
-                .gsub(/[^A-Za-z0-9\+\.\-]+/, '')
-
-              node.remove_attribute('href') if UNSAFE_PROTOCOLS.include?(scheme)
-            rescue Addressable::URI::InvalidURIError
-              node.remove_attribute('href')
-            end
-          end
-        end
-
-        def remove_rel
-          lambda do |env|
-            if env[:node_name] == 'a'
-              env[:node].remove_attribute('rel')
-            end
-          end
-        end
-
         def remove_unsafe_table_style
           lambda do |env|
             node = env[:node]
diff --git a/lib/banzai/pipeline/ascii_doc_pipeline.rb b/lib/banzai/pipeline/ascii_doc_pipeline.rb
index 6be489c6572..d25b74b23b2 100644
--- a/lib/banzai/pipeline/ascii_doc_pipeline.rb
+++ b/lib/banzai/pipeline/ascii_doc_pipeline.rb
@@ -5,7 +5,7 @@ module Banzai
     class AsciiDocPipeline < BasePipeline
       def self.filters
         FilterArray[
-          Filter::SanitizationFilter,
+          Filter::AsciiDocSanitizationFilter,
           Filter::SyntaxHighlightFilter,
           Filter::ExternalLinkFilter,
           Filter::PlantumlFilter,
diff --git a/spec/lib/gitlab/asciidoc_spec.rb b/spec/lib/gitlab/asciidoc_spec.rb
index 8f2434acd26..ff002acbd35 100644
--- a/spec/lib/gitlab/asciidoc_spec.rb
+++ b/spec/lib/gitlab/asciidoc_spec.rb
@@ -45,28 +45,117 @@ module Gitlab
       end
 
       context "XSS" do
-        links = {
-          'links' => {
+        items = {
+          'link with extra attribute' => {
             input: 'link:mylink"onmouseover="alert(1)[Click Here]',
             output: "<div>\n<p><a href=\"mylink\">Click Here</a></p>\n</div>"
           },
-          'images' => {
+          'link with unsafe scheme' => {
+              input: 'link:data://danger[Click Here]',
+              output: "<div>\n<p><a>Click Here</a></p>\n</div>"
+          },
+          'image with onerror' => {
             input: 'image:https://localhost.com/image.png[Alt text" onerror="alert(7)]',
             output: "<div>\n<p><span><img src=\"https://localhost.com/image.png\" alt='Alt text\" onerror=\"alert(7)'></span></p>\n</div>"
           },
-          'pre' => {
+          'fenced code with inline script' => {
             input: '```mypre"><script>alert(3)</script>',
             output: "<div>\n<div>\n<pre class=\"code highlight js-syntax-highlight plaintext\" lang=\"plaintext\" v-pre=\"true\"><code><span id=\"LC1\" class=\"line\" lang=\"plaintext\">\"&gt;</span></code></pre>\n</div>\n</div>"
           }
         }
 
-        links.each do |name, data|
+        items.each do |name, data|
           it "does not convert dangerous #{name} into HTML" do
             expect(render(data[:input], context)).to include(data[:output])
           end
         end
       end
 
+      context 'with admonition' do
+        it 'preserves classes' do
+          input = <<~ADOC
+            NOTE: An admonition paragraph, like this note, grabs the reader’s attention.
+          ADOC
+
+          output = <<~HTML
+            <div class="admonitionblock">
+            <table>
+            <tr>
+            <td class="icon">
+            <i class="fa icon-note" title="Note"></i>
+            </td>
+            <td>
+            An admonition paragraph, like this note, grabs the reader’s attention.
+            </td>
+            </tr>
+            </table>
+            </div>
+          HTML
+
+          expect(render(input, context)).to include(output.strip)
+        end
+      end
+
+      context 'with checklist' do
+        it 'preserves classes' do
+          input = <<~ADOC
+            * [x] checked
+            * [ ] not checked
+          ADOC
+
+          output = <<~HTML
+            <div>
+            <ul class="checklist">
+            <li>
+            <p><i class="fa fa-check-square-o"></i> checked</p>
+            </li>
+            <li>
+            <p><i class="fa fa-square-o"></i> not checked</p>
+            </li>
+            </ul>
+            </div>
+          HTML
+
+          expect(render(input, context)).to include(output.strip)
+        end
+      end
+
+      context 'with marks' do
+        it 'preserves classes' do
+          input = <<~ADOC
+            Werewolves are allergic to #cassia cinnamon#.
+
+            Did the werewolves read the [.small]#small print#?
+
+            Where did all the [.underline.small]#cores# run off to?
+
+            We need [.line-through]#ten# make that twenty VMs.
+
+            [.big]##O##nce upon an infinite loop.
+          ADOC
+
+          output = <<~HTML
+            <div>
+            <p>Werewolves are allergic to <mark>cassia cinnamon</mark>.</p>
+            </div>
+            <div>
+            <p>Did the werewolves read the <span class="small">small print</span>?</p>
+            </div>
+            <div>
+            <p>Where did all the <span class="underline small">cores</span> run off to?</p>
+            </div>
+            <div>
+            <p>We need <span class="line-through">ten</span> make that twenty VMs.</p>
+            </div>
+            <div>
+            <p><span class="big">O</span>nce upon an infinite loop.</p>
+            </div>
+          HTML
+
+          expect(render(input, context)).to include(output.strip)
+        end
+      end
+
       context 'with fenced block' do
         it 'highlights syntax' do
           input = <<~ADOC