From 4ed2618f6c732ba1009510f5698a5d981a151925 Mon Sep 17 00:00:00 2001
From: Fong-Wan Chau <fongwan@chaurocks.com>
Date: Sun, 17 Mar 2019 09:46:46 -0400
Subject: [PATCH] Allow 'rel' attribute on `<a>` link with specific values (for
 hashtag recognition).

---
 lib/pleroma/html.ex                                    | 14 ++++++++++++++
 test/html_test.exs                                     |  8 ++++++++
 test/web/mastodon_api/mastodon_api_controller_test.exs |  2 +-
 test/web/twitter_api/views/activity_view_test.exs      |  2 +-
 4 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/lib/pleroma/html.ex b/lib/pleroma/html.ex
index 05253157e..5b152d926 100644
--- a/lib/pleroma/html.ex
+++ b/lib/pleroma/html.ex
@@ -95,6 +95,13 @@ defmodule Pleroma.HTML.Scrubber.TwitterText do
   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
   Meta.allow_tag_with_these_attributes("a", ["name", "title", "class"])
 
+  Meta.allow_tag_with_this_attribute_values("a", "rel", [
+    "tag",
+    "nofollow",
+    "noopener",
+    "noreferrer"
+  ])
+
   # paragraphs and linebreaks
   Meta.allow_tag_with_these_attributes("br", [])
   Meta.allow_tag_with_these_attributes("p", [])
@@ -137,6 +144,13 @@ defmodule Pleroma.HTML.Scrubber.Default do
   Meta.allow_tag_with_uri_attributes("a", ["href", "data-user", "data-tag"], @valid_schemes)
   Meta.allow_tag_with_these_attributes("a", ["name", "title", "class"])
 
+  Meta.allow_tag_with_this_attribute_values("a", "rel", [
+    "tag",
+    "nofollow",
+    "noopener",
+    "noreferrer"
+  ])
+
   Meta.allow_tag_with_these_attributes("abbr", ["title"])
 
   Meta.allow_tag_with_these_attributes("b", [])
diff --git a/test/html_test.exs b/test/html_test.exs
index 29cab17f3..0b5d3d892 100644
--- a/test/html_test.exs
+++ b/test/html_test.exs
@@ -10,6 +10,8 @@ defmodule Pleroma.HTMLTest do
     <b>this is in bold</b>
     <p>this is a paragraph</p>
     this is a linebreak<br />
+    this is a link with allowed "rel" attribute: <a href="http://example.com/" rel="tag">example.com</a>
+    this is a link with not allowed "rel" attribute: <a href="http://example.com/" rel="tag noallowed">example.com</a>
     this is an image: <img src="http://example.com/image.jpg"><br />
     <script>alert('hacked')</script>
   """
@@ -24,6 +26,8 @@ defmodule Pleroma.HTMLTest do
       this is in bold
         this is a paragraph
         this is a linebreak
+        this is a link with allowed "rel" attribute: example.com
+        this is a link with not allowed "rel" attribute: example.com
         this is an image: 
         alert('hacked')
       """
@@ -44,6 +48,8 @@ defmodule Pleroma.HTMLTest do
       this is in bold
         <p>this is a paragraph</p>
         this is a linebreak<br />
+        this is a link with allowed "rel" attribute: <a href="http://example.com/" rel="tag">example.com</a>
+        this is a link with not allowed "rel" attribute: <a href="http://example.com/">example.com</a>
         this is an image: <img src="http://example.com/image.jpg" /><br />
         alert('hacked')
       """
@@ -66,6 +72,8 @@ defmodule Pleroma.HTMLTest do
       <b>this is in bold</b>
         <p>this is a paragraph</p>
         this is a linebreak<br />
+        this is a link with allowed "rel" attribute: <a href="http://example.com/" rel="tag">example.com</a>
+        this is a link with not allowed "rel" attribute: <a href="http://example.com/">example.com</a>
         this is an image: <img src="http://example.com/image.jpg" /><br />
         alert('hacked')
       """
diff --git a/test/web/mastodon_api/mastodon_api_controller_test.exs b/test/web/mastodon_api/mastodon_api_controller_test.exs
index 059d5237d..74bf05708 100644
--- a/test/web/mastodon_api/mastodon_api_controller_test.exs
+++ b/test/web/mastodon_api/mastodon_api_controller_test.exs
@@ -1632,7 +1632,7 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPIControllerTest do
       assert user = json_response(conn, 200)
 
       assert user["note"] ==
-               ~s(I drink <a class="hashtag" data-tag="cofe" href="http://localhost:4001/tag/cofe">#cofe</a> with <span class="h-card"><a data-user=") <>
+               ~s(I drink <a class="hashtag" data-tag="cofe" href="http://localhost:4001/tag/cofe" rel="tag">#cofe</a> with <span class="h-card"><a data-user=") <>
                  user2.id <>
                  ~s(" class="u-url mention" href=") <>
                  user2.ap_id <> ~s(">@<span>) <> user2.nickname <> ~s(</span></a></span>)
diff --git a/test/web/twitter_api/views/activity_view_test.exs b/test/web/twitter_api/views/activity_view_test.exs
index 6f0786b1c..d9df01c6e 100644
--- a/test/web/twitter_api/views/activity_view_test.exs
+++ b/test/web/twitter_api/views/activity_view_test.exs
@@ -82,7 +82,7 @@ defmodule Pleroma.Web.TwitterAPI.ActivityViewTest do
     result = ActivityView.render("activity.json", activity: activity)
 
     assert result["statusnet_html"] ==
-             "<a class=\"hashtag\" data-tag=\"bike\" href=\"http://localhost:4001/tag/bike\">#Bike</a> log - Commute Tuesday<br /><a href=\"https://pla.bike/posts/20181211/\">https://pla.bike/posts/20181211/</a><br /><a class=\"hashtag\" data-tag=\"cycling\" href=\"http://localhost:4001/tag/cycling\">#cycling</a> <a class=\"hashtag\" data-tag=\"chscycling\" href=\"http://localhost:4001/tag/chscycling\">#CHScycling</a> <a class=\"hashtag\" data-tag=\"commute\" href=\"http://localhost:4001/tag/commute\">#commute</a><br />MVIMG_20181211_054020.jpg"
+             "<a class=\"hashtag\" data-tag=\"bike\" href=\"http://localhost:4001/tag/bike\" rel=\"tag\">#Bike</a> log - Commute Tuesday<br /><a href=\"https://pla.bike/posts/20181211/\">https://pla.bike/posts/20181211/</a><br /><a class=\"hashtag\" data-tag=\"cycling\" href=\"http://localhost:4001/tag/cycling\" rel=\"tag\">#cycling</a> <a class=\"hashtag\" data-tag=\"chscycling\" href=\"http://localhost:4001/tag/chscycling\" rel=\"tag\">#CHScycling</a> <a class=\"hashtag\" data-tag=\"commute\" href=\"http://localhost:4001/tag/commute\" rel=\"tag\">#commute</a><br />MVIMG_20181211_054020.jpg"
 
     assert result["text"] ==
              "#Bike log - Commute Tuesday\nhttps://pla.bike/posts/20181211/\n#cycling #CHScycling #commute\nMVIMG_20181211_054020.jpg"