# Pleroma: A lightweight social networking server # Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/> # SPDX-License-Identifier: AGPL-3.0-only defmodule Pleroma.HTML do defp get_scrubbers(scrubber) when is_atom(scrubber), do: [scrubber] defp get_scrubbers(scrubbers) when is_list(scrubbers), do: scrubbers defp get_scrubbers(_), do: [Pleroma.HTML.Scrubber.Default] def get_scrubbers do Pleroma.Config.get([:markup, :scrub_policy]) |> get_scrubbers end def filter_tags(html, nil) do filter_tags(html, get_scrubbers()) end def filter_tags(html, scrubbers) when is_list(scrubbers) do Enum.reduce(scrubbers, html, fn scrubber, html -> filter_tags(html, scrubber) end) end def filter_tags(html, scrubber) do {:ok, content} = FastSanitize.Sanitizer.scrub(html, scrubber) content end def filter_tags(html), do: filter_tags(html, nil) def strip_tags(html), do: filter_tags(html, FastSanitize.Sanitizer.StripTags) def get_cached_scrubbed_html_for_activity( content, scrubbers, activity, key \\ "", callback \\ fn x -> x end ) do key = "#{key}#{generate_scrubber_signature(scrubbers)}|#{activity.id}" Cachex.fetch!(:scrubber_cache, key, fn _key -> object = Pleroma.Object.normalize(activity) ensure_scrubbed_html(content, scrubbers, object.data["fake"] || false, callback) end) end def get_cached_stripped_html_for_activity(content, activity, key) do get_cached_scrubbed_html_for_activity( content, FastSanitize.Sanitizer.StripTags, activity, key, &HtmlEntities.decode/1 ) end def ensure_scrubbed_html( content, scrubbers, fake, callback ) do content = content |> filter_tags(scrubbers) |> callback.() if fake do {:ignore, content} else {:commit, content} end end defp generate_scrubber_signature(scrubber) when is_atom(scrubber) do generate_scrubber_signature([scrubber]) end defp generate_scrubber_signature(scrubbers) do Enum.reduce(scrubbers, "", fn scrubber, signature -> "#{signature}#{to_string(scrubber)}" end) end def extract_first_external_url(_, nil), do: {:error, "No content"} def extract_first_external_url(object, content) do key = "URL|#{object.id}" Cachex.fetch!(:scrubber_cache, key, fn _key -> result = content |> Floki.filter_out("a.mention,a.hashtag,a[rel~=\"tag\"]") |> Floki.attribute("a", "href") |> Enum.at(0) {:commit, {:ok, result}} end) end end defmodule Pleroma.HTML.Scrubber.TwitterText do @moduledoc """ An HTML scrubbing policy which limits to twitter-style text. Only paragraphs, breaks and links are allowed through the filter. """ @valid_schemes Pleroma.Config.get([:uri_schemes, :valid_schemes], []) require FastSanitize.Sanitizer.Meta alias FastSanitize.Sanitizer.Meta Meta.strip_comments() # links Meta.allow_tag_with_uri_attributes(:a, ["href", "data-user", "data-tag"], @valid_schemes) Meta.allow_tag_with_this_attribute_values(:a, "class", [ "hashtag", "u-url", "mention", "u-url mention", "mention u-url" ]) Meta.allow_tag_with_this_attribute_values(:a, "rel", [ "tag", "nofollow", "noopener", "noreferrer" ]) Meta.allow_tag_with_these_attributes(:a, ["name", "title"]) # paragraphs and linebreaks Meta.allow_tag_with_these_attributes(:br, []) Meta.allow_tag_with_these_attributes(:p, []) # microformats Meta.allow_tag_with_this_attribute_values(:span, "class", ["h-card"]) Meta.allow_tag_with_these_attributes(:span, []) # allow inline images for custom emoji if Pleroma.Config.get([:markup, :allow_inline_images]) do # restrict img tags to http/https only, because of MediaProxy. Meta.allow_tag_with_uri_attributes(:img, ["src"], ["http", "https"]) Meta.allow_tag_with_these_attributes(:img, [ "width", "height", "class", "title", "alt" ]) end Meta.strip_everything_not_covered() end defmodule Pleroma.HTML.Scrubber.Default do @doc "The default HTML scrubbing policy: no " require FastSanitize.Sanitizer.Meta alias FastSanitize.Sanitizer.Meta # credo:disable-for-previous-line # No idea how to fix this one… @valid_schemes Pleroma.Config.get([:uri_schemes, :valid_schemes], []) Meta.strip_comments() Meta.allow_tag_with_uri_attributes(:a, ["href", "data-user", "data-tag"], @valid_schemes) Meta.allow_tag_with_this_attribute_values(:a, "class", [ "hashtag", "u-url", "mention", "u-url mention", "mention u-url" ]) Meta.allow_tag_with_this_attribute_values(:a, "rel", [ "tag", "nofollow", "noopener", "noreferrer", "ugc" ]) Meta.allow_tag_with_these_attributes(:a, ["name", "title"]) Meta.allow_tag_with_these_attributes(:abbr, ["title"]) Meta.allow_tag_with_these_attributes(:b, []) Meta.allow_tag_with_these_attributes(:blockquote, []) Meta.allow_tag_with_these_attributes(:br, []) Meta.allow_tag_with_these_attributes(:code, []) Meta.allow_tag_with_these_attributes(:del, []) Meta.allow_tag_with_these_attributes(:em, []) Meta.allow_tag_with_these_attributes(:i, []) Meta.allow_tag_with_these_attributes(:li, []) Meta.allow_tag_with_these_attributes(:ol, []) Meta.allow_tag_with_these_attributes(:p, []) Meta.allow_tag_with_these_attributes(:pre, []) Meta.allow_tag_with_these_attributes(:strong, []) Meta.allow_tag_with_these_attributes(:sub, []) Meta.allow_tag_with_these_attributes(:sup, []) Meta.allow_tag_with_these_attributes(:u, []) Meta.allow_tag_with_these_attributes(:ul, []) Meta.allow_tag_with_this_attribute_values(:span, "class", ["h-card"]) Meta.allow_tag_with_these_attributes(:span, []) @allow_inline_images Pleroma.Config.get([:markup, :allow_inline_images]) if @allow_inline_images do # restrict img tags to http/https only, because of MediaProxy. Meta.allow_tag_with_uri_attributes(:img, ["src"], ["http", "https"]) Meta.allow_tag_with_these_attributes(:img, [ "width", "height", "class", "title", "alt" ]) end if Pleroma.Config.get([:markup, :allow_tables]) do Meta.allow_tag_with_these_attributes(:table, []) Meta.allow_tag_with_these_attributes(:tbody, []) Meta.allow_tag_with_these_attributes(:td, []) Meta.allow_tag_with_these_attributes(:th, []) Meta.allow_tag_with_these_attributes(:thead, []) Meta.allow_tag_with_these_attributes(:tr, []) end if Pleroma.Config.get([:markup, :allow_headings]) do Meta.allow_tag_with_these_attributes(:h1, []) Meta.allow_tag_with_these_attributes(:h2, []) Meta.allow_tag_with_these_attributes(:h3, []) Meta.allow_tag_with_these_attributes(:h4, []) Meta.allow_tag_with_these_attributes(:h5, []) end if Pleroma.Config.get([:markup, :allow_fonts]) do Meta.allow_tag_with_these_attributes(:font, ["face"]) end Meta.strip_everything_not_covered() end defmodule Pleroma.HTML.Transform.MediaProxy do @moduledoc "Transforms inline image URIs to use MediaProxy." alias Pleroma.Web.MediaProxy def before_scrub(html), do: html def scrub_attribute(:img, {"src", "http" <> target}) do media_url = ("http" <> target) |> MediaProxy.url() {"src", media_url} end def scrub_attribute(_tag, attribute), do: attribute def scrub({:img, attributes, children}) do attributes = attributes |> Enum.map(fn attr -> scrub_attribute(:img, attr) end) |> Enum.reject(&is_nil(&1)) {:img, attributes, children} end def scrub({:comment, _text, _children}), do: "" def scrub({tag, attributes, children}), do: {tag, attributes, children} def scrub({_tag, children}), do: children def scrub(text), do: text end defmodule Pleroma.HTML.Scrubber.LinksOnly do @moduledoc """ An HTML scrubbing policy which limits to links only. """ @valid_schemes Pleroma.Config.get([:uri_schemes, :valid_schemes], []) require FastSanitize.Sanitizer.Meta alias FastSanitize.Sanitizer.Meta Meta.strip_comments() # links Meta.allow_tag_with_uri_attributes(:a, ["href"], @valid_schemes) Meta.allow_tag_with_this_attribute_values(:a, "rel", [ "tag", "nofollow", "noopener", "noreferrer", "me", "ugc" ]) Meta.allow_tag_with_these_attributes(:a, ["name", "title"]) Meta.strip_everything_not_covered() end