Pleroma/lib/pleroma/html.ex

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# Pleroma: A lightweight social networking server
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# 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)
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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}"
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Cachex.fetch!(:scrubber_cache, key, fn _key ->
object = Pleroma.Object.normalize(activity)
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ensure_scrubbed_html(content, scrubbers, object.data["fake"] || false, callback)
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end)
end
def get_cached_stripped_html_for_activity(content, activity, key) do
get_cached_scrubbed_html_for_activity(
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content,
FastSanitize.Sanitizer.StripTags,
activity,
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key,
&HtmlEntities.decode/1
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)
end
def ensure_scrubbed_html(
content,
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scrubbers,
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fake,
callback
) do
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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)
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{: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.
"""
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@valid_schemes Pleroma.Config.get([:uri_schemes, :valid_schemes], [])
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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
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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
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# credo:disable-for-previous-line
# No idea how to fix this one…
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@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",
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"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, [])
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@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
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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
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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
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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
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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}
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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], [])
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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",
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"me",
"ugc"
])
Meta.allow_tag_with_these_attributes(:a, ["name", "title"])
Meta.strip_everything_not_covered()
end