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diff --git a/changelog.d/3895.add b/changelog.d/3895.add
new file mode 100644
index 000000000..5b1737ebd
--- /dev/null
+++ b/changelog.d/3895.add
@@ -0,0 +1 @@
+Uploaded media content-type is scrubbed before serving the files to limit the security impact of some attachments
diff --git a/lib/pleroma/web/plugs/uploaded_media.ex b/lib/pleroma/web/plugs/uploaded_media.ex
index 8b3bc9acb..38c00c1a3 100644
--- a/lib/pleroma/web/plugs/uploaded_media.ex
+++ b/lib/pleroma/web/plugs/uploaded_media.ex
@@ -1,114 +1,137 @@
# Pleroma: A lightweight social networking server
# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.Plugs.UploadedMedia do
@moduledoc """
"""
import Plug.Conn
import Pleroma.Web.Gettext
require Logger
alias Pleroma.Web.MediaProxy
@behaviour Plug
# no slashes
@path "media"
@default_cache_control_header "public, max-age=1209600"
def init(_opts) do
static_plug_opts =
[
headers: %{"cache-control" => @default_cache_control_header},
cache_control_for_etags: @default_cache_control_header
]
|> Keyword.put(:from, "__unconfigured_media_plug")
|> Keyword.put(:at, "/__unconfigured_media_plug")
|> Plug.Static.init()
%{static_plug_opts: static_plug_opts}
end
def call(%{request_path: <<"/", @path, "/", file::binary>>} = conn, opts) do
conn =
case fetch_query_params(conn) do
%{query_params: %{"name" => name}} = conn ->
name = String.replace(name, ~s["], ~s[\\"])
put_resp_header(conn, "content-disposition", ~s[inline; filename="#{name}"])
conn ->
conn
end
|> merge_resp_headers([{"content-security-policy", "sandbox"}])
config = Pleroma.Config.get(Pleroma.Upload)
with uploader <- Keyword.fetch!(config, :uploader),
proxy_remote = Keyword.get(config, :proxy_remote, false),
{:ok, get_method} <- uploader.get_file(file),
false <- media_is_banned(conn, get_method) do
get_media(conn, get_method, proxy_remote, opts)
+ |> scrub_mime()
else
_ ->
conn
|> send_resp(:internal_server_error, dgettext("errors", "Failed"))
|> halt()
end
end
def call(conn, _opts), do: conn
defp media_is_banned(%{request_path: path} = _conn, {:static_dir, _}) do
MediaProxy.in_banned_urls(Pleroma.Upload.base_url() <> path)
end
defp media_is_banned(_, {:url, url}), do: MediaProxy.in_banned_urls(url)
defp media_is_banned(_, _), do: false
defp get_media(conn, {:static_dir, directory}, _, opts) do
static_opts =
Map.get(opts, :static_plug_opts)
|> Map.put(:at, [@path])
|> Map.put(:from, directory)
conn = Plug.Static.call(conn, static_opts)
if conn.halted do
conn
else
conn
|> send_resp(:not_found, dgettext("errors", "Not found"))
|> halt()
end
end
defp get_media(conn, {:url, url}, true, _) do
proxy_opts = [
http: [
follow_redirect: true,
pool: :upload
]
]
conn
|> Pleroma.ReverseProxy.call(url, proxy_opts)
end
defp get_media(conn, {:url, url}, _, _) do
conn
|> Phoenix.Controller.redirect(external: url)
|> halt()
end
defp get_media(conn, unknown, _, _) do
Logger.error("#{__MODULE__}: Unknown get startegy: #{inspect(unknown)}")
conn
|> send_resp(:internal_server_error, dgettext("errors", "Internal Error"))
|> halt()
end
+
+ defp scrub_mime(%Plug.Conn{resp_headers: headers} = conn) do
+ [{_, mimetype}] = Enum.filter(headers, fn {x, _y} -> match?("content-type", x) end)
+
+ [_type, subtype] = String.split(mimetype, "/")
+
+ cond do
+ String.contains?(subtype, ["javascript", "ecmascript", "jscript"]) ->
+ force_plaintext(conn)
+
+ String.contains?(mimetype, ["text/html", "text/xml", "application/xml"]) ->
+ force_plaintext(conn)
+
+ true ->
+ conn
+ end
+ end
+
+ defp force_plaintext(conn) do
+ conn
+ |> merge_resp_headers([{"content-type", "text/plain"}])
+ end
end
diff --git a/test/fixtures/snow.js b/test/fixtures/snow.js
new file mode 100644
index 000000000..ff53af709
--- /dev/null
+++ b/test/fixtures/snow.js
@@ -0,0 +1,32 @@
+function createSnowflake() {
+ const snowflake = document.createElement('span');
+ snowflake.innerHTML = '❅';
+ snowflake.style.position = 'absolute';
+ snowflake.style.color = '#fff';
+ snowflake.style.userSelect = 'none';
+ snowflake.style.pointerEvents = 'none';
+ snowflake.style.fontSize = Math.random() * 20 + 'px';
+ snowflake.style.left = Math.random() * window.innerWidth + 'px';
+ snowflake.style.animation = 'fall ' + (Math.random() * 5 + 5) + 's linear infinite';
+ return snowflake;
+}
+
+function createSnowfall() {
+ const snowfallContainer = document.createElement('div');
+ snowfallContainer.style.position = 'fixed';
+ snowfallContainer.style.top = '0';
+ snowfallContainer.style.left = '0';
+ snowfallContainer.style.width = '100%';
+ snowfallContainer.style.height = '100%';
+ snowfallContainer.style.pointerEvents = 'none';
+ snowfallContainer.style.zIndex = '9999';
+
+ for (let i = 0; i < 50; i++) {
+ const snowflake = createSnowflake();
+ snowfallContainer.appendChild(snowflake);
+ }
+
+ document.body.appendChild(snowfallContainer);
+}
+
+window.addEventListener('load', createSnowfall);
diff --git a/test/pleroma/web/plugs/uploaded_media_plug_test.exs b/test/pleroma/web/plugs/uploaded_media_plug_test.exs
index 8323ff6ab..6e9dade21 100644
--- a/test/pleroma/web/plugs/uploaded_media_plug_test.exs
+++ b/test/pleroma/web/plugs/uploaded_media_plug_test.exs
@@ -1,43 +1,72 @@
# Pleroma: A lightweight social networking server
# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.Plugs.UploadedMediaPlugTest do
use Pleroma.Web.ConnCase, async: true
alias Pleroma.Upload
defp upload_file(context) do
Pleroma.DataCase.ensure_local_uploader(context)
File.cp!("test/fixtures/image.jpg", "test/fixtures/image_tmp.jpg")
file = %Plug.Upload{
content_type: "image/jpeg",
path: Path.absname("test/fixtures/image_tmp.jpg"),
filename: "nice_tf.jpg"
}
{:ok, data} = Upload.store(file)
[%{"href" => attachment_url} | _] = data["url"]
[attachment_url: attachment_url]
end
setup_all :upload_file
test "does not send Content-Disposition header when name param is not set", %{
attachment_url: attachment_url
} do
conn = get(build_conn(), attachment_url)
refute Enum.any?(conn.resp_headers, &(elem(&1, 0) == "content-disposition"))
end
test "sends Content-Disposition header when name param is set", %{
attachment_url: attachment_url
} do
conn = get(build_conn(), attachment_url <> ~s[?name="cofe".gif])
assert Enum.any?(
conn.resp_headers,
&(&1 == {"content-disposition", ~s[inline; filename="\\"cofe\\".gif"]})
)
end
+
+ test "Filters out dangerous content types" do
+ context = %{module: __MODULE__, case: __MODULE__}
+
+ test_files = [
+ "test/fixtures/lain.xml",
+ "test/fixtures/nypd-facial-recognition-children-teenagers.html",
+ "test/fixtures/snow.js"
+ ]
+
+ Enum.each(test_files, fn t ->
+ Pleroma.DataCase.ensure_local_uploader(context)
+ filename = String.split(t, "/") |> List.last()
+
+ upload = %Plug.Upload{
+ path: Path.absname(t),
+ filename: filename
+ }
+
+ {:ok, %{"url" => [%{"href" => attachment_url}]}} = Upload.store(upload)
+
+ conn = get(build_conn(), attachment_url)
+
+ assert Enum.any?(
+ conn.resp_headers,
+ &(&1 == {"content-type", "text/plain"})
+ )
+ end)
+ end
end

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