[Bugfix] Improve OPML route security (#535)

* WIP - moved plugs; set up a new token-protected route plug

* Added a route_token column to settings model

* Hooked up token_protected_route plug to database

* Hooked up new OPML route to UI; turned RSS and OPML feed buttons into links

* Docs, tests

* Added a note about the phoenix bug

Author: kieraneglin

lib/pinchflat/settings/setting.ex

@@ -31,6 +31,7 @@ defmodule Pinchflat.Settings.Setting do
     field :apprise_version, :string
     field :apprise_server, :string
     field :youtube_api_key, :string
+    field :route_token, :string
 
     field :video_codec_preference, :string
     field :audio_codec_preference, :string

lib/pinchflat_web/controllers/sources/source_html.ex

@@ -40,11 +40,13 @@ defmodule PinchflatWeb.Sources.SourceHTML do
   end
 
   def rss_feed_url(conn, source) do
+    # NOTE: The reason for this concatenation is to avoid what appears to be a bug in Phoenix
+    # See: https://github.com/phoenixframework/phoenix/issues/6033
     url(conn, ~p"/sources/#{source.uuid}/feed") <> ".xml"
   end
 
   def opml_feed_url(conn) do
-    url(conn, ~p"/sources/opml") <> ".xml"
+    url(conn, ~p"/sources/opml.xml?#{[route_token: Settings.get!(:route_token)]}")
   end
 
   def output_path_template_override_placeholders(media_profiles) do

lib/pinchflat_web/controllers/sources/source_html/actions_dropdown.html.heex

@@ -1,18 +1,16 @@
 <.button_dropdown text="Actions" class="justify-center w-full sm:w-50">
   <:option>
-    <span
-      x-data="{ copied: false }"
-      x-on:click={"
-        copyWithCallbacks(
-          '#{rss_feed_url(@conn, @source)}', 
-          () => copied = true, 
-          () => copied = false
-        )
-      "}
-    >
+    <.link href={rss_feed_url(@conn, @source)} x-data="{ copied: false }" x-on:click={~s"
+          $event.preventDefault();
+          copyWithCallbacks(
+            '#{rss_feed_url(@conn, @source)}',
+            () => copied = true,
+            () => copied = false
+          )
+        "}>
       Copy RSS Feed
       <span x-show="copied" x-transition.duration.150ms><.icon name="hero-check" class="ml-2 h-4 w-4" /></span>
-    </span>
+    </.link>
   </:option>
   <:option>
     <span x-data="{ copied: false }" x-on:click={~s"

lib/pinchflat_web/controllers/sources/source_html/index.html.heex

@@ -1,16 +1,17 @@
 <div class="mb-6 flex gap-3 flex-row items-center justify-between">
   <h2 class="text-title-md2 font-bold text-black dark:text-white">Sources</h2>
-  <nav>
-    <.button color="bg-transparent" x-data="{ copied: false }" x-on:click={~s"
+  <nav class="flex items-center justify-between gap-6">
+    <.link href={opml_feed_url(@conn)} x-data="{ copied: false }" x-on:click={~s"
+          $event.preventDefault();
           copyWithCallbacks(
             '#{opml_feed_url(@conn)}',
             () => copied = true,
             () => copied = false
           )
         "}>
-      Copy OPML Feed
+      Copy OPML <span class="hidden sm:inline">Feed</span>
       <span x-show="copied" x-transition.duration.150ms><.icon name="hero-check" class="ml-2 h-4 w-4" /></span>
-    </.button>
+    </.link>
     <.link href={~p"/sources/new"}>
       <.button color="bg-primary" rounding="rounded-lg">
         <span class="font-bold mx-2">+</span> New <span class="hidden sm:inline pl-1">Source</span>

lib/pinchflat_web/endpoint.ex

@@ -73,6 +73,13 @@ defmodule PinchflatWeb.Endpoint do
     Phoenix.Controller.put_router_url(conn, new_base_url)
   end
 
+  # Some podcast clients require file extensions, and others still will _add_
+  # file extensions to XML files if they don't have them. This plug removes
+  # the extension from the path so that the correct route is matched, regardless
+  # of the provided extension.
+  #
+  # This has the downside of in-app generated verified routes not working with
+  # extensions so this behaviour may change in the future.
   defp strip_trailing_extension(%{path_info: []} = conn, _opts), do: conn
 
   defp strip_trailing_extension(conn, _opts) do

lib/pinchflat_web/plugs.ex

@@ -0,0 +1,66 @@
+defmodule PinchflatWeb.Plugs do
+  @moduledoc """
+  Custom plugs for PinchflatWeb.
+  """
+
+  use PinchflatWeb, :router
+  alias Pinchflat.Settings
+
+  @doc """
+  If the `expose_feed_endpoints` setting is true, this plug does nothing. Otherwise, it calls `basic_auth/2`.
+  """
+  def maybe_basic_auth(conn, opts) do
+    if Application.get_env(:pinchflat, :expose_feed_endpoints) do
+      conn
+    else
+      basic_auth(conn, opts)
+    end
+  end
+
+  @doc """
+  If the `basic_auth_username` and `basic_auth_password` settings are set, this plug calls `Plug.BasicAuth.basic_auth/3`.
+  """
+  def basic_auth(conn, _opts) do
+    username = Application.get_env(:pinchflat, :basic_auth_username)
+    password = Application.get_env(:pinchflat, :basic_auth_password)
+
+    if credential_set?(username) && credential_set?(password) do
+      Plug.BasicAuth.basic_auth(conn, username: username, password: password, realm: "Pinchflat")
+    else
+      conn
+    end
+  end
+
+  @doc """
+  Removes the `x-frame-options` header from the response to allow the page to be embedded in an iframe.
+  """
+  def allow_iframe_embed(conn, _opts) do
+    delete_resp_header(conn, "x-frame-options")
+  end
+
+  @doc """
+  If the `route_token` query parameter matches the `route_token` setting, this plug does nothing.
+  Otherwise, it sends a 401 response.
+  """
+  def token_protected_route(%{query_params: %{"route_token" => route_token}} = conn, _opts) do
+    if Settings.get!(:route_token) == route_token do
+      conn
+    else
+      send_unauthorized(conn)
+    end
+  end
+
+  def token_protected_route(conn, _opts) do
+    send_unauthorized(conn)
+  end
+
+  defp credential_set?(credential) do
+    credential && credential != ""
+  end
+
+  defp send_unauthorized(conn) do
+    conn
+    |> send_resp(:unauthorized, "Unauthorized")
+    |> halt()
+  end
+end

lib/pinchflat_web/router.ex

@@ -1,5 +1,6 @@
 defmodule PinchflatWeb.Router do
   use PinchflatWeb, :router
+  import PinchflatWeb.Plugs
   import Phoenix.LiveDashboard.Router
 
   # IMPORTANT: `strip_trailing_extension` in endpoint.ex removes
@@ -19,16 +20,18 @@ defmodule PinchflatWeb.Router do
     plug :accepts, ["json"]
   end
 
-  pipeline :feeds do
-    plug :maybe_basic_auth
+  scope "/", PinchflatWeb do
+    pipe_through [:maybe_basic_auth, :token_protected_route]
+
+    # has to match before /sources/:id
+    get "/sources/opml", Podcasts.PodcastController, :opml_feed
+    get "/sources/:foo/opml", Podcasts.PodcastController, :opml_feed
   end
 
   # Routes in here _may not be_ protected by basic auth. This is necessary for
   # media streaming to work for RSS podcast feeds.
   scope "/", PinchflatWeb do
-    pipe_through :feeds
-    # has to match before /sources/:id
-    get "/sources/opml", Podcasts.PodcastController, :opml_feed
+    pipe_through :maybe_basic_auth
 
     get "/sources/:uuid/feed", Podcasts.PodcastController, :rss_feed
     get "/sources/:uuid/feed_image", Podcasts.PodcastController, :feed_image
@@ -76,31 +79,4 @@ defmodule PinchflatWeb.Router do
       metrics: PinchflatWeb.Telemetry,
       ecto_repos: [Pinchflat.Repo]
   end
-
-  defp maybe_basic_auth(conn, opts) do
-    if Application.get_env(:pinchflat, :expose_feed_endpoints) do
-      conn
-    else
-      basic_auth(conn, opts)
-    end
-  end
-
-  defp basic_auth(conn, _opts) do
-    username = Application.get_env(:pinchflat, :basic_auth_username)
-    password = Application.get_env(:pinchflat, :basic_auth_password)
-
-    if credential_set?(username) && credential_set?(password) do
-      Plug.BasicAuth.basic_auth(conn, username: username, password: password, realm: "Pinchflat")
-    else
-      conn
-    end
-  end
-
-  defp credential_set?(credential) do
-    credential && credential != ""
-  end
-
-  defp allow_iframe_embed(conn, _opts) do
-    delete_resp_header(conn, "x-frame-options")
-  end
 end

priv/repo/erd.png

@@ -0,0 +1,11 @@
+defmodule Pinchflat.Repo.Migrations.AddRouteTokenToSettings do
+  use Ecto.Migration
+
+  def change do
+    alter table(:settings) do
+      add :route_token, :string, null: false, default: "tmp-token"
+    end
+
+    execute "UPDATE settings SET route_token = gen_random_uuid();", "SELECT 1;"
+  end
+end

priv/repo/migrations/20241230192618_add_route_token_to_settings.exs

@@ -4,17 +4,34 @@ defmodule PinchflatWeb.PodcastControllerTest do
   import Pinchflat.MediaFixtures
   import Pinchflat.SourcesFixtures
 
+  alias Pinchflat.Settings
+
   describe "opml_feed" do
     test "renders the XML document", %{conn: conn} do
       source = source_fixture()
+      route_token = Settings.get!(:route_token)
 
-      conn = get(conn, ~p"/sources/opml" <> ".xml")
+      conn = get(conn, ~p"/sources/opml.xml?#{[route_token: route_token]}")
 
       assert conn.status == 200
       assert {"content-type", "application/opml+xml; charset=utf-8"} in conn.resp_headers
       assert {"content-disposition", "inline"} in conn.resp_headers
       assert conn.resp_body =~ ~s"http://www.example.com/sources/#{source.uuid}/feed.xml"
-      assert conn.resp_body =~ "text=\"Cool and good internal name!\""
+      assert conn.resp_body =~ "text=\"#{source.custom_name}\""
+    end
+
+    test "returns 401 if the route token is incorrect", %{conn: conn} do
+      conn = get(conn, ~p"/sources/opml.xml?route_token=incorrect")
+
+      assert conn.status == 401
+      assert conn.resp_body == "Unauthorized"
+    end
+
+    test "returns 401 if the route token is missing", %{conn: conn} do
+      conn = get(conn, ~p"/sources/opml.xml")
+
+      assert conn.status == 401
+      assert conn.resp_body == "Unauthorized"
     end
   end