Merge branch 'fix/mediaproxy-bypass-emoji' into 'develop'

Fix profile emojis bypassing mediaproxy and harden CSP

Closes #1810

See merge request pleroma/pleroma!2596

lib/pleroma/plugs/http_security_plug.ex

@@ -31,7 +31,7 @@ defp headers do
       {"x-content-type-options", "nosniff"},
       {"referrer-policy", referrer_policy},
       {"x-download-options", "noopen"},
-      {"content-security-policy", csp_string() <> ";"}
+      {"content-security-policy", csp_string()}
     ]
 
     if report_uri do
@@ -43,23 +43,46 @@ defp headers do
         ]
       }
 
-      headers ++ [{"reply-to", Jason.encode!(report_group)}]
+      [{"reply-to", Jason.encode!(report_group)} | headers]
     else
       headers
     end
   end
 
+  static_csp_rules = [
+    "default-src 'none'",
+    "base-uri 'self'",
+    "frame-ancestors 'none'",
+    "style-src 'self' 'unsafe-inline'",
+    "font-src 'self'",
+    "manifest-src 'self'"
+  ]
+
+  @csp_start [Enum.join(static_csp_rules, ";") <> ";"]
+
   defp csp_string do
     scheme = Config.get([Pleroma.Web.Endpoint, :url])[:scheme]
     static_url = Pleroma.Web.Endpoint.static_url()
     websocket_url = Pleroma.Web.Endpoint.websocket_url()
     report_uri = Config.get([:http_security, :report_uri])
 
-    connect_src = "connect-src 'self' #{static_url} #{websocket_url}"
+    img_src = "img-src 'self' data: blob:"
+    media_src = "media-src 'self'"
+
+    {img_src, media_src} =
+      if Config.get([:media_proxy, :enabled]) &&
+           !Config.get([:media_proxy, :proxy_opts, :redirect_on_failure]) do
+        sources = get_proxy_and_attachment_sources()
+        {[img_src, sources], [media_src, sources]}
+      else
+        {img_src, media_src}
+      end
+
+    connect_src = ["connect-src 'self' ", static_url, ?\s, websocket_url]
 
     connect_src =
       if Pleroma.Config.get(:env) == :dev do
-        connect_src <> " http://localhost:3035/"
+        [connect_src, " http://localhost:3035/"]
       else
         connect_src
       end
@@ -71,27 +94,46 @@ defp csp_string do
         "script-src 'self'"
       end
 
-    main_part = [
-      "default-src 'none'",
-      "base-uri 'self'",
-      "frame-ancestors 'none'",
-      "img-src 'self' data: blob: https:",
-      "media-src 'self' https:",
-      "style-src 'self' 'unsafe-inline'",
-      "font-src 'self'",
-      "manifest-src 'self'",
-      connect_src,
-      script_src
-    ]
+    report = if report_uri, do: ["report-uri ", report_uri, ";report-to csp-endpoint"]
+    insecure = if scheme == "https", do: "upgrade-insecure-requests"
 
-    report = if report_uri, do: ["report-uri #{report_uri}; report-to csp-endpoint"], else: []
-
-    insecure = if scheme == "https", do: ["upgrade-insecure-requests"], else: []
-
-    (main_part ++ report ++ insecure)
-    |> Enum.join("; ")
+    @csp_start
+    |> add_csp_param(img_src)
+    |> add_csp_param(media_src)
+    |> add_csp_param(connect_src)
+    |> add_csp_param(script_src)
+    |> add_csp_param(insecure)
+    |> add_csp_param(report)
+    |> :erlang.iolist_to_binary()
   end
 
+  defp get_proxy_and_attachment_sources do
+    media_proxy_whitelist =
+      Enum.reduce(Config.get([:media_proxy, :whitelist]), [], fn host, acc ->
+        add_source(acc, host)
+      end)
+
+    upload_base_url =
+      if Config.get([Pleroma.Upload, :base_url]),
+        do: URI.parse(Config.get([Pleroma.Upload, :base_url])).host
+
+    s3_endpoint =
+      if Config.get([Pleroma.Upload, :uploader]) == Pleroma.Uploaders.S3,
+        do: URI.parse(Config.get([Pleroma.Uploaders.S3, :public_endpoint])).host
+
+    []
+    |> add_source(upload_base_url)
+    |> add_source(s3_endpoint)
+    |> add_source(media_proxy_whitelist)
+  end
+
+  defp add_source(iodata, nil), do: iodata
+  defp add_source(iodata, source), do: [[?\s, source] | iodata]
+
+  defp add_csp_param(csp_iodata, nil), do: csp_iodata
+
+  defp add_csp_param(csp_iodata, param), do: [[param, ?;] | csp_iodata]
+
   def warn_if_disabled do
     unless Config.get([:http_security, :enabled]) do
       Logger.warn("

lib/pleroma/web/mastodon_api/views/account_view.ex

@@ -182,12 +182,14 @@ defp do_render("show.json", %{user: user} = opts) do
     bot = user.actor_type in ["Application", "Service"]
 
     emojis =
-      Enum.map(user.emoji, fn {shortcode, url} ->
+      Enum.map(user.emoji, fn {shortcode, raw_url} ->
+        url = MediaProxy.url(raw_url)
+
         %{
-          "shortcode" => shortcode,
-          "url" => url,
-          "static_url" => url,
-          "visible_in_picker" => false
+          shortcode: shortcode,
+          url: url,
+          static_url: url,
+          visible_in_picker: false
         }
       end)
 

test/plugs/http_security_plug_test.exs

@@ -67,7 +67,7 @@ test "it sends `report-to` & `report-uri` CSP response headers" do
 
       [csp] = Conn.get_resp_header(conn, "content-security-policy")
 
-      assert csp =~ ~r|report-uri https://endpoint.com; report-to csp-endpoint;|
+      assert csp =~ ~r|report-uri https://endpoint.com;report-to csp-endpoint;|
 
       [reply_to] = Conn.get_resp_header(conn, "reply-to")
 

test/web/mastodon_api/views/account_view_test.exs

@@ -54,10 +54,10 @@ test "Represent a user account" do
       header_static: "http://localhost:4001/images/banner.png",
       emojis: [
         %{
-          "static_url" => "/file.png",
-          "url" => "/file.png",
-          "shortcode" => "karjalanpiirakka",
-          "visible_in_picker" => false
+          static_url: "/file.png",
+          url: "/file.png",
+          shortcode: "karjalanpiirakka",
+          visible_in_picker: false
         }
       ],
       fields: [],
@@ -491,4 +491,31 @@ test "shows non-zero when historical unapproved requests are present" do
                AccountView.render("show.json", %{user: user, for: user})
     end
   end
+
+  test "uses mediaproxy urls when it's enabled" do
+    clear_config([:media_proxy, :enabled], true)
+
+    user =
+      insert(:user,
+        avatar: %{"url" => [%{"href" => "https://evil.website/avatar.png"}]},
+        banner: %{"url" => [%{"href" => "https://evil.website/banner.png"}]},
+        emoji: %{"joker_smile" => "https://evil.website/society.png"}
+      )
+
+    AccountView.render("show.json", %{user: user})
+    |> Enum.all?(fn
+      {key, url} when key in [:avatar, :avatar_static, :header, :header_static] ->
+        String.starts_with?(url, Pleroma.Web.base_url())
+
+      {:emojis, emojis} ->
+        Enum.all?(emojis, fn %{url: url, static_url: static_url} ->
+          String.starts_with?(url, Pleroma.Web.base_url()) &&
+            String.starts_with?(static_url, Pleroma.Web.base_url())
+        end)
+
+      _ ->
+        true
+    end)
+    |> assert()
+  end
 end

test/web/media_proxy/media_proxy_test.exs

@@ -124,15 +124,7 @@ test "encoded url are tried to match for proxy as `conn.request_path` encodes th
     end
 
     test "uses the configured base_url" do
-      base_url = Pleroma.Config.get([:media_proxy, :base_url])
-
-      if base_url do
-        on_exit(fn ->
-          Pleroma.Config.put([:media_proxy, :base_url], base_url)
-        end)
-      end
-
-      Pleroma.Config.put([:media_proxy, :base_url], "https://cache.pleroma.social")
+      clear_config([:media_proxy, :base_url], "https://cache.pleroma.social")
 
       url = "https://pleroma.soykaf.com/static/logo.png"
       encoded = url(url)
@@ -213,8 +205,8 @@ test "mediaproxy whitelist" do
     end
 
     test "does not change whitelisted urls" do
-      Pleroma.Config.put([:media_proxy, :whitelist], ["mycdn.akamai.com"])
-      Pleroma.Config.put([:media_proxy, :base_url], "https://cache.pleroma.social")
+      clear_config([:media_proxy, :whitelist], ["mycdn.akamai.com"])
+      clear_config([:media_proxy, :base_url], "https://cache.pleroma.social")
 
       media_url = "https://mycdn.akamai.com"