HTTPSignaturePlug: Add :authorized_fetch_mode_exceptions

changelog.d/auth-fetch-exception.add

@@ -0,0 +1 @@
+HTTPSignaturePlug: Add :authorized_fetch_mode_exceptions configuration

config/description.exs

@@ -1771,6 +1771,12 @@
         type: :boolean,
         description: "Require HTTP signatures for AP fetches"
       },
+      %{
+        key: :authorized_fetch_mode_exceptions,
+        type: {:list, :string},
+        description:
+          "List of IPs (CIDR format accepted) to exempt from HTTP Signatures requirement (for example to allow debugging, you shouldn't otherwise need this)"
+      },
       %{
         key: :note_replies_output_limit,
         type: :integer,

docs/configuration/cheatsheet.md

@@ -279,6 +279,7 @@ Notes:
 * `deny_follow_blocked`: Whether to disallow following an account that has blocked the user in question
 * `sign_object_fetches`: Sign object fetches with HTTP signatures
 * `authorized_fetch_mode`: Require HTTP signatures for AP fetches
+* `authorized_fetch_mode_exceptions`: List of IPs (CIDR format accepted) to exempt from HTTP Signatures requirement (for example to allow debugging, you shouldn't otherwise need this)
 
 ## Pleroma.User
 

lib/pleroma/web/plugs/http_signature_plug.ex

@@ -3,6 +3,8 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.Plugs.HTTPSignaturePlug do
+  alias Pleroma.Helpers.InetHelper
+
   import Plug.Conn
   import Phoenix.Controller, only: [get_format: 1, text: 2]
   require Logger
@@ -89,12 +91,20 @@ defp has_signature_header?(conn) do
 
   defp maybe_require_signature(%{assigns: %{valid_signature: true}} = conn), do: conn
 
-  defp maybe_require_signature(conn) do
+  defp maybe_require_signature(%{remote_ip: remote_ip} = conn) do
     if Pleroma.Config.get([:activitypub, :authorized_fetch_mode], false) do
+      exceptions =
+        Pleroma.Config.get([:activitypub, :authorized_fetch_mode_exceptions], [])
+        |> Enum.map(&InetHelper.parse_cidr/1)
+
+      if Enum.any?(exceptions, fn x -> InetCidr.contains?(x, remote_ip) end) do
+        conn
+      else
         conn
         |> put_status(:unauthorized)
         |> text("Request not signed")
         |> halt()
+      end
     else
       conn
     end

test/pleroma/web/plugs/http_signature_plug_test.exs

@@ -81,5 +81,24 @@ test "halts the connection when `signature` header is not present", %{conn: conn
       assert conn.state == :sent
       assert conn.resp_body == "Request not signed"
     end
+
+    test "exempts specific IPs from `authorized_fetch_mode_exceptions`", %{conn: conn} do
+      clear_config([:activitypub, :authorized_fetch_mode_exceptions], ["192.168.0.0/24"])
+
+      with_mock HTTPSignatures, validate_conn: fn _ -> false end do
+        conn =
+          conn
+          |> Map.put(:remote_ip, {192, 168, 0, 1})
+          |> put_req_header(
+            "signature",
+            "keyId=\"http://mastodon.example.org/users/admin#main-key"
+          )
+          |> HTTPSignaturePlug.call(%{})
+
+        assert conn.remote_ip == {192, 168, 0, 1}
+        assert conn.halted == false
+        assert called(HTTPSignatures.validate_conn(:_))
+      end
+    end
   end
 end