ActivityPub: Basic note federation with Mastodon.

lib/pleroma/web/http_signatures/http_signatures.ex

@@ -1,6 +1,7 @@
 # https://tools.ietf.org/html/draft-cavage-http-signatures-08
 defmodule Pleroma.Web.HTTPSignatures do
   alias Pleroma.User
+  alias Pleroma.Web.ActivityPub.ActivityPub
 
   def split_signature(sig) do
     default = %{"headers" => "date"}
@@ -28,7 +29,16 @@ defmodule Pleroma.Web.HTTPSignatures do
     # For now, fetch the key for the actor.
     with actor_id <- conn.params["actor"],
          {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
-      validate_conn(conn, public_key)
+      if validate_conn(conn, public_key) do
+        true
+      else
+        # Fetch user anew and try one more time
+        with actor_id <- conn.params["actor"],
+             {:ok, _user} <- ActivityPub.make_user_from_ap_id(actor_id),
+             {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
+          validate_conn(conn, public_key)
+        end
+      end
     else
       _ -> false
     end
@@ -45,4 +55,22 @@ defmodule Pleroma.Web.HTTPSignatures do
     |> Enum.map(fn (header) -> "#{header}: #{headers[header]}" end)
     |> Enum.join("\n")
   end
+
+  def sign(user, headers) do
+    with {:ok, %{info: %{"keys" => keys}}} <- Pleroma.Web.WebFinger.ensure_keys_present(user),
+         {:ok, private_key, _} = Pleroma.Web.Salmon.keys_from_pem(keys) do
+      sigstring = build_signing_string(headers, Map.keys(headers))
+      signature = :public_key.sign(sigstring, :sha256, private_key)
+      |> Base.encode64()
+
+      [
+        keyId: user.ap_id <> "#main-key",
+        algorithm: "rsa-sha256",
+        headers: Map.keys(headers) |> Enum.join(" "),
+        signature: signature
+      ]
+      |> Enum.map(fn({k, v}) -> "#{k}=\"#{v}\"" end)
+      |> Enum.join(",")
+    end
+  end
 end