Update

lib/nulla/httpsignature.ex

@@ -1,5 +1,70 @@
 defmodule Nulla.HTTPSignature do
-  def verify(_conn, _actor) do
+  import Plug.Conn
+
+  def verify(conn, actor_json) do
+    with [sig_header] <- get_req_header(conn, "signature"),
+         signature_map <- parse_signature_header(sig_header),
+         {:ok, signed_string} <- build_signature_string(signature_map["headers"], conn),
+         {:ok, public_key_pem} <- extract_public_key(actor_json),
+         true <- verify_signature(public_key_pem, signed_string, signature_map["signature"]) do
       :ok
+    else
+      _ -> {:error, :invalid_signature}
+    end
+  end
+
+  defp parse_signature_header(header) do
+    header
+    |> String.split(",")
+    |> Enum.map(fn pair ->
+      [k, v] = String.split(pair, "=", parts: 2)
+      {String.trim(k), String.trim(v, ~s("))}
+    end)
+    |> Enum.into(%{})
+  end
+
+  defp build_signature_string(nil, _conn), do: {:error, :missing_headers}
+
+  defp build_signature_string(headers_str, conn) do
+    headers = String.split(headers_str, " ")
+
+    result =
+      Enum.map(headers, fn header ->
+        line =
+          case header do
+            "(request-target)" ->
+              method = String.downcase(conn.method)
+
+              path =
+                conn.request_path <>
+                  if conn.query_string != "", do: "?" <> conn.query_string, else: ""
+
+              "(request-target): #{method} #{path}"
+
+            _ ->
+              value = get_req_header(conn, header) |> List.first()
+              if value, do: "#{header}: #{value}", else: nil
+          end
+
+        line
+      end)
+      |> Enum.reject(&is_nil/1)
+      |> Enum.join("\n")
+
+    {:ok, result}
+  end
+
+  defp extract_public_key(%{"publicKey" => %{"publicKeyPem" => pem}}), do: {:ok, pem}
+  defp extract_public_key(_), do: {:error, :no_public_key}
+
+  defp verify_signature(public_key_pem, signed_string, signature_base64) do
+    public_key =
+      :public_key.pem_decode(public_key_pem)
+      |> hd()
+      |> :public_key.pem_entry_decode()
+
+    signature = Base.decode64!(signature_base64)
+
+    :public_key.verify(signed_string, :sha256, signature, public_key)
   end
 end

lib/nulla/models/actor.ex

@@ -138,7 +138,7 @@ defmodule Nulla.Models.Actor do
     |> Repo.insert()
   end
 
-  def get_actor(username, domain) do
-    Repo.get_by(__MODULE__, preferredUsername: username, domain: domain)
+  def get_actor(by) when is_map(by) or is_list(by) do
+    Repo.get_by(__MODULE__, by)
   end
 end

lib/nulla/models/user.ex

@@ -3,7 +3,6 @@ defmodule Nulla.Models.User do
   import Ecto.Changeset
   import Ecto.Query
   alias Nulla.Repo
-  alias Nulla.Models.User
   alias Nulla.Models.Session
 
   @primary_key {:id, :integer, autogenerate: false}
@@ -44,17 +43,17 @@ defmodule Nulla.Models.User do
   end
 
   def get_user(by) when is_map(by) or is_list(by) do
-    Repo.get_by(User, by)
+    Repo.get_by(__MODULE__, by)
   end
 
   def get_total_users_count() do
-    Repo.aggregate(from(u in User), :count, :id)
+    Repo.aggregate(from(u in __MODULE__), :count, :id)
   end
 
   def get_active_users_count(days) do
     cutoff = DateTime.add(DateTime.utc_now(), -days * 86400, :second)
 
-    from(u in User, where: u.last_active_at > ^cutoff)
+    from(u in __MODULE__, where: u.last_active_at > ^cutoff)
     |> Repo.aggregate(:count, :id)
   end
 

lib/nulla/utils.ex

@@ -1,28 +1,12 @@
 defmodule Nulla.Utils do
-  alias Nulla.Models.Actor
-  alias Nulla.Models.InstanceSettings
-
-  def resolve_local_actor("https://" <> _ = uri) do
-    case URI.parse(uri).path do
-      "/@" <> username ->
-        instance_settings = InstanceSettings.get_instance_settings!()
-        domain = instance_settings.domain
-
-        case Actor.get_actor(username, domain) do
-          nil -> {:error, :not_found}
-          user -> user
-        end
-
-      _ ->
-        {:error, :invalid_actor}
-    end
-  end
-
   def fetch_remote_actor(uri) do
-    request =
-      Finch.build(:get, uri, [
-        {"Accept", "application/activity+json"}
-      ])
+    headers = [
+      {"Accept", "application/activity+json"},
+      {"User-Agent", "Nulla/1.0"},
+      {"Host", URI.parse(uri).host}
+    ]
+
+    request = Finch.build(:get, uri, headers)
 
     case Finch.request(request, Finch) do
       {:ok, %Finch.Response{status: 200, body: body}} ->
@@ -31,6 +15,9 @@ defmodule Nulla.Utils do
           _ -> {:error, :invalid_json}
         end
 
+      {:ok, %Finch.Response{status: code}} when code in 300..399 ->
+        {:error, :redirect_not_followed}
+
       _ ->
         {:error, :actor_fetch_failed}
     end

lib/nulla_web/controllers/actor_controller.ex

@@ -10,7 +10,7 @@ defmodule NullaWeb.ActorController do
     instance_settings = InstanceSettings.get_instance_settings!()
     domain = instance_settings.domain
 
-    case Actor.get_actor(username, domain) do
+    case Actor.get_actor(preferredUsername: username, domain: domain) do
       nil ->
         conn
         |> put_status(:not_found)

lib/nulla_web/controllers/follow_controller.ex

@@ -9,7 +9,7 @@ defmodule NullaWeb.FollowController do
     instance_settings = InstanceSettings.get_instance_settings!()
     domain = instance_settings.domain
     limit = instance_settings.api_limit
-    actor = Actor.get_actor(username, domain)
+    actor = Actor.get_actor(preferredUsername: username, domain: domain)
     total = Relation.count_following(actor.id)
 
     page =
@@ -28,7 +28,7 @@ defmodule NullaWeb.FollowController do
   def following(conn, %{"username" => username}) do
     instance_settings = InstanceSettings.get_instance_settings!()
     domain = instance_settings.domain
-    actor = Actor.get_actor(username, domain)
+    actor = Actor.get_actor(preferredUsername: username, domain: domain)
     total = Relation.count_following(actor.id)
 
     conn
@@ -40,7 +40,7 @@ defmodule NullaWeb.FollowController do
     instance_settings = InstanceSettings.get_instance_settings!()
     domain = instance_settings.domain
     limit = instance_settings.api_limit
-    actor = Actor.get_actor(username, domain)
+    actor = Actor.get_actor(preferredUsername: username, domain: domain)
     total = Relation.count_followers(actor.id)
 
     page =
@@ -59,7 +59,7 @@ defmodule NullaWeb.FollowController do
   def followers(conn, %{"username" => username}) do
     instance_settings = InstanceSettings.get_instance_settings!()
     domain = instance_settings.domain
-    actor = Actor.get_actor(username, domain)
+    actor = Actor.get_actor(preferredUsername: username, domain: domain)
     total = Relation.count_followers(actor.id)
 
     conn

lib/nulla_web/controllers/inbox_controller.ex

@@ -11,7 +11,7 @@ defmodule NullaWeb.InboxController do
         conn,
         %{"id" => follow_id, "type" => "Follow", "actor" => actor_uri, "object" => target_uri}
       ) do
-    with {:ok, local_actor} <- Utils.resolve_local_actor(target_uri),
+    with local_actor <- Actor.get_actor(ap_id: target_uri),
          {:ok, remote_actor_json} <- Utils.fetch_remote_actor(actor_uri),
          :ok <- HTTPSignature.verify(conn, remote_actor_json),
          remote_actor <-
@@ -31,7 +31,7 @@ defmodule NullaWeb.InboxController do
          accept_activity <-
            Activity.create_activity(%{
              type: "Accept",
-             actor: local_actor.id,
+             actor: local_actor.ap_id,
              object: follow_activity
            }),
          _ <-

lib/nulla_web/controllers/outbox_controller.ex

@@ -10,7 +10,7 @@ defmodule NullaWeb.OutboxController do
       "true" ->
         instance_settings = InstanceSettings.get_instance_settings!()
         domain = instance_settings.domain
-        actor = Actor.get_actor(username, domain)
+        actor = Actor.get_actor(preferredUsername: username, domain: domain)
         max_id = params["max_id"] && String.to_integer(params["max_id"])
 
         notes =
@@ -44,7 +44,7 @@ defmodule NullaWeb.OutboxController do
       _ ->
         instance_settings = InstanceSettings.get_instance_settings!()
         domain = instance_settings.domain
-        actor = Actor.get_actor(username, domain)
+        actor = Actor.get_actor(preferredUsername: username, domain: domain)
         total = Note.get_total_notes_count(actor.id)
 
         conn

lib/nulla_web/controllers/webfinger_controller.ex

@@ -7,7 +7,7 @@ defmodule NullaWeb.WebfingerController do
   def index(conn, %{"resource" => resource}) do
     case Regex.run(~r/^acct:(.+)@(.+)$/, resource) do
       [_, username, domain] ->
-        case Actor.get_actor(username, domain) do
+        case Actor.get_actor(preferredUsername: username, domain: domain) do
           nil ->
             conn
             |> put_resp_content_type("text/plain")