reuse valid oauth tokens (#182)

Reviewed-on: https://akkoma.dev/AkkomaGang/akkoma/pulls/182

lib/pleroma/helpers/auth_helper.ex

@@ -9,6 +9,7 @@ defmodule Pleroma.Helpers.AuthHelper do
   import Plug.Conn
 
   @oauth_token_session_key :oauth_token
+  @oauth_user_session_key :oauth_user
 
   @doc """
   Skips OAuth permissions (scopes) checks, assigns nil `:token`.
@@ -43,4 +44,16 @@ defmodule Pleroma.Helpers.AuthHelper do
   def delete_session_token(%Conn{} = conn) do
     delete_session(conn, @oauth_token_session_key)
   end
+
+  def put_session_user(%Conn{} = conn, user) do
+    put_session(conn, @oauth_user_session_key, user)
+  end
+
+  def delete_session_user(%Conn{} = conn) do
+    delete_session(conn, @oauth_user_session_key)
+  end
+
+  def get_session_user(%Conn{} = conn) do
+    get_session(conn, @oauth_user_session_key)
+  end
 end

lib/pleroma/web/mastodon_api/controllers/auth_controller.ex

@@ -27,7 +27,8 @@ defmodule Pleroma.Web.MastodonAPI.AuthController do
   def login(conn, %{"code" => auth_token} = params) do
     with {:ok, app} <- local_mastofe_app(),
          {:ok, auth} <- Authorization.get_by_token(app, auth_token),
-         {:ok, oauth_token} <- Token.exchange_token(app, auth) do
+         %User{} = user <- User.get_cached_by_id(auth.user_id),
+         {:ok, oauth_token} <- Token.get_or_exchange_token(auth, app, user) do
       redirect_to =
         conn
         |> local_mastodon_post_login_path()

lib/pleroma/web/o_auth/authorization.ex

@@ -94,4 +94,9 @@ defmodule Pleroma.Web.OAuth.Authorization do
     from(t in __MODULE__, where: t.app_id == ^app_id and t.token == ^token)
     |> Repo.find_resource()
   end
+
+  def get_preeexisting_by_app_and_user(%App{id: app_id} = _app, %User{id: user_id} = _user) do
+    from(t in __MODULE__, where: t.app_id == ^app_id and t.user_id == ^user_id, limit: 1)
+    |> Repo.find_resource()
+  end
 end

lib/pleroma/web/o_auth/o_auth_controller.ex

@@ -59,18 +59,39 @@ defmodule Pleroma.Web.OAuth.OAuthController do
   # after user already authorized to MastodonFE.
   # So we have to check client and token.
   def authorize(
-        %Plug.Conn{assigns: %{token: %Token{} = token}} = conn,
+        %Plug.Conn{assigns: %{token: %Token{} = token, user: %User{} = user}} = conn,
         %{"client_id" => client_id} = params
       ) do
     with %Token{} = t <- Repo.get_by(Token, token: token.token) |> Repo.preload(:app),
          ^client_id <- t.app.client_id do
       handle_existing_authorization(conn, params)
+    else
+      _ ->
+        maybe_reuse_token(conn, params, user.id)
+    end
+  end
+
+  def authorize(%Plug.Conn{} = conn, params) do
+    # if we have a user in the session, attempt to authenticate as them
+    # otherwise show the login form
+    maybe_reuse_token(conn, params, AuthHelper.get_session_user(conn))
+  end
+
+  defp maybe_reuse_token(conn, params, user_id) when is_binary(user_id) do
+    with %User{} = user <- User.get_cached_by_id(user_id),
+         %App{} = app <- Repo.get_by(App, client_id: params["client_id"]),
+         {:ok, %Token{} = token} <- Token.get_preeexisting_by_app_and_user(app, user),
+         {:ok, %Authorization{} = auth} <-
+           Authorization.get_preeexisting_by_app_and_user(app, user) do
+      conn
+      |> assign(:token, token)
+      |> after_create_authorization(auth, %{"authorization" => params})
     else
       _ -> do_authorize(conn, params)
     end
   end
 
-  def authorize(%Plug.Conn{} = conn, params), do: do_authorize(conn, params)
+  defp maybe_reuse_token(conn, params, _user), do: do_authorize(conn, params)
 
   defp do_authorize(%Plug.Conn{} = conn, params) do
     app = Repo.get_by(App, client_id: params["client_id"])
@@ -148,7 +169,9 @@ defmodule Pleroma.Web.OAuth.OAuthController do
   def create_authorization(%Plug.Conn{} = conn, %{"authorization" => _} = params, opts) do
     with {:ok, auth, user} <- do_create_authorization(conn, params, opts[:user]),
          {:mfa_required, _, _, false} <- {:mfa_required, user, auth, MFA.require?(user)} do
-      after_create_authorization(conn, auth, params)
+      conn
+      |> AuthHelper.put_session_user(user.id)
+      |> after_create_authorization(auth, params)
     else
       error ->
         handle_create_authorization_error(conn, error, params)
@@ -269,7 +292,7 @@ defmodule Pleroma.Web.OAuth.OAuthController do
          fixed_token = Token.Utils.fix_padding(params["code"]),
          {:ok, auth} <- Authorization.get_by_token(app, fixed_token),
          %User{} = user <- User.get_cached_by_id(auth.user_id),
-         {:ok, token} <- Token.exchange_token(app, auth) do
+         {:ok, token} <- Token.get_or_exchange_token(auth, app, user) do
       after_token_exchange(conn, %{user: user, token: token})
     else
       error ->
@@ -321,6 +344,7 @@ defmodule Pleroma.Web.OAuth.OAuthController do
   def after_token_exchange(%Plug.Conn{} = conn, %{token: token} = view_params) do
     conn
     |> AuthHelper.put_session_token(token.token)
+    |> AuthHelper.put_session_user(token.user_id)
     |> json(OAuthView.render("token.json", view_params))
   end
 

lib/pleroma/web/o_auth/token.ex

@@ -70,6 +70,16 @@ defmodule Pleroma.Web.OAuth.Token do
     end
   end
 
+  def get_preeexisting_by_app_and_user(app, user) do
+    Query.get_by_app(app.id)
+    |> Query.get_by_user(user.id)
+    |> Query.get_unexpired()
+    |> Query.preload([:user])
+    |> Query.sort_by_inserted_at()
+    |> Query.limit(1)
+    |> Repo.find_resource()
+  end
+
   defp put_token(changeset) do
     changeset
     |> change(%{token: Token.Utils.generate_token()})
@@ -86,6 +96,14 @@ defmodule Pleroma.Web.OAuth.Token do
     |> unique_constraint(:refresh_token)
   end
 
+  def get_or_exchange_token(%Authorization{} = auth, %App{} = app, %User{} = user) do
+    if auth.used do
+      get_preeexisting_by_app_and_user(app, user)
+    else
+      exchange_token(app, auth)
+    end
+  end
+
   defp put_valid_until(changeset, attrs) do
     valid_until =
       Map.get(attrs, :valid_until, NaiveDateTime.add(NaiveDateTime.utc_now(), lifespan()))

lib/pleroma/web/o_auth/token/query.ex

@@ -38,6 +38,19 @@ defmodule Pleroma.Web.OAuth.Token.Query do
     from(q in query, where: q.user_id == ^user_id)
   end
 
+  def get_unexpired(query) do
+    now = NaiveDateTime.utc_now()
+    from(q in query, where: q.valid_until > ^now)
+  end
+
+  def limit(query, limit) do
+    from(q in query, limit: ^limit)
+  end
+
+  def sort_by_inserted_at(query) do
+    from(q in query, order_by: [desc: :updated_at])
+  end
+
   @spec preload(query, any) :: query
   def preload(query \\ Token, assoc_preload \\ [])
 

test/pleroma/web/o_auth/o_auth_controller_test.exs

@@ -494,6 +494,129 @@ defmodule Pleroma.Web.OAuth.OAuthControllerTest do
       assert html_response(conn, 200) =~ ~s(type="submit")
     end
 
+    test "allows access if the user has a prior authorization but is authenticated with another client",
+         %{
+           app: app,
+           conn: conn
+         } do
+      user = insert(:user)
+      token = insert(:oauth_token, app: app, user: user)
+
+      other_app = insert(:oauth_app, redirect_uris: "https://other_redirect.url")
+      authorization = insert(:oauth_authorization, user: user, app: other_app)
+      _reusable_token = insert(:oauth_token, app: other_app, user: user)
+
+      conn =
+        conn
+        |> AuthHelper.put_session_token(token.token)
+        |> AuthHelper.put_session_user(user.id)
+        |> get(
+          "/oauth/authorize",
+          %{
+            "response_type" => "code",
+            "client_id" => other_app.client_id,
+            "redirect_uri" => OAuthController.default_redirect_uri(other_app),
+            "scope" => "read"
+          }
+        )
+
+      assert URI.decode(redirected_to(conn)) ==
+               "https://other_redirect.url?code=#{authorization.token}"
+    end
+
+    test "renders login page if the user has an authorization but no token",
+         %{
+           app: app,
+           conn: conn
+         } do
+      user = insert(:user)
+      token = insert(:oauth_token, app: app, user: user)
+
+      other_app = insert(:oauth_app, redirect_uris: "https://other_redirect.url")
+      _authorization = insert(:oauth_authorization, user: user, app: other_app)
+
+      conn =
+        conn
+        |> AuthHelper.put_session_token(token.token)
+        |> AuthHelper.put_session_user(user.id)
+        |> get(
+          "/oauth/authorize",
+          %{
+            "response_type" => "code",
+            "client_id" => other_app.client_id,
+            "redirect_uri" => OAuthController.default_redirect_uri(other_app),
+            "scope" => "read"
+          }
+        )
+
+      assert html_response(conn, 200) =~ ~s(type="submit")
+    end
+
+    test "does not reuse other people's tokens",
+         %{
+           app: app,
+           conn: conn
+         } do
+      user = insert(:user)
+      other_user = insert(:user)
+      token = insert(:oauth_token, app: app, user: user)
+
+      other_app = insert(:oauth_app, redirect_uris: "https://other_redirect.url")
+      _authorization = insert(:oauth_authorization, user: other_user, app: other_app)
+      _reusable_token = insert(:oauth_token, app: other_app, user: other_user)
+
+      conn =
+        conn
+        |> AuthHelper.put_session_token(token.token)
+        |> AuthHelper.put_session_user(user.id)
+        |> get(
+          "/oauth/authorize",
+          %{
+            "response_type" => "code",
+            "client_id" => other_app.client_id,
+            "redirect_uri" => OAuthController.default_redirect_uri(other_app),
+            "scope" => "read"
+          }
+        )
+
+      assert html_response(conn, 200) =~ ~s(type="submit")
+    end
+
+    test "does not reuse expired tokens",
+         %{
+           app: app,
+           conn: conn
+         } do
+      user = insert(:user)
+      token = insert(:oauth_token, app: app, user: user)
+
+      other_app = insert(:oauth_app, redirect_uris: "https://other_redirect.url")
+      _authorization = insert(:oauth_authorization, user: user, app: other_app)
+
+      _reusable_token =
+        insert(:oauth_token,
+          app: other_app,
+          user: user,
+          valid_until: NaiveDateTime.add(NaiveDateTime.utc_now(), -100)
+        )
+
+      conn =
+        conn
+        |> AuthHelper.put_session_token(token.token)
+        |> AuthHelper.put_session_user(user.id)
+        |> get(
+          "/oauth/authorize",
+          %{
+            "response_type" => "code",
+            "client_id" => other_app.client_id,
+            "redirect_uri" => OAuthController.default_redirect_uri(other_app),
+            "scope" => "read"
+          }
+        )
+
+      assert html_response(conn, 200) =~ ~s(type="submit")
+    end
+
     test "with existing authentication and non-OOB `redirect_uri`, redirects to app with `token` and `state` params",
          %{
            app: app,