Improve validation for token exchange endpoint

lib/comfycamp_web/controllers/oauth_controller.ex

@@ -4,7 +4,6 @@ defmodule ComfycampWeb.OauthController do
   alias Comfycamp.Accounts
   alias Comfycamp.SSO
   alias Comfycamp.SSO.OIDCApp
-  alias Comfycamp.SSO.OIDCCode
   alias Comfycamp.SSO.IDToken
   alias Comfycamp.Token
 
@@ -78,19 +77,13 @@ defmodule ComfycampWeb.OauthController do
   end
 
   def token(conn, params = %{"code" => code_value, "redirect_uri" => redirect_uri}) do
-    {:ok, client_id, client_secret} = get_client_info(conn, params)
-
-    # Check that code is still valid and redirect uri has not been altered.
-    %OIDCCode{redirect_uri: ^redirect_uri} = code = SSO.get_oidc_code!(code_value)
-
-    # Check that client provided a valid secret for an active OIDC app.
-    %OIDCApp{enabled: true, client_id: ^client_id} =
-      oidc_app = SSO.get_oidc_app_by_secret!(client_secret)
-
-    # Check that OIDC app is referenced by provided code.
-    ^client_id = code.oidc_app.client_id
-
-    # Delete the code.
+    with {:client_info, {:ok, client_id, client_secret}} <-
+           {:client_info, get_client_info(conn, params)},
+         {:code, code} <- {:code, SSO.get_oidc_code!(code_value)},
+         {:uri, ^redirect_uri} <- {:uri, code.redirect_uri},
+         {:app, oidc_app = %OIDCApp{enabled: true, client_id: ^client_id}} <-
+           {:app, SSO.get_oidc_app_by_secret!(client_secret)},
+         {:code_ref, ^client_id} <- {:code_ref, code.oidc_app.client_id} do
       SSO.delete_oidc_code(code)
 
       {access_token, refresh_token} = Accounts.generate_oauth_tokens(code.user)
@@ -103,6 +96,22 @@ defmodule ComfycampWeb.OauthController do
         refresh_token: Base.url_encode64(refresh_token),
         id_token: signed_id_token
       )
+    else
+      {:client_info, _} ->
+        render(conn, :error, description: "Нет client id или client secret")
+
+      {:code, _} ->
+        render(conn, :error, description: "Не удалось найти временный код")
+
+      {:uri, _} ->
+        render(conn, :error, description: "Redirect URI не совпадает с изначальным значением")
+
+      {:app, _} ->
+        render(conn, :error, description: "Приложение не найдено или отключено")
+
+      {:code_ref, _} ->
+        render(conn, :error, description: "Временный код выдан для другого приложения")
+    end
   end
 
   def openid_discovery(conn, _params) do

lib/comfycamp_web/controllers/oauth_json.ex

@@ -21,4 +21,10 @@ defmodule ComfycampWeb.OauthJSON do
       claims_supported: ["sub", "email", "preferred_username"]
     }
   end
+
+  def error(assigns) do
+    %{
+      description: assigns["description"]
+    }
+  end
 end