Add Secure and SameSite cookie flags

config/config.exs

@@ -24,7 +24,8 @@ config :pleroma, Pleroma.Web.Endpoint,
   protocol: "https",
   secret_key_base: "aK4Abxf29xU9TTDKre9coZPUgevcVCFQJe/5xP/7Lt4BEif6idBIbjupVbOrbKxl",
   render_errors: [view: Pleroma.Web.ErrorView, accepts: ~w(json)],
-  pubsub: [name: Pleroma.PubSub, adapter: Phoenix.PubSub.PG2]
+  pubsub: [name: Pleroma.PubSub, adapter: Phoenix.PubSub.PG2],
+  secure_cookie_flag: true
 
 # Configures Elixir's Logger
 config :logger, :console,

lib/pleroma/web/endpoint.ex

@@ -49,7 +49,9 @@ defmodule Pleroma.Web.Endpoint do
     Plug.Session,
     store: :cookie,
     key: "_pleroma_key",
-    signing_salt: "CqaoopA2"
+    signing_salt: "CqaoopA2",
+    secure: Application.get_env(:pleroma, Pleroma.Web.Endpoint) |> Keyword.get(:secure_cookie_flag),
+    extra: "SameSite=Lax"
   )
 
   plug(Pleroma.Web.Router)