sharing cookies between rails 3 and rails 4.1

Question

I am trying to have shared cookies between Rails 3 and Rails 4.1 apps. The problem is that the Rails 3 cookies are just base64 encoded, but the Rails 4.1 cookies are encrypted. Is there any way to make both Rails 3 and Rails 4.1 make to use compatible cookies? For now the most easy way seems to downgrade to Rails 4.0

Accepted Answer

To get this working unset `secret_key_base` and instead use the same `secret_token` that you use in your Rails 3 app. Then the trick is to also set `action_dispatch.cookies_serializer = :marshal`. Otherwise Rails 4 stored the cookie in a format Rails 3 cannot read.

So my final config/initializers/session_store.rb has

```
Rails.application.config.action_dispatch.cookies_serializer = :marshal
Rails.application.config.secret_token = 'verylongstring'
```

sharing cookies between rails 3 and rails 4.1

Solution

Problem