OkHttp Cookies with domains that start with a dot

Question

Within a Xamarin app we are having a problem on Android where OkHttp is failing to send requests if they contain cookies where the domain starts with a dot.

Exception:     java.lang.IllegalArgumentException
Ex. Message:   unexpected domain: .direct.aviva.co.uk

Original stack trace:
======================
java.lang.IllegalArgumentException : unexpected domain: .my.domain.com
        at okhttp3.Cookie$Builder.domain(Cookie.kt:297)
        at okhttp3.Cookie$Builder.domain(Cookie.kt:287)

As far as I'm aware its valid for a domain to start with a dot but in the past this potentially wasn't allowed, is this correct? Could it be newer versions of OkHttp wouldn't throw this error?

We are using OkHttp 4.9.0.

Answer 1

If you’re constructing the cookie object programmatically, just omit the leading dot. That’s the rule according to the spec that OkHttp implements.

https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.3