Re: [OAUTH-WG] expires_in

It does sound like a best practice and nearly all the providers I've ever
worked with do have an expiration for ATs, however there are
counterexamples (most notably, dropbox
<https://www.dropbox.com/developers/support#token-expiration>) and they
seem to be doing fine so far.
Do we know anyone on Dropbox that can comment on their use case and whether
they'd see value in changing their current behavior?

On Tue, Dec 18, 2018 at 1:42 AM Neil Madden <neil.madden@forgerock.com>
wrote:

> This is probably a best practice, but we should be careful to not oversell
> the benefits. Unless you measure token lifetime in a small number of
> seconds, then it’s doubtful that any realistic attack will be stopped by
> this. It’s mostly useful at defending against opportunistic attacks - e.g.
> a token accidentally gets logged, but the logs aren’t examined very often.
> Sender-constrained/PoP tokens, avoiding passing tokens in URL parameters,
> and so on are better defences against this kind of thing.
>
> There are two deployment scenarios when short-lived access token are
> essential though:
>
> 1. If you are employing the “self-contained RS” model (no introspection
> calls to the AS) and are using short-lived access tokens with a refresh
> token to force the client to check in with the AS periodically to allow
> token revocation. [1]
>
> 2. If you are using a blacklisting strategy to token revocation, in which
> case having a short token lifetime limits the amount of time you need to
> blacklist tokens for.
>
> On the other hand, is there ever a valid reason for having an access token
> be valid for 10 years or so?
>
> [1] https://www.ietf.org/mail-archive/web/oauth/current/msg06687.html
>
> — Neil
>
> > On 18 Dec 2018, at 08:55, Hannes Tschofenig <Hannes.Tschofenig@arm.com>
> wrote:
> >
> > Hi all,
> >
> > In a recent email conversation on the IETF ACE mailing list Ludwig Seitz
> suggested that the expires_in claim in an access token should actually be
> mandatory.
> > Intuitively it feels like access tokens shouldn't have an unrestricted
> lifetime. I am curious whether recommendations would be useful here.
> >
> > RFC 6819 talks about the expires_in claim and says:
> >
> > 3.1.2.  Limited Access Token Lifetime
> >
> >   The protocol parameter "expires_in" allows an authorization server
> >   (based on its policies or on behalf of the end user) to limit the
> >   lifetime of an access token and to pass this information to the
> >   client.  This mechanism can be used to issue short-lived tokens to
> >   OAuth clients that the authorization server deems less secure, or
> >   where sending tokens over non-secure channels.
> >
> > draft-ietf-oauth-security-topics-10 only talks about refresh token
> expiry.
> >
> > In OpenID Connect the expires_in claim is also optional.
> >
> > Ciao
> > Hannes
> >
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