Subject: Re: [secdir] Security review of draft-ietf-oauth-token-exchange-14

From: Brian Campbell <[email-masked]>
Date: Mon, 10 Sep 2018 15:44:22 -0600

Hi Hilarie,

I've published
<https://mailarchive.ietf.org/arch/msg/oauth/Dqlg3JQqhChHy83j4IwqhLeoR88> a
new draft -15 of OAuth Token Exchange
<https://tools.ietf.org/html/draft-ietf-oauth-token-exchange-15>, which I
hope/believe addresses the comments you raised.
<https://tools.ietf.org/html/draft-ietf-oauth-token-exchange-15>

Thanks again for the review,
Brian

On Mon, Aug 13, 2018 at 11:36 AM Brian Campbell <[email-masked]>
wrote:

>
> On Fri, Aug 10, 2018 at 3:26 PM Benjamin Kaduk <[email-masked]> wrote:
>
>> ...
>> With the disclaimer that I haven't read token-exchange recently and am
>> mostly going off my memory of the mailing list discussions, it seems like
>> the key consideration here is that token exchange allows you to convert a
>> token that may be opaque to you into one that has inspectable fields, and
>> those fields can be privacy sensitive.  So a JWT response should only be
>> given to a requestor that trusted to know such information; a lot of the
>> time, that has large overlap with being trusted to have the token in the
>> first place, but potentially there is some amount of non-overlap.
>>
>> The considerations from 7523 of course also apply, and sensitive
>> information should not be sent over unencrypted channels, but isn't the
>> above paragraph an aspect inherently new to token exchange?
>
>
> I don't think it's unique to token exchange. RFC 7523, for example,
> defines the use of a JWT as an authorization grant used to obtain an access
> token from a authorization server. Unless encrypted as a JWE, the JWT in
> that scenario has fields that are inspectable to the client. And an OAuth
> access token is considered opaque to the client but whether or not
> information in the token is actually accessible to a client is an
> implementation detail of the authorization server. The latter is true for
> OAuth in general and not just these more specialized exchanges.
>
> The idea behind maybe incorporating some text similar to (but adapted to
> the context) what's in the privacy considerations of RFC 7523
> <https://tools.ietf.org/html/rfc7523#section-7> is that the
> considerations are pretty much the same - use TLS in transit, minimize the
> amount of information in the token, encrypt the token if disclosure of its
> information to the client is a concern.
>
>
>
>
>

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