It makes sense to me that the sub should always be the subject of an issued
token.

thx ..Tom (mobile)

On Sun, Oct 29, 2023, 7:54 PM Justin Richer <jric...@mit.edu> wrote:

> I disagree with the utility of just "sub" here. The subject of the token
> is always contextual to the issuer of that subject - however, the "iss"
> field here is the issuer of the transaction token and not the issuer of the
> subject identifier. As such, it's much less ambiguous to use the compound
> field. The concerns are similar to SET, where sub_id was initially defined
> - - the source context for the subject can't be assumed to be the same as
> that of the transaction token.
>
> -Justin
> ------------------------------
> *From:* OAuth <oauth-boun...@ietf.org> on behalf of Atul Tulshibagwale <
> a...@sgnl.ai>
> *Sent:* Thursday, October 26, 2023 4:07 PM
> *To:* Kai Lehmann <kai.lehmann=401und1...@dmarc.ietf.org>
> *Cc:* oauth@ietf.org <oauth@ietf.org>
> *Subject:* Re: [OAUTH-WG] sub_id in draft for Transaction tokens
>
> Hi Kai,
> Thanks for this and other feedback you have provided.
>
> The primary reason for using "sub_id" was to enable a format that can be
> more expressive than the "sub", which is always a string.
>
> I can see the benefit of having either "sub" or "sub_id" in the
> Transaction Tokens spec. "sub" will allow for more compact tokens where a
> richer subject format is not required.
>
> Atul
>
>
> On Thu, Oct 26, 2023 at 1:52 AM Kai Lehmann <kai.lehmann=
> 401und1...@dmarc.ietf.org> wrote:
>
> Hi all,
>
>
>
> I very much like the draft. We have a similar token mechanism implemented
> for our service infrastructure.
>
>
>
> I am not quite sure about the reasoning behind using “sub_id” for the
> subject identifier instead of using “sub” as used across OAuth technology.
> The referenced draft for SubjectIdentifiers is related to a security event
> environment. The origin of the sub can be manifold in those scenarios. In
> the OAuth environment, on the other hand, we do usually have the original
> access token at the beginning of the call and there, a sub is usually
> present and well defined within the trust boundary.
>
>
>
> In our implementation, we simply create an internal token (that’s our term
> for it) and copy the sub from the AT. We have a few entry points where we
> do not have a user interaction (for instance incoming mail via SMTP which
> needs to be delivered to the end-users mailbox storage). In those
> scenarios, we allow the very small list of gateways (e.g. SMTPD) to call
> the token exchange with other parameters than the AT. The recipient email
> address needs to be provided which is being used to look up the actual
> subject identifier (in our case it’s a UUID tied to the user account) which
> is put into the created internal token. This way we ensure that the “sub”
> claim is always the same type/format. The internal services do not need to
> interpret/support multiple formats as they can rely on the token exchange
> server to provide it.
>
>
>
> The referenced draft for subject identifiers for security events allows
> for the “sub” in parallel to the “sub_id”. My suggestion would be to allow
> to use either “sub” or “sub_id”. I would use “sub” as long as all parties
> (workloads) within the trust boundary understand what the sub value is and
> it is guaranteed that the transaction tokens are generated with the same
> sub format/type.
>
>
>
> Best regards,
>
> Kai
>
>
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