@Brian +1
I agree that the section is confusing and that errata should be published
about it, but before we go there it might be interesting why someone took
the effort to describe the situation with an empty client secret, because
including these suggestions will break the ability for an sever to dectect
a double authentication when the client secret is an empty string
- As for the client secret not being an empty, it might be that it's
updateable by the client.Maybe specifying that a client secret can't be an
empty string might be the most elegant solution.
- Secondly I couldn't find the the "If a client_id parameter is present in
conjunction with some client authentication mechanism, then both must
refer to the same client. " section nor can i find anywhere in the spec
what the
I do agree that many to be specs and implementations use the client_id in
the body, and there are valid arguments to be made for that. But without
errata in the OAuth2 spec they are violating the OAuth2 spec, And seeing
the nature of it i think adding errata to the OAuth2 spec is the way to go
Do you have another suggestion to interpret the problematic section ?
@Nat
Nowhere in the spec i can find that they must match or even that the AS is
supposed to do anything with it
When you read the specs at this point the problem is that if a client_id
is in the body it is the same as a client_id and a secret (but a blank
secret) and that is a double authentication when the Auth header is
present
@all
Shoudln't we define or maybe in the OIDC spec add some information so that
the AS needs to do something with that clien_id in the body, saying it
must match the client_id coming in somewhere else ?
Or at least have the AS do something with it .
From: Nat Sakimura <[email protected]>
To: Brian Campbell <[email protected]>
Cc: Tom Van Oppens <[email protected]>, oauth <[email protected]>
Date: 26/01/2018 01:16
Subject: Re: [OAUTH-WG] rfc6749 question about the optional use of
the client_id in the request body
+1 to Brian.
I would like to point out that listing the participant in the protocol
message and the authentication of the message sender is an entirely
different thing. I see no problems in duplicating client_id in body and
header. Of course, they have to match and must fail the authentication if
they do not, but this should not be a problem. In fact, it may even be
desirable for the message body to have self-contained references to the
participants in the authentication protocol as shown in [1]. In such a
case, it will necessarily duplicate in case of the basic authentication.
[1] Basin, D., Cremers, C., Meier, S.: Provably Repairing the ISO/IEC 9798
Standard for Entity Authentication. Journal of Computer Security -
Security and Trust Principles archive Volume 21 Issue 6, 817-846 (2013)
Best,
---
Nat Sakimura
On Thu, Jan 25, 2018 at 11:28 PM Brian Campbell <
[email protected]> wrote:
Hi Tom,
Indeed RFC 6749 is not well written with respect to this situation and
unfortunately leaves some room for varied interpretations. However, in my
own not entirely uninformed view having worked on this stuff for awhile
now, it is erroneous to interpret the presence of the client_id parameter
in the request body as client_secret_post authentication when there is no
corresponding client_secret parameter. As you alluded to, there are other
types of client authentication that explicitly allow (JWT, SAML, and their
base spec) or require (MTLS) the client_id parameter and the OIDC core
spec even has an example of the client_id parameter in the body when doing
JWT client auth. If client_id with no client_secret in the request body
actually implies client_secret_post, then those RFCs (one soon to be RFC)
and OIDF standards are all contradicting OAuth 2.0 /RFC 6749. Those
supplementary standards as well as widespread implementations/deployments
in practice should, I believe, be considered more authoritative than one
particular implementation's problematic (in terms of interoperability)
interpretation of a not particularly well written area of the OAuth spec.
The problematic text from
https://tools.ietf.org/html/rfc6749#section-2.3.1 says that "the client
MAY omit the [client_secret] parameter if the client secret is an empty
string" so it would only really be reasonable for an AS to reject a
request as having two client authentication methods in the case that it
issued a client the empty string as a client secret (not a public client
but a client with an empty string as its actual secret), which should
never happen in practice, and that client sent both a basic authorization
header without a password and a client_id without a client_secret in the
body. That's one way to read it anyway. And regardless that text in Sec
2.3.1 is problematic and should probably be updated with an errata on RFC
6749 to get rid of the text about empty string password and just state
that the client_secret parameter is required when doing client_secret_post
authentication. Unfortunately the errata often get overlooked but it'd
still be good to have that fixed somewhere and a published RFC can't be
changed so errata is the only real option to document the actual intent of
the original specification.
The presence of the client_secret parameter should be the only thing that
implies client_secret_post authentication.
If a client_id parameter is present in conjunction with some client
authentication mechanism, then both must refer to the same client.
On Wed, Jan 24, 2018 at 3:19 AM, Tom Van Oppens <[email protected]
> wrote:
Dear Oauth Mailing List
After some discussion i had i wanted to ask you for some guidance.
For the following request
request_uri
https://example.com/token
request_method
POST
request_headers
{"Accept":"application/json","Authorization":"Basic
bWFnaWNpZDpwb3RhdG9zZWNyZXQ=","Content-Type":"application/x-www-form-urlencoded","Content-Length":"91"}
request_body
grant_type=client_credentials&scope=accounts&client_id=magicid
We had some discussions whether or not this request is a valid request, to
be more exact wether the clientid can be in the body.
Section 2.3.1 states
A client MAY use the "client_id" request parameter to identify itself when
sending requests to the token endpoint.
But at the same time in the case of a client password (2.3.1)
The clientid and secret are carried in the basic auth header as a form of
authentication as a preferred method ,
But the standard states that if you choose to use the body as a form of
authentication that if you can ommit the clientsecret the clientsecret is
an empty string, therefore passing only the client_id is the same as
passing the client_id and an empty string clientsecret .
So the current request would be according to the spec interpreted as
follows
Authentication 1) basic auth cleintid:secret
Authentication 2) body auth clientd and blank secret
You can choose to use the client_id in the body with public clients or in
the confidential client (the Lloyds situation) if you choose to add the
clientsecret there as well and are not using the basic auth header (this
is due to spec section 2.3 which states
The client MUST NOT use more than one authentication method in each
request.
In short there is no way in the spec that allows for the oauth provider to
distinguish between your intention of sending in the client_id again for
identification and a malformed request with double authentication.
So my stance is (for now) that you cannot send a clientid when you find
yourself in the clientid with a corresponding password situation.
Is that a correct statement ?
and if it is not how would that work ?
and if it is, when can you send the clientid in the body but use something
else for authentication (something like mtls ?) ?
Kind Regards
Van Oppens Tom
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