[Openid-specs-ab] Login Initiation endpoint.

Brian Campbell bcampbell at pingidentity.com
Mon Dec 2 21:00:13 UTC 2013


IdP initiated SSO via the POST binding is arguably one of the most
successful aspects of SAML and there's not an obviously analogous thing in
Connect, which I do believe will be a point of friction in migration and
adoption. With that in mind, I agree with Mike that's worth discussing.
However, it is a pretty significant change (technically and
philosophically) to be considering given the goal of going final early next
year.

Sending it via an (auto) form post rather than a redirect keeps the token
out of the URL, which prevents the token from leaking to other sites via
the referer [sic] header. The post body is also logged in a lot fewer
places where the query string often ends up in request logs and browser
history and other places you don't want a credential to end up. There are
probably other reasons not to pass a token in the URL but those two come to
mind first.

The question about id_token_hint in the query string is a good one. It's
probably not a great idea to pass it that way but I *think* that proper
nonce checking would prevent using an id token leaked via id_token_hint
from being used to by an attacker to sign in and create a session. The
general question probably deserves some more discussions though. If the
login initiation endpoint accepted an id_token directly to create a
session, however, the protections the nonce gives don't apply and, in some
cases, a leaked id_token_hint could likely be used maliciously.

Honestly, I've never really understood the CSRF issue with login. What is
the concern? That some other CSRF vulnerable action will be taken after the
session is created via CSRF login? Or is it something more fundamental? How
do IDPs typically prevent CSRF'd SSO? Or do they?



On Tue, Nov 26, 2013 at 5:25 PM, Mike Jones <Michael.Jones at microsoft.com>wrote:

>  I’d like this to be a topic on Monday’s call.  I understand people’s
> initial reaction against making additions now, but I think this at least
> deserves serious discussion, because the feature request is driven by
> developers actually deploying the protocol and trying to migrate from
> SAML.  It’s not a whimsical made-up feature or coming from out of the
> blue.  Not having this could be a perceived deployment blocker relative to
> SAML.
>
>
>
> John, in the meantime, can you please speak to why CSRF is not a problem
> when the proposed parameter is used?
>
>
>
> Also, can you speak to why you want the parameter passing mechanism to be
> form post?  Even if we don’t add the id_token parameter, does the current
> id_token_hint parameter need to be sent via form post rather than as a
> query parameter?  If this is true, why is it ok to pass the id_token_hint
> value to the authorization endpoint as a query parameter?  (Or is it
> actually not OK?)
>
>
>
>                                                                 -- Mike
>
>
>
> *From:* openid-specs-ab-bounces at lists.openid.net [mailto:
> openid-specs-ab-bounces at lists.openid.net] *On Behalf Of *John Bradley
> *Sent:* Tuesday, November 26, 2013 5:15 AM
> *To:* Nat Sakimura
> *Cc:* Openid-specs Ab
> *Subject:* Re: [Openid-specs-ab] Login Initiation endpoint.
>
>
>
> SAML relies on the IdP to prevent CSRF as the login session starts at the
> IdP.  The RP/SP knows that it is idP initiated.
>
>
>
> This is a common pattern in SSO where the user is redirected to another
> related site with a SAML assertion that the recipient RP uses to establish
> a new session with the user.
>
> This is much safer then trying to use cross domain cookies which is the
> other common tactic.
>
>
>
> I was looking at George's proposal to bootstrap a web session from a
> native app. He had to invent a new endpoint and special access token to do
> it as there was no way to accomplish it with the current endpoint.
>
>
>
> I am OK with saying that it is a bootstrap id_token hint and can't
> directly be used by the client.   However there are a bunch of things that
> can't be done as the IdP/AS can't pass any state to itself through the
> request.   Allowing a bootstrap id_token to be sent and returned in the
> authorization request as the id_token_hint is the simplest way to send
> signed state.
>
>
>
> The important thing I missed in the proposal was sending it as a form-post
> body to prevent leaking the id_token in referrer.
>
>
>
> If we wan't to leave this for an extension we should at least say the
> login initiation endpoint can take a form POST so later extensions are
> easier.
>
>
>
> John B.
>
>
>
>
>
> On Nov 26, 2013, at 4:39 AM, Nat Sakimura <sakimura at gmail.com> wrote:
>
>
>
>   +1
>
>
>
> I wonder how these SAML implementations are dealing with CSRF.
>
> =nat via iPhone
>
>
> Nov 26, 2013 3:03、"Richer, Justin P." <jricher at mitre.org> のメッセージ:
>
> I really don't like this. It goes against the structure of how OAuth
> works, and there's no way for the RP to put anything into the id token
> (like nonce, state, etc.) to bind to a particular session and prevent a
> stolen id token being used to log in directly by another user. The fact
> that the RP starts the auth conversation is important, and I'm not at all
> comfortable with having this workaround.
>
>
>
> At the very least, this should be proposed as an extension and get
> hammered out separately. (But even then I don't think it has legs.)
>
>
>
>  -- Justin
>
>
>
> On Nov 25, 2013, at 10:58 AM, John Bradley <ve7jtb at ve7jtb.com>
>
>  wrote:
>
>
>
>   For Core Section 3 I would like to add the following optional parameter
> to the login initiation endpoint.
>
>
>
> id_token
>
> OPTIONAL. If the initiator is the iss then it may include an initial
> id_token.  The value of exp SHOULD be set to a small value in the range of
> 5 minutes.
>
> The id_token must contain a valid aud restricting it to the client
> receiving it.
>
> If the client receives a value for this string-valued parameter, it MUST
> include it in the subsequent authorization request as the id_token_hint parameter
> value.
>
>
>
>
>
> I have been getting push back from people looking to convert from SAML
> that Connect forces many more round trips than SAML for doing IdP initiated
> login.
>
> Sending an initial short lived id_token lets the client do the quick
> customization of the UI that the id_token was intended to enable while
> allowing the client to get access tokens and a new id_token in the
> background using prompt=none.
>
>
>
> This also reduces the eventual pressure to add more parameters to the
> endpoint as the AS can tack on additional claims it needs to maintain state.
>
>
>
> I think we did have the id_token as a parameter at wine point then changed
> it to the login_hint when that was added to make it more general.
>
>
>
> I know this is a late addition request.
>
>
>
> John B.
>
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