[Openid-specs-ab] Login Initiation endpoint.

John Bradley ve7jtb at ve7jtb.com
Tue Nov 26 13:14:49 UTC 2013

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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