Does a SAML application store the state while creating a request (Okta's document says it doesn't)? - saml

Okta's official document states that a SAML Service Provider does not store any state:
https://developer.okta.com/docs/concepts/saml/#planning-for-saml
The Service Provider doesn't know if the Identity Provider will ever complete the entire flow. Because of this, the Service Provider doesn't maintain any state of any authentication requests generated.
However, I also read that the SAML Application will generate a request ID which is unique to that particular request. And the SAML response will contain this same request ID which the application will use to figure out which request it corresponds to.
There is a contradiction between Okta's doc and the SAML concept. The application is storing the state. Is Okta's doc inaccurate or am I missing some concept over here?

I think Okta's document is misleading. As you say, one of the checks that a service provider should make is that the InResponseTo field in the SAML response matches the SAML authn request's ID. This is essentially state information the SP must remember so it can perform this check when the SAML response is received. Our SAML implementation certainly maintains state information and I would imagine most, if not all, implementations would.

Related

Is it possible to tie initial SAML request to the SAML Assertion received from the IDP?

I am looking for a way to tie the SAML request I make to an IDP to the SAML Assertion it sends back. Is there a way to do that?
One idea I had was to use the SessionIndex. I have found that in practice, in some cases the SessionIndex can be used to do this, because some SAML servers return the ID from the initial request as the SessionIndex in the SAML Assertion, but I have also found that is not done universally / does not seem to be required by the spec. It seems like the intention of the SessionIndex is just to tie together the SAML Assertion with subsequent calls, e.g. logout attempts, so there's no requirement that it be tied to the initial request. I draw that conclusion from this post, which says "At least one assertion containing an MUST contain a element with at least one element containing a Method of urn:oasis:names:tc:SAML:2.0:cm:bearer. If the identity provider supports the Single Logout profile, defined in Section 4.4, any such authentication statements MUST include a SessionIndex attribute to enable per-session logout requests by the service provider." I have also reviewed this post, which breaks down the use of SessionIndex and I think supports the same conclusion.
I don't see anything else in the spec that seems promising, but I am hoping I may be missing something - is there any reliable way to pass data to the IDP in a SAML request and get it back in the SAML Assertion?
FYI, the reason why I want this is to support mobile sso login where my mobile device uses an embedded web browser to make an OAuth2 call to my web server, the web server authenticates the user, and then sends back an authorization code to the mobile device with a redirect. I want to use PKCE to secure the OAuth2 flow between the mobile device and the web server, but that requires me to be able to tie the initial request call to the final redirect with a shared code.
There are at least two methods that can be used, so long as the user journey starts where it should, on the page they are trying to get to, making this a service-provider initiated authentication request. As the service provider in a SAML-based federation, you start the process by sending the identity provider an AuthnRequest.
The first method availables comes by tracking the AuthnRequest's ID. In a good SAML implementation, that AuthnRequest's ID is big and random and likely not repeatable in our lifetime. The SAML Profiles spec says on lines 625-626:
If the containing message is in response to an <AuthnRequest>, then
the InResponseTo attribute MUST match the request's ID.
Therefore, as long as you keep track of the ID's that you send out, then you can tie the Request's ID to the Response's inResponseTo.
The second method at your disposal is RelayState. This is an aptly-named element of an AuthnRequest that you can use to transfer state to the Identity Provider an back. This is a field that you can use as you see fit as the service provider, and the responder has to send it back. The Bindings spec says on lines 265-271:
Some bindings define a "RelayState" mechanism for preserving and
conveying state information. When such a mechanism is used in
conveying a request message as the initial step of a SAML protocol, it
places requirements on the selection and use of the binding
subsequently used to convey the response. Namely, if a SAML request
message is accompanied by RelayState data, then the SAML responder
MUST return its SAML protocol response using a binding that also
supports a RelayState mechanism, and it MUST place the exact
RelayState data it received with the request into the corresponding
RelayState parameter in the response.
As such, you can put something in that field, and the IdP must parrot it back untouched. You should make sure that what you put in there doesn't compromise the user or security, so just be mindful of how you use it. It's going to end up in logs somewhere.

Auth0->Atlassian SAML SSO Problem (SP Entity and ACS URL)

So I'm trying to integrate single sign-on with Auth0 (being both the service provider and the identity provider) with the Atlassian stack.
Atlassian offer SAML single sign-on. However, it is telling me:
Your users won't be able to log in with SAML single sign-on until you've copied
the values for SP Entity ID and SP Assertion Consumer Service URL to your
identity provider.
I've put the assertion consumer service URL in place of the callback URL, I've done some research and I'm almost certain this is correct.
However, the issue is with the Entity ID. Where does this go?
I've not used Auth0 before, but I think you have to set it as audience in the settings, e.g. see https://auth0.com/docs/protocols/saml/saml-apps/heroku
IMHO but the configuration option is a bit misleading. Instead of using audience, using EntityID might be clearer, as this is also the term used in the SAML spec.
I am assuming that auth0 acting as a service provider.
Assertions Consumer service URL should be :
https://YOUR_DOMAIN/login/callback?connection=YOUR_CONNECTION_NAME
Entity ID of the service provider should be:
urn:auth0:YOUR_TENANT:YOUR_CONNECTION_NAME
You can download service provider metadata like below in the XML format and upload to IDP to generate configuration.
Navigate to https://YOUR_DOMAIN/samlp/metadata?connection=YOUR_CONNECTION_NAME
Additional:
URI: urn:oasis:names:tc:SAML:2.0:nameid-format:entity Indicates that
the content of the element is the identifier of an entity that
provides SAML-based services (such as a SAML authority) or is a
participant in SAML profiles (such as a service provider supporting
the browser SSO profiles). Such an identifier can be used in the
element to identify the issuer of a SAML request, response,
or assertion, or within the element to make assertions about
system entities that can issue SAML requests, responses, and
assertions. It can also be used in other elements and attributes whose
purpose is to identify a system entity in various protocol exchanges.
The syntax of such an identifier is a URI of not more than 1024
characters in length. It is RECOMMENDED that a system entity use a URL
containing its own domain name to identify itself
(SAML CORE specification, section 8.3.6)
https://www.oasis-open.org/committees/download.php/7473/sstc-saml-core-2.0-draft-15-diff.pdf
https://spaces.at.internet2.edu/display/InCFederation/Entity+IDs

SAML spec: returning to the SP without a user

I'm using the standard SAML 2.0 SP-initiated SSO protocol for authentication.
Normally the IdP returns a samlp:Response XML object to my SP, containing a saml:Assertion about the authenticated user.
Does the SAML spec allow the IdP to return a response to the SP that doesn't contain user information?
I'd like handle the situation where authentication couldn't be done, but we want to return to the SP's site. Maybe the IdP could return some kind of error or message to our SP? Right now it seems like if authentication is impossible, the user is stuck on the IdP's site.
I guess they could just redirect to an agreed-upon URL, although then you would lose the RelayState information. Would that be the right approach, or does the SAML spec handle this scenario?
The SAML2 spec handles this. The Idp can return a samlp:response with a status code of Responder meaning that the idp failed to fulfill the request. Then there can be more detailed status information on exactly why.
But the case where an Idp fails to authenticate the user can be handled in the protocol. However, I think that most Idps behave as you describe - keep the user on the Idp if things goes wrong.
Added by OP — this is from the SAML spec:
<StatusCode> [Optional]
A subordinate status code that provides more specific information on an error condition. Note that responders MAY omit subordinate status codes in order to prevent attacks that seek to probe for additional information by intentionally presenting erroneous requests.
The permissible top-level values are as follows:
urn:oasis:names:tc:SAML:2.0:status:Success
The request succeeded. Additional information MAY be returned in the and/or elements.
urn:oasis:names:tc:SAML:2.0:status:Requester
The request could not be performed due to an error on the part of the requester.
urn:oasis:names:tc:SAML:2.0:status:Responder
The request could not be performed due to an error on the part of the SAML responder or SAML authority.
urn:oasis:names:tc:SAML:2.0:status:VersionMismatch
The SAML responder could not process the request because the version of the request message was incorrect.

What SAML bindings should I support as a web SSO Service Provider? How is the authenticated user!s info passed back to me?

I!ve a question similar to How To Become a SAML Service Provider, but it misses some part I would like to clear up.
The SAML SSP profile spec describes several possible bindings, and states that the usage depends on SP and IdP setups.
The SAML Conformance and Profiles specifications identify the SAML
bindings that can legally be used with these two messages.
Specifically, an Authentication Request message can be sent from an SP
to an IdP using either the HTTP Redirect Binding, HTTP POST Binding,
or HTTP Artifact Binding. The Response message can be sent from an IdP
to an SP using either the HTTP POST Binding or the HTTP Artifact
Binding. For this pair of messages, SAML permits asymmetry in the
choice of bindings used. That is, a request can be sent using one
binding and the response can be returned using a different binding.
The decision of which bindings to use is typically driven by
configuration settings at the IdP and SP systems. Factors such as
potential message sizes, whether identity information is allowed to
transit through the browser (if not the artifact binding may be
required) , etc. must be considered in the choice of bindings.
The first question I have: as a Service Provider, am I free to choose any one of the SP -> IdP bindings, and it will work with any IdP out there, or I should make this configurable in my implementation and support all the bindings? (Nota bene: I will probably integrate an existing saml library to help my life, but I should know what configuration options should I allow and support on my interfaces.)
The second question is about the SamlResponse coming back from the IdP upon successful authentication. As far as I understand, SAML just tells me that the user suucessfully authenticated with the IdP. As a result I would expect to give me back some user identifiers in the Response, like a uid, username or e-mail address that I can query from a local user db or LDAP and run app-specific authorization logics.
How can I ask the IdP the user identifier I need and how/where will it be returned? I can't see anthing related to this in the Wikipedia example
Depending on what bindings your SAML-IdP and SP server supports, you can choose any combination of binding pair. Typically all major SAML-IdP supports most of binding specified in SAML-spec. Also you have to take security and performance considerations. Artifact is more secure but take two round-trips to complete SAML-Authn process, because it make back-end call communication (unlike POST or Redirect) while sending and receiving SAML messages. If your SAML-IdP and SP server supports binding configuration, then you use those bindings in runtime.
NameID format identifies user between IdP and SP, which is sent in SAML Assertion by IdP. It can be emailAddress, unspecified, transient, persistent and few others. Check Section (8.3) Name Identifier Format Identifiers from SAML Spec for more details. Also you could request IdP to send user attributes (that exist in IdP identity-store) in SAML Assertion.

How should I be implementing the HTTP POST Protocol Binding for SAML WebSSO Profile?

I've implemented my Service Provider and Identify Provider following the SAML Profile for Web SSO using HTTP POST Protocol Binding. However, I am a bit confused as to how the Identity Provider will provide an <AuthnStatement> if the HTTP POST coming from the Service Provider is not tied to a session on the Identity Provider.
Could someone enlighten me how one would be able to do this?
The other approach I could use is the HTTP Redirect Binding, but that requires User-Agent intervention (i.e., the browser), often using the User-Agent simply as a pass-thru intermediary to faciliate the Request-Response message exchange. I'd rather use HTTP POST for this reason, because the message exchange occurs server-side, so the user sees nothing happening on their screen.
However, using HTTP Redirect makes more sense to me with respect to how I'd be able to tie a session to a request. Since the HTTP Redirect is facilitated via a User-Agent, the request to the IdP will have a session (if previously authenticated). What I don't get though is how to send an <AuthnRequest> on a HTTP Redirect. Answered by JST
So I'm a bit confused and would love to hear what other people are doing. Here are my questions again:
Using the HTTP POST Protocol Binding with the IsPassive option the <AuthnRequest>, how do I tie a request made by the Service Provider to a session on the Identity Provider? In other words, how does the Identity Provider know who is making the request if the POST is coming from the Service Provider which is technically an anonymous session?
Using the HTTP Redirect Protocol Binding, how do I send an <AuthnRequest> to the Identity Provider if I am using a HTTP Redirect? Answered by JST
UPDATE
Sorry for the confusion if I was unclear in my explanation above. I am implementing both the IdP and SP (via a plugin). The IdP is an existing application for which I want the SP (a third-party system) to use for authentication (i.e., Web SSO). I am developing a simple PoC at the moment. The SP is actually a third-party Spring application for which I am developing a plugin to perform the SAML operations.
I should have mentioned that I am trying to do this using the IsPassive option, that meaning the User-Agent doesn't come into play during the message exchange. It is simply the catalyst that gets the SAML-party started. Right? With that in mind, given that the user is anonymous at Step 1, what does the SP send to the IdP to allow the IdP figure out whether the user is already authenticated? Because of IsPassive, the HTTP POST isn't sent via the User-Agent
UPDATE
Question 1 Revised: How does the IdP resolve the Principal when the AuthnRequset is sent with the IsPassive option on?
Straight from the SAML 2.0 Profiles document, page 15, lines 417 to 419:
In step 4, the principal is identified
by the identity provide by some means
outside the scope of this profile.
What I'm really after is an explanation how to implement some means.
The thing to keep in mind is that there's no connection between a session on the IdP and a session on the SP. They don't know about each other, and communicate only through the SAML messages. The general steps for SP-initiated SAML SSO are:
Anonymous user visits resource (page) at SP.
SP identifies that user needs to be authenticated at IdP.
SP constructs AuthnRequest and sends to IdP.
IdP does some sort of authentication, constructs SAML Response and sends to SP.
SP validates Response and, if valid, does whatever is necessary to identify user at SP and get them to originally requested resource.
Yes, there does need to be some way to connect the SP's AuthnRequest to the IdP's Response. That's covered by the SAML spec: the SP's AuthnRequest includes an ID value, and the corresponding response from the IdP MUST include an InResponseTo attribute (on its SubjectConfirmationData element) with that ID value. The Authentication Request Protocol also allows the SP to pass a RelayState parameter to the IdP, which the IdP is then REQUIRED to pass along unchanged with the SAML Response. You (in the SP role) can use that RelayState value to capture state information allowing the user to be relayed to the originally requested resource.
That implies that when you implement an SP, you'll need some mechanism for recording ID and RelayState values, and your Response processing needs to validate InResponseTo and RelayState values it receives. How you choose to create and interpret RelayState values is up to you, but keep in mind that there is a length limit. (We use random GUID values corresponding to locally saved state data, which has the extra advantage of not giving any hint of meaning to the RelayState values.)
How does the IdP know who is making the request? The AuthnRequest must include an Issuer element that identifies the SP. It might also contain an AssertionConsumerServiceURL (the URL to which the Response is to be sent), or the IdP may have a local mapping of the Issuer to the proper URL.
How do you send an AuthnRequest using HTTP Redirect? The only difference between AuthnRequest sent using POST vs. Redirect, besides using GET rather than POST, is that the AuthnRequest XML has to get compressed (using the DEFLATE encoding).
Hope that answers most of your questions.
John,
I might suggest taking a step back and doing some more research before you decide to write your own SAML IDP/SP Implementation. You appear to be mixing Bindings with Profiles, Unsolicited vs Solicited Web SSO as well as the fact that SAML requires that the User Agent (aka Browser) is the bearer of almost all the messages between the IDP and SP. There is also a ton of info in the spec that will will have to implement to ensure your solution is actually secure.
I would suggest starting with our SAML Knowledge Base and then moving on to the OASIS SAML 2.0 Technical Overview for information on these flows.
Alternatively, if you decide to go best-of-breed you can check out our PingFederate product which can enable ALL the SAML IDP/SP use cases for you in < a day.
Hope this helps -
Ian
Unlike Ian, I am not associated with a company producing SAML-related products. However, I'd give somewhat similar advice: step back and identify why you are implementing SP or IdP. Are you really acting as both SP and IdP, or are you really just one or the other? If you're implementing/acting as IdP only, then it's fairly likely that a product like PingFederate or something similar offers all you need through configuration rather than requiring you to write custom code. If you're implementing SP, then such a product MAY be able to help you out, but it depends to a large extent on the characteristics of the system you're integrating it into. I am speaking as a developer who has done both IdP and SP implementations, and evaluated several tools before determining that because of our specific system, clients, and requirements, a custom implementation was our best option. It's been in place for over a year, with several clients using it (including some using varying commercial IdP tools).
If you can identify your use cases in terms of SAML profiles/bindings, then you'll be better equipped to make a buy-vs-build decision.