BACKGROUND:
My company is acting as the Service Provider to our clients that are the IDP. We use OpenAM, but our clients use ADFS or Shibboleth. We exchange metadata files for establishing federations, not URLS. A client asked why we require an AuthnContext class schema (specifically PasswordProtectedTransport), and not only do we not know why, we don't know how to change it or what that would mean.
QUESTION:
What is the functional difference between using "PasswordProtectedTransport" vs "unspecified" for the AuthnContextClassRef in a SAML2 assertion?
We currently use PasswordProtectedTransport amongst all our clients, but no one at my company can tell me why we require this. If we remove it, the federation stops working with a 500 error and a "NoAuthnContext" in the SAML trace. We also don't understand that, as I was led to believe from SAML documentation that having a schema is optional for the authentication. Even so, I saw no explanation anywhere of what the implications of using "unspecified" would be.
I can’t find any thorough explanation or discussion anywhere about this topic and was hoping someone could elaborate for me, as I am struggling to find light on this.
RequestedAuthnContext in a request is a mean for a SP to ask the IDP to authenticate the user with a specific authentication mechanism.
For example, if you specify PasswordProtectedTransport in your request, the IDP knows it has to authenticate the user through login/password, protected by SSL/TLS.
The IDP says in its response which mechanism it used to authenticate the user through AuthnContextClassRef.
RequestedAuthnContext in a request is optional, but AuthnContextClassRef in the assertion is mandatory as specified by the SAML schema (hence the 500 error you encountered).
Basically, the unspecified URN is used by the IDP to say "I don't want to tell you how I identified the user".
As a SP, you have the choice to accept that answer or reject it, if you want to ensure that the user is authenticated with a secure mechanism.
Related
I am looking to do IdP Discovery and i need to do this with Pingfederate Software. End Goal here is customers will request access to a resource. Then get redirected to an IdP where they see a logon form ... input their email address and then depending on their email domain they get redirected to another IdP where authentication will take place. SAML Assertion will get posted back and the customer can then access the application.
I know pingfederate has persistent cookie etc but i dont think this will work well. Has anyone tried IdP Discovery in Pingfederate?
The PingFederate Standard IdP Discovery is a cookie based mechanism that identifies the IdP, or matching of entityID to IdP. We have used the OOTB PingFederate capability and found it does work well for certain use cases and business requirements for user experience. This blog describes alternative approaches that are popular within industry to accomplish IdP Discovery. We have found that most service providers tend to use one of the forms of IdP Discovery described in the blog. The real driver for the implementation approach is business requirements for user experience. For PingFederate, if you choose not to use the out of the box cookie mechanism, then you will need to implement one of the other design patterns. I do know that there are Ping System Integration partners that have expertise and implementations of each of the design patterns described.
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.
First of all I do not have any experience with SAML (version 2).
I was asked to investigate how we can make an existing site, which has a normal login page with a username and password page, ready for SSO with SAML.
There are some tools around which we can use in order to do this.
So I think it is not so difficult to implement the SSO part.
But however it is not clear to me how the authorization is managed.
The system (web site) is using authorization rights in order to determine if the user is able do access certain parts and if he does, the right type he has (view, create or edit).
These rights are assigned to each user by an administrator in the system itself.
When a user logs in the system by specifying his credentials (without SAML/SSO) his rights are also retrieved.
How is this done when a person logs into the site by using SSO?
Is there a mapping of the userId which is know by the IdP (Identity Provider) to the userId which is know by our system?
And is this send in the SAML response from the IdP?
Or is this done in another way?
Thanks in advance
SAML is mainly a authentication protocol but there are still many ways to solve this. SAML supports sending authorization infromation in AuthzDecisionStatement in the assertion.
Another alternative is to extend SAML using XACML which is a big framework for transferring Authz information.
However the support for these are limited in many SAML providers.
The simpler solution and probably the best in your case, if it is just one access right per user, is to send it as an attribute in the SAML assertion. This can usualy be mapped against for user properties.
My understanding of the SAML (v2) protocol is that Service Providers should be interacting directly with Identity Providers to exchange authorisation request and assertion messages.
I can think of a number of reasons why this would be a bad idea (undermines message signing, gives intermediate IdP access to info from other IdP), but are there any scenarios supported by SAML that would allows the following arrangement?
SP <------> MainIdP <------> ThirdPartyIdP
So (hypothetically) assuming that MainIdP has some clever way of determining that the SP user needs to authenticate against ThirdPartyIdP, it would delegate to the ThirdPartyIdP and then receive the response, process it and reply to the SP. Does SAML allow this? (I am asking because a software supplier has suggested this approach and I believe it isn't supported, as well as being fundamentally insecure.)
The "correct" approach as I understand it is for the SP to be configured to know about both IdPs independently, and either present the user with a list to pick from, or delegate to a Discovery Service which can ask the user, or infer by some other means, which IdP to use. Is this right?
Thanks.
Most federation identity providers for SAML have the concept of a "Home Realm Discovery" screen.
The SP is "bound" to the MainIdP but the MainIdP presents a screen which shows all the other IDP's that it is federated with. From that list, you pick the ThirdPartyIdP.
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.