last update: 2023/02/03
Tested with NetScaler 11, Citrix ADC 12.1 and 13.0

I needed to use a Citrix ADC (NetScaler) both, as a SAML identity provider (IDP) and service provider (SP). So I set up my test environment accordingly.

What my test environment looked like:

You see, I created two admin partitions on my Citrix NetScaler ADC, one for the service provider (SP partition), containing both, the SAML SP and a web server, and one for my identity provider (IDP partition), containing the SAML IDP.

I used these partitions to emulate “2 different Citrix NetScalers ADCs” as it does not make sense to have both, SAML-SP and SAML-IDP in the same data center (you could do conventional LDAP/RADIUS/TACACS authentication instead).

You may try using my configuration. Just surf to https://sp.josel.net. It will forward you to https://idp.josel.net (my IDP). Use test both, as username and password. You’ll then get forwarded back to the SP. I’d suggest doing your experiments using FireFox and SAML Tracer plugin (there is a similar plugin for Chrome). This will give you a good insight into SAML assertions. All Policies are displayed and discussed here.

You may download the original Citrix ADC (NetScaler) configuration for both, IDP and SP partition from here.

There is some chance for certs to be outdated as I don’t put much effort into this. The Saml IDP only does local authentication and will then forward to the SP showing content of www.norz.at.

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How SAML works:

In Saml the resource (SP, Service Provider, so the website needing authentication) uses an external witness (IDP, Identity Provider) to handle user logon. They send messages called assertions.

Of course, it’s a bit hard to make sure the IDP is the desired, trustworthy, one. Same for the IDP, it’s hard to find out whether the SP requesting authentication is a trustworthy one. Trust is created using certificates.

So a user connects to a resource (SAML SP). If the user had not been authenticated before, he gets forwarded to the logon server, the so-called SAML-IDP. The SAML-IDP does the authentication.

After successful authentication, the SAML-IDP forwards the user back to the SAML-SP, also sending the so-called assertion, the prove this user was authenticated successfully. You could think of an assertion like a man’s ID card. As soon as the SAML-SP has checked the assertion, it forwards the user to the resource.

SAML-SP and resource are always located on the same Citrix NetScaler, the SAML-IDP is usually located “somewhere else on the internet”.

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Certificates

SAML uses certificates to establish trust between SAML-SP and SAML-IDP.

The SAML-SP uses a server certificate to sign it’s an assertion (message) sent to the IDP. So the IDP needs to own the SP’s certificate (not its private key!). These certificates usually are private, not trusted ones.

The SAML-IDP also uses a certificate to sign (and encrypt) the assertion. This certificate (again: not the private key) has to be present on the SAML-SP, so the SAML-SP is able to decrypt and validate the assertion. Trust is established by providing the certificate. This certificate may be a self-signed one (that’s what Microsoft does with ADFS)

It’s possible to use the same certificates for both, SSL between client and SAML-IDP / SAML-SP, and to prove identity, however, I would rather use private (and therefore more trustworthy) certificates to prove identity. In my setup, I use the let’s encrypt certs for AAA-servers and self-signed ones to establish SAML trust.

In my example I use the following certificates:

SP.josel.net (my serviceprovider)

sp_signing_cert_privateKey	selfsigned	SP’s signing key. It has a private key
idp_signing_cert	selfsigned	IDP’s signing key. No private key here!
sp.josel.net	valid on internet (DigiCert)	SP’s SSL certificate (for HTTPS)

idp.josel.net (my IDP)

idp_signing_cert_privateKey	selfsigned	IDP’s signing key. It has a private key
sp_signing_cert	selfsigned	SP’s signing key. No private key here!
idp.josel.net	valid on internet (DigiCert)	IDP’s SSL certificate (for HTTPS)

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Cirtix ADC / NetScaler as a SAML Service Provider (SAML-SP)

A Citrix ADC / NetScaler may be a SAML identity provider for any SAML service provider. Another Citrix ADC / NetScaler may be the service provider, but also services like Microsoft Azure, Microsoft Office 365, Citrix Sharefile, and many more may use a Citrix ADC as an authentication source.

In my example, I just created a simple load-balancing vServer and added authentication to it. There is nothing special about it, in fact, I used my test server (a description might be found there).

add service svc_HTTP 93.83.148.43 HTTP 80
add lb vserver lb_vsev_sp SSL 192.168.0.100 443 -AuthenticationHost idp.josel.net -Authentication ON -authnVsName SAML_SP
bind lb vserver lb_vsev_sp svc_HTTP
bind ssl vserver lb_vsev_sp -certkeyName sp.josel.net
set ssl vserver lb_vsev_sp -ssl3 DISABLED -tls13 ENABLED

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Adding a pattern-set containing SAML IDPs

Following Citrix CTX316577, we should add a relay-state rule. As there can be several IDPs, I decided to create a patternset.

Navigate to Appexpert → Pattern Sets. Click Create. Add a pattern set called pat_samlIDP. Click insert and add the URL of your IDP in the form https://idp.josel.net/. The trailing / is a must!
add policy patset pat_samlIDP
bind policy patset pat_samlIDP "https://idp.josel.net/" -index 1

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The Citrix ADC / NetScaler SAML Service Provider (SP) Authentication policy

The NetScaler SAML Service provider action (SAML-SP)

GUI: Navigate to:

Security → AAA-Application Traffic  → Policies → Authentication → Basic Policies →  SAML

With SAML Actions click Add.

add authentication samlAction saml_sp_server -samlIdPCertName idp_signing_cert -samlSigningCertName sp_signing_cert_privateKey -samlRedirectUrl "https://idp.josel.net/saml/login" -samlUserField "Name ID" -samlIssuerName josel.net_SP -relaystateRule "AAA.LOGIN.RELAYSTATE.CONTAINS_ANY("pat_samlIDP")"

 

IDP Certificate Name*	SAML IDP’s certificate (we need to own it, but we don’t own it’s private key)
Redirect URL*	The URL of the SAML IDP in use, if IDP is a NetScaler: /saml/login
User Field	User Name in assertion, if IDP is a NetScaler this is Name ID
Signing Certificate Name	a certificate used to sign the SAML assertion (a normal server certificate. We own a private key!)
IDP Certificate Name	the certificate used by the IDP to sign the SAML assertion (a normal server certificate. We don’t own a private key!)
Issuer Name	an ID for this SP. Every SP needs it’s own definition on IDP and this ID is used to match the right definition
Relay State Rule	a list of allowed IDPs, Citrix CTX316577

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The Citrix ADC / NetScaler SAML Service provider policy

GUI: Navigate to:

Security → AAA-Application Traffic  → Policies → Authentication → Advanced Policies →  SAML

add authentication Policy SAML_SP_pol -rule true -action saml_sp_server

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The SAML Service Provider (SAML-SP) Authentication vServer.

Click add

Provide name and IP (port is usually 443, the protocol is SSL and can’t be changed)

bind a server certificate (this one gets exposed to users, so it has to be trusted!)

bind the authentication policy you previously created
add authentication vserver SAML_SP SSL 0.0.0.0
set ssl vserver SAML_SP -ssl3 DISABLED -tls13 ENABLED
bind authentication vserver SAML_SP -policy SAML_SP_pol -priority 100 -gotoPriorityExpression NEXT


Authorization

Since Citrix ADC version 13, default authorization changed to deny. Because of that, access will fail. This may get fixed in two ways: Either change default authorization to allow (I can’t recommend this), or create a session policy, set authorization to allow, and bind it to the AAA vServer.
add authorization policy autho_allow true ALLOW
bind lb vserver lb_vsev_sp -policyName autho_allow -priority 100 -gotoPriorityExpression END -type REQUEST

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Citrix ADC / NetScaler as a SAML Identity Provider (SAML IDP)

A Citrix ADC / NetScaler may also get used as a SAML Identity Provider (SAML-IDP). This allows authenticating to any authentication source like LDAP, RADIUS, Certificates, TACACS, local, Negotiate, O-Auth, SAML, WebAuth, EPA. In my example, I do Citrix ADC / NetScaler local authentication.

Citrix NetScaler ADC is a perfect SAML IDP, a replacement for Microsoft ADFS, both more secure and simpler, to authenticate to Azure and Office 365. There is a Blog by Manuel Wikel, both in German and English, about that subject.

Adding a pattern-set containing SAML SPs

Following Citrix CTX316577, we should add a relay-state rule. As there can be several IDPs, I decided to create a patternset.

Navigate to Appexpert → Pattern Sets. Click Create. Add a pattern set called pat_samlIDP. Click insert and add the URL of your IDP in the form https://sp.josel.net/cgi/samlauth.
add policy patset pat_serviceProviderURLs
bind policy patset pat_serviceProviderURLs "https://sp.josel.net/cgi/samlauth" -index 1

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Creating the a SAML Identity Provider Policy (SAML IDP)

Creating the SAML Identity Provider Action (Saml IDP Action) on a Citrix ADC / NetScaler

Navigate to:

Security → AAA-Application Traffic  → Policies → Authentication → Advanced Policies →  SAML IDP. Go to Profiles.

Click Add.

add authentication samlIdPProfile SAML_IDP_profile -samlSPCertName sp_signing_cert -samlIdPCertName idp_signing_cert_privateKey -assertionConsumerServiceURL "https://sp.josel.net/cgi/samlauth" -samlIssuerName josel.net_IDP -acsUrlRule "AAA.LOGIN.SAML_REQ_ACS_URL.EQUALS_ANY("pat_serviceProviderURLs")"

 

Assertion Consumer Service URL	The logon-URL of the Service provider called consumer (if it’s a Citrix ADC / NetScaler: https://FQFN/cgi/samlauth)
Assertion Consumer Service URL Rule	>a list of SPs, following Citrix CTX316577
IDP Certificate Name	The certificate used to digitally sign the assertion (a normal server certificate, we own the private key)
SP Certificate Name	The certificate used by the service provider, so it can be trusted (IDP does not need to own the private key)
Issuer Name	an ID of the SAML Identity Provider (this SAML IDP’s name). It would be used if SP trusts several IDPs
Service Provider ID	an ID of the SAML Service Provider Each SAML service provider needs to have its own ID IDP profile, so there may be many profiles. This ID is used to find the right definition. (this is an optional parameter and not used in my deployment!)

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The SAML-IDP policy

add authentication samlIdPPolicy saml_IDP_Policy -rule true -action saml_idp

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The authentication policy

I don’t go into authentication policies here. Just follow Citrix’s best practices, there are many guides out there. I created a policy similar to CTX113820.

add authentication Policy local_auth -rule true -action LOCAL
bind authentication vserver aaa_vsrv_test -policy local_auth -priority 100 -gotoPriorityExpression NEXT

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The SAML Identity Provider (SAML-IDP) Authentication vServer.

click add

provide name, IP address, and port, usually 443 (the protocol can’t get changed)

bind a server certificate. This one gets exposed to the user, the user has to trust this certificate!

bind an authentication method and a SAML IDP policy

select both, the IDP and the authentication policy

add authentication vserver aaa_vsrv_test SSL 192.168.1.1 443
set ssl vserver aaa_vsrv_test -ssl3 DISABLED -tls13 ENABLED
bind authentication vserver aaa_vsrv_test -policy samlIdPPolicy -priority 100 -gotoPriorityExpression END
bind authentication vserver aaa_vsrv_test -policy local_auth -priority 100 -gotoPriorityExpression NEXT

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Trouble shooting

I used the following tools:

Citrix NetScaler’s log (Yes, there is a log on a NetSaler, and SAML issues get logged there! You look at /var/log/ns.log)

Firefox add-on SAML-Message Decoder (also available for Chrome)

Citrix NetScaler Network traces

Issues:

I have seen several issues recently:

SAML-SP fails to forward to SAML-IDP

detected: error in the browser

check settings in SAML-SP’s SAML Authentication action: Redirect URL

SAML-IDP fails to forward to SAML-SP

detected: error in the browser

check settings on in SAML-IDP’s SAML-IDP Authentication action: Assertion Consumer Service URL

Certificate not trusted on SAML-IDP

detected: confusing message in the browser, log in IDP’s /var/log/ns.log

add SAML-SP’s signing certificate to SAML-IDP’s SAML-IDP profile: SP-Certificate Name

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Exporting metadata from an SP into the IDP

Usually, in SAML, we configure just one side, export metadata, and import it to the other side. So if we configure the service provider, we can import its metadata into the IDP. That’s the way we do it if the service provider is a Citrix NetScaler ADC:

https://<servername>/metadata/samlsp/<profilename>

Clicking this link, you can import metadata from my SP into an IDP of your choice. More information can be found here. Thanks, Hermann Zauner, for this information!

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I hope. that helps. Just drop me a message if you need more information. You’re very much welcome to link to my blog / my website. Thanks!