· Apr 30, 2019

Securing Web Service with SAML - Example?


I have a very simple web service that I'd like to secure via SAML Authorization with X.509 Certificates. I am, however struggling with documentation and my lack of cryptographic skills. (I do this just for educational purposes now, but need to use it in the future)

Does anyone have an example that shows how to construct a SOAP Client with adding all necessary security headers manually or point me to a decent learning resource?


Thank you very much!

Discussion (1)1
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So, at the end I found the answer and I'm going to share it with the audience, in case someone may have the same issue.

But before I provide code, a few more words about SOAP service. 

The SOAP service has just one  method - Test. It accepts a string and returns another string. That's it. I then created a WS Policy via Wizard, this policy is using SAML Authorization with X.509 Certificates. (no ws addressing,  no body / token protection, and recipient token using X.509 credentials to keep my example simple)

I then generated a SOAP client, based on WSDL produced by the above service.

and here is the code:

Class WSC.ClientTest Extends %RegisteredObject

/// d ##class(WSC.ClientTest).Run(2)
ClassMethod Run(pValue As %String = 0)
    set tClient=##class(WSC.SecureDemo.MySecuredServiceSoap).%New()
    set tClient.SSLConfiguration="SELF-MASTER"
       In real life, we would retrieve a SAML Assertion token from 
       an IDENTITY PROVIDER - IdP - and just pass it to the web service.
       The WebService (SERVICE PROVIDER / SeP) (unauthenticated 
       or using a technical account on Cache server side) 
       would need to retrieve the SAML Assertion from SOAP Header 
       and perform its validation
    *    This is a dummy code to construct a SAML token...      *
    set tCred = ##class(%SYS.X509Credentials).GetByAlias("SAML-DEMO","norway01")
    // Create the SAML Assertion token object - this is just a form of X509 certificate
    #dim tSamlAssertion As %SAML.Assertion = ##class(%SAML.Assertion).CreateX509(tCred)
    set tSamlAssertion.IssueInstant = $zdt($h,3,,3)
    // in real life we would receive this data from IdP !!!
    #dim tName As %SAML.NameID = ##class(%SAML.NameID).%New()
    set tName.NameID = "https://DESKTOP-Q224QPV"    // saml token issuer, in this case it's me, my computer :)
    set tSamlAssertion.Issuer = tName
    set tSub = ##class(%SAML.Subject).%New()
    #dim tName2 As %SAML.NameID = ##class(%SAML.NameID).%New()
    set tName2.NameID = ""
    set tSub.NameID = tName2
    set tSamlAssertion.Subject = tSub
    #dim tAuthSt As %SAML.AuthnStatement = ##class(%SAML.AuthnStatement).%New()
    set tAuthSt.AuthnInstant = $zdt($h,3,,3)
    // SAML conditions - make sure SAML token is not valid too long...
    set tNow=$h
    set tConditions=##class(%SAML.Conditions).%New()
    set tConditions.NotBefore=$zd($p(tNow,",",1),3)_" "_$zt(($p(tNow,",",2)-30),1)
    set tConditions.NotOnOrAfter=$zd($p(tNow,",",1),3)_" "_$zt(($p(tNow,",",2)+900),1)
    set tSamlAssertion.Conditions=tConditions
    // Attribute statements
    #define AddAttribute(%key,%value,%nf) set tAttribute = ##class(%SAML.Attribute).%New() ##continue
        set tAttribute.Name=%key ##continue
        set tAttributeValue = ##class(%SAML.AttributeValue).%New() ##continue
        set tAttribute.NameFormat = %nf ##continue
        do tAttribute.AttributeValue.Insert(tAttributeValue) ##continue
        do tAttributeStatement.Attribute.Insert(tAttribute)
    #define AddStringAttribute(%key,%value,%nf) $$$AddAttribute(%key,%value,%nf) Do tAttributeValue.SetString(%value)
    #define AddElementAttribute(%key,%value,%nf) $$$AddAttribute(%key,%value,%nf) Do tAttributeValue.SetElement(%value)
    set tAttributeStatement=##class(%SAML.AttributeStatement).%New()
    $$$AddStringAttribute("name","Daniel Kutac","")
    $$$AddStringAttribute("division","Sales Organization","")
    do tSamlAssertion.Statement.Insert(tAttributeStatement)
    *     End SAML Assertion data        *
    // add SAML Token to SOAP Header
    do tClient.SecurityOut.AddToken(tSamlAssertion)
    // add WS timeStamp, this is needed by WS Security policy
    set tTS=##class(%SOAP.Security.Timestamp).Create()
    do tClient.SecurityOut.AddSecurityElement(tTS)
    // this would be, in real life, a technical account, or even unauthenticated CSP application
    set tUToken=##class(%SOAP.Security.UsernameToken).Create("kutac","xxx")
    do tClient.SecurityOut.AddSecurityElement(tUToken)
    // response has - per policy - signed body, we only display result, if signature is valid
    #dim e as %Exception.AbstractException
    try {
        write !," result: ",tClient.Test(pValue)
    } catch (e) {
        if $ZERROR["<ZSOAP>" {
            w !,"SOAP FAULT ERROR:",!
            d $System.OBJ.DisplayError(%objlasterror)
        } else {
            w !,"Other error:",!,e.DisplayString()

one more comment: you may need to implement OnPreWebMethod() method in the SOAP service where you validate incoming SAML assertion token.