vCloud SAML authentication

vCloud have LDAP, SAML and local users as an option for tenant authentication. In this post, we are looking into SAML integration. With AzureAD.

The cool thing about AzureAD is that you will gain the MFA option out of the box, and when tenants want access we can also invite them from their own AzureAD tenant into the resource AzureAD tenant. This gives flexibility and overview of who has access.

ADFS is also an option, but there you need to keep your own infrastructure with a resource AD/ADFS and furthermore need a 3. party MFA solution.

Process:

• Setup Enterprise app in desired resource AzureAD
• Setup claims
• Set federation entity id for tenant
• Import vCloud federation metadata to AzureAD
• Import AzureAD enterprise app federation metadata to vCloud
• Setup allowed users/groups in vCloud

AzureAD

Let’s get started with Azure AD configuration. Login to your AzureAD portal https://portal.azure.com. Navigate to “Azure Active Directory” > “Enterprise App” and press “New Application”. Choose “Non-gallery application”. Give it the name “vCloud SAML test” and press “Add”. This will take a couple of minutes.

Navigate back to “Enterprise Apps” > “All applications” and choose your newly created App.

For test purpose, add/assign a test user to the app. This is under “Users and groups”. This user will be able to login to the enterprise app with AzureAD.

Now go to “Single Sign-on”. This will now ask for the sign-on method, and here we will choose “SAML”. This will then take us to the SAML setup. The first thing to do is importing the metadata from the cloud.

You will find the metadata by logging in to vCloud, go to the tenant, under “administration” > “federation” tab. Enter the URL for the tenant as a entity id, apply and afterwards download the metadata from the link.

In azureAD “Upload Metadata” and chose the downloaded file from vCloud. This will give AzureAD the knowledge of where to redirect and accept request from.

vCloud can validate a couple of user/group parameters. Vmware documentation. So we will add some claims to Azure AD.

Now we will need to download the AzureAD metadata and import into vCloud. Fetch the data by pressing “Download” to the “Federation Metadata XML”.

Head over to vCloud tenant federation page again. Paste the content from the download metadata file. check the “Use SAML identity” and apply. Now we are almost ready to try it out. But first, head over to “Users” tab in vCloud. We need to add the user/role to whom are allowed to gain vCloud Access.

Next step would be to use groups and roles so that we can put users into groups in Azure AD and that way manage access for the tenant. But after this, we can now head to the tenant URL. We will then be redirected to the Azure AD login page, login and accept to MFA so that we can be redirected to our vCloud tenant.

Troubleshooting:

When I first started this project I was using a GUID as a vCloud entity id. That meant that I could get it to work with ADFS but not AzureAD. I went full mole on the troubleshooting.

In the end, I intercepted the SAML responses. These are encoded in base64, easy task to decode. And afterwards, I got the XML that either ADFS or AzureAD is sending back. I could then compare them, and I saw som <ds> tags to the cert that wasn’t on in the response from AzureAD. Unfortunately, that was a duck and meant nothing.

By tailing the log from vCloud, tail -f /opt/vmware/vcloud-director/logs/vcloud-container-debug.log, I could get some hints when the SAML auth failed.

org.opensaml.common.SAMLException: Local entity is not the intended audience of the assertion in at least one AudienceRestriction

doing a bit more googling and found out that I should be looking at the <audience> tag from the two SAML responses. And yes, that made some sense.

Azure AD sets the value of this element to the value of Issuer element of the AuthnRequest that initiated the sign-on. To evaluate the Audience value, use the value of the App ID URI that was specified during application registration.
Like the Issuer value, the Audience value must exactly match one of the service principal names that represents the cloud service in Azure AD. However, if the value of the Issuer element is not a URI value, the Audience value in the response is the Issuer value prefixed with spn:.

https://stackoverflow.com/questions/38978298/azuread-jwt-token-audience-claim-prefix-makes-jwt-token-invalid

And that was the problem, spn: prefix when not using a URL as entity id. Changing it to the URL made it work.

Maybe this is obvious to the world, but I didn’t know it, but glad my troubleshooting skills where sufficient 🙂