SAML 2.0

Security Assertion Markup Language (SAML) is an XML based way to implement single sign-on (SSO).

A cryptographically signed XML document (known as a “SAML Assertion”) is sent to the API gateway server (Gate) with your identifying information, such as username and group membership.

Gate verifies the XML document’s signature using a metadata file, and if successful, it associates the identifying information with the user and allows the user to proceed as authenticated.

Identity Provider Setup

  1. In your SAML Identity Provider (IdP), download the metadata.xml file. Some providers expose this as a URL. It may look something like this:

     <?xml version="1.0" encoding="UTF-8" standalone="no"?>
     <md:EntityDescriptor 
         xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata"    
         entityID="https://accounts.google.com/o/saml2?idpid=SomeValueHere" 
         validUntil="2021-05-16T15:17:27.000Z">
       <md:IDPSSODescriptor 
           WantAuthnRequestsSigned="false" 
           protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
         <md:KeyDescriptor use="signing">
           <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
             <ds:X509Data>
               <ds:X509Certificate>
     MIIDdDCCAlygAwIBAgIGAVS/Sw5yMA0GCSqGSIb3DQEBCwUAMHsxFDASBgNVBAoTC0dvb2dsZSBJ
     bmMuMRYwFAYDVQQHEw1Nb3VudGFpbiBWaWV3MQ8wDQYDVQQDEwZHb29nbGUxGDAWBgNVBAsTD0dv
     b2dsZSBGb3IgV29yazELMAkGA1UEBhMCVVMxEzARBgNVBAgTCkNhbGlmb3JuaWEwHhcNMTYwNTE3
     MTUxNzI3WhcNMjEwNTE2MTUxNzI3WjB7MRQwEgYDVQQKEwtHb29nbGUgSW5jLjEWMBQGA1UEBxMN
     TW91bnRhaW4gVmlldzEPMA0GA1UEAxMGR29vZ2xlMRgwFgYDVQQLEw9Hb29nbGUgRm9yIFdvcmsx
     CzAJBgNVBAYTblVTMRMwEQYDVQQIEwpDYWxpZm9ybmlhMIIBIjANBgkqhkiG9w0BAQEF46OCAQ8A
     MIIBCgKCAQEA4JsnpS0ZBzb7DtlU7Zop7l+Kgr7NzusKWcEC6MOsFa4Dlt7jxv4ScKZ/61M5WKxd
     5YX0ol1rPokpNztj+Zk7OXrG8lDic0DpeDutc9pcq0+9/NYFF7WR7TDjh4B7Txnq7SerSB78fT8d
     4rK7Bd+cu/cBIyAAyZ5tLeLbmTnHAk093Y9vF3mdWQnfAhx4ldOfstF6G/d2ev7I5xjSKzQuH6Ew
     3bb3HLcM4uEVevOfNAlh1KoV4vQr+qzbc9UEFcPRwzuTwGa6QjfspWW7NgXKbHHC+X6a+gqJrke/
     6l2VvHaQBJ7oIyt4PCdel2cnUkvuxvzHPYedh1AgrIiSP1brSQIDAQABMA0GCSqGSI34DQEBCwUA
     A4IBAQCPqMAIau+pRDs2NZG1nGfyEMDfs0qop6FBa/wTNis75tLvay9MUlxXkTxm9aVxgggjEyc6
     XtDjpV0onrH0jBnSc+vRI1GFQ48EO3owy3uBIeR1aMy13ZwAA+KVizeoOrXBJbvIUZHo0yfKRzIu
     gtM58j58BdAFeYo+X9ds/ysvZ8FIGTLqMl/A3oO/yBNDjXR9Izoqgm7RX0JJXGL9Y1AgmEjxyqo9
     MhxZAGxOHm9HZWWfVMcoe8p62mRJ2zf4lkNPBnDHrQ8MDPSsXewAuiSnRBDLxhdBgyThT/KW7Q06
     rGa6Dp0rntKWzZE3hGQS0AdsnuFY/OXbmkNG9WUrUg5x
               </ds:X509Certificate>
             </ds:X509Data>
           </ds:KeyInfo>
         </md:KeyDescriptor>
         <md:NameIDFormat>urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress</md:NameIDFormat>
         <md:SingleSignOnService 
             Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" 
             Location="https://accounts.google.com/o/saml2/idp?idpid=SomeValueHere"/>
         <md:SingleSignOnService 
             Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" 
             Location="https://accounts.google.com/o/saml2/idp?idpid=SomeValueHere"/>
       </md:IDPSSODescriptor>
     </md:EntityDescriptor>
    
  2. Create a Spinnaker SAML application.
  3. Specify the login URL as https://localhost:8084/saml/SSO. Replace “localhost” with Gate’s address, if known.
  4. Specify a unique entity ID (we’ll use io.spinnaker:test in our example).
  5. Enable the users you’d like to have access to your Spinnaker instance.

TODO: Add halyard commands here when halyard supports SAML

  1. Generate a keystore and key in a new Java Keystore with some password:
    keytool -genkey -v -keystore saml.jks -alias saml -keyalg RSA -keysize 2048 -validity 10000
    
  2. Create or modify your gate-local.yml file to include the following settings:
saml:
  enabled: true
  metadataUrl: file:/opt/spinnaker/config/metadata.xml
  keyStore: file:/opt/spinnaker/config/saml.jks
  keyStorePassword: hunter2
  keyStoreAliasName: saml
  issuerId: io.spinnaker:test
  redirectHostname: localhost:8084

Network Architecture and SSL Termination

During the SAML workflow, Gate makes an intelligent guess on how to assemble a URI to itself, called the Assertion Consumer Service URL. Sometimes this guess is wrong when Spinnaker is deployed in concert with other networking components, such as an SSL-terminating load balancer, or in the case of the Quickstart images, a fronting Apache instance.

To override the values to assemble the URL, use the following hal command:

hal config security authn saml edit --service-address-url https://my-real-gate-address.com:8084

For the Quickstart images, append /gate to the `–service-address-url. All other configurations can omit this setting.

Workflow

The SAML workflow below reflects the process when the user navigates to Spinnaker first, is redirected to the SAML IdP for login, and redirected back to Spinnaker. Some SAML providers will allow the user login to the SAML provider first, and click a link to be taken to Spinnaker.

sequenceDiagram participant Deck participant Gate participant IdentityProvider Deck->>+Gate: GET /something/protected Gate->>-Deck: HTTP 302 to https://idp.url/?SAMLRequest=... Deck->>+IdentityProvider: GET https://idp.url/?SAMLRequest=... IdentityProvider->>-Deck: Returns login page
  1. User attempts to access a protected resource.

  2. Gate redirects to the SAML provider, passing a few query params:
    • SAMLRequest: a Gzip’ed XML authentication request.
    • SigAlg: The algorithm used to generate the Signature parameter.
    • Signature: A digest of the SAMLRequest using the SigAlg algorithm and the server’s key.

    Within the SAMLRequest is the Assertion Consumer Service URL, with is the URL to your Gate instance. See here for how to override this value.

  3. SAML provider prompts user for username & password.
    sequenceDiagram participant Deck participant Gate participant IdentityProvider Deck->>+IdentityProvider: User sends credentials IdentityProvider->>-Deck: HTTP 200 with self-submitting form to POST https://gate.url Deck->>+Gate: POST /saml/SSO with { SAMLResponse: ... } Note right of Gate: User identity verified Note right of Gate: Gate extracts data based on userInfoMapping Gate->>-Deck: HTTP 302 /something/protected
  4. A SAML response must be POSTed to /saml/SSO, and most browsers won’t re-POST when given an HTTP 302. Instead, providers sometimes return a page (with HTTP 200) that has a self-submitting HTML form to POST to Gate’s /saml/SSO endpoint.

  5. Gate verifies the message’s integrity by checking its signature, and thus verifying the user’s identity information.

  6. Gate determines the username and/or email address, and optionally extracts group membership (if sent by the IdP).

  7. With the user’s identity verified, Gate redirects the user to the originally requested URL.

Next Steps

Now that you’ve authenticated the user, proceed to setting up their authorization.

Troubleshooting