IDP role HTTP-Redirect binding support broken by SameSite LAX cookies filter

• Type: Regression Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 7.0.X, 7.1.X, 7.2.X, 7.3.X, Master
• Fix Version/s: 7.0.X, 7.1.X, 7.2.X, 7.3.X, Master
• Component/s: Application Security > SAML
• Labels: None
• Branch Version/s:
  7.3.x, 7.2.x, 7.1.x, 7.0.x
• Backported to Branch:
  Committed
• Fix Priority: 4
• Sprint: Iteration 49, Iteration 50
• Git Pull Request: https://github.com/liferay-appsec/liferay-portal/pull/158

The filter converts the HTTP-Redirect binding's GET request into a POST request when it builds an auto-submitting HTML form.

Steps to reproduce.

1. Configure portal as SAML IDP
2. Clear all cookies for portal
3. Using a SAML SP which supports sending HTTP-Redirect binding Authn Requests (another portal instance is fine), initiate SSO using this binding.

 Expected result: The user lands on the portal/IDP's login screen

 Actual result: Generic SAML processing error is shown on UI

 Tip: If using portal as SP, you can download the portal IDP's SAML metadata and manually remove the HTTP-POST binding ACS support declaration. i.e.  

<md:AssertionConsumerService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" Location="http://liferaysamlsp.com:8080/c/portal/saml/acs" index="1" isDefault="true"/>

Save to an .xml file and upload via the portal's IDP connection configuration screen. This will prevent portal from sending HTTP-Post messages the the IDP. It will instead use other bindings that are declared. Which should only be HTTP-Redirect . i.e. 

<md:AssertionConsumerService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" Location="http://liferaysamlsp.com:8080/c/portal/saml/acs" index="1" isDefault="true"/>