"Unsupported request" Error Logged When Using SAML Authentication

Symptom

The error message "Error in login. Please contact your Administrator." appears when logging into Strategy Web JSP with SAML authentication. 
The following entries are present in the SAML Log: 
org.springframework.security.saml.SAMLProcessingFilter DEBUG - Incoming SAML
message is invalid
org.opensaml.common.SAMLException: Unsupported request
at
org.springframework.security.saml.processor.SAMLProcessorImpl.getBinding(SAMLPr
ocessorImpl.java:265)
at
org.springframework.security.saml.processor.SAMLProcessorImpl.retrieveMessage(S
AMLProcessorImpl.java:172)
at
org.springframework.security.saml.SAMLProcessingFilter.attemptAuthentication(SAM
LProcessingFilter.java:80)
at
com.Strategy.auth.saml.SAMLProcessingFilterWrapper.attemptAuthentication(S
AMLProcessingFilterWrapper.java:22)
at
org.springframework.security.web.authentication.AbstractAuthenticationProcessingF
ilter.doFilter(AbstractAuthenticationProcessingFilter.java:195)
at
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterC
hainProxy.java:342)
com.Strategy.auth.saml.SAMLProcessingFilterWrapper DEBUG - Authentication
request failed:
org.springframework.security.authentication.AuthenticationServiceException:
Incoming SAML message is invalid

Cause

In some circumstances the error occurs because Strategy URLs configured on IDP and Strategy use HTTP, but the load balancer in front of the web server rewrites HTTP requests to HTTPS.

Action

Because the external Strategy URL (load balancer URL) is rewritten to HTTPS, the Strategy URL used in SAML configuration should be HTTPS on the IDP and Strategy side. 
Update all Strategy URLs in SPMetadata.xml and MstrSamlConfig.xml from HTTP to HTTPS. Update the IDP side configuration so that ACS URL is updated from HTTP to HTTPS.