Q: Can We use SOAP (back-channel) binding instead of POST/Redirect in Spring SAML?
A: No. Spring Security SAML, both legacy and current SAML2, only supports HTTP-Redirect and HTTP-POST bindings. SOAP binding is not supported (yet).
Archived docs by Vladimír Schäfer: SOAP not available.
Current logout docs by Vladimír Schäfer: SOAP not available.
docs.spring.io/spring-security-saml
"I read in the documentation about back-channel SOAP calls, and that sounds like exactly what I want, but I can't find anything on it."
You're right in thinking that there should be documentation on it, there're many, example. Just none for spring saml. Have a nice one.
Cheers to the Mods 🍺