I implement an saml identity provider, The servise provider send an HTML from that containt the authnRequest in an hide input, that have a name for example SAMLRequest.
<form id="samlRequestId" action="http://localhost:8084/IdentityProvider/SSOService" method="post">
<input type="hidden" name="RelayState" value="token" />
<input type="hidden" name="SAMLRequest" value="samlRequestValue"</input>
</form>
But how the IdP know this name(SAMLRquest), actually I hard coded this name, I ask if there are any other method?
The attribute name "SAMLRequest" is defined as part of the SAML 2.0 standard. You can find more details about it in http://docs.oasis-open.org/security/saml/v2.0/saml-bindings-2.0-os.pdf, it's in chapter 3.4 HTTP Redirect Binding.