token := r.Form.Get(stsToken)
	if token == "" {
		token = r.Form.Get(stsWebIdentityToken)
	}

	accessToken := r.Form.Get(stsWebIdentityAccessToken)

	// RoleARN parameter processing: If a role ARN is given in the request, we
	// use that and validate the authentication request. If not, we assume this
	// is an STS request for a claim based IDP (if one is present) and set
	// roleArn = openid.DummyRoleARN.