A rich client performs single sign-on (SSO) to access a web- or cloud-based application. According to the described SSO approach, the rich client delegates to its native application server the task of obtaining a credential, such as a SAML assertion. The native server, acting on behalf of the user, obtains an assertion from a federated identity provider (IdP) that is then returned to the rich client. The rich client provides the assertion to a cloud-based proxy, which presents the assertion to an identity manager to attempt to prove that the user is entitled to access the web- or cloud-based application using the rich client. If the assertion can be verified, it is exchanged with a signed token, such as a token designed to protect against cross-site request forgery (CSRF). The rich client then accesses the web- or cloud-based application making a REST call that includes the signed token. The application, which recognizes the request as trustworthy, responds to the call with the requested data.