@Override
    public List<Credential> fromAuthentication(final HttpServletRequest request,
                                               final MultiValueMap<String, String> requestBody,
                                               final Authentication authentication,
                                               final MultifactorAuthenticationProvider provider) {
        val principal = authentication.getPrincipal();
        val credential = new DuoSecurityDirectCredential(principal, provider.getId());
        val credentialMetadata = new BasicCredentialMetadata(credential);
        credentialMetadata.setTenant(tenantExtractor.extract(request).map(TenantDefinition::getId).orElse(null));
        return List.of(prepareCredential(request, credential));
    }
Identifier for the duo mfa provider.
support/cas-server-support-duo-core-mfa/src/main/java/org/apereo/cas/adaptors/duo/rest/DuoSecurityRestHttpRequestCredentialFactory.java