Encountering 302 Redirect Issue When Frontend Calls Backend APIs Integrated with Okta SAML 2.0

[VikasHi]

I’m experiencing a peculiar issue with 302 redirects when making API calls from the frontend to the backend, which is integrated with Okta using SAML 2.0 for authentication. Here’s the breakdown of the scenario:

→ Current State:

Okta handles SAML 2.0 authentication with the backend. When accessing the backend APIs individually via the browser URL bar, I receive the expected API response without any 302 redirects. However, when the frontend makes similar API requests to the backend, it encounters a 302 status code (redirect) instead of the expected API response.

→ Observations:

The frontend isn’t directly involved in handling SAML assertions; it’s a backend-to-Okta setup.

→ Troubleshooting Attempts:

Verified backend configurations for Okta integration. Reviewed network requests and responses through browser tools, noting no issues when accessing the backend APIs directly.

Why might the 302 redirects occur only when the frontend communicates with the backend APIs integrated with Okta’s SAML 2.0, despite successful individual access to the same APIs via the browser? Any insights or guidance on identifying potential causes or troubleshooting steps to resolve this redirect issue would be highly appreciated.

Backend code for reference

    
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
        .authorizeRequests(authorize ->
            authorize.anyRequest().authenticated()
        ).saml2Login()
        // Your SAML 2.0 configuration
        .and()
    // Disable CSRF
    .csrf().disable()
    // Disable CORS
    .cors().disable();

        // add auto-generation of ServiceProvider Metadata
        Converter<HttpServletRequest, RelyingPartyRegistration> relyingPartyRegistrationResolver = new DefaultRelyingPartyRegistrationResolver(relyingPartyRegistrationRepository);
        Saml2MetadataFilter filter = new Saml2MetadataFilter(relyingPartyRegistrationResolver, new OpenSamlMetadataResolver());
        http.addFilterBefore(filter, Saml2WebSsoAuthenticationFilter.class);
    }

    @Bean
    protected RelyingPartyRegistrationRepository relyingPartyRegistrations() throws Exception {
        Resource resource = new ClassPathResource("saml-certificate/okta.crt");

        if (!resource.exists()) {
            throw new FileNotFoundException("Certificate file not found");
        }

        try (InputStream inputStream = resource.getInputStream()) {
            CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
            X509Certificate certificate = (X509Certificate) certFactory.generateCertificate(inputStream);
            Saml2X509Credential credential = Saml2X509Credential.verification(certificate);

            RelyingPartyRegistration registration = RelyingPartyRegistration
                    .withRegistrationId(registrationId)
                    .assertingPartyDetails(party -> party
                            .entityId(entityId)
                            .singleSignOnServiceLocation(singleSignOnServiceLocation)
                            .wantAuthnRequestsSigned(false)
                            .verificationX509Credentials(c -> c.add(credential))
                    ).build();

            return new InMemoryRelyingPartyRegistrationRepository(registration);
        }

    }
    
}

Put plainly, the backend is linked up with Okta’s SAML 2.0, while the frontend attempts to access the backend’s API. However, the frontend’s API calls are hitting a roadblock at the 302 stage, preventing them from fetching the API response despite successful authentication. What steps should the frontend take to successfully retrieve the backend’s response?

Thank you for your assistance!