AWS Cognito Signin returning Bad gateway error

Question

My.Net Core application is published to an elastic beanstalk load balanced environment and I'm using the Cognito hosted UI for authentication but after entering correct login details I get a 502 error.

snippet from startup.cs

        services.AddAuthentication(options =>
        {
            options.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            options.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            options.DefaultSignOutScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            options.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;                
        })
        .AddCookie()
        .AddOpenIdConnect(options =>
        {
            options.ResponseType = Configuration["Authentication:Cognito:ResponseType"];
            options.MetadataAddress = Configuration["Authentication:Cognito:MetadataAddress"];
            options.ClientId = Configuration["Authentication:Cognito:ClientId"];
            options.SaveTokens = true;
            options.ClientSecret = Configuration["Authentication:Cognito:Secret"];
            options.Scope.Add(Configuration["Authentication:Cognito:Scope"]);
            options.Events = new OpenIdConnectEvents()
            {
                OnRedirectToIdentityProviderForSignOut = OnRedirectToIdentityProviderForSignOut,
                OnRedirectToIdentityProvider = (async context =>
                {
                    context.ProtocolMessage.RedirectUri = context.ProtocolMessage.RedirectUri.Replace("http:", "https:");
                    await Task.FromResult(0);
                })
            };
        });

When I inspect the.network activity in the browser I'm seeing this... ...which suggests that cognito is redirecting to /signin-oidc but there's no authorisation so it redirects back to cognito which then redirects back, and this repeats until it eventually throws the 502 error.

When I'm testing locally I'm able to login okay which makes me think it's maybe some kind of loadbalancing issue??

Answer 1

I kept getting a Bad Gateway 502 until I discovered that my next.config.js had async rewrites enabled for the source/destination URLs in my clumsy attempt to fix a CORS issue. Removing that fixed my problem to get next-auth working with cognito. Then I had to fix the underlying CORS problem with server side policy settings.