Silent Auto-Login for User after Completing 'Authentication API'-Backed Custom Signup Form

I currently have a web application that is secured with Auth0 via a Regular Web Application. The Auth0 Application uses a standard credentialed Universal Login form for user authentication, with a Database Connection.

For user registrations, I have a custom signup form written in C# that uses the .NET Auth0 SDK. It creates a new Auth0 user in the Database Connection via the Management API.

I’m trying to add the ability for the custom signup form to redirect the user to my secured web application after a successful signup, and have them pre-logged in. Right now, when they complete the signup form, they are sent to the web application, but they have to re-enter their credentials on the Auth0 Login page to proceed (Bad user experience, since they just entered this 5 seconds ago).

So far, I’ve looked at alternative methods of authentication supported by Auth0.

  • Passwordless Authentication - Requires user to receive email or text and take additional actions to login, more cumbersome than them just logging in, in this use case
  • Single Sign-On - Not applicable, still requires user to login once, only useful when navigating to different applications once already logged in
  • Silent Authentication - Not applicable, still requires user to login once, only useful after initial login
  • Resource Owner Password Grant (Authentication API) - Tried looking into taking the username and password and calling an API endpoint to authenticate the user, once the user is created. The Authentication API service that does this only generates an access_token to be used for secured API calls, I have not found a way to use this token to authenticate access to a Standard Web Application.
  • Signup API - I found references to using the Signup service (/dbconnections/signup) in the Authentication API to register users, instead of the Create User service that I currently use in the Management API. I haven’t found information in the documentation around being able to redirect the user to the web application in a logged in state using the Signup service, so this seemed like a dead end (I could have missed something).
  • Rules - Tried looking into creating an Auth0 rule to accomplish this, but couldn’t find a way
  • Login Form Defaults - Similar to above

I found a few previous posts on this that never seemed to get answered: auth0-user/21362

There were some other semi-related posts like this one, as well, that didn’t seem to end with a meaningful solution:

Appreciate the help with this. I’m open to changing around how my signup/login flow works if needed, but after a few hours without much headway, I’m a little stuck on whether there are any options available at all. Overall, love everything Auth0 provides since implementing a few months ago.


Bump - has anyone had success with auto logging in a user after they complete a signup form?

1 Like

1 more bump - anyone know if this feature is present? I can do a feature request if not.

I created support ticket #00437181 for this. I’ll post updates here when I get them.

Thanks a lot! Let us know about the progress of the ticket

I got a response to my ticket last month, but it wasn’t immediately clear to me what the recommendation was, and I have been working on other app features since then. I was able to get back to this today, and got it working.

To do this, you’ll want to make use of standard ASP.NET infrastructure to sign in the user server-side. My current solution may not be perfect, but it works.

  1. After a user completes the sign-up process on my custom sign up form, I redirect them to a new endpoint on my secured application (e.g. This endpoint is setup to allow anonymous requests, so the user is not prompted for login credentials via the Auth0 login form. I have the sign up form pass an authorization query parameter to this endpoint, which contains the user’s username and password.

  2. This authLogin endpoint parses the user credentials passed into it and calls the GetToken method in the Auth0 Authentication API (Resource Owner Password flow).

  3. If the GetToken method returns a populated AccessToken, the endpoint creates a Cookie-based ClaimsIdentity with the user’s username, and calls HttpContext.SignInAsync. SignInAsync generates the Authentication Cookies that Auth0 needs to confirm user identity (Everything needed for it to do this is pre-setup in Startup.cs, as per the standard Auth0 + ASP.NET integration).

  4. With the cookies generated, the user is redirected to the secured site home page, in a logged-in state, with no login form presented. Works like a charm.

Some notes before I include some code for anyone interested:

  • You’ll want to use the ‘auth0-forwarded-for’ parameter to send Auth0 the client’s IP address when calling GetToken, as per their recommendation. Just be careful with this, since client IPs can be spoofed by evil-dooers. A well-configured proxy in front of your secured site will help with this. I’m still getting this part properly secured, so treat that part of the code below with a grain of salt. Further reading on this here and here.

  • I’m sure there are better ways to setup this server-side, cookie-based authorization/authentication. ASP.NET has some cool options with adding Middleware to structure this kind of thing better (info here)

  • I have not completed security hardening this code, there are definitely some issues with it. Although untested, I may change everything around so my custom signup form is setup with everything it needs to perform a HttpContext.SignInAsync and generate the Auth0 cookies directly, to reduce the number of handoffs the user’s credentials endures. Also, I’m only passing the user’s credentials via a query parameter because I was having CORS/cross-site security issues with using the Authorization Header; the Header would be the preferred mechanism. It’s probably not great to have the password stored in a string instead of a SecuredString, too.

Anyway, here you go:

	public async Task<IActionResult> autoLogin([FromQuery] string authorization)

		//TODO - Can all of this be done in Sign Up form, instead of Secured Site, so no need for all this crazy passing around of credentials?
		string[] credentials = getCredentialsFromHeader(authorization);
		bool authorizedAttempt = await authorizeBasicLoginAttempt(credentials, HttpContext);
		if (authorizedAttempt)

			await logInUser(credentials[0], HttpContext);


		return Redirect(Url.Action("home", "HomePage"));


	private static string[] getCredentialsFromHeader(string authorizationHeader)

		string[] credentials = new string[] { "", "" };

		if (authorizationHeader != null && authorizationHeader.StartsWith("Basic "))

			string decodedCredentials = (getBasicAuthDecodedCredentials(authorizationHeader));
			credentials = splitBasicAuthDecodedCredentials(decodedCredentials);


		return credentials;


	private static string getBasicAuthDecodedCredentials(string authorizationHeader)

		string encodedCredentials = authorizationHeader.Replace("Basic ", "");
		byte[] decodedCredentialBytes = Convert.FromBase64String(encodedCredentials);

		return Encoding.UTF8.GetString(decodedCredentialBytes);


	private static string[] splitBasicAuthDecodedCredentials(string decodedCredentials)

		string[] splitCredentials = new string[] { "", "" };

		int credentialSeperatorIndex = decodedCredentials.IndexOf(':');

		if (credentialSeperatorIndex > -1)

			splitCredentials[0] = decodedCredentials.Substring(0, credentialSeperatorIndex);
			splitCredentials[1] = decodedCredentials.Substring(credentialSeperatorIndex + 1);


		return splitCredentials;


	private static async Task<bool> authorizeBasicLoginAttempt(string[] credentials, HttpContext httpContext)

		bool authorized = false;

		//TODO - Research the security behind this and improve as needed. Getting the actual client IP is a little tricky, can be spoofed. Cloudflare has a "True-Client-IP header for enterprise users. Other options?
		string clientIpAddress = httpContext.Connection.RemoteIpAddress.ToString();

		ResourceOwnerTokenRequest authenticationRequest = buildResourceOwnerAuthenticationRequest(credentials, clientIpAddress);
		AuthenticationApiClient authenticationClient = new AuthenticationApiClient(AUTH0_DOMAIN);


			AccessTokenResponse authenticationResponse = await authenticationClient.GetTokenAsync(authenticationRequest);
			if (String.IsNullOrEmpty(authenticationResponse.AccessToken) == false)

				authorized = true;


		} catch (AuthenticationException ae)



		return authorized;


	private static ResourceOwnerTokenRequest buildResourceOwnerAuthenticationRequest(string[] credentials, string clientIpAddress)

		ResourceOwnerTokenRequest resourceOwnerAuthenticationRequest = new ResourceOwnerTokenRequest();

		resourceOwnerAuthenticationRequest.ClientId = AUTH0_CLIENT_ID;
		resourceOwnerAuthenticationRequest.ClientSecret = AUTH0_CLIENT_SECRET;
		resourceOwnerAuthenticationRequest.ForwardedForIp = clientIpAddress;
		resourceOwnerAuthenticationRequest.Username = credentials[0];
		resourceOwnerAuthenticationRequest.Password = credentials[1];

		return resourceOwnerAuthenticationRequest;


	private static async Task logInUser(string username, HttpContext httpContext)

		List<Claim> userClaims = new List<Claim>();
		userClaims.Add(new Claim(ClaimTypes.Name, username));
		userClaims.Add(new Claim(ClaimTypes.Email, username));

		ClaimsIdentity userClaimsIdentity = new ClaimsIdentity(userClaims, CookieAuthenticationDefaults.AuthenticationScheme);

		await httpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, new ClaimsPrincipal(userClaimsIdentity), new AuthenticationProperties());

1 Like

Hey @Grant-Hoover! I’m chiming in with an alternative approach.

What I would do is simply create the session for the user after the signup, without doing the resource owner password grant token exchange. E.g.:

public async Task<IActionResult> SignUp(NewUserData user)
  // this is your process that calls Management API v2 
  // to create the user and any other necessary tasks
  var createUserResult = await CreateUser(user);
  // Everything's good, now go ahead and sign the user in
  var claims = new List<Claim>
      new Claim(ClaimTypes.Email, user.Email),
      new Claim(ClaimTypes.Name, user.Name),
      new Claim(ClaimTypes.NameIdentifier, user.UserId),
      [...] // whatever claim you have either from the user form
            // or from the response from the Management API v2

  var claimsIdentity = new ClaimsIdentity(
      claims, CookieAuthenticationDefaults.AuthenticationScheme);

  await HttpContext.SignInAsync(
    new ClaimsPrincipal(claimsIdentity));

  return this.Redirect("/");


1 Like

Thanks for the suggestion. I’m currently doing the Resource Owner Password grant because I’m having an application that is separate from the sign-up form application perform the SignInAsync call, and that separate application is receiving the user login credentials via an unsecured web endpoint. The password grant is simply to ensure proper security is in place (Otherwise, anyone calling the endpoint could enter a user ID with an invalid password).

Like I mentioned in my post, I will be attempting to update the logic flow to have the sign-up form application perform the SignUpAsync call directly, then redirect to the secured application with the cookies pre-generated, removing the need for the password grant validation (Since the user is already verified in the eyes of the sign-up form application).

I wasn’t sure how long it would be before I got back to this, so I wanted to get something functional up on this post at a minimum, but I definitely like your approach better (Simpler, more secure, etc). I’ll post an update when I try to implement the improved logic flow.



Thank you a lot for that for sharing all that knowledge with the rest of community here!

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