SignIn Using Facebook Aspnet core 2.2

SignIn Using Social Logins Aspnet core 2.2

https://docs.microsoft.com/en-us/aspnet/core/security/authentication/social/google-logins?view=aspnetcore-2.2  

https://docs.microsoft.com/en-us/aspnet/core/security/authentication/social/facebook-logins?view=aspnetcore-2.2

Follow the above link to create an app and get the clientId and secret from google. and AppId and App secret from facebook.

Facebook Alone

To integrate login using facebook alone just add the below lines 

In ConfigureServices method

 services.AddAuthentication(op=> {

                op.DefaultChallengeScheme = FacebookDefaults.AuthenticationScheme;

                op.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;

                op.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;

            })

                .AddFacebook(op => {

                    op.AppId = "";

                    op.AppSecret = "";

                })

In Configure method

 app.UseAuthentication();

In the Layout Page

 <ul class="navbar-nav flex-grow-1">

                        @if (User.Identity.IsAuthenticated)

                        {

                            <li class="nav-item">

                                <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Index">Home</a>

                            </li>

                            <li class="nav-item">

                                <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>

                            </li>

                            <li class="nav-item">

                                <a class="nav-link text-dark" asp-controller="auth" asp-action="signOut">SignOut</a>

                            </li>

                        }

                        else

                        {

                            <li class="nav-item">

                                <a class="nav-link text-dark" asp-controller="auth" asp-action="signIn">SignIn</a>

                            </li>

                        }

                        

                    </ul>

The SignIn link will be shown when the User is not signed in and clicking on it will redirect the user to the signIn method in the AuthController.

AuthController

[Route("signin")]

        public IActionResult SignIn()

        {

            return Challenge(new AuthenticationProperties() { RedirectUri="/"});

        }

It is necessary to specify the redirectUri else after login the call there will be an infinite loop as after the user is authenticated the call comes back to the signIn method. So we need to redirect the user from this method once the user is signed in.

 [Route("signout")]

        public async Task<IActionResult> SignOut()

        {

            await HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);

            return RedirectToAction("Privacy","Home");

        }

User claims can be viewed by using the folowing code

<h1>Welcome @User.Identity.Name</h1>

<ul>

    @foreach (var item in User.Claims)

    {

        <li><em>@item.Type : </em> <em> @item.Value</em> </li>

    }

</ul><h1>Welcome @User.Identity.Name</h1>

<ul>

    @foreach (var item in User.Claims)

    {

        <li><em>@item.Type : </em> <em> @item.Value</em> </li>

    }

</ul>

____________________________________________________________________________

Multlple Social Login Providers

To integrate more than one social logins we need to make a few change to the above code.

 services.AddAuthentication(op=> {
                op.DefaultChallengeScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                op.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                op.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            })
                .AddFacebook(op => {
                    op.AppId = "";
                    op.AppSecret = "";
                })
                .AddGoogle(op => {
                    op.ClientId = "1";
                    op.ClientSecret = "";
                })
                .AddCookie(op=> {
                    op.LoginPath = "/auth/signIn";
                });

I have added google authentication to this application. So update the ConfigureServices method to allow google authentication. Notice DefaultChallengeScheme  has been changed to use cookie authentication , so that facebook authentication isnt being used as default.

In the Auth SignIn method we will not be issuing a challenge but redirecting to a view that will give the users the option to select a method to login. Modify SignIn method and add a view called signIn in the Auth Folder under the Views folder.

 [Route("signin")]
        public IActionResult SignIn()
        {
            //return Challenge(new AuthenticationProperties() { RedirectUri="/"});

            return View();
        }

Code for SignIn.Cshtml

@inject Microsoft.AspNetCore.Authentication.IAuthenticationSchemeProvider scheme


@foreach (var item in await scheme.GetRequestHandlerSchemesAsync())
{
    <a class="btn btn-primary login-button" asp-action="SignIn" asp-route-provider="@item.DisplayName">@item.DisplayName</a>

}

We Inject the IAuthenticationSchemeProvider  bcoz we need the registered login schemes.

Once a user click on a Scheme the User is redirected to the screen where  He/She is asked to enter the credentials and upon successful authentication the user is redirected to the Home?index page where all the claims are displayed.