This post is about how to implement JWT(JSON web token) authentication in.NET 8.0. Let's first understand what authentication is. Authentication provides a framework for secure delegation of authorization. It enables users to grant access to their resources from one website to another without sharing their credentials. OAuth operates through a series of interactions between three parties: the resource owner (user), the client (application), and the authorization server.

Adding JWT auth to the.NET 8.0 Application.

Note: The following example is based on the .NET 8.0 version.

Step 1: Install Microsoft.IdentityModel.Tokens via NuGet Package Manager. If you want to use NuGet, just search for “Microsoft.IdentityModel.Tokens” or run the following command in the NuGet Package Manager console:

PM> Install-Package Microsoft.IdentityModel.Tokens -Version 7.5.1
PM> Install-Package System.IdentityModel.Tokens.Jwt -Version 7.5.1
PM> Install-Package Microsoft.AspNetCore.Authentication.JwtBearer -Version 8.0.4

This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of  Install-Package.

Step 2: Once the installation is done, we need to add the following line of code in the startup.cs file.

builder.Services.AddSwaggerGen(option =>
{
    option.SwaggerDoc("v1", new OpenApiInfo { Title = "JWTToken", Version = "v1", Description = "An ASP.NET Core Web API for JWTToken" });
    option.AddSecurityDefinition("Bearer", new OpenApiSecurityScheme
    {
        In = ParameterLocation.Header,
        Description = "Please enter a valid token",
        Name = "Authorization",
        Type = SecuritySchemeType.Http,
        BearerFormat = "JWT",
        Scheme = "Bearer"
    });
    option.AddSecurityRequirement(new OpenApiSecurityRequirement
                {
                    {
                        new OpenApiSecurityScheme
                        {
                            Reference = new OpenApiReference
                            {
                                Type=ReferenceType.SecurityScheme,
                                Id="Bearer"
                            }
                        },
                        new string[]{}
                    }
                });
});

 builder.Services.AddAuthentication(opt => {
    opt.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    opt.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
})
.AddJwtBearer(options =>
{
    options.TokenValidationParameters = new TokenValidationParameters
    {
        ValidateIssuer = true,
        ValidateAudience = true,
        ValidateLifetime = true,
        ValidateIssuerSigningKey = true,
        ValidIssuer = builder.Configuration["JWT:ValidIssuer"],
        ValidAudience = builder.Configuration["JWT:ValidAudience"],
        IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(builder.Configuration["JWT:Secret"]))
    };
}); 

You configure Swagger generating services when you use AddSwaggerGen in the Program.cs file of your ASP.NET Core application inside the ConfigureServices function..

Step 3: We are going to add AuthController file under the Controllers folder.

public IActionResult Login([FromBody] UserModel user)
{
    if (user is null)
    {
        return BadRequest("Invalid user request!!!");
    }
    if (userRepository.CheckUserExist(user))
    {
        var secretKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(configuration["JWT:Secret"]));
        var signinCredentials = new SigningCredentials(secretKey, SecurityAlgorithms.HmacSha256);
        var tokeOptions = new JwtSecurityToken(
            issuer: configuration["JWT:ValidIssuer"],
            audience: configuration["JWT:ValidAudience"],
            claims: new List(),
            expires: DateTime.Now.AddMinutes(60),
            signingCredentials: signinCredentials
        );
        var tokenString = new JwtSecurityTokenHandler().WriteToken(tokeOptions);
        return Ok(new AuthResponseModel { Token = tokenString });
    }
    return Unauthorized();
}

Now, run the project and see how it works.

Download Source Code: GitHub Repository