How to create JWT Token authorization in ASP.NET Core 2.0 Project.

Hello

Today I want to present how to make custom JWT Tokens authorization in ASP.NET Core 2.0 project.

JSON Web Tokens it is an open standard that allows transmitting data between parties as a JSON object in a compact and secure way. They are usually used in authentication and information exchange scenarios.

First of all we have to create new project:

I'm using Visual Studio 2017 Community.

At the beginning we have to download and install library with JWT. I recommend you use Nuget.
So, we have to find: Microsoft.AspNetCore.Authentication.JwtBearer it is library from Microsoft to manage JWT.

Then in our appsetings.json:

we have to create section witch will be responsible for our Token settings:

{
  "Logging": {
    "IncludeScopes": false,
    "Debug": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
    "Console": {
      "LogLevel": {
        "Default": "Warning"
      }
    }
  },
  "Token": {
    "Key": "SuperSecretKey1234%",
    "ExpireMinutes": "5"
  }
} 

Then we have to go to Startup.cs:

and write this code:

 services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
                .AddJwtBearer(options =>
                {
                    options.TokenValidationParameters = new TokenValidationParameters()
                    {
                        ValidateLifetime = true,
                        ValidateIssuerSigningKey = true,
                        ValidateAudience = false,
                        IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["Tokens:Key"]))
                    };
                });

Its mean that we will use authentication and it will be JWT authentication. What is more in this function we can define how our verification will looks like. I defined that our token will be verified by time and secret key.

 app.UseAuthentication();

When we have defined our token settings, we can start creating our tokens!

Let's make class and name it: JwtHandler. In this class we will have just one method: Create Token.

This method should looks like this:

public class JwtHandler : IJwtHandler
    {
        private readonly IConfiguration _configuration;

        public JwtHandler(IConfiguration configuration)
        {
            _configuration = configuration;
        }

        public JwtDTO CreateToken(Guid userId, string role)
        {
            var now = DateTime.UtcNow;
            var claims = new Claim[]
            {
                new Claim(JwtRegisteredClaimNames.Sub, userId.ToString()),
                new Claim(JwtRegisteredClaimNames.UniqueName, userId.ToString()),
                new Claim(ClaimTypes.Role, role),
                new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
                new Claim(JwtRegisteredClaimNames.Iat, now.ToTimeStamp().ToString(), ClaimValueTypes.Integer64),
            };

            var signingCredentials = new SigningCredentials(
                new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_configuration["Token:Key"]))
                , SecurityAlgorithms.HmacSha256);

            var expiry = now.AddMinutes(double.Parse(_configuration["Token:ExpireMinutes"]));

            var jwt = new JwtSecurityToken(
                claims: claims,
                notBefore: now,
                expires: expiry,
                signingCredentials: signingCredentials
            );

            var token = new JwtSecurityTokenHandler().WriteToken(jwt);

            return new JwtDTO()
            {
                Token = token,
                Expiry = expiry.ToTimeStamp()
            };
        }
    }

That is all, we have created authorization with JWT Tokens. When we have use it, we have to attribut [Authorize] to our method in Controller. Like this:

[HttpGet]
[Route("auth")]
[Authorize]
public IActionResult GetAuth()
{
      return Content("This method require authorization");
}

If you like this tutorial please give a Like.

Thanks!

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