mithilesh kumar singh

If you want to generate a JWT token without adding predefined claims like ClaimTypes.Role and only using the input values (client_id, client_secret, and grant_type), follow these steps:

Program.cs

using Microsoft.AspNetCore.Authentication.JwtBearer;

using Microsoft.IdentityModel.Tokens;

using System.Text;

var builder = WebApplication.CreateBuilder(args);

var key = "your_super_secret_key"; // Use a secure key in production

builder.Services.AddControllers(); 

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)

    .AddJwtBearer(options =>

    {

        options.TokenValidationParameters = new TokenValidationParameters

        {

            ValidateIssuerSigningKey = true,

            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(key)),

            ValidateIssuer = false,

            ValidateAudience = false

        };

    });

builder.Services.AddAuthorization();

var app = builder.Build();

app.UseAuthentication();

app.UseAuthorization();

app.MapControllers();

app.Run();

Define the input model in a file, e.g., Models/TokenRequest.cs:

public class TokenRequest

{

    public string ClientId { get; set; }

    public string ClientSecret { get; set; }

    public string GrantType { get; set; }

}

Create a controller AuthController.cs inside Controllers folder:

using Microsoft.AspNetCore.Mvc;

using Microsoft.IdentityModel.Tokens;

using System.IdentityModel.Tokens.Jwt;

using System.Text;

[Route("api/auth")]

[ApiController]

public class AuthController : ControllerBase

{

    private readonly string _key = "your_super_secret_key"; // Use a secure key in production

    [HttpPost("token")]

    public IActionResult GenerateToken([FromBody] TokenRequest request)

    {

        // Validate client credentials (You can replace this with database validation)

        if (request.ClientId != "my-client-id" || request.ClientSecret != "my-secret" || request.GrantType != "client_credentials")

        {

            return Unauthorized(new { message = "Invalid client credentials" });

        }

        // Generate JWT Token

        var tokenHandler = new JwtSecurityTokenHandler();

        var keyBytes = Encoding.UTF8.GetBytes(_key);

        var tokenDescriptor = new SecurityTokenDescriptor

        {

            Expires = DateTime.UtcNow.AddHours(1), // Token expires in 1 hour

            SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(keyBytes), SecurityAlgorithms.HmacSha256Signature)

        };

        var token = tokenHandler.CreateToken(tokenDescriptor);

        var jwt = tokenHandler.WriteToken(token);

        return Ok(new { access_token = jwt, token_type = "Bearer", expires_in = 3600 });

    }

}