Here are the steps to implement JWT authentication in ASP.NET Core 6

Step 1: Install the required NuGet packages To get started with JWT authentication in ASP.NET Core 6, you need to install the following NuGet packages:

• Microsoft.AspNetCore.Authentication.JwtBearer
• Microsoft.IdentityModel.Tokens

You can install these packages using the NuGet Package Manager in Visual Studio, or by running the following commands in the Package Manager Console

Install-Package Microsoft.AspNetCore.Authentication.JwtBearer

Install-Package Microsoft.IdentityModel.Tokens

Step 2: Configure JWT authentication in your app
In your ASP.NET Core 6 app, open the Program.cs file and add the following code inside the ConfigureServices method:

                            
                                
  builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme).AddJwtBearer(options =>
    {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidateAudience = true,
            ValidateLifetime = false,
            ValidateIssuerSigningKey = true,
            ValidIssuer = "Jwt:Issuer",
            ValidAudience = "Jwt:Audience",
            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("Jwt:Key"))
        };
    });
    
                            
                        

This code configures the JWT authentication middleware for your app and sets up the options for token validation. You'll need to replace the values for Jwt:Issuer, Jwt:Audience, and Jwt:Key with your own values.

And also add

                            
                                
  app.UseAuthentication();
  
                            
                        

Step 3:Add authorization to your API endpoints
To protect your API endpoints with JWT authentication, you need to add the [Authorize] attribute to your controller or action methods. For example:

                            
                                 
  [Authorize]
  [HttpGet]
  public string HelloWorld()
  {
      return "HelloWorld";
  }

                            
                        

This code adds the [Authorize] attribute to the Get method, which means that only authenticated users with a valid JWT token can access this endpoint.

Generate JWT tokens To generate JWT tokens for your users, you can use a library like
System.IdentityModel.Tokens.Jwt.
Here's an example of how to generate a JWT token:

                            
                                
  public string GenerateToken()
  {
      var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("Jwt:Key"));
      var creds = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);
      var token = new JwtSecurityToken(
        issuer: "Jwt:Issuer",
        audience: "Jwt:Audience",
        claims: new[] {
          new Claim("sub", "user1")
        },
        expires: DateTime.Now.AddHours(1),
        signingCredentials: creds);
      var jwtToken = new JwtSecurityTokenHandler().WriteToken(token);
      return jwtToken;
  }

                            
                        

This code generates a JWT token that is valid for 1 hour, using the values for Jwt:Issuer, Jwt:Audience, and Jwt:Key from your configuration.

With these steps, you can implement JWT authentication in your ASP.NET Core 6 app.

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