JWT (JSON Web Token) authentication is a popular way of implementing authentication in ASP.NET applications. Here are the steps involved in implementing JWT authentication in ASP.NET:
Install the required packages:
First, you need to install the Microsoft.AspNetCore.Authentication.JwtBearer package using NuGet Package Manager.
Configure authentication:
Next, you need to configure authentication in your ASP.NET application by adding the following code to the ConfigureServices method in the Startup.cs file:
services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
.AddJwtBearer(options =>
{
options.TokenValidationParameters = new TokenValidationParameters
{
ValidateIssuer = true,
ValidateAudience = true,
ValidateLifetime = true,
ValidateIssuerSigningKey = true,
ValidIssuer = Configuration["Jwt:Issuer"],
ValidAudience = Configuration["Jwt:Audience"],
IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["Jwt:Key"]))
};
});
This code configures the JWT authentication scheme and sets the options for token validation.
Generate a token:
When a user logs in, you need to generate a JWT token and return it to the client. You can use the JwtSecurityTokenHandler class to generate a token, like this:
var tokenHandler = new JwtSecurityTokenHandler();
var key = Encoding.ASCII.GetBytes("your-secret-key");
var tokenDescriptor = new SecurityTokenDescriptor
{
Subject = new ClaimsIdentity(new Claim[]
{
new Claim(ClaimTypes.Name, "username")
}),
Expires = DateTime.UtcNow.AddHours(1),
SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key),
SecurityAlgorithms.HmacSha256Signature)
};
var token = tokenHandler.CreateToken(tokenDescriptor);
var tokenString = tokenHandler.WriteToken(token);
Protect routes:
Finally, you need to protect routes in your ASP.NET application by adding the [Authorize] attribute to controllers or actions that require authentication.
The request flow for JWT authentication in ASP.NET is as follows:
- The client sends a request to the server with a JWT token in the Authorization header.
- The server receives the request and validates the JWT token using the configured options.
- If the token is valid, the server allows the request to proceed and executes the requested action.
- If the token is invalid or expired, the server returns an HTTP 401 Unauthorized response to the client.
