Authentication and Authorization

75 min

ASP.NET Core provides a flexible authentication and authorization system, enabling you to control who can access your application and what they can do. Authentication verifies user identity (who you are), while authorization controls access to resources (what you can do). ASP.NET Core supports multiple authentication schemes (cookies, JWT, OAuth, etc.). Understanding authentication and authorization enables secure applications. Security is critical for production applications.

You can use built-in identity providers (ASP.NET Core Identity) or integrate with external services like Azure AD, Google, or Facebook for authentication. ASP.NET Core Identity provides user management, password hashing, and account features. External providers enable users to sign in with existing accounts. Understanding authentication options enables choosing appropriate approaches. Different applications need different authentication strategies.

Authorization policies allow you to define complex access control rules, enabling fine-grained permission management. Policies can check roles, claims, requirements, or custom logic. Policies are defined in configuration and applied with [Authorize] attributes. Understanding authorization policies enables sophisticated access control. Policies are powerful for complex authorization requirements.

JWT (JSON Web Tokens) are commonly used for API authentication, providing stateless, scalable authentication. JWTs contain claims (user information) and are signed to prevent tampering. JWTs enable stateless authentication—no server-side session storage needed. Understanding JWT enables API authentication. JWTs are standard for modern API authentication.

Role-based authorization checks if users belong to specific roles (Admin, User, etc.), while claim-based authorization checks for specific claims (permissions, attributes). Roles are simple but less flexible. Claims enable more granular authorization. Understanding both approaches enables appropriate authorization design. Many applications use both roles and claims.

Best practices include using HTTPS for all authentication, storing secrets securely (not in code), implementing proper password policies, using strong authentication for sensitive operations, and logging authentication events. Understanding authentication and authorization enables secure applications. Security requires careful implementation and ongoing attention.

Key Concepts

ASP.NET Core provides flexible authentication and authorization.
Authentication verifies identity; authorization controls access.
Multiple authentication schemes are supported (cookies, JWT, OAuth).
Authorization policies enable complex access control rules.
JWT tokens provide stateless API authentication.

Learning Objectives

Master

Implementing authentication with ASP.NET Core Identity
Using JWT tokens for API authentication
Creating authorization policies
Integrating external authentication providers

Develop

Understanding security principles
Designing secure authentication systems
Implementing comprehensive authorization

Tips

Always use HTTPS for authentication—never send credentials over HTTP.
Store secrets securely using configuration or secret management.
Use JWT for API authentication—it's stateless and scalable.
Implement proper password policies and hashing.

Common Pitfalls

Not using HTTPS, exposing credentials to attackers.
Storing secrets in code, creating security vulnerabilities.
Not implementing proper authorization, allowing unauthorized access.
Not validating tokens properly, allowing token tampering.

Summary

ASP.NET Core provides flexible authentication and authorization.
Multiple authentication schemes and providers are supported.
Authorization policies enable complex access control.
Understanding authentication and authorization enables secure applications.
Security requires careful implementation and best practices.

Exercise

Implement basic authentication with JWT tokens.

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

// Controller
[Authorize]
[ApiController]
public class SecureController : ControllerBase
{
    [HttpGet]
    public IActionResult Get()
    {
        return Ok("This is a secure endpoint");
    }
}

Authentication and Authorization