Tell us about working with authorization and authentication (Keycloak, JWT)?

For authentication and authorization, Keycloak is often used in conjunction with JWT.

Keycloak is an identity and access management server that supports OAuth2 and OpenID Connect protocols. Upon successful authentication, Keycloak issues a JWT (JSON Web Token), which contains information about the user and their permissions.

In a C# application, a middleware is usually implemented to verify the JWT in the Authorization header of each request. If the token is valid and not expired, the user is considered authenticated, and authorization decisions are made based on roles from the token.

Example of JWT validation in ASP.NET Core:

services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.Authority = "https://keycloak.example.com/auth/realms/myrealm";
        options.Audience = "my-client-id";
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateAudience = true,
            ValidateIssuer = true
        };
    });

Thus, Keycloak handles user management and token issuance, while the application simply verifies them and uses them for access control.