Emitindo tokens

Emissão versus validação

dotnet add package System.IdentityModel.Tokens.Jwt

A chave de assinatura

var key = new SymmetricSecurityKey(
    Encoding.UTF8.GetBytes(configuration["Jwt:Key"]!));

SigningCredentials

var creds = new SigningCredentials(
    key,
    SecurityAlgorithms.HmacSha256);

Construindo as declarações

var claims = new List<Claim>
{
    new Claim(JwtRegisteredClaimNames.Sub, user.Id.ToString()),
    new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
    new Claim(ClaimTypes.Name, user.UserName),
    new Claim(ClaimTypes.Role, user.Role)
};

Criando o JwtSecurityToken

var token = new JwtSecurityToken(
    issuer: configuration["Jwt:Issuer"],
    audience: configuration["Jwt:Audience"],
    claims: claims,
    notBefore: DateTime.UtcNow,
    expires: DateTime.UtcNow.AddMinutes(15),
    signingCredentials: creds);

Serializando para uma cadeia de caracteres

var handler = new JwtSecurityTokenHandler();
string jwt = handler.WriteToken(token);
// jwt now looks like eyJhbGciOiJI...

Um serviço de tokens reutilizável

public class TokenService(IConfiguration config)
{
    public string CreateAccessToken(AppUser user)
    {
        var key = new SymmetricSecurityKey(
            Encoding.UTF8.GetBytes(config["Jwt:Key"]!));
        var creds = new SigningCredentials(
            key, SecurityAlgorithms.HmacSha256);
        var claims = new[]
        {
            new Claim(JwtRegisteredClaimNames.Sub, user.Id.ToString()),
            new Claim(ClaimTypes.Role, user.Role)
        };
        var token = new JwtSecurityToken(
            config["Jwt:Issuer"], config["Jwt:Audience"],
            claims, expires: DateTime.UtcNow.AddMinutes(15),
            signingCredentials: creds);
        return new JwtSecurityTokenHandler().WriteToken(token);
    }
}

Configurando o ponto de acesso de login

app.MapPost("/login", (LoginDto dto, TokenService tokens) =>
{
    var user = Authenticate(dto.Username, dto.Password);
    if (user is null) return Results.Unauthorized();
    return Results.Ok(new { accessToken = tokens.CreateAccessToken(user) });
});

Simétrica versus assimétrica

var creds = new SigningCredentials(
    new RsaSecurityKey(rsaPrivateKey),
    SecurityAlgorithms.RsaSha256);

Registrando o serviço

builder.Services.AddScoped<TokenService>();

Mantenha os tokens enxutos e curtos

expires: DateTime.UtcNow.AddMinutes(15)

Verificação rápida

Recapitulação