Elointz / jwt

Jwt.Net, a JWT (JSON Web Token) implementation for .NET

Jwt.Net, a JWT (JSON Web Token) implementation for .NET

This library supports generating and decoding JSON Web Tokens.

Installation

Package is avaliable via NuGet. Or you can download and compile it yourself.

Supported .NET versions:

• .NET Framework 4.6.0
• .NET Framework 4.7.2
• .NET Standard 1.3
• .NET Standard 2.0

Usage

Creating (encoding) token

var payload = new Dictionary<string, object>
{
    { "claim1", 0 },
    { "claim2", "claim2-value" }
};
const string secret = "GQDstcKsx0NHjPOuXOYg5MbeJ1XT0uFiwDVvVBrk";

IJwtAlgorithm algorithm = new HMACSHA256Algorithm();
IJsonSerializer serializer = new JsonNetSerializer();
IBase64UrlEncoder urlEncoder = new JwtBase64UrlEncoder();
IJwtEncoder encoder = new JwtEncoder(algorithm, serializer, urlEncoder);

var token = encoder.Encode(payload, secret);
Console.WriteLine(token);

Or using the fluent builder API

  var token = new JwtBuilder()
      .WithAlgorithm(new HMACSHA256Algorithm())
      .WithSecret(secret)
      .AddClaim("exp", DateTimeOffset.UtcNow.AddHours(1).ToUnixTimeSeconds())
      .AddClaim("claim2", "claim2-value")
      .Build();

Console.WriteLine(token);

The output would be:

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJjbGFpbTEiOjAsImNsYWltMiI6ImNsYWltMi12YWx1ZSJ9.8pwBI_HtXqI3UgQHQ_rDRnSQRxFL1SR8fbQoS-5kM5s

Parsing (decoding) and verifying token

const string token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJjbGFpbTEiOjAsImNsYWltMiI6ImNsYWltMi12YWx1ZSJ9.8pwBI_HtXqI3UgQHQ_rDRnSQRxFL1SR8fbQoS-5kM5s";
const string secret = "GQDstcKsx0NHjPOuXOYg5MbeJ1XT0uFiwDVvVBrk";

try
{
    IJsonSerializer serializer = new JsonNetSerializer();
    IDateTimeProvider provider = new UtcDateTimeProvider();
    IJwtValidator validator = new JwtValidator(serializer, provider);
    IBase64UrlEncoder urlEncoder = new JwtBase64UrlEncoder();
    IJwtDecoder decoder = new JwtDecoder(serializer, validator, urlEncoder);
    
    var json = decoder.Decode(token, secret, verify: true);
    Console.WriteLine(json);
}
catch (TokenExpiredException)
{
    Console.WriteLine("Token has expired");
}
catch (SignatureVerificationException)
{
    Console.WriteLine("Token has invalid signature");
}

Or using the fluent builder API

try
{
    var json = new JwtBuilder()
        .WithSecret(secret)
        .MustVerifySignature()
        .Decode(token);                    
    Console.WriteLine(json);
}
catch (TokenExpiredException)
{
    Console.WriteLine("Token has expired");
}
catch (SignatureVerificationException)
{
    Console.WriteLine("Token has invalid signature");
}

The output would be:

{ "claim1": 0, "claim2": "claim2-value" }

You can also deserialize the JSON payload directly to a .NET type:

var payload = decoder.DecodeToObject<IDictionary<string, object>>(token, secret);
Console.WriteLine(payload["claim2"]);

Or using the fluent builder API

var payload = new JwtBuilder()
        .WithSecret(secret)
        .MustVerifySignature()
        .Decode<IDictionary<string, object>>(token);     
Console.WriteLine(payload["claim2"]);

The output would be:

claim2-value

Set and validate token expiration

As described in the JWT RFC, the exp "claim identifies the expiration time on or after which the JWT MUST NOT be accepted for processing." If an exp claim is present and is prior to the current time the token will fail verification. The exp (expiry) value must be specified as the number of seconds since 1/1/1970 UTC.

IDateTimeProvider provider = new UtcDateTimeProvider();
var now = provider.GetNow();

var unixEpoch = JwtValidator.UnixEpoch; // 1970-01-01 00:00:00 UTC
var secondsSinceEpoch = Math.Round((now - unixEpoch).TotalSeconds);

var payload = new Dictionary<string, object>
{
    { "exp", secondsSinceEpoch }
};
cosnt string secret = "GQDstcKsx0NHjPOuXOYg5MbeJ1XT0uFiwDVvVBrk";
var token = encoder.Encode(payload, secret);

var json = decoder.Decode(token, secret); // throws TokenExpiredException

Custom JSON serializer

By default JSON serialization is performed by JsonNetSerializer implemented using Json.Net. To use a different one, implement the IJsonSerializer interface:

public class CustomJsonSerializer : IJsonSerializer
{
    public string Serialize(object obj)
    {
        // Implement using favorite JSON serializer
    }

    public T Deserialize<T>(string json)
    {
        // Implement using favorite JSON serializer
    }
}

And then pass this serializer to JwtEncoder constructor:

IJwtAlgorithm algorithm = new HMACSHA256Algorithm();
IJsonSerializer serializer = new CustomJsonSerializer();
IBase64UrlEncoder urlEncoder = new JwtBase64UrlEncoder();
IJwtEncoder encoder = new JwtEncoder(algorithm, serializer, urlEncoder);

Custom JSON serialization settings with the default JsonNetSerializer

As mentioned above, the default JSON serialization is done by JsonNetSerializer. You can define your own custom serialization settings as follows:

JsonSerializer customJsonSerializer = new JsonSerializer
{
    // All keys start with lowercase characters instead of the exact casing of the model/property, e.g. fullName
    ContractResolver = new CamelCasePropertyNamesContractResolver(), 
    
    // Nice and easy to read, but you can also use Formatting.None to reduce the payload size
    Formatting = Formatting.Indented,
    
    // The most appropriate datetime format.
    DateFormatHandling = DateFormatHandling.IsoDateFormat,
    
    // Don't add keys/values when the value is null.
    NullValueHandling = NullValueHandling.Ignore,
    
    // Use the enum string value, not the implicit int value, e.g. "red" for enum Color { Red }
    Converters.Add(new StringEnumConverter())
};
IJsonSerializer serializer = new JsonNetSerializer(customJsonSerializer);