System.IdentityModel.Tokens.JwtSecurityToken custom properties

Question

My AuthServer is currently using the following code to generate a JwtSecurityToken:

var token = new JwtSecurityToken(_issuer, audienceId, data.Identity.Claims, issued.Value.UtcDateTime, expires.Value.UtcDateTime, signingKey);
var handler = new JwtSecurityTokenHandler();
var jwt = handler.WriteToken(token);

The payload looks like this:

{
  "unique_name": "myUserName",
  "sub": "myUserName",
  "role": "API_User",
  "iss": "Automation",
  "aud": "099153c2625149bc8ecb3e85e03f0022",
  "exp": 1486056731,
  "nbf": 1483464731
}

I would like to add some custom fields/properties within the token payload, such as ProfilePicURL, so that the payload can look something like this:

{
  "unique_name": "myUserName",
  "sub": "myUserName",
  "role": "API_User",
  "iss": "Automation",
  "aud": "099153c2625149bc8ecb3e85e03f0022",
  "exp": 1486056731,
  "nbf": 1483464731,
  "profilePicture": "http://url/user.jpg"
}

How do I go about adding these custom properties and ensuring that the token contains them?

Answer 1

JwtSecurityToken exposes a JwtPayload Payload { get; set;} property. JwtPayload derives from Dictionary<string, object> so just add it to the payload...

var token = new JwtSecurityToken(_issuer, audienceId, data.Identity.Claims, issued.Value.UtcDateTime, expires.Value.UtcDateTime, signingKey);
token.Payload["profilePicture"] = "http://url/user.jpg"
var handler = new JwtSecurityTokenHandler();
var jwt = handler.WriteToken(token);

It is important that you use WriteToken to encode and sign the token, as simply getting the RawData property will not work (the token will not contain the custom claims).