Passing JSON Object as a claim of JWT Token in ASP.NET Core 2.0

Question

Is it possible to pass a JSON object as a claim of JWT Token or list of objects (like shown on below example)?

{
  "nickname": [
    {
      "external_nickname": "tomas",
      "internal_nickname": "t_omas"
    }, 
    {
      "external_nickname": "malex",
      "internal_nickname": "alexander014"
    } 
  ]
}

So far I can only pass one nickname in token

"nickname" : "tomas"

Or I can pass an array

"nickname" : ["nickname1","nickname2"]

But none of these satisfies me.

EDIT:

Using Avin Kavish approach I got extra slashes in JSON Object. I don't want them. How to get rid of them?

 "nickname": "[{\"external_nickname\":\"tomas\",\"internal_nickname\":\"t_omas\"}]"

In javascript, `JSON.Parse(value)`. In c# `JsonConvert.DeserializeObject(value)` where T is your type — Avin Kavish, Jun 11 '19 at 17:18
https://stackoverflow.com/questions/28325107/tell-json-net-to-write-a-single-quote-rather-than-a-double-quote-when-serializi Youc an write a method than uses the JSON.Net JsonTextWriter.QuoteChar — MikeJ, Jun 11 '19 at 17:23
That shouldn't be a problem as deserialising will remove the backslashes. — Avin Kavish, Jun 11 '19 at 17:25

score 3 · Answer 1 · answered Jun 23 '22 at 13:48

If you look at the underlying structures you will find that the JWTPayload class inherits from Dictionary<string,object>. Once we know that, the rest is easy:

// Build the claims list somehow, may contain nested objects
// NOTE: any nested data must be JSON-serializable!
Dictionary<string,object> claims = BuildMeThatClaimsList();

// Add all claims manually because the CTORs only accept string values
var token = new JwtSecurityToken(issuer, audience, Array.Empty<Claim>(), notBefore, expires, signingCreds);
foreach (var pair in claims)
  token.Payload.Add(pair.Key, pair.Value);
return token;

Avin Kavish · Answer 2 · 2019-06-11T17:23:32.303

2

Yes, serialize it first.

var claim = new Claim("nickname", JsonConvert.SerializeObject(nicknames));

In order to use the nicknames, you need to deserialize from a string back to a plain old object.

In javascript,

const nicknames = JSON.Parse(value)

In C#,

var nicknames = JsonConvert.DeserializeObject<T>(value) // <-- where T is your type

edited Jun 11 '19 at 17:23

answered Jun 11 '19 at 16:36

Avin Kavish

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There are slashes present i JWT Token using your approach. Do you know how to fix it? – justme Jun 11 '19 at 17:14
I think the slashes are great for escaping the double quotes in the serialized object, can't you remove them when you use the claims eg. from your client? – Jun 11 '19 at 17:20

score 2 · Answer 3 · answered Mar 25 '21 at 01:46

I use JWT NuGet package.

Install-Package JWT

the code:

        var payload = new
        {
            nickname = new[]
            {
                new {external_nickname = "tomas", internal_nickname = "t_omas"},
                new {external_nickname = "malex", internal_nickname = "alexander014"}
            }
        };
        
        var encoder = new JwtEncoder(new HMACSHA256Algorithm(), new JsonNetSerializer(), new JwtBase64UrlEncoder());
        var token = encoder.Encode(payload, "your_secret");

score 2 · Answer 4 · answered May 16 '23 at 00:14

For those using asp.net core, this is really simple. The claim object has an additional parameter.

new Claim("json", "{\"sample\":{\"sample\":\"value\"}}", JsonClaimValueTypes.Json)

The JsonClaimValueTypes is part of System.IdentityModel.Tokens.Jwt

Passing JSON Object as a claim of JWT Token in ASP.NET Core 2.0

4 Answers4