c# - 如何使用 JWK 为 ES256 alg 验证 JWT？

Question

我有 JWT

var signedJwt = "eyJhbGciOiJFUzI1NiIsImtpZCI6IjZjNTUxNmUxLTkyZGMtNDc5ZS1hOGZmLTVhNTE5OTJlMDAwMSIsInR5cCI6IkpXVCJ9.eyJpYXQiOjE1OTY3MzA4ODMsInJlcXVlc3RfYm9keV9zaGEyNTYiOiI4NDMyODhkMWMxYmM0NzhlMTBhOTM2NWQ1YjIzY2U5ZWZlY2E2ZjdkYjA3NDQ3Y2JmNjU4YTg3ZjEzZjI1ZjJmIn0.3yQY6gtNq0lQlx6eNLO_3coGqf2VkX2CBRWam9Lz0dcVvr8h4LkYfuZMwQf1fzZ_XXHEV_o17LciyBC-O72UUw"

然后我得到了一个公钥:

{
    "alg": "ES256",
    "created_at": 1560466143,
    "crv": "P-256",
    "expired_at": null,
    "kid": "6c5516e1-92dc-479e-a8ff-5a51992e0001",
    "kty": "EC",
    "use": "sig",
    "x": "35lvC8uz2QrWpQJ3TUH8t9o9DURMp7ydU518RKDl20k",
    "y": "I8BuXB2bvxelzJAd7OKhd-ZwjCst05Fx47Mb_0ugros"
}

我正在尝试使用 C# 中的 Jose 库进行解码

var claims = Jose.JWT.Decode(signedJwt, publicKey, JwsAlgorithm.ES256);

每次我收到错误:

EcdsaUsingSha algorithm expects key to be of either CngKey or ECDsa types.

我认为我使用 key 的方式不正确，但我找不到任何方法将 json key 转换为 pem 或任何有效的东西。

Answer 1

您可以创建类型为 EccKey 的 key 从 JWK 喜欢
这个:

using Jose;
using Microsoft.AspNetCore.WebUtilities;
using Security.Cryptography;
using System;
using System.Text.Json;

namespace josejwttest
{
    public class JWK
    {
        public string alg { get; set; }
        public int? created_at { get; set; }
        public string crv { get; set; }
        public int? expired_at { get; set; }
        public string kid { get; set; }
        public string kty { get; set; }
        public string use { get; set; }
        public string x { get; set; }
        public string y { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var signedJwt = "eyJhbGciOiJFUzI1NiIsImtpZCI6IjZjNTUxNmUxLTkyZGMtNDc5ZS1hOGZmLTVhNTE5OTJlMDAwMSIsInR5cCI6IkpXVCJ9.eyJpYXQiOjE1OTY3MzA4ODMsInJlcXVlc3RfYm9keV9zaGEyNTYiOiI4NDMyODhkMWMxYmM0NzhlMTBhOTM2NWQ1YjIzY2U5ZWZlY2E2ZjdkYjA3NDQ3Y2JmNjU4YTg3ZjEzZjI1ZjJmIn0.3yQY6gtNq0lQlx6eNLO_3coGqf2VkX2CBRWam9Lz0dcVvr8h4LkYfuZMwQf1fzZ_XXHEV_o17LciyBC-O72UUw";

            var jwkJson = "{\"alg\": \"ES256\",\"created_at\": 1560466143, \"crv\": \"P -256\", \"expired_at\": null, \"kid\": \"6c5516e1-92dc-479e-a8ff-5a51992e0001\", \"kty\": \"EC\", \"use\": \"sig\", \"x\": \"35lvC8uz2QrWpQJ3TUH8t9o9DURMp7ydU518RKDl20k\", \"y\": \"I8BuXB2bvxelzJAd7OKhd-ZwjCst05Fx47Mb_0ugros\"}";

            var jwk = JsonSerializer.Deserialize<JWK> (jwkJson);
            
            var publicECCKey = EccKey.New(WebEncoders.Base64UrlDecode(jwk.x), WebEncoders.Base64UrlDecode(jwk.y)) ;

            var claims = Jose.JWT.Decode(signedJwt, publicECCKey, JwsAlgorithm.ES256);
        }
    }
}

x和 y是 Base64Url 编码在 jwk 中，所以需要使用 Base64Url Decoder 将其转换为 byte[] .我用过 Base64UrlDecode为此，但您当然可以使用任何其他解决方案。