Generating a JWT for Firebase

我正在尝试为Windows上的C# .NET编写一个自定义的JWT令牌生成器，以便在Google Firebase中使用。我从 StackOverflow 上的几个不同地方获取的来源（我正在尝试重新发现它们，以便我可以归功于原作者并提出一些额外的问题），所以它在一起有点像大杂烩。

在大多数情况下，它似乎有效，但它似乎没有像预期的那样生成有效的（Firebase）令牌。这可能完全是由于我对它首先应该如何工作缺乏了解，但是如果我能从这里得到第二双世界级的工程师眼睛来指出我做错了什么并使事情顺利进行，那就太好了。

代码如下：

// Token generator setup
using Newtonsoft.Json;
using System;
using System.IO;
using System.Web;
using System.Web.Configuration;
namespace myapp.Utils
{
    public class GoogleJsonWebToken
    {
        public static string Encode(string uid)
        {
            var utc0 = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
            var issueTime = DateTime.Now;
            var iat = (int)issueTime.Subtract(utc0).TotalSeconds;
            var exp = (int)issueTime.AddMinutes(60).Subtract(utc0).TotalSeconds;
            var firebaseInfPath = HttpContext.Current.Server.MapPath(WebConfigurationManager.AppSettings["firebaseInf"]);
            var firebaseInfJsonContent = File.ReadAllText(firebaseInfPath);
            var firebaseInf = JsonConvert.DeserializeObject<dynamic>(firebaseInfJsonContent);
            var privateKey = (string)firebaseInf.private_key;
            var payload = new
            {
                iss = firebaseInf.client_email,
                scope = firebaseInf.client_email,
                aud = "https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit",
                exp = exp,
                uid = uid,
                iat = iat,
                claims = new { premium_account = true }
            };
            return myapp.Utils.JsonWebToken.Encode(payload, privateKey, JwtHashAlgorithm.RS256);
        }
    }
}

以下是 JWT 哈希算法代码：

// JsonWebToken.cs
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;
namespace myapp.Utils
{
    public enum JwtHashAlgorithm
    {
        RS256,
        HS384,
        HS512
    }
    public class JsonWebToken
    {
        private static Dictionary<JwtHashAlgorithm, Func<byte[], byte[], byte[]>> HashAlgorithms;
        static JsonWebToken()
        {
            HashAlgorithms = new Dictionary<JwtHashAlgorithm, Func<byte[], byte[], byte[]>>
            {
                { JwtHashAlgorithm.RS256, (key, value) => { using (var sha = new HMACSHA256(key)) { return sha.ComputeHash(value); } } },
                { JwtHashAlgorithm.HS384, (key, value) => { using (var sha = new HMACSHA384(key)) { return sha.ComputeHash(value); } } },
                { JwtHashAlgorithm.HS512, (key, value) => { using (var sha = new HMACSHA512(key)) { return sha.ComputeHash(value); } } }
            };
        }
        public static string Encode(object payload, string key, JwtHashAlgorithm algorithm)
        {
            var keyBytes = Encoding.UTF8.GetBytes(key);
            return Encode(payload, keyBytes, algorithm);
        }
        public static string Encode(object payload, byte[] keyBytes, JwtHashAlgorithm algorithm)
        {
            var segments = new List<string>();
            var header = new { alg = algorithm.ToString(), typ = "JWT" };
            byte[] headerBytes = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(header, Formatting.None));
            byte[] payloadBytes = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(payload, Formatting.None));
            //byte[] payloadBytes = Encoding.UTF8.GetBytes(@"{"iss":"761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com","scope":"https://www.googleapis.com/auth/prediction","aud":"https://accounts.google.com/o/oauth2/token","exp":1328554385,"iat":1328550785}");
            segments.Add(Base64UrlEncode(headerBytes));
            segments.Add(Base64UrlEncode(payloadBytes));
            var stringToSign = string.Join(".", segments.ToArray());
            var bytesToSign = Encoding.UTF8.GetBytes(stringToSign);
            byte[] signature = HashAlgorithms[algorithm](keyBytes, bytesToSign);
            segments.Add(Base64UrlEncode(signature));
            return string.Join(".", segments.ToArray());
        }
        public static string Decode(string token, string key)
        {
            return Decode(token, key, true);
        }
        public static string Decode(string token, string key, bool verify)
        {
            var parts = token.Split('.');
            var header = parts[0];
            var payload = parts[1];
            byte[] crypto = Base64UrlDecode(parts[2]);
            var headerJson = Encoding.UTF8.GetString(Base64UrlDecode(header));
            var headerData = JObject.Parse(headerJson);
            var payloadJson = Encoding.UTF8.GetString(Base64UrlDecode(payload));
            var payloadData = JObject.Parse(payloadJson);
            if (verify)
            {
                var bytesToSign = Encoding.UTF8.GetBytes(string.Concat(header, ".", payload));
                var keyBytes = Encoding.UTF8.GetBytes(key);
                var algorithm = (string)headerData["alg"];
                var signature = HashAlgorithms[GetHashAlgorithm(algorithm)](keyBytes, bytesToSign);
                var decodedCrypto = Convert.ToBase64String(crypto);
                var decodedSignature = Convert.ToBase64String(signature);
                if (decodedCrypto != decodedSignature)
                {
                    throw new ApplicationException(string.Format("Invalid signature. Expected {0} got {1}", decodedCrypto, decodedSignature));
                }
            }
            return payloadData.ToString();
        }
        private static JwtHashAlgorithm GetHashAlgorithm(string algorithm)
        {
            switch (algorithm)
            {
                case "RS256": return JwtHashAlgorithm.RS256;
                case "HS384": return JwtHashAlgorithm.HS384;
                case "HS512": return JwtHashAlgorithm.HS512;
                default: throw new InvalidOperationException("Algorithm not supported.");
            }
        }
        // from JWT spec
        private static string Base64UrlEncode(byte[] input)
        {
            var output = Convert.ToBase64String(input);
            output = output.Split('=')[0]; // Remove any trailing '='s
            output = output.Replace('+', '-'); // 62nd char of encoding
            output = output.Replace('/', '_'); // 63rd char of encoding
            return output;
        }
        // from JWT spec
        private static byte[] Base64UrlDecode(string input)
        {
            var output = input;
            output = output.Replace('-', '+'); // 62nd char of encoding
            output = output.Replace('_', '/'); // 63rd char of encoding
            switch (output.Length % 4) // Pad with trailing '='s
            {
                case 0: break; // No pad chars in this case
                case 2: output += "=="; break; // Two pad chars
                case 3: output += "="; break; // One pad char
                default: throw new System.Exception("Illegal base64url string!");
            }
            var converted = Convert.FromBase64String(output); // Standard base64 decoder
            return converted;
        }
    }
}

public class GoogleJsonWebToken
{
    public static string Encode(string uid)
    {
        var firebaseInfPath = HttpContext.Current.Server.MapPath(WebConfigurationManager.AppSettings["firebaseInf"]);
        var firebaseInfJsonContent = File.ReadAllText(firebaseInfPath);
        var firebaseInf = JsonConvert.DeserializeObject<dynamic>(firebaseInfJsonContent);
        // NOTE: Replace this with your actual RSA public/private keypair!
        var provider = new RSACryptoServiceProvider(2048);
        var parameters = provider.ExportParameters(true);
        // Build the credentials used to sign the JWT
        var signingKey = new RsaSecurityKey(parameters);
        var signingCredentials = new SigningCredentials(signingKey, SecurityAlgorithms.RsaSha256);
        // Create a collection of optional claims
        var now = DateTimeOffset.UtcNow;
        var claims = new[]
        {
            new Claim(JwtRegisteredClaimNames.Sub, firebaseInf.client_email),
            new Claim(JwtRegisteredClaimNames.Iat, now.ToUnixTimeSeconds().ToString(), ClaimValueTypes.Integer64),
            new Claim("uid", uid, ClaimValueTypes.String), 
            new Claim("premium_account", "true", ClaimValueTypes.Boolean)
        };
        // Create and sign the JWT, and write it to a string
        var jwt = new JwtSecurityToken(
            issuer: firebaseInf.client_email,
            audience: "https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit",
            claims: claims,
            expires: now.AddMinutes(60).DateTime,
            signingCredentials: signingCredentials);
        return new JwtSecurityTokenHandler().WriteToken(jwt);
    }
}