使用字符串中的公钥验证JWT

问题描述

我具有以下格式的公钥： ----- BEGIN RSA公钥----- MIIBCgKCAQEA1pjRK + cOnesh5L1wrt1Tmx + FvyNRj4wuAotlqIWtHS8piqrzsIOJg + tlbUtEXYju + KOcIohZnnmfj0cq28RcQ19HIohqUXypmUbNy9np / M + Aj9NcyKIaNyuEZ + UhcU / OIStHK4eTUJt + RWL + 0Q1 / rl49tg7h + toB9Y6Y3SeytXvZhMx3N5qqmHHnorpfb65bvvHsicGDB7vK5kn55o + C2LhRIxfnw87nKnhPBMRbZg + BKCTXD4svz4a2xiR / uM4rxebIBgB3Sm4X1w3yoRr0F3IDhAgXmEhSZ078wm3ohPfuuwymfVhvdzavm42NwzixZ7n52SowFE2v0DSJh3IbPwIDAQAB -----结束RSA公钥-----

如何使用该字符串实现C＃来验证我的JWT？我在Verifying JWT signed with the RS256 algorithm using public key in C#找到了类似的话题，但是没有一种解决方案适合我的情况。

有我的代码：

        public static bool TransformKey(string fullKey)
        {
            try
            {
                var publicKey = fullKey.Replace("-----BEGIN RSA PUBLIC KEY-----","");
                publicKey = publicKey.Replace("-----END RSA PUBLIC KEY-----","");
                publicKey = publicKey.Replace("\n","");

                var keyBytes = Convert.FromBase64String(publicKey); // your key here 
                asymmetricKeyParameter asymmetricKeyParameter = PublicKeyFactory.CreateKey(keyBytes);
                RsaKeyParameters rsaKeyParameters = (RsaKeyParameters)asymmetricKeyParameter;
                RSAParameters rsaParameters = new RSAParameters
                {
                    Modulus = rsaKeyParameters.Modulus.ToByteArrayUnsigned(),Exponent = rsaKeyParameters.Exponent.ToByteArrayUnsigned()
                };
                return true;
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
                return false;
            }
        }
      
        static void Main(string[] args)
        {
            // The code provided will print ‘Hello World’ to the console.
            // Press Ctrl+F5 (or go to Debug > Start Without Debugging) to run your app.
            string key = "-----BEGIN RSA PUBLIC KEY-----MIIBCgKCAQEA1pjRK+cOnesh5L1wrt1Tmx+FvyNRj4wuAotlqIWtHS8piqrzsIOJg+tlbUtEXYju+KOcIohZnnmfj0cq28RcQ19HIohqUXypmUbNy9np/M+Aj9NcyKIaNyuEZ+UhcU/OIStHK4eTUJt+RWL+0Q1/rl49tg7h+toB9Y6Y3SeytXvZhMx3N5qqmHHnorpfb65bvvHsicGDB7vK5kn55o+C2LhRIxfnw87nKnhPBMRbZg+BKCTXD4svz4a2xiR/uM4rxebIBgB3Sm4X1w3yoRr0F3IDhAgXmEhSZ078wm3ohPfuuwymfVhvdzavm42NwzixZ7n52SowFE2v0DSJh3IbPwIDAQAB-----END RSA PUBLIC KEY-----";
            bool test = TransformKey(key);
            Console.ReadKey();
        }

当我尝试初始化asymmetricKeyParameter对象时，它返回异常：

System.ArgumentException: UnkNown object in GetInstance: Org.BouncyCastle.Asn1.DerInteger
Parameter name: obj
   w Org.BouncyCastle.Asn1.Asn1Sequence.GetInstance(Object obj)
   w Org.BouncyCastle.Asn1.X509.AlgorithmIdentifier.GetInstance(Object obj)
   w Org.BouncyCastle.Asn1.X509.SubjectPublicKeyInfo..ctor(Asn1Sequence seq)
   w Org.BouncyCastle.Asn1.X509.SubjectPublicKeyInfo.GetInstance(Object obj)
   w Org.BouncyCastle.Security.PublicKeyFactory.CreateKey(Byte[] keyInfoData)

具有模数和指数的字符串类型的代码片段可能有用：

RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.ImportParameters(
              new RSAParameters()
              {
                  Modulus = FromBase64Url("w7Zdfmece8iaB0kiTY8pCtiBtzbptJmP28nSWwtdjRu0f2GFpajvWE4VhfJAjEsOcwYzay7XGN0b-X84BfC8hmCTOj2b2eHT7NsZegFPKRUQzJ9wW8ipn_aDJWMGdub1XyqT1E7DYqjUCEOD1b4FLpy_xPn6oV_TYOfQ9fZdbE5HGxJUzekuGcOKqOQ8M7wfYHhHHLxGpQVgL0apWuP2gDDOdTtpuld4d2lK1MZK99s9gaSjRHE8JDb1Z4IGhEcEyzkxswVdpndUWzfvWBBWXWxtSUvQGBRkuy1BHOa4sP6FKjWEeeF7gm7UMs2Nm2QUgNZw6xvEDgalk4KASdIxRQ"),Exponent = FromBase64Url("AQAB")
              });

解决方法

对于.NET Framework（例如4.7.2），可以使用例如BouncyCastle（例如v1.8.6.1）导入公共PKCS＃1密钥：

using System.IO;
using System.Security.Cryptography;

using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.OpenSsl;
using Org.BouncyCastle.Security;

...

string publicPKCS1 = @"-----BEGIN RSA PUBLIC KEY-----
                       MIIBCgKCAQEA1pjRK+cOnEsh5L1wrt1Tmx+FvyNRj4wuAotlqIWtHS8pIqRzsIOJ
                       g+tlbUtEXYju+KOcIohZnnmfj0cq28RcQ19HIohqUXypmUbNy9np/M+Aj9NcyKIa
                       NyuEZ+UhcU/OIStHK4eTUJt+RWL+0Q1/rl49tg7h+toB9Y6Y3SeytXvZhMx3N5qq
                       mHHNorpfb65bvvHsicGDB7vK5kn55o+C2LhRIxfnw87nKnhPBMRbZg+BKCTXD4sv
                       z4a2xiR/uM4rxebIBgB3Sm4X1w3yoRr0F3IDhAgXmEhSZ078wm3ohPfuuwymfVhv
                       dzavm42NwzixZ7n52SowFE2v0DSJh3IbPwIDAQAB
                       -----END RSA PUBLIC KEY-----";

PemReader pemReader = new PemReader(new StringReader(publicPKCS1));
AsymmetricKeyParameter asymmetricKeyParameter = (AsymmetricKeyParameter)pemReader.ReadObject();
RSAParameters rsaParameters = DotNetUtilities.ToRSAParameters((RsaKeyParameters)asymmetricKeyParameter);

RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.ImportParameters(rsaParameters);

...

JWT的验证可以通过JWT库（例如 System.IdentityModel.Tokens.Jwt ）或纯加密API完成。两者在linked question的答案中都有详细描述。关于前者，另请参阅here，第二段。