c# - 创建由其他 ECDSA 证书签名的 ECDSA 证书

Question

我需要创建由“根”证书(自签名，ECDSA)签名的“客户端”ECDSA 证书。 “根”证书是按照 Translating Elliptic Curve parameters (BC to MS) 中的描述创建的.

要创建“客户端”证书(由“根”签名)，可以使用稍微修改过的算法。 不同之处在于私钥(用于从为“客户端”证书生成的 key 对中签署公钥)必须从“外部”提供 - 它是“根”证书的私钥。 但这就是问题所在。我找不到如何获取私钥并将其转换为可以传递给签名工厂的 Org.BouncyCaSTLe.Crypto.Parameters.ECPrivateKeyParameters 类型的方法。

// 1. get private-key of "Root" certificate from existing certificate:
byte[] msRootCertData = File.ReadAllBytes(@"c:\root_ecdsa_cert.pfx");
X509Certificate2 msRootCert = new X509Certificate2(msRootCertData);
ECDsaCng msRootPrivateKey = msRootCert.GetECDsaPrivateKey() as ECDsaCng;
ECParameters msRootPrivateKeyParameters = msRootPrivateKey.ExportParameters(true);

// here comes the issue:
ECPrivateKeyParameters bcRootPrivateKeysParameters = TranslateMSKeysToBouncy(msRootPrivateKeyParameters);

// 2. generate "Client" key-pair:
AsymmetricCipherKeyPair bcClientKeyPair = bcKeyGen.GenerateKeyPair();
ECPrivateKeyParameters bcClientPrivKey = (ECPrivateKeyParameters)bcClientKeyPair.Private;
ECPrivateKeyParameters bcClientPublKey = (ECPublicKeyParameters)bcClientKeyPair.Public;

// 3. create X509 certificate:
X509V3CertificateGenerator bcCertGen = new X509V3CertificateGenerator();
bcCertGen.SetPublicKey(bcClientPublKey);
// .. set subject, validity period etc
ISignatureFactory sigFac = new Asn1SignatureFactory("Sha256WithECDSA", bcRootPrivateKeysParameters);
Org.BouncyCastle.X509.X509Certificate bcClientX509Cert = bcCertGen.Generate(sigFac);
byte[] x509CertEncoded = bcClientX509Cert.GetEncoded();

//其余同上例

有什么提示吗？ 或者还有别的办法吗？ (例如:将 X509Certificate2 的实例直接传递给 BouncyCaSTLe 库(避免将私钥转换为 Cng)，或者在没有 BouncyCaSTLe 的情况下生成“客户端”证书) 谢谢。

Answer 1

如果您可以依赖 .NET Framework 4.7.2(或 .NET Core 2.0)，则可以在没有 BouncyCaSTLe 的情况下通过新的 CertificateRequest 实现。类:

X509Certificate2 publicPrivate;

using (ECDsa clientPrivateKey = ECDsa.Create())
{
    var request = new CertificateRequest(
        "CN=Et. Cetera",
        clientPrivateKey,
        HashAlgorithmName.SHA256);

    // Assuming this isn't another CA cert:
    request.CertificateExtensions.Add(
        new X509BasicConstraintsExtension(false, false, 0, false));

    // other CertificateExtensions as you desire.

    // Assign, or derive, a serial number.
    // RFC 3280 recommends that it have no more than 20 bytes encoded.
    // 12 random bytes seems long enough.
    byte[] serial = new byte[12];

    using (RandomNumberGenerator rng = RandomNumberGenerator.Create())
    {
        rng.GetBytes(serial);
    }

    DateTimeOffset notBefore = DateTimeOffset.UtcNow;
    DateTimeOffset notAfter = notBefore.AddMonths(15);

    using (X509Certificate2 publicOnly = request.Create(
        msRootCert,
        notBefore,
        notAfter,
        serial))
    {
        publicPrivate = publicOnly.CopyWithPrivateKey(clientPrivateKey);
    }
}

// The original key object was disposed,
// but publicPrivate.GetECDsaPrivateKey() still works.

如果要将 publicPrivate 添加到 X509Store，您需要 1) 将其导出到 PFX 并重新导入，或者 2) 更改 key 创建以使用命名 key 。否则，只会保存公共(public)部分(在 Windows 上)。