如何获取私钥，作为从天蓝色密钥存储库中获取的受密码保护的pfx的Byte [] [英] How to get private key as Byte[] of a password protected pfx fetched from azure key vault

问题描述

我正在使用GetSecretAsync()方法从Azure密钥保管库中获取证书，然后期望最终获得私钥的byte []和证书.

I am fetching my certificate from Azure Key Vault using GetSecretAsync() method and then I am expecting to get the byte[] of the private key and the certificate eventually.

我在.netcore3.1中有我的应用程序这就是我的代码的样子:

I have my application in .netcore3.1 This is how my code looks like :

var certWithPrivateKey = Client.GetSecretAsync(ConfigurationSettings.AppSettings["AKVEndpoint"], ConfigurationSettings.AppSettings["CertName"]).GetAwaiter().GetResult();
var privateKeyBytes = Convert.FromBase64String(certWithPrivateKey.Value);

X509Certificate2 x509Certificate = new X509Certificate2(privateKeyBytes);
var privateKey = x509Certificate.GetRSAPrivateKey() as RSA;

我得到了RSACng类型的有效privateKey，但是任何引发'privateKey.ExportRSAPrivateKey()"错误的操作(尝试ExportRSAPrivateKey())都引发了"Internal.Cryptography.CryptoThrowHelper.WindowsCryptographicException"类型的异常"和不支持请求的操作."

I get a valid privateKey of type RSACng, but any operation (tried ExportRSAPrivateKey()) on that throws an error of "'privateKey.ExportRSAPrivateKey()' threw an exception of type 'Internal.Cryptography.CryptoThrowHelper.WindowsCryptographicException'" and "The requested operation is not supported."

我不确定接下来如何获取私钥和​​证书的字节[].

I am not sure how to proceed next here to get the byte[] of the private key and certificate.

推荐答案

由于您实际上似乎确实需要导出:您当前的代码不会将私钥加载为可导出，因此无法导出.解决方法是断言可导出性:

Since you do actually seem to need to export: Your current code doesn't load the private key as exportable, so it can't be exported. The fix is to assert exportability:

X509Certificate2 x509Certificate =
    new X509Certificate2(privateKeyBytes, "", X509KeyStorageFlags.Exportable);

如果这还不够，那么您将遇到CAPI可导出性和CNG可导出性之间的差异(Windows较新的加密库).如果来自PFX/PKCS#12的私钥被加载到CNG中，则它只是加密的可导出"，而ExportParameters是纯文本导出.

If that's not enough, then you're encountering the difference between CAPI exportability and CNG exportability (Windows older, and newer, crypto libraries). If the private key from a PFX/PKCS#12 gets loaded into CNG it's only "encrypted exportable", but ExportParameters is plaintext-export.

有一种解决方法，尽管...将其导出加密，然后使用更灵活的导出策略将其导入其他地方，然后再次导出.

There's a workaround, though... export it encrypted, then import that somewhere else with a more flexible export policy, then export again.

此代码段使用.NET Core 3.0+ PemEncoding 类可简化将DER编码输出转换为PEM + DER输出的过程.如果您的出口商在.NET Framework上，则这是一个更复杂的问题.对于.NET Standard 2.0，实际上不是一个干净的解决方案(是否可以调用.NET Core/.NET 5的方法，否则可以使用Windows专用的.NET Framework版本?).

This snippet uses the .NET Core 3.0+ ExportPkcs8PrivateKey() method, since that's the format you want your data in, and new .NET 5 PemEncoding class to simplify turning the DER encoded output into PEM+DER output. If your exporter is on .NET Framework, this is a more complex problem. For .NET Standard 2.0 there's not really a clean solution (reflect call the methods for .NET Core/.NET 5, otherwise use the Windows-specific version for .NET Framework?).

byte[] pkcs8PrivateKey;

using (RSA privateKey = x509Certificate.GetRSAPrivateKey())
{
    pkcs8PrivateKey = ExportPrivateKey(privateKey);
}

File.WriteAllText(
    "tls.cer",
    new string(PemEncoding.Write("CERTIFICATE", x509Certificate.RawData));

File.WriteAllText(
    "tls.key",
    new string(PemEncoding.Write("PRIVATE KEY", pkcs8PrivateKey));

...

private static byte[] ExportPrivateKey(RSA privateKey)
{
    try
    {
        // If it's plaintext exportable, just do the easy thing.
        return privateKey.ExportPkcs8PrivateKey();
    }
    catch (CryptographicException)
    {
    }

    using (RSA exportRewriter = RSA.Create())
    {
        // Only one KDF iteration is being used here since it's immediately being
        // imported again.  Use more if you're actually exporting encrypted keys.
        exportRewriter.ImportEncryptedPkcs8PrivateKey(
            "password",
            privateKey.ExportEncryptedPkcs8PrivateKey(
                "password",
                new PbeParameters(
                    PbeEncryptionAlgorithm.Aes128Cbc,
                    HashAlgorithmName.SHA256,
                    1)),
            out _);

        return exportRewriter.ExportPkcs8PrivateKey();
    }
}

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