Azure Key Vault - 从 Key Vault 下载原始 PFX

Question

我对 Key Vault 和证书不太了解，并且正在解决一个问题。我正在利用 PFX 文件生成 JWT token 来调用外部 Web 服务。它工作正常。现在我需要将 PFX 存储在 Key Vault 中并执行相同的操作。

我正在使用 Az DevOps 和 Az Cli 命令上传证书

az keyvault certificate import --file $(filename.secureFilePath) --name pfx-cert-name --vault-name "keyvault-name" --password "password"

现在，当我尝试在 .net core 中使用 PFX 时。我正在使用 CertificateClient 类和 GetCertificateAsync 方法来获取 PFX 文件的字节数组。

var client = new CertificateClient(new Uri(kvUri), new DefaultAzureCredential());            var cert = await client.GetCertificateAsync(certName);
certInBytes = cert.Value.Cer;

代码失败。在线阅读后，我明白了这是因为“获取证书”获取了 PFX 文件的公共(public)详细信息。因此，我开始在线阅读并使用 powershell 上的 Az Cli 命令进行导入和下载。

我尝试了另一种技术来使用以下命令下载 PFX 的原始形式:

az keyvault secret download --file inputCert.pfx --vault-name keyvault-name --encoding base64 --name pfx-cert-name

该命令给了我另一个 pfx，但它仍然不是 PFX 的原始形式。当我尝试使用此证书获取 JWT token 时，收到密码无效的错误。

我有两个替代方案，但我不想使用其中任何一个，因为它们都不是干净的解决方案:

1. 将 PFX 字节数组作为 key 存储在 keystore 中
2. 存储 pfx 字节数组的 Base 64 编码版本以提高安全性。

Answer 1

要获取带有私钥的证书，您需要将其下载为 secret ，而不是证书。是的，这听起来确实很奇怪，你就是这样做的。

这是我用来从 AKV 下载带有私钥的证书的代码:

/// <summary>
/// Load a certificate (with private key) from Azure Key Vault
///
/// Getting a certificate with private key is a bit of a pain, but the code below solves it.
/// 
/// Get the private key for Key Vault certificate
/// https://github.com/heaths/azsdk-sample-getcert
/// 
/// See also these GitHub issues: 
/// https://github.com/Azure/azure-sdk-for-net/issues/12742
/// https://github.com/Azure/azure-sdk-for-net/issues/12083
/// </summary>
/// <param name="config"></param>
/// <param name="certificateName"></param>
/// <returns></returns>
public static X509Certificate2 LoadCertificate(IConfiguration config, string certificateName)
{
    string vaultUrl = config["Vault:Url"] ?? "";
    string clientId = config["Vault:ClientId"] ?? "";
    string tenantId = config["Vault:TenantId"] ?? "";
    string secret = config["Vault:ClientSecret"] ?? "";

    Console.WriteLine($"Loading certificate '{certificateName}' from Azure Key Vault");

    var credentials = new ClientSecretCredential(tenantId: tenantId, clientId: clientId, clientSecret: secret);
    var certClient = new CertificateClient(new Uri(vaultUrl), credentials);
    var secretClient = new SecretClient(new Uri(vaultUrl), credentials);

    var cert = GetCertificateAsync(certClient, secretClient, certificateName);

    Console.WriteLine("Certificate loaded");
    return cert;
}


/// <summary>
/// Helper method to get a certificate
/// 
/// Source https://github.com/heaths/azsdk-sample-getcert/blob/master/Program.cs
/// </summary>
/// <param name="certificateClient"></param>
/// <param name="secretClient"></param>
/// <param name="certificateName"></param>
/// <returns></returns>
private static X509Certificate2 GetCertificateAsync(CertificateClient certificateClient,
                                                        SecretClient secretClient,
                                                        string certificateName)
{

    KeyVaultCertificateWithPolicy certificate = certificateClient.GetCertificate(certificateName);

    // Return a certificate with only the public key if the private key is not exportable.
    if (certificate.Policy?.Exportable != true)
    {
        return new X509Certificate2(certificate.Cer);
    }

    // Parse the secret ID and version to retrieve the private key.
    string[] segments = certificate.SecretId.AbsolutePath.Split('/', StringSplitOptions.RemoveEmptyEntries);
    if (segments.Length != 3)
    {
        throw new InvalidOperationException($"Number of segments is incorrect: {segments.Length}, URI: {certificate.SecretId}");
    }

    string secretName = segments[1];
    string secretVersion = segments[2];

    KeyVaultSecret secret = secretClient.GetSecret(secretName, secretVersion);

    // For PEM, you'll need to extract the base64-encoded message body.
    // .NET 5.0 preview introduces the System.Security.Cryptography.PemEncoding class to make this easier.
    if ("application/x-pkcs12".Equals(secret.Properties.ContentType, StringComparison.InvariantCultureIgnoreCase))
    {
        byte[] pfx = Convert.FromBase64String(secret.Value);
        return new X509Certificate2(pfx);
    }

    throw new NotSupportedException($"Only PKCS#12 is supported. Found Content-Type: {secret.Properties.ContentType}");
}
}

上面的代码依赖于这些 NuGet 包:

• Azure.Security.KeyVault.Certificates
• Azure.Security.KeyVault.Keys
• Azure.Security.KeyVault.Secrets