.net - .Net 编程：在 SSL 自签名证书上验证什么

Question

我无法让用户为他们的服务器创建真正的证书，但我想做一些安全检查。所以以下内容太轻了，因为在我阅读时，没有检查证书。

ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };

你有什么建议让客户检查 x509 证书？鉴于我使用的是 .NET 语言 (c#/f#)。

Answer 1

If you're using self signed certs then the only errors you should expect is a chain error on the root (Cert. Issuer). I would suggest something like this that traps for that chain error specifically and lets all other errors fall through.

ServicePointManager.ServerCertificateValidationCallback += new RemoteCertificateValidationCallback(
    ValidateRemoteCertificate
);

private static bool ValidateRemoteCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors policyErrors )
{
    string trustedIssuer = "CN=www.domain.com";
    string trustedDomain = "CN=www.domain.com";
    bool policyErr = false;

    switch (policyErrors)
    {
        case SslPolicyErrors.None:
            policyErr |= false;
            break;
        case SslPolicyErrors.RemoteCertificateChainErrors:
            bool chainErr = false;
            foreach (X509ChainStatus status in chain.ChainStatus)
            {
                switch (status.Status)
                {
                    case X509ChainStatusFlags.NoError:
                        chainErr |= false;
                        break;
                    case X509ChainStatusFlags.UntrustedRoot:
                        if (certificate.Subject != trustedDomain || certificate.Issuer != trustedIssuer)
                            chainErr |= true;
                        else
                            chainErr |= false;
                        break;
                    default:
                        chainErr |= true;
                        break;
                }                    
            }
            policyErr |= chainErr;
            break;
        default:
            policyErr |= true;
            break;
    }

    return !policyErr;
}

Answer 2

如果您无法让客户端创建真正的证书，您至少应该尝试让他们使用您的服务器创建证书。然后您可以检查证书是否有效或至少来自您的 CA，因为您会知道您的 CA 是否已被盗用。如果您信任任何和所有 CA，那么确实没有什么值得检查的。

Answer 3

如果您可以检查证书，您可以将自己的验证逻辑放入函数 ValidateRemoteCertificate

System.Net.ServicePointManager.ServerCertificateValidationCallback += (a, b, c, d) =>
{
     return ValidateRemoteCertificate(a, b, c, d);
};

private static bool ValidateRemoteCertificate(object sender, X509Certificate certificate,
            X509Chain chain, SslPolicyErrors policyErrors)
{
            if (certificate.Subject.Equals("CN=www.domain.com"))
                return true;
            else
               return policyErrors == SslPolicyErrors.None; 

}