在C＃中验证SSL证书

Question

I'm downloading files from a FTPS server and the server sends a certificate back to me.

Microsoft states:

When custom validation is not used, the certificate name is compared with host name used to create the request. For example, if Create(String) was passed a parameter of "https://www.contoso.com/default.hmtl", the default behavior is for the client to check the certificate against www.contoso.com.

The certificate does not pass the default validation (RemoteCertificateNameMismatch). Right now I use the ServicePointManager.ServerCertificateValidationCallback delegate and provide a delegate that returns true, just "to pass" without any validation. How do I validate the certificate using C#?

One of the parameters to the delgate mentioned above, X509Certificate certificate, contains two public properties of interest: Issuer and Subject. None of the two properties contains any data matching the hostname.

Answer 1

Usually you must have a valid certificate against the right host name to pass the validation instead of overwriting the callback. What target address did you use to access the FTP server? It should be different from the subject according to your description. You may consider to use the subject hostname to access the server instead of current one. You could also set your client hosts file if you have DNS issues with that.