C#

HTTPS Server Certificate Require Hostname Match

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Demonstrates and explains the RequireHostnameMatch property. C#

//  The RequireHostnameMatch property was added in Chilkat v11.0.0
//  to ensure the URL's hostname matches at least one of the server certificate SAN's (Subject Alternative Names)
//  
//  In actuality, it is the SNI hostname that must match.  If the SNI hostname is not explicitly set,
//  then Chilkat uses the hostname from the URL as the SNI hostname.

//  Here's an example using chilkatsoft.com
//  The SSL server certificate for chilkatsoft.com has 2 Subject Alternative Names:
//  
//  1) DNS Name: *.chilkatsoft.com
//  2) DNS Name: chilkatsoft.com
//  
//  See Explaining the SNI Hostname in TLS

Chilkat.Http http = new Chilkat.Http();

http.RequireHostnameMatch = true;

//  This should succeed because "www.chilkatsoft.com" matches the SAN entry "*.chilkatsoft.com"
string html = http.QuickGetStr("https://www.chilkatsoft.com/helloWorld.html");
Debug.WriteLine("1) Succeeded: " + Convert.ToString(http.LastMethodSuccess));

//  At the time of writing this example, the IP address for chilkatsoft.com is 3.101.18.47
//  If we send the request using the IP address, it will fail because the IP address is does 
//  not match any of the SAN entries in the server certificate.
html = http.QuickGetStr("https://3.101.18.47/helloWorld.html");
Debug.WriteLine("2) Succeeded: " + Convert.ToString(http.LastMethodSuccess));

//  However, it will succeed if we explicitly set the SNI hostname.
http.SniHostname = "www.chilkatsoft.com";
html = http.QuickGetStr("https://3.101.18.47/helloWorld.html");
Debug.WriteLine("3) Succeeded: " + Convert.ToString(http.LastMethodSuccess));

//  Remove our explicit SNI hostname.
http.SniHostname = "";

//  Now let's try wrong.host.badssl.com
//  The SSL server certificate for badssl.com has 2 Subject Alternative Names:
//  
//  1) DNS Name: *.badssl.com
//  2) DNS Name: badssl.com

//  The domain wrong.host.badssl.com will fail the RequireHostnameMatch because
//  the wildcarded domain SAN entry only extends 1 level deep.  
html = http.QuickGetStr("https://wrong.host.badssl.com/");
Debug.WriteLine("4) Succeeded: " + Convert.ToString(http.LastMethodSuccess));

//  The expected output is:
//  1) Succeeded: True
//  2) Succeeded: False
//  3) Succeeded: True
//  4) Succeeded: False