(VB.NET) HTTPS Server Certificate Require Hostname Match

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Note: This example requires Chilkat v11.0.0 or greater.

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' 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


Dim http As New Chilkat.Http

http.RequireHostnameMatch = True

' This should succeed because "www.chilkatsoft.com" matches the SAN entry "*.chilkatsoft.com"
Dim html As String = http.QuickGetStr("https://www.chilkatsoft.com/helloWorld.html")
Debug.WriteLine("1) Succeeded: " & 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: " & 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: " & 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: " & http.LastMethodSuccess)


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