VB.NET

Verify and Pin the FTPS Server Certificate

Demonstrates the certificate-verification properties RequireSslCertVerify, TlsPinSet, and the read-only SslServerCertVerified.

Background: By default a TLS connection is not rejected merely because certificate-chain verification fails, so RequireSslCertVerify = true is the important hardening step — it makes an expired, unsigned, or untrusted certificate abort the connection. TlsPinSet adds public-key pinning on top: the handshake fails unless the server's SPKI fingerprint matches one you configured, defending against a mis-issued certificate that would otherwise validate. Pinning supplements verification rather than replacing it. SslServerCertVerified reports the outcome.

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Dim success As Boolean = False

Dim ftp As New Chilkat.Ftp2

ftp.Hostname = "ftp.example.com"
ftp.Username = "myFtpLogin"

ftp.AuthTls = True

'  Normally you would not hard-code the password in source.  You should instead obtain it
'  from an interactive prompt, environment variable, or a secrets vault.
ftp.Password = "myPassword"

'  Reject the connection if the server certificate cannot be verified (expired, bad signature,
'  untrusted chain, etc.).  The default is False, which does not reject on verification
'  failure -- set True for security.
ftp.RequireSslCertVerify = True

'  Optionally pin the server's public key.  If none of the configured SPKI fingerprints matches,
'  the TLS handshake fails.  Pinning supplements normal verification; it does not replace it.
ftp.TlsPinSet = "sha256//YLh1dUR9y6Kja30RrAn7JKnbQG/uEtLMkBgFF2Fuihg="

success = ftp.Connect()
If (success = False) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If


'  SslServerCertVerified reports whether the certificate chain was successfully verified.
If (ftp.SslServerCertVerified) Then
    Debug.WriteLine("The server certificate was verified.")
End If


success = ftp.Disconnect()
If (success = False) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If