Visual FoxPro

Require Specific FTPS Server Certificate Fields

Demonstrates the Chilkat Ftp2.SetSslCertRequirement method, which adds a required match against the FTP server certificate. The first argument selects the certificate field (such as SubjectCN or IssuerCN) and the second is the required value. It is a void method; a non-matching certificate causes the connection to fail.

Background: Standard TLS validation confirms a certificate is trusted and valid for the hostname, but it does not guarantee you reached the specific server you expect — a form of pinning closes that gap. Requiring a certificate field to match a known value rejects any certificate that does not, defending against a mis-issued or substituted certificate even if it would otherwise pass validation. Multiple requirements can be added, and all must be satisfied.

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LOCAL lnSuccess
LOCAL loFtp

lnSuccess = 0

*  Demonstrates the Ftp2.SetSslCertRequirement method, which adds a required match against the FTP
*  server certificate.  The 1st argument selects the certificate field and the 2nd is the required
*  value.  It is a void method.

loFtp = CreateObject('Chilkat.Ftp2')

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

*  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.
loFtp.Password = "myPassword"

*  Use explicit FTPS (AUTH TLS) on the standard FTP port.
loFtp.AuthTls = 1

*  Require that the server certificate's subject common name matches an expected value.  If the
*  presented certificate does not match, the TLS connection fails.  Supported fields include
*  SubjectDN, SubjectCN, IssuerDN, IssuerCN, and others.
loFtp.SetSslCertRequirement("SubjectCN","ftp.example.com")

lnSuccess = loFtp.Connect()
IF (lnSuccess = 0) THEN
    ? loFtp.LastErrorText
    RELEASE loFtp
    CANCEL
ENDIF

? "Connected; server certificate met the requirement."

lnSuccess = loFtp.Disconnect()
IF (lnSuccess = 0) THEN
    ? loFtp.LastErrorText
    RELEASE loFtp
    CANCEL
ENDIF

RELEASE loFtp