Swift

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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Swift


func chilkatTest() {
    var success: Bool = false

    //  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.

    let ftp = CkoFtp2()!

    ftp.hostname = "ftp.example.com"
    ftp.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.
    ftp.password = "myPassword"

    //  Use explicit FTPS (AUTH TLS) on the standard FTP port.
    ftp.authTls = true

    //  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.
    ftp.setSslCertRequirement(name: "SubjectCN", value: "ftp.example.com")

    success = ftp.connect()
    if success == false {
        print("\(ftp.lastErrorText!)")
        return
    }

    print("Connected; server certificate met the requirement.")

    success = ftp.disconnect()
    if success == false {
        print("\(ftp.lastErrorText!)")
        return
    }


}