PHP

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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<?php

use Chilkat2\Ftp2;

// 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.

$ftp = new Ftp2();

$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('SubjectCN', 'ftp.example.com');

try {
    $ftp->Connect();
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

echo "Connected; server certificate met the requirement.\n";

try {
    $ftp->Disconnect();
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}