Delphi ActiveX

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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var
success: Integer;
ftp: TChilkatFtp2;

begin
success := 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.

ftp := TChilkatFtp2.Create(Self);

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 := 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.
ftp.SetSslCertRequirement('SubjectCN','ftp.example.com');

success := ftp.Connect();
if (success = 0) then
  begin
    Memo1.Lines.Add(ftp.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add('Connected; server certificate met the requirement.');

success := ftp.Disconnect();
if (success = 0) then
  begin
    Memo1.Lines.Add(ftp.LastErrorText);
    Exit;
  end;