Delphi DLL

Use a TLS Client Certificate

Demonstrates the Chilkat MailMan.SetSslClientCert method, which sets the client-side certificate to use for SSL/TLS connections. This is typically not required — most SSL/TLS connections authenticate the server only. This example loads a client certificate from a PFX and uses it when connecting.

Background: In an ordinary TLS handshake only the server presents a certificate, and the client proves who it is later with a password. Mutual TLS adds a second leg: the client also presents a certificate, so it is authenticated cryptographically at the transport layer. Some corporate or high-security mail servers require this. Because the client must prove possession of the key, the certificate needs its private key — hence loading from a PFX.

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var
success: Boolean;
mailman: HCkMailMan;
cert: HCkCert;

begin
success := False;

//  Demonstrates the MailMan.SetSslClientCert method, which sets the client-side certificate
//  to use for SSL/TLS connections.  This is typically not required -- most SSL/TLS
//  connections authenticate the server only.

mailman := CkMailMan_Create();

//  Configure the SMTP server connection.
CkMailMan_putSmtpHost(mailman,'smtp.example.com');
CkMailMan_putSmtpPort(mailman,465);
CkMailMan_putSmtpSsl(mailman,True);
CkMailMan_putSmtpUsername(mailman,'user@example.com');
CkMailMan_putSmtpPassword(mailman,'myPassword');

//  Load the client certificate (with its private key) from a PFX file.
cert := CkCert_Create();
success := CkCert_LoadPfxFile(cert,'qa_data/certs/client.pfx','pfx_password');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

//  Use this certificate to identify the client during the TLS handshake.
success := CkMailMan_SetSslClientCert(mailman,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkMailMan__lastErrorText(mailman));
    Exit;
  end;

success := CkMailMan_VerifySmtpLogin(mailman);
if (success = False) then
  begin
    Memo1.Lines.Add(CkMailMan__lastErrorText(mailman));
    Exit;
  end;

Memo1.Lines.Add('Connected using a TLS client certificate.');

//  Note: The path "qa_data/certs/client.pfx" is a relative local filesystem path,
//  relative to the current working directory of the running application.

CkMailMan_Dispose(mailman);
CkCert_Dispose(cert);