CkPython

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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import sys
import chilkat

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 = chilkat.CkMailMan()

#  Configure the SMTP server connection.
mailman.put_SmtpHost("smtp.example.com")
mailman.put_SmtpPort(465)
mailman.put_SmtpSsl(True)
mailman.put_SmtpUsername("user@example.com")
mailman.put_SmtpPassword("myPassword")

#  Load the client certificate (with its private key) from a PFX file.
cert = chilkat.CkCert()
success = cert.LoadPfxFile("qa_data/certs/client.pfx","pfx_password")
if (success == False):
    print(cert.lastErrorText())
    sys.exit()

#  Use this certificate to identify the client during the TLS handshake.
success = mailman.SetSslClientCert(cert)
if (success == False):
    print(mailman.lastErrorText())
    sys.exit()

success = mailman.VerifySmtpLogin()
if (success == False):
    print(mailman.lastErrorText())
    sys.exit()

print("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.