Objective-C

Get the SMTP or POP3 Server's TLS Certificate

Demonstrates the Chilkat MailMan.GetServerCert method, which gets the digital certificate presented by the SMTP or POP3 server for the current SSL/TLS connection and stores it in a Cert object. Pass true for the SMTP server's certificate or false for the POP3 server's. This example connects to the SMTP server and prints the certificate's subject and issuer.

Background: During a TLS handshake the server presents a certificate proving its identity, and the client validates it against trusted authorities. Retrieving that certificate lets you inspect it yourself — checking the subject, issuer, or expiration for auditing, logging, or certificate-pinning style checks. It must be called while a TLS connection is established, since the certificate belongs to that specific session.

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Objective-C

#import <CkoMailMan.h>
#import <CkoCert.h>

BOOL success = NO;

//  Demonstrates the MailMan.GetServerCert method, which gets the digital certificate
//  presented by the SMTP or POP3 server for the current SSL/TLS connection.  Pass true for
//  the SMTP server's certificate, or false for the POP3 server's certificate.

CkoMailMan *mailman = [[CkoMailMan alloc] init];

//  Configure the SMTP server connection.
mailman.SmtpHost = @"smtp.example.com";
mailman.SmtpPort = [NSNumber numberWithInt:465];
mailman.SmtpSsl = YES;
mailman.SmtpUsername = @"user@example.com";
mailman.SmtpPassword = @"myPassword";

//  Establish the TLS connection.
success = [mailman SmtpConnect];
if (success == NO) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

//  Get the certificate the SMTP server presented (useSmtp = cktrue).
CkoCert *cert = [[CkoCert alloc] init];
success = [mailman GetServerCert: YES cert: cert];
if (success == NO) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

NSLog(@"%@%@",@"Server certificate subject (CN): ",cert.SubjectCN);
NSLog(@"%@%@",@"Issued by: ",cert.IssuerCN);

success = [mailman CloseSmtpConnection];
if (success == NO) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}