(Objective-C) IMAP Download and Verify Signed (S/MIME) Email

Demonstrates how to download and verify digitally signed S/MIME email.

Note: This example requires Chilkat v11.0.0 or greater.

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#import <CkoImap.h>
#import <CkoMessageSet.h>
#import <CkoEmail.h>
#import <CkoCert.h>
#import <NSString.h>

BOOL success = NO;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

CkoImap *imap = [[CkoImap alloc] init];

// Connect to an IMAP server.
// Use TLS
imap.Ssl = YES;
imap.Port = [NSNumber numberWithInt:993];
success = [imap Connect: @"imap.example.com"];
if (success == NO) {
    NSLog(@"%@",imap.LastErrorText);
    return;
}

success = [imap Login: @"myLogin" password: @"myPassword"];
if (success == NO) {
    NSLog(@"%@",imap.LastErrorText);
    return;
}

// Select an IMAP mailbox
success = [imap SelectMailbox: @"Inbox"];
if (success == NO) {
    NSLog(@"%@",imap.LastErrorText);
    return;
}

// We can choose to fetch UIDs or sequence numbers.
BOOL fetchUids = YES;

// Get the message IDs of all the emails in the mailbox
CkoMessageSet *messageSet = [[CkoMessageSet alloc] init];
success = [imap QueryMbx: @"ALL" bUid: fetchUids msgSet: messageSet];
if (success == NO) {
    NSLog(@"%@",imap.LastErrorText);
    return;
}

CkoEmail *email = [[CkoEmail alloc] init];
CkoCert *cert = [[CkoCert alloc] init];

int i = 0;
while (i < [messageSet.Count intValue]) {

    NSString *uid = [messageSet GetId: [NSNumber numberWithInt: i]];
    NSLog(@"%@%@",@"uid: ",uid);

    success = [imap FetchEmail: NO msgId: uid bUid: YES email: email];
    if (success == NO) {
        NSLog(@"%@",imap.LastErrorText);
        return;
    }

    // The security layers of signed and/or encrypted emails
    // are automatically "unwrapped" when loaded into
    // a Chilkat email object.
    // An application only needs to check to see if an email
    // was received signed or encrypted, and then examine
    // the success/failure.  For example:
    if (email.ReceivedSigned == YES) {

        NSLog(@"%@",@"This email was signed.");

        // Check to see if the signatures were verified.
        if (email.SignaturesValid == YES) {
            NSLog(@"%@",@"Digital signature(s) verified.");
            NSLog(@"%@%@",@"Signer: ",email.SignedBy);

            // Get the certificate used for signing.
            success = [email LastSignerCert: [NSNumber numberWithInt: 0] cert: cert];

            if (success == NO) {
                NSLog(@"%@",@"Failed to get signing certificate object.");
            }
            else {
                NSLog(@"%@%@",@"Signing cert: ",cert.SubjectCN);
            }

        }
        else {
            NSLog(@"%@",@"Digital signature verification failed.");
        }

    }

    i = i + 1;
}

// Disconnect from the IMAP server.
success = [imap Disconnect];