Objective-C

Get an S/MIME Signing Time

Demonstrates the Chilkat Mime.GetSignatureSigningTimeStr method, which returns the CMS signingTime attribute for the signer at a zero-based index, as an RFC 822-style date string in GMT. The only argument is the signer index.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: This is the timestamp the signer asserted at signing — useful for "when was this signed" audit trails and for evaluating whether the signing certificate was valid at that moment. Because it is a signed attribute, it is tamper-evident. Guard the call with HasSignatureSigningTime, since the attribute is optional. Note it is the signer's claim, not a trusted third-party timestamp.

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Objective-C

#import <CkoMime.h>
#import <NSString.h>

BOOL success = NO;

CkoMime *mime = [[CkoMime alloc] init];
success = [mime LoadMimeFile: @"qa_data/signed.eml"];
if (success == NO) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

//  After verifying, get the CMS signingTime for each signer that has one, as an RFC 822 date string
//  in GMT.  The only argument is the zero-based signer index.
success = [mime Verify];
if (success != YES) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

int n = [mime.NumSignerCerts intValue];
int i;
for (i = 0; i <= n - 1; i++) {
    //  Only signers that included a signing time have one to retrieve.
    if ([mime HasSignatureSigningTime: [NSNumber numberWithInt: i]]) {
        NSString *signingTime = [mime GetSignatureSigningTimeStr: [NSNumber numberWithInt: i]];
        if (mime.LastMethodSuccess == NO) {
            NSLog(@"%@",mime.LastErrorText);
            return;
        }

        NSLog(@"%@%d%@%@",@"Signer ",i,@" signing time: ",signingTime);
    }

}