Objective-C

Decrypt S/MIME and Verify S/MIME Signatures

See more MIME Examples

_LANGUAGE_ example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting. Objective-C

#import <CkoMime.h>
#import <CkoCert.h>

BOOL success = NO;

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

CkoMime *mime = [[CkoMime alloc] init];

//  Load an S/MIME message from a file:
success = [mime LoadMimeFile: @"signedMime.txt"];
if (success == NO) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

//  The ContainsEncryptedParts/ContainsSignedParts methods
//  can be called to determine if the MIME is encrypted and/or signed:
BOOL isEncrypted = [mime ContainsEncryptedParts];
BOOL isSigned = [mime ContainsSignedParts];

//  We don't want the "unwrap extras".  You'll see what those
//  are in a few moments...
mime.UnwrapExtras = NO;

//  To verify the signature, call UnwrapSecurity.  This will
//  verify the signature(s) and decrypt the S/MIME and restore
//  the MIME to the unsigned/unencrypted state.
//  The results of what was found are present in the MIME object's
//  properties, as well as extra header fields that are added
//  to the unwrapped MIME.
success = [mime UnwrapSecurity];
if (success != YES) {
    //  UnwrapSecurity returns true if all signatures were
    //  verified and all parts decrypted.
    NSLog(@"%@",mime.LastErrorText);
    return;
}

//  The mime.UnwrapExtras property controls whether or not
//  these additional fields are added to the unwrapped MIME:
//  
//  X-NumPartsSigned: 1
//  X-SignaturesValid: yes
//  X-NumPartsEncrypted: 1
//  X-Decrypted: no
//  
//  The X-NumPartsSigned/X-SignaturesValid headers are added
//  if the MIME was signed.  
//  
//  The X-NumPartsEncrypted/X-Decrypted headers are added
//  if the MIME was encrypted.
//  

//  If the MIME was signed, get the certificate used for signing.
if (isSigned == YES) {
    CkoCert *signerCert = [[CkoCert alloc] init];

    //  The NumSignerCerts property indicates how many certificates
    //  were used for signing.  This example will assume the value is 1.
    //  To get the 1st signer cert, call LastSignerCert with an index of 0:
    success = [mime LastSignerCert: [NSNumber numberWithInt: 0] cert: signerCert];
    if (success == YES) {
        NSLog(@"%@%@",@"**** Signer Cert: ",signerCert.SubjectCN);
    }

}

//  If the MIME was encrypted, get the certificate used for decryption
if (isEncrypted == YES) {
    //  The NumDecryptCerts property indicates how many certificates
    //  were used for decrypting.  This example will assume the value is 1.
    //  To get the 1st decrypt cert, call LastDecryptCert with an index of 0:
    CkoCert *decryptCert = [[CkoCert alloc] init];
    success = [mime LastDecryptCert: [NSNumber numberWithInt: 0] cert: decryptCert];
    if (success == YES) {
        NSLog(@"%@%@",@"**** Decrypt Cert: ",decryptCert.SubjectCN);
    }

}

//  Display the unwrapped MIME:
NSLog(@"%@",[mime GetMime]);

//  Save the unwrapped MIME to a file:
success = [mime SaveMime: @"unwrappedMime.txt"];