(Objective-C) Duplicate OpensSSL to Sign File and Output Binary DER

This example duplicates the following:

openssl smime -sign -in INPUT.xml -signer SIGN.PEM -passin pass:MYPASS -outform der -binary -nodetach -out SIGNED.P7M

Note: Although "smime" is the OpenSSL command, it's not actually producing S/MIME. The arguments "-outform der -binary" indicates that the output is binary DER (i.e. the PKCS7 binary signature). The input can be any type of file: XML, PDF, JPG, ... *anything*...

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#import <CkoCrypt2.h>
#import <CkoPem.h>
#import <CkoPrivateKey.h>
#import <CkoCert.h>

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

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];

// Load the PEM containing cert + private key.
CkoPem *pem = [[CkoPem alloc] init];
BOOL success = [pem LoadPemFile: @"qa_data/pem/myPem.pem" password: @"password"];
if (success != YES) {
    NSLog(@"%@",pem.LastErrorText);
    return;
}

CkoPrivateKey *privkey = [pem GetPrivateKey: [NSNumber numberWithInt: 0]];
if (pem.LastMethodSuccess != YES) {
    NSLog(@"%@",pem.LastErrorText);
    return;
}

CkoCert *cert = [pem GetCert: [NSNumber numberWithInt: 0]];
if (pem.LastMethodSuccess != YES) {

    NSLog(@"%@",pem.LastErrorText);
    return;
}

success = [crypt SetSigningCert2: cert key: privkey];
if (success != YES) {

    NSLog(@"%@",crypt.LastErrorText);
    return;
}

// Alternatively, we could use a .pfx/.p12 file.
// (Chilkat also supports other formats/sources for cert/private keys...)
CkoCert *certFromP12 = [[CkoCert alloc] init];
success = [certFromP12 LoadPfxFile: @"qa_data/p12/myP12.p12" password: @"password"];
if (success != YES) {
    NSLog(@"%@",certFromP12.LastErrorText);
    return;
}

// The certificate, when loaded from a .pfx/.p12, will automatically 
// include the associated private key, assuming it's present in the .p12.
// We don't have to explicitly provide the private key as in the
// lines of code above that use the PEM file.
success = [crypt SetSigningCert: certFromP12];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

// Create the opaque signature (PKCS7 binary DER that contains both the signature and original file data).
success = [crypt CreateP7M: @"qa_data/infile.anything" p7mPath: @"qa_output/outfile.p7m"];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

NSLog(@"%@",@"Success.");