(Objective-C) Duplicate OpensSSL Command that Decrypts Binary DER

This example duplicates the following:

openssl smime -decrypt -in INPUT_FILE -inform der -binary -out OUTPUT_FILE -recip PEM_CERT_AND_KEY -passin pass:PRIVKEY_PASSWORD

Note: Although "smime" is the OpenSSL command, we're not really dealing with S/MIME. The arguments "-inform der -binary" indicate that the input is simply the binary DER (i.e. the PKCS7 binary encrypted object). The output can be any type of file (whatever was encrypted).

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

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

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

crypt.CryptAlgorithm = @"pki";

CkoPem *pem = [[CkoPem alloc] init];
success = [pem LoadPemFile: @"qa_data/pem/myPem.pem" password: @"password"];
if (success == NO) {
    NSLog(@"%@",pem.LastErrorText);
    return;
}

CkoPrivateKey *privkey = [[CkoPrivateKey alloc] init];
success = [pem PrivateKeyAt: [NSNumber numberWithInt: 0] privKey: privkey];
if (success == NO) {
    NSLog(@"%@",pem.LastErrorText);
    return;
}

CkoCert *cert = [[CkoCert alloc] init];
success = [pem CertAt: [NSNumber numberWithInt: 0] cert: cert];
if (success == NO) {
    NSLog(@"%@",pem.LastErrorText);
    return;
}

success = [crypt SetDecryptCert2: cert key: privkey];
if (success == NO) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

success = [crypt CkDecryptFile: @"qa_data/infile.enc" destFile: @"qa_output/outfile.dat"];
if (success == NO) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

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