(Objective-C) Convert Java KeyStore to PKCS12 / PFX

Loads a Java keystore file and saves it as a PKCS12 / PFX. A Java keystore (JKS) can contain two types of entries: (1) trusted root certificates or (2) private keys + cert chains. Usually a JKS will contain all entries of one type or another (and thus a particular JKS serves one purpose or another; meaning that a JKS containing trusted roots is used as a source for verifying pre-trusted roots, and a JKS containing private keys (and cert chains) is used as a secure, encrypted store for private keys).

A PKCS12 / PFX typically contains one or more private keys, along with each private key's certificate chain. Therefore, it typically makes sense to only write the private key entries to a PKCS12 (and the associated certificate chains). If a JKS contains trusted root certificates, it makes more sense to conver it to a PEM file (such as the CA cert bundle in PEM format from mozilla.org).

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#import <CkoJavaKeyStore.h>
#import <NSString.h>
#import <CkoPfx.h>
#import <CkoPrivateKey.h>
#import <CkoCertChain.h>

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

CkoJavaKeyStore *jks = [[CkoJavaKeyStore alloc] init];

NSString *jksPassword = @"myJksPassword";

// Load the Java keystore from a file.  The JKS file password is used
// to verify the keyed digest that is found at the very end of the keystore.
// It verifies that the keystore has not been modified.
BOOL success = [jks LoadFile: jksPassword path: @"/someDir/keyStore.jks"];
if (success != YES) {
    NSLog(@"%@",jks.LastErrorText);
    return;
}

// To convert, we'll access the private key entries
// from the JKS, add each to the PKCS12, and then save the PKCS12.
CkoPfx *pkcs12 = [[CkoPfx alloc] init];

int numPrivateKeys = [jks.NumPrivateKeys intValue];
int i;

CkoPrivateKey *privKey = 0;
CkoCertChain *certChain = 0;

// For each private key entry, get the private key and
// the associated certificate chain.
// Each private key is password protected.  Usually it is the same
// password as used for the keyed digest of the entire JKS.  
// However, this does not have to be.  The password is passed
// here to handle the possibility of each private key requiring
// a different password.
i = 0;
while (i < numPrivateKeys) {
    privKey = [jks GetPrivateKey: jksPassword index: [NSNumber numberWithInt: i]];
    NSLog(@"%@",[jks GetPrivateKeyAlias: [NSNumber numberWithInt: i]]);
    certChain = [jks GetCertChain: [NSNumber numberWithInt: i]];

    // Add the private key and it's associated certificate chain to the PKCS12.
    success = [pkcs12 AddPrivateKey: privKey certChain: certChain];
    if (success != YES) {
        NSLog(@"%@",pkcs12.LastErrorText);

        return;
    }

    i = i + 1;
}

// Save the PKCS12 / PFX to a file.
// The password can be the same as the JKS password, or something new.
// (With the PKCS12 format, there is a single password for the entire contents
// of the file.  With the JKS format, there is flexibility in allowing each private key
// to have it's own password.)
NSString *pkcs12Password = @"myNewPassword";
success = [pkcs12 ToFile: pkcs12Password path: @"/pkcs12_files/myPfx.p12"];
if (success != YES) {
    NSLog(@"%@",pkcs12.LastErrorText);
}
else {
    NSLog(@"%@",@"Successfully saved to PKCS12 format.");
}