How to generate ds:X509Certificate value from .p12 in Objective-C?

Question

I've a private key file .p12.
I'm using Objective-C.

I need to generate Signed digital signature XML like this:

The problem is, I cannot find out how to generate the value in <ds:X509Certificate>. I know it is a public key base64 encoded. But, I can't get the same string after testing various encoding methods..

Need your help!

Answer 1

Found the solution myself. It is so easy.

Using Apple's security.framework:

NSString* pfile = [[NSBundle mainBundle] pathForResource:@"rsa_user" ofType:@"p12" ];

// Load Certificate
NSData *p12data = [NSData dataWithContentsOfFile:pfile];
CFDataRef inP12data = (__bridge CFDataRef)p12data;

SecIdentityRef myIdentity;
SecTrustRef myTrust;
extractIdentityAndTrust(inP12data, &myIdentity, &myTrust);

SecCertificateRef myCertificate;
SecIdentityCopyCertificate(myIdentity, &myCertificate);
NSData *certificateData = (__bridge NSData *) SecCertificateCopyData(myCertificate);

// Output certificate base64 value. (This value goes to <ds:X509Certificate> tag )
NSLog(@"%@", [certificateData base64EncodedString]);

// Helper function

OSStatus extractIdentityAndTrust(CFDataRef inP12data, SecIdentityRef *identity, SecTrustRef *trust)
{
    OSStatus securityError = errSecSuccess;

    CFStringRef password = CFSTR("password");
    const void *keys[] = { kSecImportExportPassphrase };
    const void *values[] = { password };

    CFDictionaryRef options = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);

    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    securityError = SecPKCS12Import(inP12data, options, &items);

    if (securityError == 0) {
        CFDictionaryRef myIdentityAndTrust = CFArrayGetValueAtIndex(items, 0);
        const void *tempIdentity = NULL;
        tempIdentity = CFDictionaryGetValue(myIdentityAndTrust, kSecImportItemIdentity);
        *identity = (SecIdentityRef)tempIdentity;
        const void *tempTrust = NULL;
        tempTrust = CFDictionaryGetValue(myIdentityAndTrust, kSecImportItemTrust);
        *trust = (SecTrustRef)tempTrust;
    }

    if (options) {
        CFRelease(options);
    }

    return securityError;
}