Get informations of the certificate (OS X)

// openssl x509 -inform der -outform pem -in public_key.der -out public_key.pem
// openssl pkcs12 -export -in public_key.pem -inkey private_key.pem -out private_key.p12

NSDictionary *info = [NSDictionary new];
[self getX509InfoWithName:@"your-cert.p12" password:@"cert-password" info:&info];
NSLog(@"X509 Infos: %@", info);

#pragma mark - X509

- (void)getX509InfoWithName:(NSString*)certificateName password:(NSString*)password info:(NSDictionary**)info
{
    NSString *p12Path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:certificateName];
    NSData *p12Data = [[NSData alloc] initWithContentsOfFile:p12Path];

    CFStringRef p12Password = (__bridge CFStringRef)password;
    const void *keys[] = { kSecImportExportPassphrase };
    const void *values[] = { p12Password };
    CFDictionaryRef optionsDictionary = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
    CFArrayRef p12Items;
    OSStatus result = SecPKCS12Import((__bridge CFDataRef)p12Data, optionsDictionary, &p12Items);
    CFRelease(optionsDictionary);

    if(result == noErr) {
        NSDictionary *item = (NSDictionary*)CFArrayGetValueAtIndex(p12Items, 0);
        SecCertificateRef cert = (SecCertificateRef)CFArrayGetValueAtIndex((__bridge CFArrayRef)[item objectForKey:(__bridge NSString*)kSecImportItemCertChain], 0);

        *info = [self dictionaryFromCerificateWithLongDescription:cert];
    }
}

- (NSDictionary*)dictionaryFromCerificateWithLongDescription:(SecCertificateRef)certificateRef {

    NSMutableDictionary *dict = [NSMutableDictionary new];

    if (certificateRef == NULL)
        return dict;

#if TARGET_OS_MAC

    const void *keys[] = { kSecOIDX509V1SubjectName, kSecOIDX509V1IssuerName, kSecOIDX509V1SerialNumber, kSecOIDX509V1Signature };
    CFArrayRef keySelection = CFArrayCreate(NULL, keys , sizeof(keys)/sizeof(keys[0]), &kCFTypeArrayCallBacks);

    CFErrorRef error;
    CFDictionaryRef vals = SecCertificateCopyValues(certificateRef, keySelection, &error);

    for(int i = 0; i < sizeof(keys)/sizeof(keys[0]); i++) {
        CFDictionaryRef dict_values = CFDictionaryGetValue(vals, keys[i]);
        CFStringRef label = CFDictionaryGetValue(dict_values, kSecPropertyKeyLabel);
        if (CFEqual(label, CFSTR("Serial Number"))) {
            CFStringRef value = CFDictionaryGetValue(dict_values, kSecPropertyKeyValue);
            if (value == NULL)
                continue;
            [dict setObject:(__bridge NSString*)(value) forKey:(__bridge NSString*)label];
        } else if (CFEqual(label, CFSTR("Signature"))) {
            CFDataRef value = CFDictionaryGetValue(dict_values, kSecPropertyKeyValue);
            if (value == NULL)
                continue;
            [dict setObject:(__bridge NSData*)(value) forKey:(__bridge NSString*)label];
        } else {
            CFArrayRef values = CFDictionaryGetValue(dict_values, kSecPropertyKeyValue);
            if (values == NULL)
                continue;
            [dict setObject:[self dictionaryFromDNwithSubjectName:values] forKey:(__bridge NSString*)label];
        }
    }

    CFRelease(vals);

#endif

    return dict;
}

- (NSDictionary*)dictionaryFromDNwithSubjectName:(CFArrayRef)array {

    NSMutableDictionary *dict = [NSMutableDictionary new];

#if TARGET_OS_MAC

    const void *keys[] = { kSecOIDCommonName, kSecOIDEmailAddress, kSecOIDOrganizationalUnitName, kSecOIDOrganizationName, kSecOIDLocalityName, kSecOIDStateProvinceName, kSecOIDCountryName };
    NSArray *labels = [NSArray arrayWithObjects:@"CN", @"E", @"OU", @"O", @"L", @"S", @"C", @"E", nil];

    for(int i = 0; i < sizeof(keys)/sizeof(keys[0]);  i++) {
        for (CFIndex n = 0 ; n < CFArrayGetCount(array); n++) {
            CFDictionaryRef dict_values = CFArrayGetValueAtIndex(array, n);
            if (CFGetTypeID(dict_values) != CFDictionaryGetTypeID())
                continue;
            CFTypeRef dictkey = CFDictionaryGetValue(dict_values, kSecPropertyKeyLabel);
            if (!CFEqual(dictkey, keys[i]))
                continue;
            CFStringRef str = (CFStringRef) CFDictionaryGetValue(dict_values, kSecPropertyKeyValue);
            [dict setObject:(__bridge  NSString*)str forKey:labels[i]];
        }
    }

#endif

    return dict;
}