CCKeyDerivationPBKDF on iOS5

Question

I'm trying to write a password encryption function into my app, following this article.

I wrote a function that runs the CCCalibratePBKDF function and outputs the number of rounds.

const uint32_t oneSecond = 1000;
uint rounds = CCCalibratePBKDF(kCCPBKDF2,
                               predictedPasswordLength,
                               predictedSaltLength,
                               kCCPRFHmacAlgSHA256,
                               kCCKeySizeAES128,
                               oneSecond);

This works perfectly, but when I try to implement the next part it all goes wrong.

I can start writing the CCKeyDerivationPBKDF function call and it auto-completes the function and all the parameters. As I go through filling it in all the parameters are also auto-completed.

- (NSData *)authenticationDataForPassword: (NSString *)password salt: (NSData *)salt rounds: (uint) rounds
{
    const NSString *plainData = @"Fuzzy Aliens";
    uint8_t key[kCCKeySizeAES128] = {0};
    int keyDerivationResult = CCKeyDerivationPBKDF(kCCPBKDF2,
                                                   [password UTF8String],
                                                   [password lengthOfBytesUsingEncoding: NSUTF8StringEncoding],
                                                   [salt bytes],
                                                   [salt length],
                                                   kCCPRFHmacAlgSHA256,
                                                   rounds,
                                                   key,
                                                   kCCKeySizeAES128);
    if (keyDerivationResult == kCCParamError) {
        //you shouldn't get here with the parameters as above
        return nil;
    }
    uint8_t hmac[CC_SHA256_DIGEST_LENGTH] = {0};
    CCHmac(kCCHmacAlgSHA256,
           key,
           kCCKeySizeAES128,
           [plainData UTF8String],
           [plainData lengthOfBytesUsingEncoding: NSUTF8StringEncoding],
           hmac);
    NSData *hmacData = [NSData dataWithBytes: hmac length: CC_SHA256_DIGEST_LENGTH];
    return hmacData;
}

But as soon as I hit ; it marks an error saying "No matching function for call to 'CCKeyDerivationPBKDF'" and it won't build or anything.

I've imported CommonCrypto/CommonKeyDerivation.h and CommonCrypto/CommonCryptor.h as both of these were necessary for the enum names.

Answer 1

First, make sure that you haven't done anything funny with your include path (in particular, I do not recommend @HachiEthan's solution, which just confuses things). In general, leave this alone, and specifically don't add things like /usr/include to it. Make sure you've added Security.framework to your link step. This is the usual cause of problems.

The biggest thing you want to be sure of is that you're getting the iOS 5 Security.framework (rather than some other version like the OS X 10.6 or iOS 4 versions). But my suspicion is that you have a problem with your build settings.

If you want to see a framework that does all of this for reference, take a look at RNCryptor.