objective-c implementation of mySQL encrypt() function - mysql

Question

I have a mySQL database with hashed passwords that I cannot abandon. I need to duplicate the encrypt() function of mySQL so that I can be consistent in my hash creation for login in an iOS app I'm creating. (I'm using the first 2 characters of the password as the salt for the encrypt function)
Has anyone done this before? I tried to add the following category to NSString based on code I found elsewhere, but the resulting string isn't even close. (I have a base64 category on NSData and yes, I'm new to the CCCrypt call)
-(NSString*) encryptWithSalt:(NSString *)salt {
NSString *token = self;
const void *vplainText;
size_t plainTextBufferSize = [token length];
vplainText = (const void *) [token UTF8String];
CCCryptorStatus ccStatus;
uint8_t *bufferPtr = NULL;
size_t bufferPtrSize = 0;
size_t movedBytes = 0;
bufferPtrSize = (plainTextBufferSize + kCCBlockSizeDES) & ~(kCCBlockSizeDES - 1);
bufferPtr = malloc( bufferPtrSize * sizeof(uint8_t));
memset((void *)bufferPtr, 0x0, bufferPtrSize);
uint8_t iv[kCCBlockSizeDES];
memset((void *) iv, 0x0, (size_t) sizeof(iv)); // zero out iv
const void *vkey = (const void *) [salt UTF8String];
ccStatus = CCCrypt(kCCEncrypt,
kCCAlgorithmDES,
kCCOptionPKCS7Padding | kCCModeCBC,
vkey,
kCCKeySizeDES,
iv,
vplainText,
plainTextBufferSize,
(void *)bufferPtr,
bufferPtrSize,
&movedBytes);
NSData *myData = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes];
NSString* hash;
if (ccStatus == kCCSuccess) {
hash = [myData base64EncodedString];
}
return hash;
}

Answer 1

The crypt() function cannot be emulated using CCCrypt, as the salt is used to alter the DES E-box. This makes the cipher in use no longer really DES.
However, it's still just the crypt() function. Call it directly:
- (NSString*) encryptWithSalt:(NSString *)salt {
return [NSString stringWithUTF8String:crypt([self UTF8String], [salt UTF8String])];
}
Incidentally, using the first two characters of the password as the salt is a gigantic security hole, as it narrows the password search space down to six characters (because the first two are given away by the salt).