AES256 Encryption/Decryption Error+ IOS SDK 7

Question

I am using AES256 for security and store data in encryption form which is working fine in IOS 6 and below but when i have tested my app in IOS 7, I am not getting my data which was store previously. After debugs, i found decryption is not working is IOS 7 and return blank.

My Code as below:

- (NSData *)AES256DecryptWithKey:(NSString *)key {
// 'key' should be 32 bytes for AES256, will be null-padded otherwise

char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)


bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
// fetch key data
[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
 NSUInteger dataLength = [self length];
//See the doc: For block ciphers, the output size will always be less than or
//equal to the input size plus the size of one block.
//That's why we need to add the size of one block here
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);
size_t numBytesDecrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                      keyPtr, kCCKeySizeAES256,
                                      NULL /* initialization vector (optional) */,
                                      [self bytes], dataLength, /* input */
                                      buffer, bufferSize, /* output */
                                      &numBytesDecrypted);
if (cryptStatus == kCCSuccess) {
    //the returned NSData takes ownership of the buffer and will free it on deallocation
    return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
}
free(buffer); //free the buffer;
return nil;

}

Can you please help to get my data again in IOS 7?

Thanks

Answer 1

Found the solution on this problem on Apple Devforums.

- (NSData *)encrypt:(NSString *)key {
 // 'key' should be 32 bytes for AES256, will be null-padded otherwise
 char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
 bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)

 BOOL patchNeeded = ([key length] > kCCKeySizeAES256);
 if (patchNeeded) {
      key = [key substringToIndex:kCCKeySizeAES256]; // Ensure that the key isn't longer than what's needed (kCCKeySizeAES256)
 }

 // fetch key data
 [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

 if (patchNeeded) {
      keyPtr[0] = '\0';  // Previous iOS version than iOS7 set the first char to '\0' if the key was longer than kCCKeySizeAES256
 }

 NSUInteger dataLength = [self length];

 //See the doc: For block ciphers, the output size will always be less than or
 //equal to the input size plus the size of one block.
 //That's why we need to add the size of one block here
 size_t bufferSize = dataLength + kCCBlockSizeAES128;
 void *buffer = malloc(bufferSize);

 size_t numBytesEncrypted = 0;
 CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                                keyPtr, kCCKeySizeAES256,
                                                NULL /* initialization vector (optional) */,
                                                [self bytes], dataLength, /* input */
                                                buffer, bufferSize, /* output */
                                                &numBytesEncrypted);
 if (cryptStatus == kCCSuccess) {
      //the returned NSData takes ownership of the buffer and will free it on deallocation
      return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
 }

 free(buffer); //free the buffer;
 return nil;
}

Of course, copy paste the same patch for the decrypt method.