Operations/QCCAESCryptor.m

/*
     File: QCCAESCryptor.m
 Abstract: Implements AES encryption and decryption without padding.
  Version: 1.0
 
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 */
 
#import "QCCAESCryptor.h"
 
#include <CommonCrypto/CommonCrypto.h>
 
@interface QCCAESCryptor ()
 
@property (atomic, assign, readonly ) CCOperation   op;
 
// read/write versions of public properties
 
@property (atomic, copy,   readwrite) NSError *     error;
@property (atomic, copy,   readwrite) NSData *      outputData;
 
@end
 
@implementation QCCAESCryptor
 
- (id)initWithOp:(CCOperation)op inputData:(NSData *)inputData keyData:(NSData *)keyData
{
    NSParameterAssert(inputData != nil);
    NSParameterAssert(keyData != nil);
    self = [super init];
    if (self != nil) {
        self->_op = op;
        self->_inputData = [inputData copy];
        self->_keyData = [keyData copy];
        self->_ivData = [[NSMutableData alloc] initWithLength:kCCBlockSizeAES128];
    }
    return self;
}
 
- (id)initToEncryptInputData:(NSData *)inputData keyData:(NSData *)keyData
{
    return [self initWithOp:kCCEncrypt inputData:inputData keyData:keyData];
}
 
- (id)initToDecryptInputData:(NSData *)inputData keyData:(NSData *)keyData
{
    return [self initWithOp:kCCDecrypt inputData:inputData keyData:keyData];
}
 
- (void)main
{
    CCCryptorStatus     err;
    NSUInteger          keyDataLength;
    NSMutableData *     result;
    size_t              resultLength;
    
    // We check for common input problems to make it easier for someone tracing through 
    // the code to find problems (rather than just getting a mysterious kCCParamError back 
    // from CCCrypt).
    
    err = kCCSuccess;
    if (([self.inputData length] % kCCBlockSizeAES128) != 0) {
        err = kCCParamError;
    }
    keyDataLength = [self.keyData length];
    if ( (keyDataLength != kCCKeySizeAES128) && (keyDataLength != kCCKeySizeAES192) && (keyDataLength != kCCKeySizeAES256) ) {
        err = kCCParamError;
    }
    if ( (self.ivData != nil) && ([self.ivData length] != kCCBlockSizeAES128) ) {
        err = kCCParamError;
    }
    
    if (err == kCCSuccess) {
        result = [[NSMutableData alloc] initWithLength:[self.inputData length]];
 
        err = CCCrypt(
            self.op, 
            kCCAlgorithmAES128, 
            (self.ivData == nil) ? kCCOptionECBMode : 0, 
            [self.keyData bytes],   [self.keyData length], 
            [self.ivData bytes],                                // will be NULL if ivData is nil
            [self.inputData bytes], [self.inputData length], 
            [result mutableBytes],  [result length], 
            &resultLength
        );
    }
    if (err == kCCSuccess) {
        // In the absence of padding the data out is always the same size as the data in.
        assert(resultLength == [result length]);
        self.outputData = result;
    } else {
        self.error = [NSError errorWithDomain:kQCCAESCryptorErrorDomain code:err userInfo:nil];
    }
}
 
@end
 
NSString * kQCCAESCryptorErrorDomain = @"kQCCAESCryptorErrorDomain";