/*

     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";