/* |
File: QCCAESPadCryptor.m |
Abstract: Implements AES encryption and decryption with PKCS#7 padding. |
Version: 1.0 |
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*/ |
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#import "QCCAESPadCryptor.h" |
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#include <CommonCrypto/CommonCrypto.h> |
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@interface QCCAESPadCryptor () |
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@property (atomic, assign, readonly ) CCOperation op; |
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// read/write versions of public properties |
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@property (atomic, copy, readwrite) NSError * error; |
@property (atomic, copy, readwrite) NSData * outputData; |
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@end |
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@implementation QCCAESPadCryptor |
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- (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; |
} |
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- (id)initToEncryptInputData:(NSData *)inputData keyData:(NSData *)keyData |
{ |
return [self initWithOp:kCCEncrypt inputData:inputData keyData:keyData]; |
} |
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- (id)initToDecryptInputData:(NSData *)inputData keyData:(NSData *)keyData |
{ |
return [self initWithOp:kCCDecrypt inputData:inputData keyData:keyData]; |
} |
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- (void)main |
{ |
CCCryptorStatus err; |
NSUInteger keyDataLength; |
NSMutableData * result; |
size_t resultLength; |
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// 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). |
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err = kCCSuccess; |
if ( (self.op == kCCDecrypt) && (([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; |
} |
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if (err == kCCSuccess) { |
NSUInteger padLength; |
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// Padding can expand the data, so we have to allocate space for that. The rule for block |
// cyphers, like AES, is that the padding only adds space on encryption (on decryption it |
// can reduce space, obviously, but we don't need to account for that) and it will only add |
// at most one block size worth of space. |
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if (self.op == kCCEncrypt) { |
padLength = kCCBlockSizeAES128; |
} else { |
padLength = 0; |
} |
result = [[NSMutableData alloc] initWithLength:[self.inputData length] + padLength]; |
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err = CCCrypt( |
self.op, |
kCCAlgorithmAES128, |
((self.ivData == nil) ? kCCOptionECBMode : 0) | kCCOptionPKCS7Padding, |
[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) { |
// Set the output length to the value returned by CCCrypt. This is necessary because |
// we have padding enabled, meaning that we might have allocated more space than we needed |
// (in the encrypt case, this is the space we allocated above for padding; in the decrypt |
// case, the output is actually shorter than the input because the padding is removed). |
[result setLength:resultLength]; |
self.outputData = result; |
} else { |
self.error = [NSError errorWithDomain:kQCCAESPadCryptorErrorDomain code:err userInfo:nil]; |
} |
} |
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@end |
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NSString * kQCCAESPadCryptorErrorDomain = @"kQCCAESPadCryptorErrorDomain"; |
