/*

 Password Encryptor

 Copyright 2013 Thincast Technologies GmbH, Author: Dorian Johnson

 This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. 

 If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

 */

/* We try to use CommonCrypto as much as possible. PBKDF2 was added to CommonCrypto in iOS 5, so use OpenSSL only as a fallback to do PBKDF2 on pre iOS 5 systems. */

#import "Encryptor.h"

#import <CommonCrypto/CommonKeyDerivation.h> 

#import <CommonCrypto/CommonCryptor.h> 

#import <CommonCrypto/CommonDigest.h> 

#import <openssl/evp.h> // For PBKDF2 on < 5.0

#include <fcntl.h>

#pragma mark -

@interface Encryptor (Private)

- (NSData*)randomInitializationVector;

@end

@implementation Encryptor

@synthesize plaintextPassword=_plaintext_password;

- (id)initWithPassword:(NSString*)plaintext_password

{

	if (plaintext_password == nil)

		return nil; 

	if ( !(self = [super init]) )

		return nil;

	_plaintext_password = [plaintext_password retain];

	const char* plaintext_password_data = [plaintext_password length] ? [plaintext_password UTF8String] : " ";

	if (!plaintext_password_data || !strlen(plaintext_password_data))

		[NSException raise:NSInternalInconsistencyException format:@"%s: plaintext password data is zero length!", __func__];

	uint8_t* derived_key = calloc(1, TSXEncryptorPBKDF2KeySize);

	if (CCKeyDerivationPBKDF != NULL)

	{

		int ret = CCKeyDerivationPBKDF(kCCPBKDF2, plaintext_password_data, strlen(plaintext_password_data)-1, (const uint8_t*)TSXEncryptorPBKDF2Salt, TSXEncryptorPBKDF2SaltLen, kCCPRFHmacAlgSHA1, TSXEncryptorPBKDF2Rounds, derived_key, TSXEncryptorPBKDF2KeySize);

		//NSLog(@"CCKeyDerivationPBKDF ret = %d; key: %@", ret, [NSData dataWithBytesNoCopy:derived_key length:TWEncryptorPBKDF2KeySize freeWhenDone:NO]);

		if (ret)

		{

			NSLog(@"%s: CCKeyDerivationPBKDF ret == %d, indicating some sort of failure.", __func__, ret);

            free(derived_key);

			[self autorelease];

			return nil;

		}

	}

	else

	{

		// iOS 4.x or earlier -- use OpenSSL

		unsigned long ret = PKCS5_PBKDF2_HMAC_SHA1(plaintext_password_data, (int)strlen(plaintext_password_data)-1, (const unsigned char*)TSXEncryptorPBKDF2Salt, TSXEncryptorPBKDF2SaltLen, TSXEncryptorPBKDF2Rounds, TSXEncryptorPBKDF2KeySize, derived_key);

		//NSLog(@"PKCS5_PBKDF2_HMAC_SHA1 ret = %lu; key: %@", ret, [NSData dataWithBytesNoCopy:derived_key length:TWEncryptorPBKDF2KeySize freeWhenDone:NO]);

		if (ret != 1)

		{

			NSLog(@"%s: PKCS5_PBKDF2_HMAC_SHA1 ret == %lu, indicating some sort of failure.", __func__, ret);

            free(derived_key);

			[self release];

			return nil;

		}

	}	

	_encryption_key = [[NSData alloc] initWithBytesNoCopy:derived_key length:TSXEncryptorPBKDF2KeySize freeWhenDone:YES];

	return self;

}

#pragma mark -

#pragma mark Encrypting/Decrypting data

- (NSData*)encryptData:(NSData*)plaintext_data

{

	if (![plaintext_data length])

		return nil;

	NSData* iv = [self randomInitializationVector];

	NSMutableData* encrypted_data = [NSMutableData dataWithLength:[iv length] + [plaintext_data length] + TSXEncryptorBlockCipherBlockSize];

	[encrypted_data replaceBytesInRange:NSMakeRange(0, [iv length]) withBytes:[iv bytes]];

	size_t data_out_moved = 0;

	int ret = CCCrypt(kCCEncrypt, TSXEncryptorBlockCipherAlgo, TSXEncryptorBlockCipherOptions, [_encryption_key bytes], TSXEncryptorBlockCipherKeySize, [iv bytes], [plaintext_data bytes], [plaintext_data length], [encrypted_data mutableBytes]+[iv length], [encrypted_data length]-[iv length], &data_out_moved);

	switch (ret)

	{

		case kCCSuccess:

			[encrypted_data setLength:[iv length] + data_out_moved];

			return encrypted_data;

		default:

			NSLog(@"%s: uncaught error, ret CCCryptorStatus = %d (plaintext len = %lu; buffer size = %lu)", __func__, ret, (unsigned long)[plaintext_data length], (unsigned long)([encrypted_data length]-[iv length]));

			return nil;

	}

	return nil;

}

- (NSData*)decryptData:(NSData*)encrypted_data

{

	if ([encrypted_data length] <= TSXEncryptorBlockCipherBlockSize)

		return nil;

	NSMutableData* plaintext_data = [NSMutableData dataWithLength:[encrypted_data length] + TSXEncryptorBlockCipherBlockSize];

	size_t data_out_moved = 0;

	int ret = CCCrypt(kCCDecrypt, TSXEncryptorBlockCipherAlgo, TSXEncryptorBlockCipherOptions, [_encryption_key bytes], TSXEncryptorBlockCipherKeySize, [encrypted_data bytes], [encrypted_data bytes] + TSXEncryptorBlockCipherBlockSize, [encrypted_data length] - TSXEncryptorBlockCipherBlockSize, [plaintext_data mutableBytes], [plaintext_data length], &data_out_moved);

	switch (ret)

	{

		case kCCSuccess:

			[plaintext_data setLength:data_out_moved];

			return plaintext_data;

		case kCCBufferTooSmall: // Our output buffer is big enough to decrypt valid data. This return code indicates malformed data.

		case kCCAlignmentError: // Shouldn't get this, since we're using padding.

		case kCCDecodeError:	// Wrong key.

			return nil;

		default:

			NSLog(@"%s: uncaught error, ret CCCryptorStatus = %d (encrypted data len = %lu; buffer size = %lu; dom = %lu)", __func__, ret, (unsigned long)[encrypted_data length], (unsigned long)[plaintext_data length], data_out_moved);

			return nil;

	}

	return nil;

}

- (NSData*)encryptString:(NSString*)plaintext_string

{

	return [self encryptData:[plaintext_string dataUsingEncoding:NSUTF8StringEncoding]];

}

- (NSString*)decryptString:(NSData*)encrypted_string

{

	return [[[NSString alloc] initWithData:[self decryptData:encrypted_string] encoding:NSUTF8StringEncoding] autorelease];

}

- (NSData*)randomInitializationVector

{

	NSMutableData* iv = [NSMutableData dataWithLength:TSXEncryptorBlockCipherBlockSize];

	int fd;

	if ( (fd = open("/dev/urandom", O_RDONLY)) < 0)

		return nil;

	NSInteger bytes_needed = [iv length];

	char* p = [iv mutableBytes];

	while (bytes_needed)

	{

		long bytes_read = read(fd, p, bytes_needed);

		if (bytes_read < 0)

			continue;

		p += bytes_read;

		bytes_needed -= bytes_read;

	}

	close(fd);

	return iv;

}

@end