Salsa20RandomStream.m

//
//  Salsa20RandomStream.m
//  KeePass2
//
//  Created by Qiang Yu on 2/28/10.
//  Copyright 2010 Qiang Yu. All rights reserved.
//

#import <CommonCrypto/CommonDigest.h>
#import "Salsa20RandomStream.h"
#import "ByteBuffer.h"

static uint32_t SIGMA[4] = {0x61707865, 0x3320646E, 0x79622D32, 0x6B206574};

@interface Salsa20RandomStream (PrivateMethods)
-(void)setKey:(uint8_t *)key;
-(void)setIV:(uint8_t *)iv;
-(uint32_t)uint8To32Little:(uint8_t *)buffer offset:(uint32_t)offset;
-(uint32_t)rotl:(uint32_t)x y:(uint32_t)y;
-(void)updateState;
@end


@implementation Salsa20RandomStream
//@synthesize _source;

//-(id)init:(uint8_t *)key len:(uint32_t)len input:(id<InputDataSource>)source{
-(id)init:(uint8_t *)key len:(uint32_t)len{
	if(self=[super init]){
		uint8_t key32[32];
		CC_SHA256(key, len, key32);
		uint8_t iv[] = {0xE8, 0x30, 0x09, 0x4B, 0x97, 0x20, 0x5D, 0x2A};
		[self setKey:key32];
		[self setIV:iv];
		_index = 0;
		
		//self._source = source;
	}
	return self;
}

-(void)dealloc{
	//[_source release];
	[super dealloc];
}

-(uint)uint8To32Little:(uint8_t *)buffer offset:(uint32_t)offset{
	return ((uint)buffer[offset] | ((uint)buffer[offset + 1] << 8) |
			((uint)buffer[offset + 2] << 16) | ((uint)buffer[offset + 3] << 24));
}

-(uint32_t)rotl:(uint32_t)x y:(uint32_t)y{
	return (x<<y)|(x>>(32-y));
}

-(void)setKey:(uint8_t *)key{
	_state[1] = [self uint8To32Little:key offset:0];
	_state[2] = [self uint8To32Little:key offset:4];
	_state[3] = [self uint8To32Little:key offset:8];
	_state[4] = [self uint8To32Little:key offset:12];
	
	_state[11] = [self uint8To32Little:key offset:16];
	_state[12] = [self uint8To32Little:key offset:20];
	_state[13] = [self uint8To32Little:key offset:24];
	_state[14] = [self uint8To32Little:key offset:28];
	_state[0 ] = SIGMA[0];
	_state[5 ] = SIGMA[1];
	_state[10] = SIGMA[2];
	_state[15] = SIGMA[3];
}

-(void)setIV:(uint8_t *)iv{	
	_state[6] = [self uint8To32Little:iv offset:0];
	_state[7] = [self uint8To32Little:iv offset:4];
	_state[8] = 0;
	_state[9] = 0;
}

-(void)updateState{
	uint32_t x[16];
	
	for(int i=0; i<16; i++) x[i] = _state[i];
	
	for(int i=0; i<10; i++){
		x[ 4] ^= [self rotl:(x[ 0]+x[12]) y:7];
		x[ 8] ^= [self rotl:(x[ 4]+x[ 0]) y:9];
		x[12] ^= [self rotl:(x[ 8]+x[ 4]) y:13];
		x[ 0] ^= [self rotl:(x[12]+x[ 8]) y:18];
		x[ 9] ^= [self rotl:(x[ 5]+x[ 1]) y:7];
		x[13] ^= [self rotl:(x[ 9]+x[ 5]) y:9];
		x[ 1] ^= [self rotl:(x[13]+x[ 9]) y:13];
		x[ 5] ^= [self rotl:(x[ 1]+x[13]) y:18];
		x[14] ^= [self rotl:(x[10]+x[ 6]) y:7];
		x[ 2] ^= [self rotl:(x[14]+x[10]) y:9];
		x[ 6] ^= [self rotl:(x[ 2]+x[14]) y:13];
		x[10] ^= [self rotl:(x[ 6]+x[ 2]) y:18];
		x[ 3] ^= [self rotl:(x[15]+x[11]) y:7];
		x[ 7] ^= [self rotl:(x[ 3]+x[15]) y:9];
		x[11] ^= [self rotl:(x[ 7]+x[ 3]) y:13];
		x[15] ^= [self rotl:(x[11]+x[ 7]) y:18];
		x[ 1] ^= [self rotl:(x[ 0]+x[ 3]) y:7];
		x[ 2] ^= [self rotl:(x[ 1]+x[ 0]) y:9];
		x[ 3] ^= [self rotl:(x[ 2]+x[ 1]) y:13];
		x[ 0] ^= [self rotl:(x[ 3]+x[ 2]) y:18];
		x[ 6] ^= [self rotl:(x[ 5]+x[ 4]) y:7];
		x[ 7] ^= [self rotl:(x[ 6]+x[ 5]) y:9];
		x[ 4] ^= [self rotl:(x[ 7]+x[ 6]) y:13];
		x[ 5] ^= [self rotl:(x[ 4]+x[ 7]) y:18];
		x[11] ^= [self rotl:(x[10]+x[ 9]) y:7];
		x[ 8] ^= [self rotl:(x[11]+x[10]) y:9];
		x[ 9] ^= [self rotl:(x[ 8]+x[11]) y:13];
		x[10] ^= [self rotl:(x[ 9]+x[ 8]) y:18];
		x[12] ^= [self rotl:(x[15]+x[14]) y:7];
		x[13] ^= [self rotl:(x[12]+x[15]) y:9];
		x[14] ^= [self rotl:(x[13]+x[12]) y:13];
		x[15] ^= [self rotl:(x[14]+x[13]) y:18];		
	}
	
	for (int i=0; i<16; i++)
		x[i] += _state[i];
	
	for (int i = 0, j = 0; i<16; i++,j+=4){
		uint32_t t = x[i];
		_keyStream[j+0] = (uint8_t)t;
		_keyStream[j+1] = (uint8_t)(t >> 8);
		_keyStream[j+2] = (uint8_t)(t >> 16);
		_keyStream[j+3] = (uint8_t)(t >> 24);		
	}
	
	_state[8]++; 
	if(!_state[8]) _state[9]++;
}

-(NSString *)xor:(NSData *)data{	
	ByteBuffer * bb = [[ByteBuffer alloc]initWithSize:[data length]];	
	[data getBytes:bb._bytes length:bb._size];
	
	for(int i=0; i<bb._size; i++){
		if(_index==0) [self updateState];
		(bb._bytes)[i] ^= _keyStream[_index];
		//DLog(@"====>%d=====%d", bb._bytes[i], _keyStream[_index]);
		_index = (_index+1)&0x3F;
	}
	
	NSString * rv = [[NSString alloc]initWithBytes:bb._bytes length:bb._size encoding:NSUTF8StringEncoding];
	[bb release];
	return [rv autorelease];	
}


/*
 * remove the support of InputdataSource to make the class less confusing
 *
 
-(NSUInteger)readBytes:(void *)buffer length:(NSUInteger)length{
	NSUInteger read = [_source readBytes:buffer length:length];
	for(int i=0; i<read; i++){
		if(_index==0) [self updateState];
		((uint8_t *)buffer)[i] ^= _keyStream[_index];
		_index = (_index+1)&0x3F;
	}	
	return read;
}

-(NSUInteger)lengthOfRemainingReadbleBytes{
	@throw [NSException exceptionWithName:@"UnsupportedMethod" reason:@"lengthOfRemainingReadbleBytes" userInfo:nil];
}

-(NSUInteger)setReadOffset:(NSUInteger) offset{
	@throw [NSException exceptionWithName:@"UnsupportedMethod" reason:@"setReadOffset" userInfo:nil];
}

-(NSUInteger)moveReadOffset:(NSInteger) offset{
	@throw [NSException exceptionWithName:@"UnsupportedMethod" reason:@"moveReadOffset" userInfo:nil];
}
*/

@end