78 lines
1.9 KiB
Mathematica
78 lines
1.9 KiB
Mathematica
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// ReplayProtector.m
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// PIATunnel
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//
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// Created by Davide De Rosa on 2/17/17.
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// Copyright © 2018 London Trust Media. All rights reserved.
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//
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#import "ReplayProtector.h"
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#import "Allocation.h"
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#define HIDDEN_WINSIZE 128
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#define BITMAP_LEN (HIDDEN_WINSIZE / 32)
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#define BITMAP_INDEX_MASK (BITMAP_LEN - 1)
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#define REDUNDANT_BIT_SHIFTS 5
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#define REDUNDANT_BITS (1 << REDUNDANT_BIT_SHIFTS)
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#define BITMAP_LOC_MASK (REDUNDANT_BITS - 1)
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#define REPLAY_WINSIZE (HIDDEN_WINSIZE - REDUNDANT_BITS)
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@interface ReplayProtector ()
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@property (nonatomic, assign) uint32_t highestPacketId;
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@property (nonatomic, unsafe_unretained) uint32_t *bitmap;
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@end
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@implementation ReplayProtector
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- (instancetype)init
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{
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if ((self = [super init])) {
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self.highestPacketId = 0;
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self.bitmap = allocate_safely(BITMAP_LEN * sizeof(uint32_t));
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bzero(self.bitmap, BITMAP_LEN * sizeof(uint32_t));
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}
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return self;
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}
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- (void)dealloc
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{
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free(self.bitmap);
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}
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- (BOOL)isReplayedPacketId:(uint32_t)packetId
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{
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if (packetId == 0) {
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return YES;
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}
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if ((REPLAY_WINSIZE + packetId) < self.highestPacketId) {
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return YES;
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}
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uint32_t index = (packetId >> REDUNDANT_BIT_SHIFTS);
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if (packetId > self.highestPacketId) {
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const uint32_t currentIndex = self.highestPacketId >> REDUNDANT_BIT_SHIFTS;
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const uint32_t diff = MIN(index - currentIndex, BITMAP_LEN);
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for (uint32_t bid = 0; bid < diff; ++bid) {
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self.bitmap[(bid + currentIndex + 1) & BITMAP_INDEX_MASK] = 0;
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}
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self.highestPacketId = packetId;
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}
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index &= BITMAP_INDEX_MASK;
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const uint32_t bitLocation = packetId & BITMAP_LOC_MASK;
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const uint32_t bitmask = (1 << bitLocation);
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if (self.bitmap[index] & bitmask) {
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return YES;
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}
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self.bitmap[index] |= bitmask;
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return NO;
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}
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@end
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