1 package edu.uci.iotproject.detection.layer2;
3 import edu.uci.iotproject.trafficreassembly.layer2.Layer2FlowReassembler;
4 import edu.uci.iotproject.trafficreassembly.layer2.Layer2Flow;
5 import edu.uci.iotproject.trafficreassembly.layer2.Layer2FlowReassemblerObserver;
6 import edu.uci.iotproject.detection.AbstractClusterMatcher;
7 import edu.uci.iotproject.trafficreassembly.layer2.Layer2FlowObserver;
8 import org.pcap4j.core.*;
10 import java.util.ArrayList;
11 import java.util.HashMap;
12 import java.util.List;
16 * Attempts to detect members of a cluster (packet sequence mutations) in layer 2 flows.
18 * @author Janus Varmarken {@literal <jvarmark@uci.edu>}
19 * @author Rahmadi Trimananda {@literal <rtrimana@uci.edu>}
21 public class Layer2ClusterMatcher extends AbstractClusterMatcher implements Layer2FlowReassemblerObserver, Layer2FlowObserver {
24 * Maps from a flow to a table of {@link Layer2SequenceMatcher}s for that particular flow. The table {@code t} is
25 * structured such that {@code t[i][j]} is a {@link Layer2SequenceMatcher} that attempts to match member {@code i}
26 * of {@link #mCluster} and has so far matched {@code j} packets of that particular sequence.
28 private final Map<Layer2Flow, Layer2SequenceMatcher[][]> mPerFlowSeqMatchers = new HashMap<>();
31 public Layer2ClusterMatcher(List<List<PcapPacket>> cluster) {
36 public void onNewPacket(Layer2Flow flow, PcapPacket newPacket) {
37 if (mPerFlowSeqMatchers.get(flow) == null) {
38 // If this is the first time we encounter this flow, we need to set up sequence matchers for it.
39 // All sequences of the cluster have the same length, so we only need to compute the length of the nested
40 // arrays once. We want to make room for a cluster matcher in each state, including the initial empty state
41 // but excluding the final "full match" state (as there is no point in keeping a terminated sequence matcher
42 // around), so the length of the inner array is simply the sequence length.
43 Layer2SequenceMatcher[][] matchers = new Layer2SequenceMatcher[mCluster.size()][mCluster.get(0).size()];
44 // Prepare a "state 0" sequence matcher for each sequence variation in the cluster.
45 for (int i = 0; i < matchers.length; i++) {
46 matchers[i][0] = new Layer2SequenceMatcher(mCluster.get(i));
48 // Associate the new sequence matcher table with the new flow
49 mPerFlowSeqMatchers.put(flow, matchers);
51 // Fetch table that contains sequence matchers for this flow.
52 Layer2SequenceMatcher[][] matchers = mPerFlowSeqMatchers.get(flow);
53 // Present the packet to all sequence matchers.
54 for (int i = 0; i < matchers.length; i++) {
55 // Present packet to the sequence matchers that has advanced the most first. This is to prevent discarding
56 // the sequence matchers that have advanced the most in the special case where the searched sequence
57 // contains two packets of the same length going in the same direction.
58 for (int j = matchers[i].length - 1; j >= 0 ; j--) {
59 Layer2SequenceMatcher sm = matchers[i][j];
61 // There is currently no sequence matcher that has managed to match j packets.
64 boolean matched = sm.matchPacket(newPacket);
66 if (sm.getMatchedPacketsCount() == sm.getTargetSequencePacketCount()) {
67 // Sequence matcher has a match. Report it to observers.
68 mObservers.forEach(o -> o.onMatch(this, sm.getMatchedPackets()));
69 // Remove the now terminated sequence matcher.
70 matchers[i][j] = null;
72 // Sequence matcher advanced one step, so move it to its corresponding new position iff the
73 // packet that advanced it has a later timestamp than that of the last matched packet of the
74 // sequence matcher at the new index, if any. In most traces, a small amount of the packets
75 // appear out of order (with regards to their timestamp), which is why this check is required.
76 // Obviously it would not be needed if packets where guaranteed to be processed in timestamp
78 if (matchers[i][j+1] == null ||
79 newPacket.getTimestamp().isAfter(matchers[i][j+1].getLastPacket().getTimestamp())) {
80 matchers[i][j+1] = sm;
83 // We always want to have a sequence matcher in state 0, regardless of if the one that advanced
84 // from state zero completed its matching or if it replaced a different one in state 1 or not.
85 if (sm.getMatchedPacketsCount() == 1) {
86 matchers[i][j] = new Layer2SequenceMatcher(sm.getTargetSequence());
95 protected List<List<PcapPacket>> pruneCluster(List<List<PcapPacket>> cluster) {
96 // Note: we assume that all sequences in the input cluster are of the same length and that their packet
97 // directions are identical.
98 List<List<PcapPacket>> prunedCluster = new ArrayList<>();
99 for (List<PcapPacket> originalClusterSeq : cluster) {
100 boolean alreadyPresent = prunedCluster.stream().anyMatch(pcPkts -> {
101 for (int i = 0; i < pcPkts.size(); i++) {
102 if (pcPkts.get(i).getOriginalLength() != originalClusterSeq.get(i).getOriginalLength()) {
108 if (!alreadyPresent) {
109 // Add the sequence if not already present in the pruned cluster.
110 prunedCluster.add(originalClusterSeq);
113 return prunedCluster;
118 public void onNewFlow(Layer2FlowReassembler reassembler, Layer2Flow newFlow) {
119 // Subscribe to the new flow to get updates whenever a new packet pertaining to the flow is processed.
120 newFlow.addFlowObserver(this);