Code/Projects/SmartPlugDetector/src/main/java/edu/uci/iotproject/detection/layer2/Layer2ClusterMatcher.java

   1 package edu.uci.iotproject.detection.layer2;
   2
   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.*;
   9
  10 import java.util.ArrayList;
  11 import java.util.HashMap;
  12 import java.util.List;
  13 import java.util.Map;
  14
  15 /**
  16  * Attempts to detect members of a cluster (packet sequence mutations) in layer 2 flows.
  17  *
  18  * @author Janus Varmarken {@literal <jvarmark@uci.edu>}
  19  * @author Rahmadi Trimananda {@literal <rtrimana@uci.edu>}
  20  */
  21 public class Layer2ClusterMatcher extends AbstractClusterMatcher implements Layer2FlowReassemblerObserver, Layer2FlowObserver {
  22
  23     /**
  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.
  27      */
  28     private final Map<Layer2Flow, Layer2SequenceMatcher[][]> mPerFlowSeqMatchers = new HashMap<>();
  29
  30
  31     public Layer2ClusterMatcher(List<List<PcapPacket>> cluster) {
  32         super(cluster);
  33     }
  34
  35     @Override
  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));
  47             }
  48             // Associate the new sequence matcher table with the new flow
  49             mPerFlowSeqMatchers.put(flow, matchers);
  50         }
  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];
  60                 if (sm == null) {
  61                     // There is currently no sequence matcher that has managed to match j packets.
  62                     continue;
  63                 }
  64                 boolean matched = sm.matchPacket(newPacket);
  65                 if (matched) {
  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;
  71                     } else {
  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
  77                         // order here.
  78                         if (matchers[i][j+1] == null ||
  79                                 newPacket.getTimestamp().isAfter(matchers[i][j+1].getLastPacket().getTimestamp())) {
  80                             matchers[i][j+1] = sm;
  81                         }
  82                     }
  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());
  87                     }
  88                 }
  89             }
  90         }
  91     }
  92
  93
  94     @Override
  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()) {
 103                         return false;
 104                     }
 105                 }
 106                 return true;
 107             });
 108             if (!alreadyPresent) {
 109                 // Add the sequence if not already present in the pruned cluster.
 110                 prunedCluster.add(originalClusterSeq);
 111             }
 112         }
 113         return prunedCluster;
 114     }
 115
 116
 117     @Override
 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);
 121     }
 122 }