Code/Projects/PacketLevelSignatureExtractor/src/main/java/edu/uci/iotproject/detection/layer2/Layer2SequenceMatcher.java

   1 package edu.uci.iotproject.detection.layer2;
   2
   3 import edu.uci.iotproject.analysis.TriggerTrafficExtractor;
   4 import edu.uci.iotproject.util.PcapPacketUtils;
   5 import org.pcap4j.core.PcapPacket;
   6 import org.pcap4j.util.MacAddress;
   7
   8 import java.util.ArrayList;
   9 import java.util.List;
  10
  11 /**
  12  * Attempts to detect the presence of a specific packet sequence in the set of packets provided through multiple calls
  13  * to {@link #matchPacket(PcapPacket)}, considering only layer 2 information.
  14  *
  15  * @author Janus Varmarken {@literal <jvarmark@uci.edu>}
  16  * @author Rahmadi Trimananda {@literal <rtrimana@uci.edu>}
  17  */
  18 public class Layer2SequenceMatcher extends Layer2AbstractMatcher {
  19
  20     /**
  21      * The sequence this {@link Layer2SequenceMatcher} is searching for.
  22      */
  23     private final List<PcapPacket> mSequence;
  24
  25     /**
  26      * Create a {@code Layer2SequenceMatcher}.
  27      * @param sequence The sequence to match against (search for).
  28      */
  29     public Layer2SequenceMatcher(List<PcapPacket> sequence) {
  30         super(sequence);
  31         mSequence = sequence;
  32         // Compute packet directions for sequence.
  33         for (int i = 0; i < sequence.size(); i++) {
  34             if (i == 0) {
  35                 // No previous packet; boolean parameter is ignored in this special case.
  36                 mPacketDirections[i] = getPacketDirection(null, true, sequence.get(i));
  37             } else {
  38                 // Base direction marker on direction of previous packet.
  39                 PcapPacket prevPkt = mSequence.get(i-1);
  40                 boolean prevPktDirection = mPacketDirections[i-1];
  41                 mPacketDirections[i] = getPacketDirection(prevPkt, prevPktDirection, sequence.get(i));
  42             }
  43         }
  44     }
  45
  46     /**
  47      * Attempt to advance this {@code Layer2SequenceMatcher} by matching {@code packet} against the packet that this
  48      * {@code Layer2SequenceMatcher} expects as the next packet of the sequence it is searching for.
  49      * @param packet
  50      * @return {@code true} if this {@code Layer2SequenceMatcher} could advance by adding {@code packet} to its set of
  51      *         matched packets, {@code false} otherwise.
  52      */
  53     public boolean matchPacket(PcapPacket packet) {
  54         if (getMatchedPacketsCount() == getTargetSequencePacketCount()) {
  55             // We already matched the entire sequence, so we can't match any more packets.
  56             return false;
  57         }
  58
  59         // Verify that new packet pertains to same flow as previously matched packets, if any.
  60         if (getMatchedPacketsCount() > 0) {
  61             MacAddress pktSrc = PcapPacketUtils.getEthSrcAddr(packet);
  62             MacAddress pktDst = PcapPacketUtils.getEthDstAddr(packet);
  63             MacAddress earlierPktSrc = PcapPacketUtils.getEthSrcAddr(mMatchedPackets.get(0));
  64             MacAddress earlierPktDst = PcapPacketUtils.getEthDstAddr(mMatchedPackets.get(0));
  65             if (!(pktSrc.equals(earlierPktSrc) && pktDst.equals(earlierPktDst) ||
  66                     pktSrc.equals(earlierPktDst) && pktDst.equals(earlierPktSrc))) {
  67                 return false;
  68             }
  69         }
  70
  71         // Get representative of the packet we expect to match next.
  72         PcapPacket expected = mSequence.get(mMatchedPackets.size());
  73         // First verify if the received packet has the length we're looking for.
  74         if (packet.getOriginalLength() == expected.getOriginalLength()) {
  75             // If this is the first packet, we only need to verify that its length is correct. Time constraints are
  76             // obviously satisfied as there are no previous packets. Furthermore, direction matches by definition as we
  77             // don't know the MAC of the device (or phone) in advance, so we can't enforce a rule saying "first packet
  78             // must originate from this particular MAC".
  79             if (getMatchedPacketsCount() == 0) {
  80                 // Store packet as matched and advance.
  81                 mMatchedPackets.add(packet);
  82                 return true;
  83             }
  84             // Check if direction of packet matches expected direction.
  85             boolean actualDirection = getPacketDirection(mMatchedPackets.get(getMatchedPacketsCount()-1),
  86                     mPacketDirections[getMatchedPacketsCount()-1], packet);
  87             boolean expectedDirection = mPacketDirections[getMatchedPacketsCount()];
  88             if (actualDirection != expectedDirection) {
  89                 return false;
  90             }
  91             // Next apply timing constraints:
  92             // 1: to be a match, the packet must have a later timestamp than any other packet currently matched
  93             // 2: does adding the packet cause the max allowed time between first packet and last packet to be exceeded?
  94             if (!packet.getTimestamp().isAfter(mMatchedPackets.get(getMatchedPacketsCount()-1).getTimestamp())) {
  95                 return false;
  96             }
  97             if (packet.getTimestamp().isAfter(mMatchedPackets.get(0).getTimestamp().
  98                             plusMillis(TriggerTrafficExtractor.INCLUSION_WINDOW_MILLIS))) {
  99                 return false;
 100             }
 101             // If we made it here, it means that this packet has the expected length, direction, and obeys the timing
 102             // constraints, so we store it and advance.
 103             mMatchedPackets.add(packet);
 104             if (mMatchedPackets.size() == mSequence.size()) {
 105                 // TODO report (to observers?) that we are done?
 106             }
 107             return true;
 108         }
 109         return false;
 110     }
 111
 112     public int getTargetSequencePacketCount() {
 113         return mSequence.size();
 114     }
 115
 116     public List<PcapPacket> getTargetSequence() {
 117         return mSequence;
 118     }
 119
 120 }