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     private int mInclusionTimeMillis;
  26
  27     /**
  28      * Create a {@code Layer2SequenceMatcher}.
  29      * @param sequence The sequence to match against (search for).
  30      */
  31     public Layer2SequenceMatcher(List<PcapPacket> sequence, int inclusionTimeMillis) {
  32         super(sequence);
  33         mSequence = sequence;
  34         // Compute packet directions for sequence.
  35         for (int i = 0; i < sequence.size(); i++) {
  36             if (i == 0) {
  37                 // No previous packet; boolean parameter is ignored in this special case.
  38                 mPacketDirections[i] = getPacketDirection(null, true, sequence.get(i));
  39             } else {
  40                 // Base direction marker on direction of previous packet.
  41                 PcapPacket prevPkt = mSequence.get(i-1);
  42                 boolean prevPktDirection = mPacketDirections[i-1];
  43                 mPacketDirections[i] = getPacketDirection(prevPkt, prevPktDirection, sequence.get(i));
  44             }
  45         }
  46         mInclusionTimeMillis =
  47                 inclusionTimeMillis == 0 ? TriggerTrafficExtractor.INCLUSION_WINDOW_MILLIS : inclusionTimeMillis;
  48     }
  49
  50     /**
  51      * Attempt to advance this {@code Layer2SequenceMatcher} by matching {@code packet} against the packet that this
  52      * {@code Layer2SequenceMatcher} expects as the next packet of the sequence it is searching for.
  53      * @param packet
  54      * @return {@code true} if this {@code Layer2SequenceMatcher} could advance by adding {@code packet} to its set of
  55      *         matched packets, {@code false} otherwise.
  56      */
  57     public boolean matchPacket(PcapPacket packet) {
  58         if (getMatchedPacketsCount() == getTargetSequencePacketCount()) {
  59             // We already matched the entire sequence, so we can't match any more packets.
  60             return false;
  61         }
  62
  63         // Verify that new packet pertains to same flow as previously matched packets, if any.
  64         if (getMatchedPacketsCount() > 0) {
  65             MacAddress pktSrc = PcapPacketUtils.getEthSrcAddr(packet);
  66             MacAddress pktDst = PcapPacketUtils.getEthDstAddr(packet);
  67             MacAddress earlierPktSrc = PcapPacketUtils.getEthSrcAddr(mMatchedPackets.get(0));
  68             MacAddress earlierPktDst = PcapPacketUtils.getEthDstAddr(mMatchedPackets.get(0));
  69             if (!(pktSrc.equals(earlierPktSrc) && pktDst.equals(earlierPktDst) ||
  70                     pktSrc.equals(earlierPktDst) && pktDst.equals(earlierPktSrc))) {
  71                 return false;
  72             }
  73         }
  74
  75         // Get representative of the packet we expect to match next.
  76         PcapPacket expected = mSequence.get(mMatchedPackets.size());
  77         // First verify if the received packet has the length we're looking for.
  78         if (packet.getOriginalLength() == expected.getOriginalLength()) {
  79             // If this is the first packet, we only need to verify that its length is correct. Time constraints are
  80             // obviously satisfied as there are no previous packets. Furthermore, direction matches by definition as we
  81             // don't know the MAC of the device (or phone) in advance, so we can't enforce a rule saying "first packet
  82             // must originate from this particular MAC".
  83             if (getMatchedPacketsCount() == 0) {
  84                 // Store packet as matched and advance.
  85                 mMatchedPackets.add(packet);
  86                 return true;
  87             }
  88             // Check if direction of packet matches expected direction.
  89             boolean actualDirection = getPacketDirection(mMatchedPackets.get(getMatchedPacketsCount()-1),
  90                     mPacketDirections[getMatchedPacketsCount()-1], packet);
  91             boolean expectedDirection = mPacketDirections[getMatchedPacketsCount()];
  92             if (actualDirection != expectedDirection) {
  93                 return false;
  94             }
  95             // Next apply timing constraints:
  96             // 1: to be a match, the packet must have a later timestamp than any other packet currently matched
  97             // 2: does adding the packet cause the max allowed time between first packet and last packet to be exceeded?
  98             if (!packet.getTimestamp().isAfter(mMatchedPackets.get(getMatchedPacketsCount()-1).getTimestamp())) {
  99                 return false;
 100             }
 101 //            if (packet.getTimestamp().isAfter(mMatchedPackets.get(0).getTimestamp().
 102 //                            plusMillis(TriggerTrafficExtractor.INCLUSION_WINDOW_MILLIS))) {
 103             if (packet.getTimestamp().isAfter(mMatchedPackets.get(0).getTimestamp().
 104                 plusMillis(mInclusionTimeMillis))) {
 105                 return false;
 106             }
 107             // If we made it here, it means that this packet has the expected length, direction, and obeys the timing
 108             // constraints, so we store it and advance.
 109             mMatchedPackets.add(packet);
 110             if (mMatchedPackets.size() == mSequence.size()) {
 111                 // TODO report (to observers?) that we are done?
 112             }
 113             return true;
 114         }
 115         return false;
 116     }
 117
 118     public int getTargetSequencePacketCount() {
 119         return mSequence.size();
 120     }
 121
 122     public List<PcapPacket> getTargetSequence() {
 123         return mSequence;
 124     }
 125
 126 }