+++ /dev/null
-package edu.uci.iotproject.detection.layer2;
-
-import edu.uci.iotproject.analysis.TriggerTrafficExtractor;
-import edu.uci.iotproject.util.PcapPacketUtils;
-import org.pcap4j.core.PcapPacket;
-import org.pcap4j.util.MacAddress;
-
-import java.util.ArrayList;
-import java.util.List;
-
-/**
- * Attempts to detect the presence of a specific packet sequence in the set of packets provided through multiple calls
- * to {@link #matchPacket(PcapPacket)}, considering only layer 2 information.
- *
- * @author Janus Varmarken {@literal <jvarmark@uci.edu>}
- * @author Rahmadi Trimananda {@literal <rtrimana@uci.edu>}
- */
-public class Layer2SequenceMatcher {
-
- /**
- * The sequence this {@link Layer2SequenceMatcher} is searching for.
- */
- private final List<PcapPacket> mSequence;
-
- /**
- * Buffer of actual packets seen so far that match the searched sequence (i.e., constitutes a subsequence of the
- * searched sequence).
- */
- private final List<PcapPacket> mMatchedPackets = new ArrayList<>();
-
- /**
- * Models the directions of packets in {@link #mSequence}. As the sequence matcher assumes that it is only presented
- * with packet from a single flow (packets exchanged between two devices), we can model the packet directions with a
- * single bit. We don't have any notion "phone to device" or "device to phone" as we don't know the MAC addresses
- * of devices in advance during matching.
- */
- private final boolean[] mPacketDirections;
-
- /**
- * Create a {@code Layer2SequenceMatcher}.
- * @param sequence The sequence to match against (search for).
- */
- public Layer2SequenceMatcher(List<PcapPacket> sequence) {
- mSequence = sequence;
- // Compute packet directions for sequence.
- mPacketDirections = new boolean[sequence.size()];
- for (int i = 0; i < sequence.size(); i++) {
- if (i == 0) {
- // No previous packet; boolean parameter is ignored in this special case.
- mPacketDirections[i] = getPacketDirection(null, true, sequence.get(i));
- } else {
- // Base direction marker on direction of previous packet.
- PcapPacket prevPkt = mSequence.get(i-1);
- boolean prevPktDirection = mPacketDirections[i-1];
- mPacketDirections[i] = getPacketDirection(prevPkt, prevPktDirection, sequence.get(i));
- }
- }
- }
-
- /**
- * Attempt to advance this {@code Layer2SequenceMatcher} by matching {@code packet} against the packet that this
- * {@code Layer2SequenceMatcher} expects as the next packet of the sequence it is searching for.
- * @param packet
- * @return {@code true} if this {@code Layer2SequenceMatcher} could advance by adding {@code packet} to its set of
- * matched packets, {@code false} otherwise.
- */
- public boolean matchPacket(PcapPacket packet) {
- if (getMatchedPacketsCount() == getTargetSequencePacketCount()) {
- // We already matched the entire sequence, so we can't match any more packets.
- return false;
- }
-
- // Verify that new packet pertains to same flow as previously matched packets, if any.
- if (getMatchedPacketsCount() > 0) {
- MacAddress pktSrc = PcapPacketUtils.getEthSrcAddr(packet);
- MacAddress pktDst = PcapPacketUtils.getEthDstAddr(packet);
- MacAddress earlierPktSrc = PcapPacketUtils.getEthSrcAddr(mMatchedPackets.get(0));
- MacAddress earlierPktDst = PcapPacketUtils.getEthDstAddr(mMatchedPackets.get(0));
- if (!(pktSrc.equals(earlierPktSrc) && pktDst.equals(earlierPktDst) ||
- pktSrc.equals(earlierPktDst) && pktDst.equals(earlierPktSrc))) {
- return false;
- }
- }
-
- // Get representative of the packet we expect to match next.
- PcapPacket expected = mSequence.get(mMatchedPackets.size());
- // First verify if the received packet has the length we're looking for.
- if (packet.getOriginalLength() == expected.getOriginalLength()) {
- // If this is the first packet, we only need to verify that its length is correct. Time constraints are
- // obviously satisfied as there are no previous packets. Furthermore, direction matches by definition as we
- // don't know the MAC of the device (or phone) in advance, so we can't enforce a rule saying "first packet
- // must originate from this particular MAC".
- if (getMatchedPacketsCount() == 0) {
- // Store packet as matched and advance.
- mMatchedPackets.add(packet);
- return true;
- }
- // Check if direction of packet matches expected direction.
- boolean actualDirection = getPacketDirection(mMatchedPackets.get(getMatchedPacketsCount()-1),
- mPacketDirections[getMatchedPacketsCount()-1], packet);
- boolean expectedDirection = mPacketDirections[getMatchedPacketsCount()];
- if (actualDirection != expectedDirection) {
- return false;
- }
- // Next apply timing constraints:
- // 1: to be a match, the packet must have a later timestamp than any other packet currently matched
- // 2: does adding the packet cause the max allowed time between first packet and last packet to be exceeded?
- if (!packet.getTimestamp().isAfter(mMatchedPackets.get(getMatchedPacketsCount()-1).getTimestamp())) {
- return false;
- }
- if (packet.getTimestamp().isAfter(mMatchedPackets.get(0).getTimestamp().
- plusMillis(TriggerTrafficExtractor.INCLUSION_WINDOW_MILLIS))) {
- return false;
- }
- // If we made it here, it means that this packet has the expected length, direction, and obeys the timing
- // constraints, so we store it and advance.
- mMatchedPackets.add(packet);
- if (mMatchedPackets.size() == mSequence.size()) {
- // TODO report (to observers?) that we are done?
- }
- return true;
- }
- return false;
- }
-
- public int getMatchedPacketsCount() {
- return mMatchedPackets.size();
- }
-
- public int getTargetSequencePacketCount() {
- return mSequence.size();
- }
-
- public List<PcapPacket> getTargetSequence() {
- return mSequence;
- }
-
- public List<PcapPacket> getMatchedPackets() {
- return mMatchedPackets;
- }
-
- /**
- * Utility for {@code getMatchedPackets().get(getMatchedPackets().size()-1)}.
- * @return The last matched packet, or {@code null} if no packets have been matched yet.
- */
- public PcapPacket getLastPacket() {
- return mSequence.size() > 0 ? mSequence.get(mSequence.size()-1) : null;
- }
-
- /**
- * Compute the direction of a packet based on the previous packet. If no previous packet is provided, the direction
- * of {@code currPkt} is {@code true} by definition.
- * @param prevPkt The previous packet, if any.
- * @param prevPktDirection The computed direction of the previous packet
- * @param currPkt The current packet for which the direction is to be determined.
- * @return The direction of {@code currPkt}.
- */
- private boolean getPacketDirection(PcapPacket prevPkt, boolean prevPktDirection, PcapPacket currPkt) {
- if (prevPkt == null) {
- // By definition, use true as direction marker for first packet
- return true;
- }
- if (PcapPacketUtils.getEthSrcAddr(prevPkt).equals(PcapPacketUtils.getEthSrcAddr(currPkt))) {
- // Current packet goes in same direction as previous packet.
- return prevPktDirection;
- } else {
- // Current packet goes in opposite direction of previous packet.
- return !prevPktDirection;
- }
- }
-
-
-}
projects / pingpong.git / blobdiff