src/java/iotcloud/Slot.java

   1 package iotcloud;
   2 import java.util.Vector;
   3 import java.nio.ByteBuffer;
   4 import javax.crypto.Mac;
   5 import java.util.Arrays;
   6
   7 class Slot implements Liveness {
   8         static final int SLOT_SIZE=2048;
   9         static final int HMAC_SIZE=32;
  10
  11         private long seqnum;
  12         private byte[] prevhmac;
  13         private byte[] hmac;
  14         private long machineid;
  15         private Vector<Entry> entries;
  16         private int livecount;
  17         private boolean seqnumlive;
  18
  19         Slot(long _seqnum, long _machineid, byte[] _prevhmac, byte[] _hmac) {
  20                 seqnum=_seqnum;
  21                 machineid=_machineid;
  22                 prevhmac=_prevhmac;
  23                 hmac=_hmac;
  24                 entries=new Vector<Entry>();
  25                 livecount=1;
  26                 seqnumlive=true;
  27         }
  28
  29         Slot(long _seqnum, long _machineid, byte[] _prevhmac) {
  30                 this(_seqnum, _machineid, _prevhmac, new byte[HMAC_SIZE]);
  31         }
  32
  33         byte[] getHMAC() {
  34                 return hmac;
  35         }
  36
  37         byte[] getPrevHMAC() {
  38                 return prevhmac;
  39         }
  40
  41         void addEntry(Entry e) {
  42                 entries.add(e);
  43                 livecount++;
  44         }
  45
  46         Vector<Entry> getEntries() {
  47                 return entries;
  48         }
  49
  50         static Slot decode(byte[] array, Mac mac) {
  51                 mac.update(array, HMAC_SIZE, array.length-HMAC_SIZE);
  52                 byte[] realmac=mac.doFinal();
  53
  54                 ByteBuffer bb=ByteBuffer.wrap(array);
  55                 byte[] hmac=new byte[HMAC_SIZE];
  56                 byte[] prevhmac=new byte[HMAC_SIZE];
  57                 bb.get(hmac);
  58                 bb.get(prevhmac);
  59                 if (!Arrays.equals(realmac, hmac))
  60                         throw new Error("Server Error: Invalid HMAC!  Potential Attack!");
  61
  62                 long seqnum=bb.getLong();
  63                 long machineid=bb.getLong();
  64                 int numentries=bb.getInt();
  65                 Slot slot=new Slot(seqnum, machineid, prevhmac, hmac);
  66
  67                 for(int i=0; i<numentries; i++) {
  68                         slot.addEntry(Entry.decode(slot, bb));
  69                 }
  70
  71                 return slot;
  72         }
  73
  74         byte[] encode(Mac mac) {
  75                 byte[] array=new byte[SLOT_SIZE];
  76                 ByteBuffer bb=ByteBuffer.wrap(array);
  77                 bb.position(HMAC_SIZE);                                                                                                                                                                                                                                                 //Leave space for the HMACs
  78                 bb.put(prevhmac);
  79                 bb.putLong(seqnum);
  80                 bb.putLong(machineid);
  81                 bb.putInt(entries.size());
  82                 for(Entry entry:entries) {
  83                         entry.encode(bb);
  84                 }
  85                 //Compute our HMAC
  86                 mac.update(array, HMAC_SIZE, array.length-HMAC_SIZE);
  87                 byte[] realmac=mac.doFinal();
  88                 bb.position(0);
  89                 bb.put(realmac);
  90                 return array;
  91         }
  92
  93         long getSequenceNumber() {
  94                 return seqnum;
  95         }
  96
  97         long getMachineID() {
  98                 return machineid;
  99         }
 100
 101         byte[] getBytes() {
 102                 return null;
 103         }
 104
 105         void setDead() {
 106                 decrementLiveCount();
 107                 seqnumlive=false;
 108         }
 109
 110         void decrementLiveCount() {
 111                 livecount--;
 112         }
 113
 114         boolean isLive() {
 115                 return livecount > 0;
 116         }
 117
 118         public String toString() {
 119                 return "<"+getSequenceNumber()+", "+new String(getBytes())+">";
 120         }
 121 }