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