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 {
   8         public static final int SLOT_SIZE=2048;
   9         public static final int HMAC_SIZE=32;
  10
  11         long seqnum;
  12         byte[] prevhmac;
  13         byte[] hmac;
  14         long machineid;
  15         Vector<Entry> entries;
  16
  17         Slot(long _seqnum, long _machineid, byte[] _prevhmac, byte[] _hmac, Vector<Entry> _entries) {
  18                 seqnum=_seqnum;
  19                 machineid=_machineid;
  20                 prevhmac=_prevhmac;
  21                 hmac=_hmac;
  22                 entries=_entries;
  23         }
  24
  25         Slot(long _seqnum, byte[] _bytes) {
  26                 seqnum=_seqnum;
  27         }
  28
  29         byte[] getHMAC() {
  30                 return hmac;
  31         }
  32
  33         byte[] getPrevHMAC() {
  34                 return prevhmac;
  35         }
  36
  37         static Slot decode(byte[] array, Mac mac) {
  38                 mac.update(array, HMAC_SIZE, array.length-HMAC_SIZE);
  39                 byte[] realmac=mac.doFinal();
  40
  41                 ByteBuffer bb=ByteBuffer.wrap(array);
  42                 byte[] hmac=new byte[HMAC_SIZE];
  43                 byte[] prevhmac=new byte[HMAC_SIZE];
  44                 bb.get(hmac);
  45                 bb.get(prevhmac);
  46                 if (!Arrays.equals(realmac, hmac))
  47                         throw new Error("Invalid HMAC!  Potential Attack!");
  48
  49                 long seqnum=bb.getLong();
  50                 long machineid=bb.getLong();
  51                 int numentries=bb.getInt();
  52                 Vector<Entry> entries=new Vector<Entry>();
  53                 for(int i=0;i<numentries;i++) {
  54                         entries.add(Entry.decode(bb));
  55                 }
  56
  57                 return new Slot(seqnum, machineid, prevhmac, hmac, entries);
  58         }
  59
  60         byte[] encode(Mac mac) {
  61                 byte[] array=new byte[SLOT_SIZE];
  62                 ByteBuffer bb=ByteBuffer.wrap(array);
  63                 bb.position(HMAC_SIZE); //Leave space for the HMACs
  64                 bb.put(prevhmac);
  65                 bb.putLong(seqnum);
  66                 bb.putLong(machineid);
  67                 bb.putInt(entries.size());
  68                 for(Entry entry:entries) {
  69                         entry.encode(bb);
  70                 }
  71                 //Compute our HMAC
  72                 mac.update(array, HMAC_SIZE, array.length-HMAC_SIZE);
  73                 byte[] realmac=mac.doFinal();
  74                 bb.position(0);
  75                 bb.put(realmac);
  76                 return array;
  77         }
  78
  79         long getSequenceNumber() {
  80                 return seqnum;
  81         }
  82
  83         byte[] getBytes() {
  84                 return null;
  85         }
  86
  87         public String toString() {
  88                 return "<"+getSequenceNumber()+", "+new String(getBytes())+">";
  89         }
  90 }