src/java/iotcloud/Table.java

   1 package iotcloud;
   2 import java.util.HashMap;
   3 import java.util.Arrays;
   4 import javax.crypto.spec.*;
   5 import javax.crypto.*;
   6
   7 public class Table {
   8         int numslots;
   9         HashMap<IoTString, IoTString> table=new HashMap<IoTString, IoTString>();
  10         SlotBuffer buffer;
  11         CloudComm cloud;
  12         private Mac hmac;
  13         long sequencenumber;
  14
  15         public Table(String baseurl, String password) {
  16                 initCloud(baseurl, password);
  17                 buffer = new SlotBuffer();
  18                 sequencenumber = 1;
  19         }
  20
  21         private void initCloud(String baseurl, String password) {
  22                 try {
  23                         SecretKeySpec secret=getKey(password);
  24                         Cipher encryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
  25                         encryptCipher.init(Cipher.ENCRYPT_MODE, secret);
  26                         Cipher decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
  27                         decryptCipher.init(Cipher.DECRYPT_MODE, secret);
  28                         hmac = Mac.getInstance("HmacSHA256");
  29                         hmac.init(secret);
  30                         cloud=new CloudComm(baseurl, encryptCipher, decryptCipher, hmac);
  31                 } catch (Exception e) {
  32                         throw new Error("Failed To Initialize Ciphers");
  33                 }
  34         }
  35
  36         private SecretKeySpec getKey(String password) {
  37                 try {
  38                         PBEKeySpec keyspec = new PBEKeySpec(password.toCharArray());
  39                         SecretKey key = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256").generateSecret(keyspec);
  40                         SecretKeySpec secret = new SecretKeySpec(key.getEncoded(), "AES");
  41                         return secret;
  42                 } catch (Exception e) {
  43                         throw new Error("Failed generating key.");
  44                 }
  45         }
  46
  47         public void update() {
  48                 Slot[] newslots=cloud.getSlots(sequencenumber);
  49                 validateandupdate(newslots);
  50         }
  51
  52         void validateandupdate(Slot[] newslots) {
  53                 //The cloud communication layer has checked slot HMACs already
  54                 //before decoding
  55
  56                 if (newslots.length==0)
  57                         return;
  58
  59                 long firstseqnum=newslots[0].getSequenceNumber();
  60                 if (firstseqnum < sequencenumber)
  61                         throw new Error("Server sent older slots!");
  62
  63                 checkHMACChain(newslots);
  64
  65                 if (firstseqnum == (buffer.getNewestSeqNum()+1)) {
  66                         //contiguous update
  67                 } else {
  68                         //non-contiguous update
  69                 }
  70
  71
  72         }
  73
  74         void checkHMACChain(Slot[] newslots) {
  75                 if (newslots[0].getSequenceNumber() == (buffer.getNewestSeqNum()+1)) {
  76                         Slot prevslot=buffer.getSlot(buffer.getNewestSeqNum());
  77                         Slot currslot=newslots[0];
  78                         if (!Arrays.equals(prevslot.getHMAC(), currslot.getPrevHMAC()))
  79                                 throw new Error("Error in HMAC Chain");
  80                 }
  81
  82                 for(int i=1; i < newslots.length; i++) {
  83                         Slot prevslot=newslots[i-1];
  84                         Slot currslot=newslots[i];
  85                         if (!Arrays.equals(prevslot.getHMAC(), currslot.getPrevHMAC()))
  86                                 throw new Error("Error in HMAC Chain");
  87                 }
  88         }
  89
  90 }