Jayanga Dissanayake's Blog: encryption

There are some instances, you want to store your passwords in files to be used by the programs or scripts. But storing your passwords in plain text is not a good idea. Use the SecurePasswordVault to encrypt your passwords before storing and get it decrypted when you want to use it.

You can use the SecurePasswordVault described here to store any number of encrypted passwords. Passwords are stored as key value pairs.

Key - any name given by the user for the password
Value - encrypted password

SecurePasswordVault will create a file with the given name in the working directory if it doesn't exist. If a file exist then the information in that file will be read.

Passwords are encrypted using the MAC address of the network card. SecurePasswordVault will use the first network card MAC which is not the loop back interface. So the encrypted file can only be decrypted with that particular MAC address. If you want to reset the pass word details, just delete the password file and run the SecurePasswordVault.

You can download the sample code from the following Github repository
https://github.com/jsdjayanga/secure_password

package com.wso2.devgov;

import org.bouncycastle.util.encoders.Base64;

import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.Security;
import java.util.*;

/**
* Created by jayanga on 3/31/14.
*/
public class SecurePasswordVault {

    private static final int AES_KEY_LEN = 32;
    private static final int PASSWORD_LEN = 256;
    
    private static boolean initialized;
    private final String secureFile;
    private final byte[] networkHardwareHaddress;
    private Map<String, String> secureDataMap;
    private List<String> secureDataList;

    SecretKeySpec secretKey;

    public SecurePasswordVault(String filename, String[] secureData) throws IOException {

        Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

        initialized = false;
        secureFile = filename;
        networkHardwareHaddress = SecurePasswordVault.readNetworkHardwareAddress();
        secureDataMap = new HashMap<String, String>();

        this.secureDataList = new ArrayList<String>(secureData.length);
        Collections.addAll(secureDataList, secureData);

        byte[] key = new byte[AES_KEY_LEN];
        Arrays.fill(key, (byte)0);

        for(int index = 0; index < networkHardwareHaddress.length; index++){
            key[index] = networkHardwareHaddress[index];
        }

        secretKey = new SecretKeySpec(key, "AES");

        if (!isInitialized()){
            readSecureData(secureDataList);
            persistSecureData();
        }

        readSecureDataFromFile();
    }
    
    private boolean isInitialized(){
        if (initialized == true){
            return true;
        }else{
            File file = new File(secureFile);
            if (file.exists()){
                initialized = true;
                return initialized;
            }
        }
        return false;
    }

    private static byte[] readNetworkHardwareAddress() throws SocketException {
        Enumeration<NetworkInterface> networkInterfaceEnumeration = NetworkInterface.getNetworkInterfaces();
        if (networkInterfaceEnumeration != null){
            NetworkInterface networkInterface = null;
            while (networkInterfaceEnumeration.hasMoreElements()){
                networkInterface = networkInterfaceEnumeration.nextElement();
                if (!networkInterface.isLoopback()){
                    break;
                }
            }

            if (networkInterface == null){
                networkInterface = networkInterfaceEnumeration.nextElement();
            }

            byte[] hwaddr = networkInterface.getHardwareAddress();

            return hwaddr;
        }else{
            throw new RuntimeException("Cannot initialize. Failed to generate unique id.");
        }
    }

    private byte[] encrypt(String word) {
        byte[] password = new byte[PASSWORD_LEN];
        Arrays.fill(password, (byte)0);

        byte[] pw = new byte[0];

        try {
            pw = word.getBytes("UTF-8");

            for(int index = 0; index < pw.length; index++){
                password[index] = pw[index];
            }

            byte[] cipherText = new byte[password.length];

            Cipher cipher = null;
            try {
                cipher = Cipher.getInstance("AES/ECB/NoPadding");

                try {
                    cipher.init(Cipher.ENCRYPT_MODE, secretKey);

                    int ctLen = 0;
                    try {
                        ctLen = cipher.update(password, 0, password.length, cipherText, 0);
                        ctLen += cipher.doFinal(cipherText, ctLen);

                        return cipherText;
                    } catch (ShortBufferException e) {
                        e.printStackTrace();
                    } catch (BadPaddingException e) {
                        e.printStackTrace();
                    } catch (IllegalBlockSizeException e) {
                        e.printStackTrace();
                    }
                } catch (InvalidKeyException e) {
                    e.printStackTrace();
                }
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
            } catch (NoSuchPaddingException e) {
                e.printStackTrace();
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        return null;
    }

    private String decrypt(byte[] cipherText) {
        byte[] plainText = new byte[PASSWORD_LEN];

        Cipher cipher = null;
        try {
            cipher = Cipher.getInstance("AES/ECB/NoPadding");

            try {
                cipher.init(Cipher.DECRYPT_MODE, secretKey);

                int plainTextLen = 0;
                try {
                    plainTextLen = cipher.update(cipherText, 0, PASSWORD_LEN, plainText, 0);

                    try {
                        plainTextLen += cipher.doFinal(plainText, plainTextLen);
                        String password = new String(plainText);
                        return password.trim();

                    } catch (IllegalBlockSizeException e) {
                        e.printStackTrace();
                    } catch (BadPaddingException e) {
                        e.printStackTrace();
                    }
                } catch (ShortBufferException e) {
                    e.printStackTrace();
                }


            } catch (InvalidKeyException e) {
                e.printStackTrace();
            }
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        }

        return null;
    }

    public void readSecureData(List<String> secureDataList) throws IOException {
        BufferedReader bufferRead = new BufferedReader(new InputStreamReader(System.in));

        for(int index = 0; index < secureDataList.size(); index++){
            System.out.println("Please enter the value for :" + secureDataList.get(index));

            String value = new String(Base64.encode(encrypt(bufferRead.readLine())));
            secureDataMap.put(secureDataList.get(index), value);
        }
    }

    public String getSecureData(String key) {
        String value = secureDataMap.get(key);
        if (value != null){
            return decrypt(Base64.decode(value.getBytes()));
        }

        throw new RuntimeException("Given key is unknown. [key=" + key + "]");
    }

    private void readSecureDataFromFile() throws IOException {
        BufferedReader br = new BufferedReader(new FileReader(secureFile));

        String line;
        while ((line = br.readLine()) != null){
            int dividerPoint = line.indexOf("=");
            if (dividerPoint > 0){
                secureDataMap.put(line.substring(0, dividerPoint), line.substring(dividerPoint + 1));
            }
        }
    }

    private void persistSecureData() throws IOException {
        FileWriter fileWriter = new FileWriter(secureFile);

        for(String key : secureDataMap.keySet()){
            fileWriter.append(key + "=" + secureDataMap.get(key) + "\n");
        }

        fileWriter.close();
    }
}

Jayanga Dissanayake's Blog

Friday, May 23, 2014

Simple SecurePasswordVault in Java

Thursday, December 26, 2013

Encryption