Android Open Source - lastpass-android Preferences

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License

The source code is released under:

Copyright (c) 2013 Nicholas Hinds Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Sof...

Java Source Code

package com.nhinds.lastpass.android;
/*from  www  . j a va 2 s . c o m*/
import java.security.GeneralSecurityException;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.nhinds.lastpass.encryption.AES256EncryptionProvider;
import com.nhinds.lastpass.encryption.EncryptionProvider;
import com.nhinds.lastpass.encryption.KeyProvider;
import com.nhinds.lastpass.encryption.PBKDF2SHA256KeyProvider;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;

public class Preferences {
  private static final Logger LOGGER = LoggerFactory.getLogger(Preferences.class);
  
  private static final String PREFERENCES_NAME = Preferences.class.getSimpleName();
  
  private static final String REMEMBERED_EMAIL_PREF = "REMEMBERED_EMAIL";
  private static final String REMEMBERED_PASSWORD_PREF = "REMEMBERED_PASSWORD";
  
  private static final KeyProvider KEY_PROVIDER = new PBKDF2SHA256KeyProvider();
  private static final int KEY_ITERATIONS = 100;
  
  private final Context context;
  private EncryptionProvider encryptionProvider;
  
  public Preferences(final Context context) {
    this.context = context;
  }
  
  private EncryptionProvider getEncryptionProvider() {
    if (this.encryptionProvider == null) {
      this.encryptionProvider = new AES256EncryptionProvider(getKey());
    }
    return this.encryptionProvider;
  }
  
  private byte[] getKey() {
    String deviceId = LastPassDeviceId.get(context);
    try {
      return KEY_PROVIDER.getKey(deviceId, deviceId, KEY_ITERATIONS);
    } catch (GeneralSecurityException e) {
      throw new RuntimeException("Error generating key", e);
    }
  }

  private SharedPreferences getPreferences() {
    return this.context.getSharedPreferences(PREFERENCES_NAME, Activity.MODE_PRIVATE);
  }
  
  private String getPreference(String preference) {
    return getPreferences().getString(preference, null);
  }
  
  /** @return the remembered email for login, or null if the email is not set */
  public String getRememberedEmail() {
    return getPreference(REMEMBERED_EMAIL_PREF);
  }

  /** 
   * Set the remembered email for login
   *
   * @param email The email to remember. May be null.
   */
  public void setRememberedEmail(final String email) {
    getPreferences().edit().putString(REMEMBERED_EMAIL_PREF, email).apply();
  }
  
  /** @return the remembered password for login, or null if the password is not set */
  public String getRememberedPassword() {
    return decrypt(getPreference(REMEMBERED_PASSWORD_PREF));
  }

  /** 
   * Set the remembered password for login.
   * <p>
   * This is encrypted internally to prevent casual observation, although a user with full control over the device would be able to gain access to the decryption key.
   *
   * @param password The encrypted password to remember. May be null.
   */
  public void setRememberedPassword(final String password) {
    getPreferences().edit().putString(REMEMBERED_PASSWORD_PREF, encrypt(password)).apply();
  }

  /**
   * Convenience method to set both the remembered email and password for login at once
   * 
   * @see #setRememberedEmail(String)
   * @see #setRememberedPassword(String)
   */
  public void setRememberedEmailAndPassword(final String email, final String password) {
    getPreferences().edit().putString(REMEMBERED_EMAIL_PREF, email).putString(REMEMBERED_PASSWORD_PREF, encrypt(password)).apply();
  }

  private String decrypt(String preference) {
    if (preference == null)
      return null;
    try {
      return getEncryptionProvider().decrypt(Hex.decodeHex(preference.toCharArray()));
    } catch (final DecoderException e) {
      LOGGER.error("Error decrypting string, returning null", e);
      return null;
    }
  }

  private String encrypt(String password) {
    if (password == null)
      return null;
    return new String(Hex.encodeHex(getEncryptionProvider().encrypt(password)));
  }
}

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