AmazonSharedPreferencesWrapper.java

/*
 * Copyright 2010-2013 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package com.amazonaws.demo.s3uploader;

import android.content.SharedPreferences;

import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.BasicSessionCredentials;

/**
 * This utility class is used to store content in Android's Shared Preferences. For maximum security the preferences should be private.
 */
public class AmazonSharedPreferencesWrapper {
	
	private static final String AWS_ACCESS_KEY = "AWS_ACCESS_KEY";
	private static final String AWS_SECRET_KEY = "AWS_SECRET_KEY";
	private static final String AWS_SECURITY_TOKEN = "AWS_SECURITY_TOKEN";
	private static final String AWS_EXPIRATION_DATE = "AWS_EXPIRATION_DATE";
	
	private static final String AWS_DEVICE_UID = "AWS_DEVICE_UID";
	private static final String AWS_DEVICE_KEY = "AWS_DEVICE_KEY";
    private static final String AWS_DEVICE_USERNAME = "AWS_DEVICE_USERNAME";

	
	/**
	 * Set all of the Shared Preferences used by the Token Vending Machine to null. This function is useful if the user needs/wants to log out to
	 * clear any user specific information.
	 */
	public static void wipe( SharedPreferences sharedPreferences ) {
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_DEVICE_UID, null );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_DEVICE_KEY, null );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_ACCESS_KEY, null );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_SECRET_KEY, null );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_SECURITY_TOKEN, null );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_EXPIRATION_DATE, null );
        AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_DEVICE_USERNAME, null );

	}
	
	/**
     * Stores the username that was registered in the Shared Preferences.
     */       
    public static void storeUsername( SharedPreferences sharedPreferences, String username ) {
        AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_DEVICE_USERNAME, username );
    }

    /**
     * Returns the current UID stored in Shared Preferences.
     */       
    public static String getUsername( SharedPreferences sharedPreferences ) {
        return AmazonSharedPreferencesWrapper.getValueFromSharedPreferences( sharedPreferences, AWS_DEVICE_USERNAME );
    }
    
	/**
	 * Stores the UID and Key that were registered in the Shared Preferences. The UID and Key and used to encrypt/decrypt the Token that is returned
	 * from the Token Vending Machine.
	 */
	public static void registerDeviceId( SharedPreferences sharedPreferences, String uid, String key ) {
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_DEVICE_UID, uid );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_DEVICE_KEY, key );
	}
	
	/**
	 * Returns the current UID stored in Shared Preferences.
	 */
	public static String getUidForDevice( SharedPreferences sharedPreferences ) {
		return AmazonSharedPreferencesWrapper.getValueFromSharedPreferences( sharedPreferences, AWS_DEVICE_UID );
	}
	
	/**
	 * Returns the current Key stored in Shared Preferences.
	 */
	public static String getKeyForDevice( SharedPreferences sharedPreferences ) {
		return AmazonSharedPreferencesWrapper.getValueFromSharedPreferences( sharedPreferences, AWS_DEVICE_KEY );
	}
	
	/**
	 * Gets the AWS Access Key, AWS Secret Key and Security Token currently stored in Shared Preferences. Then creates a Credentials object and
	 * returns that object.
	 */
	public static AWSCredentials getCredentialsFromSharedPreferences( SharedPreferences sharedPreferences ) {
		String accessKey = AmazonSharedPreferencesWrapper.getValueFromSharedPreferences( sharedPreferences, AWS_ACCESS_KEY );
		String secretKey = AmazonSharedPreferencesWrapper.getValueFromSharedPreferences( sharedPreferences, AWS_SECRET_KEY );
		String securityToken = AmazonSharedPreferencesWrapper.getValueFromSharedPreferences( sharedPreferences, AWS_SECURITY_TOKEN );
		
		return new BasicSessionCredentials( accessKey, secretKey, securityToken );
	}
	
	/**
	 * Checks if the current Token's expiration date stored in Shared Preferences has expired. A token that has expired or will expire in fifteen
	 * minutes or less is considered expired.
	 */
	public static boolean areCredentialsExpired( SharedPreferences sharedPreferences ) {
		String expirationDate = AmazonSharedPreferencesWrapper.getValueFromSharedPreferences( sharedPreferences, AWS_EXPIRATION_DATE );
		if ( expirationDate == null ) {
			return true;
		}
		else {
			long timeInSeconds = Long.parseLong( expirationDate );
			return ( timeInSeconds < ( System.currentTimeMillis() + 15 * 60 * 100 ) );
		}
	}
	
	/**
	 * Stores the four pieces of information associated with a Token in the Shared Preferences.
	 */
	public static void storeCredentialsInSharedPreferences( SharedPreferences sharedPreferences, String accessKey, String secretKey, String securityToken, String expirationDate ) {
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_ACCESS_KEY, accessKey );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_SECRET_KEY, secretKey );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_SECURITY_TOKEN, securityToken );
		AmazonSharedPreferencesWrapper.storeValueInSharedPreferences( sharedPreferences, AWS_EXPIRATION_DATE, expirationDate );
	}
	
	protected static void storeValueInSharedPreferences( SharedPreferences sharedPreferences, String key, String value ) {
		SharedPreferences.Editor editor = sharedPreferences.edit();
		editor.putString( key, value );
		editor.commit();
	}
	
	protected static String getValueFromSharedPreferences( SharedPreferences sharedPreferences, String key ) {
		return sharedPreferences.getString( key, null );
	}
}