Add in a class that should handle storing some preference data encrypted.

app/src/main/java/com/magnatune/eyecreate/companionformagnatune/login/ObscuredSharedPreferences.java

@@ -0,0 +1,349 @@
+package com.magnatune.eyecreate.companionformagnatune.login;
+
+import java.io.UnsupportedEncodingException;
+import java.util.Map;
+import java.util.Set;
+
+import javax.crypto.Cipher;
+import javax.crypto.SecretKey;
+import javax.crypto.SecretKeyFactory;
+import javax.crypto.spec.PBEKeySpec;
+import javax.crypto.spec.PBEParameterSpec;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.provider.Settings;
+import android.util.Base64;
+import android.util.Log;
+
+
+/**
+ * Thanks to emmby at http://stackoverflow.com/questions/785973/what-is-the-most-appropriate-way-to-store-user-settings-in-android-application/6393502#6393502
+ *
+ * Documentation: http://right-handed-monkey.blogspot.com/2014/04/obscured-shared-preferences-for-android.html
+ * This class has the following additions over the original:
+ *  additional logic for handling the case for when the preferences were not originally encrypted, but now are.
+ *  The secret key is no longer hard coded, but defined at runtime based on the individual device.
+ *  The benefit is that if one device is compromised, it now only affects that device.
+ *
+ * Simply replace your own SharedPreferences object in this one, and any data you read/write will be automatically encrypted and decrypted.
+ *
+ * Updated usage:
+ *    ObscuredSharedPreferences prefs = ObscuredSharedPreferences.getPrefs(this, MY_APP_NAME, Context.MODE_PRIVATE);
+ *    //to get data
+ *    prefs.getString("foo", null);
+ *    //to store data
+ *    prefs.edit().putString("foo","bar").commit();
+ */
+public class ObscuredSharedPreferences implements SharedPreferences {
+    protected static final String UTF8 = "UTF-8";
+    //this key is defined at runtime based on ANDROID_ID which is supposed to last the life of the device
+    private static char[] SEKRIT=null;
+    private static byte[] SALT=null;
+
+    private static char[] backup_secret=null;
+    private static byte[] backup_salt=null;
+
+    protected SharedPreferences delegate;
+    protected Context context;
+
+    //Set to true if a decryption error was detected
+    //in the case of float, int, and long we can tell if there was a parse error
+    //this does not detect an error in strings or boolean - that requires more sophisticated checks
+    public static boolean decryptionErrorFlag = false;
+
+    /**
+     * Constructor
+     * @param context
+     * @param delegate - SharedPreferences object from the system
+     */
+    public ObscuredSharedPreferences(Context context, SharedPreferences delegate) {
+        this.delegate = delegate;
+        this.context = context;
+        //updated thanks to help from bkhall on github
+        ObscuredSharedPreferences.setNewKey(Settings.Secure.getString(context.getContentResolver(), Settings.Secure.ANDROID_ID));
+        ObscuredSharedPreferences.setNewSalt(Settings.Secure.getString(context.getContentResolver(), Settings.Secure.ANDROID_ID));
+    }
+
+    /**
+     * Only used to change to a new key during runtime.
+     * If you don't want to use the default per-device key for example
+     * @param key
+     */
+    public static void setNewKey(String key) {
+        SEKRIT = key.toCharArray();
+    }
+
+    /**
+     * Only used to change to a new salt during runtime.
+     * If you don't want to use the default per-device code for example
+     * @param salt - this must be a string in UT
+     */
+    public static void setNewSalt(String salt) {
+        try {
+            SALT = salt.getBytes(UTF8);
+        } catch (UnsupportedEncodingException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Accessor to grab the preferences object
+     * To improve performance for multiple accesses, please store the returned object in a variable for reuse
+     * @param c - the context used to access the preferences.
+     * @param domainName - domain the shared preferences should be stored under
+     * @param contextMode - Typically Context.MODE_PRIVATE
+     * @return
+     */
+    public synchronized static ObscuredSharedPreferences getPrefs(Context c, String domainName, int contextMode) {
+        //make sure to use application context since preferences live outside an Activity
+        //use for objects that have global scope like: prefs or starting services
+        ObscuredSharedPreferences prefs = new ObscuredSharedPreferences(
+                c.getApplicationContext(), c.getApplicationContext().getSharedPreferences(domainName, contextMode) );
+        return prefs;
+    }
+
+    public class Editor implements SharedPreferences.Editor {
+        protected SharedPreferences.Editor delegate;
+
+        public Editor() {
+            this.delegate = ObscuredSharedPreferences.this.delegate.edit();
+        }
+
+        @Override
+        public Editor putBoolean(String key, boolean value) {
+            delegate.putString(key, encrypt(Boolean.toString(value)));
+            return this;
+        }
+
+        @Override
+        public Editor putFloat(String key, float value) {
+            delegate.putString(key, encrypt(Float.toString(value)));
+            return this;
+        }
+
+        @Override
+        public Editor putInt(String key, int value) {
+            delegate.putString(key, encrypt(Integer.toString(value)));
+            return this;
+        }
+
+        @Override
+        public Editor putLong(String key, long value) {
+            delegate.putString(key, encrypt(Long.toString(value)));
+            return this;
+        }
+
+        @Override
+        public Editor putString(String key, String value) {
+            delegate.putString(key, encrypt(value));
+            return this;
+        }
+
+        @Override
+        public void apply() {
+            //to maintain compatibility with android level 7
+            delegate.commit();
+        }
+
+        @Override
+        public Editor clear() {
+            delegate.clear();
+            return this;
+        }
+
+        @Override
+        public boolean commit() {
+            return delegate.commit();
+        }
+
+        @Override
+        public Editor remove(String s) {
+            delegate.remove(s);
+            return this;
+        }
+
+        @Override
+        public android.content.SharedPreferences.Editor putStringSet(String key, Set<String> values) {
+            throw new RuntimeException("This class does not work with String Sets.");
+        }
+    }
+
+    public Editor edit() {
+        return new Editor();
+    }
+
+
+    @Override
+    public Map<String, ?> getAll() {
+        throw new UnsupportedOperationException(); // left as an exercise to the reader
+    }
+
+    @Override
+    public boolean getBoolean(String key, boolean defValue) {
+        //if these weren't encrypted, then it won't be a string
+        String v;
+        try {
+            v = delegate.getString(key, null);
+        } catch (ClassCastException e) {
+            return delegate.getBoolean(key, defValue);
+        }
+        //Boolean string values should be 'true' or 'false'
+        //Boolean.parseBoolean does not throw a format exception, so check manually
+        String parsed = decrypt(v);
+        if (!checkBooleanString(parsed) ) {
+            //could not decrypt the Boolean.  Maybe the wrong key was used.
+            decryptionErrorFlag = true;
+            Log.e(this.getClass().getName(), "Warning, could not decrypt the value.  Possible incorrect key used.");
+        }
+        return v!=null ? Boolean.parseBoolean(parsed) : defValue;
+    }
+
+    /**
+     * This function checks if a valid string is received on a request for a Boolean object
+     * @param str
+     * @return
+     */
+    private boolean checkBooleanString(String str) {
+        return ("true".equalsIgnoreCase(str) || "false".equalsIgnoreCase(str));
+    }
+
+    @Override
+    public float getFloat(String key, float defValue) {
+        String v;
+        try {
+            v = delegate.getString(key, null);
+        } catch (ClassCastException e) {
+            return delegate.getFloat(key, defValue);
+        }
+        try {
+            return Float.parseFloat(decrypt(v));
+        } catch (NumberFormatException e) {
+            //could not decrypt the number.  Maybe we are using the wrong key?
+            decryptionErrorFlag = true;
+            Log.e(this.getClass().getName(), "Warning, could not decrypt the value.  Possible incorrect key.  "+e.getMessage());
+        }
+        return defValue;
+    }
+
+    @Override
+    public int getInt(String key, int defValue) {
+        String v;
+        try {
+            v = delegate.getString(key, null);
+        } catch (ClassCastException e) {
+            return delegate.getInt(key, defValue);
+        }
+        try {
+            return Integer.parseInt(decrypt(v));
+        } catch (NumberFormatException e) {
+            //could not decrypt the number.  Maybe we are using the wrong key?
+            decryptionErrorFlag = true;
+            Log.e(this.getClass().getName(), "Warning, could not decrypt the value.  Possible incorrect key.  "+e.getMessage());
+        }
+        return defValue;
+    }
+
+    @Override
+    public long getLong(String key, long defValue) {
+        String v;
+        try {
+            v = delegate.getString(key, null);
+        } catch (ClassCastException e) {
+            return delegate.getLong(key, defValue);
+        }
+        try {
+            return Long.parseLong(decrypt(v));
+        } catch (NumberFormatException e) {
+            //could not decrypt the number.  Maybe we are using the wrong key?
+            decryptionErrorFlag = true;
+            Log.e(this.getClass().getName(), "Warning, could not decrypt the value.  Possible incorrect key.  "+e.getMessage());
+        }
+        return defValue;
+    }
+
+    @Override
+    public String getString(String key, String defValue) {
+        final String v = delegate.getString(key, null);
+        return v != null ? decrypt(v) : defValue;
+    }
+
+    @Override
+    public boolean contains(String s) {
+        return delegate.contains(s);
+    }
+
+    @Override
+    public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener onSharedPreferenceChangeListener) {
+        delegate.registerOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener);
+    }
+
+    @Override
+    public void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener onSharedPreferenceChangeListener) {
+        delegate.unregisterOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener);
+    }
+
+    @Override
+    public Set<String> getStringSet(String key, Set<String> defValues) {
+        throw new RuntimeException("This class does not work with String Sets.");
+    }
+
+    /**
+     * Push key allows you to hold the current key being used into a holding location so that it can be retrieved later
+     * The use case is for when you need to load a new key, but still want to restore the old one.
+     */
+    public static void pushKey() {
+        backup_secret = SEKRIT;
+    }
+
+    /**
+     * This takes the key previously saved by pushKey() and activates it as the current decryption key
+     */
+    public static void popKey() {
+        SEKRIT = backup_secret;
+    }
+
+    /**
+     * pushSalt() allows you to hold the current salt being used into a holding location so that it can be retrieved later
+     * The use case is for when you need to load a new salt, but still want to restore the old one.
+     */
+    public static void pushSalt() {
+        backup_salt = SALT;
+    }
+
+    /**
+     * This takes the value previously saved by pushSalt() and activates it as the current salt
+     */
+    public static void popSalt() {
+        SALT = backup_salt;
+    }
+
+    protected String encrypt( String value ) {
+
+        try {
+            final byte[] bytes = value!=null ? value.getBytes(UTF8) : new byte[0];
+            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
+            SecretKey key = keyFactory.generateSecret(new PBEKeySpec(SEKRIT));
+            Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
+            pbeCipher.init(Cipher.ENCRYPT_MODE, key, new PBEParameterSpec(SALT, 20));
+            return new String(Base64.encode(pbeCipher.doFinal(bytes), Base64.NO_WRAP),UTF8);
+        } catch( Exception e ) {
+            throw new RuntimeException(e);
+        }
+
+    }
+
+    protected String decrypt(String value){
+        try {
+            final byte[] bytes = value!=null ? Base64.decode(value,Base64.DEFAULT) : new byte[0];
+            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
+            SecretKey key = keyFactory.generateSecret(new PBEKeySpec(SEKRIT));
+            Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
+            pbeCipher.init(Cipher.DECRYPT_MODE, key, new PBEParameterSpec(SALT, 20));
+            return new String(pbeCipher.doFinal(bytes),UTF8);
+        } catch( Exception e) {
+            Log.e(this.getClass().getName(), "Warning, could not decrypt the value.  It may be stored in plaintext.  "+e.getMessage());
+            return value;
+        }
+    }
+}