org.daveware.passwordmaker

Class SecureCharArray

java.lang.Object

org.daveware.passwordmaker.SecureCharArray

All Implemented Interfaces:

CharSequence

Direct Known Subclasses:

SecureUTF8String

public class SecureCharArray
extends Object
implements CharSequence

Provides an array capable of erasing the contents upon request.

It's a very bad idea to store passwords in a java.lang.String object because once that object is created, you cannot guarantee that the contents will be erased. You can't get at the actual bytes inside the String object. Thus you cannot reset all the bytes to 0.

This object stores a plain array of chars allowing the data to be erased back to 0 at any given time.

ALWWAYS reset your password storage variables when you are through with them and be very wary of the stack.

Author:

Dave Marotti

Constructor Summary

Constructors

Modifier	Constructor and Description
	SecureCharArray()
	SecureCharArray(byte[] bytes)
protected	SecureCharArray(byte[] bytes, boolean decodeAsUTF8)
	SecureCharArray(char[] chars)
	SecureCharArray(int size)
	SecureCharArray(SecureCharArray copy)
	SecureCharArray(String str) Creates the object from a string (don't pass passwords in this way).

Method Summary

Modifier and Type	Method and Description
void	append(SecureCharArray arr) Appends another SecureCharArray to this one.
char	charAt(int index)
void	erase() Erases the data in this array by writing a pattern over every element of the array.
char	getCharAt(int index) Obtains the character at an index.
char[]	getData() Returns a reference to the data.
int	length()
void	prepend(SecureCharArray arr) Prepends this array with another SecureCharArray.
void	replace(SecureCharArray arr) Replaces the contents of this array with a copy of those in arr, resizing the array as needed.
void	resize(int size, boolean retainData) Resizes the array, optionally keeping the old data.
void	setCharAt(int index, char c) Sets the character at an index.
int	size() Gets the size of this array.
CharSequence	subSequence(int start, int end)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.CharSequence

chars, codePoints, toString

Constructor Detail

SecureCharArray

public SecureCharArray()

SecureCharArray

public SecureCharArray(int size)

SecureCharArray

public SecureCharArray(byte[] bytes)

Parameters:

bytes - - assumes no character encoding... Each byte will become its own char

SecureCharArray

protected SecureCharArray(byte[] bytes,
                          boolean decodeAsUTF8)

SecureCharArray

public SecureCharArray(char[] chars)

SecureCharArray

public SecureCharArray(SecureCharArray copy)

SecureCharArray

public SecureCharArray(String str)

Creates the object from a string (don't pass passwords in this way).

Parameters:

str - The string object to get the data from.

Method Detail

append

public void append(SecureCharArray arr)
            throws Exception

Appends another SecureCharArray to this one.

Parameters:

arr - The array to append.

Throws:

Exception - Upon size problems. (lol)

erase

public void erase()

Erases the data in this array by writing a pattern over every element of the array.

The pattern part probably isn't needed and probably doesn't do anything but it's there anyway. The important part is to reset all the elements back to 0.

getCharAt

public char getCharAt(int index)
               throws ArrayIndexOutOfBoundsException

Obtains the character at an index.

Parameters:

index - The index to obtain the character at.

Returns:

The character at the index.

Throws:

ArrayIndexOutOfBoundsException - Upon bad index.

getData

public char[] getData()

Returns a reference to the data.

Returns:

a reference to the data.

prepend

public void prepend(SecureCharArray arr)
             throws Exception

Prepends this array with another SecureCharArray.

Parameters:

arr - The array to prepend.

Throws:

Exception - Upon size problems. (lol)

replace

public void replace(SecureCharArray arr)
             throws Exception

Replaces the contents of this array with a copy of those in arr, resizing the array as needed.

Parameters:

arr - The copy to use.

Throws:

Exception - on exception

resize

public void resize(int size,
                   boolean retainData)
            throws Exception

Resizes the array, optionally keeping the old data.

Parameters:

size - The new size of the array. This must be 1 or larger.

retainData - Whether or not to keep the old data.

Throws:

Exception - If the size is 0 or less.

setCharAt

public void setCharAt(int index,
                      char c)
               throws ArrayIndexOutOfBoundsException

Sets the character at an index.

Parameters:

index - The index to set at.

c - The character to set.

Throws:

ArrayIndexOutOfBoundsException - Upon bad index.

size

public int size()

Gets the size of this array.

Returns:

The size of the array.

charAt

public char charAt(int index)

Specified by:

charAt in interface CharSequence

length

public int length()

Specified by:

length in interface CharSequence

subSequence

public CharSequence subSequence(int start,
                                int end)

Specified by:

subSequence in interface CharSequence

Throws:

ArrayIndexOutOfBoundsException - - if from < 0 or from > original.length()

IllegalArgumentException - - if from < to

See Also:

CharSequence.subSequence(int, int)