// Change the following line to a name for your version of this package
package passwords.sysman.emSDK.util.signing;
import java.io.IOException;
import java.io.PrintStream;
import java.io.PushbackInputStream;
import java.util.Arrays;
/**
* The static readPassword method in this class issues a password prompt
* on the console output and returns the char array password
* entered by the user on the console input.
*/
public final class ReadPassword {
//----------------------------------
/**
* Test driver for readPassword method.
* @param args the command line args
*/
public static void main(String[] args) {
char[] pass = ReadPassword.readPassword("Enter password: ");
System.out.println("The password just entered is \""
+ new String(pass) + "\"");
System.out.println("The password length is " + pass.length);
}
* Issues a password prompt on the console output and returns
* the char array password entered by the user on the console input.
* The password is not displayed on the console (chars are not echoed).
* As soon as the returned char array is not needed,
* it should be erased for security reasons (Arrays.fill(charArr, ' '));
* A password should never be stored as a java String.
*
* Note that Java 6 has a Console class with a readPassword method,
* but there is no equivalent in Java 5 or Java 1.4.
* The readPassword method here is based on Sun's suggestions at
* http://java.sun.com/developer/technicalArticles/Security/pwordmask.
*
* @param prompt the password prompt to issue
* @return new char array containing the password
* @throws RuntimeException if some error occurs
*/
public static final char[] readPassword(String prompt)
throws RuntimeException {
try {
StreamMasker masker = new StreamMasker(System.out, prompt);
Thread threadMasking = new Thread(masker);
int firstByte = -1;
PushbackInputStream inStream = null;
try {
threadMasking.start();
inStream = new PushbackInputStream(System.in);
firstByte = inStream.read();
} finally {
masker.stopMasking();
}
try {
threadMasking.join();
} catch (InterruptedException e) {
throw new RuntimeException("Interrupt occurred when reading password");
}
if (firstByte == -1) {
throw new RuntimeException("Console input ended unexpectedly");
}
if (System.out.checkError()) {
throw new RuntimeException("Console password prompt output error");
}
inStream.unread(firstByte);
return readLineSecure(inStream);
}
catch (IOException e) {
throw new RuntimeException("I/O error occurred when reading password");
}
}
//----------------------------------
/**
* Reads one line from an input stream into a char array in a secure way
* suitable for reading a password.
* The char array will never contain a '\n' or '\r'.
*
* @param inStream the pushback input stream
* @return line as a char array, not including end-of-line-chars;
* never null, but may be zero length array
* @throws RuntimeException if some error occurs
*/
private static final char[] readLineSecure(PushbackInputStream inStream)
throws RuntimeException {
if (inStream == null) {
throw new RuntimeException("readLineSecure inStream is null");
}
try {
char[] buffer = null;
try {
buffer = new char[128];
int offset = 0;
// EOL is '\n' (unix), '\r\n' (windows), '\r' (mac)
loop:
while (true) {
int c = inStream.read();
switch (c) {
case -1:
case '\n':
break loop;
case '\r':
int c2 = inStream.read();
if ((c2 != '\n') && (c2 != -1))
inStream.unread(c2);
break loop;
default:
buffer = checkBuffer(buffer, offset);
buffer[offset++] = (char) c;
break;
}
}
char[] result = new char[offset];
System.arraycopy(buffer, 0, result, 0, offset);
return result;
}
finally {
if (buffer != null)
Arrays.fill(buffer, ' ');
}
}
catch (IOException e) {
throw new RuntimeException("I/O error occurred when reading password");
}
}
//----------------------------------
/**
* This is a helper method for readLineSecure.
*
* @param buffer the current char buffer
* @param offset the current position in the buffer
* @return the current buffer if it is not yet full;
* otherwise return a larger buffer initialized with a copy
* of the current buffer and then erase the current buffer
* @throws RuntimeException if some error occurs
*/
private static final char[] checkBuffer(char[] buffer, int offset)
throws RuntimeException
{
if (buffer == null)
throw new RuntimeException("checkBuffer buffer is null");
if (offset < 0)
throw new RuntimeException("checkBuffer offset is negative");
if (offset < buffer.length)
return buffer;
else {
try {
char[] bufferNew = new char[offset + 128];
System.arraycopy(buffer, 0, bufferNew, 0, buffer.length);
return bufferNew;
} finally {
Arrays.fill(buffer, ' ');
}
}
}
//----------------------------------
/**
* This private class prints a one line prompt
* and erases reply chars echoed to the console.
*/
private static final class StreamMasker
extends Thread {
private static final String BLANKS = StreamMasker.repeatChars(' ', 10);
private String m_promptOverwrite;
private String m_setCursorToStart;
private PrintStream m_out;
private volatile boolean m_doMasking;
//----------------------------------
/**
* Constructor.
* @throws RuntimeException if some error occurs
*/
public StreamMasker(PrintStream outPrint, String prompt)
throws RuntimeException {
if (outPrint == null)
throw new RuntimeException("StreamMasker outPrint is null");
if (prompt == null)
throw new RuntimeException("StreamMasker prompt is null");
if (prompt.indexOf('\r') != -1)
throw new RuntimeException("StreamMasker prompt contains a CR");
if (prompt.indexOf('\n') != -1)
throw new RuntimeException("StreamMasker prompt contains a NL");
m_out = outPrint;
m_setCursorToStart = StreamMasker.repeatChars('\010',
prompt.length() + BLANKS.length());
m_promptOverwrite = m_setCursorToStart + prompt + BLANKS
+ m_setCursorToStart + prompt;
}
//----------------------------------
/**
* Begin masking until asked to stop.
* @throws RuntimeException if some error occurs
*/
public void run()
throws RuntimeException {
int priorityOriginal = Thread.currentThread().getPriority();
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
try {
m_doMasking = true;
while (m_doMasking) {
m_out.print(m_promptOverwrite);
if (m_out.checkError())
throw new RuntimeException("Console output error writing prompt");
try {
Thread.currentThread().sleep(1);
} catch (InterruptedException ie) {
Thread.currentThread().interrupt();
return;
}
}
m_out.print(m_setCursorToStart);
} finally {
Thread.currentThread().setPriority(priorityOriginal);
}
}
//----------------------------------
/**
* Instructs the thread to stop masking.
*/
public void stopMasking() {
m_doMasking = false;
}
//----------------------------------
/**
* Returns a repeated char string.
*
* @param c the char to repeat
* @param length the number of times to repeat the char
* @throws RuntimeException if some error occurs
*/
private static String repeatChars(char c, int length)
throws RuntimeException {
if (length < 0)
throw new RuntimeException("repeatChars length is negative");
StringBuffer sb = new StringBuffer(length);
for (int i = 0; i < length; i++)
sb.append(c);
return sb.toString();
}
}
}
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