This Sample application attempts to authenticate a user * and reports whether or not the authentication was successful. */ public class SampleAcn { /** * Attempt to authenticate the user. * *
* * @param args input arguments for this application. These are ignored. */ public static void main(String[] args) { // Obtain a LoginContext, needed for authentication. Tell it // to use the LoginModule implementation specified by the // entry named "Sample" in the JAAS login configuration // file and to also use the specified CallbackHandler. LoginContext lc = null; try { lc = new LoginContext("Sample", new MyCallbackHandler()); } catch (LoginException le) { System.err.println("Cannot create LoginContext. " + le.getMessage()); System.exit(-1); } catch (SecurityException se) { System.err.println("Cannot create LoginContext. " + se.getMessage()); System.exit(-1); } // the user has 3 attempts to authenticate successfully int i; for (i = 0; i < 3; i++) { try { // attempt authentication lc.login(); // if we return with no exception, authentication succeeded break; } catch (LoginException le) { System.err.println("Authentication failed:"); System.err.println(" " + le.getMessage()); try { Thread.currentThread().sleep(3000); } catch (Exception e) { // ignore } } } // did they fail three times? if (i == 3) { System.out.println("Sorry"); System.exit(-1); } System.out.println("Authentication succeeded!"); } } /** * The application implements the CallbackHandler. * *
This application is text-based. Therefore it displays information * to the user using the OutputStreams System.out and System.err, * and gathers input from the user using the InputStream System.in. */ class MyCallbackHandler implements CallbackHandler { /** * Invoke an array of Callbacks. * *
*
* @param callbacks an array of Callback objects which contain
* the information requested by an underlying security
* service to be retrieved or displayed.
*
* @exception java.io.IOException if an input or output error occurs.
*
* @exception UnsupportedCallbackException if the implementation of this
* method does not support one or more of the Callbacks
* specified in the callbacks parameter.
*/
public void handle(Callback[] callbacks)
throws IOException, UnsupportedCallbackException {
for (int i = 0; i < callbacks.length; i++) {
if (callbacks[i] instanceof TextOutputCallback) {
// display the message according to the specified type
TextOutputCallback toc = (TextOutputCallback)callbacks[i];
switch (toc.getMessageType()) {
case TextOutputCallback.INFORMATION:
System.out.println(toc.getMessage());
break;
case TextOutputCallback.ERROR:
System.out.println("ERROR: " + toc.getMessage());
break;
case TextOutputCallback.WARNING:
System.out.println("WARNING: " + toc.getMessage());
break;
default:
throw new IOException("Unsupported message type: " +
toc.getMessageType());
}
} else if (callbacks[i] instanceof NameCallback) {
// prompt the user for a username
NameCallback nc = (NameCallback)callbacks[i];
System.err.print(nc.getPrompt());
System.err.flush();
nc.setName((new BufferedReader
(new InputStreamReader(System.in))).readLine());
} else if (callbacks[i] instanceof PasswordCallback) {
// prompt the user for sensitive information
PasswordCallback pc = (PasswordCallback)callbacks[i];
System.err.print(pc.getPrompt());
System.err.flush();
pc.setPassword(readPassword(System.in));
} else {
throw new UnsupportedCallbackException
(callbacks[i], "Unrecognized Callback");
}
}
}
// Reads user password from given input stream.
private char[] readPassword(InputStream in) throws IOException {
char[] lineBuffer;
char[] buf;
int i;
buf = lineBuffer = new char[128];
int room = buf.length;
int offset = 0;
int c;
loop: while (true) {
switch (c = in.read()) {
case -1:
case '\n':
break loop;
case '\r':
int c2 = in.read();
if ((c2 != '\n') && (c2 != -1)) {
if (!(in instanceof PushbackInputStream)) {
in = new PushbackInputStream(in);
}
((PushbackInputStream)in).unread(c2);
} else
break loop;
default:
if (--room < 0) {
buf = new char[offset + 128];
room = buf.length - offset - 1;
System.arraycopy(lineBuffer, 0, buf, 0, offset);
Arrays.fill(lineBuffer, ' ');
lineBuffer = buf;
}
buf[offset++] = (char) c;
break;
}
}
if (offset == 0) {
return null;
}
char[] ret = new char[offset];
System.arraycopy(buf, 0, ret, 0, offset);
Arrays.fill(buf, ' ');
return ret;
}
}