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avoid stdio; based on work by markus, millert, and I

/*
 * Copyright (c) 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$Id: readpass.c,v 1.8 1999/12/08 19:32:55 deraadt Exp $");

#include "xmalloc.h"
#include "ssh.h"

/*
 * Reads a passphrase from /dev/tty with echo turned off.  Returns the
 * passphrase (allocated with xmalloc), being very careful to ensure that
 * no other userland buffer is storing the password.
 */
char *
read_passphrase(const char *prompt, int from_stdin)
{
	char buf[1024], *p, ch;
	struct termios tio, saved_tio;
	sigset_t oset, nset;
	int input, output, echo = 0;
  
	if (from_stdin) {
		input = STDIN_FILENO;
		output = STDERR_FILENO;
	} else
		input = output = open("/dev/tty", O_RDWR);

	if (input == -1)
		fatal("You have no controlling tty.  Cannot read passphrase.\n");

	/* block signals, get terminal modes and turn off echo */
	sigemptyset(&nset);
	sigaddset(&nset, SIGINT);
	sigaddset(&nset, SIGTSTP);
	(void) sigprocmask(SIG_BLOCK, &nset, &oset);

	if (tcgetattr(input, &tio) == 0 && (tio.c_lflag & ECHO)) {
		echo = 1;
		saved_tio = tio;
		tio.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
		(void) tcsetattr(input, TCSANOW, &tio);
	}

	fflush(stdout);

	(void)write(output, prompt, strlen(prompt));
	for (p = buf; read(input, &ch, 1) == 1 && ch != '\n';)
		if (p < buf + sizeof(buf) - 1)
			*p++ = ch;
	*p = '\0';
	(void)write(output, "\n", 1);

	/* restore terminal modes and allow signals */
	if (echo)
		tcsetattr(input, TCSANOW, &saved_tio);
	(void) sigprocmask(SIG_SETMASK, &oset, NULL);

	if (!from_stdin)
		(void)close(input);
	p = xstrdup(buf);
	memset(buf, 0, sizeof(buf));
	return (p);
}