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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: chpass.c,v 1.37 2009/10/27 23:59:36 deraadt Exp $	*/
/*	$NetBSD: chpass.c,v 1.8 1996/05/15 21:50:43 jtc Exp $	*/

/*-
 * Copyright (c) 1988, 1993, 1994
 *	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. 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 <sys/param.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/uio.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <util.h>

#include "chpass.h"

extern char *__progname;

enum { NEWSH, LOADENTRY, EDITENTRY } op;
uid_t uid;
#ifdef	YP
int	use_yp;
int	force_yp = 0;
#endif

void	baduser(void);
void	kbintr(int);
void	usage(void);

int
main(int argc, char *argv[])
{
	struct passwd *pw = NULL, *opw = NULL, lpw;
	int i, ch, pfd, tfd, dfd;
	char *tz, *arg = NULL;
	sigset_t fullset;

#ifdef	YP
	use_yp = _yp_check(NULL);
#endif
	/* We need to use the system timezone for date conversions. */
	if ((tz = getenv("TZ")) != NULL) {
	    unsetenv("TZ");
	    tzset();
	    setenv("TZ", tz, 1);
	}

	op = EDITENTRY;
	while ((ch = getopt(argc, argv, "a:s:ly")) != -1)
		switch(ch) {
		case 'a':
			op = LOADENTRY;
			arg = optarg;
			break;
		case 's':
			op = NEWSH;
			arg = optarg;
			break;
#ifdef	YP
		case 'l':
			use_yp = 0;
			break;
		case 'y':
			if (!use_yp) {
				warnx("YP not in use.");
				usage();
			}
			force_yp = 1;
			break;
#endif
		case '?':
		default:
			usage();
		}
	argc -= optind;
	argv += optind;

#ifdef	YP
	if (op == LOADENTRY && use_yp)
		errx(1, "cannot load using YP, use -l to load local.");
#endif
	uid = getuid();

	if (op == EDITENTRY || op == NEWSH)
		switch(argc) {
		case 0:
			pw = getpwuid(uid);
#ifdef	YP
			if (pw && !force_yp)
				use_yp = 0;
			else if (use_yp)
				pw = ypgetpwuid(uid);
#endif	/* YP */
			if (!pw)
				errx(1, "unknown user: uid %u", uid);
			break;
		case 1:
			pw = getpwnam(*argv);
#ifdef	YP
			if (pw && !force_yp)
				use_yp = 0;
			else if (use_yp)
				pw = ypgetpwnam(*argv);
#endif	/* YP */
			if (!pw)
				errx(1, "unknown user: %s", *argv);
			if (uid && uid != pw->pw_uid)
				baduser();
			break;
		default:
			usage();
		}

	if (op == LOADENTRY) {
		if (argc != 0)
			errx(1, "option -a does not accept user argument");
		if (uid)
			baduser();
		pw = &lpw;
		if (!pw_scan(arg, pw, NULL))
			exit(1);
		opw = getpwnam(pw->pw_name);
	}
	if (opw == NULL && (opw = pw_dup(pw)) == NULL)
		err(1, NULL);

	/* Edit the user passwd information if requested. */
	if (op == EDITENTRY) {
		char tempname[] = _PATH_VARTMP "pw.XXXXXXXXXX";
		int edit_status;

		if ((pw = pw_dup(pw)) == NULL)
			pw_error(NULL, 1, 1);
		dfd = mkstemp(tempname);
		if (dfd == -1 || fcntl(dfd, F_SETFD, 1) == -1)
			pw_error(tempname, 1, 1);
		display(tempname, dfd, pw);
		edit_status = edit(tempname, pw);
		close(dfd);
		unlink(tempname);

		switch (edit_status) {
		case EDIT_OK:
			break;
		case EDIT_NOCHANGE:
			pw_error(NULL, 0, 0);
			break;
		case EDIT_ERROR:
		default:
			pw_error(tempname, 1, 1);
			break;
		}
	}

	if (op == NEWSH) {
		/* protect p_shell -- it thinks NULL is /bin/sh */
		if (!arg[0])
			usage();
		if (p_shell(arg, pw, NULL))
			pw_error(NULL, 0, 1);
	}

	/* Drop user's real uid and block all signals to avoid a DoS. */
	setuid(0);
	sigfillset(&fullset);
	sigdelset(&fullset, SIGINT);
	sigprocmask(SIG_BLOCK, &fullset, NULL);

	/* Get the passwd lock file and open the passwd file for reading. */
	pw_init();
	for (i = 1; (tfd = pw_lock(0)) == -1; i++) {
		if (i == 4)
			(void)fputs("Attempting lock password file, "
			    "please wait or press ^C to abort", stderr);
		(void)signal(SIGINT, kbintr);
		if (i % 16 == 0)
			fputc('.', stderr);
		usleep(250000);
		(void)signal(SIGINT, SIG_IGN);
	}
	if (i >= 4)
		fputc('\n', stderr);
	pfd = open(_PATH_MASTERPASSWD, O_RDONLY, 0);
	if (pfd == -1 || fcntl(pfd, F_SETFD, 1) == -1)
		pw_error(_PATH_MASTERPASSWD, 1, 1);

#ifdef	YP
	if (use_yp) {
		if (pw_yp(pw, uid))
			pw_error(NULL, 0, 1);
		else {
			pw_abort();
			exit(0);
		}
	} else
#endif	/* YP */
	{
		/* Copy the passwd file to the lock file, updating pw. */
		pw_copy(pfd, tfd, pw, opw);

		/* If username changed we need to rebuild the entire db. */
		arg = !strcmp(opw->pw_name, pw->pw_name) ? pw->pw_name : NULL;

		/* Now finish the passwd file update. */
		if (pw_mkdb(arg, 0) == -1)
			pw_error(NULL, 0, 1);
	}

	exit(0);
}

void
baduser(void)
{

	errx(1, "%s", strerror(EACCES));
}

/* ARGSUSED */
void
kbintr(int signo)
{
	struct iovec iv[5];

	iv[0].iov_base = "\n";
	iv[0].iov_len = 1;
	iv[1].iov_base = __progname;
	iv[1].iov_len = strlen(__progname);
	iv[2].iov_base = ": ";
	iv[2].iov_len = 2;
	iv[3].iov_base = _PATH_MASTERPASSWD;
	iv[3].iov_len = sizeof(_PATH_MASTERPASSWD) - 1;
	iv[4].iov_base = " unchanged\n";
	iv[4].iov_len = 11;
	writev(STDERR_FILENO, iv, 5);

	_exit(1);
}

void
usage(void)
{

#ifdef	YP
	(void)fprintf(stderr,
	    "usage: %s [-l%s] [-s newshell] [user]\n",
	    __progname, use_yp ? "y" : "");
	(void)fprintf(stderr,
	    "       %s [-l] -a list\n", __progname);
#else
	(void)fprintf(stderr, "usage: %s [-s newshell] [user]\n", __progname);
	(void)fprintf(stderr, "       %s -a list\n", __progname);
#endif
	exit(1);
}