src/usr.bin/chpass/chpass.c

/*	$OpenBSD: chpass.c,v 1.50 2023/03/08 04:43:10 guenther 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/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;

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;

	/* 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:")) != -1)
		switch(ch) {
		case 'a':
			op = LOADENTRY;
			arg = optarg;
			break;
		case 's':
			op = NEWSH;
			arg = optarg;
			break;
		default:
			usage();
		}
	argc -= optind;
	argv += optind;

	uid = getuid();

	if (op == EDITENTRY || op == NEWSH)
		switch(argc) {
		case 0:
			pw = getpwuid_shadow(uid);
			if (!pw)
				errx(1, "unknown user: uid %u", uid);
			break;
		case 1:
			pw = getpwnam_shadow(*argv);
			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_shadow(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 = mkostemp(tempname, O_CLOEXEC);
		if (dfd == -1)
			pw_error(tempname, 1, 1);
		display(tempname, dfd, pw);

		if (unveil(_PATH_BSHELL, "x") == -1)
			err(1, "unveil %s", _PATH_BSHELL);
		if (unveil(_PATH_SHELLS, "r") == -1)
			err(1, "unveil %s", _PATH_SHELLS);
		if (unveil(tempname, "rc") == -1)
			err(1, "unveil %s", tempname);
		if (pledge("stdio rpath wpath cpath id proc exec unveil",
		    NULL) == -1)
			err(1, "pledge");

		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) {
		if (unveil(_PATH_SHELLS, "r") == -1)
			err(1, "unveil %s", _PATH_SHELLS);
		if (pledge("stdio rpath wpath cpath id proc exec unveil",
		    NULL) == -1)
			err(1, "pledge");

		/* 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);

	if (unveil(_PATH_MASTERPASSWD_LOCK, "rwc") == -1)
		err(1, "unveil %s", _PATH_MASTERPASSWD_LOCK);
	if (unveil(_PATH_MASTERPASSWD, "r") == -1)
		err(1, "unveil %s", _PATH_MASTERPASSWD);
	if (unveil(_PATH_PWD_MKDB, "x") == -1)
		err(1, "unveil %s", _PATH_PWD_MKDB);
	if (pledge("stdio rpath wpath cpath proc exec", NULL) == -1)
		err(1, "pledge");

	/* 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 to 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|O_CLOEXEC);
	if (pfd == -1)
		pw_error(_PATH_MASTERPASSWD, 1, 1);

	/* 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));
}

void
kbintr(int signo)
{
	dprintf(STDERR_FILENO, "\n%s: %s unchanged\n",
	    __progname, _PATH_MASTERPASSWD);
	_exit(1);
}

void
usage(void)
{

	(void)fprintf(stderr, "usage: %s [-s newshell] [user]\n", __progname);
	(void)fprintf(stderr, "       %s -a list\n", __progname);
	exit(1);
}