/*      $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);
}