/*      $OpenBSD: local_passwd.c,v 1.64 2023/05/08 17:15:43 tobias Exp $        */

/*-
 * Copyright (c) 1990 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/types.h>
#include <sys/stat.h>
#include <sys/uio.h>

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

#define UNCHANGED_MSG   "Password unchanged."

static uid_t uid;
extern int pwd_check(login_cap_t *, char *);
extern int pwd_gettries(login_cap_t *);

int local_passwd(char *, int);
char *getnewpasswd(struct passwd *, login_cap_t *, int);
void kbintr(int);

int
local_passwd(char *uname, int authenticated)
{
        struct passwd *pw, *opw;
        login_cap_t *lc;
        sigset_t fullset;
        time_t period;
        int i, pfd, tfd = -1;
        int pwflags = _PASSWORD_OMITV7;

        if (!(pw = getpwnam_shadow(uname))) {
                warnx("unknown user %s.", uname);
                return(1);
        }

        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_LOGIN_CONF, "r") == -1)
                err(1, "unveil %s", _PATH_LOGIN_CONF);
        if (unveil(_PATH_LOGIN_CONF ".db", "r") == -1)
                err(1, "unveil %s.db", _PATH_LOGIN_CONF);
        if (unveil(_PATH_LOGIN_CONF_D, "r") == -1)
                err(1, "unveil %s", _PATH_LOGIN_CONF_D);
        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(_PATH_PWD_MKDB, "x") == -1)
                err(1, "unveil %s", _PATH_PWD_MKDB);
        if (pledge("stdio rpath wpath cpath getpw tty id proc exec", NULL) == -1)
                err(1, "pledge");

        if ((opw = pw_dup(pw)) == NULL) {
                warn(NULL);
                return(1);
        }
        if ((lc = login_getclass(pw->pw_class)) == NULL) {
                warnx("unable to get login class for user %s.", uname);
                free(opw);
                return(1);
        }

        uid = authenticated ? pw->pw_uid : getuid();
        if (uid && uid != pw->pw_uid) {
                warnx("login/uid mismatch, username argument required.");
                free(opw);
                return(1);
        }

        /* Get the new password. */
        pw->pw_passwd = getnewpasswd(pw, lc, authenticated);

        if (pledge("stdio rpath wpath cpath getpw id proc exec", NULL) == -1)
                err(1, "pledge");

        /* Reset password change time based on login.conf. */
        period = (time_t)login_getcaptime(lc, "passwordtime", 0, 0);
        if (period > 0) {
                pw->pw_change = time(NULL) + period;
        } else {
                /*
                 * If the pw change time is the same we only need
                 * to update the spwd.db file.
                 */
                if (pw->pw_change != 0)
                        pw->pw_change = 0;
                else
                        pwflags = _PASSWORD_SECUREONLY;
        }

        /* 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 (pledge("stdio rpath wpath cpath proc exec", NULL) == -1)
                err(1, "pledge");

        /* Get a lock on the passwd file and open it. */
        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);

        /* Update master.passwd file and rebuild spwd.db. */
        pw_copy(pfd, tfd, pw, opw);
        free(opw);
        if (pw_mkdb(uname, pwflags) == -1)
                pw_error(NULL, 0, 1);

        fprintf(stderr, "passwd: password updated successfully\n");

        return(0);
}

char *
getnewpasswd(struct passwd *pw, login_cap_t *lc, int authenticated)
{
        static char hash[_PASSWORD_LEN];
        char newpass[1024];
        char *p, *pref;
        int tries, pwd_tries;
        sig_t saveint, savequit;

        saveint = signal(SIGINT, kbintr);
        savequit = signal(SIGQUIT, kbintr);

        if (!authenticated) {
                fprintf(stderr, "Changing password for %s.\n", pw->pw_name);
                if (uid != 0 && pw->pw_passwd[0] != '\0') {
                        char oldpass[1024];

                        p = readpassphrase("Old password:", oldpass,
                            sizeof(oldpass), RPP_ECHO_OFF);
                        if (p == NULL || *p == '\0') {
                                fprintf(stderr, "%s\n", UNCHANGED_MSG);
                                pw_abort();
                                exit(p == NULL ? 1 : 0);
                        }
                        if (crypt_checkpass(p, pw->pw_passwd) != 0) {
                                errno = EACCES;
                                explicit_bzero(oldpass, sizeof(oldpass));
                                pw_error(NULL, 1, 1);
                        }
                        explicit_bzero(oldpass, sizeof(oldpass));
                }
        }

        pwd_tries = pwd_gettries(lc);

        for (newpass[0] = '\0', tries = -1;;) {
                char repeat[1024];

                p = readpassphrase("New password:", newpass, sizeof(newpass),
                    RPP_ECHO_OFF);
                if (p == NULL || *p == '\0') {
                        fprintf(stderr, "%s\n", UNCHANGED_MSG);
                        pw_abort();
                        exit(p == NULL ? 1 : 0);
                }
                if (strcmp(p, "s/key") == 0) {
                        fprintf(stderr, "That password collides with a system feature. Choose another.\n");
                        continue;
                }

                if ((pwd_tries == 0 || ++tries < pwd_tries) &&
                    pwd_check(lc, p) == 0)
                        continue;
                p = readpassphrase("Retype new password:", repeat, sizeof(repeat),
                    RPP_ECHO_OFF);
                if (p != NULL && strcmp(newpass, p) == 0) {
                        explicit_bzero(repeat, sizeof(repeat));
                        break;
                }
                fprintf(stderr, "Mismatch; try again, EOF to quit.\n");
                explicit_bzero(repeat, sizeof(repeat));
                explicit_bzero(newpass, sizeof(newpass));
        }

        (void)signal(SIGINT, saveint);
        (void)signal(SIGQUIT, savequit);

        pref = login_getcapstr(lc, "localcipher", NULL, NULL);
        if (crypt_newhash(newpass, pref, hash, sizeof(hash)) != 0) {
                fprintf(stderr, "Couldn't generate hash.\n");
                explicit_bzero(newpass, sizeof(newpass));
                pw_error(NULL, 0, 0);
        }
        explicit_bzero(newpass, sizeof(newpass));
        free(pref);
        return hash;
}

void
kbintr(int signo)
{
        dprintf(STDOUT_FILENO, "\n%s\n", UNCHANGED_MSG);
        _exit(0);
}