/* $OpenBSD: auth-passwd.c,v 1.48 2020/10/18 11:32:01 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Password authentication.  This file contains the functions to check whether
 * the password is valid for the user.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * Copyright (c) 1999 Dug Song.  All rights reserved.
 * Copyright (c) 2000 Markus Friedl.  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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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"

#include <sys/types.h>

#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>

#include "packet.h"
#include "sshbuf.h"
#include "ssherr.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "sshkey.h"
#include "hostfile.h"
#include "auth.h"
#include "auth-options.h"

extern struct sshbuf *loginmsg;
extern ServerOptions options;

#ifdef HAVE_LOGIN_CAP
extern login_cap_t *lc;
#endif


#define DAY             (24L * 60 * 60) /* 1 day in seconds */
#define TWO_WEEKS       (2L * 7 * DAY)  /* 2 weeks in seconds */

#define MAX_PASSWORD_LEN        1024

/*
 * Tries to authenticate the user using password.  Returns true if
 * authentication succeeds.
 */
int
auth_password(struct ssh *ssh, const char *password)
{
        Authctxt *authctxt = ssh->authctxt;
        struct passwd *pw = authctxt->pw;
        int result, ok = authctxt->valid;
#if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
        static int expire_checked = 0;
#endif

        if (strlen(password) > MAX_PASSWORD_LEN)
                return 0;

#ifndef HAVE_CYGWIN
        if (pw->pw_uid == 0 && options.permit_root_login != PERMIT_YES)
                ok = 0;
#endif
        if (*password == '\0' && options.permit_empty_passwd == 0)
                return 0;

#ifdef KRB5
        if (options.kerberos_authentication == 1) {
                int ret = auth_krb5_password(authctxt, password);
                if (ret == 1 || ret == 0)
                        return ret && ok;
                /* Fall back to ordinary passwd authentication. */
        }
#endif
#ifdef HAVE_CYGWIN
        {
                HANDLE hToken = cygwin_logon_user(pw, password);

                if (hToken == INVALID_HANDLE_VALUE)
                        return 0;
                cygwin_set_impersonation_token(hToken);
                return ok;
        }
#endif
#ifdef USE_PAM
        if (options.use_pam)
                return (sshpam_auth_passwd(authctxt, password) && ok);
#endif
#if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
        if (!expire_checked) {
                expire_checked = 1;
                if (auth_shadow_pwexpired(authctxt))
                        authctxt->force_pwchange = 1;
        }
#endif
        result = sys_auth_passwd(ssh, password);
        if (authctxt->force_pwchange)
                auth_restrict_session(ssh);
        return (result && ok);
}

#ifdef BSD_AUTH
static void
warn_expiry(Authctxt *authctxt, auth_session_t *as)
{
        int r;
        quad_t pwtimeleft, actimeleft, daysleft, pwwarntime, acwarntime;

        pwwarntime = acwarntime = TWO_WEEKS;

        pwtimeleft = auth_check_change(as);
        actimeleft = auth_check_expire(as);
#ifdef HAVE_LOGIN_CAP
        if (authctxt->valid) {
                pwwarntime = login_getcaptime(lc, "password-warn", TWO_WEEKS,
                    TWO_WEEKS);
                acwarntime = login_getcaptime(lc, "expire-warn", TWO_WEEKS,
                    TWO_WEEKS);
        }
#endif
        if (pwtimeleft != 0 && pwtimeleft < pwwarntime) {
                daysleft = pwtimeleft / DAY + 1;
                if ((r = sshbuf_putf(loginmsg,
                    "Your password will expire in %lld day%s.\n",
                    daysleft, daysleft == 1 ? "" : "s")) != 0)
                        fatal_fr(r, "buffer error");
        }
        if (actimeleft != 0 && actimeleft < acwarntime) {
                daysleft = actimeleft / DAY + 1;
                if ((r = sshbuf_putf(loginmsg,
                    "Your account will expire in %lld day%s.\n",
                    daysleft, daysleft == 1 ? "" : "s")) != 0)
                        fatal_fr(r, "buffer error");
        }
}

int
sys_auth_passwd(struct ssh *ssh, const char *password)
{
        Authctxt *authctxt = ssh->authctxt;
        auth_session_t *as;
        static int expire_checked = 0;

        as = auth_usercheck(authctxt->pw->pw_name, authctxt->style, "auth-ssh",
            (char *)password);
        if (as == NULL)
                return (0);
        if (auth_getstate(as) & AUTH_PWEXPIRED) {
                auth_close(as);
                auth_restrict_session(ssh);
                authctxt->force_pwchange = 1;
                return (1);
        } else {
                if (!expire_checked) {
                        expire_checked = 1;
                        warn_expiry(authctxt, as);
                }
                return (auth_close(as));
        }
}
#elif !defined(CUSTOM_SYS_AUTH_PASSWD)
int
sys_auth_passwd(struct ssh *ssh, const char *password)
{
        Authctxt *authctxt = ssh->authctxt;
        struct passwd *pw = authctxt->pw;
        char *encrypted_password, *salt = NULL;

        /* Just use the supplied fake password if authctxt is invalid */
        char *pw_password = authctxt->valid ? shadow_pw(pw) : pw->pw_passwd;

        if (pw_password == NULL)
                return 0;

        /* Check for users with no password. */
        if (strcmp(pw_password, "") == 0 && strcmp(password, "") == 0)
                return (1);

        /*
         * Encrypt the candidate password using the proper salt, or pass a
         * NULL and let xcrypt pick one.
         */
        if (authctxt->valid && pw_password[0] && pw_password[1])
                salt = pw_password;
        encrypted_password = xcrypt(password, salt);

        /*
         * Authentication is accepted if the encrypted passwords
         * are identical.
         */
        return encrypted_password != NULL &&
            strcmp(encrypted_password, pw_password) == 0;
}
#endif