/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright 1998 Juniper Networks, Inc.
 * All rights reserved.
 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * Portions of this software was developed for the FreeBSD Project by
 * ThinkSec AS and NAI Labs, the Security Research Division of Network
 * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
 * ("CBOSS"), as part of the DARPA CHATS research program.
 *
 * 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. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <login_cap.h>
#include <netdb.h>
#include <pwd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <syslog.h>
#include <time.h>
#include <unistd.h>

#include <libutil.h>

#ifdef YP
#include <ypclnt.h>
#endif

#define PAM_SM_AUTH
#define PAM_SM_ACCOUNT
#define PAM_SM_PASSWORD

#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_mod_misc.h>

#define PASSWORD_HASH           "md5"
#define DEFAULT_WARN            (2L * 7L * 86400L)  /* Two weeks */
#define SALTSIZE                32

#define LOCKED_PREFIX           "*LOCKED*"
#define LOCKED_PREFIX_LEN       (sizeof(LOCKED_PREFIX) - 1)

static void makesalt(char [SALTSIZE + 1]);

static char password_hash[] =           PASSWORD_HASH;

#define PAM_OPT_LOCAL_PASS      "local_pass"
#define PAM_OPT_NIS_PASS        "nis_pass"

/*
 * authentication management
 */
PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags,
    int argc __unused, const char *argv[] __unused)
{
        login_cap_t *lc;
        struct passwd *pwd;
        int retval;
        const char *pass, *user, *realpw, *prompt;
        const char *emptypasswd = "";

        if (openpam_get_option(pamh, PAM_OPT_AUTH_AS_SELF)) {
                user = getlogin();
        } else {
                retval = pam_get_user(pamh, &user, NULL);
                if (retval != PAM_SUCCESS)
                        return (retval);
        }
        pwd = getpwnam(user);

        PAM_LOG("Got user: %s", user);

        if (pwd != NULL) {
                PAM_LOG("Doing real authentication");
                realpw = pwd->pw_passwd;
                if (realpw[0] == '\0') {
                        if (!(flags & PAM_DISALLOW_NULL_AUTHTOK) &&
                            openpam_get_option(pamh, PAM_OPT_NULLOK))
                                return (PAM_SUCCESS);
                        PAM_LOG("Password is empty, using fake password");
                        realpw = "*";
                }
                /*
                 * Check whether the saved password hash matches the one
                 * generated from an empty password - as opposed to empty
                 * saved password hash, which is handled above.
                 */
                if (!(flags & PAM_DISALLOW_NULL_AUTHTOK) &&
                    openpam_get_option(pamh, PAM_OPT_EMPTYOK) &&
                    strcmp(crypt(emptypasswd, realpw), realpw) == 0)
                        return (PAM_SUCCESS);
                lc = login_getpwclass(pwd);
        } else {
                PAM_LOG("Doing dummy authentication");
                realpw = "*";
                lc = login_getclass(NULL);
        }
        prompt = login_getcapstr(lc, "passwd_prompt", NULL, NULL);
        retval = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, prompt);
        login_close(lc);
        if (retval != PAM_SUCCESS)
                return (retval);
        PAM_LOG("Got password");
        if (strnlen(pass, _PASSWORD_LEN + 1) > _PASSWORD_LEN) {
                PAM_LOG("Password is too long, using fake password");
                realpw = "*";
        }
        if (strcmp(crypt(pass, realpw), realpw) == 0)
                return (PAM_SUCCESS);

        PAM_VERBOSE_ERROR("UNIX authentication refused");
        return (PAM_AUTH_ERR);
}

PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
    int argc __unused, const char *argv[] __unused)
{

        return (PAM_SUCCESS);
}

/*
 * account management
 */
PAM_EXTERN int
pam_sm_acct_mgmt(pam_handle_t *pamh, int flags __unused,
    int argc __unused, const char *argv[] __unused)
{
        struct addrinfo hints, *res;
        struct passwd *pwd;
        struct timeval tp;
        login_cap_t *lc;
        time_t warntime;
        int retval;
        const char *user;
        const void *rhost, *tty;
        char rhostip[MAXHOSTNAMELEN] = "";

        retval = pam_get_user(pamh, &user, NULL);
        if (retval != PAM_SUCCESS)
                return (retval);

        if (user == NULL || (pwd = getpwnam(user)) == NULL)
                return (PAM_SERVICE_ERR);

        PAM_LOG("Got user: %s", user);

        retval = pam_get_item(pamh, PAM_RHOST, &rhost);
        if (retval != PAM_SUCCESS)
                return (retval);

        retval = pam_get_item(pamh, PAM_TTY, &tty);
        if (retval != PAM_SUCCESS)
                return (retval);

        if (*pwd->pw_passwd == '\0' &&
            (flags & PAM_DISALLOW_NULL_AUTHTOK) != 0)
                return (PAM_NEW_AUTHTOK_REQD);

        if (strncmp(pwd->pw_passwd, LOCKED_PREFIX, LOCKED_PREFIX_LEN) == 0)
                return (PAM_AUTH_ERR);

        lc = login_getpwclass(pwd);
        if (lc == NULL) {
                PAM_LOG("Unable to get login class for user %s", user);
                return (PAM_SERVICE_ERR);
        }

        PAM_LOG("Got login_cap");

        if (pwd->pw_change || pwd->pw_expire)
                gettimeofday(&tp, NULL);

        /*
         * Check pw_expire before pw_change - no point in letting the
         * user change the password on an expired account.
         */

        if (pwd->pw_expire) {
                warntime = login_getcaptime(lc, "warnexpire",
                    DEFAULT_WARN, DEFAULT_WARN);
                if (tp.tv_sec >= pwd->pw_expire) {
                        login_close(lc);
                        return (PAM_ACCT_EXPIRED);
                } else if (pwd->pw_expire - tp.tv_sec < warntime &&
                    (flags & PAM_SILENT) == 0) {
                        pam_error(pamh, "Warning: your account expires on %s",
                            ctime(&pwd->pw_expire));
                }
        }

        retval = PAM_SUCCESS;
        if (pwd->pw_change) {
                warntime = login_getcaptime(lc, "warnpassword",
                    DEFAULT_WARN, DEFAULT_WARN);
                if (tp.tv_sec >= pwd->pw_change) {
                        retval = PAM_NEW_AUTHTOK_REQD;
                } else if (pwd->pw_change - tp.tv_sec < warntime &&
                    (flags & PAM_SILENT) == 0) {
                        pam_error(pamh, "Warning: your password expires on %s",
                            ctime(&pwd->pw_change));
                }
        }

        /*
         * From here on, we must leave retval untouched (unless we
         * know we're going to fail), because we need to remember
         * whether we're supposed to return PAM_SUCCESS or
         * PAM_NEW_AUTHTOK_REQD.
         */

        if (rhost && *(const char *)rhost != '\0') {
                memset(&hints, 0, sizeof(hints));
                hints.ai_family = AF_UNSPEC;
                if (getaddrinfo(rhost, NULL, &hints, &res) == 0) {
                        getnameinfo(res->ai_addr, res->ai_addrlen,
                            rhostip, sizeof(rhostip), NULL, 0,
                            NI_NUMERICHOST);
                }
                if (res != NULL)
                        freeaddrinfo(res);
        }

        /*
         * Check host / tty / time-of-day restrictions
         */

        if (!auth_hostok(lc, rhost, rhostip) ||
            !auth_ttyok(lc, tty) ||
            !auth_timeok(lc, time(NULL)))
                retval = PAM_AUTH_ERR;

        login_close(lc);

        return (retval);
}

/*
 * password management
 *
 * standard Unix and NIS password changing
 */
PAM_EXTERN int
pam_sm_chauthtok(pam_handle_t *pamh, int flags,
    int argc __unused, const char *argv[] __unused)
{
#ifdef YP
        struct ypclnt *ypclnt;
        const void *yp_domain, *yp_server;
#endif
        char salt[SALTSIZE + 1];
        login_cap_t *lc;
        struct passwd *pwd, *old_pwd;
        const char *user, *old_pass, *new_pass;
        char *encrypted;
        time_t passwordtime;
        int pfd, tfd, retval;

        if (openpam_get_option(pamh, PAM_OPT_AUTH_AS_SELF))
                user = getlogin();
        else {
                retval = pam_get_user(pamh, &user, NULL);
                if (retval != PAM_SUCCESS)
                        return (retval);
        }
        pwd = getpwnam(user);

        if (pwd == NULL)
                return (PAM_AUTHTOK_RECOVERY_ERR);

        PAM_LOG("Got user: %s", user);

        if (flags & PAM_PRELIM_CHECK) {

                PAM_LOG("PRELIM round");

                if (getuid() == 0 &&
                    (pwd->pw_fields & _PWF_SOURCE) == _PWF_FILES)
                        /* root doesn't need the old password */
                        return (pam_set_item(pamh, PAM_OLDAUTHTOK, ""));
#ifdef YP
                if (getuid() == 0 &&
                    (pwd->pw_fields & _PWF_SOURCE) == _PWF_NIS) {

                        yp_domain = yp_server = NULL;
                        (void)pam_get_data(pamh, "yp_domain", &yp_domain);
                        (void)pam_get_data(pamh, "yp_server", &yp_server);

                        ypclnt = ypclnt_new(yp_domain, "passwd.byname", yp_server);
                        if (ypclnt == NULL)
                                return (PAM_BUF_ERR);

                        if (ypclnt_connect(ypclnt) == -1) {
                                ypclnt_free(ypclnt);
                                return (PAM_SERVICE_ERR);
                        }

                        retval = ypclnt_havepasswdd(ypclnt);
                        ypclnt_free(ypclnt);
                        if (retval == 1)
                                return (pam_set_item(pamh, PAM_OLDAUTHTOK, ""));
                        else if (retval == -1)
                                return (PAM_SERVICE_ERR);
                }
#endif
                if (pwd->pw_passwd[0] == '\0'
                    && openpam_get_option(pamh, PAM_OPT_NULLOK)) {
                        /*
                         * No password case. XXX Are we giving too much away
                         * by not prompting for a password?
                         * XXX check PAM_DISALLOW_NULL_AUTHTOK
                         */
                        old_pass = "";
                        retval = PAM_SUCCESS;
                } else {
                        retval = pam_get_authtok(pamh,
                            PAM_OLDAUTHTOK, &old_pass, NULL);
                        if (retval != PAM_SUCCESS)
                                return (retval);
                }
                PAM_LOG("Got old password");
                /* always encrypt first */
                encrypted = crypt(old_pass, pwd->pw_passwd);
                if (old_pass[0] == '\0' &&
                    !openpam_get_option(pamh, PAM_OPT_NULLOK))
                        return (PAM_PERM_DENIED);
                if (strcmp(encrypted, pwd->pw_passwd) != 0)
                        return (PAM_PERM_DENIED);
        }
        else if (flags & PAM_UPDATE_AUTHTOK) {
                PAM_LOG("UPDATE round");

                retval = pam_get_authtok(pamh,
                    PAM_OLDAUTHTOK, &old_pass, NULL);
                if (retval != PAM_SUCCESS)
                        return (retval);
                PAM_LOG("Got old password");

                /* get new password */
                for (;;) {
                        retval = pam_get_authtok(pamh,
                            PAM_AUTHTOK, &new_pass, NULL);
                        if (retval != PAM_TRY_AGAIN)
                                break;
                        pam_error(pamh, "Mismatch; try again, EOF to quit.");
                }
                PAM_LOG("Got new password");
                if (retval != PAM_SUCCESS) {
                        PAM_VERBOSE_ERROR("Unable to get new password");
                        return (retval);
                }

                if (getuid() != 0 && new_pass[0] == '\0' &&
                    !openpam_get_option(pamh, PAM_OPT_NULLOK))
                        return (PAM_PERM_DENIED);

                if ((old_pwd = pw_dup(pwd)) == NULL)
                        return (PAM_BUF_ERR);

                lc = login_getclass(pwd->pw_class);
                if (login_setcryptfmt(lc, password_hash, NULL) == NULL)
                        openpam_log(PAM_LOG_ERROR,
                            "can't set password cipher, relying on default");
                
                /* set password expiry date */
                pwd->pw_change = 0;
                passwordtime = login_getcaptime(lc, "passwordtime", 0, 0);
                if (passwordtime > 0)
                        pwd->pw_change = time(NULL) + passwordtime;
                
                login_close(lc);
                makesalt(salt);
                pwd->pw_passwd = crypt(new_pass, salt);
#ifdef YP
                switch (old_pwd->pw_fields & _PWF_SOURCE) {
                case _PWF_FILES:
#endif
                        retval = PAM_SERVICE_ERR;
                        if (pw_init(NULL, NULL))
                                openpam_log(PAM_LOG_ERROR, "pw_init() failed");
                        else if ((pfd = pw_lock()) == -1)
                                openpam_log(PAM_LOG_ERROR, "pw_lock() failed");
                        else if ((tfd = pw_tmp(-1)) == -1)
                                openpam_log(PAM_LOG_ERROR, "pw_tmp() failed");
                        else if (pw_copy(pfd, tfd, pwd, old_pwd) == -1)
                                openpam_log(PAM_LOG_ERROR, "pw_copy() failed");
                        else if (pw_mkdb(pwd->pw_name) == -1)
                                openpam_log(PAM_LOG_ERROR, "pw_mkdb() failed");
                        else
                                retval = PAM_SUCCESS;
                        pw_fini();
#ifdef YP
                        break;
                case _PWF_NIS:
                        yp_domain = yp_server = NULL;
                        (void)pam_get_data(pamh, "yp_domain", &yp_domain);
                        (void)pam_get_data(pamh, "yp_server", &yp_server);
                        ypclnt = ypclnt_new(yp_domain,
                            "passwd.byname", yp_server);
                        if (ypclnt == NULL) {
                                retval = PAM_BUF_ERR;
                        } else if (ypclnt_connect(ypclnt) == -1 ||
                            ypclnt_passwd(ypclnt, pwd, old_pass) == -1) {
                                openpam_log(PAM_LOG_ERROR, "%s", ypclnt->error);
                                retval = PAM_SERVICE_ERR;
                        } else {
                                retval = PAM_SUCCESS;
                        }
                        ypclnt_free(ypclnt);
                        break;
                default:
                        openpam_log(PAM_LOG_ERROR, "unsupported source 0x%x",
                            pwd->pw_fields & _PWF_SOURCE);
                        retval = PAM_SERVICE_ERR;
                }
#endif
                free(old_pwd);
        }
        else {
                /* Very bad juju */
                retval = PAM_ABORT;
                PAM_LOG("Illegal 'flags'");
        }

        return (retval);
}

/* Mostly stolen from passwd(1)'s local_passwd.c - markm */

static unsigned char itoa64[] =         /* 0 ... 63 => ascii - 64 */
        "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static void
to64(char *s, long v, int n)
{
        while (--n >= 0) {
                *s++ = itoa64[v&0x3f];
                v >>= 6;
        }
}

/* Salt suitable for traditional DES and MD5 */
static void
makesalt(char salt[SALTSIZE + 1])
{
        int i;

        /* These are not really random numbers, they are just
         * numbers that change to thwart construction of a
         * dictionary.
         */
        for (i = 0; i < SALTSIZE; i += 4)
                to64(&salt[i], arc4random(), 4);
        salt[SALTSIZE] = '\0';
}

PAM_MODULE_ENTRY("pam_unix");