/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright 1998 Juniper Networks, Inc.
 * All rights reserved.
 * Copyright (c) 2001-2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * Portions of this software were 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 <pwd.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <taclib.h>
#include <unistd.h>

#define PAM_SM_AUTH

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

#define PAM_OPT_CONF            "conf"
#define PAM_OPT_TEMPLATE_USER   "template_user"

typedef int (*set_func)(struct tac_handle *, const char *);

static int       do_item(pam_handle_t *, struct tac_handle *, int,
                    set_func, const char *);
static char     *get_msg(struct tac_handle *);
static int       set_msg(struct tac_handle *, const char *);

static int
do_item(pam_handle_t *pamh, struct tac_handle *tach, int item,
    set_func func, const char *funcname)
{
        int retval;
        const void *value;

        retval = pam_get_item(pamh, item, &value);
        if (retval != PAM_SUCCESS)
            return retval;
        if (value != NULL && (*func)(tach, (const char *)value) == -1) {
                syslog(LOG_CRIT, "%s: %s", funcname, tac_strerror(tach));
                tac_close(tach);
                return PAM_SERVICE_ERR;
        }
        return PAM_SUCCESS;
}

static char *
get_msg(struct tac_handle *tach)
{
        char *msg;

        msg = tac_get_msg(tach);
        if (msg == NULL) {
                syslog(LOG_CRIT, "tac_get_msg: %s", tac_strerror(tach));
                tac_close(tach);
                return NULL;
        }
        return msg;
}

static int
set_msg(struct tac_handle *tach, const char *msg)
{
        if (tac_set_msg(tach, msg) == -1) {
                syslog(LOG_CRIT, "tac_set_msg: %s", tac_strerror(tach));
                tac_close(tach);
                return -1;
        }
        return 0;
}

PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
    int argc __unused, const char *argv[] __unused)
{
        int retval;
        struct tac_handle *tach;
        const char *conf_file, *template_user;

        conf_file = openpam_get_option(pamh, PAM_OPT_CONF);
        template_user = openpam_get_option(pamh, PAM_OPT_TEMPLATE_USER);

        tach = tac_open();
        if (tach == NULL) {
                syslog(LOG_CRIT, "tac_open failed");
                return (PAM_SERVICE_ERR);
        }
        if (tac_config(tach, conf_file) == -1) {
                syslog(LOG_ALERT, "tac_config: %s", tac_strerror(tach));
                tac_close(tach);
                return (PAM_SERVICE_ERR);
        }
        if (tac_create_authen(tach, TAC_AUTHEN_LOGIN, TAC_AUTHEN_TYPE_ASCII,
            TAC_AUTHEN_SVC_LOGIN) == -1) {
                syslog(LOG_CRIT, "tac_create_authen: %s", tac_strerror(tach));
                tac_close(tach);
                return (PAM_SERVICE_ERR);
        }

        PAM_LOG("Done tac_open() ... tac_close()");

        retval = do_item(pamh, tach, PAM_USER, tac_set_user, "tac_set_user");
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Done user");

        retval = do_item(pamh, tach, PAM_TTY, tac_set_port, "tac_set_port");
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Done tty");

        retval = do_item(pamh, tach, PAM_RHOST, tac_set_rem_addr,
            "tac_set_rem_addr");
        if (retval != PAM_SUCCESS)
                return (retval);

        for (;;) {
                char *srvr_msg;
                size_t msg_len;
                const char *user_msg;
                char *data_msg;
                int sflags;
                int status;

                sflags = tac_send_authen(tach);
                if (sflags == -1) {
                        syslog(LOG_CRIT, "tac_send_authen: %s",
                            tac_strerror(tach));
                        tac_close(tach);
                        return (PAM_AUTHINFO_UNAVAIL);
                }
                status = TAC_AUTHEN_STATUS(sflags);
                openpam_set_option(pamh, PAM_OPT_ECHO_PASS,
                    TAC_AUTHEN_NOECHO(sflags) ? NULL : "");
                switch (status) {

                case TAC_AUTHEN_STATUS_PASS:
                        tac_close(tach);
                        if (template_user != NULL) {
                                const void *item;
                                const char *user;

                                PAM_LOG("Trying template user: %s",
                                    template_user);

                                /*
                                 * If the given user name doesn't exist in
                                 * the local password database, change it
                                 * to the value given in the "template_user"
                                 * option.
                                 */
                                retval = pam_get_item(pamh, PAM_USER, &item);
                                if (retval != PAM_SUCCESS)
                                        return (retval);
                                user = (const char *)item;
                                if (getpwnam(user) == NULL) {
                                        pam_set_item(pamh, PAM_USER,
                                            template_user);
                                        PAM_LOG("Using template user");
                                }
                        }
                        return (PAM_SUCCESS);

                case TAC_AUTHEN_STATUS_FAIL:
                        tac_close(tach);
                        PAM_VERBOSE_ERROR("TACACS+ authentication failed");
                        return (PAM_AUTH_ERR);

                case TAC_AUTHEN_STATUS_GETUSER:
                case TAC_AUTHEN_STATUS_GETPASS:
                        if ((srvr_msg = get_msg(tach)) == NULL)
                                return (PAM_SERVICE_ERR);
                        if (status == TAC_AUTHEN_STATUS_GETUSER)
                                retval = pam_get_user(pamh, &user_msg,
                                    *srvr_msg ? srvr_msg : NULL);
                        else if (status == TAC_AUTHEN_STATUS_GETPASS)
                                retval = pam_get_authtok(pamh,
                                    PAM_AUTHTOK, &user_msg,
                                    *srvr_msg ? srvr_msg : "Password:");
                        free(srvr_msg);
                        if (retval != PAM_SUCCESS) {
                                /* XXX - send a TACACS+ abort packet */
                                tac_close(tach);
                                return (retval);
                        }
                        if (set_msg(tach, user_msg) == -1)
                                return (PAM_SERVICE_ERR);
                        break;

                case TAC_AUTHEN_STATUS_GETDATA:
                        if ((srvr_msg = get_msg(tach)) == NULL)
                                return (PAM_SERVICE_ERR);
                        retval = pam_prompt(pamh,
                            openpam_get_option(pamh, PAM_OPT_ECHO_PASS) ?
                            PAM_PROMPT_ECHO_ON : PAM_PROMPT_ECHO_OFF,
                            &data_msg, "%s", *srvr_msg ? srvr_msg : "Data:");
                        free(srvr_msg);
                        if (retval != PAM_SUCCESS) {
                                /* XXX - send a TACACS+ abort packet */
                                tac_close(tach);
                                return (retval);
                        }
                        retval = set_msg(tach, data_msg);
                        memset(data_msg, 0, strlen(data_msg));
                        free(data_msg);
                        if (retval == -1)
                                return (PAM_SERVICE_ERR);
                        break;

                case TAC_AUTHEN_STATUS_ERROR:
                        srvr_msg = (char *)tac_get_data(tach, &msg_len);
                        if (srvr_msg != NULL && msg_len != 0) {
                                syslog(LOG_CRIT, "tac_send_authen:"
                                    " server detected error: %s", srvr_msg);
                                free(srvr_msg);
                        }
                        else
                                syslog(LOG_CRIT,
                                    "tac_send_authen: server detected error");
                        tac_close(tach);
                        return (PAM_AUTHINFO_UNAVAIL);
                        break;

                case TAC_AUTHEN_STATUS_RESTART:
                case TAC_AUTHEN_STATUS_FOLLOW:
                default:
                        syslog(LOG_CRIT,
                            "tac_send_authen: unexpected status %#x", status);
                        tac_close(tach);
                        return (PAM_AUTHINFO_UNAVAIL);
                }
        }
}

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

        return (PAM_IGNORE);
}

PAM_MODULE_ENTRY("pam_tacplus");