/*-
 * 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.
 * Copyright (c) 2015-2018 The University of Oslo
 * 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 <sys/socket.h>
#include <netdb.h>
#include <pwd.h>
#include <radlib.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.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"
#define PAM_OPT_NAS_ID          "nas_id"
#define PAM_OPT_NAS_IPADDR      "nas_ipaddr"
#define PAM_OPT_NO_REPLYMSG     "no_reply_message"

#define MAX_CHALLENGE_MSGS      10
#define PASSWORD_PROMPT         "RADIUS Password:"

static int       build_access_request(struct rad_handle *, const char *,
                    const char *, const char *, const char *, const char *,
                    const void *, size_t);
static int       do_accept(pam_handle_t *, struct rad_handle *);
static int       do_challenge(pam_handle_t *, struct rad_handle *,
                    const char *, const char *, const char *, const char *);

/*
 * Construct an access request, but don't send it.  Returns 0 on success,
 * -1 on failure.
 */
static int
build_access_request(struct rad_handle *radh, const char *user,
    const char *pass, const char *nas_id, const char *nas_ipaddr,
    const char *rhost, const void *state, size_t state_len)
{
        int error;
        char host[MAXHOSTNAMELEN];
        struct sockaddr_in *haddr;
        struct addrinfo hints;
        struct addrinfo *res;

        if (rad_create_request(radh, RAD_ACCESS_REQUEST) == -1) {
                syslog(LOG_CRIT, "rad_create_request: %s", rad_strerror(radh));
                return (-1);
        }
        if (nas_id == NULL ||
            (nas_ipaddr != NULL && strlen(nas_ipaddr) == 0)) {
                if (gethostname(host, sizeof host) != -1) {
                        if (nas_id == NULL)
                                nas_id = host;
                        if (nas_ipaddr != NULL && strlen(nas_ipaddr) == 0)
                                nas_ipaddr = host;
                }
        }
        if ((user != NULL &&
            rad_put_string(radh, RAD_USER_NAME, user) == -1) ||
            (pass != NULL &&
            rad_put_string(radh, RAD_USER_PASSWORD, pass) == -1) ||
            (nas_id != NULL &&
            rad_put_string(radh, RAD_NAS_IDENTIFIER, nas_id) == -1)) {
                syslog(LOG_CRIT, "rad_put_string: %s", rad_strerror(radh));
                return (-1);
        }
        if (nas_ipaddr != NULL) {
                memset(&hints, 0, sizeof(hints));
                hints.ai_family = AF_INET;
                if (getaddrinfo(nas_ipaddr, NULL, &hints, &res) == 0 &&
                    res != NULL && res->ai_family == AF_INET) {
                        haddr = (struct sockaddr_in *)res->ai_addr;
                        error = rad_put_addr(radh, RAD_NAS_IP_ADDRESS,
                            haddr->sin_addr);
                        freeaddrinfo(res);
                        if (error == -1) {
                                syslog(LOG_CRIT, "rad_put_addr: %s",
                                    rad_strerror(radh));
                                return (-1);
                        }
                }
        }
        if (rhost != NULL &&
            rad_put_string(radh, RAD_CALLING_STATION_ID, rhost) == -1) {
                syslog(LOG_CRIT, "rad_put_string: %s", rad_strerror(radh));
                return (-1);
        }
        if (state != NULL &&
            rad_put_attr(radh, RAD_STATE, state, state_len) == -1) {
                syslog(LOG_CRIT, "rad_put_attr: %s", rad_strerror(radh));
                return (-1);
        }
        if (rad_put_int(radh, RAD_SERVICE_TYPE, RAD_AUTHENTICATE_ONLY) == -1) {
                syslog(LOG_CRIT, "rad_put_int: %s", rad_strerror(radh));
                return (-1);
        }
        return (0);
}

static int
do_accept(pam_handle_t *pamh, struct rad_handle *radh)
{
        int attrtype;
        const void *attrval;
        size_t attrlen;
        char *s;

        while ((attrtype = rad_get_attr(radh, &attrval, &attrlen)) > 0) {
                switch (attrtype) {
                case RAD_USER_NAME:
                        if ((s = rad_cvt_string(attrval, attrlen)) == NULL)
                                goto enomem;
                        pam_set_item(pamh, PAM_USER, s);
                        free(s);
                        break;
                case RAD_REPLY_MESSAGE:
                        if ((s = rad_cvt_string(attrval, attrlen)) == NULL)
                                goto enomem;
                        if (!openpam_get_option(pamh, PAM_OPT_NO_REPLYMSG))
                                pam_info(pamh, "%s", s);
                        free(s);
                        break;
                default:
                        PAM_LOG("%s(): ignoring RADIUS attribute %d",
                            __func__, attrtype);
                }
        }
        if (attrtype == -1) {
                syslog(LOG_CRIT, "rad_get_attr: %s", rad_strerror(radh));
                return (-1);
        }
        return (0);
enomem:
        syslog(LOG_CRIT, "%s(): out of memory", __func__);
        return (-1);
}

static int
do_reject(pam_handle_t *pamh, struct rad_handle *radh)
{
        int attrtype;
        const void *attrval;
        size_t attrlen;
        char *s;

        while ((attrtype = rad_get_attr(radh, &attrval, &attrlen)) > 0) {
                switch (attrtype) {
                case RAD_REPLY_MESSAGE:
                        if ((s = rad_cvt_string(attrval, attrlen)) == NULL)
                                goto enomem;
                        if (!openpam_get_option(pamh, PAM_OPT_NO_REPLYMSG))
                                pam_error(pamh, "%s", s);
                        free(s);
                        break;
                default:
                        PAM_LOG("%s(): ignoring RADIUS attribute %d",
                            __func__, attrtype);
                }
        }
        if (attrtype < 0) {
                syslog(LOG_CRIT, "rad_get_attr: %s", rad_strerror(radh));
                return (-1);
        }
        return (0);
enomem:
        syslog(LOG_CRIT, "%s(): out of memory", __func__);
        return (-1);
}

static int
do_challenge(pam_handle_t *pamh, struct rad_handle *radh, const char *user,
    const char *nas_id, const char *nas_ipaddr, const char *rhost)
{
        int retval;
        int attrtype;
        const void *attrval;
        size_t attrlen;
        const void *state;
        size_t statelen;
        struct pam_message msgs[MAX_CHALLENGE_MSGS];
        const struct pam_message *msg_ptrs[MAX_CHALLENGE_MSGS];
        struct pam_response *resp;
        int num_msgs;
        const void *item;
        const struct pam_conv *conv;

        state = NULL;
        statelen = 0;
        num_msgs = 0;
        while ((attrtype = rad_get_attr(radh, &attrval, &attrlen)) > 0) {
                switch (attrtype) {

                case RAD_STATE:
                        state = attrval;
                        statelen = attrlen;
                        break;

                case RAD_REPLY_MESSAGE:
                        if (num_msgs >= MAX_CHALLENGE_MSGS) {
                                syslog(LOG_CRIT,
                                    "Too many RADIUS challenge messages");
                                return (PAM_SERVICE_ERR);
                        }
                        msgs[num_msgs].msg = rad_cvt_string(attrval, attrlen);
                        if (msgs[num_msgs].msg == NULL) {
                                syslog(LOG_CRIT,
                                    "rad_cvt_string: out of memory");
                                return (PAM_SERVICE_ERR);
                        }
                        msgs[num_msgs].msg_style = PAM_TEXT_INFO;
                        msg_ptrs[num_msgs] = &msgs[num_msgs];
                        num_msgs++;
                        break;
                }
        }
        if (attrtype == -1) {
                syslog(LOG_CRIT, "rad_get_attr: %s", rad_strerror(radh));
                return (PAM_SERVICE_ERR);
        }
        if (num_msgs == 0) {
                msgs[num_msgs].msg = strdup("(null RADIUS challenge): ");
                if (msgs[num_msgs].msg == NULL) {
                        syslog(LOG_CRIT, "Out of memory");
                        return (PAM_SERVICE_ERR);
                }
                msgs[num_msgs].msg_style = PAM_TEXT_INFO;
                msg_ptrs[num_msgs] = &msgs[num_msgs];
                num_msgs++;
        }
        msgs[num_msgs-1].msg_style = PAM_PROMPT_ECHO_ON;
        if ((retval = pam_get_item(pamh, PAM_CONV, &item)) != PAM_SUCCESS) {
                syslog(LOG_CRIT, "do_challenge: cannot get PAM_CONV");
                return (retval);
        }
        conv = (const struct pam_conv *)item;
        if ((retval = conv->conv(num_msgs, msg_ptrs, &resp,
            conv->appdata_ptr)) != PAM_SUCCESS)
                return (retval);
        if (build_access_request(radh, user, resp[num_msgs-1].resp, nas_id,
            nas_ipaddr, rhost, state, statelen) == -1)
                return (PAM_SERVICE_ERR);
        memset(resp[num_msgs-1].resp, 0, strlen(resp[num_msgs-1].resp));
        free(resp[num_msgs-1].resp);
        free(resp);
        while (num_msgs > 0)
                free(msgs[--num_msgs].msg);
        return (PAM_SUCCESS);
}

PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
    int argc __unused, const char *argv[] __unused)
{
        struct rad_handle *radh;
        const char *user, *pass;
        const void *rhost, *tmpuser;
        const char *conf_file, *template_user, *nas_id, *nas_ipaddr;
        int retval;
        int e;

        conf_file = openpam_get_option(pamh, PAM_OPT_CONF);
        template_user = openpam_get_option(pamh, PAM_OPT_TEMPLATE_USER);
        nas_id = openpam_get_option(pamh, PAM_OPT_NAS_ID);
        nas_ipaddr = openpam_get_option(pamh, PAM_OPT_NAS_IPADDR);
        pam_get_item(pamh, PAM_RHOST, &rhost);

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

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

        retval = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, PASSWORD_PROMPT);
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Got password");

        radh = rad_open();
        if (radh == NULL) {
                syslog(LOG_CRIT, "rad_open failed");
                return (PAM_SERVICE_ERR);
        }

        PAM_LOG("Radius opened");

        if (rad_config(radh, conf_file) == -1) {
                syslog(LOG_ALERT, "rad_config: %s", rad_strerror(radh));
                rad_close(radh);
                return (PAM_SERVICE_ERR);
        }

        PAM_LOG("Radius config file read");

        if (build_access_request(radh, user, pass, nas_id, nas_ipaddr, rhost,
            NULL, 0) == -1) {
                rad_close(radh);
                return (PAM_SERVICE_ERR);
        }

        PAM_LOG("Radius build access done");

        for (;;) {
                switch (rad_send_request(radh)) {

                case RAD_ACCESS_ACCEPT:
                        e = do_accept(pamh, radh);
                        rad_close(radh);
                        if (e == -1)
                                return (PAM_SERVICE_ERR);
                        if (template_user != NULL) {

                                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, &tmpuser);
                                if (retval != PAM_SUCCESS)
                                        return (retval);
                                if (getpwnam(tmpuser) == NULL) {
                                        pam_set_item(pamh, PAM_USER,
                                            template_user);
                                        PAM_LOG("Using template user");
                                }

                        }
                        return (PAM_SUCCESS);

                case RAD_ACCESS_REJECT:
                        retval = do_reject(pamh, radh);
                        rad_close(radh);
                        PAM_VERBOSE_ERROR("Radius rejection");
                        return (PAM_AUTH_ERR);

                case RAD_ACCESS_CHALLENGE:
                        retval = do_challenge(pamh, radh, user, nas_id,
                            nas_ipaddr, rhost);
                        if (retval != PAM_SUCCESS) {
                                rad_close(radh);
                                return (retval);
                        }
                        break;

                case -1:
                        syslog(LOG_CRIT, "rad_send_request: %s",
                            rad_strerror(radh));
                        rad_close(radh);
                        PAM_VERBOSE_ERROR("Radius failure");
                        return (PAM_AUTHINFO_UNAVAIL);

                default:
                        syslog(LOG_CRIT,
                            "rad_send_request: unexpected return value");
                        rad_close(radh);
                        PAM_VERBOSE_ERROR("Radius error");
                        return (PAM_SERVICE_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);
}

PAM_MODULE_ENTRY("pam_radius");