/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2001,2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * 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.
 *
 * $FreeBSD: head/lib/libpam/modules/pam_exec/pam_exec.c 315164 2017-03-12 17:41:51Z pfg $
 */

#include <sys/types.h>
#include <sys/wait.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

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

#define ENV_ITEM(n) { (n), #n }
static struct {
        int item;
        const char *name;
} env_items[] = {
        ENV_ITEM(PAM_SERVICE),
        ENV_ITEM(PAM_USER),
        ENV_ITEM(PAM_TTY),
        ENV_ITEM(PAM_RHOST),
        ENV_ITEM(PAM_RUSER),
};

struct pe_opts {
        int     return_prog_exit_status;
};

#define PAM_RV_COUNT 24

static int
parse_options(const char *func, int *argc, const char **argv[],
    struct pe_opts *options)
{
        int i;

        /*
         * Parse options:
         *   return_prog_exit_status:
         *     use the program exit status as the return code of pam_exec
         *   --:
         *     stop options parsing; what follows is the command to execute
         */
        options->return_prog_exit_status = 0;

        for (i = 0; i < *argc; ++i) {
                if (strcmp((*argv)[i], "return_prog_exit_status") == 0) {
                        openpam_log(PAM_LOG_DEBUG,
                            "%s: Option \"return_prog_exit_status\" enabled",
                            func);
                        options->return_prog_exit_status = 1;
                } else {
                        if (strcmp((*argv)[i], "--") == 0) {
                                (*argc)--;
                                (*argv)++;
                        }

                        break;
                }
        }

        (*argc) -= i;
        (*argv) += i;

        return (0);
}

static int
_pam_exec(pam_handle_t *pamh __unused,
    const char *func, int flags __unused, int argc, const char *argv[],
    struct pe_opts *options)
{
        int envlen, i, nitems, pam_err, status;
        int nitems_rv;
        char **envlist, **tmp, *envstr;
        volatile int childerr;
        pid_t pid;

        /*
         * XXX For additional credit, divert child's stdin/stdout/stderr
         * to the conversation function.
         */

        /* Check there's a program name left after parsing options. */
        if (argc < 1) {
                openpam_log(PAM_LOG_ERROR, "%s: No program specified: aborting",
                    func);
                return (PAM_SERVICE_ERR);
        }

        /*
         * Set up the child's environment list. It consists of the PAM
         * environment, plus a few hand-picked PAM items, the pam_sm_*
         * function name calling it and, if return_prog_exit_status is
         * set, the valid return codes numerical values.
         */
        envlist = pam_getenvlist(pamh);
        for (envlen = 0; envlist[envlen] != NULL; ++envlen)
                /* nothing */ ;
        nitems = sizeof(env_items) / sizeof(*env_items);
        /* Count PAM return values put in the environment. */
        nitems_rv = options->return_prog_exit_status ? PAM_RV_COUNT : 0;
        tmp = realloc(envlist, (envlen + nitems + 1 + nitems_rv + 1) *
            sizeof(*envlist));
        if (tmp == NULL) {
                openpam_free_envlist(envlist);
                return (PAM_BUF_ERR);
        }
        envlist = tmp;
        for (i = 0; i < nitems; ++i) {
                const void *item;

                pam_err = pam_get_item(pamh, env_items[i].item, &item);
                if (pam_err != PAM_SUCCESS || item == NULL)
                        continue;
                asprintf(&envstr, "%s=%s", env_items[i].name,
                    (const char *)item);
                if (envstr == NULL) {
                        openpam_free_envlist(envlist);
                        return (PAM_BUF_ERR);
                }
                envlist[envlen++] = envstr;
                envlist[envlen] = NULL;
        }

        /* Add the pam_sm_* function name to the environment. */
        asprintf(&envstr, "PAM_SM_FUNC=%s", func);
        if (envstr == NULL) {
                openpam_free_envlist(envlist);
                return (PAM_BUF_ERR);
        }
        envlist[envlen++] = envstr;

        /* Add the PAM return values to the environment. */
        if (options->return_prog_exit_status) {
#define ADD_PAM_RV_TO_ENV(name)                                         \
                asprintf(&envstr, #name "=%d", name);                   \
                if (envstr == NULL) {                                   \
                        openpam_free_envlist(envlist);                  \
                        return (PAM_BUF_ERR);                           \
                }                                                       \
                envlist[envlen++] = envstr
                /*
                 * CAUTION: When adding/removing an item in the list
                 * below, be sure to update the value of PAM_RV_COUNT.
                 */
                ADD_PAM_RV_TO_ENV(PAM_ABORT);
                ADD_PAM_RV_TO_ENV(PAM_ACCT_EXPIRED);
                ADD_PAM_RV_TO_ENV(PAM_AUTHINFO_UNAVAIL);
                ADD_PAM_RV_TO_ENV(PAM_AUTHTOK_DISABLE_AGING);
                ADD_PAM_RV_TO_ENV(PAM_AUTHTOK_ERR);
                ADD_PAM_RV_TO_ENV(PAM_AUTHTOK_LOCK_BUSY);
                ADD_PAM_RV_TO_ENV(PAM_AUTHTOK_RECOVERY_ERR);
                ADD_PAM_RV_TO_ENV(PAM_AUTH_ERR);
                ADD_PAM_RV_TO_ENV(PAM_BUF_ERR);
                ADD_PAM_RV_TO_ENV(PAM_CONV_ERR);
                ADD_PAM_RV_TO_ENV(PAM_CRED_ERR);
                ADD_PAM_RV_TO_ENV(PAM_CRED_EXPIRED);
                ADD_PAM_RV_TO_ENV(PAM_CRED_INSUFFICIENT);
                ADD_PAM_RV_TO_ENV(PAM_CRED_UNAVAIL);
                ADD_PAM_RV_TO_ENV(PAM_IGNORE);
                ADD_PAM_RV_TO_ENV(PAM_MAXTRIES);
                ADD_PAM_RV_TO_ENV(PAM_NEW_AUTHTOK_REQD);
                ADD_PAM_RV_TO_ENV(PAM_PERM_DENIED);
                ADD_PAM_RV_TO_ENV(PAM_SERVICE_ERR);
                ADD_PAM_RV_TO_ENV(PAM_SESSION_ERR);
                ADD_PAM_RV_TO_ENV(PAM_SUCCESS);
                ADD_PAM_RV_TO_ENV(PAM_SYSTEM_ERR);
                ADD_PAM_RV_TO_ENV(PAM_TRY_AGAIN);
                ADD_PAM_RV_TO_ENV(PAM_USER_UNKNOWN);
        }

        envlist[envlen] = NULL;

        /*
         * Fork and run the command.  By using vfork() instead of fork(),
         * we can distinguish between an execve() failure and a non-zero
         * exit status from the command.
         */
        childerr = 0;
        if ((pid = vfork()) == 0) {
                execve(argv[0], (char * const *)argv, (char * const *)envlist);
                childerr = errno;
                _exit(1);
        }
        openpam_free_envlist(envlist);
        if (pid == -1) {
                openpam_log(PAM_LOG_ERROR, "%s: vfork(): %m", func);
                return (PAM_SYSTEM_ERR);
        }
        while (waitpid(pid, &status, 0) == -1) {
                if (errno == EINTR)
                        continue;
                openpam_log(PAM_LOG_ERROR, "%s: waitpid(): %m", func);
                return (PAM_SYSTEM_ERR);
        }
        if (childerr != 0) {
                openpam_log(PAM_LOG_ERROR, "%s: execve(): %m", func);
                return (PAM_SYSTEM_ERR);
        }
        if (WIFSIGNALED(status)) {
                openpam_log(PAM_LOG_ERROR, "%s: %s caught signal %d%s",
                    func, argv[0], WTERMSIG(status),
                    WCOREDUMP(status) ? " (core dumped)" : "");
                return (PAM_SERVICE_ERR);
        }
        if (!WIFEXITED(status)) {
                openpam_log(PAM_LOG_ERROR, "%s: unknown status 0x%x",
                    func, status);
                return (PAM_SERVICE_ERR);
        }

        if (options->return_prog_exit_status) {
                openpam_log(PAM_LOG_DEBUG,
                    "%s: Use program exit status as return value: %d",
                    func, WEXITSTATUS(status));
                return (WEXITSTATUS(status));
        } else {
                return (WEXITSTATUS(status) == 0 ?
                    PAM_SUCCESS : PAM_PERM_DENIED);
        }
}

PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags,
    int argc, const char *argv[])
{
        int ret;
        struct pe_opts options;

        ret = parse_options(__func__, &argc, &argv, &options);
        if (ret != 0)
                return (PAM_SERVICE_ERR);

        ret = _pam_exec(pamh, __func__, flags, argc, argv, &options);

        /*
         * We must check that the program returned a valid code for this
         * function.
         */
        switch (ret) {
        case PAM_SUCCESS:
        case PAM_ABORT:
        case PAM_AUTHINFO_UNAVAIL:
        case PAM_AUTH_ERR:
        case PAM_BUF_ERR:
        case PAM_CONV_ERR:
        case PAM_CRED_INSUFFICIENT:
        case PAM_IGNORE:
        case PAM_MAXTRIES:
        case PAM_PERM_DENIED:
        case PAM_SERVICE_ERR:
        case PAM_SYSTEM_ERR:
        case PAM_USER_UNKNOWN:
                break;
        default:
                openpam_log(PAM_LOG_ERROR, "%s returned invalid code %d",
                    argv[0], ret);
                ret = PAM_SERVICE_ERR;
        }

        return (ret);
}

PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh, int flags,
    int argc, const char *argv[])
{
        int ret;
        struct pe_opts options;

        ret = parse_options(__func__, &argc, &argv, &options);
        if (ret != 0)
                return (PAM_SERVICE_ERR);

        ret = _pam_exec(pamh, __func__, flags, argc, argv, &options);

        /*
         * We must check that the program returned a valid code for this
         * function.
         */
        switch (ret) {
        case PAM_SUCCESS:
        case PAM_ABORT:
        case PAM_BUF_ERR:
        case PAM_CONV_ERR:
        case PAM_CRED_ERR:
        case PAM_CRED_EXPIRED:
        case PAM_CRED_UNAVAIL:
        case PAM_IGNORE:
        case PAM_PERM_DENIED:
        case PAM_SERVICE_ERR:
        case PAM_SYSTEM_ERR:
        case PAM_USER_UNKNOWN:
                break;
        default:
                openpam_log(PAM_LOG_ERROR, "%s returned invalid code %d",
                    argv[0], ret);
                ret = PAM_SERVICE_ERR;
        }

        return (ret);
}

PAM_EXTERN int
pam_sm_acct_mgmt(pam_handle_t *pamh, int flags,
    int argc, const char *argv[])
{
        int ret;
        struct pe_opts options;

        ret = parse_options(__func__, &argc, &argv, &options);
        if (ret != 0)
                return (PAM_SERVICE_ERR);

        ret = _pam_exec(pamh, __func__, flags, argc, argv, &options);

        /*
         * We must check that the program returned a valid code for this
         * function.
         */
        switch (ret) {
        case PAM_SUCCESS:
        case PAM_ABORT:
        case PAM_ACCT_EXPIRED:
        case PAM_AUTH_ERR:
        case PAM_BUF_ERR:
        case PAM_CONV_ERR:
        case PAM_IGNORE:
        case PAM_NEW_AUTHTOK_REQD:
        case PAM_PERM_DENIED:
        case PAM_SERVICE_ERR:
        case PAM_SYSTEM_ERR:
        case PAM_USER_UNKNOWN:
                break;
        default:
                openpam_log(PAM_LOG_ERROR, "%s returned invalid code %d",
                    argv[0], ret);
                ret = PAM_SERVICE_ERR;
        }

        return (ret);
}

PAM_EXTERN int
pam_sm_open_session(pam_handle_t *pamh, int flags,
    int argc, const char *argv[])
{
        int ret;
        struct pe_opts options;

        ret = parse_options(__func__, &argc, &argv, &options);
        if (ret != 0)
                return (PAM_SERVICE_ERR);

        ret = _pam_exec(pamh, __func__, flags, argc, argv, &options);

        /*
         * We must check that the program returned a valid code for this
         * function.
         */
        switch (ret) {
        case PAM_SUCCESS:
        case PAM_ABORT:
        case PAM_BUF_ERR:
        case PAM_CONV_ERR:
        case PAM_IGNORE:
        case PAM_PERM_DENIED:
        case PAM_SERVICE_ERR:
        case PAM_SESSION_ERR:
        case PAM_SYSTEM_ERR:
                break;
        default:
                openpam_log(PAM_LOG_ERROR, "%s returned invalid code %d",
                    argv[0], ret);
                ret = PAM_SERVICE_ERR;
        }

        return (ret);
}

PAM_EXTERN int
pam_sm_close_session(pam_handle_t *pamh, int flags,
    int argc, const char *argv[])
{
        int ret;
        struct pe_opts options;

        ret = parse_options(__func__, &argc, &argv, &options);
        if (ret != 0)
                return (PAM_SERVICE_ERR);

        ret = _pam_exec(pamh, __func__, flags, argc, argv, &options);

        /*
         * We must check that the program returned a valid code for this
         * function.
         */
        switch (ret) {
        case PAM_SUCCESS:
        case PAM_ABORT:
        case PAM_BUF_ERR:
        case PAM_CONV_ERR:
        case PAM_IGNORE:
        case PAM_PERM_DENIED:
        case PAM_SERVICE_ERR:
        case PAM_SESSION_ERR:
        case PAM_SYSTEM_ERR:
                break;
        default:
                openpam_log(PAM_LOG_ERROR, "%s returned invalid code %d",
                    argv[0], ret);
                ret = PAM_SERVICE_ERR;
        }

        return (ret);
}

PAM_EXTERN int
pam_sm_chauthtok(pam_handle_t *pamh, int flags,
    int argc, const char *argv[])
{
        int ret;
        struct pe_opts options;

        ret = parse_options(__func__, &argc, &argv, &options);
        if (ret != 0)
                return (PAM_SERVICE_ERR);

        ret = _pam_exec(pamh, __func__, flags, argc, argv, &options);

        /*
         * We must check that the program returned a valid code for this
         * function.
         */
        switch (ret) {
        case PAM_SUCCESS:
        case PAM_ABORT:
        case PAM_AUTHTOK_DISABLE_AGING:
        case PAM_AUTHTOK_ERR:
        case PAM_AUTHTOK_LOCK_BUSY:
        case PAM_AUTHTOK_RECOVERY_ERR:
        case PAM_BUF_ERR:
        case PAM_CONV_ERR:
        case PAM_IGNORE:
        case PAM_PERM_DENIED:
        case PAM_SERVICE_ERR:
        case PAM_SYSTEM_ERR:
        case PAM_TRY_AGAIN:
                break;
        default:
                openpam_log(PAM_LOG_ERROR, "%s returned invalid code %d",
                    argv[0], ret);
                ret = PAM_SERVICE_ERR;
        }

        return (ret);
}

PAM_MODULE_ENTRY("pam_exec");