/*
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2019-2023, Juniper Networks, Inc.
 * 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 <sys/types.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/mac.h>

#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <syslog.h>

#include <security/mac_grantbylabel/mac_grantbylabel.h>

#include "libveriexec.h"

static char *
find_interpreter(const char *script)
{
        static const char ws[] = " \t\n\r";
        static char buf[MAXPATHLEN+4];  /* allow space for #! etc */
        char *cp;
        int fd;
        int n;

        cp = NULL;
        if ((fd = open(script, O_RDONLY)) >= 0) {
                if ((n = read(fd, buf, sizeof(buf))) > 0) {
                        if (strncmp(buf, "#!", 2) == 0) {
                                buf[sizeof(buf) - 1] = '\0';
                                cp = &buf[2];
                                if ((n = strspn(cp, ws)) > 0)
                                        cp += n;
                                if ((n = strcspn(cp, ws)) > 0) {
                                        cp[n] = '\0';
                                } else {
                                        cp = NULL;
                                }
                        }
                }
                close(fd);
        }
        return (cp);
}

/**
 * @brief exec a python or similar script
 *
 * Python and similar scripts must normally be signed and
 * run directly rather than fed to the interpreter which
 * is not normally allowed to be run directly.
 *
 * If direct execv of script fails due to EAUTH
 * and process has GBL_VERIEXEC syslog event and run via
 * interpreter.
 *
 * If interpreter is NULL look at first block of script
 * to find ``#!`` magic.
 *
 * @prarm[in] interpreter
 *      if NULL, extract from script if necessary
 *
 * @prarm[in] argv
 *      argv for execv(2)
 *      argv[0] must be full path.
 *      Python at least requires argv[1] to also be the script path.
 *
 * @return
 * error on failure usually EPERM or EAUTH
 */
int
execv_script(const char *interpreter, char * const *argv)
{
        const char *script;
        int rc;

        script = argv[0];
        if (veriexec_check_path(script) == 0) {
                rc = execv(script, argv);
        }
        /* still here? we might be allowed to run via interpreter */
        if (gbl_check_pid(0) & GBL_VERIEXEC) {
                if (!interpreter)
                        interpreter = find_interpreter(script);
                if (interpreter) {
                        syslog(LOG_NOTICE, "running %s via %s",
                            script, interpreter);
                        rc = execv(interpreter, argv);
                }
        }
        return (rc);
}

#if defined(MAIN) || defined(UNIT_TEST)
#include <sys/wait.h>
#include <err.h>

int
main(int argc __unused, char *argv[])
{
        const char *interp;
        int c;
        int s;
        pid_t child;

        openlog("exec_script", LOG_PID|LOG_PERROR, LOG_DAEMON);

        interp = NULL;
        while ((c = getopt(argc, argv, "i:")) != -1) {
                switch (c) {
                case 'i':
                        interp = optarg;
                        break;
                default:
                        errx(1, "unknown option: -%c", c);
                        break;
                }
        }
        argc -= optind;
        argv += optind;
        /* we need a child */
        child = fork();
        if (child < 0)
                err(2, "fork");
        if (child == 0) {
                c = execv_script(interp, argv);
                err(2, "exec_script(%s,%s)", interp, argv[0]);
        }
        c = waitpid(child, &s, 0);
        printf("%s: exit %d\n", argv[0], WEXITSTATUS(s));
        return (0);
}
#endif