// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <sys/wait.h>

#define DEBUG 0

#ifndef NGROUPS_MAX
#define NGROUPS_MAX 32
#endif

static const char usage[] =
"Usage: %s -u USER_ID [-g GRP_ID] [-v EUID] [-j EGID] [-G <GID0,GID1,...>] command\n"
"  -u USER_ID           switch to uid USER_ID\n"
"  -g GRP_ID            switch to gid GRP_ID\n"
"  -v EUID              switch euid to EUID\n"
"  -j EGID              switch egid to EGID\n"
"  -G <GID0,GID1,...>   set supplementary groups\n";

static void Usage_and_abort(const char *name)
{
	fprintf(stderr, usage, name);
	exit(-1);
}

int main(int argc, char **argv)
{
	char **my_argv, *name = argv[0], *grp;
	int status, c, i;
	int gid_is_set = 0, uid_is_set = 0, num_supp = -1;
	uid_t user_id = 0;
	gid_t grp_id = 0, supp_groups[NGROUPS_MAX] = { 0 };
	int euid_is_set = 0, egid_is_set = 0;
	uid_t euid = 0;
	gid_t egid = 0;

	if (argc == 1) {
		fprintf(stderr, "No parameter count\n");
		Usage_and_abort(name);
	}

	/* get UID and GID */
	while ((c = getopt(argc, argv, "+u:g:v:j:hG:")) != -1) {
		switch (c) {
		case 'u':
			if (!isdigit(optarg[0])) {
				struct passwd *pw = getpwnam(optarg);

				if (!pw) {
					fprintf(stderr, "parameter '%s' bad\n",
						optarg);
					Usage_and_abort(name);
				}
				user_id = pw->pw_uid;
			} else {
				user_id = (uid_t)atoi(optarg);
			}
			uid_is_set = 1;
			if (!gid_is_set)
				grp_id = user_id;
			break;

		case 'g':
			if (!isdigit(optarg[0])) {
				struct group *gr = getgrnam(optarg);

				if (!gr) {
					fprintf(stderr, "getgrname %s failed\n",
						optarg);
					Usage_and_abort(name);
				}
				grp_id = gr->gr_gid;
			} else {
				grp_id = (gid_t)atoi(optarg);
			}
			gid_is_set = 1;
			break;

		case 'v':
			if (!isdigit(optarg[0])) {
				struct passwd *pw = getpwnam(optarg);

				if (!pw) {
					fprintf(stderr, "parameter '%s' bad\n",
						optarg);
					Usage_and_abort(name);
				}
				euid = pw->pw_uid;
			} else {
				euid = (uid_t)atoi(optarg);
			}
			euid_is_set = 1;
			break;

		case 'j':
			if (!isdigit(optarg[0])) {
				struct group *gr = getgrnam(optarg);

				if (!gr) {
					fprintf(stderr, "getgrname %s failed\n",
						optarg);
					Usage_and_abort(name);
				}
				egid = gr->gr_gid;
			} else {
				egid = (gid_t)atoi(optarg);
			}
			egid_is_set = 1;
			break;

		case 'G':
			if (!optarg || !isdigit(optarg[0])) {
				fprintf(stderr,
					"Provided parameter '%s' for option '-G' is bad\n",
					optarg);
				Usage_and_abort(name);
				break;
			}
			num_supp = 0;
			while ((grp = strsep(&optarg, ",")) != NULL) {
				printf("adding supp group %d\n", atoi(grp));
				supp_groups[num_supp++] = atoi(grp);
				if (num_supp >= NGROUPS_MAX)
					break;
			}
			break;

		default:
		case 'h':
			Usage_and_abort(name);
			break;
		}
	}

	if (!uid_is_set) {
		fprintf(stderr, "Must specify uid to run.\n");
		Usage_and_abort(name);
	}

	if (optind == argc) {
		fprintf(stderr, "Must specify command to run.\n");
		Usage_and_abort(name);
	}

	/* assemble the command */
	my_argv = (char **)malloc(sizeof(char *) * (argc + 1 - optind));
	if (!my_argv) {
		fprintf(stderr, "Error in allocating memory. (%s)\n",
			strerror(errno));
		exit(-1);
	}

	for (i = optind; i < argc; i++)
		my_argv[i - optind] = argv[i];

	my_argv[i - optind] = NULL;

#if DEBUG
	system("whoami");
#endif

	/* set GID */
	if (!egid_is_set)
		egid = grp_id;
	status = setregid(grp_id, egid);
	if (status == -1) {
		fprintf(stderr, "Cannot change gid to %d/%d, errno=%d (%s)\n",
			grp_id, egid, errno, strerror(errno));
		exit(-1);
	}

	if (num_supp == -1) {
		/* at least one supp group needs to be provided,
		 * so take the gid
		 */
		num_supp = 1;
		supp_groups[0] = grp_id;
	}
	status = setgroups(num_supp, supp_groups);
	if (status == -1) {
		perror("setting supplementary groups");
		exit(-1);
	}

	/* set UID */
	if (!euid_is_set)
		euid = user_id;
	status = setreuid(user_id, euid);
	if (status == -1) {
		fprintf(stderr, "Cannot change uid to %d/%d, errno=%d (%s)\n",
			user_id, euid, errno, strerror(errno));
		exit(-1);
	}

	fprintf(stderr, "running as uid/gid/euid/egid %d/%d/%d/%d, groups:",
		user_id, grp_id, euid, egid);
	for (i = 0; i < num_supp; i++)
		fprintf(stderr, " %d", supp_groups[i]);
	fprintf(stderr, "\n");

	for (i = 0; i < argc - optind; i++)
		fprintf(stderr, " [%s]", my_argv[i]);

	fprintf(stderr, "\n");
	fflush(stderr);

	/* The command to be run */
	execvp(my_argv[0], my_argv);
	fprintf(stderr, "execvp fails running %s (%d): %s\n", my_argv[0],
		errno, strerror(errno));
	exit(-1);
}
