coreutils

// relogin.c, version 0.1.0

// OMKOV coreutils relogin

// Copyright (C) 2022, Jakob Wakeling

// MIT Licence

#include "util/error.h"

#include "util/optget.h"

#include <grp.h>

#include <pwd.h>

#include <sys/types.h>

#include <unistd.h>

#include <errno.h>

#include <stdarg.h>

#include <stdio.h>

#include <stdlib.h>

#include <stdnoreturn.h>

#include <string.h>

#define VERSION "0.1.0"

static struct lop lops[] = {

	{ "help",    ARG_NUL, 256 },

	{ "version", ARG_NUL, 257 },

	{ NULL, 0, 0 }

};

static inline int relogin(const char *user, char *av[]);

static void hlp(void);

static void ver(void);

int main(int ac, char *av[]) { A0 = av[0];

	struct opt opt = OPTGET_INIT; opt.str = ""; opt.lops = lops;

	for (int o; (o = optget(&opt, av, 1)) != -1;) switch (o) {

	case 256: { hlp(); return 0; }

	case 257: { ver(); return 0; }

	default: { return 1; }

	}

	if (opt.ind + 0 >= ac) { error(1, "missing user operand"); }

	if (opt.ind + 1 >= ac) { error(1, "missing command operand"); }

	if (relogin(av[1], &av[2])) { error(1, "%s: %s\n", av[1], serr()); }

	return 0;

}

static inline int relogin(const char *user, char *av[]) {

	struct passwd *pw;

	if ((pw = getpwnam(user)) == NULL) { error(1, "%s", serr()); }

	if (initgroups(pw->pw_name, pw->pw_gid) == -1) { error(1, "%s", serr()); }

	if (setgid(pw->pw_gid) == -1) { error(1, "%s", serr()); }

	if (setuid(pw->pw_uid) == -1) { error(1, "%s", serr()); }

	setenv("HOME", pw->pw_dir, 1); setenv("LOGNAME", pw->pw_name, 1);

	setenv("USER", pw->pw_name, 1); unsetenv("MAIL");

	unsetenv("DOAS_USER"); unsetenv("SUDO_UID"); unsetenv("SUDO_GID");

	unsetenv("SUDO_USER"); unsetenv("SUDO_COMMAND");

	if (execvp(av[0], &av[0]) == -1) { error(1, "%s", serr()); }

	return 0;

}

static void hlp(void) {

	puts("relogin - invoke a command as a specified user\n");

	puts("usage: relogin user command [argument...]\n");

	puts("options:");

	puts("  --help     Display help information");

	puts("  --version  Display version information");

}

static void ver() {

	puts("OMKOV coreutils relogin, version " VERSION);

	puts("Copyright (C) 2022, Jakob Wakeling");

	puts("MIT Licence (https://opensource.org/licenses/MIT)");

}