micro-utils/src/su.c

#include <pwd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <unistd.h>
#include <signal.h>
#include <termios.h>
#include "pw_check.h"
#include "unused.h"

#define ECHOFLAGS (ECHO | ECHOE | ECHOK | ECHONL)

static char *c_flag = NULL;
static char *s_flag = NULL;
static char p_flag;

static int hide_input(int fd, int flag) {
	struct termios term;
	if (tcgetattr(fd, &term) < 0)
		return 1;

	if (flag)
		term.c_lflag &= ~ECHOFLAGS;

	else
		term.c_lflag |= ECHOFLAGS;

	if (tcsetattr(fd, TCSAFLUSH, &term) < 0)
		return 1;

	return 0;
}

static void su(const struct passwd *pw) {
	char *shell = s_flag;
	if (s_flag == NULL)
		shell = (pw->pw_shell[0] == '\0') ? "/bin/sh" : pw->pw_shell;

	if (!p_flag) {
		setenv("HOME", pw->pw_dir, 1);
		setenv("SHELL", shell, 1);
		setenv("USER", pw->pw_name, 1);
		setenv("LOGNAME", pw->pw_name, 1);
		setenv("PATH", "/bin", 1);
	}

	if (c_flag)
		execlp(shell, shell, "-c", c_flag, NULL);

	else
		execlp(shell, shell, "-l", NULL);
}

static int password(const struct passwd *pw) {
	static char psswd[512];

	printf("Password: ");
	fflush(stdout);

	if (hide_input(STDIN_FILENO, 1)) {
		fprintf(stderr, "\nsu: %s\n", strerror(errno));
		return 1;
	}

	off_t ret = 0;
	if ((ret = read(STDIN_FILENO, psswd, sizeof(psswd))) <= 0) {
		fprintf(stderr, "\nsu: %s\n", strerror(errno));
		return 1;
	}

	putchar('\n');

	psswd[ret - 1] = '\0';
	if (pw_check("su", pw, psswd)) {
		memset(psswd, '\0', sizeof(psswd));
		return 1;
	}

	memset(psswd, '\0', sizeof(psswd));
	return 0;
}

static void endwin(int sig) {
	UNUSED(sig);

	hide_input(STDIN_FILENO, 0);
	exit(1);
}

int main(int argc, char **argv) {
	int opt;
	while ((opt = getopt(argc, argv, "c:s:p")) != -1) {
		switch (opt) {
			case 'c':
				c_flag = optarg;
				break;

			case 's':
				s_flag = optarg;
				break;

			case 'p':
				p_flag = 1;
				break;

			default:
				puts("su [cps] [user Default: root]\n\t-c CMD Command to pass to \'sh -c\'\n\t-s SHELL Shell to use instead of user's default\n\t-p Do not set new env");
				return 0;
		}
	}

	argc -= optind;
	argv += optind;

	char *user = "root";
	if (argv[0])
		user = argv[0];

	struct passwd *pw = getpwnam(user);
	if (!pw) {
		fprintf(stderr, "su: Incorrent username\n");
		return 1;
	}

	signal(SIGINT, endwin);

	if (getuid() != 0) {
		int ret = password(pw);
		hide_input(STDIN_FILENO, 0);

		if (ret)
			return 1;
	}

	/* Start */
	if (setgid(pw->pw_gid) < 0) {
		fprintf(stderr, "su: %s\n", strerror(errno));
		return 1;
	}

	if (setuid(pw->pw_uid) < 0) {
		fprintf(stderr, "su: %s\n", strerror(errno));
		return 1;
	}

	su(pw);
	return 0;
}