main.c

/*
 * Copyright 2015-2018 Rivoreo
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 */

#include "common.h"
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <pwd.h>

static void print_usage(const char *name) {
	fprintf(stderr, "Usage: %s [-c <user-name>]\n", name);
}

int main(int argc, char **argv) {
	uid_t myuid = getuid();
	uid_t myeuid = geteuid();
	if(myeuid == 0) {
		fprintf(stderr, "%s: This program shouldn't be run under effective root\n", argv[0]);
		return 1;
	}
	if(myuid != myeuid) {
		fprintf(stderr, "%s: Real user ID (%u) does not equal to effective user ID (%u)\n",
			argv[0], myuid, myeuid);
		return 1;
	}

	struct passwd *mypw = getpwuid(myuid);
	if(!mypw) {
		perror("getpwuid");
		return 1;
	}

	const char *home = getenv("HOME");
	if(!home) {
		fprintf(stderr, "%s: HOME not set\n", argv[0]);
		return 1;
	}
	if(strcmp(home, mypw->pw_dir)) {
		fprintf(stderr, "%s: HOME=\"%s\" does not equal to \"%s\"\n", argv[0], home, mypw->pw_dir);
		return 1;
	}

	struct sockaddr_un sockaddr = { .sun_family = AF_UNIX };
	size_t home_len = strlen(home);
	if(home_len + 1 + sizeof SOCKET_NAME > sizeof sockaddr.sun_path) {
		fprintf(stderr, "home path too long (%zu bytes)\n", home_len);
		return 1;
	}
	memcpy(sockaddr.sun_path, home, home_len);
	sockaddr.sun_path[home_len] = '/';
	memcpy(sockaddr.sun_path + home_len + 1, SOCKET_NAME, sizeof SOCKET_NAME);

	if(chdir(home) < 0) {
		perror(home);
		return 1;
	}

	if(argc == 3 && strcmp(argv[1], "-c") == 0) return client_mode(&sockaddr, argv[2]);
	if(argc != 1) {
		print_usage(argv[0]);
		return 255;
	}
	return server_mode(&sockaddr);
}