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/*
* mulderd.c
*
* The truth is out there.
*
* I want to believe.
*
*
* Copyright 2012 Jason A. Donenfeld <Jason@zx2c4.com>.
*
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <pwd.h>
#include <getopt.h>
#include <fcntl.h>
#include <time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/prctl.h>
#include <sys/stat.h>
#include <sys/resource.h>
#include <netinet/in.h>
static char truth[] = "\033[32;1m\n\n"
" _,--=--._\n"
" ,' _ `.\n"
" - _(_)_o -\n"
" ____' /_ _/] `____\n"
" -=====::(+):::::::::::::::::(+)::=====-\n"
" (+).\"\"\"\"\"\"\"\"\"\"\"\"\",(+)\n"
" . ,\n"
" ` -=- '\n"
"\n\n\n"
" THE TRUTH IS OUT THERE\n\n\033[0m";
/*
* Drops us into a chroot, if possible, and drops privs.
*/
void drop_privileges()
{
struct passwd *user;
struct rlimit limit;
if (!geteuid()) {
user = getpwnam("nobody");
if (!user) {
perror("getpwnam");
exit(EXIT_FAILURE);
}
if (chroot("/var/empty")) {
perror("chroot");
exit(EXIT_FAILURE);
}
if (chdir("/")) {
perror("chdir");
exit(EXIT_FAILURE);
}
if (setresgid(user->pw_gid, user->pw_gid, user->pw_gid)) {
perror("setresgid");
exit(EXIT_FAILURE);
}
if (setgroups(1, &user->pw_gid)) {
perror("setgroups");
exit(EXIT_FAILURE);
}
if (setresuid(user->pw_uid, user->pw_uid, user->pw_uid)) {
perror("setresuid");
exit(EXIT_FAILURE);
}
}
limit.rlim_cur = limit.rlim_max = 0;
setrlimit(RLIMIT_CORE, &limit);
setrlimit(RLIMIT_NPROC, &limit);
if (!geteuid() || !getegid()) {
fprintf(stderr, "Mysteriously still running as root... Goodbye.\n");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
int listen_fd, connection_fd, flag;
struct sockaddr_in6 listen_addr;
struct sockaddr_storage connection_addr;
struct timeval timeout;
char ipaddr[INET6_ADDRSTRLEN];
struct in6_addr *v6;
time_t now;
socklen_t connection_addr_len;
pid_t child;
int daemonize = 0, option_index = 0, port = 17, connection_file = -1, option;
char *pid_file = 0, *connection_log = 0, *time_str;
FILE *pidfile;
static struct option long_options[] = {
{"daemonize", no_argument, NULL, 'd'},
{"foreground", no_argument, NULL, 'f'},
{"port", required_argument, NULL, 'p'},
{"pid-file", required_argument, NULL, 'P'},
{"log-file", required_argument, NULL, 'l'},
{"help", no_argument, NULL, 'h'},
{0, 0, 0, 0}
};
close(STDIN_FILENO);
while ((option = getopt_long(argc, argv, "dfP:l:p:h", long_options, &option_index)) != -1) {
switch (option) {
case 'd':
daemonize = 1;
break;
case 'f':
daemonize = 0;
break;
case 'p':
port = atoi(optarg);
break;
case 'l':
connection_log = optarg;
break;
case 'P':
pid_file = optarg;
break;
case 'h':
case '?':
default:
fprintf(stderr, "I Want to Believe by zx2c4\n\n");
fprintf(stderr, "Usage: %s [OPTION]...\n", argv[0]);
fprintf(stderr, " -d, --daemonize run as a background daemon\n");
fprintf(stderr, " -f, --foreground run in the foreground (default)\n");
fprintf(stderr, " -P FILE, --pid-file=FILE write pid of listener process to FILE\n");
fprintf(stderr, " -l FILE, --log-file=FILE write connection log to FILE instead of stdout/stderr\n");
fprintf(stderr, " -p PORT, --port=PORT listen on port PORT (default=17)\n");
fprintf(stderr, " -h, --help display this message\n");
return option == 'h' ? EXIT_SUCCESS : EXIT_FAILURE;
}
}
if (connection_log) {
connection_file = open(connection_log, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
if (connection_file < 0) {
perror("open");
return EXIT_FAILURE;
}
if (dup2(connection_file, STDOUT_FILENO) < 0) {
perror("dup2");
return EXIT_FAILURE;
}
if (dup2(connection_file, STDERR_FILENO) < 0) {
perror("dup2");
return EXIT_FAILURE;
}
close(connection_file);
setbuf(stdout, NULL);
setbuf(stderr, NULL);
}
listen_fd = socket(AF_INET6, SOCK_STREAM, 0);
if (listen_fd < 0) {
perror("socket");
return EXIT_FAILURE;
}
flag = 1;
setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag));
flag = 0;
setsockopt(listen_fd, IPPROTO_IPV6, IPV6_V6ONLY, &flag, sizeof(flag));
memset(&listen_addr, 0, sizeof(listen_addr));
listen_addr.sin6_family = AF_INET6;
listen_addr.sin6_addr = in6addr_any;
listen_addr.sin6_port = htons(port);
if (bind(listen_fd, (struct sockaddr *)&listen_addr, sizeof(listen_addr)) < 0) {
perror("bind");
return EXIT_FAILURE;
}
if (listen(listen_fd, 15) < 0) {
perror("listen");
return EXIT_FAILURE;
}
if (pid_file) {
pidfile = fopen(pid_file, "w");
if (!pidfile) {
perror("fopen");
return EXIT_FAILURE;
}
}
if (daemonize) {
if (daemon(0, 1) < 0) {
perror("daemon");
return EXIT_FAILURE;
}
if (connection_file == -1) {
close(STDERR_FILENO);
close(STDOUT_FILENO);
}
}
if (pid_file) {
if (fprintf(pidfile, "%d\n", getpid()) < 0) {
perror("fprintf");
return EXIT_FAILURE;
}
fclose(pidfile);
}
drop_privileges();
prctl(PR_SET_NAME, "truth beacon");
timeout.tv_sec = 1;
timeout.tv_usec = 0;
while ((connection_addr_len = sizeof(connection_addr)) &&
(connection_fd = accept(listen_fd, (struct sockaddr *)&connection_addr, &connection_addr_len)) >= 0) {
now = time(NULL);
if (connection_addr.ss_family == AF_INET6) {
v6 = &(((struct sockaddr_in6 *)&connection_addr)->sin6_addr);
if (v6->s6_addr32[0] == 0 && v6->s6_addr32[1] == 0 && v6->s6_addr16[4] == 0 && v6->s6_addr16[5] == 0xFFFF)
inet_ntop(AF_INET, &v6->s6_addr32[3], ipaddr, INET_ADDRSTRLEN);
else
inet_ntop(AF_INET6, v6, ipaddr, INET6_ADDRSTRLEN);
} else if (connection_addr.ss_family == AF_INET)
inet_ntop(AF_INET, &(((struct sockaddr_in *)&connection_addr)->sin_addr), ipaddr, INET_ADDRSTRLEN);
if (setsockopt(connection_fd, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout, sizeof(timeout)) < 0) {
close(connection_fd);
perror("setsockopt");
continue;
}
time_str = ctime(&now);
time_str[strlen(time_str) - 1] = 0;
printf("%s\t%s\t%d\n", time_str, ipaddr, ntohs(((struct sockaddr_in6 *)&connection_addr)->sin6_port));
if (write(connection_fd, truth, sizeof(truth)) < 0)
perror("write");
close(connection_fd);
}
close(listen_fd);
return 0;
}
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