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#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <syslog.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#include <pthread.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <errno.h>
#include <signal.h>
#include "packet.h"
#include "netascii.h"
static int stop = 0;
void stop_handler() {
stop = 1;
return;
}
void usage(char *name) {
printf("USAGE: %s -d -u nobody -g nobody -a 127.0.0.1 -p 69\n", name);
printf("\td: daemonize.\n");
printf("\tu: username to run as (default: nobody). Must be specified after -d.\n");
printf("\tg: group to run as (default: nobody). Must be specified after -d.\n");
printf("\ta: address to bind to (default: 127.0.0.1)\n");
printf("\tp: port to bind to (default: 69)\n");
}
int main(int argc, char **argv) {
int daemonize = 0;
char addr[16], user[32], group[32];
memset(addr, '\0', sizeof(addr));
memset(user, '\0', sizeof(user));
memset(group, '\0', sizeof(group));
strcpy(addr, "127.0.0.1");
strcpy(user, "nobody");
strcpy(group, "nobody");
int port = 69;
int ch = 0;
while ((ch = getopt(argc, argv, "da:p:u:g:h")) != -1) {
switch (ch) {
case 'a':
//TODO: this is unsafe
strcpy(addr, optarg);
break;
case 'p':
port = atoi(optarg);
if ((port <= 0) || (port >= 65536)) {
fprintf(stderr, "invalid port specified.\n");
return -1;
}
break;
case 'd':
daemonize = 1;
break;
case 'g':
if (daemonize) {
//TODO: this is unsafe
strcpy(group, optarg);
} else {
fprintf(stderr, "-g requires -d\n");
return -1;
}
break;
case 'u':
if (daemonize) {
//TODO: this is unsafe
strcpy(user, optarg);
} else {
fprintf(stderr, "-u requires -d\n");
return -1;
}
break;
case 'h': case '?':
usage(argv[0]);
return -1;
}
}
setlogmask(LOG_UPTO(LOG_INFO));
openlog(argv[0], LOG_PID | LOG_PERROR | LOG_NDELAY, LOG_FTP);
syslog(LOG_INFO, "starting up...");
if (daemonize) {
if (daemon(1, 0)) {
syslog(LOG_ERR, "failed to daemonize as requested!");
return -1;
} else {
syslog(LOG_INFO, "daemonized");
}
}
int s = socket(AF_INET, SOCK_DGRAM, 0);
if (s <= 0) {
syslog(LOG_ERR, "unable to bind socket!");
return -1;
}
struct sockaddr_in saddr;
saddr.sin_family = AF_INET;
saddr.sin_port = htons(port);
saddr.sin_addr.s_addr = inet_addr(addr);
if (bind(s, (struct sockaddr*)&saddr, sizeof(saddr)) < 0) {
switch (errno) {
case EACCES:
syslog(LOG_ERR, "socket bind failed: permission denied");
break;
case EADDRINUSE:
syslog(LOG_ERR, "socket bind failed: address already in use");
break;
case EADDRNOTAVAIL:
syslog(LOG_ERR, "socket bind failed: address not available");
break;
default:
syslog(LOG_ERR, "socket bind failed");
}
return -1;
}
syslog(LOG_INFO, "socket bind success");
//TODO: use getpwnam_r() and getgrnam_r()
struct passwd *u = getpwnam((const char *)&user);
if (setuid((*u).pw_uid) == -1) {
syslog(LOG_ERR, "failed to drop user privileges");
return -1;
}
struct group *g = getgrnam((const char *)&group);
if (setgid((*g).gr_gid) == -1) {
syslog(LOG_ERR, "failed to drop group privileges");
return -1;
}
// create persistent buffer
char *buf;
buf = malloc(1024);
if (buf == NULL) {
syslog(LOG_CRIT, "unable to allocate memory!");
close(s);
return -1;
}
while (!stop) {
struct sockaddr_in caddr;
unsigned int clen = sizeof(caddr);
memset(buf, '\0', 1024);
if (recvfrom(s, buf, 1024, 0, (struct sockaddr*)&caddr, &clen) < 0) {
syslog(LOG_ERR,
"got a client connection, but unable to receive data!");
free(buf);
continue;
}
//TODO: process packet
// we will never actually join on this thread, and don't care to keep it around.
//pthread_t *_thread; // since this hasn't been implemented yet, clang is complaining
}
// free our persistent buffer
free(buf);
// close socket
close(s);
// wait for threads to exit
pthread_exit(NULL);
// exit program
return 0;
}
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