/* * Copyright (c) 2006 Bjorn Andersson , Erik Ekman * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "tun.h" #include "structs.h" #include "dns.h" #ifndef MAX #define MAX(a,b) ((a)>(b)?(a):(b)) #endif int running = 1; struct packet packetbuf; struct packet outpacket; int outid; struct query q; int my_mtu; in_addr_t my_ip; static void sigint(int sig) { running = 0; } static int tunnel(int tun_fd, int dns_fd) { struct in_addr clientip; struct in_addr myip; struct timeval tv; char out[64*1024]; char in[64*1024]; char *tmp[2]; long outlen; fd_set fds; int read; int code; int i; while (running) { if (q.id != 0) { tv.tv_sec = 0; tv.tv_usec = 5000; } else { tv.tv_sec = 1; tv.tv_usec = 0; } FD_ZERO(&fds); if(outpacket.len == 0) FD_SET(tun_fd, &fds); FD_SET(dns_fd, &fds); i = select(MAX(tun_fd, dns_fd) + 1, &fds, NULL, NULL, &tv); if(i < 0) { if (running) warn("select"); return 1; } if (i==0) { if (q.id != 0) { dnsd_send(dns_fd, &q, outpacket.data, outpacket.len); outpacket.len = 0; q.id = 0; } } else { if(FD_ISSET(tun_fd, &fds)) { read = read_tun(tun_fd, in, sizeof(in)); if (read <= 0) continue; outlen = sizeof(out); compress2(out, &outlen, in, read, 9); memcpy(outpacket.data, out, outlen); outpacket.len = outlen; } if(FD_ISSET(dns_fd, &fds)) { read = dnsd_read(dns_fd, &q, in, sizeof(in)); if (read < 0) continue; if(in[0] == 'H' || in[0] == 'h') { myip.s_addr = my_ip; clientip.s_addr = my_ip + inet_addr("0.0.0.1"); tmp[0] = strdup(inet_ntoa(myip)); tmp[1] = strdup(inet_ntoa(clientip)); read = snprintf(out, sizeof(out), "%s-%s-%d", tmp[0], tmp[1], my_mtu); dnsd_send(dns_fd, &q, out, read); q.id = 0; free(tmp[1]); free(tmp[0]); } else if((in[0] >= '0' && in[0] <= '9') || (in[0] >= 'a' && in[0] <= 'f') || (in[0] >= 'A' && in[0] <= 'F')) { if ((in[0] >= '0' && in[0] <= '9')) code = in[0] - '0'; if ((in[0] >= 'a' && in[0] <= 'f')) code = in[0] - 'a' + 10; if ((in[0] >= 'A' && in[0] <= 'F')) code = in[0] - 'A' + 10; memcpy(packetbuf.data + packetbuf.offset, in + 1, read - 1); packetbuf.len += read - 1; packetbuf.offset += read - 1; if (code & 1) { outlen = sizeof(out); uncompress(out, &outlen, packetbuf.data, packetbuf.len); write_tun(tun_fd, out, outlen); packetbuf.len = packetbuf.offset = 0; } } if (outpacket.len > 0) { dnsd_send(dns_fd, &q, outpacket.data, outpacket.len); outpacket.len = 0; q.id = 0; } } } } return 0; } static void usage() { extern char *__progname; printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] [-m mtu] [-l ip address to listen on] " "tunnel_ip topdomain\n", __progname); exit(2); } static void help() { extern char *__progname; printf("iodine IP over DNS tunneling server\n"); printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] [-m mtu] [-l ip address to listen on] " "tunnel_ip topdomain\n", __progname); printf(" -v to print version info and exit\n"); printf(" -h to print this help and exit\n"); printf(" -f to keep running in foreground\n"); printf(" -u name to drop privileges and run as user 'name'\n"); printf(" -t dir to chroot to directory dir\n"); printf(" -d device to set tunnel device name\n"); printf(" -m mtu to set tunnel device mtu\n"); printf(" -l ip address to listen on for incoming dns traffic (default 0.0.0.0)\n"); printf("tunnel_ip is the IP number of the local tunnel interface.\n"); printf("topdomain is the FQDN that is delegated to this server.\n"); exit(0); } static void version() { char *svnver = "$Rev$ from $Date$"; printf("iodine IP over DNS tunneling server\n"); printf("SVN version: %s\n", svnver); exit(0); } int main(int argc, char **argv) { int choice; int tun_fd; int dnsd_fd; char *newroot; char *username; char *device; int foreground; int mtu; struct passwd *pw; in_addr_t listen_ip; username = NULL; newroot = NULL; device = NULL; foreground = 0; mtu = 1024; listen_ip = INADDR_ANY; packetbuf.len = 0; packetbuf.offset = 0; outpacket.len = 0; q.id = 0; while ((choice = getopt(argc, argv, "vfhu:t:d:m:l:")) != -1) { switch(choice) { case 'v': version(); break; case 'f': foreground = 1; break; case 'h': help(); break; case 'u': username = optarg; break; case 't': newroot = optarg; break; case 'd': device = optarg; break; case 'm': mtu = atoi(optarg); break; case 'l': listen_ip = inet_addr(optarg); break; default: usage(); break; } } argc -= optind; argv += optind; if (geteuid() != 0) { printf("Run as root and you'll be happy.\n"); usage(); } if (argc != 2) usage(); if (username) { pw = getpwnam(username); if (!pw) { printf("User %s does not exist!\n", username); usage(); } } if (mtu == 0) { printf("Bad MTU given.\n"); usage(); } if (listen_ip == INADDR_NONE) { printf("Bad IP address to listen on.\n"); usage(); } if ((tun_fd = open_tun(device)) == -1) goto cleanup0; if (tun_setip(argv[0]) != 0 || tun_setmtu(mtu) != 0) goto cleanup1; if ((dnsd_fd = open_dns(argv[1], 53, listen_ip)) == -1) goto cleanup2; my_ip = inet_addr(argv[0]); my_mtu = mtu; printf("Listening to dns for domain %s\n", argv[1]); if (newroot) { if (chroot(newroot) != 0 || chdir("/") != 0) err(1, "%s", newroot); seteuid(geteuid()); setuid(getuid()); } if (!foreground) { printf("Detaching from terminal...\n"); daemon(0, 0); umask(0); alarm(0); } signal(SIGINT, sigint); if (username) { if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) { printf("Could not switch to user %s!\n", username); usage(); } } tunnel(tun_fd, dnsd_fd); cleanup2: close_dns(dnsd_fd); cleanup1: close_tun(tun_fd); cleanup0: return 0; }