/* * Copyright (c) 2006-2009 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 #ifdef WINDOWS32 #include "windows.h" #include #else #include #ifdef DARWIN #include #endif #define _XPG4_2 #include #include #include #include #include #include #include #include #include #include #include #endif #include "common.h" #include "dns.h" #include "encoding.h" #include "base32.h" #include "base64.h" #include "user.h" #include "login.h" #include "tun.h" #include "fw_query.h" #include "version.h" #ifdef WINDOWS32 WORD req_version = MAKEWORD(2, 2); WSADATA wsa_data; #endif static int running = 1; static char *topdomain; static char password[33]; static struct encoder *b32; static int created_users; static int check_ip; static int my_mtu; static in_addr_t my_ip; static int netmask; static in_addr_t ns_ip; static int bind_port; static int debug; #if !defined(BSD) && !defined(__GLIBC__) static char *__progname; #endif static int read_dns(int, struct query *); static void write_dns(int, struct query *, char *, int); static void sigint(int sig) { running = 0; } #ifdef WINDOWS32 #define LOG_EMERG 0 #define LOG_ALERT 1 #define LOG_CRIT 2 #define LOG_ERR 3 #define LOG_WARNING 4 #define LOG_NOTICE 5 #define LOG_INFO 6 #define LOG_DEBUG 7 static void syslog(int a, const char *str, ...) { /* TODO: implement (add to event log), move to common.c */ ; } #endif static int check_user_and_ip(int userid, struct query *q) { struct sockaddr_in *tempin; if (userid < 0 || userid >= created_users ) { return 1; } if (!users[userid].active) { return 1; } /* return early if IP checking is disabled */ if (!check_ip) { return 0; } tempin = (struct sockaddr_in *) &(q->from); return memcmp(&(users[userid].host), &(tempin->sin_addr), sizeof(struct in_addr)); } static int tunnel_tun(int tun_fd, int dns_fd) { unsigned long outlen; struct ip *header; char out[64*1024]; char in[64*1024]; int userid; int read; if ((read = read_tun(tun_fd, in, sizeof(in))) <= 0) return 0; /* find target ip in packet, in is padded with 4 bytes TUN header */ header = (struct ip*) (in + 4); userid = find_user_by_ip(header->ip_dst.s_addr); if (userid < 0) return 0; outlen = sizeof(out); compress2((uint8_t*)out, &outlen, (uint8_t*)in, read, 9); /* if another packet is queued, throw away this one. TODO build queue */ if (users[userid].outpacket.len == 0) { memcpy(users[userid].outpacket.data, out, outlen); users[userid].outpacket.len = outlen; users[userid].outpacket.offset = 0; users[userid].outpacket.sentlen = 0; users[userid].outpacket.seqno = (++users[userid].outpacket.seqno & 7); users[userid].outpacket.fragment = 0; return outlen; } else { return 0; } } typedef enum { VERSION_ACK, VERSION_NACK, VERSION_FULL } version_ack_t; static void send_version_response(int fd, version_ack_t ack, uint32_t payload, int userid, struct query *q) { char out[9]; switch (ack) { case VERSION_ACK: strncpy(out, "VACK", sizeof(out)); break; case VERSION_NACK: strncpy(out, "VNAK", sizeof(out)); break; case VERSION_FULL: strncpy(out, "VFUL", sizeof(out)); break; } out[4] = ((payload >> 24) & 0xff); out[5] = ((payload >> 16) & 0xff); out[6] = ((payload >> 8) & 0xff); out[7] = ((payload) & 0xff); out[8] = userid & 0xff; write_dns(fd, q, out, sizeof(out)); } static void send_chunk(int dns_fd, int userid) { char pkt[4096]; int datalen; int last; datalen = MIN(users[userid].fragsize, users[userid].outpacket.len - users[userid].outpacket.offset); if (datalen && users[userid].outpacket.sentlen > 0 && ( users[userid].outpacket.seqno != users[userid].out_acked_seqno || users[userid].outpacket.fragment != users[userid].out_acked_fragment ) ) { /* Still waiting on latest ack, send nothing */ datalen = 0; last = 0; /* TODO : count down and discard packet if no acks arrive within X queries */ } else { memcpy(&pkt[2], &users[userid].outpacket.data[users[userid].outpacket.offset], datalen); users[userid].outpacket.sentlen = datalen; last = (users[userid].outpacket.len == users[userid].outpacket.offset + users[userid].outpacket.sentlen); /* Increase fragment# when sending data with offset */ if (users[userid].outpacket.offset && datalen) users[userid].outpacket.fragment++; } /* Build downstream data header (see doc/proto_xxxxxxxx.txt) */ /* First byte is 1 bit compression flag, 3 bits upstream seqno, 4 bits upstream fragment */ pkt[0] = (1<<7) | ((users[userid].inpacket.seqno & 7) << 4) | (users[userid].inpacket.fragment & 15); /* Second byte is 3 bits downstream seqno, 4 bits downstream fragment, 1 bit last flag */ pkt[1] = ((users[userid].outpacket.seqno & 7) << 5) | ((users[userid].outpacket.fragment & 15) << 1) | (last & 1); if (debug >= 1) { fprintf(stderr, "OUT pkt seq# %d, frag %d (last=%d), offset %d, fragsize %d, total %d, to user %d\n", users[userid].outpacket.seqno & 7, users[userid].outpacket.fragment & 15, last, users[userid].outpacket.offset, datalen, users[userid].outpacket.len, userid); } write_dns(dns_fd, &users[userid].q, pkt, datalen + 2); users[userid].q.id = 0; if (users[userid].outpacket.len > 0 && users[userid].outpacket.len == users[userid].outpacket.sentlen) { /* Whole packet was sent in one chunk, dont wait for ack */ users[userid].outpacket.len = 0; users[userid].outpacket.offset = 0; users[userid].outpacket.sentlen = 0; } } static void update_downstream_seqno(int dns_fd, int userid, int down_seq, int down_frag) { /* If we just read a new packet from tun we have not sent a fragment of, just send it */ if (users[userid].outpacket.len > 0 && users[userid].outpacket.sentlen == 0) { send_chunk(dns_fd, userid); return; } /* otherwise, check if we received ack on a fragment and can send next */ if (users[userid].outpacket.len > 0 && users[userid].outpacket.seqno == down_seq && users[userid].outpacket.fragment == down_frag) { if (down_seq != users[userid].out_acked_seqno || down_frag != users[userid].out_acked_fragment) { /* Received ACK on downstream fragment */ users[userid].outpacket.offset += users[userid].outpacket.sentlen; users[userid].outpacket.sentlen = 0; /* Is packet done? */ if (users[userid].outpacket.offset == users[userid].outpacket.len) { users[userid].outpacket.len = 0; users[userid].outpacket.offset = 0; users[userid].outpacket.sentlen = 0; } users[userid].out_acked_seqno = down_seq; users[userid].out_acked_fragment = down_frag; /* Send reply if waiting */ if (users[userid].outpacket.len > 0) { send_chunk(dns_fd, userid); } } } } static void handle_null_request(int tun_fd, int dns_fd, struct query *q, int domain_len) { struct in_addr tempip; struct ip *hdr; unsigned long outlen; char in[512]; char logindata[16]; char out[64*1024]; char unpacked[64*1024]; char *tmp[2]; int userid; int touser; int version; int code; int read; userid = -1; memcpy(in, q->name, MIN(domain_len, sizeof(in))); if(in[0] == 'V' || in[0] == 'v') { read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), domain_len - 1, b32); /* Version greeting, compare and send ack/nak */ if (read > 4) { /* Received V + 32bits version */ version = (((unpacked[0] & 0xff) << 24) | ((unpacked[1] & 0xff) << 16) | ((unpacked[2] & 0xff) << 8) | ((unpacked[3] & 0xff))); } if (version == VERSION) { userid = find_available_user(); if (userid >= 0) { struct sockaddr_in *tempin; users[userid].seed = rand(); /* Store remote IP number */ tempin = (struct sockaddr_in *) &(q->from); memcpy(&(users[userid].host), &(tempin->sin_addr), sizeof(struct in_addr)); memcpy(&(users[userid].q), q, sizeof(struct query)); users[userid].encoder = get_base32_encoder(); send_version_response(dns_fd, VERSION_ACK, users[userid].seed, userid, q); syslog(LOG_INFO, "accepted version for user #%d from %s", userid, inet_ntoa(tempin->sin_addr)); users[userid].q.id = 0; } else { /* No space for another user */ send_version_response(dns_fd, VERSION_FULL, created_users, 0, q); syslog(LOG_INFO, "dropped user from %s, server full", inet_ntoa(((struct sockaddr_in *) &q->from)->sin_addr)); } } else { send_version_response(dns_fd, VERSION_NACK, VERSION, 0, q); syslog(LOG_INFO, "dropped user from %s, sent bad version %08X", inet_ntoa(((struct sockaddr_in *) &q->from)->sin_addr), version); } return; } else if(in[0] == 'L' || in[0] == 'l') { read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), domain_len - 1, b32); /* Login phase, handle auth */ userid = unpacked[0]; if (check_user_and_ip(userid, q) != 0) { write_dns(dns_fd, q, "BADIP", 5); syslog(LOG_WARNING, "dropped login request from user #%d from unexpected source %s", userid, inet_ntoa(((struct sockaddr_in *) &q->from)->sin_addr)); return; } else { users[userid].last_pkt = time(NULL); login_calculate(logindata, 16, password, users[userid].seed); if (read >= 18 && (memcmp(logindata, unpacked+1, 16) == 0)) { /* Login ok, send ip/mtu/netmask info */ tempip.s_addr = my_ip; tmp[0] = strdup(inet_ntoa(tempip)); tempip.s_addr = users[userid].tun_ip; tmp[1] = strdup(inet_ntoa(tempip)); read = snprintf(out, sizeof(out), "%s-%s-%d-%d", tmp[0], tmp[1], my_mtu, netmask); write_dns(dns_fd, q, out, read); q->id = 0; syslog(LOG_NOTICE, "accepted password from user #%d, given IP %s", userid, tmp[1]); free(tmp[1]); free(tmp[0]); } else { write_dns(dns_fd, q, "LNAK", 4); syslog(LOG_WARNING, "rejected login request from user #%d from %s, bad password", userid, inet_ntoa(((struct sockaddr_in *) &q->from)->sin_addr)); } } return; } else if(in[0] == 'I' || in[0] == 'i') { /* Request for IP number */ in_addr_t replyaddr; unsigned addr; char reply[5]; userid = b32_8to5(in[1]); if (check_user_and_ip(userid, q) != 0) { write_dns(dns_fd, q, "BADIP", 5); return; /* illegal id */ } if (ns_ip != INADDR_ANY) { /* If set, use assigned external ip (-n option) */ replyaddr = ns_ip; } else { /* otherwise return destination ip from packet */ memcpy(&replyaddr, &q->destination.s_addr, sizeof(in_addr_t)); } addr = htonl(replyaddr); reply[0] = 'I'; reply[1] = (addr >> 24) & 0xFF; reply[2] = (addr >> 16) & 0xFF; reply[3] = (addr >> 8) & 0xFF; reply[4] = (addr >> 0) & 0xFF; write_dns(dns_fd, q, reply, sizeof(reply)); } else if(in[0] == 'Z' || in[0] == 'z') { /* Check for case conservation and chars not allowed according to RFC */ /* Reply with received hostname as data */ write_dns(dns_fd, q, in, domain_len); return; } else if(in[0] == 'S' || in[0] == 's') { int codec; struct encoder *enc; if (domain_len < 3) { /* len at least 3, example: "S15" */ write_dns(dns_fd, q, "BADLEN", 6); return; } userid = b32_8to5(in[1]); if (check_user_and_ip(userid, q) != 0) { write_dns(dns_fd, q, "BADIP", 5); return; /* illegal id */ } codec = b32_8to5(in[2]); switch (codec) { case 5: /* 5 bits per byte = base32 */ enc = get_base32_encoder(); user_switch_codec(userid, enc); write_dns(dns_fd, q, enc->name, strlen(enc->name)); break; case 6: /* 6 bits per byte = base64 */ enc = get_base64_encoder(); user_switch_codec(userid, enc); write_dns(dns_fd, q, enc->name, strlen(enc->name)); break; default: write_dns(dns_fd, q, "BADCODEC", 8); break; } return; } else if(in[0] == 'R' || in[0] == 'r') { int req_frag_size; /* Downstream fragsize probe packet */ userid = (b32_8to5(in[1]) >> 1) & 15; if (check_user_and_ip(userid, q) != 0) { write_dns(dns_fd, q, "BADIP", 5); return; /* illegal id */ } req_frag_size = ((b32_8to5(in[1]) & 1) << 10) | ((b32_8to5(in[2]) & 31) << 5) | (b32_8to5(in[3]) & 31); if (req_frag_size < 2 || req_frag_size > 2047) { write_dns(dns_fd, q, "BADFRAG", 7); } else { char buf[2048]; memset(buf, 0, sizeof(buf)); buf[0] = (req_frag_size >> 8) & 0xff; buf[1] = req_frag_size & 0xff; write_dns(dns_fd, q, buf, req_frag_size); } return; } else if(in[0] == 'N' || in[0] == 'n') { int max_frag_size; read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), domain_len - 1, b32); /* Downstream fragsize packet */ userid = unpacked[0]; if (check_user_and_ip(userid, q) != 0) { write_dns(dns_fd, q, "BADIP", 5); return; /* illegal id */ } max_frag_size = ((unpacked[1] & 0xff) << 8) | (unpacked[2] & 0xff); if (max_frag_size < 2) { write_dns(dns_fd, q, "BADFRAG", 7); } else { users[userid].fragsize = max_frag_size; write_dns(dns_fd, q, &unpacked[1], 2); } return; } else if(in[0] == 'P' || in[0] == 'p') { int dn_seq; int dn_frag; read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), domain_len - 1, b32); /* Ping packet, store userid */ userid = unpacked[0]; if (check_user_and_ip(userid, q) != 0) { write_dns(dns_fd, q, "BADIP", 5); return; /* illegal id */ } if (debug >= 1) { fprintf(stderr, "PING pkt from user %d\n", userid); } if (users[userid].q.id != 0) { /* Send reply on earlier query before overwriting */ send_chunk(dns_fd, userid); } dn_seq = unpacked[1] >> 4; dn_frag = unpacked[1] & 15; memcpy(&(users[userid].q), q, sizeof(struct query)); users[userid].last_pkt = time(NULL); /* Update seqno and maybe send immediate response packet */ update_downstream_seqno(dns_fd, userid, dn_seq, dn_frag); } 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; userid = code; /* Check user and sending ip number */ if (check_user_and_ip(userid, q) != 0) { write_dns(dns_fd, q, "BADIP", 5); } else { /* Decode data header */ int up_seq = (b32_8to5(in[1]) >> 2) & 7; int up_frag = ((b32_8to5(in[1]) & 3) << 2) | ((b32_8to5(in[2]) >> 3) & 3); int dn_seq = (b32_8to5(in[2]) & 7); int dn_frag = b32_8to5(in[3]) >> 1; int lastfrag = b32_8to5(in[3]) & 1; if (users[userid].q.id != 0) { /* Send reply on earlier query before overwriting */ send_chunk(dns_fd, userid); } /* Update query and time info for user */ users[userid].last_pkt = time(NULL); memcpy(&(users[userid].q), q, sizeof(struct query)); if (up_seq == users[userid].inpacket.seqno && up_frag <= users[userid].inpacket.fragment) { /* Got repeated old packet, skip it */ if (debug >= 1) { fprintf(stderr, "IN pkt seq# %d, frag %d, dropped duplicate\n", up_seq, up_frag); } /* Update seqno and maybe send immediate response packet */ update_downstream_seqno(dns_fd, userid, dn_seq, dn_frag); return; } if (up_seq != users[userid].inpacket.seqno) { /* New packet has arrived */ users[userid].inpacket.seqno = up_seq; users[userid].inpacket.len = 0; users[userid].inpacket.offset = 0; } users[userid].inpacket.fragment = up_frag; /* decode with this users encoding */ read = unpack_data(unpacked, sizeof(unpacked), &(in[4]), domain_len - 4, users[userid].encoder); /* copy to packet buffer, update length */ memcpy(users[userid].inpacket.data + users[userid].inpacket.offset, unpacked, read); users[userid].inpacket.len += read; users[userid].inpacket.offset += read; if (debug >= 1) { fprintf(stderr, "IN pkt seq# %d, frag %d (last=%d), fragsize %d, total %d, from user %d\n", up_seq, up_frag, lastfrag, read, users[userid].inpacket.len, userid); } if (lastfrag & 1) { /* packet is complete */ int ret; outlen = sizeof(out); ret = uncompress((uint8_t*)out, &outlen, (uint8_t*)users[userid].inpacket.data, users[userid].inpacket.len); if (ret == Z_OK) { hdr = (struct ip*) (out + 4); touser = find_user_by_ip(hdr->ip_dst.s_addr); if (touser == -1) { /* send the uncompressed packet to tun device */ write_tun(tun_fd, out, outlen); } else { /* send the compressed packet to other client * if another packet is queued, throw away this one. TODO build queue */ if (users[touser].outpacket.len == 0) { memcpy(users[touser].outpacket.data, users[userid].inpacket.data, users[userid].inpacket.len); users[touser].outpacket.len = users[userid].inpacket.len; } } } else { fprintf(stderr, "Discarded data, uncompress() result: %d\n", ret); } users[userid].inpacket.len = users[userid].inpacket.offset = 0; } /* Update seqno and maybe send immediate response packet */ update_downstream_seqno(dns_fd, userid, dn_seq, dn_frag); } } } static void handle_ns_request(int dns_fd, struct query *q) { char buf[64*1024]; int len; if (ns_ip != INADDR_ANY) { /* If ns_ip set, overwrite destination addr with it. * Destination addr will be sent as additional record (A, IN) */ memcpy(&q->destination.s_addr, &ns_ip, sizeof(in_addr_t)); } len = dns_encode_ns_response(buf, sizeof(buf), q, topdomain); if (debug >= 2) { struct sockaddr_in *tempin; tempin = (struct sockaddr_in *) &(q->from); fprintf(stderr, "TX: client %s, type %d, name %s, %d bytes NS reply\n", inet_ntoa(tempin->sin_addr), q->type, q->name, len); } if (sendto(dns_fd, buf, len, 0, (struct sockaddr*)&q->from, q->fromlen) <= 0) { warn("ns reply send error"); } } static void forward_query(int bind_fd, struct query *q) { char buf[64*1024]; int len; struct fw_query fwq; struct sockaddr_in *myaddr; in_addr_t newaddr; len = dns_encode(buf, sizeof(buf), q, QR_QUERY, q->name, strlen(q->name)); /* Store sockaddr for q->id */ memcpy(&(fwq.addr), &(q->from), q->fromlen); fwq.addrlen = q->fromlen; fwq.id = q->id; fw_query_put(&fwq); newaddr = inet_addr("127.0.0.1"); myaddr = (struct sockaddr_in *) &(q->from); memcpy(&(myaddr->sin_addr), &newaddr, sizeof(in_addr_t)); myaddr->sin_port = htons(bind_port); if (debug >= 2) { fprintf(stderr, "TX: NS reply \n"); } if (sendto(bind_fd, buf, len, 0, (struct sockaddr*)&q->from, q->fromlen) <= 0) { warn("forward query error"); } } static int tunnel_bind(int bind_fd, int dns_fd) { char packet[64*1024]; struct sockaddr_in from; socklen_t fromlen; struct fw_query *query; unsigned short id; int r; fromlen = sizeof(struct sockaddr); r = recvfrom(bind_fd, packet, sizeof(packet), 0, (struct sockaddr*)&from, &fromlen); if (r <= 0) return 0; id = dns_get_id(packet, r); if (debug >= 2) { fprintf(stderr, "RX: Got response on query %u from DNS\n", (id & 0xFFFF)); } /* Get sockaddr from id */ fw_query_get(id, &query); if (!query && debug >= 2) { fprintf(stderr, "Lost sender of id %u, dropping reply\n", (id & 0xFFFF)); return 0; } if (debug >= 2) { struct sockaddr_in *in; in = (struct sockaddr_in *) &(query->addr); fprintf(stderr, "TX: client %s id %u, %d bytes\n", inet_ntoa(in->sin_addr), (id & 0xffff), r); } if (sendto(dns_fd, packet, r, 0, (const struct sockaddr *) &(query->addr), query->addrlen) <= 0) { warn("forward reply error"); } return 0; } static int tunnel_dns(int tun_fd, int dns_fd, int bind_fd) { struct query q; int read; char *domain; int domain_len; int inside_topdomain; if ((read = read_dns(dns_fd, &q)) <= 0) return 0; if (debug >= 2) { struct sockaddr_in *tempin; tempin = (struct sockaddr_in *) &(q.from); fprintf(stderr, "RX: client %s, type %d, name %s\n", inet_ntoa(tempin->sin_addr), q.type, q.name); } domain = strstr(q.name, topdomain); inside_topdomain = 0; if (domain) { domain_len = (int) (domain - q.name); if (domain_len + strlen(topdomain) == strlen(q.name)) { inside_topdomain = 1; } } if (inside_topdomain) { /* This is a query we can handle */ switch (q.type) { case T_NULL: handle_null_request(tun_fd, dns_fd, &q, domain_len); break; case T_NS: handle_ns_request(dns_fd, &q); break; default: break; } } else { /* Forward query to other port ? */ if (bind_fd) { forward_query(bind_fd, &q); } } return 0; } static int tunnel(int tun_fd, int dns_fd, int bind_fd) { struct timeval tv; fd_set fds; int i; while (running) { int maxfd; if (users_waiting_on_reply()) { tv.tv_sec = 0; tv.tv_usec = 15000; } else { tv.tv_sec = 1; tv.tv_usec = 0; } FD_ZERO(&fds); FD_SET(dns_fd, &fds); maxfd = dns_fd; if (bind_fd) { /* wait for replies from real DNS */ FD_SET(bind_fd, &fds); maxfd = MAX(bind_fd, maxfd); } /* TODO : use some kind of packet queue */ if(!all_users_waiting_to_send()) { FD_SET(tun_fd, &fds); maxfd = MAX(tun_fd, maxfd); } i = select(maxfd + 1, &fds, NULL, NULL, &tv); if(i < 0) { if (running) warn("select"); return 1; } if (i==0) { int j; for (j = 0; j < USERS; j++) { if (users[j].q.id != 0) { send_chunk(dns_fd, j); } } } else { if(FD_ISSET(tun_fd, &fds)) { tunnel_tun(tun_fd, dns_fd); continue; } if(FD_ISSET(dns_fd, &fds)) { tunnel_dns(tun_fd, dns_fd, bind_fd); continue; } if(FD_ISSET(bind_fd, &fds)) { tunnel_bind(bind_fd, dns_fd); continue; } } } return 0; } static void send_raw(int fd, char *buf, int buflen, int cmd, struct query *q) { char packet[4096]; int len; len = MIN(sizeof(packet) - RAW_HDR_LEN, buflen); memcpy(packet, raw_header, RAW_HDR_LEN); memcpy(&packet[RAW_HDR_LEN], buf, len); len += RAW_HDR_LEN; packet[RAW_HDR_CMD] = cmd; sendto(fd, packet, len, 0, &q->from, q->fromlen); } static void handle_raw_login(char *packet, int len, struct query *q, int fd) { int userid; char myhash[16]; if (len < 17) return; userid = packet[16]; if (userid < 0 || userid > created_users) return; if (!users[userid].active) return; login_calculate(myhash, 16, password, users[userid].seed + 1); if (memcmp(packet, myhash, 16) == 0) { /* Correct hash, reply with hash of seed - 1 */ users[userid].last_pkt = time(NULL); login_calculate(myhash, 16, password, users[userid].seed - 1); memcpy(packet, myhash, 16); send_raw(fd, packet, 17, RAW_HDR_CMD_LOGIN, q); } } static int raw_decode(char *packet, int len, struct query *q, int fd) { /* minimum length */ if (len < RAW_HDR_LEN) return 0; /* should start with header */ if (memcmp(packet, raw_header, RAW_HDR_IDENT_LEN)) return 0; if (packet[RAW_HDR_CMD] == RAW_HDR_CMD_LOGIN) { handle_raw_login(&packet[RAW_HDR_LEN], len - RAW_HDR_LEN, q, fd); } else { warnx("Unhandled raw command %02X\n", packet[RAW_HDR_CMD]); } return 1; } static int read_dns(int fd, struct query *q) { struct sockaddr_in from; socklen_t addrlen; char packet[64*1024]; int r; #ifndef WINDOWS32 char address[96]; struct msghdr msg; struct iovec iov; struct cmsghdr *cmsg; addrlen = sizeof(struct sockaddr); iov.iov_base = packet; iov.iov_len = sizeof(packet); msg.msg_name = (caddr_t) &from; msg.msg_namelen = (unsigned) addrlen; msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = address; msg.msg_controllen = sizeof(address); msg.msg_flags = 0; r = recvmsg(fd, &msg, 0); #else addrlen = sizeof(struct sockaddr); r = recvfrom(fd, packet, sizeof(packet), 0, (struct sockaddr*)&from, &addrlen); #endif /* !WINDOWS32 */ if (r > 0) { memcpy((struct sockaddr*)&q->from, (struct sockaddr*)&from, addrlen); q->fromlen = addrlen; /* TODO do not handle raw packets here! */ if (raw_decode(packet, r, q, fd)) { return 0; } if (dns_decode(NULL, 0, q, QR_QUERY, packet, r) < 0) { return 0; } #ifndef WINDOWS32 for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL; cmsg = CMSG_NXTHDR(&msg, cmsg)) { if (cmsg->cmsg_level == IPPROTO_IP && cmsg->cmsg_type == DSTADDR_SOCKOPT) { q->destination = *dstaddr(cmsg); break; } } #endif return strlen(q->name); } else if (r < 0) { /* Error */ warn("read dns"); } return 0; } static void write_dns(int fd, struct query *q, char *data, int datalen) { char buf[64*1024]; int len; len = dns_encode(buf, sizeof(buf), q, QR_ANSWER, data, datalen); if (debug >= 2) { struct sockaddr_in *tempin; tempin = (struct sockaddr_in *) &(q->from); fprintf(stderr, "TX: client %s, type %d, name %s, %d bytes data\n", inet_ntoa(tempin->sin_addr), q->type, q->name, datalen); } sendto(fd, buf, len, 0, (struct sockaddr*)&q->from, q->fromlen); } static void usage() { extern char *__progname; fprintf(stderr, "Usage: %s [-v] [-h] [-c] [-s] [-f] [-D] [-u user] " "[-t chrootdir] [-d device] [-m mtu] [-z context] " "[-l ip address to listen on] [-p port] [-n external ip] [-b dnsport] [-P password]" " tunnel_ip[/netmask] topdomain\n", __progname); exit(2); } static void help() { extern char *__progname; fprintf(stderr, "iodine IP over DNS tunneling server\n"); fprintf(stderr, "Usage: %s [-v] [-h] [-c] [-s] [-f] [-D] [-u user] " "[-t chrootdir] [-d device] [-m mtu] [-z context] " "[-l ip address to listen on] [-p port] [-n external ip] [-b dnsport] [-P password]" " tunnel_ip[/netmask] topdomain\n", __progname); fprintf(stderr, " -v to print version info and exit\n"); fprintf(stderr, " -h to print this help and exit\n"); fprintf(stderr, " -c to disable check of client IP/port on each request\n"); fprintf(stderr, " -s to skip creating and configuring the tun device, " "which then has to be created manually\n"); fprintf(stderr, " -f to keep running in foreground\n"); fprintf(stderr, " -D to increase debug level\n"); fprintf(stderr, " -u name to drop privileges and run as user 'name'\n"); fprintf(stderr, " -t dir to chroot to directory dir\n"); fprintf(stderr, " -d device to set tunnel device name\n"); fprintf(stderr, " -m mtu to set tunnel device mtu\n"); fprintf(stderr, " -z context to apply SELinux context after initialization\n"); fprintf(stderr, " -l ip address to listen on for incoming dns traffic " "(default 0.0.0.0)\n"); fprintf(stderr, " -p port to listen on for incoming dns traffic (default 53)\n"); fprintf(stderr, " -n ip to respond with to NS queries\n"); fprintf(stderr, " -b port to forward normal DNS queries to (on localhost)\n"); fprintf(stderr, " -P password used for authentication (max 32 chars will be used)\n"); fprintf(stderr, "tunnel_ip is the IP number of the local tunnel interface.\n"); fprintf(stderr, " /netmask sets the size of the tunnel network.\n"); fprintf(stderr, "topdomain is the FQDN that is delegated to this server.\n"); exit(0); } static void version() { char *svnver; svnver = "$Rev$ from $Date$"; fprintf(stderr, "iodine IP over DNS tunneling server\n"); fprintf(stderr, "SVN version: %s\n", svnver); exit(0); } int main(int argc, char **argv) { extern char *__progname; in_addr_t listen_ip; #ifndef WINDOWS32 struct passwd *pw; #endif int foreground; char *username; char *newroot; char *context; char *device; int dnsd_fd; int tun_fd; /* settings for forwarding normal DNS to * local real DNS server */ int bind_fd; int bind_enable; int choice; int port; int mtu; int skipipconfig; char *netsize; int retval; username = NULL; newroot = NULL; context = NULL; device = NULL; foreground = 0; bind_enable = 0; bind_fd = 0; mtu = 1200; listen_ip = INADDR_ANY; port = 53; ns_ip = INADDR_ANY; check_ip = 1; skipipconfig = 0; debug = 0; netmask = 27; b32 = get_base32_encoder(); retval = 0; #ifdef WINDOWS32 WSAStartup(req_version, &wsa_data); #endif #if !defined(BSD) && !defined(__GLIBC__) __progname = strrchr(argv[0], '/'); if (__progname == NULL) __progname = argv[0]; else __progname++; #endif memset(password, 0, sizeof(password)); srand(time(NULL)); fw_query_init(); while ((choice = getopt(argc, argv, "vcsfhDu:t:d:m:l:p:n:b:P:z:")) != -1) { switch(choice) { case 'v': version(); break; case 'c': check_ip = 0; break; case 's': skipipconfig = 1; break; case 'f': foreground = 1; break; case 'h': help(); break; case 'D': debug++; 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; case 'p': port = atoi(optarg); break; case 'n': ns_ip = inet_addr(optarg); break; case 'b': bind_enable = 1; bind_port = atoi(optarg); break; case 'P': strncpy(password, optarg, sizeof(password)); password[sizeof(password)-1] = 0; /* XXX: find better way of cleaning up ps(1) */ memset(optarg, 0, strlen(optarg)); break; case 'z': context = optarg; break; default: usage(); break; } } argc -= optind; argv += optind; check_superuser(usage); if (argc != 2) usage(); netsize = strchr(argv[0], '/'); if (netsize) { *netsize = 0; netsize++; netmask = atoi(netsize); } my_ip = inet_addr(argv[0]); if (my_ip == INADDR_NONE) { warnx("Bad IP address to use inside tunnel.\n"); usage(); } topdomain = strdup(argv[1]); if(strlen(topdomain) <= 128) { if(check_topdomain(topdomain)) { warnx("Topdomain contains invalid characters.\n"); usage(); } } else { warnx("Use a topdomain max 128 chars long.\n"); usage(); } if (username != NULL) { #ifndef WINDOWS32 if ((pw = getpwnam(username)) == NULL) { warnx("User %s does not exist!\n", username); usage(); } #endif } if (mtu <= 0) { warnx("Bad MTU given.\n"); usage(); } if(port < 1 || port > 65535) { warnx("Bad port number given.\n"); usage(); } if(bind_enable) { if (bind_port < 1 || bind_port > 65535 || bind_port == port) { warnx("Bad DNS server port number given.\n"); usage(); /* NOTREACHED */ } fprintf(stderr, "Requests for domains outside of %s will be forwarded to port %d\n", topdomain, bind_port); } if (port != 53) { fprintf(stderr, "ALERT! Other dns servers expect you to run on port 53.\n"); fprintf(stderr, "You must manually forward port 53 to port %d for things to work.\n", port); } if (debug) { fprintf(stderr, "Debug level %d enabled, will stay in foreground.\n", debug); fprintf(stderr, "Add more -D switches to set higher debug level.\n"); foreground = 1; } if (listen_ip == INADDR_NONE) { warnx("Bad IP address to listen on.\n"); usage(); } if (ns_ip == INADDR_NONE) { warnx("Bad IP address to return as nameserver.\n"); usage(); } if (netmask > 30 || netmask < 8) { warnx("Bad netmask (%d bits). Use 8-30 bits.\n", netmask); usage(); } if (strlen(password) == 0) read_password(password, sizeof(password)); if ((tun_fd = open_tun(device)) == -1) { retval = 1; goto cleanup0; } if (!skipipconfig) { if (tun_setip(argv[0], netmask) != 0 || tun_setmtu(mtu) != 0) { retval = 1; goto cleanup1; } } if ((dnsd_fd = open_dns(port, listen_ip)) == -1) { retval = 1; goto cleanup2; } if (bind_enable) { if ((bind_fd = open_dns(0, INADDR_ANY)) == -1) { retval = 1; goto cleanup3; } } my_mtu = mtu; created_users = init_users(my_ip, netmask); if (created_users < USERS) { fprintf(stderr, "Limiting to %d simultaneous users because of netmask /%d\n", created_users, netmask); } fprintf(stderr, "Listening to dns for domain %s\n", topdomain); if (foreground == 0) do_detach(); if (newroot != NULL) do_chroot(newroot); signal(SIGINT, sigint); if (username != NULL) { #ifndef WINDOWS32 gid_t gids[1]; gids[0] = pw->pw_gid; if (setgroups(1, gids) < 0 || setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) { warnx("Could not switch to user %s!\n", username); usage(); } #endif } if (context != NULL) do_setcon(context); #ifndef WINDOWS32 openlog(__progname, LOG_NOWAIT, LOG_DAEMON); #endif syslog(LOG_INFO, "started, listening on port %d", port); tunnel(tun_fd, dnsd_fd, bind_fd); syslog(LOG_INFO, "stopping"); cleanup3: close_dns(bind_fd); cleanup2: close_dns(dnsd_fd); cleanup1: close_tun(tun_fd); cleanup0: return retval; }