--- gvpe/src/vpn_dns.C 2008/08/07 17:54:27 1.47 +++ gvpe/src/vpn_dns.C 2011/03/06 19:40:28 1.51 @@ -1,6 +1,6 @@ /* vpn_dns.C -- handle the dns tunnel part of the protocol. - Copyright (C) 2003-2008 Marc Lehmann + Copyright (C) 2003-2011 Marc Lehmann This file is part of GVPE. @@ -61,8 +61,8 @@ #include "vpn.h" -#define MAX_POLL_INTERVAL 5. // how often to poll minimally when the server has no data -#define ACTIVITY_INTERVAL 5. +#define MIN_POLL_INTERVAL 0.1 // poll at most this often when no data received +#define MAX_POLL_INTERVAL 1. // how often to poll minimally when the server has no data #define INITIAL_TIMEOUT 0.1 // retry timeouts #define INITIAL_SYN_TIMEOUT 2. // retry timeout for initial syn @@ -85,6 +85,7 @@ #define RR_TYPE_A 1 #define RR_TYPE_NULL 10 #define RR_TYPE_TXT 16 +#define RR_TYPE_AAAA 28 #define RR_TYPE_ANY 255 #define RR_CLASS_IN 1 @@ -92,9 +93,23 @@ #define CMD_IP_1 207 #define CMD_IP_2 46 #define CMD_IP_3 236 -#define CMD_IP_RST 29 -#define CMD_IP_SYN 113 -#define CMD_IP_REJ 32 + +#define CMD_IP_RST 29 // some error, reset and retry +#define CMD_IP_REJ 32 // do not want you +#define CMD_IP_SYN 113 // connection established +#define CMD_IP_CSE 213 // connection established, but likely case mismatch + +static bool +is_uc (char c) +{ + return 'A' <= c && c <= 'Z'; +} + +static bool +is_lc (char c) +{ + return 'a' <= c && c <= 'z'; +} // works for cmaps up to 255 (not 256!) struct charmap @@ -118,8 +133,14 @@ for (size = 0; cmap [size]; size++) { - enc [size] = cmap [size]; - dec [(u8)enc [size]] = size; + char c = cmap [size]; + + enc [size] = c; + dec [(u8)c] = size; + + // allow lowercase/uppercase aliases if possible + if (is_uc (c) && dec [c + ('a' - 'A')] == INVALID) dec [c + ('a' - 'A')] = size; + if (is_lc (c) && dec [c - ('a' - 'A')] == INVALID) dec [c - ('a' - 'A')] = size; } assert (size < 256); @@ -136,11 +157,11 @@ unsigned int enc_len [MAX_DEC_LEN]; unsigned int dec_len [MAX_ENC_LEN]; - unsigned int encode_len (unsigned int len); - unsigned int decode_len (unsigned int len); + unsigned int encode_len (unsigned int len) const; + unsigned int decode_len (unsigned int len) const; - unsigned int encode (char *dst, u8 *src, unsigned int len); - unsigned int decode (u8 *dst, char *src, unsigned int len); + unsigned int encode (char *dst, u8 *src, unsigned int len) const; + unsigned int decode (u8 *dst, char *src, unsigned int len) const; basecoder (const char *cmap); }; @@ -169,12 +190,14 @@ } } -unsigned int basecoder::encode_len (unsigned int len) +unsigned int +basecoder::encode_len (unsigned int len) const { return enc_len [len]; } -unsigned int basecoder::decode_len (unsigned int len) +unsigned int +basecoder::decode_len (unsigned int len) const { while (len && !dec_len [len]) --len; @@ -182,7 +205,8 @@ return dec_len [len]; } -unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len) +unsigned int +basecoder::encode (char *dst, u8 *src, unsigned int len) const { if (!len || len > MAX_DEC_LEN) return 0; @@ -211,7 +235,8 @@ return elen; } -unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len) +unsigned int +basecoder::decode (u8 *dst, char *src, unsigned int len) const { if (!len || len > MAX_ENC_LEN) return 0; @@ -270,39 +295,39 @@ } #endif -//static basecoder cdc64 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI-"); -//static basecoder cdc63 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); -static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); -//static basecoder cdc36 ("dphzr06qmjkb34tsvl81xaef92wgyo57ucni"); // unused as of yet -static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyO"); +static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); // a-zA-Z0-9 +static basecoder cdc36 ("dPhZr06QmJkB34tSvL81xAeF92wGyO57uCnI"); // a-z0-9 for case-changers +static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyOuCnI"); // a-z ///////////////////////////////////////////////////////////////////////////// -#define HDRSIZE 6 +#define HDRSIZE 5 -inline void encode_header (char *data, int clientid, int seqno, int retry = 0) +inline void +encode_header (char *data, int clientid, int seqno, int retry = 0) { + assert (clientid < 256); + seqno &= SEQNO_MASK; u8 hdr[3] = { - clientid, - (seqno >> 8) | (retry << 6), seqno, + (seqno >> 8) | (retry << 6), + clientid, }; - assert (clientid < 256); - - cdc26.encode (data, hdr, 3); + cdc36.encode (data, hdr, 3); } -inline void decode_header (char *data, int &clientid, int &seqno) +inline void +decode_header (char *data, int &clientid, int &seqno) { u8 hdr[3]; - cdc26.decode (hdr, data, HDRSIZE); + cdc36.decode (hdr, data, HDRSIZE); - clientid = hdr[0]; - seqno = ((hdr[1] << 8) | hdr[2]) & SEQNO_MASK; + clientid = hdr[2]; + seqno = ((hdr[1] << 8) | hdr[0]) & SEQNO_MASK; } ///////////////////////////////////////////////////////////////////////////// @@ -338,7 +363,8 @@ delete data; } -void byte_stream::remove (int count) +void +byte_stream::remove (int count) { if (count > fill) assert (count <= fill); @@ -346,7 +372,8 @@ memmove (data, data + count, fill -= count); } -bool byte_stream::put (u8 *data, unsigned int datalen) +bool +byte_stream::put (u8 *data, unsigned int datalen) { if (maxsize - fill < datalen) return false; @@ -356,7 +383,8 @@ return true; } -bool byte_stream::put (vpn_packet *pkt) +bool +byte_stream::put (vpn_packet *pkt) { if (maxsize - fill < pkt->len + 2) return false; @@ -422,57 +450,80 @@ { static int next_uid; - u8 id1, id2, id3, id4; + u8 chksum; + u8 rrtype; + u16 uid; // to make request unique u8 version; u8 flags; - u8 rrtype; - u8 def_ttl; + u16 max_size; - u16 client; - u16 uid; // to make request unique + u8 id1, id2, id3, id4; - u16 max_size; - u8 seq_cdc; - u8 req_cdc; + u16 client; + u8 def_ttl; + u8 r0; - u8 rep_cdc; - u8 delay; // time in 0.01s units that the server may delay replying packets - u8 r3, r4; + u8 syn_cdc; // cdc en/decoder for syn (A?) requests + u8 hdr_cdc; // cdc en/decoder for regular request headers + u8 req_cdc; // cdc en/decoder for regular (ANY?) request data + u8 rep_cdc; // cdc en/decoder for regular (TXT) replies, 0 == 8 bit encoding - u8 r5, r6, r7, r8; + u8 r1, r2, r3, r4; void reset (int clientid); bool valid (); + u8 get_chksum (); }; int dns_cfg::next_uid; -void dns_cfg::reset (int clientid) +void +dns_cfg::reset (int clientid) { + // this ID must result in some mixed-case characters in cdc26-encoding id1 = 'G'; id2 = 'V'; id3 = 'P'; id4 = 'E'; - version = 1; + version = 2; rrtype = RR_TYPE_TXT; flags = 0; def_ttl = 0; - seq_cdc = 26; - req_cdc = 62; + syn_cdc = 26; + hdr_cdc = 36; + req_cdc = conf.dns_case_preserving ? 62 : 36; rep_cdc = 0; max_size = htons (MAX_PKT_SIZE); client = htons (clientid); - uid = next_uid++; - delay = 0; + uid = ++next_uid; + + r0 = r1 = r2 = r3 = r4 = 0; - r3 = r4 = 0; - r4 = r5 = r6 = r7 = 0; + chksum = get_chksum (); } -bool dns_cfg::valid () +// simple but not trivial chksum +u8 +dns_cfg::get_chksum () +{ + unsigned int sum = 0xff00; // only 16 bits required + + u8 old_chksum = chksum; + chksum = 0; + + for (unsigned int i = 0; i < sizeof (*this); ++i) + sum += ((u8 *)this)[i] * (i + 1); + + chksum = old_chksum; + + return sum + (sum >> 8); +} + +bool +dns_cfg::valid () { // although the protocol itself allows for some configurability, // only the following encoding/decoding settings are implemented. @@ -480,10 +531,12 @@ && id2 == 'V' && id3 == 'P' && id4 == 'E' - && seq_cdc == 26 - && req_cdc == 62 + && version == 2 + && syn_cdc == 26 + && hdr_cdc == 36 + && (req_cdc == 36 || req_cdc == 62) && rep_cdc == 0 - && version == 1; + && chksum == get_chksum (); } struct dns_packet : net_packet @@ -497,7 +550,8 @@ int decode_label (char *data, int size, int &offs); }; -int dns_packet::decode_label (char *data, int size, int &offs) +int +dns_packet::decode_label (char *data, int size, int &offs) { char *orig = data; @@ -533,10 +587,11 @@ ///////////////////////////////////////////////////////////////////////////// -static u16 dns_id = 0; // TODO: should be per-vpn - -static u16 next_id () +static +u16 next_id () { + static u16 dns_id = 0; // TODO: should be per-vpn + if (!dns_id) dns_id = time (0); @@ -561,6 +616,7 @@ dns_cfg cfg; bool established; + const basecoder *cdc; tstamp last_received; tstamp last_sent; @@ -575,6 +631,9 @@ inline void time_cb (ev::timer &w, int revents); ev::timer tw; void receive_rep (dns_rcv *r); + void reset (); // quite like tcp RST + void set_cfg (); // to be called after any cfg changes + dns_connection (connection *c); ~dns_connection (); }; @@ -614,7 +673,8 @@ delete pkt; } -static void append_domain (dns_packet &pkt, int &offs, const char *domain) +static void +append_domain (dns_packet &pkt, int &offs, const char *domain) { // add tunnel domain for (;;) @@ -637,7 +697,8 @@ } } -void dns_snd::gen_stream_req (int seqno, byte_stream &stream) +void +dns_snd::gen_stream_req (int seqno, byte_stream &stream) { stdhdr = true; this->seqno = seqno; @@ -655,12 +716,12 @@ char enc[256], *encp = enc; encode_header (enc, THISNODE->id, seqno); - int datalen = cdc62.decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE); + int datalen = dns->cdc->decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE); if (datalen > stream.size ()) datalen = stream.size (); - int enclen = cdc62.encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE; + int enclen = dns->cdc->encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE; stream.remove (datalen); while (enclen) @@ -685,7 +746,8 @@ pkt->len = offs; } -void dns_snd::gen_syn_req () +void +dns_snd::gen_syn_req () { timeout = ev_now () + INITIAL_SYN_TIMEOUT; @@ -742,6 +804,30 @@ vpn = c->vpn; + reset (); +} + +dns_connection::~dns_connection () +{ + reset (); +} + +void +dns_connection::reset () +{ + while (!rcvpq.empty ()) + { + delete rcvpq.back (); + rcvpq.pop_back (); + } + + for (int i = vpn->dns_sndpq.size (); i--; ) + if (vpn->dns_sndpq [i]->dns == this) + { + vpn->dns_sndpq [i] = vpn->dns_sndpq.back (); + vpn->dns_sndpq.pop_back (); + } + established = false; rcvseq = repseq = sndseq = 0; @@ -752,15 +838,14 @@ min_latency = INITIAL_TIMEOUT; } -dns_connection::~dns_connection () +void +dns_connection::set_cfg () { - for (vector::iterator i = rcvpq.begin (); - i != rcvpq.end (); - ++i) - delete *i; + cdc = cfg.req_cdc == 36 ? &cdc36 : &cdc62; } -void dns_connection::receive_rep (dns_rcv *r) +void +dns_connection::receive_rep (dns_rcv *r) { if (r->datalen) { @@ -803,8 +888,10 @@ if (!rcvdq.put (r->data, r->datalen)) { - slog (L_ERR, "DNS: !rcvdq.put (r->data, r->datalen)"); - abort (); // MUST never overflow, can be caused by data corruption, TODO + // MUST never overflow, can be caused by data corruption, TODO + slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)"); + reset (); + return; } while (vpn_packet *pkt = rcvdq.get ()) @@ -813,7 +900,6 @@ si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4; vpn->recv_vpn_packet (pkt, si); - delete pkt; } @@ -866,9 +952,6 @@ int client, seqno; decode_header (qname, client, seqno); - u8 data[MAXSIZE]; - int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE)); - if (0 < client && client <= conns.size ()) { connection *c = conns [client - 1]; @@ -877,6 +960,9 @@ if (dns) { + u8 data[MAXSIZE]; + int datalen = dns->cdc->decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE)); + for (vector::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); ) if (SEQNO_EQ ((*i)->seqno, seqno)) { @@ -987,8 +1073,6 @@ pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL pkt [offs++] = 0; pkt [offs++] = 4; // rdlength - slog (L_INFO, _("DNS: client %d connects"), client); - pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; pkt [offs++] = CMD_IP_REJ; @@ -998,11 +1082,20 @@ if (cfg.valid ()) { - pkt [offs - 1] = CMD_IP_SYN; + slog (L_INFO, _("DNS: client %d connects (version %d, req_cdc %d)"), client, cfg.version, cfg.req_cdc); + + // check for any encoding mismatches - hints at a case problem + char qname2 [MAX_ENC_LEN]; + cdc26.encode (qname2, (u8 *)&cfg, sizeof (dns_cfg)); delete c->dns; + + pkt [offs - 1] = memcmp (qname, qname2, cdc26.encode_len (sizeof (dns_cfg))) + ? CMD_IP_CSE : CMD_IP_SYN; + c->dns = new dns_connection (c); c->dns->cfg = cfg; + c->dns->set_cfg (); } } } @@ -1032,8 +1125,9 @@ int seqno = (*i)->seqno; u8 data[MAXSIZE], *datap = data; //printf ("rcv pkt %x\n", seqno);//D + bool back_off = (*i)->retry; - if ((*i)->retry) + if (back_off) { dns->send_interval *= 1.01; if (dns->send_interval > MAX_SEND_INTERVAL) @@ -1083,7 +1177,7 @@ ttl |= pkt [offs++]; u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++]; - if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT) + if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype) { if (rdlen <= MAXSIZE - offs) { @@ -1119,10 +1213,9 @@ if (ip [3] == CMD_IP_RST) { - slog (L_DEBUG, _("DNS: got tunnel RST request")); - - delete dns; c->dns = 0; + slog (L_DEBUG, _("DNS: got tunnel RST request.")); + dns->reset (); return; } else if (ip [3] == CMD_IP_SYN) @@ -1130,13 +1223,31 @@ slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us.")); dns->established = true; } + else if (ip [3] == CMD_IP_CSE) + { + if (conf.dns_case_preserving) + { + slog (L_INFO, _("DNS: got tunnel CSE reply, globally downgrading to case-insensitive protocol.")); + conf.dns_case_preserving = false; + dns->reset (); + return; + } + else + { + slog (L_DEBUG, _("DNS: got tunnel CSE reply, server likes us.")); + dns->established = true; + } + } else if (ip [3] == CMD_IP_REJ) { - slog (L_DEBUG, _("DNS: got tunnel REJ reply, server does not like us, aborting.")); - abort (); + slog (L_ERR, _("DNS: got tunnel REJ reply, server does not like us.")); + dns->tw.start (60.); } else - slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]); + { + slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]); + dns->tw.start (60.); + } } else slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"), @@ -1164,6 +1275,16 @@ // todo: pkt now used if (datap) dns->receive_rep (new dns_rcv (seqno, data, datap - data)); + else if (dns_sndpq.empty ()) // no data received, and nothing to send - idle + { + dns->send_interval *= 1.1; + + if (dns->send_interval < MIN_POLL_INTERVAL) + dns->send_interval = MIN_POLL_INTERVAL; + + if (dns->send_interval > MAX_POLL_INTERVAL && !back_off) + dns->send_interval = MAX_POLL_INTERVAL; + } break; } @@ -1214,12 +1335,6 @@ return true; } -void -connection::dnsv4_reset_connection () -{ - //delete dns; dns = 0; //TODO -} - #define NEXT(w) do { if (next > (w)) next = w; } while (0) void @@ -1270,6 +1385,7 @@ send = new dns_snd (this); cfg.reset (THISNODE->id); + set_cfg (); send->gen_syn_req (); } }