--- gvpe/src/vpn_dns.C 2005/03/01 04:38:21 1.2 +++ gvpe/src/vpn_dns.C 2007/12/06 00:35:29 1.46 @@ -1,8 +1,10 @@ /* vpn_dns.C -- handle the dns tunnel part of the protocol. - Copyright (C) 2003-2004 Marc Lehmann + Copyright (C) 2003-2005 Marc Lehmann - This program is free software; you can redistribute it and/or modify + This file is part of GVPE. + + GVPE is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. @@ -13,10 +15,14 @@ GNU General Public License for more details. You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + along with gvpe; if not, write to the Free Software + Foundation, Inc. 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ +// TODO: EDNS0 option to increase dns mtu? +// TODO: re-write dns packet parsing/creation using a safe mem-buffer +// to ensure no buffer overflows or similar problems. + #include "config.h" #if ENABLE_DNS @@ -25,6 +31,7 @@ // it's a hack, use only in emergency situations please. #include +#include #include #include @@ -37,120 +44,360 @@ #include +#include /* bug in libgmp: gmp.h relies on cstdio being included */ +#include + #include "netcompat.h" #include "vpn.h" -#if ENABLE_HTTP_PROXY -# include "conf.h" -#endif +#define MAX_POLL_INTERVAL 5. // how often to poll minimally when the server has no data +#define ACTIVITY_INTERVAL 5. -#define MIN_RETRY 1. -#define MAX_RETRY 60. +#define INITIAL_TIMEOUT 0.1 // retry timeouts +#define INITIAL_SYN_TIMEOUT 2. // retry timeout for initial syn -#define SERVER conf.dns_port +#define MAX_SEND_INTERVAL 2. // optimistic? -/* +#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog +#define MAX_BACKLOG (64*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE -protocol, in shorthand :) +#define MAX_DOMAIN_SIZE 240 // 255 is legal limit, but bind doesn't compress well +// 240 leaves about 4 bytes of server reply data +// every request byte less give room for two reply bytes -client -> server ANY? -server -> client TXT +#define SEQNO_MASK 0x3fff +#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) ) - is dns64-encoded [] - is dns64-encoded <0:12>[] +#define MAX_LBL_SIZE 63 +#define MAX_PKT_SIZE 512 -if is zero, the connection will be configured: +#define RR_TYPE_A 1 +#define RR_TYPE_NULL 10 +#define RR_TYPE_TXT 16 +#define RR_TYPE_ANY 255 -<0:12><0:4>client-id:12> +#define RR_CLASS_IN 1 -*/ +#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 MAX_LBL_SIZE 63 -#define MAX_PKT_SIZE 512 +// works for cmaps up to 255 (not 256!) +struct charmap +{ + enum { INVALID = (u8)255 }; -#define RR_TYPE_TXT 16 -#define RR_TYPE_ANY 255 -#define RR_CLASS_IN 1 + char encode [256]; // index => char + u8 decode [256]; // char => index + unsigned int size; -// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative) -struct dns64 + charmap (const char *cmap); +}; + +charmap::charmap (const char *cmap) { - static const char encode_chars[64 + 1]; - static s8 decode_chars[256]; + char *enc = encode; + u8 *dec = decode; + + memset (enc, (char) 0, 256); + memset (dec, (char)INVALID, 256); - static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; } - static int decode_len (int bytes) { return (bytes * 6) / 8; } - static void encode (char *dst, u8 *src, int len); - static void decode (u8 *dst, char *src, int len); + for (size = 0; cmap [size]; size++) + { + enc [size] = cmap [size]; + dec [(u8)enc [size]] = size; + } - dns64 (); -} dns64; + assert (size < 256); +} -const char dns64::encode_chars[64 + 1] = "0123456789-abcdefghijklmnopqrstuvwxyz_ABCDEFGHIJKLMNOPQRSTUVWXYZ"; -s8 dns64::decode_chars[256]; +#define MAX_DEC_LEN 500 +#define MAX_ENC_LEN (MAX_DEC_LEN * 2) +#define MAX_LIMBS ((MAX_DEC_LEN * 8 + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS) -dns64::dns64 () +// ugly. minimum base is 16(!) +struct basecoder { - for (int i = 0; i < 64; i++) - decode_chars [encode_chars [i]] = i + 1; + charmap cmap; + 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 (char *dst, u8 *src, unsigned int len); + unsigned int decode (u8 *dst, char *src, unsigned int len); + + basecoder (const char *cmap); +}; + +basecoder::basecoder (const char *cmap) +: cmap (cmap) +{ + for (unsigned int len = 0; len < MAX_DEC_LEN; ++len) + { + u8 src [MAX_DEC_LEN]; + u8 dst [MAX_ENC_LEN]; + + memset (src, 255, len); + + mp_limb_t m [MAX_LIMBS]; + mp_size_t n; + + n = mpn_set_str (m, src, len, 256); + n = mpn_get_str (dst, this->cmap.size, m, n); + + for (int i = 0; !dst [i]; ++i) + n--; + + enc_len [len] = n; + dec_len [n] = len; + } } -void dns64::encode (char *dst, u8 *src, int len) +unsigned int basecoder::encode_len (unsigned int len) { - // slow, but easy to debug - unsigned int accum, bits = 0; + return enc_len [len]; +} - while (len--) - { - accum <<= 8; - accum |= *src++; - bits += 8; +unsigned int basecoder::decode_len (unsigned int len) +{ + while (len && !dec_len [len]) + --len; - while (bits >= 6) - { - *dst++ = encode_chars [(accum >> (bits - 6)) & 63]; - bits -= 6; - } + return dec_len [len]; +} + +unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len) +{ + if (!len || len > MAX_DEC_LEN) + return 0; + + int elen = encode_len (len); + + mp_limb_t m [MAX_LIMBS]; + mp_size_t n; + + u8 dst_ [MAX_ENC_LEN]; + + n = mpn_set_str (m, src, len, 256); + n = mpn_get_str (dst_, cmap.size, m, n); + + int plen = elen; // for padding + + while (n < plen) + { + *dst++ = cmap.encode [0]; + plen--; } - if (bits) - *dst++ = encode_chars [(accum << (6 - bits)) & 63]; + for (unsigned int i = n - plen; i < n; ++i) + *dst++ = cmap.encode [dst_ [i]]; + + return elen; } -void dns64::decode (u8 *dst, char *src, int len) +unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len) { - // slow, but easy to debug - unsigned int accum, bits = 0; + if (!len || len > MAX_ENC_LEN) + return 0; + + u8 src_ [MAX_ENC_LEN]; + unsigned int elen = 0; while (len--) { - s8 chr = decode_chars [(u8)*src++]; + u8 val = cmap.decode [(u8)*src++]; + + if (val != charmap::INVALID) + src_ [elen++] = val; + } + int dlen = decode_len (elen); - if (!chr) - break; + mp_limb_t m [MAX_LIMBS]; + mp_size_t n; - accum <<= 6; - accum |= chr - 1; - bits += 6; + u8 dst_ [MAX_DEC_LEN]; - while (bits >= 8) - { - *dst++ = accum >> (bits - 8); - bits -= 8; - } + n = mpn_set_str (m, src_, elen, cmap.size); + n = mpn_get_str (dst_, 256, m, n); + + if (n < dlen) + { + memset (dst, 0, dlen - n); + memcpy (dst + dlen - n, dst_, n); } + else + memcpy (dst, dst_ + n - dlen, dlen); + + return dlen; +} + +#if 0 +struct test { test (); } test; + +test::test () +{ + basecoder cdc ("0123456789abcdefghijklmnopqrstuvwxyz"); + + u8 in[] = "0123456789abcdefghijklmnopqrstuvwxyz"; + static char enc[200]; + static u8 dec[200]; + + for (int i = 1; i < 20; i++) + { + int elen = cdc.encode (enc, in, i); + int dlen = cdc.decode (dec, enc, elen); + + printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec); + } + abort (); +} +#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"); + +///////////////////////////////////////////////////////////////////////////// + +#define HDRSIZE 6 + +inline void encode_header (char *data, int clientid, int seqno, int retry = 0) +{ + seqno &= SEQNO_MASK; + + u8 hdr[3] = { + clientid, + (seqno >> 8) | (retry << 6), + seqno, + }; + + assert (clientid < 256); + + cdc26.encode (data, hdr, 3); +} + +inline void decode_header (char *data, int &clientid, int &seqno) +{ + u8 hdr[3]; + + cdc26.decode (hdr, data, HDRSIZE); + + clientid = hdr[0]; + seqno = ((hdr[1] << 8) | hdr[2]) & SEQNO_MASK; } +///////////////////////////////////////////////////////////////////////////// + +struct byte_stream +{ + u8 *data; + int maxsize; + int fill; + + byte_stream (int maxsize); + ~byte_stream (); + + bool empty () { return !fill; } + int size () { return fill; } + + bool put (u8 *data, unsigned int datalen); + bool put (vpn_packet *pkt); + vpn_packet *get (); + + u8 *begin () { return data; } + void remove (int count); +}; + +byte_stream::byte_stream (int maxsize) +: maxsize (maxsize), fill (0) +{ + data = new u8 [maxsize]; +} + +byte_stream::~byte_stream () +{ + delete data; +} + +void byte_stream::remove (int count) +{ + if (count > fill) + assert (count <= fill); + + memmove (data, data + count, fill -= count); +} + +bool byte_stream::put (u8 *data, unsigned int datalen) +{ + if (maxsize - fill < datalen) + return false; + + memcpy (this->data + fill, data, datalen); fill += datalen; + + return true; +} + +bool byte_stream::put (vpn_packet *pkt) +{ + if (maxsize - fill < pkt->len + 2) + return false; + + data [fill++] = pkt->len >> 8; + data [fill++] = pkt->len; + + memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len; + + return true; +} + +vpn_packet *byte_stream::get () +{ + unsigned int len; + + for (;;) + { + len = (data [0] << 8) | data [1]; + + if (len <= MAXSIZE || fill < 2) + break; + + // TODO: handle this better than skipping, e.g. by reset + slog (L_DEBUG, _("DNS: corrupted packet stream skipping a byte...")); + remove (1); + } + + if (fill < len + 2) + return 0; + + vpn_packet *pkt = new vpn_packet; + + pkt->len = len; + memcpy (pkt->at (0), data + 2, len); + remove (len + 2); + + return pkt; +} + +///////////////////////////////////////////////////////////////////////////// + #define FLAG_QUERY ( 0 << 15) #define FLAG_RESPONSE ( 1 << 15) -#define FLAG_OP_MASK (15 << 14) +#define FLAG_OP_MASK (15 << 11) #define FLAG_OP_QUERY ( 0 << 11) #define FLAG_AA ( 1 << 10) #define FLAG_TC ( 1 << 9) #define FLAG_RD ( 1 << 8) #define FLAG_RA ( 1 << 7) +#define FLAG_AUTH ( 1 << 5) #define FLAG_RCODE_MASK (15 << 0) #define FLAG_RCODE_OK ( 0 << 0) #define FLAG_RCODE_FORMERR ( 1 << 0) @@ -159,7 +406,75 @@ #define FLAG_RCODE_REFUSED ( 5 << 0) #define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) -#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD) +#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA) + +struct dns_cfg +{ + static int next_uid; + + u8 id1, id2, id3, id4; + + u8 version; + u8 flags; + u8 rrtype; + u8 def_ttl; + + u16 client; + u16 uid; // to make request unique + + u16 max_size; + u8 seq_cdc; + u8 req_cdc; + + u8 rep_cdc; + u8 delay; // time in 0.01s units that the server may delay replying packets + u8 r3, r4; + + u8 r5, r6, r7, r8; + + void reset (int clientid); + bool valid (); +}; + +int dns_cfg::next_uid; + +void dns_cfg::reset (int clientid) +{ + id1 = 'G'; + id2 = 'V'; + id3 = 'P'; + id4 = 'E'; + + version = 1; + + rrtype = RR_TYPE_TXT; + flags = 0; + def_ttl = 0; + seq_cdc = 26; + req_cdc = 62; + rep_cdc = 0; + max_size = htons (MAX_PKT_SIZE); + client = htons (clientid); + uid = next_uid++; + delay = 0; + + r3 = r4 = 0; + r4 = r5 = r6 = r7 = 0; +} + +bool dns_cfg::valid () +{ + // although the protocol itself allows for some configurability, + // only the following encoding/decoding settings are implemented. + return id1 == 'G' + && id2 == 'V' + && id3 == 'P' + && id4 == 'E' + && seq_cdc == 26 + && req_cdc == 62 + && rep_cdc == 0 + && version == 1; +} struct dns_packet : net_packet { @@ -167,7 +482,7 @@ u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4 u16 qdcount, ancount, nscount, arcount; - u8 data[MAXSIZE - 6 * 2]; + u8 data [MAXSIZE - 6 * 2]; int decode_label (char *data, int size, int &offs); }; @@ -206,100 +521,666 @@ return data - orig; } -struct dns_cfg +///////////////////////////////////////////////////////////////////////////// + +static u16 dns_id = 0; // TODO: should be per-vpn + +static u16 next_id () { - u8 id1, id2, id3; - u8 def_ttl; - u8 unused1; - u16 max_size; - u8 flags1, flags2; + if (!dns_id) + dns_id = time (0); + + // the simplest lsfr with periodicity 65535 i could find + dns_id = (dns_id << 1) + | (((dns_id >> 1) + ^ (dns_id >> 2) + ^ (dns_id >> 4) + ^ (dns_id >> 15)) & 1); + + return dns_id; +} + +struct dns_rcv; +struct dns_snd; + +struct dns_connection +{ + connection *c; + struct vpn *vpn; + + dns_cfg cfg; + + bool established; + + tstamp last_received; + tstamp last_sent; + double min_latency; + double poll_interval, send_interval; + + vector rcvpq; + + byte_stream rcvdq; int rcvseq; int repseq; + byte_stream snddq; int sndseq; + + inline void time_cb (ev::timer &w, int revents); ev::timer tw; + void receive_rep (dns_rcv *r); + + dns_connection (connection *c); + ~dns_connection (); }; -// reply to client-poll -void dnsv4_poll (dns_packet *pkt, int &offs) +struct dns_snd { - int dlen = MAX_PKT_SIZE - offs - 2; + dns_packet *pkt; + tstamp timeout, sent; + int retry; + struct dns_connection *dns; + int seqno; + bool stdhdr; + + void gen_stream_req (int seqno, byte_stream &stream); + void gen_syn_req (); - (*pkt) [offs++] = 0; - (*pkt) [offs++] = 5; - memcpy (&((*pkt)[offs]), "\01H\02\xff\x00", 5); - offs += 5; + dns_snd (dns_connection *dns); + ~dns_snd (); +}; + +dns_snd::dns_snd (dns_connection *dns) +: dns (dns) +{ + timeout = 0; + retry = 0; + seqno = 0; + sent = ev_now (); + stdhdr = false; - pkt->ancount = htons (1); - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); + pkt = new dns_packet; - printf ("we have room for %d bytes\n", dlen); + pkt->id = next_id (); } -void -vpn::dnsv4_ev (io_watcher &w, short revents) +dns_snd::~dns_snd () { - if (revents & EVENT_READ) + delete pkt; +} + +static void append_domain (dns_packet &pkt, int &offs, const char *domain) +{ + // add tunnel domain + for (;;) { - dns_packet *pkt = new dns_packet; - struct sockaddr_in sa; - socklen_t sa_len = sizeof (sa); + const char *end = strchr (domain, '.'); - int len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); - pkt->len = len; + if (!end) + end = domain + strlen (domain); - u16 flags = ntohs (pkt->flags); + int len = end - domain; - if (THISNODE->dns_port) - { - // server - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); + pkt [offs++] = len; + memcpy (pkt.at (offs), domain, len); + offs += len; + + if (!*end) + break; + + domain = end + 1; + } +} + +void dns_snd::gen_stream_req (int seqno, byte_stream &stream) +{ + stdhdr = true; + this->seqno = seqno; + + timeout = ev_now () + INITIAL_TIMEOUT; + + pkt->flags = htons (DEFAULT_CLIENT_FLAGS); + pkt->qdcount = htons (1); + + int offs = 6*2; + int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2); + // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well, + // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra + + 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); + + if (datalen > stream.size ()) + datalen = stream.size (); + + int enclen = cdc62.encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE; + stream.remove (datalen); + + while (enclen) + { + int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; + + (*pkt)[offs++] = lbllen; + memcpy (pkt->at (offs), encp, lbllen); + + offs += lbllen; + encp += lbllen; + + enclen -= lbllen; + } + + append_domain (*pkt, offs, dns->c->conf->domain); + + (*pkt)[offs++] = 0; + (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; + (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; + + pkt->len = offs; +} + +void dns_snd::gen_syn_req () +{ + timeout = ev_now () + INITIAL_SYN_TIMEOUT; + + pkt->flags = htons (DEFAULT_CLIENT_FLAGS); + pkt->qdcount = htons (1); + + int offs = 6 * 2; + + int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg)); + + assert (elen <= MAX_LBL_SIZE); + + (*pkt)[offs] = elen; + offs += elen + 1; + append_domain (*pkt, offs, dns->c->conf->domain); + + (*pkt)[offs++] = 0; + (*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A; + (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; + + pkt->len = offs; +} - int offs = 6 * 2; // skip header +struct dns_rcv +{ + int seqno; + dns_packet *pkt; // reply packet + u8 data [MAXSIZE]; // actually part of the reply packet... + int datalen; + + dns_rcv (int seqno, u8 *data, int datalen); + ~dns_rcv (); +}; + +dns_rcv::dns_rcv (int seqno, u8 *data, int datalen) +: seqno (seqno), pkt (new dns_packet), datalen (datalen) +{ + memcpy (this->data, data, datalen); +} + +dns_rcv::~dns_rcv () +{ + delete pkt; +} + +///////////////////////////////////////////////////////////////////////////// + +dns_connection::dns_connection (connection *c) +: c (c) +, rcvdq (MAX_BACKLOG * 2) +, snddq (MAX_BACKLOG) +{ + tw.set (this); + + vpn = c->vpn; + + established = false; + + rcvseq = repseq = sndseq = 0; + + last_sent = last_received = 0; + poll_interval = 0.5; // starting here + send_interval = 0.5; // starting rate + min_latency = INITIAL_TIMEOUT; +} + +dns_connection::~dns_connection () +{ + for (vector::iterator i = rcvpq.begin (); + i != rcvpq.end (); + ++i) + delete *i; +} + +void dns_connection::receive_rep (dns_rcv *r) +{ + if (r->datalen) + { + last_received = ev_now (); + tw (); + + poll_interval = send_interval; + } + else + { + poll_interval *= 1.5; + + if (poll_interval > MAX_POLL_INTERVAL) + poll_interval = MAX_POLL_INTERVAL; + } + + rcvpq.push_back (r); + + redo: - if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) - && pkt->qdcount == htons (1)) + // find next packet + for (vector::iterator i = rcvpq.end (); i-- != rcvpq.begin (); ) + if (SEQNO_EQ (rcvseq, (*i)->seqno)) + { + //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D + // enter the packet into our input stream + r = *i; + + // remove the oldest packet, look forward, as it's oldest first + for (vector::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j) + if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW)) { - char qname[MAXSIZE]; - int qlen = pkt->decode_label ((char *)qname, MAXSIZE, offs); + //printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D + delete *j; + rcvpq.erase (j); + break; + } + + rcvseq = (rcvseq + 1) & SEQNO_MASK; - printf ("rcvd packet len %d, id%04x flags%04x q%04x a%04x n%04x a%04x <%s>\n", len, - pkt->id, flags, pkt->qdcount, pkt->ancount, pkt->nscount, pkt->arcount, qname);//D + 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 + } + + while (vpn_packet *pkt = rcvdq.get ()) + { + sockinfo si; + si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4; + + vpn->recv_vpn_packet (pkt, si); + + delete pkt; + } + + // check for further packets + goto redo; + } +} - u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; - u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; +void +vpn::dnsv4_server (dns_packet &pkt) +{ + u16 flags = ntohs (pkt.flags); - pkt->qdcount = htons (1); - pkt->ancount = 0; - pkt->nscount = 0; // should be self, as other nameservers reply like this - pkt->arcount = 0; // a record for self, as other nameservers reply like this + int offs = 6 * 2; // skip header - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); - int dlen = strlen (THISNODE->domain); + if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK)) + && pkt.qdcount == htons (1)) + { + char qname [MAXSIZE]; + int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); - if (qclass == RR_CLASS_IN - && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT) - && qlen > dlen + 1 - && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) - { - // correct class, now generate reply - pkt->ancount = htons (1); // one answer RR + u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++]; + u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++]; - (*pkt) [offs++] = 0xc0; - (*pkt) [offs++] = 6 * 2; // same as in query section + pkt.qdcount = htons (1); + pkt.ancount = 0; + pkt.nscount = 0; // should be self, as other nameservers reply like this + pkt.arcount = 0; // a record for self, as other nameservers reply like this + + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL); + + int dlen = strlen (THISNODE->domain); + + if (qclass == RR_CLASS_IN + && qlen > dlen + 1 + && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen)) + { + // now generate reply + pkt.ancount = htons (1); // one answer RR + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); + + if ((qtype == RR_TYPE_ANY + || qtype == RR_TYPE_TXT + || qtype == RR_TYPE_NULL) + && qlen > dlen + 1 + HDRSIZE) + { + // correct class, domain: parse + int client, seqno; + decode_header (qname, client, seqno); - (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; - (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; + u8 data[MAXSIZE]; + int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE)); - (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; - (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL + if (0 < client && client <= conns.size ()) + { + connection *c = conns [client - 1]; + dns_connection *dns = c->dns; + dns_rcv *rcv; + + if (dns) + { + for (vector::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); ) + if (SEQNO_EQ ((*i)->seqno, seqno)) + { + // already seen that request: simply reply with the cached reply + dns_rcv *r = *i; + + slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno); + + // refresh header & id, as the retry count could have changed + memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE); + r->pkt->id = pkt.id; + + memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len); + + goto duplicate_request; + } + + // new packet, queue + rcv = new dns_rcv (seqno, data, datalen); + dns->receive_rep (rcv); + } + + { + pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section + + int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A; + pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type + pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class + pkt [offs++] = 0; pkt [offs++] = 0; + pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL + + int rdlen_offs = offs += 2; + + if (dns) + { + int dlen = ntohs (dns->cfg.max_size) - offs; + + // bind doesn't compress well, so reduce further by one label length + dlen -= qlen; + + // only put data into in-order sequence packets, if + // we receive out-of-order packets we generate empty + // replies + //printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D + if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW) + { + dns->repseq = seqno; + + while (dlen > 1 && !dns->snddq.empty ()) + { + int txtlen = dlen <= 255 ? dlen - 1 : 255; + + if (txtlen > dns->snddq.size ()) + txtlen = dns->snddq.size (); + + pkt[offs++] = txtlen; + memcpy (pkt.at (offs), dns->snddq.begin (), txtlen); + offs += txtlen; + dns->snddq.remove (txtlen); + + dlen -= txtlen + 1; + } + } + + // avoid completely empty TXT rdata + if (offs == rdlen_offs) + pkt[offs++] = 0; + + slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ()); + } + else + { + // send RST + pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; + pkt [offs++] = CMD_IP_RST; + } + + int rdlen = offs - rdlen_offs; + + pkt [rdlen_offs - 2] = rdlen >> 8; + pkt [rdlen_offs - 1] = rdlen; + + if (dns) + { + // now update dns_rcv copy + rcv->pkt->len = offs; + memcpy (rcv->pkt->at (0), pkt.at (0), offs); + } + } - dnsv4_poll (pkt, offs); - printf ("correct class\n"); + duplicate_request: ; } + else + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); } + else if (qtype == RR_TYPE_A + && qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg))) + { + dns_cfg cfg; + cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg))); + int client = ntohs (cfg.client); + + pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section + + pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type + pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class + pkt [offs++] = 0; pkt [offs++] = 0; + pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL + pkt [offs++] = 0; pkt [offs++] = 4; // rdlength + + slog (L_INFO, _("DNS: client %d connects"), client); - sendto (w.fd, &((*pkt)[0]), offs, 0, (sockaddr *)&sa, sa_len); + pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; + pkt [offs++] = CMD_IP_REJ; + + if (0 < client && client <= conns.size ()) + { + connection *c = conns [client - 1]; + + if (cfg.valid ()) + { + pkt [offs - 1] = CMD_IP_SYN; + + delete c->dns; + c->dns = new dns_connection (c); + c->dns->cfg = cfg; + } + } + } } - else + + pkt.len = offs; + } +} + +void +vpn::dnsv4_client (dns_packet &pkt) +{ + u16 flags = ntohs (pkt.flags); + int offs = 6 * 2; // skip header + + pkt.qdcount = ntohs (pkt.qdcount); + pkt.ancount = ntohs (pkt.ancount); + + // go through our request list and find the corresponding request + for (vector::iterator i = dns_sndpq.begin (); + i != dns_sndpq.end (); + ++i) + if ((*i)->pkt->id == pkt.id) + { + dns_connection *dns = (*i)->dns; + connection *c = dns->c; + int seqno = (*i)->seqno; + u8 data[MAXSIZE], *datap = data; + //printf ("rcv pkt %x\n", seqno);//D + + if ((*i)->retry) + { + dns->send_interval *= 1.01; + if (dns->send_interval > MAX_SEND_INTERVAL) + dns->send_interval = MAX_SEND_INTERVAL; + } + else + { +#if 0 + dns->send_interval *= 0.999; +#endif + // the latency surely puts an upper bound on + // the minimum send interval + double latency = ev_now () - (*i)->sent; + + if (latency < dns->min_latency) + dns->min_latency = latency; + + if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor) + dns->send_interval = dns->min_latency * conf.dns_overlap_factor; + + if (dns->send_interval < conf.dns_send_interval) + dns->send_interval = conf.dns_send_interval; + } + + delete *i; + dns_sndpq.erase (i); + + if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK)) + { + char qname[MAXSIZE]; + + while (pkt.qdcount-- && offs < MAXSIZE - 4) + { + int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); + offs += 4; // skip qtype, qclass + } + + while (pkt.ancount-- && offs < MAXSIZE - 10 && datap) + { + int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); + + u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++]; + u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++]; + u32 ttl = pkt [offs++] << 24; + ttl |= pkt [offs++] << 16; + ttl |= pkt [offs++] << 8; + ttl |= pkt [offs++]; + u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++]; + + if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT) + { + if (rdlen <= MAXSIZE - offs) + { + // decode bytes, finally + + while (rdlen) + { + int txtlen = pkt [offs++]; + + assert (txtlen + offs < MAXSIZE - 1); + + memcpy (datap, pkt.at (offs), txtlen); + datap += txtlen; offs += txtlen; + + rdlen -= txtlen + 1; + } + } + } + else if (qtype == RR_TYPE_A) + { + u8 ip [4]; + + ip [0] = pkt [offs++]; + ip [1] = pkt [offs++]; + ip [2] = pkt [offs++]; + ip [3] = pkt [offs++]; + + if (ip [0] == CMD_IP_1 + && ip [1] == CMD_IP_2 + && ip [2] == CMD_IP_3) + { + slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]); + + if (ip [3] == CMD_IP_RST) + { + slog (L_DEBUG, _("DNS: got tunnel RST request")); + + delete dns; c->dns = 0; + + return; + } + else if (ip [3] == CMD_IP_SYN) + { + slog (L_DEBUG, _("DNS: got tunnel SYN 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 (); + } + else + slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]); + } + else + slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"), + ip [0], ip [1], ip [2], ip [3]); + + return; + } + + int client, rseqno; + decode_header (qname, client, rseqno); + + if (client != THISNODE->id) + { + slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring")); + datap = 0; + } + else if (rseqno != seqno) + { + slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?")); + datap = 0; + } + } + } + + // todo: pkt now used + if (datap) + dns->receive_rep (new dns_rcv (seqno, data, datap - data)); + + break; + } +} + +void +vpn::dnsv4_ev (ev::io &w, int revents) +{ + if (revents & EV_READ) + { + dns_packet *pkt = new dns_packet; + struct sockaddr_in sa; + socklen_t sa_len = sizeof (sa); + + pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); + + if (pkt->len > 0) { - // client + if (ntohs (pkt->flags) & FLAG_RESPONSE) + dnsv4_client (*pkt); + else + { + dnsv4_server (*pkt); + sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len); + } + + delete pkt; } } } @@ -307,7 +1188,127 @@ bool vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) { - //return i->send_packet (pkt, tos); + int client = ntohl (si.host); + + assert (0 < client && client <= conns.size ()); + + connection *c = conns [client - 1]; + + if (!c->dns) + c->dns = new dns_connection (c); + + if (c->dns->snddq.put (pkt)) + c->dns->tw (); + + // always return true even if the buffer overflows + return true; +} + +void +connection::dnsv4_reset_connection () +{ + //delete dns; dns = 0; //TODO +} + +#define NEXT(w) do { if (next > (w)) next = w; } while (0) + +void +dns_connection::time_cb (ev::timer &w, int revents) +{ + // servers have to be polled + if (THISNODE->dns_port) + return; + + // check for timeouts and (re)transmit + tstamp next = ev::now () + poll_interval; + dns_snd *send = 0; + + for (vector::iterator i = vpn->dns_sndpq.begin (); + i != vpn->dns_sndpq.end (); + ++i) + { + dns_snd *r = *i; + + if (r->timeout <= ev_now ()) + { + if (!send) + { + send = r; + + r->retry++; + r->timeout = ev_now () + (r->retry * min_latency * conf.dns_timeout_factor); + //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev_now ());//D + + // the following code changes the query section a bit, forcing + // the forwarder to generate a new request + if (r->stdhdr) + encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry); + } + } + else + NEXT (r->timeout); + } + + if (!send) + { + // generate a new packet, if wise + + if (!established) + { + if (vpn->dns_sndpq.empty ()) + { + send = new dns_snd (this); + + cfg.reset (THISNODE->id); + send->gen_syn_req (); + } + } + else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding + && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1))) + { + if (last_sent + send_interval <= ev_now ()) + { + //printf ("sending data request etc.\n"); //D + if (!snddq.empty () || last_received + 1. > ev_now ()) + { + poll_interval = send_interval; + NEXT (ev_now () + send_interval); + } + + send = new dns_snd (this); + send->gen_stream_req (sndseq, snddq); + send->timeout = ev_now () + min_latency * conf.dns_timeout_factor; + //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D + + sndseq = (sndseq + 1) & SEQNO_MASK; + } + else + NEXT (last_sent + send_interval); + } + + if (send) + vpn->dns_sndpq.push_back (send); + } + + if (send) + { + last_sent = ev_now (); + sendto (vpn->dnsv4_fd, + send->pkt->at (0), send->pkt->len, 0, + vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ()); + } + + slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)", + poll_interval, send_interval, next - ev_now (), + vpn->dns_sndpq.size (), snddq.size (), + rcvpq.size ()); + + // TODO: no idea when this happens, but when next < ev_now (), we have a problem + // doesn't seem to happen anymore + if (next < ev_now () + 0.001) + next = ev_now () + 0.1; + + w.start (next - ev_now ()); } #endif