mdw@git.distorted.org.uk Git - userv-utils/blob - ipif/forwarder.c

   1 /*
   2  * Encrypting tunnel for userv-ipif tunnels, actual core implementation
   3  */
   4 /*
   5  * usage:
   6  *  udptunnel-forwarder <optchars>
   7  *                      <public-local-fd> <private-in-fd> <private-out-fd>
   8  *                      <encdec-keys-fd>
   9  *                      <mtu> <keepalive> <timeout> <reannounce>
  10  *                      <public-remote-addr> [<public-remote-port>]
  11  *                      |<mech1> [<mech1-params> ...]
  12  *                      |<mech2> [<mech2-params> ...]
  13  *                      ''
  14  *
  15  * Remote addr may '' to mean wait to receive a packet and reply to
  16  * whereever we get a good packet from first, in which case port
  17  * should not be specified.
  18  *
  19  * <optchars> is zero or more of
  20  *    w   means generate and write encdec keys, rather than reading them
  21  *    K   means do crypto debug (use with care!)
  22  *
  23  * encdec keys datastream has keys for packets from key datastream
  24  * writer to reader first, then keys for packets from reader to
  25  * writer.
  26  *
  27  * Every addr or port must be numeric.  There is very little argument checking.
  28  *
  29  * Exit status:
  30  *  SIGALARM   timed out
  31  *       0     terminated due to outbound packet stream EOF
  32  *       4     other error
  33  *       8     system problem
  34  *      12     usage error
  35  *      16     bad trouble
  36  */
  37 /*
  38  * This file is part of ipif, part of userv-utils
  39  *
  40  * Copyright 1996-2013 Ian Jackson <ijackson@chiark.greenend.org.uk>
  41  * Copyright 1998 David Damerell <damerell@chiark.greenend.org.uk>
  42  * Copyright 1999,2003
  43  *    Chancellor Masters and Scholars of the University of Cambridge
  44  * Copyright 2010 Tony Finch <fanf@dotat.at>
  45  *
  46  * This is free software; you can redistribute it and/or modify it
  47  * under the terms of the GNU General Public License as published by
  48  * the Free Software Foundation; either version 3 of the License, or
  49  * (at your option) any later version.
  50  *
  51  * This program is distributed in the hope that it will be useful, but
  52  * WITHOUT ANY WARRANTY; without even the implied warranty of
  53  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  54  * General Public License for more details.
  55  *
  56  * You should have received a copy of the GNU General Public License
  57  * along with userv-utils; if not, see http://www.gnu.org/licenses/.
  58  */
  59
  60 #include <sys/socket.h>
  61 #include <netinet/in.h>
  62 #include <arpa/inet.h>
  63 #include <sys/utsname.h>
  64 #include <sys/poll.h>
  65
  66 #include <string.h>
  67 #include <errno.h>
  68 #include <assert.h>
  69 #include <stdlib.h>
  70
  71 #include <unistd.h>
  72 #include <fcntl.h>
  73
  74 #include "forwarder.h"
  75
  76 #define MAXMECHS 10
  77
  78 static size_t buffer_size;
  79 static struct utsname uname_result;
  80
  81 static const char *opt_chars;
  82 static int public_local_fd, private_in_fd, private_out_fd;
  83 static int mtu2, keepalive, timeout, reannounce;
  84 static int public_remote_specd;
  85 static struct sockaddr_in public_remote;
  86 static int encdec_keys_fd, encdec_keys_write, crypto_debug;
  87 static int n_mechs;
  88 static const struct mechanism *mechs[MAXMECHS];
  89
  90 static struct mechdata *md_in[MAXMECHS], *md_out[MAXMECHS];
  91 static int maxprefix, maxsuffix;
  92
  93 static struct buffer buf_in, buf_out;
  94 static unsigned char *accum_buf;
  95 static size_t accum_used, accum_avail;
  96
  97 static time_t nextsendka;
  98
  99 static void cdebug(int mechno /*or -1*/, const char *msg) {
 100   if (!crypto_debug) return;
 101   printf("%-8.8s: CRYPTO: %-20s %s\n",
 102          uname_result.nodename,
 103          mechno >= 0 ? mechs[mechno]->name : "",
 104          msg);
 105 }
 106
 107 static void cdebughex(int mechno /*or -1*/, const char *msg, const void *ptr,
 108                       size_t sz, size_t skipbefore,
 109                       int spc_offset, int dot_offset) {
 110   const unsigned char *p;
 111   size_t i;
 112   unsigned j= dot_offset;
 113
 114   if (!crypto_debug) return;
 115   printf("%-8.8s: CRYPTO: %-20s %-10s",
 116          uname_result.nodename,
 117          mechno >= 0 ? mechs[mechno]->name : "",
 118          msg);
 119
 120   for (i=0; i<spc_offset; i++, j++) fputs(j&3 ? "  " : "   ",stdout);
 121   for (i=0; i<skipbefore; i++, j++) fputs(j&3 ? ".." : " ..",stdout);
 122   for (i=0, p=ptr; i<sz; i++, j++, p++) printf(j&3 ? "%02x" : " %02x",*p);
 123
 124   fputc('\n',stdout);
 125 }
 126
 127 static void cdebugbuf(int mechno /*or -1*/, const char *msg,
 128                       const struct buffer *buf, int spc_offset, int dot_offset) {
 129   cdebughex(mechno, msg, buf->start, buf->size, buf->start - buf->base,
 130             spc_offset, dot_offset);
 131 }
 132
 133 void get_random(void *ptr, size_t sz) {
 134   static FILE *randfile;
 135
 136   size_t r;
 137
 138   if (!randfile) {
 139     randfile= fopen("/dev/urandom","rb");
 140     if (!randfile && errno==ENOENT) randfile= fopen("/dev/random","rb");
 141     if (!randfile) sysfail("open random number generator");
 142   }
 143
 144   r= fread(ptr,1,sz,randfile);
 145   if (r != sz)
 146     (ferror(randfile) ? sysfail : fail)("cannot read random number generator");
 147
 148   cdebughex(-1, "get_random", ptr, sz, 0,0,0);
 149 }
 150
 151 void random_key(void *ptr, size_t sz) {
 152   if (encdec_keys_write) {
 153     get_random(ptr,sz);
 154     write_must(encdec_keys_fd,ptr,sz,"write keys datastream");
 155   } else {
 156     read_must(encdec_keys_fd,ptr,sz,"read keys datastream");
 157     cdebughex(-1, "random_key", ptr, sz, 0,0,0);
 158   }
 159 }
 160
 161
 162 static void setnonblock(int fd, int nonblock) {
 163   int r;
 164
 165   r= fcntl(fd,F_GETFL);
 166   if (r==-1) sysfail("fcntl F_GETFL");
 167   r= fcntl(fd,F_SETFL, nonblock ? r|O_NONBLOCK : r&~O_NONBLOCK);
 168   if (r==-1) sysfail("fcntl F_SETFL");
 169 }
 170
 171 static const struct mechanism *find_mech(const char *name) {
 172   const struct mechanism *mech, *const *mechlist;
 173
 174   for (mechlist= mechanismlists;
 175        *mechlist;
 176        mechlist++)
 177     for (mech= *mechlist; mech->name; mech++)
 178       if (!strcmp(mech->name,name)) return mech;
 179
 180   fprintf(stderr,"%s: unknown mechanism: %s\n",programid,name);
 181   exit(4);
 182 }
 183
 184 static void inbound(void) {
 185   static int any_recvd;
 186   static time_t nextreann;
 187   static unsigned long npackets, nbytes;
 188
 189   struct sockaddr_in this_saddr;
 190   size_t this_saddrlen;
 191   int r, i, different;
 192   const char *emsg;
 193
 194   buf_in.start= buf_in.base+1;
 195   buf_in.size= buffer_size-2;
 196
 197   setnonblock(public_local_fd,1);
 198   this_saddrlen= sizeof(this_saddr);
 199   r= recvfrom(public_local_fd, buf_in.start, buf_in.size, 0,
 200               &this_saddr, &this_saddrlen);
 201   if (!r) { diag("empty ciphertext"); return; }
 202
 203   if (r<0) {
 204     if (errno != EAGAIN && errno != EINTR) { sysdiag("receive"); sleep(1); }
 205     return;
 206   }
 207   if (this_saddr.sin_family != AF_INET) {
 208     fprintf(stderr,"%s: received unknown AF %lu\n",
 209             programid, (unsigned long)this_saddr.sin_family);
 210     return;
 211   }
 212   assert(this_saddrlen == sizeof(this_saddr));
 213
 214   assert(r <= buf_in.size);
 215   buf_in.size= r;
 216   cdebugbuf(-1, "decode", &buf_in, 3,0);
 217   for (i=n_mechs-1; i>=0; i--) {
 218     emsg= mechs[i]->decode(md_in[i],&buf_in);
 219     if (emsg) {
 220       if (*emsg)
 221         fprintf(stderr, "%s: bad packet: %s: %s\n",
 222                 programid, mechs[i]->name, emsg);
 223       else
 224         cdebug(i,"silently discarded");
 225       return;
 226     }
 227     cdebugbuf(i, "decode", &buf_in, 3,0);
 228   }
 229
 230   npackets++;
 231   nbytes += buf_in.size;
 232   alarm(timeout);
 233
 234   different= (!public_remote_specd ||
 235               public_remote.sin_addr.s_addr != this_saddr.sin_addr.s_addr ||
 236               public_remote.sin_port != this_saddr.sin_port);
 237
 238   if (different) {
 239
 240     if (public_remote_specd==2) {
 241       fprintf(stderr, "%s: packet from unexpected sender %s:%lu\n",
 242               programid, inet_ntoa(this_saddr.sin_addr),
 243               (unsigned long)ntohs(this_saddr.sin_port));
 244       return;
 245     }
 246
 247     fprintf(stderr, "%s: tunnel open with peer %s:%lu\n",
 248             programid, inet_ntoa(this_saddr.sin_addr),
 249             (unsigned long)ntohs(this_saddr.sin_port));
 250     nextsendka= now();
 251     public_remote_specd= 1;
 252     memcpy(&public_remote,&this_saddr,sizeof(public_remote));
 253
 254   } else if (!any_recvd) {
 255
 256     diag("tunnel open");
 257
 258   } else if (reannounce && now() >= nextreann) {
 259
 260     fprintf(stderr, "%s: tunnel still open: received %lu packets, %lu bytes\n",
 261             programid, npackets, nbytes);
 262
 263   } else {
 264
 265     goto no_set_reann; /* only reset this if we don't print a message. */
 266
 267   }
 268
 269   if (reannounce)
 270     nextreann= now() + reannounce;
 271
 272 no_set_reann:
 273
 274   any_recvd= 1;
 275
 276   if (!buf_in.size || *buf_in.start != 0300) {
 277     *--buf_in.start= 0300;
 278     buf_in.size++;
 279   }
 280   if (buf_in.start[buf_in.size-1] != 0300) {
 281     buf_in.start[buf_in.size++]= 0300;
 282   }
 283
 284   setnonblock(private_in_fd,0);
 285   write_must(private_in_fd, buf_in.start, buf_in.size, "write down");
 286 }
 287
 288 static void sendpacket(const unsigned char *message, size_t size) {
 289   int i, r;
 290
 291   buf_out.start= buf_out.base+maxprefix;
 292   buf_out.size= size;
 293   memcpy(buf_out.start, message, size);
 294
 295   nextsendka= now() + keepalive;
 296
 297   cdebugbuf(-1, "encode", &buf_out, 4,0);
 298   for (i=0; i<n_mechs; i++) {
 299     mechs[i]->encode(md_out[i],&buf_out);
 300     cdebugbuf(i, "encode", &buf_out, 4,0);
 301   }
 302   assert(public_remote_specd);
 303
 304   setnonblock(public_local_fd,1);
 305   for (;;) {
 306     r= sendto(public_local_fd, buf_out.start, buf_out.size, 0,
 307               &public_remote, sizeof(public_remote));
 308     if (r == buf_out.size) break;
 309     if (r >= 0) { diag("unexpected short send"); return; }
 310     if (errno != EINTR) { sysdiag("send"); return; }
 311   }
 312 }
 313
 314 static void outbound(void) {
 315   int r;
 316   unsigned char *after_eaten, *delim;
 317   size_t this_packet;
 318
 319   setnonblock(private_out_fd,1);
 320
 321   for (;;) {
 322     r= read(private_out_fd, accum_buf + accum_used, accum_avail - accum_used);
 323     if (!r) { diag("outbound datastream closed, quitting"); exit(0); }
 324     if (r<0) {
 325       if (errno == EAGAIN) return;
 326       if (errno == EINTR) continue;
 327     }
 328     accum_used += r;
 329     assert(accum_used<=accum_avail);
 330
 331     after_eaten= accum_buf;
 332     while ((delim= memchr(after_eaten, 0300, accum_used))) {
 333       this_packet= delim - after_eaten;
 334       if (this_packet) sendpacket(after_eaten, this_packet);
 335       accum_used -= this_packet+1;
 336       after_eaten = delim+1;
 337     }
 338     memmove(accum_buf, after_eaten, accum_used);
 339
 340     if (accum_used == accum_avail) {
 341       diag("missing interpacket delimiter in output datastream");
 342       accum_used= 0;
 343     }
 344   }
 345 }
 346
 347 int main(int argc, const char *const *const argv_in) {
 348   const char *arg;
 349   const char *const *argv_save;
 350   const char *const *argv_done;
 351   struct pollfd pollfds[2];
 352   int i, polltimeout, r;
 353   time_t tnow;
 354
 355   argv= argv_in;
 356
 357   if (uname(&uname_result)) { perror(PROGRAM ": uname failed"); exit(16); }
 358   sprintf(programid, PROGRAM ": %.*s", SYS_NMLN, uname_result.nodename);
 359
 360   opt_chars= getarg_string();
 361   encdec_keys_write= !!strchr(opt_chars,'w');
 362   crypto_debug= !!strchr(opt_chars,'K');
 363
 364   public_local_fd= getarg_ulong();
 365   private_in_fd= getarg_ulong();
 366   private_out_fd= getarg_ulong();
 367   encdec_keys_fd= getarg_ulong();
 368
 369   mtu2= getarg_ulong() * 2;
 370   keepalive= getarg_ulong();
 371   timeout= getarg_ulong();
 372   reannounce= getarg_ulong();
 373
 374   arg= getarg_string();
 375   if (*arg) {
 376     public_remote_specd= 1;
 377     public_remote.sin_family= AF_INET;
 378     arg_assert(inet_aton(arg,&public_remote.sin_addr));
 379     public_remote.sin_port= htons(getarg_ulong());
 380   }
 381
 382   if (crypto_debug) {
 383     diag("crypto debugging enabled!");
 384     setvbuf(stdout,0,_IOLBF,0);
 385   }
 386
 387   maxprefix= 0;
 388   i= 0;
 389   while ((arg= *++argv)) {
 390     arg_assert(*arg++ == '|');
 391     arg_assert(i <= MAXMECHS);
 392     mechs[i]= find_mech(arg);
 393
 394     cdebug(i,"writer->reader setup");
 395     argv_save= argv;
 396
 397     if (encdec_keys_write)
 398       mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix);
 399     else
 400       mechs[i]->decsetup(&md_in[i]);
 401
 402     argv_done= argv;
 403     argv= argv_save;
 404     cdebug(i,"reader->writer setup");
 405
 406     if (encdec_keys_write)
 407       mechs[i]->decsetup(&md_in[i]);
 408     else
 409       mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix);
 410
 411     assert(argv == argv_done);
 412
 413     i++;
 414   }
 415   n_mechs= i;
 416
 417   if (maxprefix<1) maxprefix= 1;
 418   if (maxsuffix<1) maxsuffix= 1;
 419   buffer_size= mtu2 + maxprefix + maxsuffix;
 420   buf_in.base= xmalloc(buffer_size);
 421   buf_out.base= xmalloc(buffer_size);
 422   accum_avail= mtu2 + 1;
 423   accum_buf= xmalloc(accum_avail);
 424
 425   alarm(timeout);
 426
 427   pollfds[0].fd= public_local_fd;
 428   pollfds[0].events= POLLIN;
 429   pollfds[1].fd= private_out_fd;
 430   for (;;) {
 431     pollfds[1].events= public_remote_specd ? POLLIN : 0;
 432     pollfds[0].revents= 0;
 433     pollfds[1].revents= 0;
 434
 435     if (keepalive) {
 436       tnow= now();
 437       if (tnow >= nextsendka && public_remote_specd)
 438         sendpacket((unsigned char*)"\300",1);
 439       polltimeout= (nextsendka - tnow)*1000;
 440     } else {
 441       polltimeout= -1;
 442     }
 443
 444     r= poll(pollfds,2,polltimeout);
 445     if (!r) continue;
 446     if (r==-1 && errno==EINTR) continue;
 447     if (r==-1) sysfail("poll");
 448
 449     if (pollfds[0].revents & (POLLIN|POLLERR)) inbound();
 450     if (pollfds[1].revents & (POLLIN|POLLERR)) outbound();
 451   }
 452 }