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  * Copyright (C) 2000,2003 Ian Jackson
  39  * This file is part of ipif, part of userv-utils
  40  *
  41  * This is free software; you can redistribute it and/or modify it
  42  * under the terms of the GNU General Public License as published by
  43  * the Free Software Foundation; either version 2 of the License, or
  44  * (at your option) any later version.
  45  *
  46  * This program is distributed in the hope that it will be useful, but
  47  * WITHOUT ANY WARRANTY; without even the implied warranty of
  48  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  49  * General Public License for more details.
  50  *
  51  * You should have received a copy of the GNU General Public License
  52  * along with userv-utils; if not, write to the Free Software
  53  * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  54  */
  55
  56 #include <sys/socket.h>
  57 #include <netinet/in.h>
  58 #include <arpa/inet.h>
  59 #include <sys/utsname.h>
  60 #include <sys/poll.h>
  61
  62 #include <string.h>
  63 #include <errno.h>
  64 #include <assert.h>
  65 #include <stdlib.h>
  66
  67 #include <unistd.h>
  68 #include <fcntl.h>
  69
  70 #include "forwarder.h"
  71
  72 #define MAXMECHS 10
  73
  74 static size_t buffer_size;
  75 static struct utsname uname_result;
  76
  77 static const char *opt_chars;
  78 static int public_local_fd, private_in_fd, private_out_fd;
  79 static int mtu2, keepalive, timeout, reannounce;
  80 static int public_remote_specd;
  81 static struct sockaddr_in public_remote;
  82 static int encdec_keys_fd, encdec_keys_write, crypto_debug;
  83 static int n_mechs;
  84 static const struct mechanism *mechs[MAXMECHS];
  85
  86 static struct mechdata *md_in[MAXMECHS], *md_out[MAXMECHS];
  87 static size_t maxprefix, maxsuffix;
  88
  89 static struct buffer buf_in, buf_out;
  90 static unsigned char *accum_buf;
  91 static size_t accum_used, accum_avail;
  92
  93 static time_t nextsendka;
  94
  95 static void cdebug(int mechno /*or -1*/, const char *msg) {
  96   if (!crypto_debug) return;
  97   printf("%-8.8s: CRYPTO: %-20s %s\n",
  98          uname_result.nodename,
  99          mechno >= 0 ? mechs[mechno]->name : "",
 100          msg);
 101 }
 102
 103 static void cdebughex(int mechno /*or -1*/, const char *msg, const void *ptr,
 104                       size_t sz, size_t skipbefore,
 105                       int spc_offset, int dot_offset) {
 106   const unsigned char *p;
 107   size_t i;
 108   unsigned j= dot_offset;
 109
 110   if (!crypto_debug) return;
 111   printf("%-8.8s: CRYPTO: %-20s %-10s",
 112          uname_result.nodename,
 113          mechno >= 0 ? mechs[mechno]->name : "",
 114          msg);
 115
 116   for (i=0; i<spc_offset; i++, j++) fputs(j&3 ? "  " : "   ",stdout);
 117   for (i=0; i<skipbefore; i++, j++) fputs(j&3 ? ".." : " ..",stdout);
 118   for (i=0, p=ptr; i<sz; i++, j++, p++) printf(j&3 ? "%02x" : " %02x",*p);
 119
 120   fputc('\n',stdout);
 121 }
 122
 123 static void cdebugbuf(int mechno /*or -1*/, const char *msg,
 124                       const struct buffer *buf, int spc_offset, int dot_offset) {
 125   cdebughex(mechno, msg, buf->start, buf->size, buf->start - buf->base,
 126             spc_offset, dot_offset);
 127 }
 128
 129 void get_random(void *ptr, size_t sz) {
 130   static FILE *randfile;
 131
 132   size_t r;
 133
 134   if (!randfile) {
 135     randfile= fopen("/dev/urandom","rb");
 136     if (!randfile && errno==ENOENT) randfile= fopen("/dev/random","rb");
 137     if (!randfile) sysfail("open random number generator");
 138   }
 139
 140   r= fread(ptr,1,sz,randfile);
 141   if (r != sz)
 142     (ferror(randfile) ? sysfail : fail)("cannot read random number generator");
 143
 144   cdebughex(-1, "get_random", ptr, sz, 0,0,0);
 145 }
 146
 147 void random_key(void *ptr, size_t sz) {
 148   if (encdec_keys_write) {
 149     get_random(ptr,sz);
 150     write_must(encdec_keys_fd,ptr,sz,"write keys datastream");
 151   } else {
 152     read_must(encdec_keys_fd,ptr,sz,"read keys datastream");
 153     cdebughex(-1, "random_key", ptr, sz, 0,0,0);
 154   }
 155 }
 156
 157
 158 static void setnonblock(int fd, int nonblock) {
 159   int r;
 160
 161   r= fcntl(fd,F_GETFL);
 162   if (r==-1) sysfail("fcntl F_GETFL");
 163   r= fcntl(fd,F_SETFL, nonblock ? r|O_NONBLOCK : r&~O_NONBLOCK);
 164   if (r==-1) sysfail("fcntl F_SETFL");
 165 }
 166
 167 static const struct mechanism *find_mech(const char *name) {
 168   const struct mechanism *mech, *const *mechlist;
 169
 170   for (mechlist= mechanismlists;
 171        *mechlist;
 172        mechlist++)
 173     for (mech= *mechlist; mech->name; mech++)
 174       if (!strcmp(mech->name,name)) return mech;
 175
 176   fprintf(stderr,"%s: unknown mechanism: %s\n",programid,name);
 177   exit(4);
 178 }
 179
 180 static void inbound(void) {
 181   static int any_recvd;
 182   static time_t nextreann;
 183   static unsigned long npackets, nbytes;
 184
 185   struct sockaddr_in this_saddr;
 186   int r, i, different, this_saddrlen;
 187   const char *emsg;
 188
 189   buf_in.start= buf_in.base+1;
 190   buf_in.size= buffer_size-2;
 191
 192   setnonblock(public_local_fd,1);
 193   this_saddrlen= sizeof(this_saddr);
 194   r= recvfrom(public_local_fd, buf_in.start, buf_in.size, 0,
 195               &this_saddr, &this_saddrlen);
 196   if (!r) { diag("empty ciphertext"); return; }
 197
 198   if (r<0) {
 199     if (errno != EAGAIN && errno != EINTR) { sysdiag("receive"); sleep(1); }
 200     return;
 201   }
 202   if (this_saddr.sin_family != AF_INET) {
 203     fprintf(stderr,"%s: received unknown AF %lu\n",
 204             programid, (unsigned long)this_saddr.sin_family);
 205     return;
 206   }
 207   assert(this_saddrlen == sizeof(this_saddr));
 208
 209   assert(r <= buf_in.size);
 210   buf_in.size= r;
 211   cdebugbuf(-1, "decode", &buf_in, 3,0);
 212   for (i=n_mechs-1; i>=0; i--) {
 213     emsg= mechs[i]->decode(md_in[i],&buf_in);
 214     if (emsg) {
 215       if (*emsg)
 216         fprintf(stderr, "%s: bad packet: %s: %s\n",
 217                 programid, mechs[i]->name, emsg);
 218       else
 219         cdebug(i,"silently discarded");
 220       return;
 221     }
 222     cdebugbuf(i, "decode", &buf_in, 3,0);
 223   }
 224
 225   npackets++;
 226   nbytes += buf_in.size;
 227   alarm(timeout);
 228
 229   different= (!public_remote_specd ||
 230               public_remote.sin_addr.s_addr != this_saddr.sin_addr.s_addr ||
 231               public_remote.sin_port != this_saddr.sin_port);
 232
 233   if (different) {
 234
 235     if (public_remote_specd==2) {
 236       fprintf(stderr, "%s: packet from unexpected sender %s:%lu\n",
 237               programid, inet_ntoa(this_saddr.sin_addr),
 238               (unsigned long)ntohs(this_saddr.sin_port));
 239       return;
 240     }
 241
 242     fprintf(stderr, "%s: tunnel open with peer %s:%lu\n",
 243             programid, inet_ntoa(this_saddr.sin_addr),
 244             (unsigned long)ntohs(this_saddr.sin_port));
 245     nextsendka= now();
 246     public_remote_specd= 1;
 247     memcpy(&public_remote,&this_saddr,sizeof(public_remote));
 248
 249   } else if (!any_recvd) {
 250
 251     diag("tunnel open");
 252
 253   } else if (reannounce && now() >= nextreann) {
 254
 255     fprintf(stderr, "%s: tunnel still open: received %lu packets, %lu bytes\n",
 256             programid, npackets, nbytes);
 257
 258   } else {
 259
 260     goto no_set_reann; /* only reset this if we don't print a message. */
 261
 262   }
 263
 264   if (reannounce)
 265     nextreann= now() + reannounce;
 266
 267 no_set_reann:
 268
 269   any_recvd= 1;
 270
 271   if (!buf_in.size || *buf_in.start != 0300) {
 272     *--buf_in.start= 0300;
 273     buf_in.size++;
 274   }
 275   if (buf_in.start[buf_in.size-1] != 0300) {
 276     buf_in.start[buf_in.size++]= 0300;
 277   }
 278
 279   setnonblock(private_in_fd,0);
 280   write_must(private_in_fd, buf_in.start, buf_in.size, "write down");
 281 }
 282
 283 static void sendpacket(const unsigned char *message, size_t size) {
 284   int i, r;
 285
 286   buf_out.start= buf_out.base+maxprefix;
 287   buf_out.size= size;
 288   memcpy(buf_out.start, message, size);
 289
 290   nextsendka= now() + keepalive;
 291
 292   cdebugbuf(-1, "encode", &buf_out, 4,0);
 293   for (i=0; i<n_mechs; i++) {
 294     mechs[i]->encode(md_out[i],&buf_out);
 295     cdebugbuf(i, "encode", &buf_out, 4,0);
 296   }
 297   assert(public_remote_specd);
 298
 299   setnonblock(public_local_fd,1);
 300   for (;;) {
 301     r= sendto(public_local_fd, buf_out.start, buf_out.size, 0,
 302               &public_remote, sizeof(public_remote));
 303     if (r == buf_out.size) break;
 304     if (r >= 0) { diag("unexpected short send"); return; }
 305     if (errno != EINTR) { sysdiag("send"); return; }
 306   }
 307 }
 308
 309 static void outbound(void) {
 310   int r;
 311   unsigned char *after_eaten, *delim;
 312   size_t this_packet;
 313
 314   setnonblock(private_out_fd,1);
 315
 316   for (;;) {
 317     r= read(private_out_fd, accum_buf + accum_used, accum_avail - accum_used);
 318     if (!r) { diag("outbound datastream closed, quitting"); exit(0); }
 319     if (r<0) {
 320       if (errno == EAGAIN) return;
 321       if (errno == EINTR) continue;
 322     }
 323     accum_used += r;
 324     assert(accum_used<=accum_avail);
 325
 326     after_eaten= accum_buf;
 327     while ((delim= memchr(after_eaten, 0300, accum_used))) {
 328       this_packet= delim - after_eaten;
 329       if (this_packet) sendpacket(after_eaten, this_packet);
 330       accum_used -= this_packet+1;
 331       after_eaten = delim+1;
 332     }
 333     memmove(accum_buf, after_eaten, accum_used);
 334
 335     if (accum_used == accum_avail) {
 336       diag("missing interpacket delimiter in output datastream");
 337       accum_used= 0;
 338     }
 339   }
 340 }
 341
 342 int main(int argc, const char *const *const argv_in) {
 343   const char *arg;
 344   const char *const *argv_save;
 345   const char *const *argv_done;
 346   struct pollfd pollfds[2];
 347   int i, polltimeout, r;
 348   time_t tnow;
 349
 350   argv= argv_in;
 351
 352   if (uname(&uname_result)) { perror(PROGRAM ": uname failed"); exit(16); }
 353   sprintf(programid, PROGRAM ": %.*s", SYS_NMLN, uname_result.nodename);
 354
 355   opt_chars= getarg_string();
 356   encdec_keys_write= !!strchr(opt_chars,'w');
 357   crypto_debug= !!strchr(opt_chars,'K');
 358
 359   public_local_fd= getarg_ulong();
 360   private_in_fd= getarg_ulong();
 361   private_out_fd= getarg_ulong();
 362   encdec_keys_fd= getarg_ulong();
 363
 364   mtu2= getarg_ulong() * 2;
 365   keepalive= getarg_ulong();
 366   timeout= getarg_ulong();
 367   reannounce= getarg_ulong();
 368
 369   arg= getarg_string();
 370   if (*arg) {
 371     public_remote_specd= 1;
 372     public_remote.sin_family= AF_INET;
 373     arg_assert(inet_aton(arg,&public_remote.sin_addr));
 374     public_remote.sin_port= htons(getarg_ulong());
 375   }
 376
 377   if (crypto_debug) {
 378     diag("crypto debugging enabled!");
 379     setvbuf(stdout,0,_IOLBF,0);
 380   }
 381
 382   maxprefix= 0;
 383   i= 0;
 384   while ((arg= *++argv)) {
 385     arg_assert(*arg++ == '|');
 386     arg_assert(i <= MAXMECHS);
 387     mechs[i]= find_mech(arg);
 388
 389     cdebug(i,"writer->reader setup");
 390     argv_save= argv;
 391
 392     if (encdec_keys_write)
 393       mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix);
 394     else
 395       mechs[i]->decsetup(&md_in[i]);
 396
 397     argv_done= argv;
 398     argv= argv_save;
 399     cdebug(i,"reader->writer setup");
 400
 401     if (encdec_keys_write)
 402       mechs[i]->decsetup(&md_in[i]);
 403     else
 404       mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix);
 405
 406     assert(argv == argv_done);
 407
 408     i++;
 409   }
 410   n_mechs= i;
 411
 412   if (maxprefix<1) maxprefix= 1;
 413   if (maxsuffix<1) maxsuffix= 1;
 414   buffer_size= mtu2 + maxprefix + maxsuffix;
 415   buf_in.base= xmalloc(buffer_size);
 416   buf_out.base= xmalloc(buffer_size);
 417   accum_avail= mtu2 + 1;
 418   accum_buf= xmalloc(accum_avail);
 419
 420   alarm(timeout);
 421
 422   pollfds[0].fd= public_local_fd;
 423   pollfds[0].events= POLLIN;
 424   pollfds[1].fd= private_out_fd;
 425   for (;;) {
 426     pollfds[1].events= public_remote_specd ? POLLIN : 0;
 427     pollfds[0].revents= 0;
 428     pollfds[1].revents= 0;
 429
 430     if (keepalive) {
 431       tnow= now();
 432       if (tnow >= nextsendka && public_remote_specd) sendpacket("\300",1);
 433       polltimeout= (nextsendka - tnow)*1000;
 434     } else {
 435       polltimeout= -1;
 436     }
 437
 438     r= poll(pollfds,2,polltimeout);
 439     if (!r) continue;
 440     if (r==-1 && errno==EINTR) continue;
 441     if (r==-1) sysfail("poll");
 442
 443     if (pollfds[0].revents & (POLLIN|POLLERR)) inbound();
 444     if (pollfds[1].revents & (POLLIN|POLLERR)) outbound();
 445   }
 446 }