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 int 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   size_t this_saddrlen;
 187   int r, i, different;
 188   const char *emsg;
 189
 190   buf_in.start= buf_in.base+1;
 191   buf_in.size= buffer_size-2;
 192
 193   setnonblock(public_local_fd,1);
 194   this_saddrlen= sizeof(this_saddr);
 195   r= recvfrom(public_local_fd, buf_in.start, buf_in.size, 0,
 196               &this_saddr, &this_saddrlen);
 197   if (!r) { diag("empty ciphertext"); return; }
 198
 199   if (r<0) {
 200     if (errno != EAGAIN && errno != EINTR) { sysdiag("receive"); sleep(1); }
 201     return;
 202   }
 203   if (this_saddr.sin_family != AF_INET) {
 204     fprintf(stderr,"%s: received unknown AF %lu\n",
 205             programid, (unsigned long)this_saddr.sin_family);
 206     return;
 207   }
 208   assert(this_saddrlen == sizeof(this_saddr));
 209
 210   assert(r <= buf_in.size);
 211   buf_in.size= r;
 212   cdebugbuf(-1, "decode", &buf_in, 3,0);
 213   for (i=n_mechs-1; i>=0; i--) {
 214     emsg= mechs[i]->decode(md_in[i],&buf_in);
 215     if (emsg) {
 216       if (*emsg)
 217         fprintf(stderr, "%s: bad packet: %s: %s\n",
 218                 programid, mechs[i]->name, emsg);
 219       else
 220         cdebug(i,"silently discarded");
 221       return;
 222     }
 223     cdebugbuf(i, "decode", &buf_in, 3,0);
 224   }
 225
 226   npackets++;
 227   nbytes += buf_in.size;
 228   alarm(timeout);
 229
 230   different= (!public_remote_specd ||
 231               public_remote.sin_addr.s_addr != this_saddr.sin_addr.s_addr ||
 232               public_remote.sin_port != this_saddr.sin_port);
 233
 234   if (different) {
 235
 236     if (public_remote_specd==2) {
 237       fprintf(stderr, "%s: packet from unexpected sender %s:%lu\n",
 238               programid, inet_ntoa(this_saddr.sin_addr),
 239               (unsigned long)ntohs(this_saddr.sin_port));
 240       return;
 241     }
 242
 243     fprintf(stderr, "%s: tunnel open with peer %s:%lu\n",
 244             programid, inet_ntoa(this_saddr.sin_addr),
 245             (unsigned long)ntohs(this_saddr.sin_port));
 246     nextsendka= now();
 247     public_remote_specd= 1;
 248     memcpy(&public_remote,&this_saddr,sizeof(public_remote));
 249
 250   } else if (!any_recvd) {
 251
 252     diag("tunnel open");
 253
 254   } else if (reannounce && now() >= nextreann) {
 255
 256     fprintf(stderr, "%s: tunnel still open: received %lu packets, %lu bytes\n",
 257             programid, npackets, nbytes);
 258
 259   } else {
 260
 261     goto no_set_reann; /* only reset this if we don't print a message. */
 262
 263   }
 264
 265   if (reannounce)
 266     nextreann= now() + reannounce;
 267
 268 no_set_reann:
 269
 270   any_recvd= 1;
 271
 272   if (!buf_in.size || *buf_in.start != 0300) {
 273     *--buf_in.start= 0300;
 274     buf_in.size++;
 275   }
 276   if (buf_in.start[buf_in.size-1] != 0300) {
 277     buf_in.start[buf_in.size++]= 0300;
 278   }
 279
 280   setnonblock(private_in_fd,0);
 281   write_must(private_in_fd, buf_in.start, buf_in.size, "write down");
 282 }
 283
 284 static void sendpacket(const unsigned char *message, size_t size) {
 285   int i, r;
 286
 287   buf_out.start= buf_out.base+maxprefix;
 288   buf_out.size= size;
 289   memcpy(buf_out.start, message, size);
 290
 291   nextsendka= now() + keepalive;
 292
 293   cdebugbuf(-1, "encode", &buf_out, 4,0);
 294   for (i=0; i<n_mechs; i++) {
 295     mechs[i]->encode(md_out[i],&buf_out);
 296     cdebugbuf(i, "encode", &buf_out, 4,0);
 297   }
 298   assert(public_remote_specd);
 299
 300   setnonblock(public_local_fd,1);
 301   for (;;) {
 302     r= sendto(public_local_fd, buf_out.start, buf_out.size, 0,
 303               &public_remote, sizeof(public_remote));
 304     if (r == buf_out.size) break;
 305     if (r >= 0) { diag("unexpected short send"); return; }
 306     if (errno != EINTR) { sysdiag("send"); return; }
 307   }
 308 }
 309
 310 static void outbound(void) {
 311   int r;
 312   unsigned char *after_eaten, *delim;
 313   size_t this_packet;
 314
 315   setnonblock(private_out_fd,1);
 316
 317   for (;;) {
 318     r= read(private_out_fd, accum_buf + accum_used, accum_avail - accum_used);
 319     if (!r) { diag("outbound datastream closed, quitting"); exit(0); }
 320     if (r<0) {
 321       if (errno == EAGAIN) return;
 322       if (errno == EINTR) continue;
 323     }
 324     accum_used += r;
 325     assert(accum_used<=accum_avail);
 326
 327     after_eaten= accum_buf;
 328     while ((delim= memchr(after_eaten, 0300, accum_used))) {
 329       this_packet= delim - after_eaten;
 330       if (this_packet) sendpacket(after_eaten, this_packet);
 331       accum_used -= this_packet+1;
 332       after_eaten = delim+1;
 333     }
 334     memmove(accum_buf, after_eaten, accum_used);
 335
 336     if (accum_used == accum_avail) {
 337       diag("missing interpacket delimiter in output datastream");
 338       accum_used= 0;
 339     }
 340   }
 341 }
 342
 343 int main(int argc, const char *const *const argv_in) {
 344   const char *arg;
 345   const char *const *argv_save;
 346   const char *const *argv_done;
 347   struct pollfd pollfds[2];
 348   int i, polltimeout, r;
 349   time_t tnow;
 350
 351   argv= argv_in;
 352
 353   if (uname(&uname_result)) { perror(PROGRAM ": uname failed"); exit(16); }
 354   sprintf(programid, PROGRAM ": %.*s", SYS_NMLN, uname_result.nodename);
 355
 356   opt_chars= getarg_string();
 357   encdec_keys_write= !!strchr(opt_chars,'w');
 358   crypto_debug= !!strchr(opt_chars,'K');
 359
 360   public_local_fd= getarg_ulong();
 361   private_in_fd= getarg_ulong();
 362   private_out_fd= getarg_ulong();
 363   encdec_keys_fd= getarg_ulong();
 364
 365   mtu2= getarg_ulong() * 2;
 366   keepalive= getarg_ulong();
 367   timeout= getarg_ulong();
 368   reannounce= getarg_ulong();
 369
 370   arg= getarg_string();
 371   if (*arg) {
 372     public_remote_specd= 1;
 373     public_remote.sin_family= AF_INET;
 374     arg_assert(inet_aton(arg,&public_remote.sin_addr));
 375     public_remote.sin_port= htons(getarg_ulong());
 376   }
 377
 378   if (crypto_debug) {
 379     diag("crypto debugging enabled!");
 380     setvbuf(stdout,0,_IOLBF,0);
 381   }
 382
 383   maxprefix= 0;
 384   i= 0;
 385   while ((arg= *++argv)) {
 386     arg_assert(*arg++ == '|');
 387     arg_assert(i <= MAXMECHS);
 388     mechs[i]= find_mech(arg);
 389
 390     cdebug(i,"writer->reader setup");
 391     argv_save= argv;
 392
 393     if (encdec_keys_write)
 394       mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix);
 395     else
 396       mechs[i]->decsetup(&md_in[i]);
 397
 398     argv_done= argv;
 399     argv= argv_save;
 400     cdebug(i,"reader->writer setup");
 401
 402     if (encdec_keys_write)
 403       mechs[i]->decsetup(&md_in[i]);
 404     else
 405       mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix);
 406
 407     assert(argv == argv_done);
 408
 409     i++;
 410   }
 411   n_mechs= i;
 412
 413   if (maxprefix<1) maxprefix= 1;
 414   if (maxsuffix<1) maxsuffix= 1;
 415   buffer_size= mtu2 + maxprefix + maxsuffix;
 416   buf_in.base= xmalloc(buffer_size);
 417   buf_out.base= xmalloc(buffer_size);
 418   accum_avail= mtu2 + 1;
 419   accum_buf= xmalloc(accum_avail);
 420
 421   alarm(timeout);
 422
 423   pollfds[0].fd= public_local_fd;
 424   pollfds[0].events= POLLIN;
 425   pollfds[1].fd= private_out_fd;
 426   for (;;) {
 427     pollfds[1].events= public_remote_specd ? POLLIN : 0;
 428     pollfds[0].revents= 0;
 429     pollfds[1].revents= 0;
 430
 431     if (keepalive) {
 432       tnow= now();
 433       if (tnow >= nextsendka && public_remote_specd)
 434         sendpacket((unsigned char*)"\300",1);
 435       polltimeout= (nextsendka - tnow)*1000;
 436     } else {
 437       polltimeout= -1;
 438     }
 439
 440     r= poll(pollfds,2,polltimeout);
 441     if (!r) continue;
 442     if (r==-1 && errno==EINTR) continue;
 443     if (r==-1) sysfail("poll");
 444
 445     if (pollfds[0].revents & (POLLIN|POLLERR)) inbound();
 446     if (pollfds[1].revents & (POLLIN|POLLERR)) outbound();
 447   }
 448 }