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

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