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

   1 /*
   2  * Encrypting tunnel for userv-ipif tunnels, actual implementation
   3  *
   4  * usage:
   5  *  udptunnel-forwarder <public-local-fd> <private-in-fd> <private-out-fd>
   6  *                      <mtu> <keepalive> <timeout>
   7  *                      <public-remote-addr> [<public-remote-port>]
   8  *                      <encdec-keys-fd> <encdec-keys-write>
   9  *                      <mech1> [<mech1-params> ...]
  10  *                      <mech2> [<mech2-params> ...]
  11  *                      ''
  12  *
  13  * Remote addr may '' to mean wait to receive a packet and reply to
  14  * whereever we get a good packet from first, in which case port
  15  * should not be specified.
  16  *
  17  * <enc-keys-write> is '' to mean read, anything else to mean write.
  18  *
  19  * Every must be numeric.  There is very little argument checking.
  20  *
  21  * Exit status:
  22  *  SIGALARM   timed out
  23  *       0     terminated due to outbound packet stream EOF
  24  *       4     other error
  25  *       8     system problem
  26  *      12     usage error
  27  *      16     bad trouble
  28  */
  29
  30 #include <sys/socket.h>
  31 #include <netinet/in.h>
  32 #include <arpa/inet.h>
  33 #include <sys/utsname.h>
  34 #include <sys/poll.h>
  35
  36 #include <string.h>
  37 #include <errno.h>
  38 #include <assert.h>
  39 #include <stdlib.h>
  40
  41 #include <unistd.h>
  42 #include <fcntl.h>
  43
  44 #include "mech.h"
  45
  46 #define MAXMECHS 10
  47 #define PROGRAM "udptunnel-forwarder"
  48 char programid[SYS_NMLN+sizeof(PROGRAM)+3];
  49
  50 static const char *const *argv;
  51 static size_t buffer_size;
  52
  53 static int public_local_fd, private_in_fd, private_out_fd;
  54 static int mtu2, keepalive, timeout;
  55 static int public_remote_specd;
  56 static struct sockaddr_in public_remote;
  57 static int encdec_keys_fd, encdec_keys_write;
  58 static int n_mechs;
  59 static const struct mechanism *mechs[MAXMECHS];
  60
  61 static struct mechdata *md_in[MAXMECHS], *md_out[MAXMECHS];
  62 static size_t maxprefix, maxsuffix;
  63
  64 static struct buffer buf_in, buf_out;
  65 static unsigned char *accum_buf;
  66 static size_t accum_used, accum_avail;
  67
  68 static time_t nextsendka;
  69
  70
  71 void arg_assert_fail(const char *msg) {
  72   fprintf(stderr, PROGRAM ": argument error: %s\n",msg);
  73   exit(12);
  74 }
  75
  76 void sysfail(const char *msg) {
  77   fprintf(stderr, "%s: fatal system error: %s: %s\n", programid, msg, strerror(errno));
  78   exit(8);
  79 }
  80
  81 void fail(const char *msg) {
  82   fprintf(stderr, "%s: fatal error: %s\n", programid, msg);
  83   exit(4);
  84 }
  85
  86 void sysdiag(const char *msg) {
  87   fprintf(stderr, "%s: system/network error: %s: %s\n", programid, msg, strerror(errno));
  88 }
  89
  90 void diag(const char *msg) {
  91   fprintf(stderr, "%s: %s\n", programid, msg);
  92 }
  93
  94 time_t now(void) {
  95   time_t r;
  96   if (time(&r) == (time_t)-1) sysfail("get time of day");
  97   return r;
  98 }
  99
 100 void *xmalloc(size_t sz) {
 101   void *r;
 102   r= malloc(sz);
 103   if (!r) sysfail("allocate memory");
 104   return r;
 105 }
 106
 107 void get_random(void *ptr, size_t sz) {
 108   static FILE *randfile;
 109
 110   size_t r;
 111
 112   if (!randfile) {
 113     randfile= fopen("/dev/urandom","rb");
 114     if (!randfile && errno==ENOENT) randfile= fopen("/dev/random","rb");
 115     if (!randfile) sysfail("open random number generator");
 116   }
 117
 118   r= fread(ptr,1,sz,randfile);
 119   if (r == sz) return;
 120   (ferror(randfile) ? sysfail : fail)("cannot read random number generator");
 121 }
 122
 123 const char *getarg_string(void) {
 124   const char *arg;
 125
 126   arg= *++argv;
 127   arg_assert(arg);
 128   return arg;
 129 }
 130
 131 unsigned long getarg_ulong(void) {
 132   char *ep;
 133   unsigned long ul;
 134
 135   ul= strtoul(getarg_string(),&ep,0);
 136   arg_assert(!*ep);
 137   return ul;
 138 }
 139
 140 static void setnonblock(int fd, int nonblock) {
 141   int r;
 142
 143   r= fcntl(fd,F_GETFL);
 144   if (r==-1) sysfail("fcntl F_GETFL");
 145   r= fcntl(fd,F_SETFL, nonblock ? r|O_NONBLOCK : r&~O_NONBLOCK);
 146   if (r==-1) sysfail("fcntl F_SETFL");
 147 }
 148
 149 static const struct mechanism *getarg_mech(void) {
 150   const char *name;
 151   const struct mechanism *mech, *const *mechlist;
 152
 153   name= getarg_string();
 154
 155   for (mechlist= mechanismlists;
 156        *mechlist;
 157        mechlist++)
 158     for (mech= *mechlist; mech->name; mech++)
 159       if (!strcmp(mech->name,name)) return mech;
 160
 161   fprintf(stderr,"%s: unknown mechanism: %s\n",programid,name);
 162   exit(4);
 163 }
 164
 165 static void inbound(void) {
 166   static int any_recvd;
 167
 168   struct sockaddr_in this_saddr;
 169   int r, i, different, this_saddrlen;
 170   const char *emsg;
 171
 172   alarm(timeout);
 173
 174   setnonblock(public_local_fd,1);
 175   this_saddrlen= sizeof(this_saddr);
 176   r= recvfrom(public_local_fd, buf_in.base, buffer_size-1, 0,
 177               &this_saddr, &this_saddrlen);
 178   if (!r) { diag("empty ciphertext"); return; }
 179
 180   if (r<0) {
 181     if (errno != EAGAIN && errno != EINTR) sysdiag("receive");
 182     return;
 183   }
 184   if (this_saddr.sin_family != AF_INET) {
 185     fprintf(stderr,"%s: received unknown AF %lu",
 186             programid, (unsigned long)this_saddr.sin_family);
 187     return;
 188   }
 189   assert(this_saddrlen == sizeof(this_saddr));
 190
 191   buf_in.size= buffer_size;
 192   buf_in.start= buf_in.base;
 193   for (i=n_mechs-1; i>=0; i--) {
 194     emsg= mechs[i]->decode(md_in[i],&buf_in);
 195     if (emsg) {
 196       fprintf(stderr, "%s: bad packet: %s: %s\n", programid, mechs[i]->name, emsg);
 197       return;
 198     }
 199   }
 200
 201   different= !public_remote_specd ||
 202     memcmp(&this_saddr,&public_remote,sizeof(this_saddr));
 203
 204   if (different) {
 205
 206     if (public_remote_specd==2) {
 207       fprintf(stderr, "%s: packet from unexpected sender %s:%lu",
 208               programid, inet_ntoa(this_saddr.sin_addr),
 209               (unsigned long)this_saddr.sin_port);
 210       return;
 211     }
 212
 213     fprintf(stderr, "%s: tunnel open with peer %s:%lu",
 214             programid, inet_ntoa(this_saddr.sin_addr),
 215             (unsigned long)this_saddr.sin_port);
 216     nextsendka= now();
 217     public_remote_specd= 1;
 218     memcpy(&public_remote,&this_saddr,sizeof(public_remote));
 219
 220   } else if (!any_recvd) {
 221
 222     diag("tunnel open");
 223
 224   }
 225
 226   any_recvd= 1;
 227
 228   buf_in.start[buf_in.size]= 0300;
 229   *--buf_in.start= 0300;
 230   buf_in.size+= 2;
 231
 232   setnonblock(private_in_fd,0);
 233   while (buf_in.size) {
 234     r= write(private_in_fd, buf_in.start, buf_in.size);
 235     assert(r && r <= buf_in.size);
 236     if (r<0) {
 237       if (errno == EINTR) continue;
 238       sysfail("write down");
 239     }
 240     buf_in.start += r;
 241     buf_in.size -= r;
 242   }
 243 }
 244
 245 static void sendpacket(const unsigned char *message, size_t size) {
 246   int i, r;
 247
 248   buf_out.start= buf_out.base+maxprefix;
 249   buf_out.size= size;
 250   memcpy(buf_out.start, message, size);
 251
 252   nextsendka= now() + keepalive;
 253
 254   for (i=0; i<n_mechs; i++) mechs[i]->encode(md_out[i],&buf_out);
 255   assert(public_remote_specd);
 256
 257   setnonblock(public_local_fd,1);
 258   for (;;) {
 259     r= sendto(public_local_fd, buf_out.start, buf_out.size, 0,
 260               &public_remote, sizeof(public_remote));
 261     if (r == buf_out.size) break;
 262     if (r >= 0) { diag("unexpected short send"); return; }
 263     if (errno != EINTR) { sysdiag("send"); return; }
 264   }
 265 }
 266
 267 static void outbound(void) {
 268   int r;
 269   unsigned char *after_eaten, *delim;
 270   size_t this_packet;
 271
 272   setnonblock(private_out_fd,1);
 273
 274   for (;;) {
 275     r= read(private_out_fd, accum_buf + accum_used, accum_avail - accum_used);
 276     if (!r) { diag("outbound datastream closed, quitting"); exit(0); }
 277     if (r<0) {
 278       if (errno == EAGAIN) return;
 279       if (errno == EINTR) continue;
 280     }
 281     accum_used += r;
 282     assert(accum_used<=accum_avail);
 283
 284     after_eaten= accum_buf;
 285     while ((delim= memchr(after_eaten, 0300, accum_used))) {
 286       this_packet= delim - after_eaten;
 287       sendpacket(after_eaten, this_packet);
 288       accum_used -= this_packet+1;
 289       after_eaten = delim+1;
 290     }
 291     memmove(accum_buf, after_eaten, accum_used);
 292
 293     if (accum_used == accum_avail) {
 294       diag("missing interpacket delimiter in output datastream");
 295       accum_used= 0;
 296     }
 297   }
 298 }
 299
 300 int main(int argc, const char *const *const argv_in) {
 301   const char *arg;
 302   struct pollfd pollfds[2];
 303   struct utsname uname_result;
 304   int i, polltimeout, r;
 305   time_t tnow;
 306
 307   argv= argv_in;
 308
 309   if (uname(&uname_result)) { perror(PROGRAM ": uname failed"); exit(16); }
 310   sprintf(programid, PROGRAM ": %.*s", SYS_NMLN, uname_result.nodename);
 311
 312   public_local_fd= getarg_ulong();
 313   mtu2= getarg_ulong() * 2;
 314   keepalive= getarg_ulong();
 315   timeout= getarg_ulong();
 316   private_in_fd= getarg_ulong();
 317   private_out_fd= getarg_ulong();
 318
 319   arg= getarg_string();
 320   if (*arg) {
 321     public_remote_specd= 1;
 322     arg_assert(inet_aton(arg,&public_remote.sin_addr));
 323     public_remote.sin_port= getarg_ulong();
 324   }
 325
 326   encdec_keys_fd= getarg_ulong();
 327   encdec_keys_write= !!*getarg_string();
 328
 329   maxprefix= 0;
 330   for (i=0; i<n_mechs; i++) mechs[i]= getarg_mech();
 331   for (i=0; i<n_mechs; i++) mechs[i]->encsetup(&md_in[i], &maxprefix, &maxsuffix);
 332   for (i=0; i<n_mechs; i++) mechs[i]->decsetup(&md_out[i]);
 333
 334   if (maxprefix<1) maxprefix= 1;
 335   if (maxsuffix<1) maxsuffix= 1;
 336   buffer_size= mtu2 + maxprefix + maxsuffix;
 337   buf_in.base= xmalloc(buffer_size);
 338   buf_out.base= xmalloc(buffer_size);
 339   accum_avail= mtu2 + 1;
 340   accum_buf= xmalloc(accum_avail);
 341
 342   alarm(timeout);
 343
 344   pollfds[0].fd= public_local_fd;
 345   pollfds[0].events= POLLIN;
 346   pollfds[1].fd= private_out_fd;
 347   for (;;) {
 348     pollfds[1].events= public_remote_specd ? POLLIN : 0;
 349     pollfds[0].revents= 0;
 350     pollfds[1].revents= 0;
 351
 352     if (keepalive) {
 353       tnow= now();
 354       if (tnow >= nextsendka) sendpacket("\300",1);
 355       polltimeout= (nextsendka - tnow)*1000;
 356     } else {
 357       polltimeout= -1;
 358     }
 359
 360     r= poll(pollfds,2,polltimeout);
 361     if (!r) continue;
 362     if (r==-1 && errno==EINTR) continue;
 363     if (r==-1) sysfail("poll");
 364
 365     if (pollfds[0].revents & POLLIN) inbound();
 366     if (pollfds[1].revents & POLLOUT) outbound();
 367   }
 368 }