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 <optchars>
   6  *                      <public-local-fd> <private-in-fd> <private-out-fd>
   7  *                      <encdec-keys-fd>
   8  *                      <mtu> <keepalive> <timeout>
   9  *                      <public-remote-addr> [<public-remote-port>]
  10  *                      !<mech1> [<mech1-params> ...]
  11  *                      !<mech2> [<mech2-params> ...]
  12  *                      ''
  13  *
  14  * Remote addr may '' to mean wait to receive a packet and reply to
  15  * whereever we get a good packet from first, in which case port
  16  * should not be specified.
  17  *
  18  * <optchars> is zero or more of
  19  *    w   means generate and write encdec keys, rather than reading them
  20  *    K   means do crypto debug (use with care!)
  21  *
  22  * Every must be numeric.  There is very little argument checking.
  23  *
  24  * Exit status:
  25  *  SIGALARM   timed out
  26  *       0     terminated due to outbound packet stream EOF
  27  *       4     other error
  28  *       8     system problem
  29  *      12     usage error
  30  *      16     bad trouble
  31  */
  32
  33 #include <sys/socket.h>
  34 #include <netinet/in.h>
  35 #include <arpa/inet.h>
  36 #include <sys/utsname.h>
  37 #include <sys/poll.h>
  38
  39 #include <string.h>
  40 #include <errno.h>
  41 #include <assert.h>
  42 #include <stdlib.h>
  43
  44 #include <unistd.h>
  45 #include <fcntl.h>
  46
  47 #include "forwarder.h"
  48
  49 #define MAXMECHS 10
  50
  51 static size_t buffer_size;
  52 static struct utsname uname_result;
  53
  54 static const char *opt_chars;
  55 static int public_local_fd, private_in_fd, private_out_fd;
  56 static int mtu2, keepalive, timeout;
  57 static int public_remote_specd;
  58 static struct sockaddr_in public_remote;
  59 static int encdec_keys_fd, encdec_keys_write, crypto_debug;
  60 static int n_mechs;
  61 static const struct mechanism *mechs[MAXMECHS];
  62
  63 static struct mechdata *md_in[MAXMECHS], *md_out[MAXMECHS];
  64 static size_t maxprefix, maxsuffix;
  65
  66 static struct buffer buf_in, buf_out;
  67 static unsigned char *accum_buf;
  68 static size_t accum_used, accum_avail;
  69
  70 static time_t nextsendka;
  71
  72 static void cdebug(int mechno /*or -1*/, const char *msg) {
  73   if (!crypto_debug) return;
  74   printf("%s: CRYPTO: %-20s %s\n",
  75          programid,
  76          mechno >= 0 ? mechs[mechno]->name : "",
  77          msg);
  78 }
  79
  80 static void cdebughex(int mechno /*or -1*/, const char *msg, const void *ptr,
  81                       size_t sz, size_t skipbefore,
  82                       int spc_offset, int dot_offset) {
  83   const unsigned char *p;
  84   size_t i;
  85   unsigned j= dot_offset;
  86
  87   if (!crypto_debug) return;
  88   printf("%-8.8s: CRYPTO: %-20s %-10s",
  89          uname_result.nodename,
  90          mechno >= 0 ? mechs[mechno]->name : "",
  91          msg);
  92
  93   for (i=0; i<spc_offset; i++, j++) fputs(j&3 ? "  " : "   ",stdout);
  94   for (i=0; i<skipbefore; i++, j++) fputs(j&3 ? ".." : " ..",stdout);
  95   for (i=0, p=ptr; i<sz; i++, j++, p++) printf(j&3 ? "%02x" : " %02x",*p);
  96
  97   fputc('\n',stdout);
  98 }
  99
 100 static void cdebugbuf(int mechno /*or -1*/, const char *msg,
 101                       const struct buffer *buf, int spc_offset, int dot_offset) {
 102   cdebughex(mechno, msg, buf->start, buf->size, buf->start - buf->base,
 103             spc_offset, dot_offset);
 104 }
 105
 106 void get_random(void *ptr, size_t sz) {
 107   static FILE *randfile;
 108
 109   size_t r;
 110
 111   if (!randfile) {
 112     randfile= fopen("/dev/urandom","rb");
 113     if (!randfile && errno==ENOENT) randfile= fopen("/dev/random","rb");
 114     if (!randfile) sysfail("open random number generator");
 115   }
 116
 117   r= fread(ptr,1,sz,randfile);
 118   if (r != sz)
 119     (ferror(randfile) ? sysfail : fail)("cannot read random number generator");
 120
 121   cdebughex(-1, "get_random", ptr, sz, 0,0,0);
 122 }
 123
 124 void random_key(void *ptr, size_t sz) {
 125   if (encdec_keys_write) {
 126     get_random(ptr,sz);
 127     write_must(encdec_keys_fd,ptr,sz,"write keys datastream");
 128   } else {
 129     read_must(encdec_keys_fd,ptr,sz,"read keys datastream");
 130   }
 131 }
 132
 133
 134 static void setnonblock(int fd, int nonblock) {
 135   int r;
 136
 137   r= fcntl(fd,F_GETFL);
 138   if (r==-1) sysfail("fcntl F_GETFL");
 139   r= fcntl(fd,F_SETFL, nonblock ? r|O_NONBLOCK : r&~O_NONBLOCK);
 140   if (r==-1) sysfail("fcntl F_SETFL");
 141 }
 142
 143 static const struct mechanism *find_mech(const char *name) {
 144   const struct mechanism *mech, *const *mechlist;
 145
 146   for (mechlist= mechanismlists;
 147        *mechlist;
 148        mechlist++)
 149     for (mech= *mechlist; mech->name; mech++)
 150       if (!strcmp(mech->name,name)) return mech;
 151
 152   fprintf(stderr,"%s: unknown mechanism: %s\n",programid,name);
 153   exit(4);
 154 }
 155
 156 static void inbound(void) {
 157   static int any_recvd;
 158
 159   struct sockaddr_in this_saddr;
 160   int r, i, different, this_saddrlen;
 161   const char *emsg;
 162
 163   buf_in.start= buf_in.base+1;
 164   buf_in.size= buffer_size-2;
 165
 166   setnonblock(public_local_fd,1);
 167   this_saddrlen= sizeof(this_saddr);
 168   r= recvfrom(public_local_fd, buf_in.start, buf_in.size, 0,
 169               &this_saddr, &this_saddrlen);
 170   if (!r) { diag("empty ciphertext"); return; }
 171
 172   if (r<0) {
 173     if (errno != EAGAIN && errno != EINTR) { sysdiag("receive"); sleep(1); }
 174     return;
 175   }
 176   if (this_saddr.sin_family != AF_INET) {
 177     fprintf(stderr,"%s: received unknown AF %lu\n",
 178             programid, (unsigned long)this_saddr.sin_family);
 179     return;
 180   }
 181   assert(this_saddrlen == sizeof(this_saddr));
 182
 183   assert(r <= buf_in.size);
 184   buf_in.size= r;
 185   cdebugbuf(-1, "decode", &buf_in, 3,0);
 186   for (i=n_mechs-1; i>=0; i--) {
 187     emsg= mechs[i]->decode(md_in[i],&buf_in);
 188     if (emsg) {
 189       fprintf(stderr, "%s: bad packet: %s: %s\n", programid, mechs[i]->name, emsg);
 190       return;
 191     }
 192     cdebugbuf(i, "decode", &buf_in, 3,0);
 193   }
 194
 195   alarm(timeout);
 196
 197   different= (!public_remote_specd ||
 198               public_remote.sin_addr.s_addr != this_saddr.sin_addr.s_addr ||
 199               public_remote.sin_port != this_saddr.sin_port);
 200
 201   if (different) {
 202
 203     if (public_remote_specd==2) {
 204       fprintf(stderr, "%s: packet from unexpected sender %s:%lu\n",
 205               programid, inet_ntoa(this_saddr.sin_addr),
 206               (unsigned long)ntohs(this_saddr.sin_port));
 207       return;
 208     }
 209
 210     fprintf(stderr, "%s: tunnel open with peer %s:%lu\n",
 211             programid, inet_ntoa(this_saddr.sin_addr),
 212             (unsigned long)ntohs(this_saddr.sin_port));
 213     nextsendka= now();
 214     public_remote_specd= 1;
 215     memcpy(&public_remote,&this_saddr,sizeof(public_remote));
 216
 217   } else if (!any_recvd) {
 218
 219     diag("tunnel open");
 220
 221   }
 222
 223   any_recvd= 1;
 224
 225   if (!buf_in.size || *buf_in.start != 0300) {
 226     *--buf_in.start= 0300;
 227     buf_in.size++;
 228   }
 229   if (buf_in.start[buf_in.size-1] != 0300) {
 230     buf_in.start[buf_in.size++]= 0300;
 231   }
 232
 233   setnonblock(private_in_fd,0);
 234   write_must(private_in_fd, buf_in.start, buf_in.size, "write down");
 235 }
 236
 237 static void sendpacket(const unsigned char *message, size_t size) {
 238   int i, r;
 239
 240   buf_out.start= buf_out.base+maxprefix;
 241   buf_out.size= size;
 242   memcpy(buf_out.start, message, size);
 243
 244   nextsendka= now() + keepalive;
 245
 246   cdebugbuf(-1, "encode", &buf_out, 4,0);
 247   for (i=0; i<n_mechs; i++) {
 248     mechs[i]->encode(md_out[i],&buf_out);
 249     cdebugbuf(i, "encode", &buf_out, 4,0);
 250   }
 251   assert(public_remote_specd);
 252
 253   setnonblock(public_local_fd,1);
 254   for (;;) {
 255     r= sendto(public_local_fd, buf_out.start, buf_out.size, 0,
 256               &public_remote, sizeof(public_remote));
 257     if (r == buf_out.size) break;
 258     if (r >= 0) { diag("unexpected short send"); return; }
 259     if (errno != EINTR) { sysdiag("send"); return; }
 260   }
 261 }
 262
 263 static void outbound(void) {
 264   int r;
 265   unsigned char *after_eaten, *delim;
 266   size_t this_packet;
 267
 268   setnonblock(private_out_fd,1);
 269
 270   for (;;) {
 271     r= read(private_out_fd, accum_buf + accum_used, accum_avail - accum_used);
 272     if (!r) { diag("outbound datastream closed, quitting"); exit(0); }
 273     if (r<0) {
 274       if (errno == EAGAIN) return;
 275       if (errno == EINTR) continue;
 276     }
 277     accum_used += r;
 278     assert(accum_used<=accum_avail);
 279
 280     after_eaten= accum_buf;
 281     while ((delim= memchr(after_eaten, 0300, accum_used))) {
 282       this_packet= delim - after_eaten;
 283       if (this_packet) sendpacket(after_eaten, this_packet);
 284       accum_used -= this_packet+1;
 285       after_eaten = delim+1;
 286     }
 287     memmove(accum_buf, after_eaten, accum_used);
 288
 289     if (accum_used == accum_avail) {
 290       diag("missing interpacket delimiter in output datastream");
 291       accum_used= 0;
 292     }
 293   }
 294 }
 295
 296 int main(int argc, const char *const *const argv_in) {
 297   const char *arg;
 298   const char *const *argv_save;
 299   const char *const *argv_done;
 300   struct pollfd pollfds[2];
 301   int i, polltimeout, r;
 302   time_t tnow;
 303
 304   argv= argv_in;
 305
 306   if (uname(&uname_result)) { perror(PROGRAM ": uname failed"); exit(16); }
 307   sprintf(programid, PROGRAM ": %.*s", SYS_NMLN, uname_result.nodename);
 308
 309   opt_chars= getarg_string();
 310   encdec_keys_write= !!strchr(opt_chars,'w');
 311   crypto_debug= !!strchr(opt_chars,'K');
 312
 313   public_local_fd= getarg_ulong();
 314   private_in_fd= getarg_ulong();
 315   private_out_fd= getarg_ulong();
 316   encdec_keys_fd= getarg_ulong();
 317
 318   mtu2= getarg_ulong() * 2;
 319   keepalive= getarg_ulong();
 320   timeout= getarg_ulong();
 321
 322   arg= getarg_string();
 323   if (*arg) {
 324     public_remote_specd= 1;
 325     public_remote.sin_family= AF_INET;
 326     arg_assert(inet_aton(arg,&public_remote.sin_addr));
 327     public_remote.sin_port= htons(getarg_ulong());
 328   }
 329
 330   if (crypto_debug) {
 331     diag("crypto debugging enabled!");
 332     setvbuf(stdout,0,_IOLBF,0);
 333   }
 334
 335   maxprefix= 0;
 336   i= 0;
 337   while ((arg= *++argv)) {
 338     arg_assert(*arg++ == '!');
 339     arg_assert(i <= MAXMECHS);
 340     mechs[i]= find_mech(arg);
 341     cdebug(i,"encsetup");
 342
 343     argv_save= argv;
 344     mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix);
 345
 346     argv_done= argv;
 347     argv= argv_save;
 348     cdebug(i,"decsetup");
 349     mechs[i]->decsetup(&md_in[i]);
 350
 351     assert(argv == argv_done);
 352
 353     i++;
 354   }
 355   n_mechs= i;
 356
 357   if (maxprefix<1) maxprefix= 1;
 358   if (maxsuffix<1) maxsuffix= 1;
 359   buffer_size= mtu2 + maxprefix + maxsuffix;
 360   buf_in.base= xmalloc(buffer_size);
 361   buf_out.base= xmalloc(buffer_size);
 362   accum_avail= mtu2 + 1;
 363   accum_buf= xmalloc(accum_avail);
 364
 365   alarm(timeout);
 366
 367   pollfds[0].fd= public_local_fd;
 368   pollfds[0].events= POLLIN;
 369   pollfds[1].fd= private_out_fd;
 370   for (;;) {
 371     pollfds[1].events= public_remote_specd ? POLLIN : 0;
 372     pollfds[0].revents= 0;
 373     pollfds[1].revents= 0;
 374
 375     if (keepalive) {
 376       tnow= now();
 377       if (tnow >= nextsendka && public_remote_specd) sendpacket("\300",1);
 378       polltimeout= (nextsendka - tnow)*1000;
 379     } else {
 380       polltimeout= -1;
 381     }
 382
 383     r= poll(pollfds,2,polltimeout);
 384     if (!r) continue;
 385     if (r==-1 && errno==EINTR) continue;
 386     if (r==-1) sysfail("poll");
 387
 388     if (pollfds[0].revents & (POLLIN|POLLERR)) inbound();
 389     if (pollfds[1].revents & (POLLIN|POLLERR)) outbound();
 390   }
 391 }