| 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 | * encdec keys datastream has keys for packets from key datastream |
| 23 | * writer to reader first, then keys for packets from reader to |
| 24 | * writer. |
| 25 | * |
| 26 | * Every must be numeric. There is very little argument checking. |
| 27 | * |
| 28 | * Exit status: |
| 29 | * SIGALARM timed out |
| 30 | * 0 terminated due to outbound packet stream EOF |
| 31 | * 4 other error |
| 32 | * 8 system problem |
| 33 | * 12 usage error |
| 34 | * 16 bad trouble |
| 35 | */ |
| 36 | |
| 37 | #include <sys/socket.h> |
| 38 | #include <netinet/in.h> |
| 39 | #include <arpa/inet.h> |
| 40 | #include <sys/utsname.h> |
| 41 | #include <sys/poll.h> |
| 42 | |
| 43 | #include <string.h> |
| 44 | #include <errno.h> |
| 45 | #include <assert.h> |
| 46 | #include <stdlib.h> |
| 47 | |
| 48 | #include <unistd.h> |
| 49 | #include <fcntl.h> |
| 50 | |
| 51 | #include "forwarder.h" |
| 52 | |
| 53 | #define MAXMECHS 10 |
| 54 | |
| 55 | static size_t buffer_size; |
| 56 | static struct utsname uname_result; |
| 57 | |
| 58 | static const char *opt_chars; |
| 59 | static int public_local_fd, private_in_fd, private_out_fd; |
| 60 | static int mtu2, keepalive, timeout; |
| 61 | static int public_remote_specd; |
| 62 | static struct sockaddr_in public_remote; |
| 63 | static int encdec_keys_fd, encdec_keys_write, crypto_debug; |
| 64 | static int n_mechs; |
| 65 | static const struct mechanism *mechs[MAXMECHS]; |
| 66 | |
| 67 | static struct mechdata *md_in[MAXMECHS], *md_out[MAXMECHS]; |
| 68 | static size_t maxprefix, maxsuffix; |
| 69 | |
| 70 | static struct buffer buf_in, buf_out; |
| 71 | static unsigned char *accum_buf; |
| 72 | static size_t accum_used, accum_avail; |
| 73 | |
| 74 | static time_t nextsendka; |
| 75 | |
| 76 | static void cdebug(int mechno /*or -1*/, const char *msg) { |
| 77 | if (!crypto_debug) return; |
| 78 | printf("%-8.8s: CRYPTO: %-20s %s\n", |
| 79 | uname_result.nodename, |
| 80 | mechno >= 0 ? mechs[mechno]->name : "", |
| 81 | msg); |
| 82 | } |
| 83 | |
| 84 | static void cdebughex(int mechno /*or -1*/, const char *msg, const void *ptr, |
| 85 | size_t sz, size_t skipbefore, |
| 86 | int spc_offset, int dot_offset) { |
| 87 | const unsigned char *p; |
| 88 | size_t i; |
| 89 | unsigned j= dot_offset; |
| 90 | |
| 91 | if (!crypto_debug) return; |
| 92 | printf("%-8.8s: CRYPTO: %-20s %-10s", |
| 93 | uname_result.nodename, |
| 94 | mechno >= 0 ? mechs[mechno]->name : "", |
| 95 | msg); |
| 96 | |
| 97 | for (i=0; i<spc_offset; i++, j++) fputs(j&3 ? " " : " ",stdout); |
| 98 | for (i=0; i<skipbefore; i++, j++) fputs(j&3 ? ".." : " ..",stdout); |
| 99 | for (i=0, p=ptr; i<sz; i++, j++, p++) printf(j&3 ? "%02x" : " %02x",*p); |
| 100 | |
| 101 | fputc('\n',stdout); |
| 102 | } |
| 103 | |
| 104 | static void cdebugbuf(int mechno /*or -1*/, const char *msg, |
| 105 | const struct buffer *buf, int spc_offset, int dot_offset) { |
| 106 | cdebughex(mechno, msg, buf->start, buf->size, buf->start - buf->base, |
| 107 | spc_offset, dot_offset); |
| 108 | } |
| 109 | |
| 110 | void get_random(void *ptr, size_t sz) { |
| 111 | static FILE *randfile; |
| 112 | |
| 113 | size_t r; |
| 114 | |
| 115 | if (!randfile) { |
| 116 | randfile= fopen("/dev/urandom","rb"); |
| 117 | if (!randfile && errno==ENOENT) randfile= fopen("/dev/random","rb"); |
| 118 | if (!randfile) sysfail("open random number generator"); |
| 119 | } |
| 120 | |
| 121 | r= fread(ptr,1,sz,randfile); |
| 122 | if (r != sz) |
| 123 | (ferror(randfile) ? sysfail : fail)("cannot read random number generator"); |
| 124 | |
| 125 | cdebughex(-1, "get_random", ptr, sz, 0,0,0); |
| 126 | } |
| 127 | |
| 128 | void random_key(void *ptr, size_t sz) { |
| 129 | if (encdec_keys_write) { |
| 130 | get_random(ptr,sz); |
| 131 | write_must(encdec_keys_fd,ptr,sz,"write keys datastream"); |
| 132 | } else { |
| 133 | read_must(encdec_keys_fd,ptr,sz,"read keys datastream"); |
| 134 | cdebughex(-1, "random_key", ptr, sz, 0,0,0); |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | |
| 139 | static void setnonblock(int fd, int nonblock) { |
| 140 | int r; |
| 141 | |
| 142 | r= fcntl(fd,F_GETFL); |
| 143 | if (r==-1) sysfail("fcntl F_GETFL"); |
| 144 | r= fcntl(fd,F_SETFL, nonblock ? r|O_NONBLOCK : r&~O_NONBLOCK); |
| 145 | if (r==-1) sysfail("fcntl F_SETFL"); |
| 146 | } |
| 147 | |
| 148 | static const struct mechanism *find_mech(const char *name) { |
| 149 | const struct mechanism *mech, *const *mechlist; |
| 150 | |
| 151 | for (mechlist= mechanismlists; |
| 152 | *mechlist; |
| 153 | mechlist++) |
| 154 | for (mech= *mechlist; mech->name; mech++) |
| 155 | if (!strcmp(mech->name,name)) return mech; |
| 156 | |
| 157 | fprintf(stderr,"%s: unknown mechanism: %s\n",programid,name); |
| 158 | exit(4); |
| 159 | } |
| 160 | |
| 161 | static void inbound(void) { |
| 162 | static int any_recvd; |
| 163 | |
| 164 | struct sockaddr_in this_saddr; |
| 165 | int r, i, different, this_saddrlen; |
| 166 | const char *emsg; |
| 167 | |
| 168 | buf_in.start= buf_in.base+1; |
| 169 | buf_in.size= buffer_size-2; |
| 170 | |
| 171 | setnonblock(public_local_fd,1); |
| 172 | this_saddrlen= sizeof(this_saddr); |
| 173 | r= recvfrom(public_local_fd, buf_in.start, buf_in.size, 0, |
| 174 | &this_saddr, &this_saddrlen); |
| 175 | if (!r) { diag("empty ciphertext"); return; } |
| 176 | |
| 177 | if (r<0) { |
| 178 | if (errno != EAGAIN && errno != EINTR) { sysdiag("receive"); sleep(1); } |
| 179 | return; |
| 180 | } |
| 181 | if (this_saddr.sin_family != AF_INET) { |
| 182 | fprintf(stderr,"%s: received unknown AF %lu\n", |
| 183 | programid, (unsigned long)this_saddr.sin_family); |
| 184 | return; |
| 185 | } |
| 186 | assert(this_saddrlen == sizeof(this_saddr)); |
| 187 | |
| 188 | assert(r <= buf_in.size); |
| 189 | buf_in.size= r; |
| 190 | cdebugbuf(-1, "decode", &buf_in, 3,0); |
| 191 | for (i=n_mechs-1; i>=0; i--) { |
| 192 | emsg= mechs[i]->decode(md_in[i],&buf_in); |
| 193 | if (emsg) { |
| 194 | fprintf(stderr, "%s: bad packet: %s: %s\n", programid, mechs[i]->name, emsg); |
| 195 | return; |
| 196 | } |
| 197 | cdebugbuf(i, "decode", &buf_in, 3,0); |
| 198 | } |
| 199 | |
| 200 | alarm(timeout); |
| 201 | |
| 202 | different= (!public_remote_specd || |
| 203 | public_remote.sin_addr.s_addr != this_saddr.sin_addr.s_addr || |
| 204 | public_remote.sin_port != this_saddr.sin_port); |
| 205 | |
| 206 | if (different) { |
| 207 | |
| 208 | if (public_remote_specd==2) { |
| 209 | fprintf(stderr, "%s: packet from unexpected sender %s:%lu\n", |
| 210 | programid, inet_ntoa(this_saddr.sin_addr), |
| 211 | (unsigned long)ntohs(this_saddr.sin_port)); |
| 212 | return; |
| 213 | } |
| 214 | |
| 215 | fprintf(stderr, "%s: tunnel open with peer %s:%lu\n", |
| 216 | programid, inet_ntoa(this_saddr.sin_addr), |
| 217 | (unsigned long)ntohs(this_saddr.sin_port)); |
| 218 | nextsendka= now(); |
| 219 | public_remote_specd= 1; |
| 220 | memcpy(&public_remote,&this_saddr,sizeof(public_remote)); |
| 221 | |
| 222 | } else if (!any_recvd) { |
| 223 | |
| 224 | diag("tunnel open"); |
| 225 | |
| 226 | } |
| 227 | |
| 228 | any_recvd= 1; |
| 229 | |
| 230 | if (!buf_in.size || *buf_in.start != 0300) { |
| 231 | *--buf_in.start= 0300; |
| 232 | buf_in.size++; |
| 233 | } |
| 234 | if (buf_in.start[buf_in.size-1] != 0300) { |
| 235 | buf_in.start[buf_in.size++]= 0300; |
| 236 | } |
| 237 | |
| 238 | setnonblock(private_in_fd,0); |
| 239 | write_must(private_in_fd, buf_in.start, buf_in.size, "write down"); |
| 240 | } |
| 241 | |
| 242 | static void sendpacket(const unsigned char *message, size_t size) { |
| 243 | int i, r; |
| 244 | |
| 245 | buf_out.start= buf_out.base+maxprefix; |
| 246 | buf_out.size= size; |
| 247 | memcpy(buf_out.start, message, size); |
| 248 | |
| 249 | nextsendka= now() + keepalive; |
| 250 | |
| 251 | cdebugbuf(-1, "encode", &buf_out, 4,0); |
| 252 | for (i=0; i<n_mechs; i++) { |
| 253 | mechs[i]->encode(md_out[i],&buf_out); |
| 254 | cdebugbuf(i, "encode", &buf_out, 4,0); |
| 255 | } |
| 256 | assert(public_remote_specd); |
| 257 | |
| 258 | setnonblock(public_local_fd,1); |
| 259 | for (;;) { |
| 260 | r= sendto(public_local_fd, buf_out.start, buf_out.size, 0, |
| 261 | &public_remote, sizeof(public_remote)); |
| 262 | if (r == buf_out.size) break; |
| 263 | if (r >= 0) { diag("unexpected short send"); return; } |
| 264 | if (errno != EINTR) { sysdiag("send"); return; } |
| 265 | } |
| 266 | } |
| 267 | |
| 268 | static void outbound(void) { |
| 269 | int r; |
| 270 | unsigned char *after_eaten, *delim; |
| 271 | size_t this_packet; |
| 272 | |
| 273 | setnonblock(private_out_fd,1); |
| 274 | |
| 275 | for (;;) { |
| 276 | r= read(private_out_fd, accum_buf + accum_used, accum_avail - accum_used); |
| 277 | if (!r) { diag("outbound datastream closed, quitting"); exit(0); } |
| 278 | if (r<0) { |
| 279 | if (errno == EAGAIN) return; |
| 280 | if (errno == EINTR) continue; |
| 281 | } |
| 282 | accum_used += r; |
| 283 | assert(accum_used<=accum_avail); |
| 284 | |
| 285 | after_eaten= accum_buf; |
| 286 | while ((delim= memchr(after_eaten, 0300, accum_used))) { |
| 287 | this_packet= delim - after_eaten; |
| 288 | if (this_packet) sendpacket(after_eaten, this_packet); |
| 289 | accum_used -= this_packet+1; |
| 290 | after_eaten = delim+1; |
| 291 | } |
| 292 | memmove(accum_buf, after_eaten, accum_used); |
| 293 | |
| 294 | if (accum_used == accum_avail) { |
| 295 | diag("missing interpacket delimiter in output datastream"); |
| 296 | accum_used= 0; |
| 297 | } |
| 298 | } |
| 299 | } |
| 300 | |
| 301 | int main(int argc, const char *const *const argv_in) { |
| 302 | const char *arg; |
| 303 | const char *const *argv_save; |
| 304 | const char *const *argv_done; |
| 305 | struct pollfd pollfds[2]; |
| 306 | int i, polltimeout, r; |
| 307 | time_t tnow; |
| 308 | |
| 309 | argv= argv_in; |
| 310 | |
| 311 | if (uname(&uname_result)) { perror(PROGRAM ": uname failed"); exit(16); } |
| 312 | sprintf(programid, PROGRAM ": %.*s", SYS_NMLN, uname_result.nodename); |
| 313 | |
| 314 | opt_chars= getarg_string(); |
| 315 | encdec_keys_write= !!strchr(opt_chars,'w'); |
| 316 | crypto_debug= !!strchr(opt_chars,'K'); |
| 317 | |
| 318 | public_local_fd= getarg_ulong(); |
| 319 | private_in_fd= getarg_ulong(); |
| 320 | private_out_fd= getarg_ulong(); |
| 321 | encdec_keys_fd= getarg_ulong(); |
| 322 | |
| 323 | mtu2= getarg_ulong() * 2; |
| 324 | keepalive= getarg_ulong(); |
| 325 | timeout= getarg_ulong(); |
| 326 | |
| 327 | arg= getarg_string(); |
| 328 | if (*arg) { |
| 329 | public_remote_specd= 1; |
| 330 | public_remote.sin_family= AF_INET; |
| 331 | arg_assert(inet_aton(arg,&public_remote.sin_addr)); |
| 332 | public_remote.sin_port= htons(getarg_ulong()); |
| 333 | } |
| 334 | |
| 335 | if (crypto_debug) { |
| 336 | diag("crypto debugging enabled!"); |
| 337 | setvbuf(stdout,0,_IOLBF,0); |
| 338 | } |
| 339 | |
| 340 | maxprefix= 0; |
| 341 | i= 0; |
| 342 | while ((arg= *++argv)) { |
| 343 | arg_assert(*arg++ == '|'); |
| 344 | arg_assert(i <= MAXMECHS); |
| 345 | mechs[i]= find_mech(arg); |
| 346 | |
| 347 | cdebug(i,"writer->reader setup"); |
| 348 | argv_save= argv; |
| 349 | |
| 350 | if (encdec_keys_write) |
| 351 | mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix); |
| 352 | else |
| 353 | mechs[i]->decsetup(&md_in[i]); |
| 354 | |
| 355 | argv_done= argv; |
| 356 | argv= argv_save; |
| 357 | cdebug(i,"reader->writer setup"); |
| 358 | |
| 359 | if (encdec_keys_write) |
| 360 | mechs[i]->decsetup(&md_in[i]); |
| 361 | else |
| 362 | mechs[i]->encsetup(&md_out[i], &maxprefix, &maxsuffix); |
| 363 | |
| 364 | assert(argv == argv_done); |
| 365 | |
| 366 | i++; |
| 367 | } |
| 368 | n_mechs= i; |
| 369 | |
| 370 | if (maxprefix<1) maxprefix= 1; |
| 371 | if (maxsuffix<1) maxsuffix= 1; |
| 372 | buffer_size= mtu2 + maxprefix + maxsuffix; |
| 373 | buf_in.base= xmalloc(buffer_size); |
| 374 | buf_out.base= xmalloc(buffer_size); |
| 375 | accum_avail= mtu2 + 1; |
| 376 | accum_buf= xmalloc(accum_avail); |
| 377 | |
| 378 | alarm(timeout); |
| 379 | |
| 380 | pollfds[0].fd= public_local_fd; |
| 381 | pollfds[0].events= POLLIN; |
| 382 | pollfds[1].fd= private_out_fd; |
| 383 | for (;;) { |
| 384 | pollfds[1].events= public_remote_specd ? POLLIN : 0; |
| 385 | pollfds[0].revents= 0; |
| 386 | pollfds[1].revents= 0; |
| 387 | |
| 388 | if (keepalive) { |
| 389 | tnow= now(); |
| 390 | if (tnow >= nextsendka && public_remote_specd) sendpacket("\300",1); |
| 391 | polltimeout= (nextsendka - tnow)*1000; |
| 392 | } else { |
| 393 | polltimeout= -1; |
| 394 | } |
| 395 | |
| 396 | r= poll(pollfds,2,polltimeout); |
| 397 | if (!r) continue; |
| 398 | if (r==-1 && errno==EINTR) continue; |
| 399 | if (r==-1) sysfail("poll"); |
| 400 | |
| 401 | if (pollfds[0].revents & (POLLIN|POLLERR)) inbound(); |
| 402 | if (pollfds[1].revents & (POLLIN|POLLERR)) outbound(); |
| 403 | } |
| 404 | } |