git.distorted.org.uk Git - u/mdw/putty/blob - portfwd.c

   1 /*
   2  * SSH port forwarding.
   3  */
   4
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7
   8 #include "putty.h"
   9 #include "ssh.h"
  10
  11 #ifndef FALSE
  12 #define FALSE 0
  13 #endif
  14 #ifndef TRUE
  15 #define TRUE 1
  16 #endif
  17
  18 struct PFwdPrivate {
  19     const struct plug_function_table *fn;
  20     /* the above variable absolutely *must* be the first in this structure */
  21     void *c;                           /* (channel) data used by ssh.c */
  22     void *backhandle;                  /* instance of SSH backend itself */
  23     /* Note that backhandle need not be filled in if c is non-NULL */
  24     Socket s;
  25     int throttled, throttle_override;
  26     int ready;
  27     /*
  28      * `dynamic' does double duty. It's set to 0 for an ordinary
  29      * forwarded port, and nonzero for SOCKS-style dynamic port
  30      * forwarding; but it also represents the state of the SOCKS
  31      * exchange.
  32      */
  33     int dynamic;
  34     /*
  35      * `hostname' and `port' are the real hostname and port, once
  36      * we know what we're connecting to; they're unused for this
  37      * purpose while conducting a local SOCKS exchange, which means
  38      * we can also use them as a buffer and pointer for reading
  39      * data from the SOCKS client.
  40      */
  41     char hostname[256+8];
  42     int port;
  43     /*
  44      * When doing dynamic port forwarding, we can receive
  45      * connection data before we are actually able to send it; so
  46      * we may have to temporarily hold some in a dynamically
  47      * allocated buffer here.
  48      */
  49     void *buffer;
  50     int buflen;
  51 };
  52
  53 static void pfd_log(Plug plug, int type, SockAddr addr, int port,
  54                     const char *error_msg, int error_code)
  55 {
  56     /* we have to dump these since we have no interface to logging.c */
  57 }
  58
  59 static int pfd_closing(Plug plug, const char *error_msg, int error_code,
  60                        int calling_back)
  61 {
  62     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
  63
  64     /*
  65      * We have no way to communicate down the forwarded connection,
  66      * so if an error occurred on the socket, we just ignore it
  67      * and treat it like a proper close.
  68      *
  69      * FIXME: except we could initiate a full close here instead of
  70      * just an outgoing EOF? ssh.c currently has no API for that, but
  71      * it could.
  72      */
  73     if (pr->c)
  74         sshfwd_write_eof(pr->c);
  75
  76     return 1;
  77 }
  78
  79 static int pfd_receive(Plug plug, int urgent, char *data, int len)
  80 {
  81     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
  82     if (pr->dynamic) {
  83         while (len--) {
  84             /*
  85              * Throughout SOCKS negotiation, "hostname" is re-used as a
  86              * random protocol buffer with "port" storing the length.
  87              */
  88             if (pr->port >= lenof(pr->hostname)) {
  89                 /* Request too long. */
  90                 if ((pr->dynamic >> 12) == 4) {
  91                     /* Send back a SOCKS 4 error before closing. */
  92                     char data[8];
  93                     memset(data, 0, sizeof(data));
  94                     data[1] = 91;      /* generic `request rejected' */
  95                     sk_write(pr->s, data, 8);
  96                 }
  97                 pfd_close(pr->s);
  98                 return 1;
  99             }
 100             pr->hostname[pr->port++] = *data++;
 101
 102             /*
 103              * Now check what's in the buffer to see if it's a
 104              * valid and complete message in the SOCKS exchange.
 105              */
 106             if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 4) &&
 107                 pr->hostname[0] == 4) {
 108                 /*
 109                  * SOCKS 4.
 110                  */
 111                 if (pr->dynamic == 1)
 112                     pr->dynamic = 0x4000;
 113                 if (pr->port < 2) continue;/* don't have command code yet */
 114                 if (pr->hostname[1] != 1) {
 115                     /* Not CONNECT. */
 116                     /* Send back a SOCKS 4 error before closing. */
 117                     char data[8];
 118                     memset(data, 0, sizeof(data));
 119                     data[1] = 91;      /* generic `request rejected' */
 120                     sk_write(pr->s, data, 8);
 121                     pfd_close(pr->s);
 122                     return 1;
 123                 }
 124                 if (pr->port <= 8) continue; /* haven't started user/hostname */
 125                 if (pr->hostname[pr->port-1] != 0)
 126                     continue;          /* haven't _finished_ user/hostname */
 127                 /*
 128                  * Now we have a full SOCKS 4 request. Check it to
 129                  * see if it's a SOCKS 4A request.
 130                  */
 131                 if (pr->hostname[4] == 0 && pr->hostname[5] == 0 &&
 132                     pr->hostname[6] == 0 && pr->hostname[7] != 0) {
 133                     /*
 134                      * It's SOCKS 4A. So if we haven't yet
 135                      * collected the host name, we should continue
 136                      * waiting for data in order to do so; if we
 137                      * have, we can go ahead.
 138                      */
 139                     int len;
 140                     if (pr->dynamic == 0x4000) {
 141                         pr->dynamic = 0x4001;
 142                         pr->port = 8;      /* reset buffer to overwrite name */
 143                         continue;
 144                     }
 145                     pr->hostname[0] = 0;   /* reply version code */
 146                     pr->hostname[1] = 90;   /* request granted */
 147                     sk_write(pr->s, pr->hostname, 8);
 148                     len= pr->port - 8;
 149                     pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
 150                     memmove(pr->hostname, pr->hostname + 8, len);
 151                     goto connect;
 152                 } else {
 153                     /*
 154                      * It's SOCKS 4, which means we should format
 155                      * the IP address into the hostname string and
 156                      * then just go.
 157                      */
 158                     pr->hostname[0] = 0;   /* reply version code */
 159                     pr->hostname[1] = 90;   /* request granted */
 160                     sk_write(pr->s, pr->hostname, 8);
 161                     pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
 162                     sprintf(pr->hostname, "%d.%d.%d.%d",
 163                             (unsigned char)pr->hostname[4],
 164                             (unsigned char)pr->hostname[5],
 165                             (unsigned char)pr->hostname[6],
 166                             (unsigned char)pr->hostname[7]);
 167                     goto connect;
 168                 }
 169             }
 170
 171             if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 5) &&
 172                 pr->hostname[0] == 5) {
 173                 /*
 174                  * SOCKS 5.
 175                  */
 176                 if (pr->dynamic == 1)
 177                     pr->dynamic = 0x5000;
 178
 179                 if (pr->dynamic == 0x5000) {
 180                     int i, method;
 181                     char data[2];
 182                     /*
 183                      * We're receiving a set of method identifiers.
 184                      */
 185                     if (pr->port < 2) continue;/* no method count yet */
 186                     if (pr->port < 2 + (unsigned char)pr->hostname[1])
 187                         continue;      /* no methods yet */
 188                     method = 0xFF;     /* invalid */
 189                     for (i = 0; i < (unsigned char)pr->hostname[1]; i++)
 190                         if (pr->hostname[2+i] == 0) {
 191                             method = 0;/* no auth */
 192                             break;
 193                         }
 194                     data[0] = 5;
 195                     data[1] = method;
 196                     sk_write(pr->s, data, 2);
 197                     pr->dynamic = 0x5001;
 198                     pr->port = 0;      /* re-empty the buffer */
 199                     continue;
 200                 }
 201
 202                 if (pr->dynamic == 0x5001) {
 203                     /*
 204                      * We're receiving a SOCKS request.
 205                      */
 206                     unsigned char reply[10]; /* SOCKS5 atyp=1 reply */
 207                     int atype, alen = 0;
 208
 209                     /*
 210                      * Pre-fill reply packet.
 211                      * In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0
 212                      * (atyp=1) in the reply; if we succeed, we don't know
 213                      * the right answers, and if we fail, they should be
 214                      * ignored.
 215                      */
 216                     memset(reply, 0, lenof(reply));
 217                     reply[0] = 5; /* VER */
 218                     reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */
 219
 220                     if (pr->port < 6) continue;
 221                     atype = (unsigned char)pr->hostname[3];
 222                     if (atype == 1)    /* IPv4 address */
 223                         alen = 4;
 224                     if (atype == 4)    /* IPv6 address */
 225                         alen = 16;
 226                     if (atype == 3)    /* domain name has leading length */
 227                         alen = 1 + (unsigned char)pr->hostname[4];
 228                     if (pr->port < 6 + alen) continue;
 229                     if (pr->hostname[1] != 1 || pr->hostname[2] != 0) {
 230                         /* Not CONNECT or reserved field nonzero - error */
 231                         reply[1] = 1;   /* generic failure */
 232                         sk_write(pr->s, (char *) reply, lenof(reply));
 233                         pfd_close(pr->s);
 234                         return 1;
 235                     }
 236                     /*
 237                      * Now we have a viable connect request. Switch
 238                      * on atype.
 239                      */
 240                     pr->port = GET_16BIT_MSB_FIRST(pr->hostname+4+alen);
 241                     if (atype == 1) {
 242                         /* REP=0 (success) already */
 243                         sk_write(pr->s, (char *) reply, lenof(reply));
 244                         sprintf(pr->hostname, "%d.%d.%d.%d",
 245                                 (unsigned char)pr->hostname[4],
 246                                 (unsigned char)pr->hostname[5],
 247                                 (unsigned char)pr->hostname[6],
 248                                 (unsigned char)pr->hostname[7]);
 249                         goto connect;
 250                     } else if (atype == 3) {
 251                         /* REP=0 (success) already */
 252                         sk_write(pr->s, (char *) reply, lenof(reply));
 253                         memmove(pr->hostname, pr->hostname + 5, alen-1);
 254                         pr->hostname[alen-1] = '\0';
 255                         goto connect;
 256                     } else {
 257                         /*
 258                          * Unknown address type. (FIXME: support IPv6!)
 259                          */
 260                         reply[1] = 8;   /* atype not supported */
 261                         sk_write(pr->s, (char *) reply, lenof(reply));
 262                         pfd_close(pr->s);
 263                         return 1;
 264                     }
 265                 }
 266             }
 267
 268             /*
 269              * If we get here without either having done `continue'
 270              * or `goto connect', it must be because there is no
 271              * sensible interpretation of what's in our buffer. So
 272              * close the connection rudely.
 273              */
 274             pfd_close(pr->s);
 275             return 1;
 276         }
 277         return 1;
 278
 279         /*
 280          * We come here when we're ready to make an actual
 281          * connection.
 282          */
 283         connect:
 284
 285         /*
 286          * Freeze the socket until the SSH server confirms the
 287          * connection.
 288          */
 289         sk_set_frozen(pr->s, 1);
 290
 291         pr->c = new_sock_channel(pr->backhandle, pr->s);
 292         if (pr->c == NULL) {
 293             pfd_close(pr->s);
 294             return 1;
 295         } else {
 296             /* asks to forward to the specified host/port for this */
 297             ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
 298         }
 299         pr->dynamic = 0;
 300
 301         /*
 302          * If there's any data remaining in our current buffer,
 303          * save it to be sent on pfd_confirm().
 304          */
 305         if (len > 0) {
 306             pr->buffer = snewn(len, char);
 307             memcpy(pr->buffer, data, len);
 308             pr->buflen = len;
 309         }
 310     }
 311     if (pr->ready) {
 312         if (sshfwd_write(pr->c, data, len) > 0) {
 313             pr->throttled = 1;
 314             sk_set_frozen(pr->s, 1);
 315         }
 316     }
 317     return 1;
 318 }
 319
 320 static void pfd_sent(Plug plug, int bufsize)
 321 {
 322     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
 323
 324     if (pr->c)
 325         sshfwd_unthrottle(pr->c, bufsize);
 326 }
 327
 328 /*
 329  * Called when receiving a PORT OPEN from the server
 330  */
 331 const char *pfd_newconnect(Socket *s, char *hostname, int port,
 332                            void *c, Conf *conf, int addressfamily)
 333 {
 334     static const struct plug_function_table fn_table = {
 335         pfd_log,
 336         pfd_closing,
 337         pfd_receive,
 338         pfd_sent,
 339         NULL
 340     };
 341
 342     SockAddr addr;
 343     const char *err;
 344     char *dummy_realhost;
 345     struct PFwdPrivate *pr;
 346
 347     /*
 348      * Try to find host.
 349      */
 350     addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily);
 351     if ((err = sk_addr_error(addr)) != NULL) {
 352         sk_addr_free(addr);
 353         return err;
 354     }
 355
 356     /*
 357      * Open socket.
 358      */
 359     pr = snew(struct PFwdPrivate);
 360     pr->buffer = NULL;
 361     pr->fn = &fn_table;
 362     pr->throttled = pr->throttle_override = 0;
 363     pr->ready = 1;
 364     pr->c = c;
 365     pr->backhandle = NULL;             /* we shouldn't need this */
 366     pr->dynamic = 0;
 367
 368     pr->s = *s = new_connection(addr, dummy_realhost, port,
 369                                 0, 1, 0, 0, (Plug) pr, conf);
 370     if ((err = sk_socket_error(*s)) != NULL) {
 371         sfree(pr);
 372         return err;
 373     }
 374
 375     sk_set_private_ptr(*s, pr);
 376     return NULL;
 377 }
 378
 379 /*
 380  called when someone connects to the local port
 381  */
 382
 383 static int pfd_accepting(Plug p, OSSocket sock)
 384 {
 385     static const struct plug_function_table fn_table = {
 386         pfd_log,
 387         pfd_closing,
 388         pfd_receive,
 389         pfd_sent,
 390         NULL
 391     };
 392     struct PFwdPrivate *pr, *org;
 393     Socket s;
 394     const char *err;
 395
 396     org = (struct PFwdPrivate *)p;
 397     pr = snew(struct PFwdPrivate);
 398     pr->buffer = NULL;
 399     pr->fn = &fn_table;
 400
 401     pr->c = NULL;
 402     pr->backhandle = org->backhandle;
 403
 404     pr->s = s = sk_register(sock, (Plug) pr);
 405     if ((err = sk_socket_error(s)) != NULL) {
 406         sfree(pr);
 407         return err != NULL;
 408     }
 409
 410     sk_set_private_ptr(s, pr);
 411
 412     pr->throttled = pr->throttle_override = 0;
 413     pr->ready = 0;
 414
 415     if (org->dynamic) {
 416         pr->dynamic = 1;
 417         pr->port = 0;                  /* "hostname" buffer is so far empty */
 418         sk_set_frozen(s, 0);           /* we want to receive SOCKS _now_! */
 419     } else {
 420         pr->dynamic = 0;
 421         strcpy(pr->hostname, org->hostname);
 422         pr->port = org->port;
 423         pr->c = new_sock_channel(org->backhandle, s);
 424
 425         if (pr->c == NULL) {
 426             sfree(pr);
 427             return 1;
 428         } else {
 429             /* asks to forward to the specified host/port for this */
 430             ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
 431         }
 432     }
 433
 434     return 0;
 435 }
 436
 437
 438 /* Add a new forwarding from port -> desthost:destport
 439  sets up a listener on the local machine on (srcaddr:)port
 440  */
 441 const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
 442                            int port, void *backhandle, Conf *conf,
 443                            void **sockdata, int address_family)
 444 {
 445     static const struct plug_function_table fn_table = {
 446         pfd_log,
 447         pfd_closing,
 448         pfd_receive,                   /* should not happen... */
 449         pfd_sent,                      /* also should not happen */
 450         pfd_accepting
 451     };
 452
 453     const char *err;
 454     struct PFwdPrivate *pr;
 455     Socket s;
 456
 457     /*
 458      * Open socket.
 459      */
 460     pr = snew(struct PFwdPrivate);
 461     pr->buffer = NULL;
 462     pr->fn = &fn_table;
 463     pr->c = NULL;
 464     if (desthost) {
 465         strcpy(pr->hostname, desthost);
 466         pr->port = destport;
 467         pr->dynamic = 0;
 468     } else
 469         pr->dynamic = 1;
 470     pr->throttled = pr->throttle_override = 0;
 471     pr->ready = 0;
 472     pr->backhandle = backhandle;
 473
 474     pr->s = s = new_listener(srcaddr, port, (Plug) pr,
 475                              !conf_get_int(conf, CONF_lport_acceptall),
 476                              conf, address_family);
 477     if ((err = sk_socket_error(s)) != NULL) {
 478         sfree(pr);
 479         return err;
 480     }
 481
 482     sk_set_private_ptr(s, pr);
 483
 484     *sockdata = (void *)s;
 485
 486     return NULL;
 487 }
 488
 489 void pfd_close(Socket s)
 490 {
 491     struct PFwdPrivate *pr;
 492
 493     if (!s)
 494         return;
 495
 496     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 497
 498     sfree(pr->buffer);
 499     sfree(pr);
 500
 501     sk_close(s);
 502 }
 503
 504 /*
 505  * Terminate a listener.
 506  */
 507 void pfd_terminate(void *sv)
 508 {
 509     pfd_close((Socket)sv);
 510 }
 511
 512 void pfd_unthrottle(Socket s)
 513 {
 514     struct PFwdPrivate *pr;
 515     if (!s)
 516         return;
 517     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 518
 519     pr->throttled = 0;
 520     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 521 }
 522
 523 void pfd_override_throttle(Socket s, int enable)
 524 {
 525     struct PFwdPrivate *pr;
 526     if (!s)
 527         return;
 528     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 529
 530     pr->throttle_override = enable;
 531     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 532 }
 533
 534 /*
 535  * Called to send data down the raw connection.
 536  */
 537 int pfd_send(Socket s, char *data, int len)
 538 {
 539     if (s == NULL)
 540         return 0;
 541     return sk_write(s, data, len);
 542 }
 543
 544 void pfd_send_eof(Socket s)
 545 {
 546     sk_write_eof(s);
 547 }
 548
 549 void pfd_confirm(Socket s)
 550 {
 551     struct PFwdPrivate *pr;
 552
 553     if (s == NULL)
 554         return;
 555
 556     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 557     pr->ready = 1;
 558     sk_set_frozen(s, 0);
 559     sk_write(s, NULL, 0);
 560     if (pr->buffer) {
 561         sshfwd_write(pr->c, pr->buffer, pr->buflen);
 562         sfree(pr->buffer);
 563         pr->buffer = NULL;
 564     }
 565 }