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

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