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.
  37      */
  38     char *hostname;
  39     int port;
  40     /*
  41      * `socksbuf' is the buffer we use to accumulate a SOCKS request.
  42      */
  43     char *socksbuf;
  44     int sockslen, sockssize;
  45     /*
  46      * When doing dynamic port forwarding, we can receive
  47      * connection data before we are actually able to send it; so
  48      * we may have to temporarily hold some in a dynamically
  49      * allocated buffer here.
  50      */
  51     void *buffer;
  52     int buflen;
  53 };
  54
  55 static struct PFwdPrivate *new_portfwd_private(void)
  56 {
  57     struct PFwdPrivate *pr = snew(struct PFwdPrivate);
  58     pr->hostname = NULL;
  59     pr->socksbuf = NULL;
  60     pr->sockslen = pr->sockssize = 0;
  61     pr->buffer = NULL;
  62     return pr;
  63 }
  64
  65 static void free_portfwd_private(struct PFwdPrivate *pr)
  66 {
  67     if (!pr)
  68         return;
  69     sfree(pr->hostname);
  70     sfree(pr->socksbuf);
  71     sfree(pr->buffer);
  72     sfree(pr);
  73 }
  74
  75 static void pfd_log(Plug plug, int type, SockAddr addr, int port,
  76                     const char *error_msg, int error_code)
  77 {
  78     /* we have to dump these since we have no interface to logging.c */
  79 }
  80
  81 static int pfd_closing(Plug plug, const char *error_msg, int error_code,
  82                        int calling_back)
  83 {
  84     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
  85
  86     if (error_msg) {
  87         /*
  88          * Socket error. Slam the connection instantly shut.
  89          */
  90         sshfwd_unclean_close(pr->c);
  91     } else {
  92         /*
  93          * Ordinary EOF received on socket. Send an EOF on the SSH
  94          * channel.
  95          */
  96         if (pr->c)
  97             sshfwd_write_eof(pr->c);
  98     }
  99
 100     return 1;
 101 }
 102
 103 static int pfd_receive(Plug plug, int urgent, char *data, int len)
 104 {
 105     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
 106     if (pr->dynamic) {
 107         while (len--) {
 108             if (pr->sockslen >= pr->sockssize) {
 109                 pr->sockssize = pr->sockslen * 5 / 4 + 256;
 110                 pr->socksbuf = sresize(pr->socksbuf, pr->sockssize, char);
 111             }
 112             pr->socksbuf[pr->sockslen++] = *data++;
 113
 114             /*
 115              * Now check what's in the buffer to see if it's a
 116              * valid and complete message in the SOCKS exchange.
 117              */
 118             if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 4) &&
 119                 pr->socksbuf[0] == 4) {
 120                 /*
 121                  * SOCKS 4.
 122                  */
 123                 if (pr->dynamic == 1)
 124                     pr->dynamic = 0x4000;
 125                 if (pr->sockslen < 2)
 126                     continue;        /* don't have command code yet */
 127                 if (pr->socksbuf[1] != 1) {
 128                     /* Not CONNECT. */
 129                     /* Send back a SOCKS 4 error before closing. */
 130                     char data[8];
 131                     memset(data, 0, sizeof(data));
 132                     data[1] = 91;      /* generic `request rejected' */
 133                     sk_write(pr->s, data, 8);
 134                     pfd_close(pr->s);
 135                     return 1;
 136                 }
 137                 if (pr->sockslen <= 8)
 138                     continue;      /* haven't started user/hostname */
 139                 if (pr->socksbuf[pr->sockslen-1] != 0)
 140                     continue;          /* haven't _finished_ user/hostname */
 141                 /*
 142                  * Now we have a full SOCKS 4 request. Check it to
 143                  * see if it's a SOCKS 4A request.
 144                  */
 145                 if (pr->socksbuf[4] == 0 && pr->socksbuf[5] == 0 &&
 146                     pr->socksbuf[6] == 0 && pr->socksbuf[7] != 0) {
 147                     /*
 148                      * It's SOCKS 4A. So if we haven't yet
 149                      * collected the host name, we should continue
 150                      * waiting for data in order to do so; if we
 151                      * have, we can go ahead.
 152                      */
 153                     int len;
 154                     if (pr->dynamic == 0x4000) {
 155                         pr->dynamic = 0x4001;
 156                         pr->sockslen = 8; /* reset buffer to overwrite name */
 157                         continue;
 158                     }
 159                     pr->socksbuf[0] = 0;   /* reply version code */
 160                     pr->socksbuf[1] = 90;   /* request granted */
 161                     sk_write(pr->s, pr->socksbuf, 8);
 162                     len = pr->sockslen - 8;
 163                     pr->port = GET_16BIT_MSB_FIRST(pr->socksbuf+2);
 164                     pr->hostname = snewn(len+1, char);
 165                     pr->hostname[len] = '\0';
 166                     memcpy(pr->hostname, pr->socksbuf + 8, len);
 167                     goto connect;
 168                 } else {
 169                     /*
 170                      * It's SOCKS 4, which means we should format
 171                      * the IP address into the hostname string and
 172                      * then just go.
 173                      */
 174                     pr->socksbuf[0] = 0;   /* reply version code */
 175                     pr->socksbuf[1] = 90;   /* request granted */
 176                     sk_write(pr->s, pr->socksbuf, 8);
 177                     pr->port = GET_16BIT_MSB_FIRST(pr->socksbuf+2);
 178                     pr->hostname = dupprintf("%d.%d.%d.%d",
 179                                              (unsigned char)pr->socksbuf[4],
 180                                              (unsigned char)pr->socksbuf[5],
 181                                              (unsigned char)pr->socksbuf[6],
 182                                              (unsigned char)pr->socksbuf[7]);
 183                     goto connect;
 184                 }
 185             }
 186
 187             if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 5) &&
 188                 pr->socksbuf[0] == 5) {
 189                 /*
 190                  * SOCKS 5.
 191                  */
 192                 if (pr->dynamic == 1)
 193                     pr->dynamic = 0x5000;
 194
 195                 if (pr->dynamic == 0x5000) {
 196                     int i, method;
 197                     char data[2];
 198                     /*
 199                      * We're receiving a set of method identifiers.
 200                      */
 201                     if (pr->sockslen < 2)
 202                         continue;      /* no method count yet */
 203                     if (pr->sockslen < 2 + (unsigned char)pr->socksbuf[1])
 204                         continue;      /* no methods yet */
 205                     method = 0xFF;     /* invalid */
 206                     for (i = 0; i < (unsigned char)pr->socksbuf[1]; i++)
 207                         if (pr->socksbuf[2+i] == 0) {
 208                             method = 0;/* no auth */
 209                             break;
 210                         }
 211                     data[0] = 5;
 212                     data[1] = method;
 213                     sk_write(pr->s, data, 2);
 214                     pr->dynamic = 0x5001;
 215                     pr->sockslen = 0;      /* re-empty the buffer */
 216                     continue;
 217                 }
 218
 219                 if (pr->dynamic == 0x5001) {
 220                     /*
 221                      * We're receiving a SOCKS request.
 222                      */
 223                     unsigned char reply[10]; /* SOCKS5 atyp=1 reply */
 224                     int atype, alen = 0;
 225
 226                     /*
 227                      * Pre-fill reply packet.
 228                      * In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0
 229                      * (atyp=1) in the reply; if we succeed, we don't know
 230                      * the right answers, and if we fail, they should be
 231                      * ignored.
 232                      */
 233                     memset(reply, 0, lenof(reply));
 234                     reply[0] = 5; /* VER */
 235                     reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */
 236
 237                     if (pr->sockslen < 6) continue;
 238                     atype = (unsigned char)pr->socksbuf[3];
 239                     if (atype == 1)    /* IPv4 address */
 240                         alen = 4;
 241                     if (atype == 4)    /* IPv6 address */
 242                         alen = 16;
 243                     if (atype == 3)    /* domain name has leading length */
 244                         alen = 1 + (unsigned char)pr->socksbuf[4];
 245                     if (pr->sockslen < 6 + alen) continue;
 246                     if (pr->socksbuf[1] != 1 || pr->socksbuf[2] != 0) {
 247                         /* Not CONNECT or reserved field nonzero - error */
 248                         reply[1] = 1;   /* generic failure */
 249                         sk_write(pr->s, (char *) reply, lenof(reply));
 250                         pfd_close(pr->s);
 251                         return 1;
 252                     }
 253                     /*
 254                      * Now we have a viable connect request. Switch
 255                      * on atype.
 256                      */
 257                     pr->port = GET_16BIT_MSB_FIRST(pr->socksbuf+4+alen);
 258                     if (atype == 1) {
 259                         /* REP=0 (success) already */
 260                         sk_write(pr->s, (char *) reply, lenof(reply));
 261                         pr->hostname = dupprintf("%d.%d.%d.%d",
 262                                                  (unsigned char)pr->socksbuf[4],
 263                                                  (unsigned char)pr->socksbuf[5],
 264                                                  (unsigned char)pr->socksbuf[6],
 265                                                  (unsigned char)pr->socksbuf[7]);
 266                         goto connect;
 267                     } else if (atype == 3) {
 268                         /* REP=0 (success) already */
 269                         sk_write(pr->s, (char *) reply, lenof(reply));
 270                         pr->hostname = snewn(alen, char);
 271                         pr->hostname[alen-1] = '\0';
 272                         memcpy(pr->hostname, pr->socksbuf + 5, alen-1);
 273                         goto connect;
 274                     } else {
 275                         /*
 276                          * Unknown address type. (FIXME: support IPv6!)
 277                          */
 278                         reply[1] = 8;   /* atype not supported */
 279                         sk_write(pr->s, (char *) reply, lenof(reply));
 280                         pfd_close(pr->s);
 281                         return 1;
 282                     }
 283                 }
 284             }
 285
 286             /*
 287              * If we get here without either having done `continue'
 288              * or `goto connect', it must be because there is no
 289              * sensible interpretation of what's in our buffer. So
 290              * close the connection rudely.
 291              */
 292             pfd_close(pr->s);
 293             return 1;
 294         }
 295         return 1;
 296
 297         /*
 298          * We come here when we're ready to make an actual
 299          * connection.
 300          */
 301         connect:
 302         sfree(pr->socksbuf);
 303         pr->socksbuf = NULL;
 304
 305         /*
 306          * Freeze the socket until the SSH server confirms the
 307          * connection.
 308          */
 309         sk_set_frozen(pr->s, 1);
 310
 311         pr->c = new_sock_channel(pr->backhandle, pr->s);
 312         if (pr->c == NULL) {
 313             pfd_close(pr->s);
 314             return 1;
 315         } else {
 316             /* asks to forward to the specified host/port for this */
 317             ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
 318         }
 319         pr->dynamic = 0;
 320
 321         /*
 322          * If there's any data remaining in our current buffer,
 323          * save it to be sent on pfd_confirm().
 324          */
 325         if (len > 0) {
 326             pr->buffer = snewn(len, char);
 327             memcpy(pr->buffer, data, len);
 328             pr->buflen = len;
 329         }
 330     }
 331     if (pr->ready) {
 332         if (sshfwd_write(pr->c, data, len) > 0) {
 333             pr->throttled = 1;
 334             sk_set_frozen(pr->s, 1);
 335         }
 336     }
 337     return 1;
 338 }
 339
 340 static void pfd_sent(Plug plug, int bufsize)
 341 {
 342     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
 343
 344     if (pr->c)
 345         sshfwd_unthrottle(pr->c, bufsize);
 346 }
 347
 348 /*
 349  * Called when receiving a PORT OPEN from the server
 350  */
 351 const char *pfd_newconnect(Socket *s, char *hostname, int port,
 352                            void *c, Conf *conf, int addressfamily)
 353 {
 354     static const struct plug_function_table fn_table = {
 355         pfd_log,
 356         pfd_closing,
 357         pfd_receive,
 358         pfd_sent,
 359         NULL
 360     };
 361
 362     SockAddr addr;
 363     const char *err;
 364     char *dummy_realhost;
 365     struct PFwdPrivate *pr;
 366
 367     /*
 368      * Try to find host.
 369      */
 370     addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily);
 371     if ((err = sk_addr_error(addr)) != NULL) {
 372         sk_addr_free(addr);
 373         sfree(dummy_realhost);
 374         return err;
 375     }
 376
 377     /*
 378      * Open socket.
 379      */
 380     pr = new_portfwd_private();
 381     pr->fn = &fn_table;
 382     pr->throttled = pr->throttle_override = 0;
 383     pr->ready = 1;
 384     pr->c = c;
 385     pr->backhandle = NULL;             /* we shouldn't need this */
 386     pr->dynamic = 0;
 387
 388     pr->s = *s = new_connection(addr, dummy_realhost, port,
 389                                 0, 1, 0, 0, (Plug) pr, conf);
 390     sfree(dummy_realhost);
 391     if ((err = sk_socket_error(*s)) != NULL) {
 392         free_portfwd_private(pr);
 393         return err;
 394     }
 395
 396     sk_set_private_ptr(*s, pr);
 397     return NULL;
 398 }
 399
 400 /*
 401  called when someone connects to the local port
 402  */
 403
 404 static int pfd_accepting(Plug p, OSSocket sock)
 405 {
 406     static const struct plug_function_table fn_table = {
 407         pfd_log,
 408         pfd_closing,
 409         pfd_receive,
 410         pfd_sent,
 411         NULL
 412     };
 413     struct PFwdPrivate *pr, *org;
 414     Socket s;
 415     const char *err;
 416
 417     org = (struct PFwdPrivate *)p;
 418     pr = new_portfwd_private();
 419     pr->fn = &fn_table;
 420
 421     pr->c = NULL;
 422     pr->backhandle = org->backhandle;
 423
 424     pr->s = s = sk_register(sock, (Plug) pr);
 425     if ((err = sk_socket_error(s)) != NULL) {
 426         free_portfwd_private(pr);
 427         return err != NULL;
 428     }
 429
 430     sk_set_private_ptr(s, pr);
 431
 432     pr->throttled = pr->throttle_override = 0;
 433     pr->ready = 0;
 434
 435     if (org->dynamic) {
 436         pr->dynamic = 1;
 437         pr->port = 0;                  /* "hostname" buffer is so far empty */
 438         sk_set_frozen(s, 0);           /* we want to receive SOCKS _now_! */
 439     } else {
 440         pr->dynamic = 0;
 441         pr->hostname = dupstr(org->hostname);
 442         pr->port = org->port;
 443         pr->c = new_sock_channel(org->backhandle, s);
 444
 445         if (pr->c == NULL) {
 446             free_portfwd_private(pr);
 447             return 1;
 448         } else {
 449             /* asks to forward to the specified host/port for this */
 450             ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
 451         }
 452     }
 453
 454     return 0;
 455 }
 456
 457
 458 /* Add a new forwarding from port -> desthost:destport
 459  sets up a listener on the local machine on (srcaddr:)port
 460  */
 461 const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
 462                            int port, void *backhandle, Conf *conf,
 463                            void **sockdata, int address_family)
 464 {
 465     static const struct plug_function_table fn_table = {
 466         pfd_log,
 467         pfd_closing,
 468         pfd_receive,                   /* should not happen... */
 469         pfd_sent,                      /* also should not happen */
 470         pfd_accepting
 471     };
 472
 473     const char *err;
 474     struct PFwdPrivate *pr;
 475     Socket s;
 476
 477     /*
 478      * Open socket.
 479      */
 480     pr = new_portfwd_private();
 481     pr->fn = &fn_table;
 482     pr->c = NULL;
 483     if (desthost) {
 484         pr->hostname = dupstr(desthost);
 485         pr->port = destport;
 486         pr->dynamic = 0;
 487     } else
 488         pr->dynamic = 1;
 489     pr->throttled = pr->throttle_override = 0;
 490     pr->ready = 0;
 491     pr->backhandle = backhandle;
 492
 493     pr->s = s = new_listener(srcaddr, port, (Plug) pr,
 494                              !conf_get_int(conf, CONF_lport_acceptall),
 495                              conf, address_family);
 496     if ((err = sk_socket_error(s)) != NULL) {
 497         free_portfwd_private(pr);
 498         return err;
 499     }
 500
 501     sk_set_private_ptr(s, pr);
 502
 503     *sockdata = (void *)s;
 504
 505     return NULL;
 506 }
 507
 508 void pfd_close(Socket s)
 509 {
 510     struct PFwdPrivate *pr;
 511
 512     if (!s)
 513         return;
 514
 515     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 516
 517     free_portfwd_private(pr);
 518
 519     sk_close(s);
 520 }
 521
 522 /*
 523  * Terminate a listener.
 524  */
 525 void pfd_terminate(void *sv)
 526 {
 527     pfd_close((Socket)sv);
 528 }
 529
 530 void pfd_unthrottle(Socket s)
 531 {
 532     struct PFwdPrivate *pr;
 533     if (!s)
 534         return;
 535     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 536
 537     pr->throttled = 0;
 538     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 539 }
 540
 541 void pfd_override_throttle(Socket s, int enable)
 542 {
 543     struct PFwdPrivate *pr;
 544     if (!s)
 545         return;
 546     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 547
 548     pr->throttle_override = enable;
 549     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 550 }
 551
 552 /*
 553  * Called to send data down the raw connection.
 554  */
 555 int pfd_send(Socket s, char *data, int len)
 556 {
 557     if (s == NULL)
 558         return 0;
 559     return sk_write(s, data, len);
 560 }
 561
 562 void pfd_send_eof(Socket s)
 563 {
 564     sk_write_eof(s);
 565 }
 566
 567 void pfd_confirm(Socket s)
 568 {
 569     struct PFwdPrivate *pr;
 570
 571     if (s == NULL)
 572         return;
 573
 574     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 575     pr->ready = 1;
 576     sk_set_frozen(s, 0);
 577     sk_write(s, NULL, 0);
 578     if (pr->buffer) {
 579         sshfwd_write(pr->c, pr->buffer, pr->buflen);
 580         sfree(pr->buffer);
 581         pr->buffer = NULL;
 582     }
 583 }