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         if (pr->c) {
  91             sshfwd_unclean_close(pr->c);
  92         } else {
  93             /*
  94              * We might not have an SSH channel, if a socket error
  95              * occurred during SOCKS negotiation. If not, we must
  96              * clean ourself up without sshfwd_unclean_close's call
  97              * back to pfd_close.
  98              */
  99             pfd_close(pr->s);
 100         }
 101     } else {
 102         /*
 103          * Ordinary EOF received on socket. Send an EOF on the SSH
 104          * channel.
 105          */
 106         if (pr->c)
 107             sshfwd_write_eof(pr->c);
 108     }
 109
 110     return 1;
 111 }
 112
 113 static int pfd_receive(Plug plug, int urgent, char *data, int len)
 114 {
 115     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
 116     if (pr->dynamic) {
 117         while (len--) {
 118             if (pr->sockslen >= pr->sockssize) {
 119                 pr->sockssize = pr->sockslen * 5 / 4 + 256;
 120                 pr->socksbuf = sresize(pr->socksbuf, pr->sockssize, char);
 121             }
 122             pr->socksbuf[pr->sockslen++] = *data++;
 123
 124             /*
 125              * Now check what's in the buffer to see if it's a
 126              * valid and complete message in the SOCKS exchange.
 127              */
 128             if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 4) &&
 129                 pr->socksbuf[0] == 4) {
 130                 /*
 131                  * SOCKS 4.
 132                  */
 133                 if (pr->dynamic == 1)
 134                     pr->dynamic = 0x4000;
 135                 if (pr->sockslen < 2)
 136                     continue;        /* don't have command code yet */
 137                 if (pr->socksbuf[1] != 1) {
 138                     /* Not CONNECT. */
 139                     /* Send back a SOCKS 4 error before closing. */
 140                     char data[8];
 141                     memset(data, 0, sizeof(data));
 142                     data[1] = 91;      /* generic `request rejected' */
 143                     sk_write(pr->s, data, 8);
 144                     pfd_close(pr->s);
 145                     return 1;
 146                 }
 147                 if (pr->sockslen <= 8)
 148                     continue;      /* haven't started user/hostname */
 149                 if (pr->socksbuf[pr->sockslen-1] != 0)
 150                     continue;          /* haven't _finished_ user/hostname */
 151                 /*
 152                  * Now we have a full SOCKS 4 request. Check it to
 153                  * see if it's a SOCKS 4A request.
 154                  */
 155                 if (pr->socksbuf[4] == 0 && pr->socksbuf[5] == 0 &&
 156                     pr->socksbuf[6] == 0 && pr->socksbuf[7] != 0) {
 157                     /*
 158                      * It's SOCKS 4A. So if we haven't yet
 159                      * collected the host name, we should continue
 160                      * waiting for data in order to do so; if we
 161                      * have, we can go ahead.
 162                      */
 163                     int len;
 164                     if (pr->dynamic == 0x4000) {
 165                         pr->dynamic = 0x4001;
 166                         pr->sockslen = 8; /* reset buffer to overwrite name */
 167                         continue;
 168                     }
 169                     pr->socksbuf[0] = 0;   /* reply version code */
 170                     pr->socksbuf[1] = 90;   /* request granted */
 171                     sk_write(pr->s, pr->socksbuf, 8);
 172                     len = pr->sockslen - 8;
 173                     pr->port = GET_16BIT_MSB_FIRST(pr->socksbuf+2);
 174                     pr->hostname = snewn(len+1, char);
 175                     pr->hostname[len] = '\0';
 176                     memcpy(pr->hostname, pr->socksbuf + 8, len);
 177                     goto connect;
 178                 } else {
 179                     /*
 180                      * It's SOCKS 4, which means we should format
 181                      * the IP address into the hostname string and
 182                      * then just go.
 183                      */
 184                     pr->socksbuf[0] = 0;   /* reply version code */
 185                     pr->socksbuf[1] = 90;   /* request granted */
 186                     sk_write(pr->s, pr->socksbuf, 8);
 187                     pr->port = GET_16BIT_MSB_FIRST(pr->socksbuf+2);
 188                     pr->hostname = dupprintf("%d.%d.%d.%d",
 189                                              (unsigned char)pr->socksbuf[4],
 190                                              (unsigned char)pr->socksbuf[5],
 191                                              (unsigned char)pr->socksbuf[6],
 192                                              (unsigned char)pr->socksbuf[7]);
 193                     goto connect;
 194                 }
 195             }
 196
 197             if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 5) &&
 198                 pr->socksbuf[0] == 5) {
 199                 /*
 200                  * SOCKS 5.
 201                  */
 202                 if (pr->dynamic == 1)
 203                     pr->dynamic = 0x5000;
 204
 205                 if (pr->dynamic == 0x5000) {
 206                     int i, method;
 207                     char data[2];
 208                     /*
 209                      * We're receiving a set of method identifiers.
 210                      */
 211                     if (pr->sockslen < 2)
 212                         continue;      /* no method count yet */
 213                     if (pr->sockslen < 2 + (unsigned char)pr->socksbuf[1])
 214                         continue;      /* no methods yet */
 215                     method = 0xFF;     /* invalid */
 216                     for (i = 0; i < (unsigned char)pr->socksbuf[1]; i++)
 217                         if (pr->socksbuf[2+i] == 0) {
 218                             method = 0;/* no auth */
 219                             break;
 220                         }
 221                     data[0] = 5;
 222                     data[1] = method;
 223                     sk_write(pr->s, data, 2);
 224                     pr->dynamic = 0x5001;
 225                     pr->sockslen = 0;      /* re-empty the buffer */
 226                     continue;
 227                 }
 228
 229                 if (pr->dynamic == 0x5001) {
 230                     /*
 231                      * We're receiving a SOCKS request.
 232                      */
 233                     unsigned char reply[10]; /* SOCKS5 atyp=1 reply */
 234                     int atype, alen = 0;
 235
 236                     /*
 237                      * Pre-fill reply packet.
 238                      * In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0
 239                      * (atyp=1) in the reply; if we succeed, we don't know
 240                      * the right answers, and if we fail, they should be
 241                      * ignored.
 242                      */
 243                     memset(reply, 0, lenof(reply));
 244                     reply[0] = 5; /* VER */
 245                     reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */
 246
 247                     if (pr->sockslen < 6) continue;
 248                     atype = (unsigned char)pr->socksbuf[3];
 249                     if (atype == 1)    /* IPv4 address */
 250                         alen = 4;
 251                     if (atype == 4)    /* IPv6 address */
 252                         alen = 16;
 253                     if (atype == 3)    /* domain name has leading length */
 254                         alen = 1 + (unsigned char)pr->socksbuf[4];
 255                     if (pr->sockslen < 6 + alen) continue;
 256                     if (pr->socksbuf[1] != 1 || pr->socksbuf[2] != 0) {
 257                         /* Not CONNECT or reserved field nonzero - error */
 258                         reply[1] = 1;   /* generic failure */
 259                         sk_write(pr->s, (char *) reply, lenof(reply));
 260                         pfd_close(pr->s);
 261                         return 1;
 262                     }
 263                     /*
 264                      * Now we have a viable connect request. Switch
 265                      * on atype.
 266                      */
 267                     pr->port = GET_16BIT_MSB_FIRST(pr->socksbuf+4+alen);
 268                     if (atype == 1) {
 269                         /* REP=0 (success) already */
 270                         sk_write(pr->s, (char *) reply, lenof(reply));
 271                         pr->hostname = dupprintf("%d.%d.%d.%d",
 272                                                  (unsigned char)pr->socksbuf[4],
 273                                                  (unsigned char)pr->socksbuf[5],
 274                                                  (unsigned char)pr->socksbuf[6],
 275                                                  (unsigned char)pr->socksbuf[7]);
 276                         goto connect;
 277                     } else if (atype == 3) {
 278                         /* REP=0 (success) already */
 279                         sk_write(pr->s, (char *) reply, lenof(reply));
 280                         pr->hostname = snewn(alen, char);
 281                         pr->hostname[alen-1] = '\0';
 282                         memcpy(pr->hostname, pr->socksbuf + 5, alen-1);
 283                         goto connect;
 284                     } else {
 285                         /*
 286                          * Unknown address type. (FIXME: support IPv6!)
 287                          */
 288                         reply[1] = 8;   /* atype not supported */
 289                         sk_write(pr->s, (char *) reply, lenof(reply));
 290                         pfd_close(pr->s);
 291                         return 1;
 292                     }
 293                 }
 294             }
 295
 296             /*
 297              * If we get here without either having done `continue'
 298              * or `goto connect', it must be because there is no
 299              * sensible interpretation of what's in our buffer. So
 300              * close the connection rudely.
 301              */
 302             pfd_close(pr->s);
 303             return 1;
 304         }
 305         return 1;
 306
 307         /*
 308          * We come here when we're ready to make an actual
 309          * connection.
 310          */
 311         connect:
 312         sfree(pr->socksbuf);
 313         pr->socksbuf = NULL;
 314
 315         /*
 316          * Freeze the socket until the SSH server confirms the
 317          * connection.
 318          */
 319         sk_set_frozen(pr->s, 1);
 320
 321         pr->c = new_sock_channel(pr->backhandle, pr->s);
 322         if (pr->c == NULL) {
 323             pfd_close(pr->s);
 324             return 1;
 325         } else {
 326             /* asks to forward to the specified host/port for this */
 327             ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
 328         }
 329         pr->dynamic = 0;
 330
 331         /*
 332          * If there's any data remaining in our current buffer,
 333          * save it to be sent on pfd_confirm().
 334          */
 335         if (len > 0) {
 336             pr->buffer = snewn(len, char);
 337             memcpy(pr->buffer, data, len);
 338             pr->buflen = len;
 339         }
 340     }
 341     if (pr->ready) {
 342         if (sshfwd_write(pr->c, data, len) > 0) {
 343             pr->throttled = 1;
 344             sk_set_frozen(pr->s, 1);
 345         }
 346     }
 347     return 1;
 348 }
 349
 350 static void pfd_sent(Plug plug, int bufsize)
 351 {
 352     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
 353
 354     if (pr->c)
 355         sshfwd_unthrottle(pr->c, bufsize);
 356 }
 357
 358 /*
 359  * Called when receiving a PORT OPEN from the server
 360  */
 361 const char *pfd_newconnect(Socket *s, char *hostname, int port,
 362                            void *c, Conf *conf, int addressfamily)
 363 {
 364     static const struct plug_function_table fn_table = {
 365         pfd_log,
 366         pfd_closing,
 367         pfd_receive,
 368         pfd_sent,
 369         NULL
 370     };
 371
 372     SockAddr addr;
 373     const char *err;
 374     char *dummy_realhost;
 375     struct PFwdPrivate *pr;
 376
 377     /*
 378      * Try to find host.
 379      */
 380     addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily);
 381     if ((err = sk_addr_error(addr)) != NULL) {
 382         sk_addr_free(addr);
 383         sfree(dummy_realhost);
 384         return err;
 385     }
 386
 387     /*
 388      * Open socket.
 389      */
 390     pr = new_portfwd_private();
 391     pr->fn = &fn_table;
 392     pr->throttled = pr->throttle_override = 0;
 393     pr->ready = 1;
 394     pr->c = c;
 395     pr->backhandle = NULL;             /* we shouldn't need this */
 396     pr->dynamic = 0;
 397
 398     pr->s = *s = new_connection(addr, dummy_realhost, port,
 399                                 0, 1, 0, 0, (Plug) pr, conf);
 400     sfree(dummy_realhost);
 401     if ((err = sk_socket_error(*s)) != NULL) {
 402         free_portfwd_private(pr);
 403         return err;
 404     }
 405
 406     sk_set_private_ptr(*s, pr);
 407     return NULL;
 408 }
 409
 410 /*
 411  called when someone connects to the local port
 412  */
 413
 414 static int pfd_accepting(Plug p, OSSocket sock)
 415 {
 416     static const struct plug_function_table fn_table = {
 417         pfd_log,
 418         pfd_closing,
 419         pfd_receive,
 420         pfd_sent,
 421         NULL
 422     };
 423     struct PFwdPrivate *pr, *org;
 424     Socket s;
 425     const char *err;
 426
 427     org = (struct PFwdPrivate *)p;
 428     pr = new_portfwd_private();
 429     pr->fn = &fn_table;
 430
 431     pr->c = NULL;
 432     pr->backhandle = org->backhandle;
 433
 434     pr->s = s = sk_register(sock, (Plug) pr);
 435     if ((err = sk_socket_error(s)) != NULL) {
 436         free_portfwd_private(pr);
 437         return err != NULL;
 438     }
 439
 440     sk_set_private_ptr(s, pr);
 441
 442     pr->throttled = pr->throttle_override = 0;
 443     pr->ready = 0;
 444
 445     if (org->dynamic) {
 446         pr->dynamic = 1;
 447         pr->port = 0;                  /* "hostname" buffer is so far empty */
 448         sk_set_frozen(s, 0);           /* we want to receive SOCKS _now_! */
 449     } else {
 450         pr->dynamic = 0;
 451         pr->hostname = dupstr(org->hostname);
 452         pr->port = org->port;
 453         pr->c = new_sock_channel(org->backhandle, s);
 454
 455         if (pr->c == NULL) {
 456             free_portfwd_private(pr);
 457             return 1;
 458         } else {
 459             /* asks to forward to the specified host/port for this */
 460             ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
 461         }
 462     }
 463
 464     return 0;
 465 }
 466
 467
 468 /* Add a new forwarding from port -> desthost:destport
 469  sets up a listener on the local machine on (srcaddr:)port
 470  */
 471 const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
 472                            int port, void *backhandle, Conf *conf,
 473                            void **sockdata, int address_family)
 474 {
 475     static const struct plug_function_table fn_table = {
 476         pfd_log,
 477         pfd_closing,
 478         pfd_receive,                   /* should not happen... */
 479         pfd_sent,                      /* also should not happen */
 480         pfd_accepting
 481     };
 482
 483     const char *err;
 484     struct PFwdPrivate *pr;
 485     Socket s;
 486
 487     /*
 488      * Open socket.
 489      */
 490     pr = new_portfwd_private();
 491     pr->fn = &fn_table;
 492     pr->c = NULL;
 493     if (desthost) {
 494         pr->hostname = dupstr(desthost);
 495         pr->port = destport;
 496         pr->dynamic = 0;
 497     } else
 498         pr->dynamic = 1;
 499     pr->throttled = pr->throttle_override = 0;
 500     pr->ready = 0;
 501     pr->backhandle = backhandle;
 502
 503     pr->s = s = new_listener(srcaddr, port, (Plug) pr,
 504                              !conf_get_int(conf, CONF_lport_acceptall),
 505                              conf, address_family);
 506     if ((err = sk_socket_error(s)) != NULL) {
 507         free_portfwd_private(pr);
 508         return err;
 509     }
 510
 511     sk_set_private_ptr(s, pr);
 512
 513     *sockdata = (void *)s;
 514
 515     return NULL;
 516 }
 517
 518 void pfd_close(Socket s)
 519 {
 520     struct PFwdPrivate *pr;
 521
 522     if (!s)
 523         return;
 524
 525     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 526
 527     free_portfwd_private(pr);
 528
 529     sk_close(s);
 530 }
 531
 532 /*
 533  * Terminate a listener.
 534  */
 535 void pfd_terminate(void *sv)
 536 {
 537     pfd_close((Socket)sv);
 538 }
 539
 540 void pfd_unthrottle(Socket s)
 541 {
 542     struct PFwdPrivate *pr;
 543     if (!s)
 544         return;
 545     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 546
 547     pr->throttled = 0;
 548     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 549 }
 550
 551 void pfd_override_throttle(Socket s, int enable)
 552 {
 553     struct PFwdPrivate *pr;
 554     if (!s)
 555         return;
 556     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 557
 558     pr->throttle_override = enable;
 559     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 560 }
 561
 562 /*
 563  * Called to send data down the raw connection.
 564  */
 565 int pfd_send(Socket s, char *data, int len)
 566 {
 567     if (s == NULL)
 568         return 0;
 569     return sk_write(s, data, len);
 570 }
 571
 572 void pfd_send_eof(Socket s)
 573 {
 574     sk_write_eof(s);
 575 }
 576
 577 void pfd_confirm(Socket s)
 578 {
 579     struct PFwdPrivate *pr;
 580
 581     if (s == NULL)
 582         return;
 583
 584     pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 585     pr->ready = 1;
 586     sk_set_frozen(s, 0);
 587     sk_write(s, NULL, 0);
 588     if (pr->buffer) {
 589         sshfwd_write(pr->c, pr->buffer, pr->buflen);
 590         sfree(pr->buffer);
 591         pr->buffer = NULL;
 592     }
 593 }