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

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <winsock.h>
   4
   5 #include "putty.h"
   6
   7 #ifndef FALSE
   8 #define FALSE 0
   9 #endif
  10 #ifndef TRUE
  11 #define TRUE 1
  12 #endif
  13
  14 #include "ssh.h"
  15
  16 #define SSH_MSG_DISCONNECT 1
  17 #define SSH_SMSG_PUBLIC_KEY 2
  18 #define SSH_CMSG_SESSION_KEY 3
  19 #define SSH_CMSG_USER 4
  20 #define SSH_CMSG_AUTH_PASSWORD 9
  21 #define SSH_CMSG_REQUEST_PTY 10
  22 #define SSH_CMSG_EXEC_SHELL 12
  23 #define SSH_CMSG_STDIN_DATA 16
  24 #define SSH_SMSG_STDOUT_DATA 17
  25 #define SSH_SMSG_STDERR_DATA 18
  26 #define SSH_SMSG_SUCCESS 14
  27 #define SSH_SMSG_FAILURE 15
  28 #define SSH_SMSG_EXITSTATUS 20
  29 #define SSH_MSG_IGNORE 32
  30 #define SSH_CMSG_EXIT_CONFIRMATION 33
  31 #define SSH_MSG_DEBUG 36
  32 #define SSH_CMSG_AUTH_TIS 39
  33 #define SSH_SMSG_AUTH_TIS_CHALLENGE 40
  34 #define SSH_CMSG_AUTH_TIS_RESPONSE 41
  35
  36 #define SSH_AUTH_TIS              5
  37
  38 /* Coroutine mechanics for the sillier bits of the code */
  39 #define crBegin1        static int crLine = 0;
  40 #define crBegin2        switch(crLine) { case 0:;
  41 #define crBegin         crBegin1; crBegin2;
  42 #define crFinish(z)     } crLine = 0; return (z)
  43 #define crFinishV       } crLine = 0; return
  44 #define crReturn(z)     \
  45         do {\
  46             crLine=__LINE__; return (z); case __LINE__:;\
  47         } while (0)
  48 #define crReturnV       \
  49         do {\
  50             crLine=__LINE__; return; case __LINE__:;\
  51         } while (0)
  52 #define crStop(z)       do{ crLine = 0; return (z); }while(0)
  53 #define crStopV         do{ crLine = 0; return; }while(0)
  54
  55 #ifndef FALSE
  56 #define FALSE 0
  57 #endif
  58 #ifndef TRUE
  59 #define TRUE 1
  60 #endif
  61
  62 static SOCKET s = INVALID_SOCKET;
  63
  64 static unsigned char session_key[32];
  65 static struct ssh_cipher *cipher = NULL;
  66
  67 static char *savedhost;
  68
  69 static enum {
  70     SSH_STATE_BEFORE_SIZE,
  71     SSH_STATE_INTERMED,
  72     SSH_STATE_SESSION,
  73     SSH_STATE_CLOSED
  74 } ssh_state = SSH_STATE_BEFORE_SIZE;
  75
  76 static int size_needed = FALSE;
  77
  78 static void s_write (char *buf, int len) {
  79     while (len > 0) {
  80         int i = send (s, buf, len, 0);
  81         if (i > 0)
  82             len -= i, buf += i;
  83     }
  84 }
  85
  86 static int s_read (char *buf, int len) {
  87     int ret = 0;
  88     while (len > 0) {
  89         int i = recv (s, buf, len, 0);
  90         if (i > 0)
  91             len -= i, buf += i, ret += i;
  92         else
  93             return i;
  94     }
  95     return ret;
  96 }
  97
  98 static void c_write (char *buf, int len) {
  99     while (len--) {
 100         int new_head = (inbuf_head + 1) & INBUF_MASK;
 101         if (new_head != inbuf_reap) {
 102             inbuf[inbuf_head] = *buf++;
 103             inbuf_head = new_head;
 104         } else {
 105             term_out();
 106             if( inbuf_head == inbuf_reap ) len++; else break;
 107         }
 108     }
 109 }
 110
 111 struct Packet {
 112     long length;
 113     int type;
 114     unsigned long crc;
 115     unsigned char *data;
 116     unsigned char *body;
 117     long maxlen;
 118 };
 119
 120 static struct Packet pktin = { 0, 0, 0, NULL, 0 };
 121 static struct Packet pktout = { 0, 0, 0, NULL, 0 };
 122
 123 static void ssh_protocol(unsigned char *in, int inlen, int ispkt);
 124 static void ssh_size(void);
 125
 126 static void ssh_gotdata(unsigned char *data, int datalen) {
 127     static long len, biglen, to_read;
 128     static unsigned char *p;
 129     static int i, pad;
 130     static unsigned long realcrc, gotcrc;
 131
 132     crBegin;
 133     while (1) {
 134         for (i = len = 0; i < 4; i++) {
 135             while (datalen == 0)
 136                 crReturnV;
 137             len = (len << 8) + *data;
 138             data++, datalen--;
 139         }
 140
 141 #ifdef FWHACK
 142         if (len == 0x52656d6f) {       /* "Remo"te server has closed ... */
 143             len = 0x300;               /* big enough to carry to end */
 144         }
 145 #endif
 146
 147         pad = 8 - (len%8);
 148
 149         biglen = len + pad;
 150
 151         len -= 5;                      /* type and CRC */
 152
 153         pktin.length = len;
 154         if (pktin.maxlen < biglen) {
 155             pktin.maxlen = biglen;
 156 #ifdef MSCRYPTOAPI
 157             /* Allocate enough buffer space for extra block
 158              * for MS CryptEncrypt() */
 159             pktin.data = (pktin.data == NULL ? malloc(biglen+8) :
 160                           realloc(pktin.data, biglen+8));
 161 #else
 162             pktin.data = (pktin.data == NULL ? malloc(biglen) :
 163                           realloc(pktin.data, biglen));
 164 #endif
 165             if (!pktin.data)
 166                 fatalbox("Out of memory");
 167         }
 168
 169         p = pktin.data, to_read = biglen;
 170         while (to_read > 0) {
 171             static int chunk;
 172             chunk = to_read;
 173             while (datalen == 0)
 174                 crReturnV;
 175             if (chunk > datalen)
 176                 chunk = datalen;
 177             memcpy(p, data, chunk);
 178             data += chunk;
 179             datalen -= chunk;
 180             p += chunk;
 181             to_read -= chunk;
 182         }
 183
 184         if (cipher)
 185             cipher->decrypt(pktin.data, biglen);
 186
 187         pktin.type = pktin.data[pad];
 188         pktin.body = pktin.data+pad+1;
 189
 190         realcrc = crc32(pktin.data, biglen-4);
 191         gotcrc = (pktin.data[biglen-4] << 24);
 192         gotcrc |= (pktin.data[biglen-3] << 16);
 193         gotcrc |= (pktin.data[biglen-2] <<  8);
 194         gotcrc |= (pktin.data[biglen-1] <<  0);
 195         if (gotcrc != realcrc) {
 196             fatalbox("Incorrect CRC received on packet");
 197         }
 198
 199         if (pktin.type == SSH_MSG_DEBUG) {
 200             /* FIXME: log it */
 201         } else if (pktin.type == SSH_MSG_IGNORE) {
 202             /* do nothing */;
 203         } else
 204             ssh_protocol(NULL, 0, 1);
 205     }
 206     crFinishV;
 207 }
 208
 209 static void s_wrpkt_start(int type, int len) {
 210     int pad, biglen;
 211
 212     len += 5;                          /* type and CRC */
 213     pad = 8 - (len%8);
 214     biglen = len + pad;
 215
 216     pktout.length = len-5;
 217     if (pktout.maxlen < biglen) {
 218         pktout.maxlen = biglen;
 219 #ifdef MSCRYPTOAPI
 220         /* Allocate enough buffer space for extra block
 221          * for MS CryptEncrypt() */
 222         pktout.data = (pktout.data == NULL ? malloc(biglen+8) :
 223                        realloc(pktout.data, biglen+8));
 224 #else
 225         pktout.data = (pktout.data == NULL ? malloc(biglen+4) :
 226                        realloc(pktout.data, biglen+4));
 227 #endif
 228         if (!pktout.data)
 229             fatalbox("Out of memory");
 230     }
 231
 232     pktout.type = type;
 233     pktout.body = pktout.data+4+pad+1;
 234 }
 235
 236 static void s_wrpkt(void) {
 237     int pad, len, biglen, i;
 238     unsigned long crc;
 239
 240     len = pktout.length + 5;           /* type and CRC */
 241     pad = 8 - (len%8);
 242     biglen = len + pad;
 243
 244     pktout.body[-1] = pktout.type;
 245     for (i=0; i<pad; i++)
 246         pktout.data[i+4] = random_byte();
 247     crc = crc32(pktout.data+4, biglen-4);
 248
 249     pktout.data[biglen+0] = (unsigned char) ((crc >> 24) & 0xFF);
 250     pktout.data[biglen+1] = (unsigned char) ((crc >> 16) & 0xFF);
 251     pktout.data[biglen+2] = (unsigned char) ((crc >> 8) & 0xFF);
 252     pktout.data[biglen+3] = (unsigned char) (crc & 0xFF);
 253
 254     pktout.data[0] = (len >> 24) & 0xFF;
 255     pktout.data[1] = (len >> 16) & 0xFF;
 256     pktout.data[2] = (len >> 8) & 0xFF;
 257     pktout.data[3] = len & 0xFF;
 258
 259     if (cipher)
 260         cipher->encrypt(pktout.data+4, biglen);
 261
 262     s_write(pktout.data, biglen+4);
 263 }
 264
 265 static int ssh_versioncmp(char *a, char *b) {
 266     char *ae, *be;
 267     unsigned long av, bv;
 268
 269     av = strtoul(a, &ae, 10);
 270     bv = strtoul(b, &be, 10);
 271     if (av != bv) return (av < bv ? -1 : +1);
 272     if (*ae == '.') ae++;
 273     if (*be == '.') be++;
 274     av = strtoul(ae, &ae, 10);
 275     bv = strtoul(be, &be, 10);
 276     if (av != bv) return (av < bv ? -1 : +1);
 277     return 0;
 278 }
 279
 280 static int do_ssh_init(void) {
 281     char c, *vsp;
 282     char version[10];
 283     char vstring[80];
 284     char vlog[sizeof(vstring)+20];
 285     int i;
 286
 287 #ifdef FWHACK
 288     i = 0;
 289     while (s_read(&c, 1) == 1) {
 290         if (c == 'S' && i < 2) i++;
 291         else if (c == 'S' && i == 2) i = 2;
 292         else if (c == 'H' && i == 2) break;
 293         else i = 0;
 294     }
 295 #else
 296     if (s_read(&c,1) != 1 || c != 'S') return 0;
 297     if (s_read(&c,1) != 1 || c != 'S') return 0;
 298     if (s_read(&c,1) != 1 || c != 'H') return 0;
 299 #endif
 300     strcpy(vstring, "SSH-");
 301     vsp = vstring+4;
 302     if (s_read(&c,1) != 1 || c != '-') return 0;
 303     i = 0;
 304     while (1) {
 305         if (s_read(&c,1) != 1)
 306             return 0;
 307         if (vsp < vstring+sizeof(vstring)-1)
 308             *vsp++ = c;
 309         if (i >= 0) {
 310             if (c == '-') {
 311                 version[i] = '\0';
 312                 i = -1;
 313             } else if (i < sizeof(version)-1)
 314                 version[i++] = c;
 315         }
 316         else if (c == '\n')
 317             break;
 318     }
 319
 320     *vsp = 0;
 321     sprintf(vlog, "Server version: %s", vstring);
 322     vlog[strcspn(vlog, "\r\n")] = '\0';
 323     logevent(vlog);
 324
 325     sprintf(vstring, "SSH-%s-PuTTY\n",
 326             (ssh_versioncmp(version, "1.5") <= 0 ? version : "1.5"));
 327     sprintf(vlog, "We claim version: %s", vstring);
 328     vlog[strcspn(vlog, "\r\n")] = '\0';
 329     logevent(vlog);
 330     s_write(vstring, strlen(vstring));
 331     return 1;
 332 }
 333
 334 static void ssh_protocol(unsigned char *in, int inlen, int ispkt) {
 335     int i, j, len;
 336     unsigned char session_id[16];
 337     unsigned char *rsabuf, *keystr1, *keystr2;
 338     unsigned char cookie[8];
 339     struct RSAKey servkey, hostkey;
 340     struct MD5Context md5c;
 341     static unsigned long supported_ciphers_mask, supported_auths_mask;
 342     int cipher_type;
 343
 344     extern struct ssh_cipher ssh_3des;
 345     extern struct ssh_cipher ssh_des;
 346     extern struct ssh_cipher ssh_blowfish;
 347
 348     crBegin;
 349
 350     random_init();
 351
 352     while (!ispkt)
 353         crReturnV;
 354
 355     if (pktin.type != SSH_SMSG_PUBLIC_KEY)
 356         fatalbox("Public key packet not received");
 357
 358     logevent("Received public keys");
 359
 360     memcpy(cookie, pktin.body, 8);
 361
 362     i = makekey(pktin.body+8, &servkey, &keystr1);
 363
 364     j = makekey(pktin.body+8+i, &hostkey, &keystr2);
 365
 366     /*
 367      * Hash the host key and print the hash in the log box. Just as
 368      * a last resort in case the registry's host key checking is
 369      * compromised, we'll allow the user some ability to verify
 370      * host keys by eye.
 371      */
 372     MD5Init(&md5c);
 373     MD5Update(&md5c, keystr2, hostkey.bytes);
 374     MD5Final(session_id, &md5c);
 375     {
 376         char logmsg[80];
 377         int i;
 378         logevent("Host key MD5 is:");
 379         strcpy(logmsg, "      ");
 380         for (i = 0; i < 16; i++)
 381             sprintf(logmsg+strlen(logmsg), "%02x", session_id[i]);
 382         logevent(logmsg);
 383     }
 384
 385     supported_ciphers_mask = ((pktin.body[12+i+j] << 24) |
 386                               (pktin.body[13+i+j] << 16) |
 387                               (pktin.body[14+i+j] << 8) |
 388                               (pktin.body[15+i+j]));
 389
 390     supported_auths_mask = ((pktin.body[16+i+j] << 24) |
 391                             (pktin.body[17+i+j] << 16) |
 392                             (pktin.body[18+i+j] << 8) |
 393                             (pktin.body[19+i+j]));
 394
 395     MD5Init(&md5c);
 396
 397     MD5Update(&md5c, keystr2, hostkey.bytes);
 398     MD5Update(&md5c, keystr1, servkey.bytes);
 399     MD5Update(&md5c, pktin.body, 8);
 400
 401     MD5Final(session_id, &md5c);
 402
 403     for (i=0; i<32; i++)
 404         session_key[i] = random_byte();
 405
 406     len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 407
 408     rsabuf = malloc(len);
 409     if (!rsabuf)
 410         fatalbox("Out of memory");
 411
 412     /*
 413      * Verify the host key.
 414      */
 415     {
 416         /*
 417          * First format the key into a string.
 418          */
 419         int len = rsastr_len(&hostkey);
 420         char *keystr = malloc(len);
 421         if (!keystr)
 422             fatalbox("Out of memory");
 423         rsastr_fmt(keystr, &hostkey);
 424         verify_ssh_host_key(savedhost, keystr);
 425         free(keystr);
 426     }
 427
 428     for (i=0; i<32; i++) {
 429         rsabuf[i] = session_key[i];
 430         if (i < 16)
 431             rsabuf[i] ^= session_id[i];
 432     }
 433
 434     if (hostkey.bytes > servkey.bytes) {
 435         rsaencrypt(rsabuf, 32, &servkey);
 436         rsaencrypt(rsabuf, servkey.bytes, &hostkey);
 437     } else {
 438         rsaencrypt(rsabuf, 32, &hostkey);
 439         rsaencrypt(rsabuf, hostkey.bytes, &servkey);
 440     }
 441
 442     logevent("Encrypted session key");
 443
 444     cipher_type = cfg.cipher == CIPHER_BLOWFISH ? SSH_CIPHER_BLOWFISH :
 445                   cfg.cipher == CIPHER_DES ? SSH_CIPHER_DES :
 446                   SSH_CIPHER_3DES;
 447     if ((supported_ciphers_mask & (1 << cipher_type)) == 0) {
 448         c_write("Selected cipher not supported, falling back to 3DES\r\n", 53);
 449         cipher_type = SSH_CIPHER_3DES;
 450     }
 451     switch (cipher_type) {
 452       case SSH_CIPHER_3DES: logevent("Using 3DES encryption"); break;
 453       case SSH_CIPHER_DES: logevent("Using single-DES encryption"); break;
 454       case SSH_CIPHER_BLOWFISH: logevent("Using Blowfish encryption"); break;
 455     }
 456
 457     s_wrpkt_start(SSH_CMSG_SESSION_KEY, len+15);
 458     pktout.body[0] = cipher_type;
 459     memcpy(pktout.body+1, cookie, 8);
 460     pktout.body[9] = (len*8) >> 8;
 461     pktout.body[10] = (len*8) & 0xFF;
 462     memcpy(pktout.body+11, rsabuf, len);
 463     pktout.body[len+11] = pktout.body[len+12] = 0;   /* protocol flags */
 464     pktout.body[len+13] = pktout.body[len+14] = 0;
 465     s_wrpkt();
 466     logevent("Trying to enable encryption...");
 467
 468     free(rsabuf);
 469
 470     cipher = cipher_type == SSH_CIPHER_BLOWFISH ? &ssh_blowfish :
 471              cipher_type == SSH_CIPHER_DES ? &ssh_des :
 472              &ssh_3des;
 473     cipher->sesskey(session_key);
 474
 475     do { crReturnV; } while (!ispkt);
 476
 477     if (pktin.type != SSH_SMSG_SUCCESS)
 478         fatalbox("Encryption not successfully enabled");
 479
 480     logevent("Successfully started encryption");
 481
 482     fflush(stdout);
 483     {
 484         static char username[100];
 485         static int pos = 0;
 486         static char c;
 487         if (!*cfg.username) {
 488             c_write("login as: ", 10);
 489             while (pos >= 0) {
 490                 do { crReturnV; } while (ispkt);
 491                 while (inlen--) switch (c = *in++) {
 492                   case 10: case 13:
 493                     username[pos] = 0;
 494                     pos = -1;
 495                     break;
 496                   case 8: case 127:
 497                     if (pos > 0) {
 498                         c_write("\b \b", 3);
 499                         pos--;
 500                     }
 501                     break;
 502                   case 21: case 27:
 503                     while (pos > 0) {
 504                         c_write("\b \b", 3);
 505                         pos--;
 506                     }
 507                     break;
 508                   case 3: case 4:
 509                     random_save_seed();
 510                     exit(0);
 511                     break;
 512                   default:
 513                     if (((c >= ' ' && c <= '~') ||
 514                          ((unsigned char)c >= 160)) && pos < 40) {
 515                         username[pos++] = c;
 516                         c_write(&c, 1);
 517                     }
 518                     break;
 519                 }
 520             }
 521             c_write("\r\n", 2);
 522             username[strcspn(username, "\n\r")] = '\0';
 523         } else {
 524             char stuff[200];
 525             strncpy(username, cfg.username, 99);
 526             username[99] = '\0';
 527             sprintf(stuff, "Sent username \"%s\".\r\n", username);
 528             c_write(stuff, strlen(stuff));
 529         }
 530         s_wrpkt_start(SSH_CMSG_USER, 4+strlen(username));
 531         {
 532             char userlog[20+sizeof(username)];
 533             sprintf(userlog, "Sent username \"%s\"", username);
 534             logevent(userlog);
 535         }
 536         pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 537         pktout.body[3] = strlen(username);
 538         memcpy(pktout.body+4, username, strlen(username));
 539         s_wrpkt();
 540     }
 541
 542     do { crReturnV; } while (!ispkt);
 543
 544     while (pktin.type == SSH_SMSG_FAILURE) {
 545         static char password[100];
 546         static int pos;
 547         static char c;
 548         static int pwpkt_type;
 549
 550         /*
 551          * Show password prompt, having first obtained it via a TIS
 552          * exchange if we're doing TIS authentication.
 553          */
 554         pwpkt_type = SSH_CMSG_AUTH_PASSWORD;
 555         if (pktin.type == SSH_SMSG_FAILURE &&
 556             cfg.try_tis_auth &&
 557             (supported_auths_mask & (1<<SSH_AUTH_TIS))) {
 558             pwpkt_type = SSH_CMSG_AUTH_TIS_RESPONSE;
 559             logevent("Requested TIS authentication");
 560             s_wrpkt_start(SSH_CMSG_AUTH_TIS, 0);
 561             s_wrpkt();
 562             do { crReturnV; } while (!ispkt);
 563             if (pktin.type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
 564                 logevent("TIS authentication declined");
 565                 c_write("TIS authentication refused.\r\n", 29);
 566             } else {
 567                 int challengelen = ((pktin.body[0] << 24) |
 568                                     (pktin.body[1] << 16) |
 569                                     (pktin.body[2] << 8) |
 570                                     (pktin.body[3]));
 571                 logevent("Received TIS challenge");
 572                 c_write(pktin.body+4, challengelen);
 573             }
 574         }
 575         if (pwpkt_type == SSH_CMSG_AUTH_PASSWORD)
 576             c_write("password: ", 10);
 577
 578         pos = 0;
 579         while (pos >= 0) {
 580             do { crReturnV; } while (ispkt);
 581             while (inlen--) switch (c = *in++) {
 582               case 10: case 13:
 583                 password[pos] = 0;
 584                 pos = -1;
 585                 break;
 586               case 8: case 127:
 587                 if (pos > 0)
 588                     pos--;
 589                 break;
 590               case 21: case 27:
 591                 pos = 0;
 592                 break;
 593               case 3: case 4:
 594                 random_save_seed();
 595                 exit(0);
 596                 break;
 597               default:
 598                 if (((c >= ' ' && c <= '~') ||
 599                      ((unsigned char)c >= 160)) && pos < 40)
 600                     password[pos++] = c;
 601                 break;
 602             }
 603         }
 604         c_write("\r\n", 2);
 605         s_wrpkt_start(pwpkt_type, 4+strlen(password));
 606         pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 607         pktout.body[3] = strlen(password);
 608         memcpy(pktout.body+4, password, strlen(password));
 609         s_wrpkt();
 610         logevent("Sent password");
 611         memset(password, 0, strlen(password));
 612         do { crReturnV; } while (!ispkt);
 613         if (pktin.type == 15) {
 614             c_write("Access denied\r\n", 15);
 615             logevent("Authentication refused");
 616         } else if (pktin.type != 14) {
 617             fatalbox("Strange packet received, type %d", pktin.type);
 618         }
 619     }
 620
 621     logevent("Authentication successful");
 622
 623     if (!cfg.nopty) {
 624         i = strlen(cfg.termtype);
 625         s_wrpkt_start(SSH_CMSG_REQUEST_PTY, i+5*4+1);
 626         pktout.body[0] = (i >> 24) & 0xFF;
 627         pktout.body[1] = (i >> 16) & 0xFF;
 628         pktout.body[2] = (i >> 8) & 0xFF;
 629         pktout.body[3] = i & 0xFF;
 630         memcpy(pktout.body+4, cfg.termtype, i);
 631         i += 4;
 632         pktout.body[i++] = (rows >> 24) & 0xFF;
 633         pktout.body[i++] = (rows >> 16) & 0xFF;
 634         pktout.body[i++] = (rows >> 8) & 0xFF;
 635         pktout.body[i++] = rows & 0xFF;
 636         pktout.body[i++] = (cols >> 24) & 0xFF;
 637         pktout.body[i++] = (cols >> 16) & 0xFF;
 638         pktout.body[i++] = (cols >> 8) & 0xFF;
 639         pktout.body[i++] = cols & 0xFF;
 640         memset(pktout.body+i, 0, 9);       /* 0 pixwidth, 0 pixheight, 0.b endofopt */
 641         s_wrpkt();
 642         ssh_state = SSH_STATE_INTERMED;
 643         do { crReturnV; } while (!ispkt);
 644         if (pktin.type != SSH_SMSG_SUCCESS && pktin.type != SSH_SMSG_FAILURE) {
 645             fatalbox("Protocol confusion");
 646         } else if (pktin.type == SSH_SMSG_FAILURE) {
 647             c_write("Server refused to allocate pty\r\n", 32);
 648         }
 649         logevent("Allocated pty");
 650     }
 651
 652     s_wrpkt_start(SSH_CMSG_EXEC_SHELL, 0);
 653     s_wrpkt();
 654     logevent("Started session");
 655
 656     ssh_state = SSH_STATE_SESSION;
 657     if (size_needed)
 658         ssh_size();
 659
 660     while (1) {
 661         crReturnV;
 662         if (ispkt) {
 663             if (pktin.type == SSH_SMSG_STDOUT_DATA ||
 664                 pktin.type == SSH_SMSG_STDERR_DATA) {
 665                 long len = 0;
 666                 for (i = 0; i < 4; i++)
 667                     len = (len << 8) + pktin.body[i];
 668                 c_write(pktin.body+4, len);
 669             } else if (pktin.type == SSH_MSG_DISCONNECT) {
 670                 ssh_state = SSH_STATE_CLOSED;
 671                 logevent("Received disconnect request");
 672             } else if (pktin.type == SSH_SMSG_SUCCESS) {
 673                 /* may be from EXEC_SHELL on some servers */
 674             } else if (pktin.type == SSH_SMSG_FAILURE) {
 675                 /* may be from EXEC_SHELL on some servers
 676                  * if no pty is available or in other odd cases. Ignore */
 677             } else if (pktin.type == SSH_SMSG_EXITSTATUS) {
 678                 s_wrpkt_start(SSH_CMSG_EXIT_CONFIRMATION, 0);
 679                 s_wrpkt();
 680             } else {
 681                 fatalbox("Strange packet received: type %d", pktin.type);
 682             }
 683         } else {
 684             s_wrpkt_start(SSH_CMSG_STDIN_DATA, 4+inlen);
 685             pktout.body[0] = (inlen >> 24) & 0xFF;
 686             pktout.body[1] = (inlen >> 16) & 0xFF;
 687             pktout.body[2] = (inlen >> 8) & 0xFF;
 688             pktout.body[3] = inlen & 0xFF;
 689             memcpy(pktout.body+4, in, inlen);
 690             s_wrpkt();
 691         }
 692     }
 693
 694     crFinishV;
 695 }
 696
 697 /*
 698  * Called to set up the connection. Will arrange for WM_NETEVENT
 699  * messages to be passed to the specified window, whose window
 700  * procedure should then call telnet_msg().
 701  *
 702  * Returns an error message, or NULL on success.
 703  *
 704  * Also places the canonical host name into `realhost'.
 705  */
 706 static char *ssh_init (HWND hwnd, char *host, int port, char **realhost) {
 707     SOCKADDR_IN addr;
 708     struct hostent *h;
 709     unsigned long a;
 710 #ifdef FWHACK
 711     char *FWhost;
 712     int FWport;
 713 #endif
 714
 715 #ifdef MSCRYPTOAPI
 716     if(crypto_startup() == 0)
 717         return "Microsoft high encryption pack not installed!";
 718 #endif
 719
 720     savedhost = malloc(1+strlen(host));
 721     if (!savedhost)
 722         fatalbox("Out of memory");
 723     strcpy(savedhost, host);
 724
 725 #ifdef FWHACK
 726     FWhost = host;
 727     FWport = port;
 728     host = FWSTR;
 729     port = 23;
 730 #endif
 731
 732     /*
 733      * Try to find host.
 734      */
 735     if ( (a = inet_addr(host)) == (unsigned long) INADDR_NONE) {
 736         if ( (h = gethostbyname(host)) == NULL)
 737             switch (WSAGetLastError()) {
 738               case WSAENETDOWN: return "Network is down";
 739               case WSAHOST_NOT_FOUND: case WSANO_DATA:
 740                 return "Host does not exist";
 741               case WSATRY_AGAIN: return "Host not found";
 742               default: return "gethostbyname: unknown error";
 743             }
 744         memcpy (&a, h->h_addr, sizeof(a));
 745         *realhost = h->h_name;
 746     } else
 747         *realhost = host;
 748 #ifdef FWHACK
 749     *realhost = FWhost;
 750 #endif
 751     a = ntohl(a);
 752
 753     if (port < 0)
 754         port = 22;                     /* default ssh port */
 755
 756     /*
 757      * Open socket.
 758      */
 759     s = socket(AF_INET, SOCK_STREAM, 0);
 760     if (s == INVALID_SOCKET)
 761         switch (WSAGetLastError()) {
 762           case WSAENETDOWN: return "Network is down";
 763           case WSAEAFNOSUPPORT: return "TCP/IP support not present";
 764           default: return "socket(): unknown error";
 765         }
 766
 767     /*
 768      * Bind to local address.
 769      */
 770     addr.sin_family = AF_INET;
 771     addr.sin_addr.s_addr = htonl(INADDR_ANY);
 772     addr.sin_port = htons(0);
 773     if (bind (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 774         switch (WSAGetLastError()) {
 775           case WSAENETDOWN: return "Network is down";
 776           default: return "bind(): unknown error";
 777         }
 778
 779     /*
 780      * Connect to remote address.
 781      */
 782     addr.sin_addr.s_addr = htonl(a);
 783     addr.sin_port = htons((short)port);
 784     if (connect (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 785         switch (WSAGetLastError()) {
 786           case WSAENETDOWN: return "Network is down";
 787           case WSAECONNREFUSED: return "Connection refused";
 788           case WSAENETUNREACH: return "Network is unreachable";
 789           case WSAEHOSTUNREACH: return "No route to host";
 790           default: return "connect(): unknown error";
 791         }
 792
 793 #ifdef FWHACK
 794     send(s, "connect ", 8, 0);
 795     send(s, FWhost, strlen(FWhost), 0);
 796     {
 797         char buf[20];
 798         sprintf(buf, " %d\n", FWport);
 799         send (s, buf, strlen(buf), 0);
 800     }
 801 #endif
 802
 803     if (!do_ssh_init())
 804         return "Protocol initialisation error";
 805
 806     if (WSAAsyncSelect (s, hwnd, WM_NETEVENT, FD_READ | FD_CLOSE) == SOCKET_ERROR)
 807         switch (WSAGetLastError()) {
 808           case WSAENETDOWN: return "Network is down";
 809           default: return "WSAAsyncSelect(): unknown error";
 810         }
 811
 812     return NULL;
 813 }
 814
 815 /*
 816  * Process a WM_NETEVENT message. Will return 0 if the connection
 817  * has closed, or <0 for a socket error.
 818  */
 819 static int ssh_msg (WPARAM wParam, LPARAM lParam) {
 820     int ret;
 821     char buf[256];
 822
 823     /*
 824      * Because reading less than the whole of the available pending
 825      * data can generate an FD_READ event, we need to allow for the
 826      * possibility that FD_READ may arrive with FD_CLOSE already in
 827      * the queue; so it's possible that we can get here even with s
 828      * invalid. If so, we return 1 and don't worry about it.
 829      */
 830     if (s == INVALID_SOCKET)
 831         return 1;
 832
 833     if (WSAGETSELECTERROR(lParam) != 0)
 834         return -WSAGETSELECTERROR(lParam);
 835
 836     switch (WSAGETSELECTEVENT(lParam)) {
 837       case FD_READ:
 838       case FD_CLOSE:
 839         ret = recv(s, buf, sizeof(buf), 0);
 840         if (ret < 0 && WSAGetLastError() == WSAEWOULDBLOCK)
 841             return 1;
 842         if (ret < 0)                   /* any _other_ error */
 843             return -10000-WSAGetLastError();
 844         if (ret == 0) {
 845             s = INVALID_SOCKET;
 846             return 0;
 847         }
 848         ssh_gotdata (buf, ret);
 849         return 1;
 850     }
 851     return 1;                          /* shouldn't happen, but WTF */
 852 }
 853
 854 /*
 855  * Called to send data down the Telnet connection.
 856  */
 857 static void ssh_send (char *buf, int len) {
 858     if (s == INVALID_SOCKET)
 859         return;
 860
 861     ssh_protocol(buf, len, 0);
 862 }
 863
 864 /*
 865  * Called to set the size of the window from Telnet's POV.
 866  */
 867 static void ssh_size(void) {
 868     switch (ssh_state) {
 869       case SSH_STATE_BEFORE_SIZE:
 870       case SSH_STATE_CLOSED:
 871         break;                         /* do nothing */
 872       case SSH_STATE_INTERMED:
 873         size_needed = TRUE;            /* buffer for later */
 874         break;
 875       case SSH_STATE_SESSION:
 876         if (!cfg.nopty) {
 877             s_wrpkt_start(11, 16);
 878             pktout.body[0] = (rows >> 24) & 0xFF;
 879             pktout.body[1] = (rows >> 16) & 0xFF;
 880             pktout.body[2] = (rows >> 8) & 0xFF;
 881             pktout.body[3] = rows & 0xFF;
 882             pktout.body[4] = (cols >> 24) & 0xFF;
 883             pktout.body[5] = (cols >> 16) & 0xFF;
 884             pktout.body[6] = (cols >> 8) & 0xFF;
 885             pktout.body[7] = cols & 0xFF;
 886             memset(pktout.body+8, 0, 8);
 887             s_wrpkt();
 888         }
 889     }
 890 }
 891
 892 /*
 893  * (Send Telnet special codes)
 894  */
 895 static void ssh_special (Telnet_Special code) {
 896     /* do nothing */
 897 }
 898
 899 Backend ssh_backend = {
 900     ssh_init,
 901     ssh_msg,
 902     ssh_send,
 903     ssh_size,
 904     ssh_special
 905 };