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