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

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <stdarg.h>
   4 #include <assert.h>
   5 #include <winsock.h>
   6
   7 #include "putty.h"
   8 #include "ssh.h"
   9 #include "scp.h"
  10
  11 #ifndef FALSE
  12 #define FALSE 0
  13 #endif
  14 #ifndef TRUE
  15 #define TRUE 1
  16 #endif
  17
  18 #define logevent(s) { logevent(s); \
  19                       if (IS_SCP && (scp_flags & SCP_VERBOSE) != 0) \
  20                       fprintf(stderr, "%s\n", s); }
  21
  22 #define SSH_MSG_DISCONNECT      1
  23 #define SSH_SMSG_PUBLIC_KEY     2
  24 #define SSH_CMSG_SESSION_KEY    3
  25 #define SSH_CMSG_USER           4
  26 #define SSH_CMSG_AUTH_PASSWORD  9
  27 #define SSH_CMSG_REQUEST_PTY    10
  28 #define SSH_CMSG_WINDOW_SIZE    11
  29 #define SSH_CMSG_EXEC_SHELL     12
  30 #define SSH_CMSG_EXEC_CMD       13
  31 #define SSH_SMSG_SUCCESS        14
  32 #define SSH_SMSG_FAILURE        15
  33 #define SSH_CMSG_STDIN_DATA     16
  34 #define SSH_SMSG_STDOUT_DATA    17
  35 #define SSH_SMSG_STDERR_DATA    18
  36 #define SSH_CMSG_EOF            19
  37 #define SSH_SMSG_EXIT_STATUS    20
  38 #define SSH_CMSG_EXIT_CONFIRMATION      33
  39 #define SSH_MSG_IGNORE          32
  40 #define SSH_MSG_DEBUG           36
  41 #define SSH_CMSG_AUTH_TIS       39
  42 #define SSH_SMSG_AUTH_TIS_CHALLENGE     40
  43 #define SSH_CMSG_AUTH_TIS_RESPONSE      41
  44
  45 #define SSH_AUTH_TIS            5
  46
  47 #define GET_32BIT(cp) \
  48     (((unsigned long)(unsigned char)(cp)[0] << 24) | \
  49     ((unsigned long)(unsigned char)(cp)[1] << 16) | \
  50     ((unsigned long)(unsigned char)(cp)[2] << 8) | \
  51     ((unsigned long)(unsigned char)(cp)[3]))
  52
  53 #define PUT_32BIT(cp, value) { \
  54     (cp)[0] = (unsigned char)((value) >> 24); \
  55     (cp)[1] = (unsigned char)((value) >> 16); \
  56     (cp)[2] = (unsigned char)((value) >> 8); \
  57     (cp)[3] = (unsigned char)(value); }
  58
  59 enum { PKT_END, PKT_INT, PKT_CHAR, PKT_DATA, PKT_STR };
  60
  61 /* Coroutine mechanics for the sillier bits of the code */
  62 #define crBegin1        static int crLine = 0;
  63 #define crBegin2        switch(crLine) { case 0:;
  64 #define crBegin         crBegin1; crBegin2;
  65 #define crFinish(z)     } crLine = 0; return (z)
  66 #define crFinishV       } crLine = 0; return
  67 #define crReturn(z)     \
  68         do {\
  69             crLine=__LINE__; return (z); case __LINE__:;\
  70         } while (0)
  71 #define crReturnV       \
  72         do {\
  73             crLine=__LINE__; return; case __LINE__:;\
  74         } while (0)
  75 #define crStop(z)       do{ crLine = 0; return (z); }while(0)
  76 #define crStopV         do{ crLine = 0; return; }while(0)
  77 #define crWaitUntil(c)  do { crReturn(0); } while (!(c))
  78
  79 static SOCKET s = INVALID_SOCKET;
  80
  81 static unsigned char session_key[32];
  82 static struct ssh_cipher *cipher = NULL;
  83 int scp_flags = 0;
  84 int (*ssh_get_password)(const char *prompt, char *str, int maxlen) = NULL;
  85
  86 static char *savedhost;
  87
  88 static enum {
  89     SSH_STATE_BEFORE_SIZE,
  90     SSH_STATE_INTERMED,
  91     SSH_STATE_SESSION,
  92     SSH_STATE_CLOSED
  93 } ssh_state = SSH_STATE_BEFORE_SIZE;
  94
  95 static int size_needed = FALSE;
  96
  97 static void s_write (char *buf, int len) {
  98     while (len > 0) {
  99         int i = send (s, buf, len, 0);
 100         if (IS_SCP) {
 101             noise_ultralight(i);
 102             if (i <= 0)
 103                 fatalbox("Lost connection while sending");
 104         }
 105         if (i > 0)
 106             len -= i, buf += i;
 107     }
 108 }
 109
 110 static int s_read (char *buf, int len) {
 111     int ret = 0;
 112     while (len > 0) {
 113         int i = recv (s, buf, len, 0);
 114         if (IS_SCP)
 115             noise_ultralight(i);
 116         if (i > 0)
 117             len -= i, buf += i, ret += i;
 118         else
 119             return i;
 120     }
 121     return ret;
 122 }
 123
 124 static void c_write (char *buf, int len) {
 125     if (IS_SCP) {
 126         if (len > 0 && buf[len-1] == '\n') len--;
 127         if (len > 0 && buf[len-1] == '\r') len--;
 128         if (len > 0) { fwrite(buf, len, 1, stderr); fputc('\n', stderr); }
 129         return;
 130     }
 131     while (len--)
 132         c_write1(*buf++);
 133 }
 134
 135 struct Packet {
 136     long length;
 137     int type;
 138     unsigned char *data;
 139     unsigned char *body;
 140     long maxlen;
 141 };
 142
 143 static struct Packet pktin = { 0, 0, NULL, NULL, 0 };
 144 static struct Packet pktout = { 0, 0, NULL, NULL, 0 };
 145
 146 static void ssh_protocol(unsigned char *in, int inlen, int ispkt);
 147 static void ssh_size(void);
 148
 149
 150 /*
 151  * Collect incoming data in the incoming packet buffer.
 152  * Decihper and verify the packet when it is completely read.
 153  * Drop SSH_MSG_DEBUG and SSH_MSG_IGNORE packets.
 154  * Update the *data and *datalen variables.
 155  * Return the additional nr of bytes needed, or 0 when
 156  * a complete packet is available.
 157  */
 158 static int s_rdpkt(unsigned char **data, int *datalen)
 159 {
 160     static long len, pad, biglen, to_read;
 161     static unsigned long realcrc, gotcrc;
 162     static unsigned char *p;
 163     static int i;
 164
 165     crBegin;
 166
 167 next_packet:
 168
 169     pktin.type = 0;
 170     pktin.length = 0;
 171
 172     for (i = len = 0; i < 4; i++) {
 173         while ((*datalen) == 0)
 174             crReturn(4-i);
 175         len = (len << 8) + **data;
 176         (*data)++, (*datalen)--;
 177     }
 178
 179 #ifdef FWHACK
 180     if (len == 0x52656d6f) {       /* "Remo"te server has closed ... */
 181         len = 0x300;               /* big enough to carry to end */
 182     }
 183 #endif
 184
 185     pad = 8 - (len % 8);
 186     biglen = len + pad;
 187     pktin.length = len - 5;
 188
 189     if (pktin.maxlen < biglen) {
 190         pktin.maxlen = biglen;
 191 #ifdef MSCRYPTOAPI
 192         /* Allocate enough buffer space for extra block
 193          * for MS CryptEncrypt() */
 194         pktin.data = (pktin.data == NULL ? malloc(biglen+8) :
 195                       realloc(pktin.data, biglen+8));
 196 #else
 197         pktin.data = (pktin.data == NULL ? malloc(biglen) :
 198                       realloc(pktin.data, biglen));
 199 #endif
 200         if (!pktin.data)
 201             fatalbox("Out of memory");
 202     }
 203
 204     to_read = biglen;
 205     p = pktin.data;
 206     while (to_read > 0) {
 207         static int chunk;
 208         chunk = to_read;
 209         while ((*datalen) == 0)
 210             crReturn(to_read);
 211         if (chunk > (*datalen))
 212             chunk = (*datalen);
 213         memcpy(p, *data, chunk);
 214         *data += chunk;
 215         *datalen -= chunk;
 216         p += chunk;
 217         to_read -= chunk;
 218     }
 219
 220     if (cipher)
 221         cipher->decrypt(pktin.data, biglen);
 222
 223     pktin.type = pktin.data[pad];
 224     pktin.body = pktin.data + pad + 1;
 225
 226     realcrc = crc32(pktin.data, biglen-4);
 227     gotcrc = GET_32BIT(pktin.data+biglen-4);
 228     if (gotcrc != realcrc) {
 229         fatalbox("Incorrect CRC received on packet");
 230     }
 231
 232     if (pktin.type == SSH_SMSG_STDOUT_DATA ||
 233         pktin.type == SSH_SMSG_STDERR_DATA ||
 234         pktin.type == SSH_MSG_DEBUG ||
 235         pktin.type == SSH_SMSG_AUTH_TIS_CHALLENGE) {
 236         long strlen = GET_32BIT(pktin.body);
 237         if (strlen + 4 != pktin.length)
 238             fatalbox("Received data packet with bogus string length");
 239     }
 240
 241     if (pktin.type == SSH_MSG_DEBUG) {
 242         /* log debug message */
 243         char buf[80];
 244         int strlen = GET_32BIT(pktin.body);
 245         strcpy(buf, "Remote: ");
 246         if (strlen > 70) strlen = 70;
 247         memcpy(buf+8, pktin.body+4, strlen);
 248         buf[8+strlen] = '\0';
 249         logevent(buf);
 250         goto next_packet;
 251     } else if (pktin.type == SSH_MSG_IGNORE) {
 252         /* do nothing */
 253         goto next_packet;
 254     }
 255
 256     crFinish(0);
 257 }
 258
 259 static void ssh_gotdata(unsigned char *data, int datalen)
 260 {
 261     while (datalen > 0) {
 262         if ( s_rdpkt(&data, &datalen) == 0 ) {
 263             ssh_protocol(NULL, 0, 1);
 264             if (ssh_state == SSH_STATE_CLOSED) {
 265                 return;
 266             }
 267         }
 268     }
 269 }
 270
 271
 272 static void s_wrpkt_start(int type, int len) {
 273     int pad, biglen;
 274
 275     len += 5;                          /* type and CRC */
 276     pad = 8 - (len%8);
 277     biglen = len + pad;
 278
 279     pktout.length = len-5;
 280     if (pktout.maxlen < biglen) {
 281         pktout.maxlen = biglen;
 282 #ifdef MSCRYPTOAPI
 283         /* Allocate enough buffer space for extra block
 284          * for MS CryptEncrypt() */
 285         pktout.data = (pktout.data == NULL ? malloc(biglen+12) :
 286                        realloc(pktout.data, biglen+12));
 287 #else
 288         pktout.data = (pktout.data == NULL ? malloc(biglen+4) :
 289                        realloc(pktout.data, biglen+4));
 290 #endif
 291         if (!pktout.data)
 292             fatalbox("Out of memory");
 293     }
 294
 295     pktout.type = type;
 296     pktout.body = pktout.data+4+pad+1;
 297 }
 298
 299 static void s_wrpkt(void) {
 300     int pad, len, biglen, i;
 301     unsigned long crc;
 302
 303     len = pktout.length + 5;           /* type and CRC */
 304     pad = 8 - (len%8);
 305     biglen = len + pad;
 306
 307     pktout.body[-1] = pktout.type;
 308     for (i=0; i<pad; i++)
 309         pktout.data[i+4] = random_byte();
 310     crc = crc32(pktout.data+4, biglen-4);
 311     PUT_32BIT(pktout.data+biglen, crc);
 312     PUT_32BIT(pktout.data, len);
 313
 314     if (cipher)
 315         cipher->encrypt(pktout.data+4, biglen);
 316
 317     s_write(pktout.data, biglen+4);
 318 }
 319
 320 /*
 321  * Construct a packet with the specified contents and
 322  * send it to the server.
 323  */
 324 static void send_packet(int pkttype, ...)
 325 {
 326     va_list args;
 327     unsigned char *p, *argp, argchar;
 328     unsigned long argint;
 329     int pktlen, argtype, arglen;
 330
 331     pktlen = 0;
 332     va_start(args, pkttype);
 333     while ((argtype = va_arg(args, int)) != PKT_END) {
 334         switch (argtype) {
 335           case PKT_INT:
 336             (void) va_arg(args, int);
 337             pktlen += 4;
 338             break;
 339           case PKT_CHAR:
 340             (void) va_arg(args, char);
 341             pktlen++;
 342             break;
 343           case PKT_DATA:
 344             (void) va_arg(args, unsigned char *);
 345             arglen = va_arg(args, int);
 346             pktlen += arglen;
 347             break;
 348           case PKT_STR:
 349             argp = va_arg(args, unsigned char *);
 350             arglen = strlen(argp);
 351             pktlen += 4 + arglen;
 352             break;
 353           default:
 354             assert(0);
 355         }
 356     }
 357     va_end(args);
 358
 359     s_wrpkt_start(pkttype, pktlen);
 360     p = pktout.body;
 361
 362     va_start(args, pkttype);
 363     while ((argtype = va_arg(args, int)) != PKT_END) {
 364         switch (argtype) {
 365           case PKT_INT:
 366             argint = va_arg(args, int);
 367             PUT_32BIT(p, argint);
 368             p += 4;
 369             break;
 370           case PKT_CHAR:
 371             argchar = va_arg(args, unsigned char);
 372             *p = argchar;
 373             p++;
 374             break;
 375           case PKT_DATA:
 376             argp = va_arg(args, unsigned char *);
 377             arglen = va_arg(args, int);
 378             memcpy(p, argp, arglen);
 379             p += arglen;
 380             break;
 381           case PKT_STR:
 382             argp = va_arg(args, unsigned char *);
 383             arglen = strlen(argp);
 384             PUT_32BIT(p, arglen);
 385             memcpy(p + 4, argp, arglen);
 386             p += 4 + arglen;
 387             break;
 388         }
 389     }
 390     va_end(args);
 391
 392     s_wrpkt();
 393 }
 394
 395
 396 /*
 397  * Connect to specified host and port.
 398  * Returns an error message, or NULL on success.
 399  * Also places the canonical host name into `realhost'.
 400  */
 401 static char *connect_to_host(char *host, int port, char **realhost)
 402 {
 403     SOCKADDR_IN addr;
 404     struct hostent *h;
 405     unsigned long a;
 406 #ifdef FWHACK
 407     char *FWhost;
 408     int FWport;
 409 #endif
 410
 411     savedhost = malloc(1+strlen(host));
 412     if (!savedhost)
 413         fatalbox("Out of memory");
 414     strcpy(savedhost, host);
 415
 416     if (port < 0)
 417         port = 22;                     /* default ssh port */
 418
 419 #ifdef FWHACK
 420     FWhost = host;
 421     FWport = port;
 422     host = FWSTR;
 423     port = 23;
 424 #endif
 425
 426     /*
 427      * Try to find host.
 428      */
 429     if ( (a = inet_addr(host)) == (unsigned long) INADDR_NONE) {
 430         if ( (h = gethostbyname(host)) == NULL)
 431             switch (WSAGetLastError()) {
 432               case WSAENETDOWN: return "Network is down";
 433               case WSAHOST_NOT_FOUND: case WSANO_DATA:
 434                 return "Host does not exist";
 435               case WSATRY_AGAIN: return "Host not found";
 436               default: return "gethostbyname: unknown error";
 437             }
 438         memcpy (&a, h->h_addr, sizeof(a));
 439         *realhost = h->h_name;
 440     } else
 441         *realhost = host;
 442 #ifdef FWHACK
 443     *realhost = FWhost;
 444 #endif
 445     a = ntohl(a);
 446
 447     /*
 448      * Open socket.
 449      */
 450     s = socket(AF_INET, SOCK_STREAM, 0);
 451     if (s == INVALID_SOCKET)
 452         switch (WSAGetLastError()) {
 453           case WSAENETDOWN: return "Network is down";
 454           case WSAEAFNOSUPPORT: return "TCP/IP support not present";
 455           default: return "socket(): unknown error";
 456         }
 457
 458     /*
 459      * Bind to local address.
 460      */
 461     addr.sin_family = AF_INET;
 462     addr.sin_addr.s_addr = htonl(INADDR_ANY);
 463     addr.sin_port = htons(0);
 464     if (bind (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 465         switch (WSAGetLastError()) {
 466           case WSAENETDOWN: return "Network is down";
 467           default: return "bind(): unknown error";
 468         }
 469
 470     /*
 471      * Connect to remote address.
 472      */
 473     addr.sin_addr.s_addr = htonl(a);
 474     addr.sin_port = htons((short)port);
 475     if (connect (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 476         switch (WSAGetLastError()) {
 477           case WSAENETDOWN: return "Network is down";
 478           case WSAECONNREFUSED: return "Connection refused";
 479           case WSAENETUNREACH: return "Network is unreachable";
 480           case WSAEHOSTUNREACH: return "No route to host";
 481           default: return "connect(): unknown error";
 482         }
 483
 484 #ifdef FWHACK
 485     send(s, "connect ", 8, 0);
 486     send(s, FWhost, strlen(FWhost), 0);
 487     {
 488         char buf[20];
 489         sprintf(buf, " %d\n", FWport);
 490         send (s, buf, strlen(buf), 0);
 491     }
 492 #endif
 493
 494     return NULL;
 495 }
 496
 497 static int ssh_versioncmp(char *a, char *b) {
 498     char *ae, *be;
 499     unsigned long av, bv;
 500
 501     av = strtoul(a, &ae, 10);
 502     bv = strtoul(b, &be, 10);
 503     if (av != bv) return (av < bv ? -1 : +1);
 504     if (*ae == '.') ae++;
 505     if (*be == '.') be++;
 506     av = strtoul(ae, &ae, 10);
 507     bv = strtoul(be, &be, 10);
 508     if (av != bv) return (av < bv ? -1 : +1);
 509     return 0;
 510 }
 511
 512 static int do_ssh_init(void) {
 513     char c, *vsp;
 514     char version[10];
 515     char vstring[80];
 516     char vlog[sizeof(vstring)+20];
 517     int i;
 518
 519 #ifdef FWHACK
 520     i = 0;
 521     while (s_read(&c, 1) == 1) {
 522         if (c == 'S' && i < 2) i++;
 523         else if (c == 'S' && i == 2) i = 2;
 524         else if (c == 'H' && i == 2) break;
 525         else i = 0;
 526     }
 527 #else
 528     if (s_read(&c,1) != 1 || c != 'S') return 0;
 529     if (s_read(&c,1) != 1 || c != 'S') return 0;
 530     if (s_read(&c,1) != 1 || c != 'H') return 0;
 531 #endif
 532     strcpy(vstring, "SSH-");
 533     vsp = vstring+4;
 534     if (s_read(&c,1) != 1 || c != '-') return 0;
 535     i = 0;
 536     while (1) {
 537         if (s_read(&c,1) != 1)
 538             return 0;
 539         if (vsp < vstring+sizeof(vstring)-1)
 540             *vsp++ = c;
 541         if (i >= 0) {
 542             if (c == '-') {
 543                 version[i] = '\0';
 544                 i = -1;
 545             } else if (i < sizeof(version)-1)
 546                 version[i++] = c;
 547         }
 548         else if (c == '\n')
 549             break;
 550     }
 551
 552     *vsp = 0;
 553     sprintf(vlog, "Server version: %s", vstring);
 554     vlog[strcspn(vlog, "\r\n")] = '\0';
 555     logevent(vlog);
 556
 557     sprintf(vstring, "SSH-%s-PuTTY\n",
 558             (ssh_versioncmp(version, "1.5") <= 0 ? version : "1.5"));
 559     sprintf(vlog, "We claim version: %s", vstring);
 560     vlog[strcspn(vlog, "\r\n")] = '\0';
 561     logevent(vlog);
 562     s_write(vstring, strlen(vstring));
 563     return 1;
 564 }
 565
 566 /*
 567  * Handle the key exchange and user authentication phases.
 568  */
 569 static int do_ssh_login(unsigned char *in, int inlen, int ispkt)
 570 {
 571     int i, j, len;
 572     unsigned char session_id[16];
 573     unsigned char *rsabuf, *keystr1, *keystr2;
 574     unsigned char cookie[8];
 575     struct RSAKey servkey, hostkey;
 576     struct MD5Context md5c;
 577     static unsigned long supported_ciphers_mask, supported_auths_mask;
 578     int cipher_type;
 579
 580     extern struct ssh_cipher ssh_3des;
 581     extern struct ssh_cipher ssh_des;
 582     extern struct ssh_cipher ssh_blowfish;
 583
 584     crBegin;
 585
 586     if (!ispkt) crWaitUntil(ispkt);
 587
 588     if (pktin.type != SSH_SMSG_PUBLIC_KEY)
 589         fatalbox("Public key packet not received");
 590
 591     logevent("Received public keys");
 592
 593     memcpy(cookie, pktin.body, 8);
 594
 595     i = makekey(pktin.body+8, &servkey, &keystr1);
 596     j = makekey(pktin.body+8+i, &hostkey, &keystr2);
 597
 598     /*
 599      * Hash the host key and print the hash in the log box. Just as
 600      * a last resort in case the registry's host key checking is
 601      * compromised, we'll allow the user some ability to verify
 602      * host keys by eye.
 603      */
 604     MD5Init(&md5c);
 605     MD5Update(&md5c, keystr2, hostkey.bytes);
 606     MD5Final(session_id, &md5c);
 607     {
 608         char logmsg[80];
 609         int i;
 610         logevent("Host key MD5 is:");
 611         strcpy(logmsg, "      ");
 612         for (i = 0; i < 16; i++)
 613             sprintf(logmsg+strlen(logmsg), "%02x", session_id[i]);
 614         logevent(logmsg);
 615     }
 616
 617     supported_ciphers_mask = GET_32BIT(pktin.body+12+i+j);
 618     supported_auths_mask = GET_32BIT(pktin.body+16+i+j);
 619
 620     MD5Init(&md5c);
 621     MD5Update(&md5c, keystr2, hostkey.bytes);
 622     MD5Update(&md5c, keystr1, servkey.bytes);
 623     MD5Update(&md5c, pktin.body, 8);
 624     MD5Final(session_id, &md5c);
 625
 626     for (i=0; i<32; i++)
 627         session_key[i] = random_byte();
 628
 629     len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 630
 631     rsabuf = malloc(len);
 632     if (!rsabuf)
 633         fatalbox("Out of memory");
 634
 635     /*
 636      * Verify the host key.
 637      */
 638     {
 639         /*
 640          * First format the key into a string.
 641          */
 642         int len = rsastr_len(&hostkey);
 643         char *keystr = malloc(len);
 644         if (!keystr)
 645             fatalbox("Out of memory");
 646         rsastr_fmt(keystr, &hostkey);
 647         verify_ssh_host_key(savedhost, keystr);
 648         free(keystr);
 649     }
 650
 651     for (i=0; i<32; i++) {
 652         rsabuf[i] = session_key[i];
 653         if (i < 16)
 654             rsabuf[i] ^= session_id[i];
 655     }
 656
 657     if (hostkey.bytes > servkey.bytes) {
 658         rsaencrypt(rsabuf, 32, &servkey);
 659         rsaencrypt(rsabuf, servkey.bytes, &hostkey);
 660     } else {
 661         rsaencrypt(rsabuf, 32, &hostkey);
 662         rsaencrypt(rsabuf, hostkey.bytes, &servkey);
 663     }
 664
 665     logevent("Encrypted session key");
 666
 667     cipher_type = cfg.cipher == CIPHER_BLOWFISH ? SSH_CIPHER_BLOWFISH :
 668                   cfg.cipher == CIPHER_DES ? SSH_CIPHER_DES :
 669                   SSH_CIPHER_3DES;
 670     if ((supported_ciphers_mask & (1 << cipher_type)) == 0) {
 671         c_write("Selected cipher not supported, falling back to 3DES\r\n", 53);
 672         cipher_type = SSH_CIPHER_3DES;
 673     }
 674     switch (cipher_type) {
 675       case SSH_CIPHER_3DES: logevent("Using 3DES encryption"); break;
 676       case SSH_CIPHER_DES: logevent("Using single-DES encryption"); break;
 677       case SSH_CIPHER_BLOWFISH: logevent("Using Blowfish encryption"); break;
 678     }
 679
 680     send_packet(SSH_CMSG_SESSION_KEY,
 681                 PKT_CHAR, cipher_type,
 682                 PKT_DATA, cookie, 8,
 683                 PKT_CHAR, (len*8) >> 8, PKT_CHAR, (len*8) & 0xFF,
 684                 PKT_DATA, rsabuf, len,
 685                 PKT_INT, 0,
 686                 PKT_END);
 687
 688     logevent("Trying to enable encryption...");
 689
 690     free(rsabuf);
 691
 692     cipher = cipher_type == SSH_CIPHER_BLOWFISH ? &ssh_blowfish :
 693              cipher_type == SSH_CIPHER_DES ? &ssh_des :
 694              &ssh_3des;
 695     cipher->sesskey(session_key);
 696
 697     crWaitUntil(ispkt);
 698
 699     if (pktin.type != SSH_SMSG_SUCCESS)
 700         fatalbox("Encryption not successfully enabled");
 701
 702     logevent("Successfully started encryption");
 703
 704     fflush(stdout);
 705     {
 706         static char username[100];
 707         static int pos = 0;
 708         static char c;
 709         if (!IS_SCP && !*cfg.username) {
 710             c_write("login as: ", 10);
 711             while (pos >= 0) {
 712                 crWaitUntil(!ispkt);
 713                 while (inlen--) switch (c = *in++) {
 714                   case 10: case 13:
 715                     username[pos] = 0;
 716                     pos = -1;
 717                     break;
 718                   case 8: case 127:
 719                     if (pos > 0) {
 720                         c_write("\b \b", 3);
 721                         pos--;
 722                     }
 723                     break;
 724                   case 21: case 27:
 725                     while (pos > 0) {
 726                         c_write("\b \b", 3);
 727                         pos--;
 728                     }
 729                     break;
 730                   case 3: case 4:
 731                     random_save_seed();
 732                     exit(0);
 733                     break;
 734                   default:
 735                     if (((c >= ' ' && c <= '~') ||
 736                          ((unsigned char)c >= 160)) && pos < 40) {
 737                         username[pos++] = c;
 738                         c_write(&c, 1);
 739                     }
 740                     break;
 741                 }
 742             }
 743             c_write("\r\n", 2);
 744             username[strcspn(username, "\n\r")] = '\0';
 745         } else {
 746             char stuff[200];
 747             strncpy(username, cfg.username, 99);
 748             username[99] = '\0';
 749             if (!IS_SCP) {
 750                 sprintf(stuff, "Sent username \"%s\".\r\n", username);
 751                 c_write(stuff, strlen(stuff));
 752             }
 753         }
 754
 755         send_packet(SSH_CMSG_USER, PKT_STR, username, PKT_END);
 756         {
 757             char userlog[20+sizeof(username)];
 758             sprintf(userlog, "Sent username \"%s\"", username);
 759             logevent(userlog);
 760         }
 761     }
 762
 763     crWaitUntil(ispkt);
 764
 765     while (pktin.type == SSH_SMSG_FAILURE) {
 766         static char password[100];
 767         static int pos;
 768         static char c;
 769         static int pwpkt_type;
 770
 771         /*
 772          * Show password prompt, having first obtained it via a TIS
 773          * exchange if we're doing TIS authentication.
 774          */
 775         pwpkt_type = SSH_CMSG_AUTH_PASSWORD;
 776
 777         if (IS_SCP) {
 778             char prompt[200];
 779             sprintf(prompt, "%s@%s's password: ", cfg.username, savedhost);
 780             if (!ssh_get_password(prompt, password, sizeof(password))) {
 781                 /*
 782                  * get_password failed to get a password (for
 783                  * example because one was supplied on the command
 784                  * line which has already failed to work).
 785                  * Terminate.
 786                  */
 787                 logevent("No more passwords to try");
 788                 ssh_state = SSH_STATE_CLOSED;
 789                 crReturn(1);
 790             }
 791         } else {
 792
 793         if (pktin.type == SSH_SMSG_FAILURE &&
 794             cfg.try_tis_auth &&
 795             (supported_auths_mask & (1<<SSH_AUTH_TIS))) {
 796             pwpkt_type = SSH_CMSG_AUTH_TIS_RESPONSE;
 797             logevent("Requested TIS authentication");
 798             send_packet(SSH_CMSG_AUTH_TIS, PKT_END);
 799             crWaitUntil(ispkt);
 800             if (pktin.type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
 801                 logevent("TIS authentication declined");
 802                 c_write("TIS authentication refused.\r\n", 29);
 803             } else {
 804                 int challengelen = ((pktin.body[0] << 24) |
 805                                     (pktin.body[1] << 16) |
 806                                     (pktin.body[2] << 8) |
 807                                     (pktin.body[3]));
 808                 logevent("Received TIS challenge");
 809                 c_write(pktin.body+4, challengelen);
 810             }
 811         }
 812         if (pwpkt_type == SSH_CMSG_AUTH_PASSWORD)
 813             c_write("password: ", 10);
 814
 815         pos = 0;
 816         while (pos >= 0) {
 817             crWaitUntil(!ispkt);
 818             while (inlen--) switch (c = *in++) {
 819               case 10: case 13:
 820                 password[pos] = 0;
 821                 pos = -1;
 822                 break;
 823               case 8: case 127:
 824                 if (pos > 0)
 825                     pos--;
 826                 break;
 827               case 21: case 27:
 828                 pos = 0;
 829                 break;
 830               case 3: case 4:
 831                 random_save_seed();
 832                 exit(0);
 833                 break;
 834               default:
 835                 if (((c >= ' ' && c <= '~') ||
 836                      ((unsigned char)c >= 160)) && pos < 40)
 837                     password[pos++] = c;
 838                 break;
 839             }
 840         }
 841         c_write("\r\n", 2);
 842
 843         }
 844
 845         send_packet(pwpkt_type, PKT_STR, password, PKT_END);
 846         logevent("Sent password");
 847         memset(password, 0, strlen(password));
 848         crWaitUntil(ispkt);
 849         if (pktin.type == SSH_SMSG_FAILURE) {
 850             c_write("Access denied\r\n", 15);
 851             logevent("Authentication refused");
 852         } else if (pktin.type == SSH_MSG_DISCONNECT) {
 853             logevent("Received disconnect request");
 854             ssh_state = SSH_STATE_CLOSED;
 855             crReturn(1);
 856         } else if (pktin.type != SSH_SMSG_SUCCESS) {
 857             fatalbox("Strange packet received, type %d", pktin.type);
 858         }
 859     }
 860
 861     logevent("Authentication successful");
 862
 863     crFinish(1);
 864 }
 865
 866 static void ssh_protocol(unsigned char *in, int inlen, int ispkt) {
 867     crBegin;
 868
 869     random_init();
 870
 871     while (!do_ssh_login(in, inlen, ispkt)) {
 872         crReturnV;
 873     }
 874     if (ssh_state == SSH_STATE_CLOSED)
 875         crReturnV;
 876
 877     if (!cfg.nopty) {
 878         send_packet(SSH_CMSG_REQUEST_PTY,
 879                     PKT_STR, cfg.termtype,
 880                     PKT_INT, rows, PKT_INT, cols,
 881                     PKT_INT, 0, PKT_INT, 0,
 882                     PKT_CHAR, 0,
 883                     PKT_END);
 884         ssh_state = SSH_STATE_INTERMED;
 885         do { crReturnV; } while (!ispkt);
 886         if (pktin.type != SSH_SMSG_SUCCESS && pktin.type != SSH_SMSG_FAILURE) {
 887             fatalbox("Protocol confusion");
 888         } else if (pktin.type == SSH_SMSG_FAILURE) {
 889             c_write("Server refused to allocate pty\r\n", 32);
 890         }
 891         logevent("Allocated pty");
 892     }
 893
 894     send_packet(SSH_CMSG_EXEC_SHELL, PKT_END);
 895     logevent("Started session");
 896
 897     ssh_state = SSH_STATE_SESSION;
 898     if (size_needed)
 899         ssh_size();
 900
 901     while (1) {
 902         crReturnV;
 903         if (ispkt) {
 904             if (pktin.type == SSH_SMSG_STDOUT_DATA ||
 905                 pktin.type == SSH_SMSG_STDERR_DATA) {
 906                 long len = GET_32BIT(pktin.body);
 907                 c_write(pktin.body+4, len);
 908             } else if (pktin.type == SSH_MSG_DISCONNECT) {
 909                 ssh_state = SSH_STATE_CLOSED;
 910                 logevent("Received disconnect request");
 911             } else if (pktin.type == SSH_SMSG_SUCCESS) {
 912                 /* may be from EXEC_SHELL on some servers */
 913             } else if (pktin.type == SSH_SMSG_FAILURE) {
 914                 /* may be from EXEC_SHELL on some servers
 915                  * if no pty is available or in other odd cases. Ignore */
 916             } else if (pktin.type == SSH_SMSG_EXIT_STATUS) {
 917                 send_packet(SSH_CMSG_EXIT_CONFIRMATION, PKT_END);
 918             } else {
 919                 fatalbox("Strange packet received: type %d", pktin.type);
 920             }
 921         } else {
 922             send_packet(SSH_CMSG_STDIN_DATA,
 923                         PKT_INT, inlen, PKT_DATA, in, inlen, PKT_END);
 924         }
 925     }
 926
 927     crFinishV;
 928 }
 929
 930 /*
 931  * Called to set up the connection. Will arrange for WM_NETEVENT
 932  * messages to be passed to the specified window, whose window
 933  * procedure should then call telnet_msg().
 934  *
 935  * Returns an error message, or NULL on success.
 936  */
 937 static char *ssh_init (HWND hwnd, char *host, int port, char **realhost) {
 938     char *p;
 939
 940 #ifdef MSCRYPTOAPI
 941     if(crypto_startup() == 0)
 942         return "Microsoft high encryption pack not installed!";
 943 #endif
 944
 945     p = connect_to_host(host, port, realhost);
 946     if (p != NULL)
 947         return p;
 948
 949     if (!do_ssh_init())
 950         return "Protocol initialisation error";
 951
 952     if (WSAAsyncSelect (s, hwnd, WM_NETEVENT, FD_READ | FD_CLOSE) == SOCKET_ERROR)
 953         switch (WSAGetLastError()) {
 954           case WSAENETDOWN: return "Network is down";
 955           default: return "WSAAsyncSelect(): unknown error";
 956         }
 957
 958     return NULL;
 959 }
 960
 961 /*
 962  * Process a WM_NETEVENT message. Will return 0 if the connection
 963  * has closed, or <0 for a socket error.
 964  */
 965 static int ssh_msg (WPARAM wParam, LPARAM lParam) {
 966     int ret;
 967     char buf[256];
 968
 969     /*
 970      * Because reading less than the whole of the available pending
 971      * data can generate an FD_READ event, we need to allow for the
 972      * possibility that FD_READ may arrive with FD_CLOSE already in
 973      * the queue; so it's possible that we can get here even with s
 974      * invalid. If so, we return 1 and don't worry about it.
 975      */
 976     if (s == INVALID_SOCKET)
 977         return 1;
 978
 979     if (WSAGETSELECTERROR(lParam) != 0)
 980         return -WSAGETSELECTERROR(lParam);
 981
 982     switch (WSAGETSELECTEVENT(lParam)) {
 983       case FD_READ:
 984       case FD_CLOSE:
 985         ret = recv(s, buf, sizeof(buf), 0);
 986         if (ret < 0 && WSAGetLastError() == WSAEWOULDBLOCK)
 987             return 1;
 988         if (ret < 0)                   /* any _other_ error */
 989             return -10000-WSAGetLastError();
 990         if (ret == 0) {
 991             s = INVALID_SOCKET;
 992             return 0;
 993         }
 994         ssh_gotdata (buf, ret);
 995         if (ssh_state == SSH_STATE_CLOSED) {
 996             closesocket(s);
 997             s = INVALID_SOCKET;
 998             return 0;
 999         }
1000         return 1;
1001     }
1002     return 1;                          /* shouldn't happen, but WTF */
1003 }
1004
1005 /*
1006  * Called to send data down the Telnet connection.
1007  */
1008 static void ssh_send (char *buf, int len) {
1009     if (s == INVALID_SOCKET)
1010         return;
1011
1012     ssh_protocol(buf, len, 0);
1013 }
1014
1015 /*
1016  * Called to set the size of the window from Telnet's POV.
1017  */
1018 static void ssh_size(void) {
1019     switch (ssh_state) {
1020       case SSH_STATE_BEFORE_SIZE:
1021       case SSH_STATE_CLOSED:
1022         break;                         /* do nothing */
1023       case SSH_STATE_INTERMED:
1024         size_needed = TRUE;            /* buffer for later */
1025         break;
1026       case SSH_STATE_SESSION:
1027         if (!cfg.nopty) {
1028             send_packet(SSH_CMSG_WINDOW_SIZE,
1029                         PKT_INT, rows, PKT_INT, cols,
1030                         PKT_INT, 0, PKT_INT, 0, PKT_END);
1031         }
1032     }
1033 }
1034
1035 /*
1036  * (Send Telnet special codes)
1037  */
1038 static void ssh_special (Telnet_Special code) {
1039     /* do nothing */
1040 }
1041
1042
1043 /*
1044  * Read and decrypt one incoming SSH packet.
1045  * (only used by pSCP)
1046  */
1047 static void get_packet(void)
1048 {
1049     unsigned char buf[4096], *p;
1050     long to_read;
1051     int len;
1052
1053     assert(IS_SCP);
1054
1055     p = NULL;
1056     len = 0;
1057
1058     while ((to_read = s_rdpkt(&p, &len)) > 0) {
1059         if (to_read > sizeof(buf)) to_read = sizeof(buf);
1060         len = s_read(buf, to_read);
1061         if (len != to_read) {
1062             closesocket(s);
1063             s = INVALID_SOCKET;
1064             return;
1065         }
1066         p = buf;
1067     }
1068
1069     assert(len == 0);
1070 }
1071
1072 /*
1073  * Receive a block of data over the SSH link. Block until
1074  * all data is available. Return nr of bytes read (0 if lost connection).
1075  * (only used by pSCP)
1076  */
1077 int ssh_scp_recv(unsigned char *buf, int len)
1078 {
1079     static int pending_input_len = 0;
1080     static unsigned char *pending_input_ptr;
1081     int to_read = len;
1082
1083     assert(IS_SCP);
1084
1085     if (pending_input_len >= to_read) {
1086         memcpy(buf, pending_input_ptr, to_read);
1087         pending_input_ptr += to_read;
1088         pending_input_len -= to_read;
1089         return len;
1090     }
1091
1092     if (pending_input_len > 0) {
1093         memcpy(buf, pending_input_ptr, pending_input_len);
1094         buf += pending_input_len;
1095         to_read -= pending_input_len;
1096         pending_input_len = 0;
1097     }
1098
1099     if (s == INVALID_SOCKET)
1100         return 0;
1101     while (to_read > 0) {
1102         get_packet();
1103         if (s == INVALID_SOCKET)
1104             return 0;
1105         if (pktin.type == SSH_SMSG_STDOUT_DATA) {
1106             int plen = GET_32BIT(pktin.body);
1107             if (plen <= to_read) {
1108                 memcpy(buf, pktin.body + 4, plen);
1109                 buf += plen;
1110                 to_read -= plen;
1111             } else {
1112                 memcpy(buf, pktin.body + 4, to_read);
1113                 pending_input_len = plen - to_read;
1114                 pending_input_ptr = pktin.body + 4 + to_read;
1115                 to_read = 0;
1116             }
1117         } else if (pktin.type == SSH_SMSG_STDERR_DATA) {
1118             int plen = GET_32BIT(pktin.body);
1119             fwrite(pktin.body + 4, plen, 1, stderr);
1120         } else if (pktin.type == SSH_MSG_DISCONNECT) {
1121                 logevent("Received disconnect request");
1122         } else if (pktin.type == SSH_SMSG_SUCCESS ||
1123                    pktin.type == SSH_SMSG_FAILURE) {
1124                 /* ignore */
1125         } else if (pktin.type == SSH_SMSG_EXIT_STATUS) {
1126             char logbuf[100];
1127             sprintf(logbuf, "Remote exit status: %d", GET_32BIT(pktin.body));
1128             logevent(logbuf);
1129             send_packet(SSH_CMSG_EXIT_CONFIRMATION, PKT_END);
1130             logevent("Closing connection");
1131             closesocket(s);
1132             s = INVALID_SOCKET;
1133         } else {
1134             fatalbox("Strange packet received: type %d", pktin.type);
1135         }
1136     }
1137
1138     return len;
1139 }
1140
1141 /*
1142  * Send a block of data over the SSH link.
1143  * Block until all data is sent.
1144  * (only used by pSCP)
1145  */
1146 void ssh_scp_send(unsigned char *buf, int len)
1147 {
1148     assert(IS_SCP);
1149     if (s == INVALID_SOCKET)
1150         return;
1151     send_packet(SSH_CMSG_STDIN_DATA,
1152                 PKT_INT, len, PKT_DATA, buf, len, PKT_END);
1153 }
1154
1155 /*
1156  * Send an EOF notification to the server.
1157  * (only used by pSCP)
1158  */
1159 void ssh_scp_send_eof(void)
1160 {
1161     assert(IS_SCP);
1162     if (s == INVALID_SOCKET)
1163         return;
1164     send_packet(SSH_CMSG_EOF, PKT_END);
1165 }
1166
1167 /*
1168  * Set up the connection, login on the remote host and
1169  * start execution of a command.
1170  * Returns an error message, or NULL on success.
1171  * (only used by pSCP)
1172  */
1173 char *ssh_scp_init(char *host, int port, char *cmd, char **realhost)
1174 {
1175     char buf[160], *p;
1176
1177     assert(IS_SCP);
1178
1179 #ifdef MSCRYPTOAPI
1180     if (crypto_startup() == 0)
1181         return "Microsoft high encryption pack not installed!";
1182 #endif
1183
1184     p = connect_to_host(host, port, realhost);
1185     if (p != NULL)
1186         return p;
1187
1188     random_init();
1189
1190     if (!do_ssh_init())
1191         return "Protocol initialisation error";
1192
1193     /* Exchange keys and login */
1194     do {
1195         get_packet();
1196         if (s == INVALID_SOCKET)
1197             return "Connection closed by remote host";
1198     } while (!do_ssh_login(NULL, 0, 1));
1199
1200     if (ssh_state == SSH_STATE_CLOSED) {
1201         closesocket(s);
1202         s = INVALID_SOCKET;
1203         return "Session initialisation error";
1204     }
1205
1206     /* Execute command */
1207     sprintf(buf, "Sending command: %.100s", cmd);
1208     logevent(buf);
1209     send_packet(SSH_CMSG_EXEC_CMD, PKT_STR, cmd, PKT_END);
1210
1211     return NULL;
1212 }
1213
1214
1215 Backend ssh_backend = {
1216     ssh_init,
1217     ssh_msg,
1218     ssh_send,
1219     ssh_size,
1220     ssh_special
1221 };
1222