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

   1 /*
   2  *  scpssh.c  -  SSH implementation for PuTTY Secure Copy
   3  *  Joris van Rantwijk, Aug 1999.
   4  *  Based on PuTTY ssh.c by Simon Tatham.
   5  */
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <winsock.h>
  11
  12 #include "putty.h"
  13 #include "ssh.h"
  14 #include "scp.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_EXEC_CMD       13
  22 #define SSH_SMSG_SUCCESS        14
  23 #define SSH_SMSG_FAILURE        15
  24 #define SSH_CMSG_STDIN_DATA     16
  25 #define SSH_SMSG_STDOUT_DATA    17
  26 #define SSH_SMSG_STDERR_DATA    18
  27 #define SSH_CMSG_EOF            19
  28 #define SSH_SMSG_EXIT_STATUS    20
  29 #define SSH_CMSG_EXIT_CONFIRMATION      33
  30 #define SSH_MSG_IGNORE          32
  31 #define SSH_MSG_DEBUG           36
  32
  33 #define GET_32BIT(cp) \
  34     (((unsigned long)(unsigned char)(cp)[0] << 24) | \
  35     ((unsigned long)(unsigned char)(cp)[1] << 16) | \
  36     ((unsigned long)(unsigned char)(cp)[2] << 8) | \
  37     ((unsigned long)(unsigned char)(cp)[3]))
  38
  39 #define PUT_32BIT(cp, value) { \
  40     (cp)[0] = (unsigned char)((value) >> 24); \
  41     (cp)[1] = (unsigned char)((value) >> 16); \
  42     (cp)[2] = (unsigned char)((value) >> 8); \
  43     (cp)[3] = (unsigned char)(value); }
  44
  45 static SOCKET s = INVALID_SOCKET;
  46
  47 static unsigned char session_key[32];
  48 static struct ssh_cipher *cipher = NULL;
  49
  50 static char *savedhost;
  51
  52 struct Packet {
  53     long length;
  54     int type;
  55     unsigned long crc;
  56     unsigned char *data;
  57     unsigned char *body;
  58     long maxlen;
  59 };
  60
  61 static struct Packet pktin = { 0, 0, 0, NULL, 0 };
  62 static struct Packet pktout = { 0, 0, 0, NULL, 0 };
  63
  64
  65 static void s_write (char *buf, int len) {
  66     while (len > 0) {
  67         int i = send (s, buf, len, 0);
  68         noise_ultralight(i);
  69         if (i <= 0)
  70             fatalbox("Lost connection while sending");
  71         len -= i, buf += i;
  72     }
  73 }
  74
  75 static int s_read (char *buf, int len) {
  76     int ret = 0;
  77     while (len > 0) {
  78         int i = recv (s, buf, len, 0);
  79         noise_ultralight(i);
  80         if (i > 0)
  81             len -= i, buf += i, ret += i;
  82         else
  83             return i;
  84     }
  85     return ret;
  86 }
  87
  88 /*
  89  * Read and decrypt one incoming SSH packet.
  90  */
  91 static void get_packet(void)
  92 {
  93     unsigned char buf[4];
  94     int ret;
  95     int len, pad, biglen;
  96
  97 next_packet:
  98
  99     pktin.type = 0;
 100     pktin.length = 0;
 101
 102     ret = s_read(buf, 4);
 103     if (ret != 4) {
 104         closesocket(s);
 105         s = INVALID_SOCKET;
 106         return;
 107     }
 108
 109     len = GET_32BIT(buf);
 110
 111 #ifdef FWHACK
 112     if (len == 0x52656d6f) {
 113         len = 0x300;
 114     }
 115 #endif
 116
 117     pad = 8 - (len % 8);
 118     biglen = len + pad;
 119     len -= 5;                   /* type and CRC */
 120
 121     pktin.length = len;
 122     if (pktin.maxlen < biglen) {
 123         pktin.maxlen = biglen;
 124         pktin.data = (pktin.data == NULL) ?
 125                      smalloc(biglen) : srealloc(pktin.data, biglen);
 126     }
 127
 128     ret = s_read(pktin.data, biglen);
 129     if (ret != biglen) {
 130         closesocket(s);
 131         s = INVALID_SOCKET;
 132         return;
 133     }
 134
 135     if (cipher)
 136         cipher->decrypt(pktin.data, biglen);
 137
 138     pktin.type = pktin.data[pad];
 139     pktin.body = pktin.data + pad + 1;
 140
 141     if (pktin.type == SSH_MSG_DEBUG) {
 142         if (verbose) {
 143             int len = GET_32BIT(pktin.body);
 144             fprintf(stderr, "Remote: ");
 145             fwrite(pktin.body + 4, len, 1, stderr);
 146             fprintf(stderr, "\n");
 147         }
 148         goto next_packet;
 149     }
 150     if (pktin.type == SSH_MSG_IGNORE) {
 151         goto next_packet;
 152     }
 153 }
 154
 155 static void s_wrpkt_start(int type, int len) {
 156     int pad, biglen;
 157
 158     len += 5;                          /* type and CRC */
 159     pad = 8 - (len%8);
 160     biglen = len + pad;
 161
 162     pktout.length = len-5;
 163     if (pktout.maxlen < biglen) {
 164         pktout.maxlen = biglen;
 165         pktout.data = (pktout.data == NULL ? malloc(biglen+4) :
 166                        realloc(pktout.data, biglen+4));
 167         if (!pktout.data)
 168             fatalbox("Out of memory");
 169     }
 170
 171     pktout.type = type;
 172     pktout.body = pktout.data+4+pad+1;
 173 }
 174
 175 static void s_wrpkt(void) {
 176     int pad, len, biglen, i;
 177     unsigned long crc;
 178
 179     len = pktout.length + 5;           /* type and CRC */
 180     pad = 8 - (len%8);
 181     biglen = len + pad;
 182
 183     pktout.body[-1] = pktout.type;
 184     for (i=0; i<pad; i++)
 185         pktout.data[i+4] = random_byte();
 186     crc = crc32(pktout.data+4, biglen-4);
 187     PUT_32BIT(pktout.data+biglen, crc);
 188     PUT_32BIT(pktout.data, len);
 189
 190     if (cipher)
 191         cipher->encrypt(pktout.data+4, biglen);
 192
 193     s_write(pktout.data, biglen+4);
 194 }
 195
 196 static int do_ssh_init(void) {
 197     char c;
 198     char version[10];
 199     char vstring[40];
 200     int i;
 201
 202 #ifdef FWHACK
 203     i = 0;
 204     while (s_read(&c, 1) == 1) {
 205         if (c == 'S' && i < 2) i++;
 206         else if (c == 'S' && i == 2) i = 2;
 207         else if (c == 'H' && i == 2) break;
 208         else i = 0;
 209     }
 210 #else
 211     if (s_read(&c,1) != 1 || c != 'S') return 0;
 212     if (s_read(&c,1) != 1 || c != 'S') return 0;
 213     if (s_read(&c,1) != 1 || c != 'H') return 0;
 214 #endif
 215     if (s_read(&c,1) != 1 || c != '-') return 0;
 216     i = 0;
 217     while (1) {
 218         if (s_read(&c,1) != 1)
 219             return 0;
 220         if (i >= 0) {
 221             if (c == '-') {
 222                 version[i] = '\0';
 223                 i = -1;
 224             } else if (i < sizeof(version)-1)
 225                 version[i++] = c;
 226         }
 227         else if (c == '\n')
 228             break;
 229     }
 230
 231     sprintf(vstring, "SSH-%s-7.7.7\n",
 232             (strcmp(version, "1.5") <= 0 ? version : "1.5"));
 233     s_write(vstring, strlen(vstring));
 234     return 1;
 235 }
 236
 237
 238 /*
 239  * Login on the server and request execution of the command.
 240  */
 241 static void ssh_login(char *username, char *cmd)
 242 {
 243     int i, j, len;
 244     unsigned char session_id[16];
 245     unsigned char *rsabuf, *keystr1, *keystr2;
 246     unsigned char cookie[8];
 247     struct RSAKey servkey, hostkey;
 248     struct MD5Context md5c;
 249     unsigned long supported_ciphers_mask;
 250     int cipher_type;
 251
 252     extern struct ssh_cipher ssh_3des;
 253     extern struct ssh_cipher ssh_blowfish;
 254
 255     get_packet();
 256
 257     if (pktin.type != SSH_SMSG_PUBLIC_KEY)
 258         fatalbox("Public key packet not received");
 259
 260     memcpy(cookie, pktin.body, 8);
 261
 262     MD5Init(&md5c);
 263
 264     i = makekey(pktin.body+8, &servkey, &keystr1);
 265     j = makekey(pktin.body+8+i, &hostkey, &keystr2);
 266
 267     supported_ciphers_mask = GET_32BIT(pktin.body+12+i+j);
 268
 269     MD5Update(&md5c, keystr2, hostkey.bytes);
 270     MD5Update(&md5c, keystr1, servkey.bytes);
 271     MD5Update(&md5c, pktin.body, 8);
 272
 273     MD5Final(session_id, &md5c);
 274
 275     for (i=0; i<32; i++)
 276         session_key[i] = random_byte();
 277
 278     len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 279
 280     rsabuf = malloc(len);
 281     if (!rsabuf)
 282         fatalbox("Out of memory");
 283
 284     /*
 285      * Verify the host key.
 286      */
 287     {
 288         /*
 289          * First format the key into a string.
 290          */
 291         int len = rsastr_len(&hostkey);
 292         char *keystr = malloc(len);
 293         if (!keystr)
 294             fatalbox("Out of memory");
 295         rsastr_fmt(keystr, &hostkey);
 296         verify_ssh_host_key(savedhost, keystr);
 297         free(keystr);
 298     }
 299
 300     for (i=0; i<32; i++) {
 301         rsabuf[i] = session_key[i];
 302         if (i < 16)
 303             rsabuf[i] ^= session_id[i];
 304     }
 305
 306     if (hostkey.bytes > servkey.bytes) {
 307         rsaencrypt(rsabuf, 32, &servkey);
 308         rsaencrypt(rsabuf, servkey.bytes, &hostkey);
 309     } else {
 310         rsaencrypt(rsabuf, 32, &hostkey);
 311         rsaencrypt(rsabuf, hostkey.bytes, &servkey);
 312     }
 313
 314     cipher_type = cfg.cipher == CIPHER_BLOWFISH ? SSH_CIPHER_BLOWFISH :
 315                   SSH_CIPHER_3DES;
 316     if ((supported_ciphers_mask & (1 << cipher_type)) == 0) {
 317         fprintf(stderr, "Selected cipher not supported, falling back to 3DES\n");
 318         cipher_type = SSH_CIPHER_3DES;
 319     }
 320
 321     s_wrpkt_start(SSH_CMSG_SESSION_KEY, len+15);
 322     pktout.body[0] = cipher_type;
 323     memcpy(pktout.body+1, cookie, 8);
 324     pktout.body[9] = (len*8) >> 8;
 325     pktout.body[10] = (len*8) & 0xFF;
 326     memcpy(pktout.body+11, rsabuf, len);
 327     pktout.body[len+11] = pktout.body[len+12] = 0;   /* protocol flags */
 328     pktout.body[len+13] = pktout.body[len+14] = 0;
 329     s_wrpkt();
 330
 331     free(rsabuf);
 332
 333     cipher = cipher_type == SSH_CIPHER_BLOWFISH ? &ssh_blowfish :
 334              &ssh_3des;
 335     cipher->sesskey(session_key);
 336
 337     get_packet();
 338
 339     if (pktin.type != SSH_SMSG_SUCCESS)
 340         fatalbox("Encryption not successfully enabled");
 341
 342     if (verbose)
 343         fprintf(stderr, "Logging in as \"%s\".\n", username);
 344     s_wrpkt_start(SSH_CMSG_USER, 4+strlen(username));
 345     pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 346     pktout.body[3] = strlen(username);
 347     memcpy(pktout.body+4, username, strlen(username));
 348     s_wrpkt();
 349
 350     get_packet();
 351
 352     while (pktin.type == SSH_SMSG_FAILURE) {
 353         char password[100];
 354         char prompt[200];
 355         sprintf(prompt, "%s@%s's password: ", username, savedhost);
 356         ssh_get_password(prompt, password, 100);
 357         s_wrpkt_start(SSH_CMSG_AUTH_PASSWORD, 4+strlen(password));
 358         pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 359         pktout.body[3] = strlen(password);
 360         memcpy(pktout.body+4, password, strlen(password));
 361         s_wrpkt();
 362         memset(password, 0, strlen(password));
 363         get_packet();
 364         if (pktin.type == SSH_SMSG_FAILURE) {
 365             fprintf(stderr, "Access denied\n");
 366         } else if (pktin.type != SSH_SMSG_SUCCESS) {
 367             fatalbox("Strange packet received, type %d", pktin.type);
 368         }
 369     }
 370
 371     /* Execute command */
 372     if (verbose)
 373         fprintf(stderr, "Sending command: %s\n", cmd);
 374     i = strlen(cmd);
 375     s_wrpkt_start(SSH_CMSG_EXEC_CMD, 4+i);
 376     PUT_32BIT(pktout.body, i);
 377     memcpy(pktout.body+4, cmd, i);
 378     s_wrpkt();
 379 }
 380
 381
 382 /*
 383  * Receive a block of data over the SSH link. Block until
 384  * all data is available. Return nr of bytes read (0 if lost connection).
 385  */
 386 int ssh_recv(unsigned char *buf, int len)
 387 {
 388     static int pending_input_len = 0;
 389     static unsigned char *pending_input_ptr;
 390     int to_read = len;
 391
 392     if (pending_input_len >= to_read) {
 393         memcpy(buf, pending_input_ptr, to_read);
 394         pending_input_ptr += to_read;
 395         pending_input_len -= to_read;
 396         return len;
 397     }
 398
 399     if (pending_input_len > 0) {
 400         memcpy(buf, pending_input_ptr, pending_input_len);
 401         buf += pending_input_len;
 402         to_read -= pending_input_len;
 403         pending_input_len = 0;
 404     }
 405
 406     if (s == INVALID_SOCKET)
 407         return 0;
 408     while (to_read > 0) {
 409         get_packet();
 410         if (s == INVALID_SOCKET)
 411             return 0;
 412         if (pktin.type == SSH_SMSG_STDOUT_DATA) {
 413             int plen = GET_32BIT(pktin.body);
 414             if (plen <= to_read) {
 415                 memcpy(buf, pktin.body + 4, plen);
 416                 buf += plen;
 417                 to_read -= plen;
 418             } else {
 419                 memcpy(buf, pktin.body + 4, to_read);
 420                 pending_input_len = plen - to_read;
 421                 pending_input_ptr = pktin.body + 4 + to_read;
 422                 to_read = 0;
 423             }
 424         } else if (pktin.type == SSH_SMSG_STDERR_DATA) {
 425             int plen = GET_32BIT(pktin.body);
 426             fwrite(pktin.body + 4, plen, 1, stderr);
 427         } else if (pktin.type == SSH_MSG_DISCONNECT) {
 428         } else if (pktin.type == SSH_SMSG_SUCCESS ||
 429                    pktin.type == SSH_SMSG_FAILURE) {
 430         } else if (pktin.type == SSH_SMSG_EXIT_STATUS) {
 431             if (verbose)
 432                 fprintf(stderr, "Remote exit status %d\n",
 433                         GET_32BIT(pktin.body));
 434             s_wrpkt_start(SSH_CMSG_EXIT_CONFIRMATION, 0);
 435             s_wrpkt();
 436             if (verbose)
 437                 fprintf(stderr, "Closing connection\n");
 438             closesocket(s);
 439             s = INVALID_SOCKET;
 440         }
 441     }
 442
 443     return len;
 444 }
 445
 446
 447 /*
 448  * Send a block of data over the SSH link.
 449  * Block until all data is sent.
 450  */
 451 void ssh_send(unsigned char *buf, int len)
 452 {
 453     if (s == INVALID_SOCKET)
 454         return;
 455     s_wrpkt_start(SSH_CMSG_STDIN_DATA, 4 + len);
 456     PUT_32BIT(pktout.body, len);
 457     memcpy(pktout.body + 4, buf, len);
 458     s_wrpkt();
 459 }
 460
 461
 462 /*
 463  * Send an EOF notification to the server.
 464  */
 465 void ssh_send_eof(void)
 466 {
 467     if (s == INVALID_SOCKET)
 468         return;
 469     s_wrpkt_start(SSH_CMSG_EOF, 0);
 470     s_wrpkt();
 471 }
 472
 473
 474 /*
 475  * Set up the connection, login on the remote host and
 476  * start execution of a command.
 477  *
 478  * Returns an error message, or NULL on success.
 479  *
 480  * Also places the canonical host name into `realhost'.
 481  */
 482 char *ssh_init(char *host, int port, char *cmd, char **realhost) {
 483     SOCKADDR_IN addr;
 484     struct hostent *h;
 485     unsigned long a;
 486 #ifdef FWHACK
 487     char *FWhost;
 488     int FWport;
 489 #endif
 490
 491     savedhost = malloc(1+strlen(host));
 492     if (!savedhost)
 493         fatalbox("Out of memory");
 494     strcpy(savedhost, host);
 495
 496 #ifdef FWHACK
 497     FWhost = host;
 498     FWport = port;
 499     host = FWSTR;
 500     port = 23;
 501 #endif
 502
 503     /*
 504      * Try to find host.
 505      */
 506     if ( (a = inet_addr(host)) == (unsigned long) INADDR_NONE) {
 507         if ( (h = gethostbyname(host)) == NULL)
 508             switch (WSAGetLastError()) {
 509               case WSAENETDOWN: return "Network is down";
 510               case WSAHOST_NOT_FOUND: case WSANO_DATA:
 511                 return "Host does not exist";
 512               case WSATRY_AGAIN: return "Host not found";
 513               default: return "gethostbyname: unknown error";
 514             }
 515         memcpy (&a, h->h_addr, sizeof(a));
 516         *realhost = h->h_name;
 517     } else
 518         *realhost = host;
 519 #ifdef FWHACK
 520     *realhost = FWhost;
 521 #endif
 522     a = ntohl(a);
 523
 524     if (port < 0)
 525         port = 22;                     /* default ssh port */
 526
 527     /*
 528      * Open socket.
 529      */
 530     s = socket(AF_INET, SOCK_STREAM, 0);
 531     if (s == INVALID_SOCKET)
 532         switch (WSAGetLastError()) {
 533           case WSAENETDOWN: return "Network is down";
 534           case WSAEAFNOSUPPORT: return "TCP/IP support not present";
 535           default: return "socket(): unknown error";
 536         }
 537
 538     /*
 539      * Bind to local address.
 540      */
 541     addr.sin_family = AF_INET;
 542     addr.sin_addr.s_addr = htonl(INADDR_ANY);
 543     addr.sin_port = htons(0);
 544     if (bind (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 545         switch (WSAGetLastError()) {
 546           case WSAENETDOWN: return "Network is down";
 547           default: return "bind(): unknown error";
 548         }
 549
 550     /*
 551      * Connect to remote address.
 552      */
 553     addr.sin_addr.s_addr = htonl(a);
 554     addr.sin_port = htons((short)port);
 555     if (connect (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 556         switch (WSAGetLastError()) {
 557           case WSAENETDOWN: return "Network is down";
 558           case WSAECONNREFUSED: return "Connection refused";
 559           case WSAENETUNREACH: return "Network is unreachable";
 560           case WSAEHOSTUNREACH: return "No route to host";
 561           default: return "connect(): unknown error";
 562         }
 563
 564 #ifdef FWHACK
 565     send(s, "connect ", 8, 0);
 566     send(s, FWhost, strlen(FWhost), 0);
 567     {
 568         char buf[20];
 569         sprintf(buf, " %d\n", FWport);
 570         send (s, buf, strlen(buf), 0);
 571     }
 572 #endif
 573
 574     random_init();
 575
 576     if (!do_ssh_init())
 577         return "Protocol initialisation error";
 578
 579     ssh_login(cfg.username, cmd);
 580
 581     return NULL;
 582 }
 583
 584 /* end */