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     verify_ssh_host_key(savedhost, &hostkey);
 285
 286     for (i=0; i<32; i++) {
 287         rsabuf[i] = session_key[i];
 288         if (i < 16)
 289             rsabuf[i] ^= session_id[i];
 290     }
 291
 292     if (hostkey.bytes > servkey.bytes) {
 293         rsaencrypt(rsabuf, 32, &servkey);
 294         rsaencrypt(rsabuf, servkey.bytes, &hostkey);
 295     } else {
 296         rsaencrypt(rsabuf, 32, &hostkey);
 297         rsaencrypt(rsabuf, hostkey.bytes, &servkey);
 298     }
 299
 300     cipher_type = cfg.cipher == CIPHER_BLOWFISH ? SSH_CIPHER_BLOWFISH :
 301                   SSH_CIPHER_3DES;
 302     if ((supported_ciphers_mask & (1 << cipher_type)) == 0) {
 303         fprintf(stderr, "Selected cipher not supported, falling back to 3DES\n");
 304         cipher_type = SSH_CIPHER_3DES;
 305     }
 306
 307     s_wrpkt_start(SSH_CMSG_SESSION_KEY, len+15);
 308     pktout.body[0] = cipher_type;
 309     memcpy(pktout.body+1, cookie, 8);
 310     pktout.body[9] = (len*8) >> 8;
 311     pktout.body[10] = (len*8) & 0xFF;
 312     memcpy(pktout.body+11, rsabuf, len);
 313     pktout.body[len+11] = pktout.body[len+12] = 0;   /* protocol flags */
 314     pktout.body[len+13] = pktout.body[len+14] = 0;
 315     s_wrpkt();
 316
 317     free(rsabuf);
 318
 319     cipher = cipher_type == SSH_CIPHER_BLOWFISH ? &ssh_blowfish :
 320              &ssh_3des;
 321     cipher->sesskey(session_key);
 322
 323     get_packet();
 324
 325     if (pktin.type != SSH_SMSG_SUCCESS)
 326         fatalbox("Encryption not successfully enabled");
 327
 328     if (verbose)
 329         fprintf(stderr, "Logging in as \"%s\".\n", username);
 330     s_wrpkt_start(SSH_CMSG_USER, 4+strlen(username));
 331     pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 332     pktout.body[3] = strlen(username);
 333     memcpy(pktout.body+4, username, strlen(username));
 334     s_wrpkt();
 335
 336     get_packet();
 337
 338     while (pktin.type == SSH_SMSG_FAILURE) {
 339         char password[100];
 340         char prompt[200];
 341         sprintf(prompt, "%s@%s's password: ", username, savedhost);
 342         ssh_get_password(prompt, password, 100);
 343         s_wrpkt_start(SSH_CMSG_AUTH_PASSWORD, 4+strlen(password));
 344         pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 345         pktout.body[3] = strlen(password);
 346         memcpy(pktout.body+4, password, strlen(password));
 347         s_wrpkt();
 348         memset(password, 0, strlen(password));
 349         get_packet();
 350         if (pktin.type == SSH_SMSG_FAILURE) {
 351             fprintf(stderr, "Access denied\n");
 352         } else if (pktin.type != SSH_SMSG_SUCCESS) {
 353             fatalbox("Strange packet received, type %d", pktin.type);
 354         }
 355     }
 356
 357     /* Execute command */
 358     if (verbose)
 359         fprintf(stderr, "Sending command: %s\n", cmd);
 360     i = strlen(cmd);
 361     s_wrpkt_start(SSH_CMSG_EXEC_CMD, 4+i);
 362     PUT_32BIT(pktout.body, i);
 363     memcpy(pktout.body+4, cmd, i);
 364     s_wrpkt();
 365 }
 366
 367
 368 /*
 369  * Receive a block of data over the SSH link. Block until
 370  * all data is available. Return nr of bytes read (0 if lost connection).
 371  */
 372 int ssh_recv(unsigned char *buf, int len)
 373 {
 374     static int pending_input_len = 0;
 375     static unsigned char *pending_input_ptr;
 376     int to_read = len;
 377
 378     if (pending_input_len >= to_read) {
 379         memcpy(buf, pending_input_ptr, to_read);
 380         pending_input_ptr += to_read;
 381         pending_input_len -= to_read;
 382         return len;
 383     }
 384
 385     if (pending_input_len > 0) {
 386         memcpy(buf, pending_input_ptr, pending_input_len);
 387         buf += pending_input_len;
 388         to_read -= pending_input_len;
 389         pending_input_len = 0;
 390     }
 391
 392     if (s == INVALID_SOCKET)
 393         return 0;
 394     while (to_read > 0) {
 395         get_packet();
 396         if (s == INVALID_SOCKET)
 397             return 0;
 398         if (pktin.type == SSH_SMSG_STDOUT_DATA) {
 399             int plen = GET_32BIT(pktin.body);
 400             if (plen <= to_read) {
 401                 memcpy(buf, pktin.body + 4, plen);
 402                 buf += plen;
 403                 to_read -= plen;
 404             } else {
 405                 memcpy(buf, pktin.body + 4, to_read);
 406                 pending_input_len = plen - to_read;
 407                 pending_input_ptr = pktin.body + 4 + to_read;
 408                 to_read = 0;
 409             }
 410         } else if (pktin.type == SSH_SMSG_STDERR_DATA) {
 411             int plen = GET_32BIT(pktin.body);
 412             fwrite(pktin.body + 4, plen, 1, stderr);
 413         } else if (pktin.type == SSH_MSG_DISCONNECT) {
 414         } else if (pktin.type == SSH_SMSG_SUCCESS ||
 415                    pktin.type == SSH_SMSG_FAILURE) {
 416         } else if (pktin.type == SSH_SMSG_EXIT_STATUS) {
 417             if (verbose)
 418                 fprintf(stderr, "Remote exit status %d\n",
 419                         GET_32BIT(pktin.body));
 420             s_wrpkt_start(SSH_CMSG_EXIT_CONFIRMATION, 0);
 421             s_wrpkt();
 422             if (verbose)
 423                 fprintf(stderr, "Closing connection\n");
 424             closesocket(s);
 425             s = INVALID_SOCKET;
 426         }
 427     }
 428
 429     return len;
 430 }
 431
 432
 433 /*
 434  * Send a block of data over the SSH link.
 435  * Block until all data is sent.
 436  */
 437 void ssh_send(unsigned char *buf, int len)
 438 {
 439     if (s == INVALID_SOCKET)
 440         return;
 441     s_wrpkt_start(SSH_CMSG_STDIN_DATA, 4 + len);
 442     PUT_32BIT(pktout.body, len);
 443     memcpy(pktout.body + 4, buf, len);
 444     s_wrpkt();
 445 }
 446
 447
 448 /*
 449  * Send an EOF notification to the server.
 450  */
 451 void ssh_send_eof(void)
 452 {
 453     if (s == INVALID_SOCKET)
 454         return;
 455     s_wrpkt_start(SSH_CMSG_EOF, 0);
 456     s_wrpkt();
 457 }
 458
 459
 460 /*
 461  * Set up the connection, login on the remote host and
 462  * start execution of a command.
 463  *
 464  * Returns an error message, or NULL on success.
 465  *
 466  * Also places the canonical host name into `realhost'.
 467  */
 468 char *ssh_init(char *host, int port, char *cmd, char **realhost) {
 469     SOCKADDR_IN addr;
 470     struct hostent *h;
 471     unsigned long a;
 472 #ifdef FWHACK
 473     char *FWhost;
 474     int FWport;
 475 #endif
 476
 477     savedhost = malloc(1+strlen(host));
 478     if (!savedhost)
 479         fatalbox("Out of memory");
 480     strcpy(savedhost, host);
 481
 482 #ifdef FWHACK
 483     FWhost = host;
 484     FWport = port;
 485     host = FWSTR;
 486     port = 23;
 487 #endif
 488
 489     /*
 490      * Try to find host.
 491      */
 492     if ( (a = inet_addr(host)) == (unsigned long) INADDR_NONE) {
 493         if ( (h = gethostbyname(host)) == NULL)
 494             switch (WSAGetLastError()) {
 495               case WSAENETDOWN: return "Network is down";
 496               case WSAHOST_NOT_FOUND: case WSANO_DATA:
 497                 return "Host does not exist";
 498               case WSATRY_AGAIN: return "Host not found";
 499               default: return "gethostbyname: unknown error";
 500             }
 501         memcpy (&a, h->h_addr, sizeof(a));
 502         *realhost = h->h_name;
 503     } else
 504         *realhost = host;
 505 #ifdef FWHACK
 506     *realhost = FWhost;
 507 #endif
 508     a = ntohl(a);
 509
 510     if (port < 0)
 511         port = 22;                     /* default ssh port */
 512
 513     /*
 514      * Open socket.
 515      */
 516     s = socket(AF_INET, SOCK_STREAM, 0);
 517     if (s == INVALID_SOCKET)
 518         switch (WSAGetLastError()) {
 519           case WSAENETDOWN: return "Network is down";
 520           case WSAEAFNOSUPPORT: return "TCP/IP support not present";
 521           default: return "socket(): unknown error";
 522         }
 523
 524     /*
 525      * Bind to local address.
 526      */
 527     addr.sin_family = AF_INET;
 528     addr.sin_addr.s_addr = htonl(INADDR_ANY);
 529     addr.sin_port = htons(0);
 530     if (bind (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 531         switch (WSAGetLastError()) {
 532           case WSAENETDOWN: return "Network is down";
 533           default: return "bind(): unknown error";
 534         }
 535
 536     /*
 537      * Connect to remote address.
 538      */
 539     addr.sin_addr.s_addr = htonl(a);
 540     addr.sin_port = htons((short)port);
 541     if (connect (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 542         switch (WSAGetLastError()) {
 543           case WSAENETDOWN: return "Network is down";
 544           case WSAECONNREFUSED: return "Connection refused";
 545           case WSAENETUNREACH: return "Network is unreachable";
 546           case WSAEHOSTUNREACH: return "No route to host";
 547           default: return "connect(): unknown error";
 548         }
 549
 550 #ifdef FWHACK
 551     send(s, "connect ", 8, 0);
 552     send(s, FWhost, strlen(FWhost), 0);
 553     {
 554         char buf[20];
 555         sprintf(buf, " %d\n", FWport);
 556         send (s, buf, strlen(buf), 0);
 557     }
 558 #endif
 559
 560     random_init();
 561
 562     if (!do_ssh_init())
 563         return "Protocol initialisation error";
 564
 565     ssh_login(cfg.username, cmd);
 566
 567     return NULL;
 568 }
 569
 570 /* end */