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 #ifdef MSCRYPTOAPI
 125         /* allocate enough buffer space for extra block
 126          * for MS CryptEncrypt() */
 127         pktin.data = (pktin.data == NULL) ?
 128             smalloc(biglen+8) : srealloc(pktin.data, biglen+8);
 129 #else
 130         pktin.data = (pktin.data == NULL) ?
 131             smalloc(biglen) : srealloc(pktin.data, biglen);
 132 #endif
 133     }
 134
 135     ret = s_read(pktin.data, biglen);
 136     if (ret != biglen) {
 137         closesocket(s);
 138         s = INVALID_SOCKET;
 139         return;
 140     }
 141
 142     if (cipher)
 143         cipher->decrypt(pktin.data, biglen);
 144
 145     pktin.type = pktin.data[pad];
 146     pktin.body = pktin.data + pad + 1;
 147
 148     if (pktin.type == SSH_MSG_DEBUG) {
 149         if (verbose) {
 150             int len = GET_32BIT(pktin.body);
 151             fprintf(stderr, "Remote: ");
 152             fwrite(pktin.body + 4, len, 1, stderr);
 153             fprintf(stderr, "\n");
 154         }
 155         goto next_packet;
 156     }
 157     if (pktin.type == SSH_MSG_IGNORE) {
 158         goto next_packet;
 159     }
 160 }
 161
 162 static void s_wrpkt_start(int type, int len) {
 163     int pad, biglen;
 164
 165     len += 5;                          /* type and CRC */
 166     pad = 8 - (len%8);
 167     biglen = len + pad;
 168
 169     pktout.length = len-5;
 170     if (pktout.maxlen < biglen) {
 171         pktout.maxlen = biglen;
 172 #ifdef MSCRYPTOAPI
 173         /* Allocate enough buffer space for extra block
 174          * for MS CryptEncrypt() */
 175         pktout.data = (pktout.data == NULL ? malloc(biglen+8) :
 176                        realloc(pktout.data, biglen+8));
 177 #else
 178         pktout.data = (pktout.data == NULL ? malloc(biglen+4) :
 179                        realloc(pktout.data, biglen+4));
 180 #endif
 181         if (!pktout.data)
 182             fatalbox("Out of memory");
 183     }
 184
 185     pktout.type = type;
 186     pktout.body = pktout.data+4+pad+1;
 187 }
 188
 189 static void s_wrpkt(void) {
 190     int pad, len, biglen, i;
 191     unsigned long crc;
 192
 193     len = pktout.length + 5;           /* type and CRC */
 194     pad = 8 - (len%8);
 195     biglen = len + pad;
 196
 197     pktout.body[-1] = pktout.type;
 198     for (i=0; i<pad; i++)
 199         pktout.data[i+4] = random_byte();
 200     crc = crc32(pktout.data+4, biglen-4);
 201     PUT_32BIT(pktout.data+biglen, crc);
 202     PUT_32BIT(pktout.data, len);
 203
 204     if (cipher)
 205         cipher->encrypt(pktout.data+4, biglen);
 206
 207     s_write(pktout.data, biglen+4);
 208 }
 209
 210 static int do_ssh_init(void) {
 211     char c;
 212     char version[10];
 213     char vstring[40];
 214     int i;
 215
 216 #ifdef FWHACK
 217     i = 0;
 218     while (s_read(&c, 1) == 1) {
 219         if (c == 'S' && i < 2) i++;
 220         else if (c == 'S' && i == 2) i = 2;
 221         else if (c == 'H' && i == 2) break;
 222         else i = 0;
 223     }
 224 #else
 225     if (s_read(&c,1) != 1 || c != 'S') return 0;
 226     if (s_read(&c,1) != 1 || c != 'S') return 0;
 227     if (s_read(&c,1) != 1 || c != 'H') return 0;
 228 #endif
 229     if (s_read(&c,1) != 1 || c != '-') return 0;
 230     i = 0;
 231     while (1) {
 232         if (s_read(&c,1) != 1)
 233             return 0;
 234         if (i >= 0) {
 235             if (c == '-') {
 236                 version[i] = '\0';
 237                 i = -1;
 238             } else if (i < sizeof(version)-1)
 239                 version[i++] = c;
 240         }
 241         else if (c == '\n')
 242             break;
 243     }
 244
 245     sprintf(vstring, "SSH-%s-7.7.7\n",
 246             (strcmp(version, "1.5") <= 0 ? version : "1.5"));
 247     s_write(vstring, strlen(vstring));
 248     return 1;
 249 }
 250
 251
 252 /*
 253  * Login on the server and request execution of the command.
 254  */
 255 static void ssh_login(char *username, char *cmd)
 256 {
 257     int i, j, len;
 258     unsigned char session_id[16];
 259     unsigned char *rsabuf, *keystr1, *keystr2;
 260     unsigned char cookie[8];
 261     struct RSAKey servkey, hostkey;
 262     struct MD5Context md5c;
 263     unsigned long supported_ciphers_mask;
 264     int cipher_type;
 265
 266     extern struct ssh_cipher ssh_3des;
 267     extern struct ssh_cipher ssh_blowfish;
 268
 269     get_packet();
 270
 271     if (pktin.type != SSH_SMSG_PUBLIC_KEY)
 272         fatalbox("Public key packet not received");
 273
 274     memcpy(cookie, pktin.body, 8);
 275
 276     MD5Init(&md5c);
 277
 278     i = makekey(pktin.body+8, &servkey, &keystr1);
 279     j = makekey(pktin.body+8+i, &hostkey, &keystr2);
 280
 281     supported_ciphers_mask = GET_32BIT(pktin.body+12+i+j);
 282
 283     MD5Update(&md5c, keystr2, hostkey.bytes);
 284     MD5Update(&md5c, keystr1, servkey.bytes);
 285     MD5Update(&md5c, pktin.body, 8);
 286
 287     MD5Final(session_id, &md5c);
 288
 289     for (i=0; i<32; i++)
 290         session_key[i] = random_byte();
 291
 292     len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 293
 294     rsabuf = malloc(len);
 295     if (!rsabuf)
 296         fatalbox("Out of memory");
 297
 298     /*
 299      * Verify the host key.
 300      */
 301     {
 302         /*
 303          * First format the key into a string.
 304          */
 305         int len = rsastr_len(&hostkey);
 306         char *keystr = malloc(len);
 307         if (!keystr)
 308             fatalbox("Out of memory");
 309         rsastr_fmt(keystr, &hostkey);
 310         verify_ssh_host_key(savedhost, keystr);
 311         free(keystr);
 312     }
 313
 314     for (i=0; i<32; i++) {
 315         rsabuf[i] = session_key[i];
 316         if (i < 16)
 317             rsabuf[i] ^= session_id[i];
 318     }
 319
 320     if (hostkey.bytes > servkey.bytes) {
 321         rsaencrypt(rsabuf, 32, &servkey);
 322         rsaencrypt(rsabuf, servkey.bytes, &hostkey);
 323     } else {
 324         rsaencrypt(rsabuf, 32, &hostkey);
 325         rsaencrypt(rsabuf, hostkey.bytes, &servkey);
 326     }
 327
 328     cipher_type = cfg.cipher == CIPHER_BLOWFISH ? SSH_CIPHER_BLOWFISH :
 329                   SSH_CIPHER_3DES;
 330     if ((supported_ciphers_mask & (1 << cipher_type)) == 0) {
 331         fprintf(stderr, "Selected cipher not supported, falling back to 3DES\n");
 332         cipher_type = SSH_CIPHER_3DES;
 333     }
 334
 335     s_wrpkt_start(SSH_CMSG_SESSION_KEY, len+15);
 336     pktout.body[0] = cipher_type;
 337     memcpy(pktout.body+1, cookie, 8);
 338     pktout.body[9] = (len*8) >> 8;
 339     pktout.body[10] = (len*8) & 0xFF;
 340     memcpy(pktout.body+11, rsabuf, len);
 341     pktout.body[len+11] = pktout.body[len+12] = 0;   /* protocol flags */
 342     pktout.body[len+13] = pktout.body[len+14] = 0;
 343     s_wrpkt();
 344
 345     free(rsabuf);
 346
 347     cipher = cipher_type == SSH_CIPHER_BLOWFISH ? &ssh_blowfish :
 348              &ssh_3des;
 349     cipher->sesskey(session_key);
 350
 351     get_packet();
 352
 353     if (pktin.type != SSH_SMSG_SUCCESS)
 354         fatalbox("Encryption not successfully enabled");
 355
 356     if (verbose)
 357         fprintf(stderr, "Logging in as \"%s\".\n", username);
 358     s_wrpkt_start(SSH_CMSG_USER, 4+strlen(username));
 359     pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 360     pktout.body[3] = strlen(username);
 361     memcpy(pktout.body+4, username, strlen(username));
 362     s_wrpkt();
 363
 364     get_packet();
 365
 366     while (pktin.type == SSH_SMSG_FAILURE) {
 367         char password[100];
 368         char prompt[200];
 369         sprintf(prompt, "%s@%s's password: ", username, savedhost);
 370         ssh_get_password(prompt, password, 100);
 371         s_wrpkt_start(SSH_CMSG_AUTH_PASSWORD, 4+strlen(password));
 372         pktout.body[0] = pktout.body[1] = pktout.body[2] = 0;
 373         pktout.body[3] = strlen(password);
 374         memcpy(pktout.body+4, password, strlen(password));
 375         s_wrpkt();
 376         memset(password, 0, strlen(password));
 377         get_packet();
 378         if (pktin.type == SSH_SMSG_FAILURE) {
 379             fprintf(stderr, "Access denied\n");
 380         } else if (pktin.type != SSH_SMSG_SUCCESS) {
 381             fatalbox("Strange packet received, type %d", pktin.type);
 382         }
 383     }
 384
 385     /* Execute command */
 386     if (verbose)
 387         fprintf(stderr, "Sending command: %s\n", cmd);
 388     i = strlen(cmd);
 389     s_wrpkt_start(SSH_CMSG_EXEC_CMD, 4+i);
 390     PUT_32BIT(pktout.body, i);
 391     memcpy(pktout.body+4, cmd, i);
 392     s_wrpkt();
 393 }
 394
 395
 396 /*
 397  * Receive a block of data over the SSH link. Block until
 398  * all data is available. Return nr of bytes read (0 if lost connection).
 399  */
 400 int ssh_recv(unsigned char *buf, int len)
 401 {
 402     static int pending_input_len = 0;
 403     static unsigned char *pending_input_ptr;
 404     int to_read = len;
 405
 406     if (pending_input_len >= to_read) {
 407         memcpy(buf, pending_input_ptr, to_read);
 408         pending_input_ptr += to_read;
 409         pending_input_len -= to_read;
 410         return len;
 411     }
 412
 413     if (pending_input_len > 0) {
 414         memcpy(buf, pending_input_ptr, pending_input_len);
 415         buf += pending_input_len;
 416         to_read -= pending_input_len;
 417         pending_input_len = 0;
 418     }
 419
 420     if (s == INVALID_SOCKET)
 421         return 0;
 422     while (to_read > 0) {
 423         get_packet();
 424         if (s == INVALID_SOCKET)
 425             return 0;
 426         if (pktin.type == SSH_SMSG_STDOUT_DATA) {
 427             int plen = GET_32BIT(pktin.body);
 428             if (plen <= to_read) {
 429                 memcpy(buf, pktin.body + 4, plen);
 430                 buf += plen;
 431                 to_read -= plen;
 432             } else {
 433                 memcpy(buf, pktin.body + 4, to_read);
 434                 pending_input_len = plen - to_read;
 435                 pending_input_ptr = pktin.body + 4 + to_read;
 436                 to_read = 0;
 437             }
 438         } else if (pktin.type == SSH_SMSG_STDERR_DATA) {
 439             int plen = GET_32BIT(pktin.body);
 440             fwrite(pktin.body + 4, plen, 1, stderr);
 441         } else if (pktin.type == SSH_MSG_DISCONNECT) {
 442         } else if (pktin.type == SSH_SMSG_SUCCESS ||
 443                    pktin.type == SSH_SMSG_FAILURE) {
 444         } else if (pktin.type == SSH_SMSG_EXIT_STATUS) {
 445             if (verbose)
 446                 fprintf(stderr, "Remote exit status %d\n",
 447                         GET_32BIT(pktin.body));
 448             s_wrpkt_start(SSH_CMSG_EXIT_CONFIRMATION, 0);
 449             s_wrpkt();
 450             if (verbose)
 451                 fprintf(stderr, "Closing connection\n");
 452             closesocket(s);
 453             s = INVALID_SOCKET;
 454         }
 455     }
 456
 457     return len;
 458 }
 459
 460
 461 /*
 462  * Send a block of data over the SSH link.
 463  * Block until all data is sent.
 464  */
 465 void ssh_send(unsigned char *buf, int len)
 466 {
 467     if (s == INVALID_SOCKET)
 468         return;
 469     s_wrpkt_start(SSH_CMSG_STDIN_DATA, 4 + len);
 470     PUT_32BIT(pktout.body, len);
 471     memcpy(pktout.body + 4, buf, len);
 472     s_wrpkt();
 473 }
 474
 475
 476 /*
 477  * Send an EOF notification to the server.
 478  */
 479 void ssh_send_eof(void)
 480 {
 481     if (s == INVALID_SOCKET)
 482         return;
 483     s_wrpkt_start(SSH_CMSG_EOF, 0);
 484     s_wrpkt();
 485 }
 486
 487
 488 /*
 489  * Set up the connection, login on the remote host and
 490  * start execution of a command.
 491  *
 492  * Returns an error message, or NULL on success.
 493  *
 494  * Also places the canonical host name into `realhost'.
 495  */
 496 char *ssh_init(char *host, int port, char *cmd, char **realhost) {
 497     SOCKADDR_IN addr;
 498     struct hostent *h;
 499     unsigned long a;
 500 #ifdef FWHACK
 501     char *FWhost;
 502     int FWport;
 503 #endif
 504
 505 #ifdef MSCRYPTOAPI
 506     if(crypto_startup() == 0)
 507         return "Microsoft high encryption pack not installed!";
 508 #endif
 509
 510     savedhost = malloc(1+strlen(host));
 511     if (!savedhost)
 512         fatalbox("Out of memory");
 513     strcpy(savedhost, host);
 514
 515 #ifdef FWHACK
 516     FWhost = host;
 517     FWport = port;
 518     host = FWSTR;
 519     port = 23;
 520 #endif
 521
 522     /*
 523      * Try to find host.
 524      */
 525     if ( (a = inet_addr(host)) == (unsigned long) INADDR_NONE) {
 526         if ( (h = gethostbyname(host)) == NULL)
 527             switch (WSAGetLastError()) {
 528               case WSAENETDOWN: return "Network is down";
 529               case WSAHOST_NOT_FOUND: case WSANO_DATA:
 530                 return "Host does not exist";
 531               case WSATRY_AGAIN: return "Host not found";
 532               default: return "gethostbyname: unknown error";
 533             }
 534         memcpy (&a, h->h_addr, sizeof(a));
 535         *realhost = h->h_name;
 536     } else
 537         *realhost = host;
 538 #ifdef FWHACK
 539     *realhost = FWhost;
 540 #endif
 541     a = ntohl(a);
 542
 543     if (port < 0)
 544         port = 22;                     /* default ssh port */
 545
 546     /*
 547      * Open socket.
 548      */
 549     s = socket(AF_INET, SOCK_STREAM, 0);
 550     if (s == INVALID_SOCKET)
 551         switch (WSAGetLastError()) {
 552           case WSAENETDOWN: return "Network is down";
 553           case WSAEAFNOSUPPORT: return "TCP/IP support not present";
 554           default: return "socket(): unknown error";
 555         }
 556
 557     /*
 558      * Bind to local address.
 559      */
 560     addr.sin_family = AF_INET;
 561     addr.sin_addr.s_addr = htonl(INADDR_ANY);
 562     addr.sin_port = htons(0);
 563     if (bind (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 564         switch (WSAGetLastError()) {
 565           case WSAENETDOWN: return "Network is down";
 566           default: return "bind(): unknown error";
 567         }
 568
 569     /*
 570      * Connect to remote address.
 571      */
 572     addr.sin_addr.s_addr = htonl(a);
 573     addr.sin_port = htons((short)port);
 574     if (connect (s, (struct sockaddr *)&addr, sizeof(addr)) == SOCKET_ERROR)
 575         switch (WSAGetLastError()) {
 576           case WSAENETDOWN: return "Network is down";
 577           case WSAECONNREFUSED: return "Connection refused";
 578           case WSAENETUNREACH: return "Network is unreachable";
 579           case WSAEHOSTUNREACH: return "No route to host";
 580           default: return "connect(): unknown error";
 581         }
 582
 583 #ifdef FWHACK
 584     send(s, "connect ", 8, 0);
 585     send(s, FWhost, strlen(FWhost), 0);
 586     {
 587         char buf[20];
 588         sprintf(buf, " %d\n", FWport);
 589         send (s, buf, strlen(buf), 0);
 590     }
 591 #endif
 592
 593     random_init();
 594
 595     if (!do_ssh_init())
 596         return "Protocol initialisation error";
 597
 598     ssh_login(cfg.username, cmd);
 599
 600     return NULL;
 601 }
 602
 603 /* end */