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