packet.c

   1 /* $OpenBSD: packet.c,v 1.153 2008/05/19 06:14:02 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * This file contains code implementing the packet protocol and communication
   7  * with the other side.  This same code is used both on client and server side.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  *
  15  *
  16  * SSH2 packet format added by Markus Friedl.
  17  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  18  *
  19  * Redistribution and use in source and binary forms, with or without
  20  * modification, are permitted provided that the following conditions
  21  * are met:
  22  * 1. Redistributions of source code must retain the above copyright
  23  *    notice, this list of conditions and the following disclaimer.
  24  * 2. Redistributions in binary form must reproduce the above copyright
  25  *    notice, this list of conditions and the following disclaimer in the
  26  *    documentation and/or other materials provided with the distribution.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  29  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  30  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  31  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  32  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  33  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  34  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  35  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  36  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  37  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  38  */
  39
  40 #include "includes.h"
  41
  42 #include <sys/types.h>
  43 #include "openbsd-compat/sys-queue.h"
  44 #include <sys/param.h>
  45 #include <sys/socket.h>
  46 #ifdef HAVE_SYS_TIME_H
  47 # include <sys/time.h>
  48 #endif
  49
  50 #include <netinet/in.h>
  51 #include <netinet/ip.h>
  52 #include <arpa/inet.h>
  53
  54 #include <errno.h>
  55 #include <stdarg.h>
  56 #include <stdio.h>
  57 #include <stdlib.h>
  58 #include <string.h>
  59 #include <unistd.h>
  60 #include <signal.h>
  61
  62 #include "xmalloc.h"
  63 #include "buffer.h"
  64 #include "packet.h"
  65 #include "crc32.h"
  66 #include "compress.h"
  67 #include "deattack.h"
  68 #include "channels.h"
  69 #include "compat.h"
  70 #include "ssh1.h"
  71 #include "ssh2.h"
  72 #include "cipher.h"
  73 #include "key.h"
  74 #include "kex.h"
  75 #include "mac.h"
  76 #include "log.h"
  77 #include "canohost.h"
  78 #include "misc.h"
  79 #include "ssh.h"
  80
  81 #ifdef PACKET_DEBUG
  82 #define DBG(x) x
  83 #else
  84 #define DBG(x)
  85 #endif
  86
  87 /*
  88  * This variable contains the file descriptors used for communicating with
  89  * the other side.  connection_in is used for reading; connection_out for
  90  * writing.  These can be the same descriptor, in which case it is assumed to
  91  * be a socket.
  92  */
  93 static int connection_in = -1;
  94 static int connection_out = -1;
  95
  96 /* Protocol flags for the remote side. */
  97 static u_int remote_protocol_flags = 0;
  98
  99 /* Encryption context for receiving data.  This is only used for decryption. */
 100 static CipherContext receive_context;
 101
 102 /* Encryption context for sending data.  This is only used for encryption. */
 103 static CipherContext send_context;
 104
 105 /* Buffer for raw input data from the socket. */
 106 Buffer input;
 107
 108 /* Buffer for raw output data going to the socket. */
 109 Buffer output;
 110
 111 /* Buffer for the partial outgoing packet being constructed. */
 112 static Buffer outgoing_packet;
 113
 114 /* Buffer for the incoming packet currently being processed. */
 115 static Buffer incoming_packet;
 116
 117 /* Scratch buffer for packet compression/decompression. */
 118 static Buffer compression_buffer;
 119 static int compression_buffer_ready = 0;
 120
 121 /* Flag indicating whether packet compression/decompression is enabled. */
 122 static int packet_compression = 0;
 123
 124 /* default maximum packet size */
 125 u_int max_packet_size = 32768;
 126
 127 /* Flag indicating whether this module has been initialized. */
 128 static int initialized = 0;
 129
 130 /* Set to true if the connection is interactive. */
 131 static int interactive_mode = 0;
 132
 133 /* Set to true if we are the server side. */
 134 static int server_side = 0;
 135
 136 /* Set to true if we are authenticated. */
 137 static int after_authentication = 0;
 138
 139 int keep_alive_timeouts = 0;
 140
 141 /* Session key information for Encryption and MAC */
 142 Newkeys *newkeys[MODE_MAX];
 143 static struct packet_state {
 144         u_int32_t seqnr;
 145         u_int32_t packets;
 146         u_int64_t blocks;
 147 } p_read, p_send;
 148
 149 static u_int64_t max_blocks_in, max_blocks_out;
 150 static u_int32_t rekey_limit;
 151
 152 /* Session key for protocol v1 */
 153 static u_char ssh1_key[SSH_SESSION_KEY_LENGTH];
 154 static u_int ssh1_keylen;
 155
 156 /* roundup current message to extra_pad bytes */
 157 static u_char extra_pad = 0;
 158
 159 struct packet {
 160         TAILQ_ENTRY(packet) next;
 161         u_char type;
 162         Buffer payload;
 163 };
 164 TAILQ_HEAD(, packet) outgoing;
 165
 166 /*
 167  * Sets the descriptors used for communication.  Disables encryption until
 168  * packet_set_encryption_key is called.
 169  */
 170 void
 171 packet_set_connection(int fd_in, int fd_out)
 172 {
 173         Cipher *none = cipher_by_name("none");
 174
 175         if (none == NULL)
 176                 fatal("packet_set_connection: cannot load cipher 'none'");
 177         connection_in = fd_in;
 178         connection_out = fd_out;
 179         cipher_init(&send_context, none, (const u_char *)"",
 180             0, NULL, 0, CIPHER_ENCRYPT);
 181         cipher_init(&receive_context, none, (const u_char *)"",
 182             0, NULL, 0, CIPHER_DECRYPT);
 183         newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL;
 184         if (!initialized) {
 185                 initialized = 1;
 186                 buffer_init(&input);
 187                 buffer_init(&output);
 188                 buffer_init(&outgoing_packet);
 189                 buffer_init(&incoming_packet);
 190                 TAILQ_INIT(&outgoing);
 191         }
 192 }
 193
 194 /* Returns 1 if remote host is connected via socket, 0 if not. */
 195
 196 int
 197 packet_connection_is_on_socket(void)
 198 {
 199         struct sockaddr_storage from, to;
 200         socklen_t fromlen, tolen;
 201
 202         /* filedescriptors in and out are the same, so it's a socket */
 203         if (connection_in == connection_out)
 204                 return 1;
 205         fromlen = sizeof(from);
 206         memset(&from, 0, sizeof(from));
 207         if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0)
 208                 return 0;
 209         tolen = sizeof(to);
 210         memset(&to, 0, sizeof(to));
 211         if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0)
 212                 return 0;
 213         if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
 214                 return 0;
 215         if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
 216                 return 0;
 217         return 1;
 218 }
 219
 220 /*
 221  * Exports an IV from the CipherContext required to export the key
 222  * state back from the unprivileged child to the privileged parent
 223  * process.
 224  */
 225
 226 void
 227 packet_get_keyiv(int mode, u_char *iv, u_int len)
 228 {
 229         CipherContext *cc;
 230
 231         if (mode == MODE_OUT)
 232                 cc = &send_context;
 233         else
 234                 cc = &receive_context;
 235
 236         cipher_get_keyiv(cc, iv, len);
 237 }
 238
 239 int
 240 packet_get_keycontext(int mode, u_char *dat)
 241 {
 242         CipherContext *cc;
 243
 244         if (mode == MODE_OUT)
 245                 cc = &send_context;
 246         else
 247                 cc = &receive_context;
 248
 249         return (cipher_get_keycontext(cc, dat));
 250 }
 251
 252 void
 253 packet_set_keycontext(int mode, u_char *dat)
 254 {
 255         CipherContext *cc;
 256
 257         if (mode == MODE_OUT)
 258                 cc = &send_context;
 259         else
 260                 cc = &receive_context;
 261
 262         cipher_set_keycontext(cc, dat);
 263 }
 264
 265 int
 266 packet_get_keyiv_len(int mode)
 267 {
 268         CipherContext *cc;
 269
 270         if (mode == MODE_OUT)
 271                 cc = &send_context;
 272         else
 273                 cc = &receive_context;
 274
 275         return (cipher_get_keyiv_len(cc));
 276 }
 277
 278 void
 279 packet_set_iv(int mode, u_char *dat)
 280 {
 281         CipherContext *cc;
 282
 283         if (mode == MODE_OUT)
 284                 cc = &send_context;
 285         else
 286                 cc = &receive_context;
 287
 288         cipher_set_keyiv(cc, dat);
 289 }
 290
 291 int
 292 packet_get_ssh1_cipher(void)
 293 {
 294         return (cipher_get_number(receive_context.cipher));
 295 }
 296
 297 void
 298 packet_get_state(int mode, u_int32_t *seqnr, u_int64_t *blocks, u_int32_t *packets)
 299 {
 300         struct packet_state *state;
 301
 302         state = (mode == MODE_IN) ? &p_read : &p_send;
 303         *seqnr = state->seqnr;
 304         *blocks = state->blocks;
 305         *packets = state->packets;
 306 }
 307
 308 void
 309 packet_set_state(int mode, u_int32_t seqnr, u_int64_t blocks, u_int32_t packets)
 310 {
 311         struct packet_state *state;
 312
 313         state = (mode == MODE_IN) ? &p_read : &p_send;
 314         state->seqnr = seqnr;
 315         state->blocks = blocks;
 316         state->packets = packets;
 317 }
 318
 319 /* returns 1 if connection is via ipv4 */
 320
 321 int
 322 packet_connection_is_ipv4(void)
 323 {
 324         struct sockaddr_storage to;
 325         socklen_t tolen = sizeof(to);
 326
 327         memset(&to, 0, sizeof(to));
 328         if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
 329                 return 0;
 330         if (to.ss_family == AF_INET)
 331                 return 1;
 332 #ifdef IPV4_IN_IPV6
 333         if (to.ss_family == AF_INET6 &&
 334             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&to)->sin6_addr))
 335                 return 1;
 336 #endif
 337         return 0;
 338 }
 339
 340 /* Sets the connection into non-blocking mode. */
 341
 342 void
 343 packet_set_nonblocking(void)
 344 {
 345         /* Set the socket into non-blocking mode. */
 346         set_nonblock(connection_in);
 347
 348         if (connection_out != connection_in)
 349                 set_nonblock(connection_out);
 350 }
 351
 352 /* Returns the socket used for reading. */
 353
 354 int
 355 packet_get_connection_in(void)
 356 {
 357         return connection_in;
 358 }
 359
 360 /* Returns the descriptor used for writing. */
 361
 362 int
 363 packet_get_connection_out(void)
 364 {
 365         return connection_out;
 366 }
 367
 368 /* Closes the connection and clears and frees internal data structures. */
 369
 370 void
 371 packet_close(void)
 372 {
 373         if (!initialized)
 374                 return;
 375         initialized = 0;
 376         if (connection_in == connection_out) {
 377                 shutdown(connection_out, SHUT_RDWR);
 378                 close(connection_out);
 379         } else {
 380                 close(connection_in);
 381                 close(connection_out);
 382         }
 383         buffer_free(&input);
 384         buffer_free(&output);
 385         buffer_free(&outgoing_packet);
 386         buffer_free(&incoming_packet);
 387         if (compression_buffer_ready) {
 388                 buffer_free(&compression_buffer);
 389                 buffer_compress_uninit();
 390         }
 391         cipher_cleanup(&send_context);
 392         cipher_cleanup(&receive_context);
 393 }
 394
 395 /* Sets remote side protocol flags. */
 396
 397 void
 398 packet_set_protocol_flags(u_int protocol_flags)
 399 {
 400         remote_protocol_flags = protocol_flags;
 401 }
 402
 403 /* Returns the remote protocol flags set earlier by the above function. */
 404
 405 u_int
 406 packet_get_protocol_flags(void)
 407 {
 408         return remote_protocol_flags;
 409 }
 410
 411 /*
 412  * Starts packet compression from the next packet on in both directions.
 413  * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
 414  */
 415
 416 static void
 417 packet_init_compression(void)
 418 {
 419         if (compression_buffer_ready == 1)
 420                 return;
 421         compression_buffer_ready = 1;
 422         buffer_init(&compression_buffer);
 423 }
 424
 425 void
 426 packet_start_compression(int level)
 427 {
 428         if (packet_compression && !compat20)
 429                 fatal("Compression already enabled.");
 430         packet_compression = 1;
 431         packet_init_compression();
 432         buffer_compress_init_send(level);
 433         buffer_compress_init_recv();
 434 }
 435
 436 /*
 437  * Causes any further packets to be encrypted using the given key.  The same
 438  * key is used for both sending and reception.  However, both directions are
 439  * encrypted independently of each other.
 440  */
 441
 442 void
 443 packet_set_encryption_key(const u_char *key, u_int keylen,
 444     int number)
 445 {
 446         Cipher *cipher = cipher_by_number(number);
 447
 448         if (cipher == NULL)
 449                 fatal("packet_set_encryption_key: unknown cipher number %d", number);
 450         if (keylen < 20)
 451                 fatal("packet_set_encryption_key: keylen too small: %d", keylen);
 452         if (keylen > SSH_SESSION_KEY_LENGTH)
 453                 fatal("packet_set_encryption_key: keylen too big: %d", keylen);
 454         memcpy(ssh1_key, key, keylen);
 455         ssh1_keylen = keylen;
 456         cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT);
 457         cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT);
 458 }
 459
 460 u_int
 461 packet_get_encryption_key(u_char *key)
 462 {
 463         if (key == NULL)
 464                 return (ssh1_keylen);
 465         memcpy(key, ssh1_key, ssh1_keylen);
 466         return (ssh1_keylen);
 467 }
 468
 469 /* Start constructing a packet to send. */
 470 void
 471 packet_start(u_char type)
 472 {
 473         u_char buf[9];
 474         int len;
 475
 476         DBG(debug("packet_start[%d]", type));
 477         len = compat20 ? 6 : 9;
 478         memset(buf, 0, len - 1);
 479         buf[len - 1] = type;
 480         buffer_clear(&outgoing_packet);
 481         buffer_append(&outgoing_packet, buf, len);
 482 }
 483
 484 /* Append payload. */
 485 void
 486 packet_put_char(int value)
 487 {
 488         char ch = value;
 489
 490         buffer_append(&outgoing_packet, &ch, 1);
 491 }
 492
 493 void
 494 packet_put_int(u_int value)
 495 {
 496         buffer_put_int(&outgoing_packet, value);
 497 }
 498
 499 void
 500 packet_put_string(const void *buf, u_int len)
 501 {
 502         buffer_put_string(&outgoing_packet, buf, len);
 503 }
 504
 505 void
 506 packet_put_cstring(const char *str)
 507 {
 508         buffer_put_cstring(&outgoing_packet, str);
 509 }
 510
 511 void
 512 packet_put_raw(const void *buf, u_int len)
 513 {
 514         buffer_append(&outgoing_packet, buf, len);
 515 }
 516
 517 void
 518 packet_put_bignum(BIGNUM * value)
 519 {
 520         buffer_put_bignum(&outgoing_packet, value);
 521 }
 522
 523 void
 524 packet_put_bignum2(BIGNUM * value)
 525 {
 526         buffer_put_bignum2(&outgoing_packet, value);
 527 }
 528
 529 /*
 530  * Finalizes and sends the packet.  If the encryption key has been set,
 531  * encrypts the packet before sending.
 532  */
 533
 534 static void
 535 packet_send1(void)
 536 {
 537         u_char buf[8], *cp;
 538         int i, padding, len;
 539         u_int checksum;
 540         u_int32_t rnd = 0;
 541
 542         /*
 543          * If using packet compression, compress the payload of the outgoing
 544          * packet.
 545          */
 546         if (packet_compression) {
 547                 buffer_clear(&compression_buffer);
 548                 /* Skip padding. */
 549                 buffer_consume(&outgoing_packet, 8);
 550                 /* padding */
 551                 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
 552                 buffer_compress(&outgoing_packet, &compression_buffer);
 553                 buffer_clear(&outgoing_packet);
 554                 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
 555                     buffer_len(&compression_buffer));
 556         }
 557         /* Compute packet length without padding (add checksum, remove padding). */
 558         len = buffer_len(&outgoing_packet) + 4 - 8;
 559
 560         /* Insert padding. Initialized to zero in packet_start1() */
 561         padding = 8 - len % 8;
 562         if (!send_context.plaintext) {
 563                 cp = buffer_ptr(&outgoing_packet);
 564                 for (i = 0; i < padding; i++) {
 565                         if (i % 4 == 0)
 566                                 rnd = arc4random();
 567                         cp[7 - i] = rnd & 0xff;
 568                         rnd >>= 8;
 569                 }
 570         }
 571         buffer_consume(&outgoing_packet, 8 - padding);
 572
 573         /* Add check bytes. */
 574         checksum = ssh_crc32(buffer_ptr(&outgoing_packet),
 575             buffer_len(&outgoing_packet));
 576         put_u32(buf, checksum);
 577         buffer_append(&outgoing_packet, buf, 4);
 578
 579 #ifdef PACKET_DEBUG
 580         fprintf(stderr, "packet_send plain: ");
 581         buffer_dump(&outgoing_packet);
 582 #endif
 583
 584         /* Append to output. */
 585         put_u32(buf, len);
 586         buffer_append(&output, buf, 4);
 587         cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
 588         cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
 589             buffer_len(&outgoing_packet));
 590
 591 #ifdef PACKET_DEBUG
 592         fprintf(stderr, "encrypted: ");
 593         buffer_dump(&output);
 594 #endif
 595
 596         buffer_clear(&outgoing_packet);
 597
 598         /*
 599          * Note that the packet is now only buffered in output.  It won't be
 600          * actually sent until packet_write_wait or packet_write_poll is
 601          * called.
 602          */
 603 }
 604
 605 void
 606 set_newkeys(int mode)
 607 {
 608         Enc *enc;
 609         Mac *mac;
 610         Comp *comp;
 611         CipherContext *cc;
 612         u_int64_t *max_blocks;
 613         int crypt_type;
 614
 615         debug2("set_newkeys: mode %d", mode);
 616
 617         if (mode == MODE_OUT) {
 618                 cc = &send_context;
 619                 crypt_type = CIPHER_ENCRYPT;
 620                 p_send.packets = p_send.blocks = 0;
 621                 max_blocks = &max_blocks_out;
 622         } else {
 623                 cc = &receive_context;
 624                 crypt_type = CIPHER_DECRYPT;
 625                 p_read.packets = p_read.blocks = 0;
 626                 max_blocks = &max_blocks_in;
 627         }
 628         if (newkeys[mode] != NULL) {
 629                 debug("set_newkeys: rekeying");
 630                 cipher_cleanup(cc);
 631                 enc  = &newkeys[mode]->enc;
 632                 mac  = &newkeys[mode]->mac;
 633                 comp = &newkeys[mode]->comp;
 634                 mac_clear(mac);
 635                 xfree(enc->name);
 636                 xfree(enc->iv);
 637                 xfree(enc->key);
 638                 xfree(mac->name);
 639                 xfree(mac->key);
 640                 xfree(comp->name);
 641                 xfree(newkeys[mode]);
 642         }
 643         newkeys[mode] = kex_get_newkeys(mode);
 644         if (newkeys[mode] == NULL)
 645                 fatal("newkeys: no keys for mode %d", mode);
 646         enc  = &newkeys[mode]->enc;
 647         mac  = &newkeys[mode]->mac;
 648         comp = &newkeys[mode]->comp;
 649         if (mac_init(mac) == 0)
 650                 mac->enabled = 1;
 651         DBG(debug("cipher_init_context: %d", mode));
 652         cipher_init(cc, enc->cipher, enc->key, enc->key_len,
 653             enc->iv, enc->block_size, crypt_type);
 654         /* Deleting the keys does not gain extra security */
 655         /* memset(enc->iv,  0, enc->block_size);
 656            memset(enc->key, 0, enc->key_len);
 657            memset(mac->key, 0, mac->key_len); */
 658         if ((comp->type == COMP_ZLIB ||
 659             (comp->type == COMP_DELAYED && after_authentication)) &&
 660             comp->enabled == 0) {
 661                 packet_init_compression();
 662                 if (mode == MODE_OUT)
 663                         buffer_compress_init_send(6);
 664                 else
 665                         buffer_compress_init_recv();
 666                 comp->enabled = 1;
 667         }
 668         /*
 669          * The 2^(blocksize*2) limit is too expensive for 3DES,
 670          * blowfish, etc, so enforce a 1GB limit for small blocksizes.
 671          */
 672         if (enc->block_size >= 16)
 673                 *max_blocks = (u_int64_t)1 << (enc->block_size*2);
 674         else
 675                 *max_blocks = ((u_int64_t)1 << 30) / enc->block_size;
 676         if (rekey_limit)
 677                 *max_blocks = MIN(*max_blocks, rekey_limit / enc->block_size);
 678 }
 679
 680 /*
 681  * Delayed compression for SSH2 is enabled after authentication:
 682  * This happens on the server side after a SSH2_MSG_USERAUTH_SUCCESS is sent,
 683  * and on the client side after a SSH2_MSG_USERAUTH_SUCCESS is received.
 684  */
 685 static void
 686 packet_enable_delayed_compress(void)
 687 {
 688         Comp *comp = NULL;
 689         int mode;
 690
 691         /*
 692          * Remember that we are past the authentication step, so rekeying
 693          * with COMP_DELAYED will turn on compression immediately.
 694          */
 695         after_authentication = 1;
 696         for (mode = 0; mode < MODE_MAX; mode++) {
 697                 /* protocol error: USERAUTH_SUCCESS received before NEWKEYS */
 698                 if (newkeys[mode] == NULL)
 699                         continue;
 700                 comp = &newkeys[mode]->comp;
 701                 if (comp && !comp->enabled && comp->type == COMP_DELAYED) {
 702                         packet_init_compression();
 703                         if (mode == MODE_OUT)
 704                                 buffer_compress_init_send(6);
 705                         else
 706                                 buffer_compress_init_recv();
 707                         comp->enabled = 1;
 708                 }
 709         }
 710 }
 711
 712 /*
 713  * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
 714  */
 715 static void
 716 packet_send2_wrapped(void)
 717 {
 718         u_char type, *cp, *macbuf = NULL;
 719         u_char padlen, pad;
 720         u_int packet_length = 0;
 721         u_int i, len;
 722         u_int32_t rnd = 0;
 723         Enc *enc   = NULL;
 724         Mac *mac   = NULL;
 725         Comp *comp = NULL;
 726         int block_size;
 727
 728         if (newkeys[MODE_OUT] != NULL) {
 729                 enc  = &newkeys[MODE_OUT]->enc;
 730                 mac  = &newkeys[MODE_OUT]->mac;
 731                 comp = &newkeys[MODE_OUT]->comp;
 732         }
 733         block_size = enc ? enc->block_size : 8;
 734
 735         cp = buffer_ptr(&outgoing_packet);
 736         type = cp[5];
 737
 738 #ifdef PACKET_DEBUG
 739         fprintf(stderr, "plain:     ");
 740         buffer_dump(&outgoing_packet);
 741 #endif
 742
 743         if (comp && comp->enabled) {
 744                 len = buffer_len(&outgoing_packet);
 745                 /* skip header, compress only payload */
 746                 buffer_consume(&outgoing_packet, 5);
 747                 buffer_clear(&compression_buffer);
 748                 buffer_compress(&outgoing_packet, &compression_buffer);
 749                 buffer_clear(&outgoing_packet);
 750                 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5);
 751                 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
 752                     buffer_len(&compression_buffer));
 753                 DBG(debug("compression: raw %d compressed %d", len,
 754                     buffer_len(&outgoing_packet)));
 755         }
 756
 757         /* sizeof (packet_len + pad_len + payload) */
 758         len = buffer_len(&outgoing_packet);
 759
 760         /*
 761          * calc size of padding, alloc space, get random data,
 762          * minimum padding is 4 bytes
 763          */
 764         padlen = block_size - (len % block_size);
 765         if (padlen < 4)
 766                 padlen += block_size;
 767         if (extra_pad) {
 768                 /* will wrap if extra_pad+padlen > 255 */
 769                 extra_pad  = roundup(extra_pad, block_size);
 770                 pad = extra_pad - ((len + padlen) % extra_pad);
 771                 debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)",
 772                     pad, len, padlen, extra_pad);
 773                 padlen += pad;
 774                 extra_pad = 0;
 775         }
 776         cp = buffer_append_space(&outgoing_packet, padlen);
 777         if (enc && !send_context.plaintext) {
 778                 /* random padding */
 779                 for (i = 0; i < padlen; i++) {
 780                         if (i % 4 == 0)
 781                                 rnd = arc4random();
 782                         cp[i] = rnd & 0xff;
 783                         rnd >>= 8;
 784                 }
 785         } else {
 786                 /* clear padding */
 787                 memset(cp, 0, padlen);
 788         }
 789         /* packet_length includes payload, padding and padding length field */
 790         packet_length = buffer_len(&outgoing_packet) - 4;
 791         cp = buffer_ptr(&outgoing_packet);
 792         put_u32(cp, packet_length);
 793         cp[4] = padlen;
 794         DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
 795
 796         /* compute MAC over seqnr and packet(length fields, payload, padding) */
 797         if (mac && mac->enabled) {
 798                 macbuf = mac_compute(mac, p_send.seqnr,
 799                     buffer_ptr(&outgoing_packet),
 800                     buffer_len(&outgoing_packet));
 801                 DBG(debug("done calc MAC out #%d", p_send.seqnr));
 802         }
 803         /* encrypt packet and append to output buffer. */
 804         cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
 805         cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
 806             buffer_len(&outgoing_packet));
 807         /* append unencrypted MAC */
 808         if (mac && mac->enabled)
 809                 buffer_append(&output, macbuf, mac->mac_len);
 810 #ifdef PACKET_DEBUG
 811         fprintf(stderr, "encrypted: ");
 812         buffer_dump(&output);
 813 #endif
 814         /* increment sequence number for outgoing packets */
 815         if (++p_send.seqnr == 0)
 816                 logit("outgoing seqnr wraps around");
 817         if (++p_send.packets == 0)
 818                 if (!(datafellows & SSH_BUG_NOREKEY))
 819                         fatal("XXX too many packets with same key");
 820         p_send.blocks += (packet_length + 4) / block_size;
 821         buffer_clear(&outgoing_packet);
 822
 823         if (type == SSH2_MSG_NEWKEYS)
 824                 set_newkeys(MODE_OUT);
 825         else if (type == SSH2_MSG_USERAUTH_SUCCESS && server_side)
 826                 packet_enable_delayed_compress();
 827 }
 828
 829 static void
 830 packet_send2(void)
 831 {
 832         static int rekeying = 0;
 833         struct packet *p;
 834         u_char type, *cp;
 835
 836         cp = buffer_ptr(&outgoing_packet);
 837         type = cp[5];
 838
 839         /* during rekeying we can only send key exchange messages */
 840         if (rekeying) {
 841                 if (!((type >= SSH2_MSG_TRANSPORT_MIN) &&
 842                     (type <= SSH2_MSG_TRANSPORT_MAX))) {
 843                         debug("enqueue packet: %u", type);
 844                         p = xmalloc(sizeof(*p));
 845                         p->type = type;
 846                         memcpy(&p->payload, &outgoing_packet, sizeof(Buffer));
 847                         buffer_init(&outgoing_packet);
 848                         TAILQ_INSERT_TAIL(&outgoing, p, next);
 849                         return;
 850                 }
 851         }
 852
 853         /* rekeying starts with sending KEXINIT */
 854         if (type == SSH2_MSG_KEXINIT)
 855                 rekeying = 1;
 856
 857         packet_send2_wrapped();
 858
 859         /* after a NEWKEYS message we can send the complete queue */
 860         if (type == SSH2_MSG_NEWKEYS) {
 861                 rekeying = 0;
 862                 while ((p = TAILQ_FIRST(&outgoing))) {
 863                         type = p->type;
 864                         debug("dequeue packet: %u", type);
 865                         buffer_free(&outgoing_packet);
 866                         memcpy(&outgoing_packet, &p->payload,
 867                             sizeof(Buffer));
 868                         TAILQ_REMOVE(&outgoing, p, next);
 869                         xfree(p);
 870                         packet_send2_wrapped();
 871                 }
 872         }
 873 }
 874
 875 void
 876 packet_send(void)
 877 {
 878         if (compat20)
 879                 packet_send2();
 880         else
 881                 packet_send1();
 882         DBG(debug("packet_send done"));
 883 }
 884
 885 /*
 886  * Waits until a packet has been received, and returns its type.  Note that
 887  * no other data is processed until this returns, so this function should not
 888  * be used during the interactive session.
 889  */
 890
 891 int
 892 packet_read_seqnr(u_int32_t *seqnr_p)
 893 {
 894         int type, len;
 895         fd_set *setp;
 896         char buf[8192];
 897         DBG(debug("packet_read()"));
 898
 899         setp = (fd_set *)xcalloc(howmany(connection_in+1, NFDBITS),
 900             sizeof(fd_mask));
 901
 902         /* Since we are blocking, ensure that all written packets have been sent. */
 903         packet_write_wait();
 904
 905         /* Stay in the loop until we have received a complete packet. */
 906         for (;;) {
 907                 /* Try to read a packet from the buffer. */
 908                 type = packet_read_poll_seqnr(seqnr_p);
 909                 if (!compat20 && (
 910                     type == SSH_SMSG_SUCCESS
 911                     || type == SSH_SMSG_FAILURE
 912                     || type == SSH_CMSG_EOF
 913                     || type == SSH_CMSG_EXIT_CONFIRMATION))
 914                         packet_check_eom();
 915                 /* If we got a packet, return it. */
 916                 if (type != SSH_MSG_NONE) {
 917                         xfree(setp);
 918                         return type;
 919                 }
 920                 /*
 921                  * Otherwise, wait for some data to arrive, add it to the
 922                  * buffer, and try again.
 923                  */
 924                 memset(setp, 0, howmany(connection_in + 1, NFDBITS) *
 925                     sizeof(fd_mask));
 926                 FD_SET(connection_in, setp);
 927
 928                 /* Wait for some data to arrive. */
 929                 while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 &&
 930                     (errno == EAGAIN || errno == EINTR))
 931                         ;
 932
 933                 /* Read data from the socket. */
 934                 len = read(connection_in, buf, sizeof(buf));
 935                 if (len == 0) {
 936                         logit("Connection closed by %.200s", get_remote_ipaddr());
 937                         cleanup_exit(255);
 938                 }
 939                 if (len < 0)
 940                         fatal("Read from socket failed: %.100s", strerror(errno));
 941                 /* Append it to the buffer. */
 942                 packet_process_incoming(buf, len);
 943         }
 944         /* NOTREACHED */
 945 }
 946
 947 int
 948 packet_read(void)
 949 {
 950         return packet_read_seqnr(NULL);
 951 }
 952
 953 /*
 954  * Waits until a packet has been received, verifies that its type matches
 955  * that given, and gives a fatal error and exits if there is a mismatch.
 956  */
 957
 958 void
 959 packet_read_expect(int expected_type)
 960 {
 961         int type;
 962
 963         type = packet_read();
 964         if (type != expected_type)
 965                 packet_disconnect("Protocol error: expected packet type %d, got %d",
 966                     expected_type, type);
 967 }
 968
 969 /* Checks if a full packet is available in the data received so far via
 970  * packet_process_incoming.  If so, reads the packet; otherwise returns
 971  * SSH_MSG_NONE.  This does not wait for data from the connection.
 972  *
 973  * SSH_MSG_DISCONNECT is handled specially here.  Also,
 974  * SSH_MSG_IGNORE messages are skipped by this function and are never returned
 975  * to higher levels.
 976  */
 977
 978 static int
 979 packet_read_poll1(void)
 980 {
 981         u_int len, padded_len;
 982         u_char *cp, type;
 983         u_int checksum, stored_checksum;
 984
 985         /* Check if input size is less than minimum packet size. */
 986         if (buffer_len(&input) < 4 + 8)
 987                 return SSH_MSG_NONE;
 988         /* Get length of incoming packet. */
 989         cp = buffer_ptr(&input);
 990         len = get_u32(cp);
 991         if (len < 1 + 2 + 2 || len > 256 * 1024)
 992                 packet_disconnect("Bad packet length %u.", len);
 993         padded_len = (len + 8) & ~7;
 994
 995         /* Check if the packet has been entirely received. */
 996         if (buffer_len(&input) < 4 + padded_len)
 997                 return SSH_MSG_NONE;
 998
 999         /* The entire packet is in buffer. */
1000
1001         /* Consume packet length. */
1002         buffer_consume(&input, 4);
1003
1004         /*
1005          * Cryptographic attack detector for ssh
1006          * (C)1998 CORE-SDI, Buenos Aires Argentina
1007          * Ariel Futoransky(futo@core-sdi.com)
1008          */
1009         if (!receive_context.plaintext) {
1010                 switch (detect_attack(buffer_ptr(&input), padded_len)) {
1011                 case DEATTACK_DETECTED:
1012                         packet_disconnect("crc32 compensation attack: "
1013                             "network attack detected");
1014                 case DEATTACK_DOS_DETECTED:
1015                         packet_disconnect("deattack denial of "
1016                             "service detected");
1017                 }
1018         }
1019
1020         /* Decrypt data to incoming_packet. */
1021         buffer_clear(&incoming_packet);
1022         cp = buffer_append_space(&incoming_packet, padded_len);
1023         cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len);
1024
1025         buffer_consume(&input, padded_len);
1026
1027 #ifdef PACKET_DEBUG
1028         fprintf(stderr, "read_poll plain: ");
1029         buffer_dump(&incoming_packet);
1030 #endif
1031
1032         /* Compute packet checksum. */
1033         checksum = ssh_crc32(buffer_ptr(&incoming_packet),
1034             buffer_len(&incoming_packet) - 4);
1035
1036         /* Skip padding. */
1037         buffer_consume(&incoming_packet, 8 - len % 8);
1038
1039         /* Test check bytes. */
1040         if (len != buffer_len(&incoming_packet))
1041                 packet_disconnect("packet_read_poll1: len %d != buffer_len %d.",
1042                     len, buffer_len(&incoming_packet));
1043
1044         cp = (u_char *)buffer_ptr(&incoming_packet) + len - 4;
1045         stored_checksum = get_u32(cp);
1046         if (checksum != stored_checksum)
1047                 packet_disconnect("Corrupted check bytes on input.");
1048         buffer_consume_end(&incoming_packet, 4);
1049
1050         if (packet_compression) {
1051                 buffer_clear(&compression_buffer);
1052                 buffer_uncompress(&incoming_packet, &compression_buffer);
1053                 buffer_clear(&incoming_packet);
1054                 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1055                     buffer_len(&compression_buffer));
1056         }
1057         type = buffer_get_char(&incoming_packet);
1058         if (type < SSH_MSG_MIN || type > SSH_MSG_MAX)
1059                 packet_disconnect("Invalid ssh1 packet type: %d", type);
1060         return type;
1061 }
1062
1063 static int
1064 packet_read_poll2(u_int32_t *seqnr_p)
1065 {
1066         static u_int packet_length = 0;
1067         u_int padlen, need;
1068         u_char *macbuf, *cp, type;
1069         u_int maclen, block_size;
1070         Enc *enc   = NULL;
1071         Mac *mac   = NULL;
1072         Comp *comp = NULL;
1073
1074         if (newkeys[MODE_IN] != NULL) {
1075                 enc  = &newkeys[MODE_IN]->enc;
1076                 mac  = &newkeys[MODE_IN]->mac;
1077                 comp = &newkeys[MODE_IN]->comp;
1078         }
1079         maclen = mac && mac->enabled ? mac->mac_len : 0;
1080         block_size = enc ? enc->block_size : 8;
1081
1082         if (packet_length == 0) {
1083                 /*
1084                  * check if input size is less than the cipher block size,
1085                  * decrypt first block and extract length of incoming packet
1086                  */
1087                 if (buffer_len(&input) < block_size)
1088                         return SSH_MSG_NONE;
1089                 buffer_clear(&incoming_packet);
1090                 cp = buffer_append_space(&incoming_packet, block_size);
1091                 cipher_crypt(&receive_context, cp, buffer_ptr(&input),
1092                     block_size);
1093                 cp = buffer_ptr(&incoming_packet);
1094                 packet_length = get_u32(cp);
1095                 if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
1096 #ifdef PACKET_DEBUG
1097                         buffer_dump(&incoming_packet);
1098 #endif
1099                         packet_disconnect("Bad packet length %u.", packet_length);
1100                 }
1101                 DBG(debug("input: packet len %u", packet_length+4));
1102                 buffer_consume(&input, block_size);
1103         }
1104         /* we have a partial packet of block_size bytes */
1105         need = 4 + packet_length - block_size;
1106         DBG(debug("partial packet %d, need %d, maclen %d", block_size,
1107             need, maclen));
1108         if (need % block_size != 0)
1109                 fatal("padding error: need %d block %d mod %d",
1110                     need, block_size, need % block_size);
1111         /*
1112          * check if the entire packet has been received and
1113          * decrypt into incoming_packet
1114          */
1115         if (buffer_len(&input) < need + maclen)
1116                 return SSH_MSG_NONE;
1117 #ifdef PACKET_DEBUG
1118         fprintf(stderr, "read_poll enc/full: ");
1119         buffer_dump(&input);
1120 #endif
1121         cp = buffer_append_space(&incoming_packet, need);
1122         cipher_crypt(&receive_context, cp, buffer_ptr(&input), need);
1123         buffer_consume(&input, need);
1124         /*
1125          * compute MAC over seqnr and packet,
1126          * increment sequence number for incoming packet
1127          */
1128         if (mac && mac->enabled) {
1129                 macbuf = mac_compute(mac, p_read.seqnr,
1130                     buffer_ptr(&incoming_packet),
1131                     buffer_len(&incoming_packet));
1132                 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
1133                         packet_disconnect("Corrupted MAC on input.");
1134                 DBG(debug("MAC #%d ok", p_read.seqnr));
1135                 buffer_consume(&input, mac->mac_len);
1136         }
1137         if (seqnr_p != NULL)
1138                 *seqnr_p = p_read.seqnr;
1139         if (++p_read.seqnr == 0)
1140                 logit("incoming seqnr wraps around");
1141         if (++p_read.packets == 0)
1142                 if (!(datafellows & SSH_BUG_NOREKEY))
1143                         fatal("XXX too many packets with same key");
1144         p_read.blocks += (packet_length + 4) / block_size;
1145
1146         /* get padlen */
1147         cp = buffer_ptr(&incoming_packet);
1148         padlen = cp[4];
1149         DBG(debug("input: padlen %d", padlen));
1150         if (padlen < 4)
1151                 packet_disconnect("Corrupted padlen %d on input.", padlen);
1152
1153         /* skip packet size + padlen, discard padding */
1154         buffer_consume(&incoming_packet, 4 + 1);
1155         buffer_consume_end(&incoming_packet, padlen);
1156
1157         DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet)));
1158         if (comp && comp->enabled) {
1159                 buffer_clear(&compression_buffer);
1160                 buffer_uncompress(&incoming_packet, &compression_buffer);
1161                 buffer_clear(&incoming_packet);
1162                 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1163                     buffer_len(&compression_buffer));
1164                 DBG(debug("input: len after de-compress %d",
1165                     buffer_len(&incoming_packet)));
1166         }
1167         /*
1168          * get packet type, implies consume.
1169          * return length of payload (without type field)
1170          */
1171         type = buffer_get_char(&incoming_packet);
1172         if (type < SSH2_MSG_MIN || type >= SSH2_MSG_LOCAL_MIN)
1173                 packet_disconnect("Invalid ssh2 packet type: %d", type);
1174         if (type == SSH2_MSG_NEWKEYS)
1175                 set_newkeys(MODE_IN);
1176         else if (type == SSH2_MSG_USERAUTH_SUCCESS && !server_side)
1177                 packet_enable_delayed_compress();
1178 #ifdef PACKET_DEBUG
1179         fprintf(stderr, "read/plain[%d]:\r\n", type);
1180         buffer_dump(&incoming_packet);
1181 #endif
1182         /* reset for next packet */
1183         packet_length = 0;
1184         return type;
1185 }
1186
1187 int
1188 packet_read_poll_seqnr(u_int32_t *seqnr_p)
1189 {
1190         u_int reason, seqnr;
1191         u_char type;
1192         char *msg;
1193
1194         for (;;) {
1195                 if (compat20) {
1196                         type = packet_read_poll2(seqnr_p);
1197                         if (type) {
1198                                 keep_alive_timeouts = 0;
1199                                 DBG(debug("received packet type %d", type));
1200                         }
1201                         switch (type) {
1202                         case SSH2_MSG_IGNORE:
1203                                 debug3("Received SSH2_MSG_IGNORE");
1204                                 break;
1205                         case SSH2_MSG_DEBUG:
1206                                 packet_get_char();
1207                                 msg = packet_get_string(NULL);
1208                                 debug("Remote: %.900s", msg);
1209                                 xfree(msg);
1210                                 msg = packet_get_string(NULL);
1211                                 xfree(msg);
1212                                 break;
1213                         case SSH2_MSG_DISCONNECT:
1214                                 reason = packet_get_int();
1215                                 msg = packet_get_string(NULL);
1216                                 logit("Received disconnect from %s: %u: %.400s",
1217                                     get_remote_ipaddr(), reason, msg);
1218                                 xfree(msg);
1219                                 cleanup_exit(255);
1220                                 break;
1221                         case SSH2_MSG_UNIMPLEMENTED:
1222                                 seqnr = packet_get_int();
1223                                 debug("Received SSH2_MSG_UNIMPLEMENTED for %u",
1224                                     seqnr);
1225                                 break;
1226                         default:
1227                                 return type;
1228                         }
1229                 } else {
1230                         type = packet_read_poll1();
1231                         switch (type) {
1232                         case SSH_MSG_IGNORE:
1233                                 break;
1234                         case SSH_MSG_DEBUG:
1235                                 msg = packet_get_string(NULL);
1236                                 debug("Remote: %.900s", msg);
1237                                 xfree(msg);
1238                                 break;
1239                         case SSH_MSG_DISCONNECT:
1240                                 msg = packet_get_string(NULL);
1241                                 logit("Received disconnect from %s: %.400s",
1242                                     get_remote_ipaddr(), msg);
1243                                 cleanup_exit(255);
1244                                 break;
1245                         default:
1246                                 if (type)
1247                                         DBG(debug("received packet type %d", type));
1248                                 return type;
1249                         }
1250                 }
1251         }
1252 }
1253
1254 int
1255 packet_read_poll(void)
1256 {
1257         return packet_read_poll_seqnr(NULL);
1258 }
1259
1260 /*
1261  * Buffers the given amount of input characters.  This is intended to be used
1262  * together with packet_read_poll.
1263  */
1264
1265 void
1266 packet_process_incoming(const char *buf, u_int len)
1267 {
1268         buffer_append(&input, buf, len);
1269 }
1270
1271 /* Returns a character from the packet. */
1272
1273 u_int
1274 packet_get_char(void)
1275 {
1276         char ch;
1277
1278         buffer_get(&incoming_packet, &ch, 1);
1279         return (u_char) ch;
1280 }
1281
1282 /* Returns an integer from the packet data. */
1283
1284 u_int
1285 packet_get_int(void)
1286 {
1287         return buffer_get_int(&incoming_packet);
1288 }
1289
1290 /*
1291  * Returns an arbitrary precision integer from the packet data.  The integer
1292  * must have been initialized before this call.
1293  */
1294
1295 void
1296 packet_get_bignum(BIGNUM * value)
1297 {
1298         buffer_get_bignum(&incoming_packet, value);
1299 }
1300
1301 void
1302 packet_get_bignum2(BIGNUM * value)
1303 {
1304         buffer_get_bignum2(&incoming_packet, value);
1305 }
1306
1307 void *
1308 packet_get_raw(u_int *length_ptr)
1309 {
1310         u_int bytes = buffer_len(&incoming_packet);
1311
1312         if (length_ptr != NULL)
1313                 *length_ptr = bytes;
1314         return buffer_ptr(&incoming_packet);
1315 }
1316
1317 int
1318 packet_remaining(void)
1319 {
1320         return buffer_len(&incoming_packet);
1321 }
1322
1323 /*
1324  * Returns a string from the packet data.  The string is allocated using
1325  * xmalloc; it is the responsibility of the calling program to free it when
1326  * no longer needed.  The length_ptr argument may be NULL, or point to an
1327  * integer into which the length of the string is stored.
1328  */
1329
1330 void *
1331 packet_get_string(u_int *length_ptr)
1332 {
1333         return buffer_get_string(&incoming_packet, length_ptr);
1334 }
1335
1336 void *
1337 packet_get_string_ptr(u_int *length_ptr)
1338 {
1339         return buffer_get_string_ptr(&incoming_packet, length_ptr);
1340 }
1341
1342 /*
1343  * Sends a diagnostic message from the server to the client.  This message
1344  * can be sent at any time (but not while constructing another message). The
1345  * message is printed immediately, but only if the client is being executed
1346  * in verbose mode.  These messages are primarily intended to ease debugging
1347  * authentication problems.   The length of the formatted message must not
1348  * exceed 1024 bytes.  This will automatically call packet_write_wait.
1349  */
1350
1351 void
1352 packet_send_debug(const char *fmt,...)
1353 {
1354         char buf[1024];
1355         va_list args;
1356
1357         if (compat20 && (datafellows & SSH_BUG_DEBUG))
1358                 return;
1359
1360         va_start(args, fmt);
1361         vsnprintf(buf, sizeof(buf), fmt, args);
1362         va_end(args);
1363
1364         if (compat20) {
1365                 packet_start(SSH2_MSG_DEBUG);
1366                 packet_put_char(0);     /* bool: always display */
1367                 packet_put_cstring(buf);
1368                 packet_put_cstring("");
1369         } else {
1370                 packet_start(SSH_MSG_DEBUG);
1371                 packet_put_cstring(buf);
1372         }
1373         packet_send();
1374         packet_write_wait();
1375 }
1376
1377 /*
1378  * Logs the error plus constructs and sends a disconnect packet, closes the
1379  * connection, and exits.  This function never returns. The error message
1380  * should not contain a newline.  The length of the formatted message must
1381  * not exceed 1024 bytes.
1382  */
1383
1384 void
1385 packet_disconnect(const char *fmt,...)
1386 {
1387         char buf[1024];
1388         va_list args;
1389         static int disconnecting = 0;
1390
1391         if (disconnecting)      /* Guard against recursive invocations. */
1392                 fatal("packet_disconnect called recursively.");
1393         disconnecting = 1;
1394
1395         /*
1396          * Format the message.  Note that the caller must make sure the
1397          * message is of limited size.
1398          */
1399         va_start(args, fmt);
1400         vsnprintf(buf, sizeof(buf), fmt, args);
1401         va_end(args);
1402
1403         /* Display the error locally */
1404         logit("Disconnecting: %.100s", buf);
1405
1406         /* Send the disconnect message to the other side, and wait for it to get sent. */
1407         if (compat20) {
1408                 packet_start(SSH2_MSG_DISCONNECT);
1409                 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR);
1410                 packet_put_cstring(buf);
1411                 packet_put_cstring("");
1412         } else {
1413                 packet_start(SSH_MSG_DISCONNECT);
1414                 packet_put_cstring(buf);
1415         }
1416         packet_send();
1417         packet_write_wait();
1418
1419         /* Stop listening for connections. */
1420         channel_close_all();
1421
1422         /* Close the connection. */
1423         packet_close();
1424         cleanup_exit(255);
1425 }
1426
1427 /* Checks if there is any buffered output, and tries to write some of the output. */
1428
1429 void
1430 packet_write_poll(void)
1431 {
1432         int len = buffer_len(&output);
1433
1434         if (len > 0) {
1435                 len = write(connection_out, buffer_ptr(&output), len);
1436                 if (len <= 0) {
1437                         if (errno == EAGAIN)
1438                                 return;
1439                         else
1440                                 fatal("Write failed: %.100s", strerror(errno));
1441                 }
1442                 buffer_consume(&output, len);
1443         }
1444 }
1445
1446 /*
1447  * Calls packet_write_poll repeatedly until all pending output data has been
1448  * written.
1449  */
1450
1451 void
1452 packet_write_wait(void)
1453 {
1454         fd_set *setp;
1455
1456         setp = (fd_set *)xcalloc(howmany(connection_out + 1, NFDBITS),
1457             sizeof(fd_mask));
1458         packet_write_poll();
1459         while (packet_have_data_to_write()) {
1460                 memset(setp, 0, howmany(connection_out + 1, NFDBITS) *
1461                     sizeof(fd_mask));
1462                 FD_SET(connection_out, setp);
1463                 while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 &&
1464                     (errno == EAGAIN || errno == EINTR))
1465                         ;
1466                 packet_write_poll();
1467         }
1468         xfree(setp);
1469 }
1470
1471 /* Returns true if there is buffered data to write to the connection. */
1472
1473 int
1474 packet_have_data_to_write(void)
1475 {
1476         return buffer_len(&output) != 0;
1477 }
1478
1479 /* Returns true if there is not too much data to write to the connection. */
1480
1481 int
1482 packet_not_very_much_data_to_write(void)
1483 {
1484         if (interactive_mode)
1485                 return buffer_len(&output) < 16384;
1486         else
1487                 return buffer_len(&output) < 128 * 1024;
1488 }
1489
1490
1491 static void
1492 packet_set_tos(int interactive)
1493 {
1494 #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
1495         int tos = interactive ? IPTOS_LOWDELAY : IPTOS_THROUGHPUT;
1496
1497         if (!packet_connection_is_on_socket() ||
1498             !packet_connection_is_ipv4())
1499                 return;
1500         if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, &tos,
1501             sizeof(tos)) < 0)
1502                 error("setsockopt IP_TOS %d: %.100s:",
1503                     tos, strerror(errno));
1504 #endif
1505 }
1506
1507 /* Informs that the current session is interactive.  Sets IP flags for that. */
1508
1509 void
1510 packet_set_interactive(int interactive)
1511 {
1512         static int called = 0;
1513
1514         if (called)
1515                 return;
1516         called = 1;
1517
1518         /* Record that we are in interactive mode. */
1519         interactive_mode = interactive;
1520
1521         /* Only set socket options if using a socket.  */
1522         if (!packet_connection_is_on_socket())
1523                 return;
1524         set_nodelay(connection_in);
1525         packet_set_tos(interactive);
1526 }
1527
1528 /* Returns true if the current connection is interactive. */
1529
1530 int
1531 packet_is_interactive(void)
1532 {
1533         return interactive_mode;
1534 }
1535
1536 int
1537 packet_set_maxsize(u_int s)
1538 {
1539         static int called = 0;
1540
1541         if (called) {
1542                 logit("packet_set_maxsize: called twice: old %d new %d",
1543                     max_packet_size, s);
1544                 return -1;
1545         }
1546         if (s < 4 * 1024 || s > 1024 * 1024) {
1547                 logit("packet_set_maxsize: bad size %d", s);
1548                 return -1;
1549         }
1550         called = 1;
1551         debug("packet_set_maxsize: setting to %d", s);
1552         max_packet_size = s;
1553         return s;
1554 }
1555
1556 /* roundup current message to pad bytes */
1557 void
1558 packet_add_padding(u_char pad)
1559 {
1560         extra_pad = pad;
1561 }
1562
1563 /*
1564  * 9.2.  Ignored Data Message
1565  *
1566  *   byte      SSH_MSG_IGNORE
1567  *   string    data
1568  *
1569  * All implementations MUST understand (and ignore) this message at any
1570  * time (after receiving the protocol version). No implementation is
1571  * required to send them. This message can be used as an additional
1572  * protection measure against advanced traffic analysis techniques.
1573  */
1574 void
1575 packet_send_ignore(int nbytes)
1576 {
1577         u_int32_t rnd = 0;
1578         int i;
1579
1580         packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE);
1581         packet_put_int(nbytes);
1582         for (i = 0; i < nbytes; i++) {
1583                 if (i % 4 == 0)
1584                         rnd = arc4random();
1585                 packet_put_char((u_char)rnd & 0xff);
1586                 rnd >>= 8;
1587         }
1588 }
1589
1590 #define MAX_PACKETS     (1U<<31)
1591 int
1592 packet_need_rekeying(void)
1593 {
1594         if (datafellows & SSH_BUG_NOREKEY)
1595                 return 0;
1596         return
1597             (p_send.packets > MAX_PACKETS) ||
1598             (p_read.packets > MAX_PACKETS) ||
1599             (max_blocks_out && (p_send.blocks > max_blocks_out)) ||
1600             (max_blocks_in  && (p_read.blocks > max_blocks_in));
1601 }
1602
1603 void
1604 packet_set_rekey_limit(u_int32_t bytes)
1605 {
1606         rekey_limit = bytes;
1607 }
1608
1609 void
1610 packet_set_server(void)
1611 {
1612         server_side = 1;
1613 }
1614
1615 void
1616 packet_set_authenticated(void)
1617 {
1618         after_authentication = 1;
1619 }