crypto/openssh-4/packet.c

   1 /* $OpenBSD: packet.c,v 1.145 2006/09/19 21:14:08 markus 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 /* Session key information for Encryption and MAC */
 140 Newkeys *newkeys[MODE_MAX];
 141 static struct packet_state {
 142         u_int32_t seqnr;
 143         u_int32_t packets;
 144         u_int64_t blocks;
 145 } p_read, p_send;
 146
 147 static u_int64_t max_blocks_in, max_blocks_out;
 148 static u_int32_t rekey_limit;
 149
 150 /* Session key for protocol v1 */
 151 static u_char ssh1_key[SSH_SESSION_KEY_LENGTH];
 152 static u_int ssh1_keylen;
 153
 154 /* roundup current message to extra_pad bytes */
 155 static u_char extra_pad = 0;
 156
 157 struct packet {
 158         TAILQ_ENTRY(packet) next;
 159         u_char type;
 160         Buffer payload;
 161 };
 162 TAILQ_HEAD(, packet) outgoing;
 163
 164 /*
 165  * Sets the descriptors used for communication.  Disables encryption until
 166  * packet_set_encryption_key is called.
 167  */
 168 void
 169 packet_set_connection(int fd_in, int fd_out)
 170 {
 171         Cipher *none = cipher_by_name("none");
 172
 173         if (none == NULL)
 174                 fatal("packet_set_connection: cannot load cipher 'none'");
 175         connection_in = fd_in;
 176         connection_out = fd_out;
 177         cipher_init(&send_context, none, (const u_char *)"",
 178             0, NULL, 0, CIPHER_ENCRYPT);
 179         cipher_init(&receive_context, none, (const u_char *)"",
 180             0, NULL, 0, CIPHER_DECRYPT);
 181         newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL;
 182         if (!initialized) {
 183                 initialized = 1;
 184                 buffer_init(&input);
 185                 buffer_init(&output);
 186                 buffer_init(&outgoing_packet);
 187                 buffer_init(&incoming_packet);
 188                 TAILQ_INIT(&outgoing);
 189         }
 190 }
 191
 192 /* Returns 1 if remote host is connected via socket, 0 if not. */
 193
 194 int
 195 packet_connection_is_on_socket(void)
 196 {
 197         struct sockaddr_storage from, to;
 198         socklen_t fromlen, tolen;
 199
 200         /* filedescriptors in and out are the same, so it's a socket */
 201         if (connection_in == connection_out)
 202                 return 1;
 203         fromlen = sizeof(from);
 204         memset(&from, 0, sizeof(from));
 205         if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0)
 206                 return 0;
 207         tolen = sizeof(to);
 208         memset(&to, 0, sizeof(to));
 209         if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0)
 210                 return 0;
 211         if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
 212                 return 0;
 213         if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
 214                 return 0;
 215         return 1;
 216 }
 217
 218 /*
 219  * Exports an IV from the CipherContext required to export the key
 220  * state back from the unprivileged child to the privileged parent
 221  * process.
 222  */
 223
 224 void
 225 packet_get_keyiv(int mode, u_char *iv, u_int len)
 226 {
 227         CipherContext *cc;
 228
 229         if (mode == MODE_OUT)
 230                 cc = &send_context;
 231         else
 232                 cc = &receive_context;
 233
 234         cipher_get_keyiv(cc, iv, len);
 235 }
 236
 237 int
 238 packet_get_keycontext(int mode, u_char *dat)
 239 {
 240         CipherContext *cc;
 241
 242         if (mode == MODE_OUT)
 243                 cc = &send_context;
 244         else
 245                 cc = &receive_context;
 246
 247         return (cipher_get_keycontext(cc, dat));
 248 }
 249
 250 void
 251 packet_set_keycontext(int mode, u_char *dat)
 252 {
 253         CipherContext *cc;
 254
 255         if (mode == MODE_OUT)
 256                 cc = &send_context;
 257         else
 258                 cc = &receive_context;
 259
 260         cipher_set_keycontext(cc, dat);
 261 }
 262
 263 int
 264 packet_get_keyiv_len(int mode)
 265 {
 266         CipherContext *cc;
 267
 268         if (mode == MODE_OUT)
 269                 cc = &send_context;
 270         else
 271                 cc = &receive_context;
 272
 273         return (cipher_get_keyiv_len(cc));
 274 }
 275
 276 void
 277 packet_set_iv(int mode, u_char *dat)
 278 {
 279         CipherContext *cc;
 280
 281         if (mode == MODE_OUT)
 282                 cc = &send_context;
 283         else
 284                 cc = &receive_context;
 285
 286         cipher_set_keyiv(cc, dat);
 287 }
 288
 289 int
 290 packet_get_ssh1_cipher(void)
 291 {
 292         return (cipher_get_number(receive_context.cipher));
 293 }
 294
 295 void
 296 packet_get_state(int mode, u_int32_t *seqnr, u_int64_t *blocks, u_int32_t *packets)
 297 {
 298         struct packet_state *state;
 299
 300         state = (mode == MODE_IN) ? &p_read : &p_send;
 301         *seqnr = state->seqnr;
 302         *blocks = state->blocks;
 303         *packets = state->packets;
 304 }
 305
 306 void
 307 packet_set_state(int mode, u_int32_t seqnr, u_int64_t blocks, u_int32_t packets)
 308 {
 309         struct packet_state *state;
 310
 311         state = (mode == MODE_IN) ? &p_read : &p_send;
 312         state->seqnr = seqnr;
 313         state->blocks = blocks;
 314         state->packets = packets;
 315 }
 316
 317 /* returns 1 if connection is via ipv4 */
 318
 319 int
 320 packet_connection_is_ipv4(void)
 321 {
 322         struct sockaddr_storage to;
 323         socklen_t tolen = sizeof(to);
 324
 325         memset(&to, 0, sizeof(to));
 326         if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
 327                 return 0;
 328         if (to.ss_family == AF_INET)
 329                 return 1;
 330 #ifdef IPV4_IN_IPV6
 331         if (to.ss_family == AF_INET6 &&
 332             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&to)->sin6_addr))
 333                 return 1;
 334 #endif
 335         return 0;
 336 }
 337
 338 /* Sets the connection into non-blocking mode. */
 339
 340 void
 341 packet_set_nonblocking(void)
 342 {
 343         /* Set the socket into non-blocking mode. */
 344         set_nonblock(connection_in);
 345
 346         if (connection_out != connection_in)
 347                 set_nonblock(connection_out);
 348 }
 349
 350 /* Returns the socket used for reading. */
 351
 352 int
 353 packet_get_connection_in(void)
 354 {
 355         return connection_in;
 356 }
 357
 358 /* Returns the descriptor used for writing. */
 359
 360 int
 361 packet_get_connection_out(void)
 362 {
 363         return connection_out;
 364 }
 365
 366 /* Closes the connection and clears and frees internal data structures. */
 367
 368 void
 369 packet_close(void)
 370 {
 371         if (!initialized)
 372                 return;
 373         initialized = 0;
 374         if (connection_in == connection_out) {
 375                 shutdown(connection_out, SHUT_RDWR);
 376                 close(connection_out);
 377         } else {
 378                 close(connection_in);
 379                 close(connection_out);
 380         }
 381         buffer_free(&input);
 382         buffer_free(&output);
 383         buffer_free(&outgoing_packet);
 384         buffer_free(&incoming_packet);
 385         if (compression_buffer_ready) {
 386                 buffer_free(&compression_buffer);
 387                 buffer_compress_uninit();
 388         }
 389         cipher_cleanup(&send_context);
 390         cipher_cleanup(&receive_context);
 391 }
 392
 393 /* Sets remote side protocol flags. */
 394
 395 void
 396 packet_set_protocol_flags(u_int protocol_flags)
 397 {
 398         remote_protocol_flags = protocol_flags;
 399 }
 400
 401 /* Returns the remote protocol flags set earlier by the above function. */
 402
 403 u_int
 404 packet_get_protocol_flags(void)
 405 {
 406         return remote_protocol_flags;
 407 }
 408
 409 /*
 410  * Starts packet compression from the next packet on in both directions.
 411  * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
 412  */
 413
 414 static void
 415 packet_init_compression(void)
 416 {
 417         if (compression_buffer_ready == 1)
 418                 return;
 419         compression_buffer_ready = 1;
 420         buffer_init(&compression_buffer);
 421 }
 422
 423 void
 424 packet_start_compression(int level)
 425 {
 426         if (packet_compression && !compat20)
 427                 fatal("Compression already enabled.");
 428         packet_compression = 1;
 429         packet_init_compression();
 430         buffer_compress_init_send(level);
 431         buffer_compress_init_recv();
 432 }
 433
 434 /*
 435  * Causes any further packets to be encrypted using the given key.  The same
 436  * key is used for both sending and reception.  However, both directions are
 437  * encrypted independently of each other.
 438  */
 439
 440 void
 441 packet_set_encryption_key(const u_char *key, u_int keylen,
 442     int number)
 443 {
 444         Cipher *cipher = cipher_by_number(number);
 445
 446         if (cipher == NULL)
 447                 fatal("packet_set_encryption_key: unknown cipher number %d", number);
 448         if (keylen < 20)
 449                 fatal("packet_set_encryption_key: keylen too small: %d", keylen);
 450         if (keylen > SSH_SESSION_KEY_LENGTH)
 451                 fatal("packet_set_encryption_key: keylen too big: %d", keylen);
 452         memcpy(ssh1_key, key, keylen);
 453         ssh1_keylen = keylen;
 454         cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT);
 455         cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT);
 456 }
 457
 458 u_int
 459 packet_get_encryption_key(u_char *key)
 460 {
 461         if (key == NULL)
 462                 return (ssh1_keylen);
 463         memcpy(key, ssh1_key, ssh1_keylen);
 464         return (ssh1_keylen);
 465 }
 466
 467 /* Start constructing a packet to send. */
 468 void
 469 packet_start(u_char type)
 470 {
 471         u_char buf[9];
 472         int len;
 473
 474         DBG(debug("packet_start[%d]", type));
 475         len = compat20 ? 6 : 9;
 476         memset(buf, 0, len - 1);
 477         buf[len - 1] = type;
 478         buffer_clear(&outgoing_packet);
 479         buffer_append(&outgoing_packet, buf, len);
 480 }
 481
 482 /* Append payload. */
 483 void
 484 packet_put_char(int value)
 485 {
 486         char ch = value;
 487
 488         buffer_append(&outgoing_packet, &ch, 1);
 489 }
 490
 491 void
 492 packet_put_int(u_int value)
 493 {
 494         buffer_put_int(&outgoing_packet, value);
 495 }
 496
 497 void
 498 packet_put_string(const void *buf, u_int len)
 499 {
 500         buffer_put_string(&outgoing_packet, buf, len);
 501 }
 502
 503 void
 504 packet_put_cstring(const char *str)
 505 {
 506         buffer_put_cstring(&outgoing_packet, str);
 507 }
 508
 509 void
 510 packet_put_raw(const void *buf, u_int len)
 511 {
 512         buffer_append(&outgoing_packet, buf, len);
 513 }
 514
 515 void
 516 packet_put_bignum(BIGNUM * value)
 517 {
 518         buffer_put_bignum(&outgoing_packet, value);
 519 }
 520
 521 void
 522 packet_put_bignum2(BIGNUM * value)
 523 {
 524         buffer_put_bignum2(&outgoing_packet, value);
 525 }
 526
 527 /*
 528  * Finalizes and sends the packet.  If the encryption key has been set,
 529  * encrypts the packet before sending.
 530  */
 531
 532 static void
 533 packet_send1(void)
 534 {
 535         u_char buf[8], *cp;
 536         int i, padding, len;
 537         u_int checksum;
 538         u_int32_t rnd = 0;
 539
 540         /*
 541          * If using packet compression, compress the payload of the outgoing
 542          * packet.
 543          */
 544         if (packet_compression) {
 545                 buffer_clear(&compression_buffer);
 546                 /* Skip padding. */
 547                 buffer_consume(&outgoing_packet, 8);
 548                 /* padding */
 549                 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
 550                 buffer_compress(&outgoing_packet, &compression_buffer);
 551                 buffer_clear(&outgoing_packet);
 552                 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
 553                     buffer_len(&compression_buffer));
 554         }
 555         /* Compute packet length without padding (add checksum, remove padding). */
 556         len = buffer_len(&outgoing_packet) + 4 - 8;
 557
 558         /* Insert padding. Initialized to zero in packet_start1() */
 559         padding = 8 - len % 8;
 560         if (!send_context.plaintext) {
 561                 cp = buffer_ptr(&outgoing_packet);
 562                 for (i = 0; i < padding; i++) {
 563                         if (i % 4 == 0)
 564                                 rnd = arc4random();
 565                         cp[7 - i] = rnd & 0xff;
 566                         rnd >>= 8;
 567                 }
 568         }
 569         buffer_consume(&outgoing_packet, 8 - padding);
 570
 571         /* Add check bytes. */
 572         checksum = ssh_crc32(buffer_ptr(&outgoing_packet),
 573             buffer_len(&outgoing_packet));
 574         put_u32(buf, checksum);
 575         buffer_append(&outgoing_packet, buf, 4);
 576
 577 #ifdef PACKET_DEBUG
 578         fprintf(stderr, "packet_send plain: ");
 579         buffer_dump(&outgoing_packet);
 580 #endif
 581
 582         /* Append to output. */
 583         put_u32(buf, len);
 584         buffer_append(&output, buf, 4);
 585         cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
 586         cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
 587             buffer_len(&outgoing_packet));
 588
 589 #ifdef PACKET_DEBUG
 590         fprintf(stderr, "encrypted: ");
 591         buffer_dump(&output);
 592 #endif
 593
 594         buffer_clear(&outgoing_packet);
 595
 596         /*
 597          * Note that the packet is now only buffered in output.  It won't be
 598          * actually sent until packet_write_wait or packet_write_poll is
 599          * called.
 600          */
 601 }
 602
 603 void
 604 set_newkeys(int mode)
 605 {
 606         Enc *enc;
 607         Mac *mac;
 608         Comp *comp;
 609         CipherContext *cc;
 610         u_int64_t *max_blocks;
 611         int crypt_type;
 612
 613         debug2("set_newkeys: mode %d", mode);
 614
 615         if (mode == MODE_OUT) {
 616                 cc = &send_context;
 617                 crypt_type = CIPHER_ENCRYPT;
 618                 p_send.packets = p_send.blocks = 0;
 619                 max_blocks = &max_blocks_out;
 620         } else {
 621                 cc = &receive_context;
 622                 crypt_type = CIPHER_DECRYPT;
 623                 p_read.packets = p_read.blocks = 0;
 624                 max_blocks = &max_blocks_in;
 625         }
 626         if (newkeys[mode] != NULL) {
 627                 debug("set_newkeys: rekeying");
 628                 cipher_cleanup(cc);
 629                 enc  = &newkeys[mode]->enc;
 630                 mac  = &newkeys[mode]->mac;
 631                 comp = &newkeys[mode]->comp;
 632                 memset(mac->key, 0, mac->key_len);
 633                 xfree(enc->name);
 634                 xfree(enc->iv);
 635                 xfree(enc->key);
 636                 xfree(mac->name);
 637                 xfree(mac->key);
 638                 xfree(comp->name);
 639                 xfree(newkeys[mode]);
 640         }
 641         newkeys[mode] = kex_get_newkeys(mode);
 642         if (newkeys[mode] == NULL)
 643                 fatal("newkeys: no keys for mode %d", mode);
 644         enc  = &newkeys[mode]->enc;
 645         mac  = &newkeys[mode]->mac;
 646         comp = &newkeys[mode]->comp;
 647         if (mac->md != NULL)
 648                 mac->enabled = 1;
 649         DBG(debug("cipher_init_context: %d", mode));
 650         cipher_init(cc, enc->cipher, enc->key, enc->key_len,
 651             enc->iv, enc->block_size, crypt_type);
 652         /* Deleting the keys does not gain extra security */
 653         /* memset(enc->iv,  0, enc->block_size);
 654            memset(enc->key, 0, enc->key_len); */
 655         if ((comp->type == COMP_ZLIB ||
 656             (comp->type == COMP_DELAYED && after_authentication)) &&
 657             comp->enabled == 0) {
 658                 packet_init_compression();
 659                 if (mode == MODE_OUT)
 660                         buffer_compress_init_send(6);
 661                 else
 662                         buffer_compress_init_recv();
 663                 comp->enabled = 1;
 664         }
 665         /*
 666          * The 2^(blocksize*2) limit is too expensive for 3DES,
 667          * blowfish, etc, so enforce a 1GB limit for small blocksizes.
 668          */
 669         if (enc->block_size >= 16)
 670                 *max_blocks = (u_int64_t)1 << (enc->block_size*2);
 671         else
 672                 *max_blocks = ((u_int64_t)1 << 30) / enc->block_size;
 673         if (rekey_limit)
 674                 *max_blocks = MIN(*max_blocks, rekey_limit / enc->block_size);
 675 }
 676
 677 /*
 678  * Delayed compression for SSH2 is enabled after authentication:
 679  * This happens on the server side after a SSH2_MSG_USERAUTH_SUCCESS is sent,
 680  * and on the client side after a SSH2_MSG_USERAUTH_SUCCESS is received.
 681  */
 682 static void
 683 packet_enable_delayed_compress(void)
 684 {
 685         Comp *comp = NULL;
 686         int mode;
 687
 688         /*
 689          * Remember that we are past the authentication step, so rekeying
 690          * with COMP_DELAYED will turn on compression immediately.
 691          */
 692         after_authentication = 1;
 693         for (mode = 0; mode < MODE_MAX; mode++) {
 694                 /* protocol error: USERAUTH_SUCCESS received before NEWKEYS */
 695                 if (newkeys[mode] == NULL)
 696                         continue;
 697                 comp = &newkeys[mode]->comp;
 698                 if (comp && !comp->enabled && comp->type == COMP_DELAYED) {
 699                         packet_init_compression();
 700                         if (mode == MODE_OUT)
 701                                 buffer_compress_init_send(6);
 702                         else
 703                                 buffer_compress_init_recv();
 704                         comp->enabled = 1;
 705                 }
 706         }
 707 }
 708
 709 /*
 710  * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
 711  */
 712 static void
 713 packet_send2_wrapped(void)
 714 {
 715         u_char type, *cp, *macbuf = NULL;
 716         u_char padlen, pad;
 717         u_int packet_length = 0;
 718         u_int i, len;
 719         u_int32_t rnd = 0;
 720         Enc *enc   = NULL;
 721         Mac *mac   = NULL;
 722         Comp *comp = NULL;
 723         int block_size;
 724
 725         if (newkeys[MODE_OUT] != NULL) {
 726                 enc  = &newkeys[MODE_OUT]->enc;
 727                 mac  = &newkeys[MODE_OUT]->mac;
 728                 comp = &newkeys[MODE_OUT]->comp;
 729         }
 730         block_size = enc ? enc->block_size : 8;
 731
 732         cp = buffer_ptr(&outgoing_packet);
 733         type = cp[5];
 734
 735 #ifdef PACKET_DEBUG
 736         fprintf(stderr, "plain:     ");
 737         buffer_dump(&outgoing_packet);
 738 #endif
 739
 740         if (comp && comp->enabled) {
 741                 len = buffer_len(&outgoing_packet);
 742                 /* skip header, compress only payload */
 743                 buffer_consume(&outgoing_packet, 5);
 744                 buffer_clear(&compression_buffer);
 745                 buffer_compress(&outgoing_packet, &compression_buffer);
 746                 buffer_clear(&outgoing_packet);
 747                 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5);
 748                 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
 749                     buffer_len(&compression_buffer));
 750                 DBG(debug("compression: raw %d compressed %d", len,
 751                     buffer_len(&outgoing_packet)));
 752         }
 753
 754         /* sizeof (packet_len + pad_len + payload) */
 755         len = buffer_len(&outgoing_packet);
 756
 757         /*
 758          * calc size of padding, alloc space, get random data,
 759          * minimum padding is 4 bytes
 760          */
 761         padlen = block_size - (len % block_size);
 762         if (padlen < 4)
 763                 padlen += block_size;
 764         if (extra_pad) {
 765                 /* will wrap if extra_pad+padlen > 255 */
 766                 extra_pad  = roundup(extra_pad, block_size);
 767                 pad = extra_pad - ((len + padlen) % extra_pad);
 768                 debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)",
 769                     pad, len, padlen, extra_pad);
 770                 padlen += pad;
 771                 extra_pad = 0;
 772         }
 773         cp = buffer_append_space(&outgoing_packet, padlen);
 774         if (enc && !send_context.plaintext) {
 775                 /* random padding */
 776                 for (i = 0; i < padlen; i++) {
 777                         if (i % 4 == 0)
 778                                 rnd = arc4random();
 779                         cp[i] = rnd & 0xff;
 780                         rnd >>= 8;
 781                 }
 782         } else {
 783                 /* clear padding */
 784                 memset(cp, 0, padlen);
 785         }
 786         /* packet_length includes payload, padding and padding length field */
 787         packet_length = buffer_len(&outgoing_packet) - 4;
 788         cp = buffer_ptr(&outgoing_packet);
 789         put_u32(cp, packet_length);
 790         cp[4] = padlen;
 791         DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
 792
 793         /* compute MAC over seqnr and packet(length fields, payload, padding) */
 794         if (mac && mac->enabled) {
 795                 macbuf = mac_compute(mac, p_send.seqnr,
 796                     buffer_ptr(&outgoing_packet),
 797                     buffer_len(&outgoing_packet));
 798                 DBG(debug("done calc MAC out #%d", p_send.seqnr));
 799         }
 800         /* encrypt packet and append to output buffer. */
 801         cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
 802         cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
 803             buffer_len(&outgoing_packet));
 804         /* append unencrypted MAC */
 805         if (mac && mac->enabled)
 806                 buffer_append(&output, macbuf, mac->mac_len);
 807 #ifdef PACKET_DEBUG
 808         fprintf(stderr, "encrypted: ");
 809         buffer_dump(&output);
 810 #endif
 811         /* increment sequence number for outgoing packets */
 812         if (++p_send.seqnr == 0)
 813                 logit("outgoing seqnr wraps around");
 814         if (++p_send.packets == 0)
 815                 if (!(datafellows & SSH_BUG_NOREKEY))
 816                         fatal("XXX too many packets with same key");
 817         p_send.blocks += (packet_length + 4) / block_size;
 818         buffer_clear(&outgoing_packet);
 819
 820         if (type == SSH2_MSG_NEWKEYS)
 821                 set_newkeys(MODE_OUT);
 822         else if (type == SSH2_MSG_USERAUTH_SUCCESS && server_side)
 823                 packet_enable_delayed_compress();
 824 }
 825
 826 static void
 827 packet_send2(void)
 828 {
 829         static int rekeying = 0;
 830         struct packet *p;
 831         u_char type, *cp;
 832
 833         cp = buffer_ptr(&outgoing_packet);
 834         type = cp[5];
 835
 836         /* during rekeying we can only send key exchange messages */
 837         if (rekeying) {
 838                 if (!((type >= SSH2_MSG_TRANSPORT_MIN) &&
 839                     (type <= SSH2_MSG_TRANSPORT_MAX))) {
 840                         debug("enqueue packet: %u", type);
 841                         p = xmalloc(sizeof(*p));
 842                         p->type = type;
 843                         memcpy(&p->payload, &outgoing_packet, sizeof(Buffer));
 844                         buffer_init(&outgoing_packet);
 845                         TAILQ_INSERT_TAIL(&outgoing, p, next);
 846                         return;
 847                 }
 848         }
 849
 850         /* rekeying starts with sending KEXINIT */
 851         if (type == SSH2_MSG_KEXINIT)
 852                 rekeying = 1;
 853
 854         packet_send2_wrapped();
 855
 856         /* after a NEWKEYS message we can send the complete queue */
 857         if (type == SSH2_MSG_NEWKEYS) {
 858                 rekeying = 0;
 859                 while ((p = TAILQ_FIRST(&outgoing))) {
 860                         type = p->type;
 861                         debug("dequeue packet: %u", type);
 862                         buffer_free(&outgoing_packet);
 863                         memcpy(&outgoing_packet, &p->payload,
 864                             sizeof(Buffer));
 865                         TAILQ_REMOVE(&outgoing, p, next);
 866                         xfree(p);
 867                         packet_send2_wrapped();
 868                 }
 869         }
 870 }
 871
 872 void
 873 packet_send(void)
 874 {
 875         if (compat20)
 876                 packet_send2();
 877         else
 878                 packet_send1();
 879         DBG(debug("packet_send done"));
 880 }
 881
 882 /*
 883  * Waits until a packet has been received, and returns its type.  Note that
 884  * no other data is processed until this returns, so this function should not
 885  * be used during the interactive session.
 886  */
 887
 888 int
 889 packet_read_seqnr(u_int32_t *seqnr_p)
 890 {
 891         int type, len;
 892         fd_set *setp;
 893         char buf[8192];
 894         DBG(debug("packet_read()"));
 895
 896         setp = (fd_set *)xcalloc(howmany(connection_in+1, NFDBITS),
 897             sizeof(fd_mask));
 898
 899         /* Since we are blocking, ensure that all written packets have been sent. */
 900         packet_write_wait();
 901
 902         /* Stay in the loop until we have received a complete packet. */
 903         for (;;) {
 904                 /* Try to read a packet from the buffer. */
 905                 type = packet_read_poll_seqnr(seqnr_p);
 906                 if (!compat20 && (
 907                     type == SSH_SMSG_SUCCESS
 908                     || type == SSH_SMSG_FAILURE
 909                     || type == SSH_CMSG_EOF
 910                     || type == SSH_CMSG_EXIT_CONFIRMATION))
 911                         packet_check_eom();
 912                 /* If we got a packet, return it. */
 913                 if (type != SSH_MSG_NONE) {
 914                         xfree(setp);
 915                         return type;
 916                 }
 917                 /*
 918                  * Otherwise, wait for some data to arrive, add it to the
 919                  * buffer, and try again.
 920                  */
 921                 memset(setp, 0, howmany(connection_in + 1, NFDBITS) *
 922                     sizeof(fd_mask));
 923                 FD_SET(connection_in, setp);
 924
 925                 /* Wait for some data to arrive. */
 926                 while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 &&
 927                     (errno == EAGAIN || errno == EINTR))
 928                         ;
 929
 930                 /* Read data from the socket. */
 931                 len = read(connection_in, buf, sizeof(buf));
 932                 if (len == 0) {
 933                         logit("Connection closed by %.200s", get_remote_ipaddr());
 934                         cleanup_exit(255);
 935                 }
 936                 if (len < 0)
 937                         fatal("Read from socket failed: %.100s", strerror(errno));
 938                 /* Append it to the buffer. */
 939                 packet_process_incoming(buf, len);
 940         }
 941         /* NOTREACHED */
 942 }
 943
 944 int
 945 packet_read(void)
 946 {
 947         return packet_read_seqnr(NULL);
 948 }
 949
 950 /*
 951  * Waits until a packet has been received, verifies that its type matches
 952  * that given, and gives a fatal error and exits if there is a mismatch.
 953  */
 954
 955 void
 956 packet_read_expect(int expected_type)
 957 {
 958         int type;
 959
 960         type = packet_read();
 961         if (type != expected_type)
 962                 packet_disconnect("Protocol error: expected packet type %d, got %d",
 963                     expected_type, type);
 964 }
 965
 966 /* Checks if a full packet is available in the data received so far via
 967  * packet_process_incoming.  If so, reads the packet; otherwise returns
 968  * SSH_MSG_NONE.  This does not wait for data from the connection.
 969  *
 970  * SSH_MSG_DISCONNECT is handled specially here.  Also,
 971  * SSH_MSG_IGNORE messages are skipped by this function and are never returned
 972  * to higher levels.
 973  */
 974
 975 static int
 976 packet_read_poll1(void)
 977 {
 978         u_int len, padded_len;
 979         u_char *cp, type;
 980         u_int checksum, stored_checksum;
 981
 982         /* Check if input size is less than minimum packet size. */
 983         if (buffer_len(&input) < 4 + 8)
 984                 return SSH_MSG_NONE;
 985         /* Get length of incoming packet. */
 986         cp = buffer_ptr(&input);
 987         len = get_u32(cp);
 988         if (len < 1 + 2 + 2 || len > 256 * 1024)
 989                 packet_disconnect("Bad packet length %u.", len);
 990         padded_len = (len + 8) & ~7;
 991
 992         /* Check if the packet has been entirely received. */
 993         if (buffer_len(&input) < 4 + padded_len)
 994                 return SSH_MSG_NONE;
 995
 996         /* The entire packet is in buffer. */
 997
 998         /* Consume packet length. */
 999         buffer_consume(&input, 4);
1000
1001         /*
1002          * Cryptographic attack detector for ssh
1003          * (C)1998 CORE-SDI, Buenos Aires Argentina
1004          * Ariel Futoransky(futo@core-sdi.com)
1005          */
1006         if (!receive_context.plaintext) {
1007                 switch (detect_attack(buffer_ptr(&input), padded_len)) {
1008                 case DEATTACK_DETECTED:
1009                         packet_disconnect("crc32 compensation attack: "
1010                             "network attack detected");
1011                 case DEATTACK_DOS_DETECTED:
1012                         packet_disconnect("deattack denial of "
1013                             "service detected");
1014                 }
1015         }
1016
1017         /* Decrypt data to incoming_packet. */
1018         buffer_clear(&incoming_packet);
1019         cp = buffer_append_space(&incoming_packet, padded_len);
1020         cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len);
1021
1022         buffer_consume(&input, padded_len);
1023
1024 #ifdef PACKET_DEBUG
1025         fprintf(stderr, "read_poll plain: ");
1026         buffer_dump(&incoming_packet);
1027 #endif
1028
1029         /* Compute packet checksum. */
1030         checksum = ssh_crc32(buffer_ptr(&incoming_packet),
1031             buffer_len(&incoming_packet) - 4);
1032
1033         /* Skip padding. */
1034         buffer_consume(&incoming_packet, 8 - len % 8);
1035
1036         /* Test check bytes. */
1037         if (len != buffer_len(&incoming_packet))
1038                 packet_disconnect("packet_read_poll1: len %d != buffer_len %d.",
1039                     len, buffer_len(&incoming_packet));
1040
1041         cp = (u_char *)buffer_ptr(&incoming_packet) + len - 4;
1042         stored_checksum = get_u32(cp);
1043         if (checksum != stored_checksum)
1044                 packet_disconnect("Corrupted check bytes on input.");
1045         buffer_consume_end(&incoming_packet, 4);
1046
1047         if (packet_compression) {
1048                 buffer_clear(&compression_buffer);
1049                 buffer_uncompress(&incoming_packet, &compression_buffer);
1050                 buffer_clear(&incoming_packet);
1051                 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1052                     buffer_len(&compression_buffer));
1053         }
1054         type = buffer_get_char(&incoming_packet);
1055         if (type < SSH_MSG_MIN || type > SSH_MSG_MAX)
1056                 packet_disconnect("Invalid ssh1 packet type: %d", type);
1057         return type;
1058 }
1059
1060 static int
1061 packet_read_poll2(u_int32_t *seqnr_p)
1062 {
1063         static u_int packet_length = 0;
1064         u_int padlen, need;
1065         u_char *macbuf, *cp, type;
1066         u_int maclen, block_size;
1067         Enc *enc   = NULL;
1068         Mac *mac   = NULL;
1069         Comp *comp = NULL;
1070
1071         if (newkeys[MODE_IN] != NULL) {
1072                 enc  = &newkeys[MODE_IN]->enc;
1073                 mac  = &newkeys[MODE_IN]->mac;
1074                 comp = &newkeys[MODE_IN]->comp;
1075         }
1076         maclen = mac && mac->enabled ? mac->mac_len : 0;
1077         block_size = enc ? enc->block_size : 8;
1078
1079         if (packet_length == 0) {
1080                 /*
1081                  * check if input size is less than the cipher block size,
1082                  * decrypt first block and extract length of incoming packet
1083                  */
1084                 if (buffer_len(&input) < block_size)
1085                         return SSH_MSG_NONE;
1086                 buffer_clear(&incoming_packet);
1087                 cp = buffer_append_space(&incoming_packet, block_size);
1088                 cipher_crypt(&receive_context, cp, buffer_ptr(&input),
1089                     block_size);
1090                 cp = buffer_ptr(&incoming_packet);
1091                 packet_length = get_u32(cp);
1092                 if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
1093 #ifdef PACKET_DEBUG
1094                         buffer_dump(&incoming_packet);
1095 #endif
1096                         packet_disconnect("Bad packet length %u.", packet_length);
1097                 }
1098                 DBG(debug("input: packet len %u", packet_length+4));
1099                 buffer_consume(&input, block_size);
1100         }
1101         /* we have a partial packet of block_size bytes */
1102         need = 4 + packet_length - block_size;
1103         DBG(debug("partial packet %d, need %d, maclen %d", block_size,
1104             need, maclen));
1105         if (need % block_size != 0)
1106                 fatal("padding error: need %d block %d mod %d",
1107                     need, block_size, need % block_size);
1108         /*
1109          * check if the entire packet has been received and
1110          * decrypt into incoming_packet
1111          */
1112         if (buffer_len(&input) < need + maclen)
1113                 return SSH_MSG_NONE;
1114 #ifdef PACKET_DEBUG
1115         fprintf(stderr, "read_poll enc/full: ");
1116         buffer_dump(&input);
1117 #endif
1118         cp = buffer_append_space(&incoming_packet, need);
1119         cipher_crypt(&receive_context, cp, buffer_ptr(&input), need);
1120         buffer_consume(&input, need);
1121         /*
1122          * compute MAC over seqnr and packet,
1123          * increment sequence number for incoming packet
1124          */
1125         if (mac && mac->enabled) {
1126                 macbuf = mac_compute(mac, p_read.seqnr,
1127                     buffer_ptr(&incoming_packet),
1128                     buffer_len(&incoming_packet));
1129                 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
1130                         packet_disconnect("Corrupted MAC on input.");
1131                 DBG(debug("MAC #%d ok", p_read.seqnr));
1132                 buffer_consume(&input, mac->mac_len);
1133         }
1134         if (seqnr_p != NULL)
1135                 *seqnr_p = p_read.seqnr;
1136         if (++p_read.seqnr == 0)
1137                 logit("incoming seqnr wraps around");
1138         if (++p_read.packets == 0)
1139                 if (!(datafellows & SSH_BUG_NOREKEY))
1140                         fatal("XXX too many packets with same key");
1141         p_read.blocks += (packet_length + 4) / block_size;
1142
1143         /* get padlen */
1144         cp = buffer_ptr(&incoming_packet);
1145         padlen = cp[4];
1146         DBG(debug("input: padlen %d", padlen));
1147         if (padlen < 4)
1148                 packet_disconnect("Corrupted padlen %d on input.", padlen);
1149
1150         /* skip packet size + padlen, discard padding */
1151         buffer_consume(&incoming_packet, 4 + 1);
1152         buffer_consume_end(&incoming_packet, padlen);
1153
1154         DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet)));
1155         if (comp && comp->enabled) {
1156                 buffer_clear(&compression_buffer);
1157                 buffer_uncompress(&incoming_packet, &compression_buffer);
1158                 buffer_clear(&incoming_packet);
1159                 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
1160                     buffer_len(&compression_buffer));
1161                 DBG(debug("input: len after de-compress %d",
1162                     buffer_len(&incoming_packet)));
1163         }
1164         /*
1165          * get packet type, implies consume.
1166          * return length of payload (without type field)
1167          */
1168         type = buffer_get_char(&incoming_packet);
1169         if (type < SSH2_MSG_MIN || type >= SSH2_MSG_LOCAL_MIN)
1170                 packet_disconnect("Invalid ssh2 packet type: %d", type);
1171         if (type == SSH2_MSG_NEWKEYS)
1172                 set_newkeys(MODE_IN);
1173         else if (type == SSH2_MSG_USERAUTH_SUCCESS && !server_side)
1174                 packet_enable_delayed_compress();
1175 #ifdef PACKET_DEBUG
1176         fprintf(stderr, "read/plain[%d]:\r\n", type);
1177         buffer_dump(&incoming_packet);
1178 #endif
1179         /* reset for next packet */
1180         packet_length = 0;
1181         return type;
1182 }
1183
1184 int
1185 packet_read_poll_seqnr(u_int32_t *seqnr_p)
1186 {
1187         u_int reason, seqnr;
1188         u_char type;
1189         char *msg;
1190
1191         for (;;) {
1192                 if (compat20) {
1193                         type = packet_read_poll2(seqnr_p);
1194                         if (type)
1195                                 DBG(debug("received packet type %d", type));
1196                         switch (type) {
1197                         case SSH2_MSG_IGNORE:
1198                                 break;
1199                         case SSH2_MSG_DEBUG:
1200                                 packet_get_char();
1201                                 msg = packet_get_string(NULL);
1202                                 debug("Remote: %.900s", msg);
1203                                 xfree(msg);
1204                                 msg = packet_get_string(NULL);
1205                                 xfree(msg);
1206                                 break;
1207                         case SSH2_MSG_DISCONNECT:
1208                                 reason = packet_get_int();
1209                                 msg = packet_get_string(NULL);
1210                                 logit("Received disconnect from %s: %u: %.400s",
1211                                     get_remote_ipaddr(), reason, msg);
1212                                 xfree(msg);
1213                                 cleanup_exit(255);
1214                                 break;
1215                         case SSH2_MSG_UNIMPLEMENTED:
1216                                 seqnr = packet_get_int();
1217                                 debug("Received SSH2_MSG_UNIMPLEMENTED for %u",
1218                                     seqnr);
1219                                 break;
1220                         default:
1221                                 return type;
1222                         }
1223                 } else {
1224                         type = packet_read_poll1();
1225                         switch (type) {
1226                         case SSH_MSG_IGNORE:
1227                                 break;
1228                         case SSH_MSG_DEBUG:
1229                                 msg = packet_get_string(NULL);
1230                                 debug("Remote: %.900s", msg);
1231                                 xfree(msg);
1232                                 break;
1233                         case SSH_MSG_DISCONNECT:
1234                                 msg = packet_get_string(NULL);
1235                                 logit("Received disconnect from %s: %.400s",
1236                                     get_remote_ipaddr(), msg);
1237                                 cleanup_exit(255);
1238                                 xfree(msg);
1239                                 break;
1240                         default:
1241                                 if (type)
1242                                         DBG(debug("received packet type %d", type));
1243                                 return type;
1244                         }
1245                 }
1246         }
1247 }
1248
1249 int
1250 packet_read_poll(void)
1251 {
1252         return packet_read_poll_seqnr(NULL);
1253 }
1254
1255 /*
1256  * Buffers the given amount of input characters.  This is intended to be used
1257  * together with packet_read_poll.
1258  */
1259
1260 void
1261 packet_process_incoming(const char *buf, u_int len)
1262 {
1263         buffer_append(&input, buf, len);
1264 }
1265
1266 /* Returns a character from the packet. */
1267
1268 u_int
1269 packet_get_char(void)
1270 {
1271         char ch;
1272
1273         buffer_get(&incoming_packet, &ch, 1);
1274         return (u_char) ch;
1275 }
1276
1277 /* Returns an integer from the packet data. */
1278
1279 u_int
1280 packet_get_int(void)
1281 {
1282         return buffer_get_int(&incoming_packet);
1283 }
1284
1285 /*
1286  * Returns an arbitrary precision integer from the packet data.  The integer
1287  * must have been initialized before this call.
1288  */
1289
1290 void
1291 packet_get_bignum(BIGNUM * value)
1292 {
1293         buffer_get_bignum(&incoming_packet, value);
1294 }
1295
1296 void
1297 packet_get_bignum2(BIGNUM * value)
1298 {
1299         buffer_get_bignum2(&incoming_packet, value);
1300 }
1301
1302 void *
1303 packet_get_raw(u_int *length_ptr)
1304 {
1305         u_int bytes = buffer_len(&incoming_packet);
1306
1307         if (length_ptr != NULL)
1308                 *length_ptr = bytes;
1309         return buffer_ptr(&incoming_packet);
1310 }
1311
1312 int
1313 packet_remaining(void)
1314 {
1315         return buffer_len(&incoming_packet);
1316 }
1317
1318 /*
1319  * Returns a string from the packet data.  The string is allocated using
1320  * xmalloc; it is the responsibility of the calling program to free it when
1321  * no longer needed.  The length_ptr argument may be NULL, or point to an
1322  * integer into which the length of the string is stored.
1323  */
1324
1325 void *
1326 packet_get_string(u_int *length_ptr)
1327 {
1328         return buffer_get_string(&incoming_packet, length_ptr);
1329 }
1330
1331 /*
1332  * Sends a diagnostic message from the server to the client.  This message
1333  * can be sent at any time (but not while constructing another message). The
1334  * message is printed immediately, but only if the client is being executed
1335  * in verbose mode.  These messages are primarily intended to ease debugging
1336  * authentication problems.   The length of the formatted message must not
1337  * exceed 1024 bytes.  This will automatically call packet_write_wait.
1338  */
1339
1340 void
1341 packet_send_debug(const char *fmt,...)
1342 {
1343         char buf[1024];
1344         va_list args;
1345
1346         if (compat20 && (datafellows & SSH_BUG_DEBUG))
1347                 return;
1348
1349         va_start(args, fmt);
1350         vsnprintf(buf, sizeof(buf), fmt, args);
1351         va_end(args);
1352
1353         if (compat20) {
1354                 packet_start(SSH2_MSG_DEBUG);
1355                 packet_put_char(0);     /* bool: always display */
1356                 packet_put_cstring(buf);
1357                 packet_put_cstring("");
1358         } else {
1359                 packet_start(SSH_MSG_DEBUG);
1360                 packet_put_cstring(buf);
1361         }
1362         packet_send();
1363         packet_write_wait();
1364 }
1365
1366 /*
1367  * Logs the error plus constructs and sends a disconnect packet, closes the
1368  * connection, and exits.  This function never returns. The error message
1369  * should not contain a newline.  The length of the formatted message must
1370  * not exceed 1024 bytes.
1371  */
1372
1373 void
1374 packet_disconnect(const char *fmt,...)
1375 {
1376         char buf[1024];
1377         va_list args;
1378         static int disconnecting = 0;
1379
1380         if (disconnecting)      /* Guard against recursive invocations. */
1381                 fatal("packet_disconnect called recursively.");
1382         disconnecting = 1;
1383
1384         /*
1385          * Format the message.  Note that the caller must make sure the
1386          * message is of limited size.
1387          */
1388         va_start(args, fmt);
1389         vsnprintf(buf, sizeof(buf), fmt, args);
1390         va_end(args);
1391
1392         /* Display the error locally */
1393         logit("Disconnecting: %.100s", buf);
1394
1395         /* Send the disconnect message to the other side, and wait for it to get sent. */
1396         if (compat20) {
1397                 packet_start(SSH2_MSG_DISCONNECT);
1398                 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR);
1399                 packet_put_cstring(buf);
1400                 packet_put_cstring("");
1401         } else {
1402                 packet_start(SSH_MSG_DISCONNECT);
1403                 packet_put_cstring(buf);
1404         }
1405         packet_send();
1406         packet_write_wait();
1407
1408         /* Stop listening for connections. */
1409         channel_close_all();
1410
1411         /* Close the connection. */
1412         packet_close();
1413         cleanup_exit(255);
1414 }
1415
1416 /* Checks if there is any buffered output, and tries to write some of the output. */
1417
1418 void
1419 packet_write_poll(void)
1420 {
1421         int len = buffer_len(&output);
1422
1423         if (len > 0) {
1424                 len = write(connection_out, buffer_ptr(&output), len);
1425                 if (len <= 0) {
1426                         if (errno == EAGAIN)
1427                                 return;
1428                         else
1429                                 fatal("Write failed: %.100s", strerror(errno));
1430                 }
1431                 buffer_consume(&output, len);
1432         }
1433 }
1434
1435 /*
1436  * Calls packet_write_poll repeatedly until all pending output data has been
1437  * written.
1438  */
1439
1440 void
1441 packet_write_wait(void)
1442 {
1443         fd_set *setp;
1444
1445         setp = (fd_set *)xcalloc(howmany(connection_out + 1, NFDBITS),
1446             sizeof(fd_mask));
1447         packet_write_poll();
1448         while (packet_have_data_to_write()) {
1449                 memset(setp, 0, howmany(connection_out + 1, NFDBITS) *
1450                     sizeof(fd_mask));
1451                 FD_SET(connection_out, setp);
1452                 while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 &&
1453                     (errno == EAGAIN || errno == EINTR))
1454                         ;
1455                 packet_write_poll();
1456         }
1457         xfree(setp);
1458 }
1459
1460 /* Returns true if there is buffered data to write to the connection. */
1461
1462 int
1463 packet_have_data_to_write(void)
1464 {
1465         return buffer_len(&output) != 0;
1466 }
1467
1468 /* Returns true if there is not too much data to write to the connection. */
1469
1470 int
1471 packet_not_very_much_data_to_write(void)
1472 {
1473         if (interactive_mode)
1474                 return buffer_len(&output) < 16384;
1475         else
1476                 return buffer_len(&output) < 128 * 1024;
1477 }
1478
1479
1480 static void
1481 packet_set_tos(int interactive)
1482 {
1483 #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
1484         int tos = interactive ? IPTOS_LOWDELAY : IPTOS_THROUGHPUT;
1485
1486         if (!packet_connection_is_on_socket() ||
1487             !packet_connection_is_ipv4())
1488                 return;
1489         if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, &tos,
1490             sizeof(tos)) < 0)
1491                 error("setsockopt IP_TOS %d: %.100s:",
1492                     tos, strerror(errno));
1493 #endif
1494 }
1495
1496 /* Informs that the current session is interactive.  Sets IP flags for that. */
1497
1498 void
1499 packet_set_interactive(int interactive)
1500 {
1501         static int called = 0;
1502
1503         if (called)
1504                 return;
1505         called = 1;
1506
1507         /* Record that we are in interactive mode. */
1508         interactive_mode = interactive;
1509
1510         /* Only set socket options if using a socket.  */
1511         if (!packet_connection_is_on_socket())
1512                 return;
1513         set_nodelay(connection_in);
1514         packet_set_tos(interactive);
1515 }
1516
1517 /* Returns true if the current connection is interactive. */
1518
1519 int
1520 packet_is_interactive(void)
1521 {
1522         return interactive_mode;
1523 }
1524
1525 int
1526 packet_set_maxsize(u_int s)
1527 {
1528         static int called = 0;
1529
1530         if (called) {
1531                 logit("packet_set_maxsize: called twice: old %d new %d",
1532                     max_packet_size, s);
1533                 return -1;
1534         }
1535         if (s < 4 * 1024 || s > 1024 * 1024) {
1536                 logit("packet_set_maxsize: bad size %d", s);
1537                 return -1;
1538         }
1539         called = 1;
1540         debug("packet_set_maxsize: setting to %d", s);
1541         max_packet_size = s;
1542         return s;
1543 }
1544
1545 /* roundup current message to pad bytes */
1546 void
1547 packet_add_padding(u_char pad)
1548 {
1549         extra_pad = pad;
1550 }
1551
1552 /*
1553  * 9.2.  Ignored Data Message
1554  *
1555  *   byte      SSH_MSG_IGNORE
1556  *   string    data
1557  *
1558  * All implementations MUST understand (and ignore) this message at any
1559  * time (after receiving the protocol version). No implementation is
1560  * required to send them. This message can be used as an additional
1561  * protection measure against advanced traffic analysis techniques.
1562  */
1563 void
1564 packet_send_ignore(int nbytes)
1565 {
1566         u_int32_t rnd = 0;
1567         int i;
1568
1569         packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE);
1570         packet_put_int(nbytes);
1571         for (i = 0; i < nbytes; i++) {
1572                 if (i % 4 == 0)
1573                         rnd = arc4random();
1574                 packet_put_char((u_char)rnd & 0xff);
1575                 rnd >>= 8;
1576         }
1577 }
1578
1579 #define MAX_PACKETS     (1U<<31)
1580 int
1581 packet_need_rekeying(void)
1582 {
1583         if (datafellows & SSH_BUG_NOREKEY)
1584                 return 0;
1585         return
1586             (p_send.packets > MAX_PACKETS) ||
1587             (p_read.packets > MAX_PACKETS) ||
1588             (max_blocks_out && (p_send.blocks > max_blocks_out)) ||
1589             (max_blocks_in  && (p_read.blocks > max_blocks_in));
1590 }
1591
1592 void
1593 packet_set_rekey_limit(u_int32_t bytes)
1594 {
1595         rekey_limit = bytes;
1596 }
1597
1598 void
1599 packet_set_server(void)
1600 {
1601         server_side = 1;
1602 }
1603
1604 void
1605 packet_set_authenticated(void)
1606 {
1607         after_authentication = 1;
1608 }