crypto/external/bsd/openssh/dist/kex.c

   1 /*      $NetBSD: kex.c,v 1.1.1.2 2009/12/27 01:06:55 christos Exp $     */
   2 /* $OpenBSD: kex.c,v 1.81 2009/05/27 06:34:36 andreas Exp $ */
   3 /*
   4  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28 __RCSID("$NetBSD: kex.c,v 1.2 2009/06/07 22:38:46 christos Exp $");
  29 #include <sys/param.h>
  30
  31 #include <signal.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35
  36 #include <openssl/crypto.h>
  37
  38 #include "xmalloc.h"
  39 #include "ssh2.h"
  40 #include "buffer.h"
  41 #include "packet.h"
  42 #include "compat.h"
  43 #include "cipher.h"
  44 #include "key.h"
  45 #include "kex.h"
  46 #include "log.h"
  47 #include "mac.h"
  48 #include "match.h"
  49 #include "dispatch.h"
  50 #include "monitor.h"
  51 #include "canohost.h"
  52
  53 /* prototype */
  54 static void kex_kexinit_finish(Kex *);
  55 static void kex_choose_conf(Kex *);
  56
  57 /* put algorithm proposal into buffer */
  58 void
  59 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
  60 {
  61         u_int i;
  62
  63         buffer_clear(b);
  64         /*
  65          * add a dummy cookie, the cookie will be overwritten by
  66          * kex_send_kexinit(), each time a kexinit is set
  67          */
  68         for (i = 0; i < KEX_COOKIE_LEN; i++)
  69                 buffer_put_char(b, 0);
  70         for (i = 0; i < PROPOSAL_MAX; i++)
  71                 buffer_put_cstring(b, proposal[i]);
  72         buffer_put_char(b, 0);                  /* first_kex_packet_follows */
  73         buffer_put_int(b, 0);                   /* uint32 reserved */
  74 }
  75
  76 /* parse buffer and return algorithm proposal */
  77 static char **
  78 kex_buf2prop(Buffer *raw, int *first_kex_follows)
  79 {
  80         Buffer b;
  81         u_int i;
  82         char **proposal;
  83
  84         proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
  85
  86         buffer_init(&b);
  87         buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
  88         /* skip cookie */
  89         for (i = 0; i < KEX_COOKIE_LEN; i++)
  90                 buffer_get_char(&b);
  91         /* extract kex init proposal strings */
  92         for (i = 0; i < PROPOSAL_MAX; i++) {
  93                 proposal[i] = buffer_get_string(&b,NULL);
  94                 debug2("kex_parse_kexinit: %s", proposal[i]);
  95         }
  96         /* first kex follows / reserved */
  97         i = buffer_get_char(&b);
  98         if (first_kex_follows != NULL)
  99                 *first_kex_follows = i;
 100         debug2("kex_parse_kexinit: first_kex_follows %d ", i);
 101         i = buffer_get_int(&b);
 102         debug2("kex_parse_kexinit: reserved %u ", i);
 103         buffer_free(&b);
 104         return proposal;
 105 }
 106
 107 static void
 108 kex_prop_free(char **proposal)
 109 {
 110         u_int i;
 111
 112         for (i = 0; i < PROPOSAL_MAX; i++)
 113                 xfree(proposal[i]);
 114         xfree(proposal);
 115 }
 116
 117 /* ARGSUSED */
 118 static void
 119 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
 120 {
 121         error("Hm, kex protocol error: type %d seq %u", type, seq);
 122 }
 123
 124 static void
 125 kex_reset_dispatch(void)
 126 {
 127         dispatch_range(SSH2_MSG_TRANSPORT_MIN,
 128             SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
 129         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 130 }
 131
 132 void
 133 kex_finish(Kex *kex)
 134 {
 135         kex_reset_dispatch();
 136
 137         packet_start(SSH2_MSG_NEWKEYS);
 138         packet_send();
 139         /* packet_write_wait(); */
 140         debug("SSH2_MSG_NEWKEYS sent");
 141
 142         debug("expecting SSH2_MSG_NEWKEYS");
 143         packet_read_expect(SSH2_MSG_NEWKEYS);
 144         packet_check_eom();
 145         debug("SSH2_MSG_NEWKEYS received");
 146
 147         kex->done = 1;
 148         buffer_clear(&kex->peer);
 149         /* buffer_clear(&kex->my); */
 150         kex->flags &= ~KEX_INIT_SENT;
 151         xfree(kex->name);
 152         kex->name = NULL;
 153 }
 154
 155 void
 156 kex_send_kexinit(Kex *kex)
 157 {
 158         u_int32_t rnd = 0;
 159         u_char *cookie;
 160         u_int i;
 161
 162         if (kex == NULL) {
 163                 error("kex_send_kexinit: no kex, cannot rekey");
 164                 return;
 165         }
 166         if (kex->flags & KEX_INIT_SENT) {
 167                 debug("KEX_INIT_SENT");
 168                 return;
 169         }
 170         kex->done = 0;
 171
 172         /* generate a random cookie */
 173         if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
 174                 fatal("kex_send_kexinit: kex proposal too short");
 175         cookie = buffer_ptr(&kex->my);
 176         for (i = 0; i < KEX_COOKIE_LEN; i++) {
 177                 if (i % 4 == 0)
 178                         rnd = arc4random();
 179                 cookie[i] = rnd;
 180                 rnd >>= 8;
 181         }
 182         packet_start(SSH2_MSG_KEXINIT);
 183         packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
 184         packet_send();
 185         debug("SSH2_MSG_KEXINIT sent");
 186         kex->flags |= KEX_INIT_SENT;
 187 }
 188
 189 /* ARGSUSED */
 190 void
 191 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
 192 {
 193         char *ptr;
 194         u_int i, dlen;
 195         Kex *kex = (Kex *)ctxt;
 196
 197         debug("SSH2_MSG_KEXINIT received");
 198         if (kex == NULL)
 199                 fatal("kex_input_kexinit: no kex, cannot rekey");
 200
 201         ptr = packet_get_raw(&dlen);
 202         buffer_append(&kex->peer, ptr, dlen);
 203
 204         /* discard packet */
 205         for (i = 0; i < KEX_COOKIE_LEN; i++)
 206                 packet_get_char();
 207         for (i = 0; i < PROPOSAL_MAX; i++)
 208                 xfree(packet_get_string(NULL));
 209         (void) packet_get_char();
 210         (void) packet_get_int();
 211         packet_check_eom();
 212
 213         kex_kexinit_finish(kex);
 214 }
 215
 216 Kex *
 217 kex_setup(char *proposal[PROPOSAL_MAX])
 218 {
 219         Kex *kex;
 220
 221         kex = xcalloc(1, sizeof(*kex));
 222         buffer_init(&kex->peer);
 223         buffer_init(&kex->my);
 224         kex_prop2buf(&kex->my, proposal);
 225         kex->done = 0;
 226
 227         kex_send_kexinit(kex);                                  /* we start */
 228         kex_reset_dispatch();
 229
 230         return kex;
 231 }
 232
 233 static void
 234 kex_kexinit_finish(Kex *kex)
 235 {
 236         if (!(kex->flags & KEX_INIT_SENT))
 237                 kex_send_kexinit(kex);
 238
 239         kex_choose_conf(kex);
 240
 241         if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
 242             kex->kex[kex->kex_type] != NULL) {
 243                 (kex->kex[kex->kex_type])(kex);
 244         } else {
 245                 fatal("Unsupported key exchange %d", kex->kex_type);
 246         }
 247 }
 248
 249 static void
 250 choose_enc(Enc *enc, char *client, char *server)
 251 {
 252         char *name = match_list(client, server, NULL);
 253         if (name == NULL)
 254                 fatal("no matching cipher found: client %s server %s",
 255                     client, server);
 256         if ((enc->cipher = cipher_by_name(name)) == NULL)
 257                 fatal("matching cipher is not supported: %s", name);
 258         enc->name = name;
 259         enc->enabled = 0;
 260         enc->iv = NULL;
 261         enc->key = NULL;
 262         enc->key_len = cipher_keylen(enc->cipher);
 263         enc->block_size = cipher_blocksize(enc->cipher);
 264 }
 265
 266 static void
 267 choose_mac(Mac *mac, char *client, char *server)
 268 {
 269         char *name = match_list(client, server, NULL);
 270         if (name == NULL)
 271                 fatal("no matching mac found: client %s server %s",
 272                     client, server);
 273         if (mac_setup(mac, name) < 0)
 274                 fatal("unsupported mac %s", name);
 275         /* truncate the key */
 276         if (datafellows & SSH_BUG_HMAC)
 277                 mac->key_len = 16;
 278         mac->name = name;
 279         mac->key = NULL;
 280         mac->enabled = 0;
 281 }
 282
 283 static void
 284 choose_comp(Comp *comp, char *client, char *server)
 285 {
 286         char *name = match_list(client, server, NULL);
 287         if (name == NULL)
 288                 fatal("no matching comp found: client %s server %s", client, server);
 289         if (strcmp(name, "zlib@openssh.com") == 0) {
 290                 comp->type = COMP_DELAYED;
 291         } else if (strcmp(name, "zlib") == 0) {
 292                 comp->type = COMP_ZLIB;
 293         } else if (strcmp(name, "none") == 0) {
 294                 comp->type = COMP_NONE;
 295         } else {
 296                 fatal("unsupported comp %s", name);
 297         }
 298         comp->name = name;
 299 }
 300
 301 static void
 302 choose_kex(Kex *k, char *client, char *server)
 303 {
 304         k->name = match_list(client, server, NULL);
 305         if (k->name == NULL)
 306                 fatal("Unable to negotiate a key exchange method");
 307         if (strcmp(k->name, KEX_DH1) == 0) {
 308                 k->kex_type = KEX_DH_GRP1_SHA1;
 309                 k->evp_md = EVP_sha1();
 310         } else if (strcmp(k->name, KEX_DH14) == 0) {
 311                 k->kex_type = KEX_DH_GRP14_SHA1;
 312                 k->evp_md = EVP_sha1();
 313         } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
 314                 k->kex_type = KEX_DH_GEX_SHA1;
 315                 k->evp_md = EVP_sha1();
 316         } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
 317                 k->kex_type = KEX_DH_GEX_SHA256;
 318                 k->evp_md = EVP_sha256();
 319         } else
 320                 fatal("bad kex alg %s", k->name);
 321 }
 322
 323 static void
 324 choose_hostkeyalg(Kex *k, char *client, char *server)
 325 {
 326         char *hostkeyalg = match_list(client, server, NULL);
 327         if (hostkeyalg == NULL)
 328                 fatal("no hostkey alg");
 329         k->hostkey_type = key_type_from_name(hostkeyalg);
 330         if (k->hostkey_type == KEY_UNSPEC)
 331                 fatal("bad hostkey alg '%s'", hostkeyalg);
 332         xfree(hostkeyalg);
 333 }
 334
 335 static int
 336 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
 337 {
 338         static int check[] = {
 339                 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
 340         };
 341         int *idx;
 342         char *p;
 343
 344         for (idx = &check[0]; *idx != -1; idx++) {
 345                 if ((p = strchr(my[*idx], ',')) != NULL)
 346                         *p = '\0';
 347                 if ((p = strchr(peer[*idx], ',')) != NULL)
 348                         *p = '\0';
 349                 if (strcmp(my[*idx], peer[*idx]) != 0) {
 350                         debug2("proposal mismatch: my %s peer %s",
 351                             my[*idx], peer[*idx]);
 352                         return (0);
 353                 }
 354         }
 355         debug2("proposals match");
 356         return (1);
 357 }
 358
 359 static void
 360 kex_choose_conf(Kex *kex)
 361 {
 362         Newkeys *newkeys;
 363         char **my, **peer;
 364         char **cprop, **sprop;
 365         int nenc, nmac, ncomp;
 366         u_int mode, ctos, need;
 367         int first_kex_follows, type;
 368         int log_flag = 0;
 369
 370         int auth_flag;
 371
 372         auth_flag = packet_authentication_state();
 373
 374         debug ("AUTH STATE IS %d", auth_flag);
 375
 376         my   = kex_buf2prop(&kex->my, NULL);
 377         peer = kex_buf2prop(&kex->peer, &first_kex_follows);
 378
 379         if (kex->server) {
 380                 cprop=peer;
 381                 sprop=my;
 382         } else {
 383                 cprop=my;
 384                 sprop=peer;
 385         }
 386
 387         /* Algorithm Negotiation */
 388         for (mode = 0; mode < MODE_MAX; mode++) {
 389                 newkeys = xcalloc(1, sizeof(*newkeys));
 390                 kex->newkeys[mode] = newkeys;
 391                 ctos = (!kex->server && mode == MODE_OUT) ||
 392                     (kex->server && mode == MODE_IN);
 393                 nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
 394                 nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
 395                 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
 396                 choose_enc (&newkeys->enc,  cprop[nenc],  sprop[nenc]);
 397                 choose_mac (&newkeys->mac,  cprop[nmac],  sprop[nmac]);
 398                 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
 399                 debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
 400                 if (strcmp(newkeys->enc.name, "none") == 0) {
 401                                 debug("Requesting NONE. Authflag is %d", auth_flag);
 402                         if (auth_flag == 1) {
 403                                 debug("None requested post authentication.");
 404                         } else {
 405                                 fatal("Pre-authentication none cipher requests are not allowed.");
 406                         }
 407                 }
 408                 debug("kex: %s %s %s %s",
 409                     ctos ? "client->server" : "server->client",
 410                     newkeys->enc.name,
 411                     newkeys->mac.name,
 412                     newkeys->comp.name);
 413                 /* client starts withctos = 0 && log flag = 0 and no log*/
 414                 /* 2nd client pass ctos=1 and flag = 1 so no log*/
 415                 /* server starts with ctos =1 && log_flag = 0 so log */
 416                 /* 2nd sever pass ctos = 1 && log flag = 1 so no log*/
 417                 /* -cjr*/
 418                 if (ctos && !log_flag) {
 419                         logit("SSH: Server;Ltype: Kex;Remote: %s-%d;Enc: %s;MAC: %s;Comp: %s",
 420                               get_remote_ipaddr(),
 421                               get_remote_port(),
 422                               newkeys->enc.name,
 423                               newkeys->mac.name,
 424                               newkeys->comp.name);
 425                 }
 426                 log_flag = 1;
 427         }
 428         choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
 429         choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
 430             sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
 431         need = 0;
 432         for (mode = 0; mode < MODE_MAX; mode++) {
 433                 newkeys = kex->newkeys[mode];
 434                 if (need < newkeys->enc.key_len)
 435                         need = newkeys->enc.key_len;
 436                 if (need < newkeys->enc.block_size)
 437                         need = newkeys->enc.block_size;
 438                 if (need < newkeys->mac.key_len)
 439                         need = newkeys->mac.key_len;
 440         }
 441         /* XXX need runden? */
 442         kex->we_need = need;
 443
 444         /* ignore the next message if the proposals do not match */
 445         if (first_kex_follows && !proposals_match(my, peer) &&
 446             !(datafellows & SSH_BUG_FIRSTKEX)) {
 447                 type = packet_read();
 448                 debug2("skipping next packet (type %u)", type);
 449         }
 450
 451         kex_prop_free(my);
 452         kex_prop_free(peer);
 453 }
 454
 455 static u_char *
 456 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
 457     BIGNUM *shared_secret)
 458 {
 459         Buffer b;
 460         EVP_MD_CTX md;
 461         char c = id;
 462         u_int have;
 463         int mdsz;
 464         u_char *digest;
 465
 466         if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
 467                 fatal("bad kex md size %d", mdsz);
 468         digest = xmalloc(roundup(need, mdsz));
 469
 470         buffer_init(&b);
 471         buffer_put_bignum2(&b, shared_secret);
 472
 473         /* K1 = HASH(K || H || "A" || session_id) */
 474         EVP_DigestInit(&md, kex->evp_md);
 475         if (!(datafellows & SSH_BUG_DERIVEKEY))
 476                 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
 477         EVP_DigestUpdate(&md, hash, hashlen);
 478         EVP_DigestUpdate(&md, &c, 1);
 479         EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
 480         EVP_DigestFinal(&md, digest, NULL);
 481
 482         /*
 483          * expand key:
 484          * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
 485          * Key = K1 || K2 || ... || Kn
 486          */
 487         for (have = mdsz; need > have; have += mdsz) {
 488                 EVP_DigestInit(&md, kex->evp_md);
 489                 if (!(datafellows & SSH_BUG_DERIVEKEY))
 490                         EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
 491                 EVP_DigestUpdate(&md, hash, hashlen);
 492                 EVP_DigestUpdate(&md, digest, have);
 493                 EVP_DigestFinal(&md, digest + have, NULL);
 494         }
 495         buffer_free(&b);
 496 #ifdef DEBUG_KEX
 497         fprintf(stderr, "key '%c'== ", c);
 498         dump_digest("key", digest, need);
 499 #endif
 500         return digest;
 501 }
 502
 503 Newkeys *current_keys[MODE_MAX];
 504
 505 #define NKEYS   6
 506 void
 507 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
 508 {
 509         u_char *keys[NKEYS];
 510         u_int i, mode, ctos;
 511
 512         for (i = 0; i < NKEYS; i++) {
 513                 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
 514                     shared_secret);
 515         }
 516
 517         debug2("kex_derive_keys");
 518         for (mode = 0; mode < MODE_MAX; mode++) {
 519                 current_keys[mode] = kex->newkeys[mode];
 520                 kex->newkeys[mode] = NULL;
 521                 ctos = (!kex->server && mode == MODE_OUT) ||
 522                     (kex->server && mode == MODE_IN);
 523                 current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
 524                 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
 525                 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
 526         }
 527 }
 528
 529 Newkeys *
 530 kex_get_newkeys(int mode)
 531 {
 532         Newkeys *ret;
 533
 534         ret = current_keys[mode];
 535         current_keys[mode] = NULL;
 536         return ret;
 537 }
 538
 539 void
 540 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
 541     u_int8_t cookie[8], u_int8_t id[16])
 542 {
 543         const EVP_MD *evp_md = EVP_md5();
 544         EVP_MD_CTX md;
 545         u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
 546         int len;
 547
 548         EVP_DigestInit(&md, evp_md);
 549
 550         len = BN_num_bytes(host_modulus);
 551         if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
 552                 fatal("%s: bad host modulus (len %d)", __func__, len);
 553         BN_bn2bin(host_modulus, nbuf);
 554         EVP_DigestUpdate(&md, nbuf, len);
 555
 556         len = BN_num_bytes(server_modulus);
 557         if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
 558                 fatal("%s: bad server modulus (len %d)", __func__, len);
 559         BN_bn2bin(server_modulus, nbuf);
 560         EVP_DigestUpdate(&md, nbuf, len);
 561
 562         EVP_DigestUpdate(&md, cookie, 8);
 563
 564         EVP_DigestFinal(&md, obuf, NULL);
 565         memcpy(id, obuf, 16);
 566
 567         memset(nbuf, 0, sizeof(nbuf));
 568         memset(obuf, 0, sizeof(obuf));
 569         memset(&md, 0, sizeof(md));
 570 }
 571
 572 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
 573 void
 574 dump_digest(char *msg, u_char *digest, int len)
 575 {
 576         u_int i;
 577
 578         fprintf(stderr, "%s\n", msg);
 579         for (i = 0; i < len; i++) {
 580                 fprintf(stderr, "%02x", digest[i]);
 581                 if (i%32 == 31)
 582                         fprintf(stderr, "\n");
 583                 else if (i%8 == 7)
 584                         fprintf(stderr, " ");
 585         }
 586         fprintf(stderr, "\n");
 587 }
 588 #endif