crypto/openssh/kex.c

   1 /* $OpenBSD: kex.c,v 1.99 2014/04/29 18:01:49 markus Exp $ */
   2 /*
   3  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "includes.h"
  27
  28 #include <sys/param.h>
  29
  30 #include <signal.h>
  31 #include <stdarg.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35
  36 #ifdef WITH_OPENSSL
  37 #include <openssl/crypto.h>
  38 #endif
  39
  40 #include "xmalloc.h"
  41 #include "ssh2.h"
  42 #include "buffer.h"
  43 #include "packet.h"
  44 #include "compat.h"
  45 #include "cipher.h"
  46 #include "key.h"
  47 #include "kex.h"
  48 #include "log.h"
  49 #include "mac.h"
  50 #include "match.h"
  51 #include "dispatch.h"
  52 #include "monitor.h"
  53 #include "roaming.h"
  54 #include "digest.h"
  55
  56 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
  57 # if defined(HAVE_EVP_SHA256)
  58 # define evp_ssh_sha256 EVP_sha256
  59 # else
  60 extern const EVP_MD *evp_ssh_sha256(void);
  61 # endif
  62 #endif
  63
  64 /* prototype */
  65 static void kex_kexinit_finish(Kex *);
  66 static void kex_choose_conf(Kex *);
  67
  68 struct kexalg {
  69         char *name;
  70         int type;
  71         int ec_nid;
  72         int hash_alg;
  73 };
  74 static const struct kexalg kexalgs[] = {
  75 #ifdef WITH_OPENSSL
  76         { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
  77         { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
  78         { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
  79 #ifdef HAVE_EVP_SHA256
  80         { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
  81 #endif /* HAVE_EVP_SHA256 */
  82 #ifdef OPENSSL_HAS_ECC
  83         { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
  84             NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
  85         { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
  86             SSH_DIGEST_SHA384 },
  87 # ifdef OPENSSL_HAS_NISTP521
  88         { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
  89             SSH_DIGEST_SHA512 },
  90 # endif /* OPENSSL_HAS_NISTP521 */
  91 #endif /* OPENSSL_HAS_ECC */
  92         { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
  93 #endif /* WITH_OPENSSL */
  94 #ifdef HAVE_EVP_SHA256
  95         { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
  96 #endif /* HAVE_EVP_SHA256 */
  97         { NULL, -1, -1, -1},
  98 };
  99
 100 char *
 101 kex_alg_list(char sep)
 102 {
 103         char *ret = NULL;
 104         size_t nlen, rlen = 0;
 105         const struct kexalg *k;
 106
 107         for (k = kexalgs; k->name != NULL; k++) {
 108                 if (ret != NULL)
 109                         ret[rlen++] = sep;
 110                 nlen = strlen(k->name);
 111                 ret = xrealloc(ret, 1, rlen + nlen + 2);
 112                 memcpy(ret + rlen, k->name, nlen + 1);
 113                 rlen += nlen;
 114         }
 115         return ret;
 116 }
 117
 118 static const struct kexalg *
 119 kex_alg_by_name(const char *name)
 120 {
 121         const struct kexalg *k;
 122
 123         for (k = kexalgs; k->name != NULL; k++) {
 124                 if (strcmp(k->name, name) == 0)
 125                         return k;
 126         }
 127         return NULL;
 128 }
 129
 130 /* Validate KEX method name list */
 131 int
 132 kex_names_valid(const char *names)
 133 {
 134         char *s, *cp, *p;
 135
 136         if (names == NULL || strcmp(names, "") == 0)
 137                 return 0;
 138         s = cp = xstrdup(names);
 139         for ((p = strsep(&cp, ",")); p && *p != '\0';
 140             (p = strsep(&cp, ","))) {
 141                 if (kex_alg_by_name(p) == NULL) {
 142                         error("Unsupported KEX algorithm \"%.100s\"", p);
 143                         free(s);
 144                         return 0;
 145                 }
 146         }
 147         debug3("kex names ok: [%s]", names);
 148         free(s);
 149         return 1;
 150 }
 151
 152 /* put algorithm proposal into buffer */
 153 static void
 154 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
 155 {
 156         u_int i;
 157
 158         buffer_clear(b);
 159         /*
 160          * add a dummy cookie, the cookie will be overwritten by
 161          * kex_send_kexinit(), each time a kexinit is set
 162          */
 163         for (i = 0; i < KEX_COOKIE_LEN; i++)
 164                 buffer_put_char(b, 0);
 165         for (i = 0; i < PROPOSAL_MAX; i++)
 166                 buffer_put_cstring(b, proposal[i]);
 167         buffer_put_char(b, 0);                  /* first_kex_packet_follows */
 168         buffer_put_int(b, 0);                   /* uint32 reserved */
 169 }
 170
 171 /* parse buffer and return algorithm proposal */
 172 static char **
 173 kex_buf2prop(Buffer *raw, int *first_kex_follows)
 174 {
 175         Buffer b;
 176         u_int i;
 177         char **proposal;
 178
 179         proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
 180
 181         buffer_init(&b);
 182         buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
 183         /* skip cookie */
 184         for (i = 0; i < KEX_COOKIE_LEN; i++)
 185                 buffer_get_char(&b);
 186         /* extract kex init proposal strings */
 187         for (i = 0; i < PROPOSAL_MAX; i++) {
 188                 proposal[i] = buffer_get_cstring(&b,NULL);
 189                 debug2("kex_parse_kexinit: %s", proposal[i]);
 190         }
 191         /* first kex follows / reserved */
 192         i = buffer_get_char(&b);
 193         if (first_kex_follows != NULL)
 194                 *first_kex_follows = i;
 195         debug2("kex_parse_kexinit: first_kex_follows %d ", i);
 196         i = buffer_get_int(&b);
 197         debug2("kex_parse_kexinit: reserved %u ", i);
 198         buffer_free(&b);
 199         return proposal;
 200 }
 201
 202 static void
 203 kex_prop_free(char **proposal)
 204 {
 205         u_int i;
 206
 207         for (i = 0; i < PROPOSAL_MAX; i++)
 208                 free(proposal[i]);
 209         free(proposal);
 210 }
 211
 212 /* ARGSUSED */
 213 static void
 214 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
 215 {
 216         error("Hm, kex protocol error: type %d seq %u", type, seq);
 217 }
 218
 219 static void
 220 kex_reset_dispatch(void)
 221 {
 222         dispatch_range(SSH2_MSG_TRANSPORT_MIN,
 223             SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
 224         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 225 }
 226
 227 void
 228 kex_finish(Kex *kex)
 229 {
 230         kex_reset_dispatch();
 231
 232         packet_start(SSH2_MSG_NEWKEYS);
 233         packet_send();
 234         /* packet_write_wait(); */
 235         debug("SSH2_MSG_NEWKEYS sent");
 236
 237         debug("expecting SSH2_MSG_NEWKEYS");
 238         packet_read_expect(SSH2_MSG_NEWKEYS);
 239         packet_check_eom();
 240         debug("SSH2_MSG_NEWKEYS received");
 241
 242         kex->done = 1;
 243         buffer_clear(&kex->peer);
 244         /* buffer_clear(&kex->my); */
 245         kex->flags &= ~KEX_INIT_SENT;
 246         free(kex->name);
 247         kex->name = NULL;
 248 }
 249
 250 void
 251 kex_send_kexinit(Kex *kex)
 252 {
 253         u_int32_t rnd = 0;
 254         u_char *cookie;
 255         u_int i;
 256
 257         if (kex == NULL) {
 258                 error("kex_send_kexinit: no kex, cannot rekey");
 259                 return;
 260         }
 261         if (kex->flags & KEX_INIT_SENT) {
 262                 debug("KEX_INIT_SENT");
 263                 return;
 264         }
 265         kex->done = 0;
 266
 267         /* generate a random cookie */
 268         if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
 269                 fatal("kex_send_kexinit: kex proposal too short");
 270         cookie = buffer_ptr(&kex->my);
 271         for (i = 0; i < KEX_COOKIE_LEN; i++) {
 272                 if (i % 4 == 0)
 273                         rnd = arc4random();
 274                 cookie[i] = rnd;
 275                 rnd >>= 8;
 276         }
 277         packet_start(SSH2_MSG_KEXINIT);
 278         packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
 279         packet_send();
 280         debug("SSH2_MSG_KEXINIT sent");
 281         kex->flags |= KEX_INIT_SENT;
 282 }
 283
 284 /* ARGSUSED */
 285 void
 286 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
 287 {
 288         char *ptr;
 289         u_int i, dlen;
 290         Kex *kex = (Kex *)ctxt;
 291
 292         debug("SSH2_MSG_KEXINIT received");
 293         if (kex == NULL)
 294                 fatal("kex_input_kexinit: no kex, cannot rekey");
 295
 296         ptr = packet_get_raw(&dlen);
 297         buffer_append(&kex->peer, ptr, dlen);
 298
 299         /* discard packet */
 300         for (i = 0; i < KEX_COOKIE_LEN; i++)
 301                 packet_get_char();
 302         for (i = 0; i < PROPOSAL_MAX; i++)
 303                 free(packet_get_string(NULL));
 304         /*
 305          * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
 306          * KEX method has the server move first, but a server might be using
 307          * a custom method or one that we otherwise don't support. We should
 308          * be prepared to remember first_kex_follows here so we can eat a
 309          * packet later.
 310          * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
 311          * for cases where the server *doesn't* go first. I guess we should
 312          * ignore it when it is set for these cases, which is what we do now.
 313          */
 314         (void) packet_get_char();       /* first_kex_follows */
 315         (void) packet_get_int();        /* reserved */
 316         packet_check_eom();
 317
 318         kex_kexinit_finish(kex);
 319 }
 320
 321 Kex *
 322 kex_setup(char *proposal[PROPOSAL_MAX])
 323 {
 324         Kex *kex;
 325
 326         kex = xcalloc(1, sizeof(*kex));
 327         buffer_init(&kex->peer);
 328         buffer_init(&kex->my);
 329         kex_prop2buf(&kex->my, proposal);
 330         kex->done = 0;
 331
 332         kex_send_kexinit(kex);                                  /* we start */
 333         kex_reset_dispatch();
 334
 335         return kex;
 336 }
 337
 338 static void
 339 kex_kexinit_finish(Kex *kex)
 340 {
 341         if (!(kex->flags & KEX_INIT_SENT))
 342                 kex_send_kexinit(kex);
 343
 344         kex_choose_conf(kex);
 345
 346         if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
 347             kex->kex[kex->kex_type] != NULL) {
 348                 (kex->kex[kex->kex_type])(kex);
 349         } else {
 350                 fatal("Unsupported key exchange %d", kex->kex_type);
 351         }
 352 }
 353
 354 static void
 355 choose_enc(Enc *enc, char *client, char *server)
 356 {
 357         char *name = match_list(client, server, NULL);
 358         if (name == NULL)
 359                 fatal("no matching cipher found: client %s server %s",
 360                     client, server);
 361         if ((enc->cipher = cipher_by_name(name)) == NULL)
 362                 fatal("matching cipher is not supported: %s", name);
 363         enc->name = name;
 364         enc->enabled = 0;
 365         enc->iv = NULL;
 366         enc->iv_len = cipher_ivlen(enc->cipher);
 367         enc->key = NULL;
 368         enc->key_len = cipher_keylen(enc->cipher);
 369         enc->block_size = cipher_blocksize(enc->cipher);
 370 }
 371
 372 static void
 373 choose_mac(Mac *mac, char *client, char *server)
 374 {
 375         char *name = match_list(client, server, NULL);
 376         if (name == NULL)
 377                 fatal("no matching mac found: client %s server %s",
 378                     client, server);
 379         if (mac_setup(mac, name) < 0)
 380                 fatal("unsupported mac %s", name);
 381         /* truncate the key */
 382         if (datafellows & SSH_BUG_HMAC)
 383                 mac->key_len = 16;
 384         mac->name = name;
 385         mac->key = NULL;
 386         mac->enabled = 0;
 387 }
 388
 389 static void
 390 choose_comp(Comp *comp, char *client, char *server)
 391 {
 392         char *name = match_list(client, server, NULL);
 393         if (name == NULL)
 394                 fatal("no matching comp found: client %s server %s", client, server);
 395         if (strcmp(name, "zlib@openssh.com") == 0) {
 396                 comp->type = COMP_DELAYED;
 397         } else if (strcmp(name, "zlib") == 0) {
 398                 comp->type = COMP_ZLIB;
 399         } else if (strcmp(name, "none") == 0) {
 400                 comp->type = COMP_NONE;
 401         } else {
 402                 fatal("unsupported comp %s", name);
 403         }
 404         comp->name = name;
 405 }
 406
 407 static void
 408 choose_kex(Kex *k, char *client, char *server)
 409 {
 410         const struct kexalg *kexalg;
 411
 412         k->name = match_list(client, server, NULL);
 413         if (k->name == NULL)
 414                 fatal("Unable to negotiate a key exchange method");
 415         if ((kexalg = kex_alg_by_name(k->name)) == NULL)
 416                 fatal("unsupported kex alg %s", k->name);
 417         k->kex_type = kexalg->type;
 418         k->hash_alg = kexalg->hash_alg;
 419         k->ec_nid = kexalg->ec_nid;
 420 }
 421
 422 static void
 423 choose_hostkeyalg(Kex *k, char *client, char *server)
 424 {
 425         char *hostkeyalg = match_list(client, server, NULL);
 426         if (hostkeyalg == NULL)
 427                 fatal("no hostkey alg");
 428         k->hostkey_type = key_type_from_name(hostkeyalg);
 429         if (k->hostkey_type == KEY_UNSPEC)
 430                 fatal("bad hostkey alg '%s'", hostkeyalg);
 431         free(hostkeyalg);
 432 }
 433
 434 static int
 435 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
 436 {
 437         static int check[] = {
 438                 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
 439         };
 440         int *idx;
 441         char *p;
 442
 443         for (idx = &check[0]; *idx != -1; idx++) {
 444                 if ((p = strchr(my[*idx], ',')) != NULL)
 445                         *p = '\0';
 446                 if ((p = strchr(peer[*idx], ',')) != NULL)
 447                         *p = '\0';
 448                 if (strcmp(my[*idx], peer[*idx]) != 0) {
 449                         debug2("proposal mismatch: my %s peer %s",
 450                             my[*idx], peer[*idx]);
 451                         return (0);
 452                 }
 453         }
 454         debug2("proposals match");
 455         return (1);
 456 }
 457
 458 static void
 459 kex_choose_conf(Kex *kex)
 460 {
 461         Newkeys *newkeys;
 462         char **my, **peer;
 463         char **cprop, **sprop;
 464         int nenc, nmac, ncomp;
 465         u_int mode, ctos, need, dh_need, authlen;
 466         int first_kex_follows, type;
 467
 468         my   = kex_buf2prop(&kex->my, NULL);
 469         peer = kex_buf2prop(&kex->peer, &first_kex_follows);
 470
 471         if (kex->server) {
 472                 cprop=peer;
 473                 sprop=my;
 474         } else {
 475                 cprop=my;
 476                 sprop=peer;
 477         }
 478
 479         /* Check whether server offers roaming */
 480         if (!kex->server) {
 481                 char *roaming;
 482                 roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
 483                 if (roaming) {
 484                         kex->roaming = 1;
 485                         free(roaming);
 486                 }
 487         }
 488
 489         /* Algorithm Negotiation */
 490         for (mode = 0; mode < MODE_MAX; mode++) {
 491                 newkeys = xcalloc(1, sizeof(*newkeys));
 492                 kex->newkeys[mode] = newkeys;
 493                 ctos = (!kex->server && mode == MODE_OUT) ||
 494                     (kex->server && mode == MODE_IN);
 495                 nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
 496                 nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
 497                 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
 498                 choose_enc(&newkeys->enc, cprop[nenc], sprop[nenc]);
 499                 /* ignore mac for authenticated encryption */
 500                 authlen = cipher_authlen(newkeys->enc.cipher);
 501                 if (authlen == 0)
 502                         choose_mac(&newkeys->mac, cprop[nmac], sprop[nmac]);
 503                 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
 504                 debug("kex: %s %s %s %s",
 505                     ctos ? "client->server" : "server->client",
 506                     newkeys->enc.name,
 507                     authlen == 0 ? newkeys->mac.name : "<implicit>",
 508                     newkeys->comp.name);
 509         }
 510         choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
 511         choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
 512             sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
 513         need = dh_need = 0;
 514         for (mode = 0; mode < MODE_MAX; mode++) {
 515                 newkeys = kex->newkeys[mode];
 516                 need = MAX(need, newkeys->enc.key_len);
 517                 need = MAX(need, newkeys->enc.block_size);
 518                 need = MAX(need, newkeys->enc.iv_len);
 519                 need = MAX(need, newkeys->mac.key_len);
 520                 dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
 521                 dh_need = MAX(dh_need, newkeys->enc.block_size);
 522                 dh_need = MAX(dh_need, newkeys->enc.iv_len);
 523                 dh_need = MAX(dh_need, newkeys->mac.key_len);
 524         }
 525         /* XXX need runden? */
 526         kex->we_need = need;
 527         kex->dh_need = dh_need;
 528
 529         /* ignore the next message if the proposals do not match */
 530         if (first_kex_follows && !proposals_match(my, peer) &&
 531             !(datafellows & SSH_BUG_FIRSTKEX)) {
 532                 type = packet_read();
 533                 debug2("skipping next packet (type %u)", type);
 534         }
 535
 536         kex_prop_free(my);
 537         kex_prop_free(peer);
 538 }
 539
 540 static u_char *
 541 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
 542     const u_char *shared_secret, u_int slen)
 543 {
 544         Buffer b;
 545         struct ssh_digest_ctx *hashctx;
 546         char c = id;
 547         u_int have;
 548         size_t mdsz;
 549         u_char *digest;
 550
 551         if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
 552                 fatal("bad kex md size %zu", mdsz);
 553         digest = xmalloc(roundup(need, mdsz));
 554
 555         buffer_init(&b);
 556         buffer_append(&b, shared_secret, slen);
 557
 558         /* K1 = HASH(K || H || "A" || session_id) */
 559         if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
 560                 fatal("%s: ssh_digest_start failed", __func__);
 561         if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
 562             ssh_digest_update(hashctx, hash, hashlen) != 0 ||
 563             ssh_digest_update(hashctx, &c, 1) != 0 ||
 564             ssh_digest_update(hashctx, kex->session_id,
 565             kex->session_id_len) != 0)
 566                 fatal("%s: ssh_digest_update failed", __func__);
 567         if (ssh_digest_final(hashctx, digest, mdsz) != 0)
 568                 fatal("%s: ssh_digest_final failed", __func__);
 569         ssh_digest_free(hashctx);
 570
 571         /*
 572          * expand key:
 573          * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
 574          * Key = K1 || K2 || ... || Kn
 575          */
 576         for (have = mdsz; need > have; have += mdsz) {
 577                 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
 578                         fatal("%s: ssh_digest_start failed", __func__);
 579                 if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
 580                     ssh_digest_update(hashctx, hash, hashlen) != 0 ||
 581                     ssh_digest_update(hashctx, digest, have) != 0)
 582                         fatal("%s: ssh_digest_update failed", __func__);
 583                 if (ssh_digest_final(hashctx, digest + have, mdsz) != 0)
 584                         fatal("%s: ssh_digest_final failed", __func__);
 585                 ssh_digest_free(hashctx);
 586         }
 587         buffer_free(&b);
 588 #ifdef DEBUG_KEX
 589         fprintf(stderr, "key '%c'== ", c);
 590         dump_digest("key", digest, need);
 591 #endif
 592         return digest;
 593 }
 594
 595 Newkeys *current_keys[MODE_MAX];
 596
 597 #define NKEYS   6
 598 void
 599 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen,
 600     const u_char *shared_secret, u_int slen)
 601 {
 602         u_char *keys[NKEYS];
 603         u_int i, mode, ctos;
 604
 605         for (i = 0; i < NKEYS; i++) {
 606                 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
 607                     shared_secret, slen);
 608         }
 609
 610         debug2("kex_derive_keys");
 611         for (mode = 0; mode < MODE_MAX; mode++) {
 612                 current_keys[mode] = kex->newkeys[mode];
 613                 kex->newkeys[mode] = NULL;
 614                 ctos = (!kex->server && mode == MODE_OUT) ||
 615                     (kex->server && mode == MODE_IN);
 616                 current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
 617                 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
 618                 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
 619         }
 620 }
 621
 622 #ifdef WITH_OPENSSL
 623 void
 624 kex_derive_keys_bn(Kex *kex, u_char *hash, u_int hashlen, const BIGNUM *secret)
 625 {
 626         Buffer shared_secret;
 627
 628         buffer_init(&shared_secret);
 629         buffer_put_bignum2(&shared_secret, secret);
 630         kex_derive_keys(kex, hash, hashlen,
 631             buffer_ptr(&shared_secret), buffer_len(&shared_secret));
 632         buffer_free(&shared_secret);
 633 }
 634 #endif
 635
 636 Newkeys *
 637 kex_get_newkeys(int mode)
 638 {
 639         Newkeys *ret;
 640
 641         ret = current_keys[mode];
 642         current_keys[mode] = NULL;
 643         return ret;
 644 }
 645
 646 #ifdef WITH_SSH1
 647 void
 648 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
 649     u_int8_t cookie[8], u_int8_t id[16])
 650 {
 651         u_int8_t nbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
 652         int len;
 653         struct ssh_digest_ctx *hashctx;
 654
 655         if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL)
 656                 fatal("%s: ssh_digest_start", __func__);
 657
 658         len = BN_num_bytes(host_modulus);
 659         if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
 660                 fatal("%s: bad host modulus (len %d)", __func__, len);
 661         BN_bn2bin(host_modulus, nbuf);
 662         if (ssh_digest_update(hashctx, nbuf, len) != 0)
 663                 fatal("%s: ssh_digest_update failed", __func__);
 664
 665         len = BN_num_bytes(server_modulus);
 666         if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
 667                 fatal("%s: bad server modulus (len %d)", __func__, len);
 668         BN_bn2bin(server_modulus, nbuf);
 669         if (ssh_digest_update(hashctx, nbuf, len) != 0 ||
 670             ssh_digest_update(hashctx, cookie, 8) != 0)
 671                 fatal("%s: ssh_digest_update failed", __func__);
 672         if (ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0)
 673                 fatal("%s: ssh_digest_final failed", __func__);
 674         memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
 675
 676         explicit_bzero(nbuf, sizeof(nbuf));
 677         explicit_bzero(obuf, sizeof(obuf));
 678 }
 679 #endif
 680
 681 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
 682 void
 683 dump_digest(char *msg, u_char *digest, int len)
 684 {
 685         int i;
 686
 687         fprintf(stderr, "%s\n", msg);
 688         for (i = 0; i < len; i++) {
 689                 fprintf(stderr, "%02x", digest[i]);
 690                 if (i%32 == 31)
 691                         fprintf(stderr, "\n");
 692                 else if (i%8 == 7)
 693                         fprintf(stderr, " ");
 694         }
 695         fprintf(stderr, "\n");
 696 }
 697 #endif