kex.c

   1 /* $OpenBSD: kex.c,v 1.86 2010/09/22 05:01:29 djm 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 #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 "roaming.h"
  52
  53 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
  54 # if defined(HAVE_EVP_SHA256)
  55 # define evp_ssh_sha256 EVP_sha256
  56 # else
  57 extern const EVP_MD *evp_ssh_sha256(void);
  58 # endif
  59 #endif
  60
  61 /* prototype */
  62 static void kex_kexinit_finish(Kex *);
  63 static void kex_choose_conf(Kex *);
  64
  65 /* Validate KEX method name list */
  66 int
  67 kex_names_valid(const char *names)
  68 {
  69         char *s, *cp, *p;
  70
  71         if (names == NULL || strcmp(names, "") == 0)
  72                 return 0;
  73         s = cp = xstrdup(names);
  74         for ((p = strsep(&cp, ",")); p && *p != '\0';
  75             (p = strsep(&cp, ","))) {
  76                 if (strcmp(p, KEX_DHGEX_SHA256) != 0 &&
  77                     strcmp(p, KEX_DHGEX_SHA1) != 0 &&
  78                     strcmp(p, KEX_DH14) != 0 &&
  79                     strcmp(p, KEX_DH1) != 0 &&
  80                     (strncmp(p, KEX_ECDH_SHA2_STEM,
  81                     sizeof(KEX_ECDH_SHA2_STEM) - 1) != 0 ||
  82                     kex_ecdh_name_to_nid(p) == -1)) {
  83                         error("Unsupported KEX algorithm \"%.100s\"", p);
  84                         xfree(s);
  85                         return 0;
  86                 }
  87         }
  88         debug3("kex names ok: [%s]", names);
  89         xfree(s);
  90         return 1;
  91 }
  92
  93 /* put algorithm proposal into buffer */
  94 static void
  95 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
  96 {
  97         u_int i;
  98
  99         buffer_clear(b);
 100         /*
 101          * add a dummy cookie, the cookie will be overwritten by
 102          * kex_send_kexinit(), each time a kexinit is set
 103          */
 104         for (i = 0; i < KEX_COOKIE_LEN; i++)
 105                 buffer_put_char(b, 0);
 106         for (i = 0; i < PROPOSAL_MAX; i++)
 107                 buffer_put_cstring(b, proposal[i]);
 108         buffer_put_char(b, 0);                  /* first_kex_packet_follows */
 109         buffer_put_int(b, 0);                   /* uint32 reserved */
 110 }
 111
 112 /* parse buffer and return algorithm proposal */
 113 static char **
 114 kex_buf2prop(Buffer *raw, int *first_kex_follows)
 115 {
 116         Buffer b;
 117         u_int i;
 118         char **proposal;
 119
 120         proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
 121
 122         buffer_init(&b);
 123         buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
 124         /* skip cookie */
 125         for (i = 0; i < KEX_COOKIE_LEN; i++)
 126                 buffer_get_char(&b);
 127         /* extract kex init proposal strings */
 128         for (i = 0; i < PROPOSAL_MAX; i++) {
 129                 proposal[i] = buffer_get_cstring(&b,NULL);
 130                 debug2("kex_parse_kexinit: %s", proposal[i]);
 131         }
 132         /* first kex follows / reserved */
 133         i = buffer_get_char(&b);
 134         if (first_kex_follows != NULL)
 135                 *first_kex_follows = i;
 136         debug2("kex_parse_kexinit: first_kex_follows %d ", i);
 137         i = buffer_get_int(&b);
 138         debug2("kex_parse_kexinit: reserved %u ", i);
 139         buffer_free(&b);
 140         return proposal;
 141 }
 142
 143 static void
 144 kex_prop_free(char **proposal)
 145 {
 146         u_int i;
 147
 148         for (i = 0; i < PROPOSAL_MAX; i++)
 149                 xfree(proposal[i]);
 150         xfree(proposal);
 151 }
 152
 153 /* ARGSUSED */
 154 static void
 155 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
 156 {
 157         error("Hm, kex protocol error: type %d seq %u", type, seq);
 158 }
 159
 160 static void
 161 kex_reset_dispatch(void)
 162 {
 163         dispatch_range(SSH2_MSG_TRANSPORT_MIN,
 164             SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
 165         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 166 }
 167
 168 void
 169 kex_finish(Kex *kex)
 170 {
 171         kex_reset_dispatch();
 172
 173         packet_start(SSH2_MSG_NEWKEYS);
 174         packet_send();
 175         /* packet_write_wait(); */
 176         debug("SSH2_MSG_NEWKEYS sent");
 177
 178         debug("expecting SSH2_MSG_NEWKEYS");
 179         packet_read_expect(SSH2_MSG_NEWKEYS);
 180         packet_check_eom();
 181         debug("SSH2_MSG_NEWKEYS received");
 182
 183         kex->done = 1;
 184         buffer_clear(&kex->peer);
 185         /* buffer_clear(&kex->my); */
 186         kex->flags &= ~KEX_INIT_SENT;
 187         xfree(kex->name);
 188         kex->name = NULL;
 189 }
 190
 191 void
 192 kex_send_kexinit(Kex *kex)
 193 {
 194         u_int32_t rnd = 0;
 195         u_char *cookie;
 196         u_int i;
 197
 198         if (kex == NULL) {
 199                 error("kex_send_kexinit: no kex, cannot rekey");
 200                 return;
 201         }
 202         if (kex->flags & KEX_INIT_SENT) {
 203                 debug("KEX_INIT_SENT");
 204                 return;
 205         }
 206         kex->done = 0;
 207
 208         /* generate a random cookie */
 209         if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
 210                 fatal("kex_send_kexinit: kex proposal too short");
 211         cookie = buffer_ptr(&kex->my);
 212         for (i = 0; i < KEX_COOKIE_LEN; i++) {
 213                 if (i % 4 == 0)
 214                         rnd = arc4random();
 215                 cookie[i] = rnd;
 216                 rnd >>= 8;
 217         }
 218         packet_start(SSH2_MSG_KEXINIT);
 219         packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
 220         packet_send();
 221         debug("SSH2_MSG_KEXINIT sent");
 222         kex->flags |= KEX_INIT_SENT;
 223 }
 224
 225 /* ARGSUSED */
 226 void
 227 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
 228 {
 229         char *ptr;
 230         u_int i, dlen;
 231         Kex *kex = (Kex *)ctxt;
 232
 233         debug("SSH2_MSG_KEXINIT received");
 234         if (kex == NULL)
 235                 fatal("kex_input_kexinit: no kex, cannot rekey");
 236
 237         ptr = packet_get_raw(&dlen);
 238         buffer_append(&kex->peer, ptr, dlen);
 239
 240         /* discard packet */
 241         for (i = 0; i < KEX_COOKIE_LEN; i++)
 242                 packet_get_char();
 243         for (i = 0; i < PROPOSAL_MAX; i++)
 244                 xfree(packet_get_string(NULL));
 245         (void) packet_get_char();
 246         (void) packet_get_int();
 247         packet_check_eom();
 248
 249         kex_kexinit_finish(kex);
 250 }
 251
 252 Kex *
 253 kex_setup(char *proposal[PROPOSAL_MAX])
 254 {
 255         Kex *kex;
 256
 257         kex = xcalloc(1, sizeof(*kex));
 258         buffer_init(&kex->peer);
 259         buffer_init(&kex->my);
 260         kex_prop2buf(&kex->my, proposal);
 261         kex->done = 0;
 262
 263         kex_send_kexinit(kex);                                  /* we start */
 264         kex_reset_dispatch();
 265
 266         return kex;
 267 }
 268
 269 static void
 270 kex_kexinit_finish(Kex *kex)
 271 {
 272         if (!(kex->flags & KEX_INIT_SENT))
 273                 kex_send_kexinit(kex);
 274
 275         kex_choose_conf(kex);
 276
 277         if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
 278             kex->kex[kex->kex_type] != NULL) {
 279                 (kex->kex[kex->kex_type])(kex);
 280         } else {
 281                 fatal("Unsupported key exchange %d", kex->kex_type);
 282         }
 283 }
 284
 285 static void
 286 choose_enc(Enc *enc, char *client, char *server)
 287 {
 288         char *name = match_list(client, server, NULL);
 289         if (name == NULL)
 290                 fatal("no matching cipher found: client %s server %s",
 291                     client, server);
 292         if ((enc->cipher = cipher_by_name(name)) == NULL)
 293                 fatal("matching cipher is not supported: %s", name);
 294         enc->name = name;
 295         enc->enabled = 0;
 296         enc->iv = NULL;
 297         enc->key = NULL;
 298         enc->key_len = cipher_keylen(enc->cipher);
 299         enc->block_size = cipher_blocksize(enc->cipher);
 300 }
 301
 302 static void
 303 choose_mac(Mac *mac, char *client, char *server)
 304 {
 305         char *name = match_list(client, server, NULL);
 306         if (name == NULL)
 307                 fatal("no matching mac found: client %s server %s",
 308                     client, server);
 309         if (mac_setup(mac, name) < 0)
 310                 fatal("unsupported mac %s", name);
 311         /* truncate the key */
 312         if (datafellows & SSH_BUG_HMAC)
 313                 mac->key_len = 16;
 314         mac->name = name;
 315         mac->key = NULL;
 316         mac->enabled = 0;
 317 }
 318
 319 static void
 320 choose_comp(Comp *comp, char *client, char *server)
 321 {
 322         char *name = match_list(client, server, NULL);
 323         if (name == NULL)
 324                 fatal("no matching comp found: client %s server %s", client, server);
 325         if (strcmp(name, "zlib@openssh.com") == 0) {
 326                 comp->type = COMP_DELAYED;
 327         } else if (strcmp(name, "zlib") == 0) {
 328                 comp->type = COMP_ZLIB;
 329         } else if (strcmp(name, "none") == 0) {
 330                 comp->type = COMP_NONE;
 331         } else {
 332                 fatal("unsupported comp %s", name);
 333         }
 334         comp->name = name;
 335 }
 336
 337 static void
 338 choose_kex(Kex *k, char *client, char *server)
 339 {
 340         k->name = match_list(client, server, NULL);
 341         if (k->name == NULL)
 342                 fatal("Unable to negotiate a key exchange method");
 343         if (strcmp(k->name, KEX_DH1) == 0) {
 344                 k->kex_type = KEX_DH_GRP1_SHA1;
 345                 k->evp_md = EVP_sha1();
 346         } else if (strcmp(k->name, KEX_DH14) == 0) {
 347                 k->kex_type = KEX_DH_GRP14_SHA1;
 348                 k->evp_md = EVP_sha1();
 349         } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
 350                 k->kex_type = KEX_DH_GEX_SHA1;
 351                 k->evp_md = EVP_sha1();
 352 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
 353         } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
 354                 k->kex_type = KEX_DH_GEX_SHA256;
 355                 k->evp_md = evp_ssh_sha256();
 356         } else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
 357             sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
 358                 k->kex_type = KEX_ECDH_SHA2;
 359                 k->evp_md = kex_ecdh_name_to_evpmd(k->name);
 360 #endif
 361         } else
 362                 fatal("bad kex alg %s", k->name);
 363 }
 364
 365 static void
 366 choose_hostkeyalg(Kex *k, char *client, char *server)
 367 {
 368         char *hostkeyalg = match_list(client, server, NULL);
 369         if (hostkeyalg == NULL)
 370                 fatal("no hostkey alg");
 371         k->hostkey_type = key_type_from_name(hostkeyalg);
 372         if (k->hostkey_type == KEY_UNSPEC)
 373                 fatal("bad hostkey alg '%s'", hostkeyalg);
 374         xfree(hostkeyalg);
 375 }
 376
 377 static int
 378 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
 379 {
 380         static int check[] = {
 381                 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
 382         };
 383         int *idx;
 384         char *p;
 385
 386         for (idx = &check[0]; *idx != -1; idx++) {
 387                 if ((p = strchr(my[*idx], ',')) != NULL)
 388                         *p = '\0';
 389                 if ((p = strchr(peer[*idx], ',')) != NULL)
 390                         *p = '\0';
 391                 if (strcmp(my[*idx], peer[*idx]) != 0) {
 392                         debug2("proposal mismatch: my %s peer %s",
 393                             my[*idx], peer[*idx]);
 394                         return (0);
 395                 }
 396         }
 397         debug2("proposals match");
 398         return (1);
 399 }
 400
 401 static void
 402 kex_choose_conf(Kex *kex)
 403 {
 404         Newkeys *newkeys;
 405         char **my, **peer;
 406         char **cprop, **sprop;
 407         int nenc, nmac, ncomp;
 408         u_int mode, ctos, need;
 409         int first_kex_follows, type;
 410
 411         my   = kex_buf2prop(&kex->my, NULL);
 412         peer = kex_buf2prop(&kex->peer, &first_kex_follows);
 413
 414         if (kex->server) {
 415                 cprop=peer;
 416                 sprop=my;
 417         } else {
 418                 cprop=my;
 419                 sprop=peer;
 420         }
 421
 422         /* Check whether server offers roaming */
 423         if (!kex->server) {
 424                 char *roaming;
 425                 roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
 426                 if (roaming) {
 427                         kex->roaming = 1;
 428                         xfree(roaming);
 429                 }
 430         }
 431
 432         /* Algorithm Negotiation */
 433         for (mode = 0; mode < MODE_MAX; mode++) {
 434                 newkeys = xcalloc(1, sizeof(*newkeys));
 435                 kex->newkeys[mode] = newkeys;
 436                 ctos = (!kex->server && mode == MODE_OUT) ||
 437                     (kex->server && mode == MODE_IN);
 438                 nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
 439                 nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
 440                 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
 441                 choose_enc (&newkeys->enc,  cprop[nenc],  sprop[nenc]);
 442                 choose_mac (&newkeys->mac,  cprop[nmac],  sprop[nmac]);
 443                 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
 444                 debug("kex: %s %s %s %s",
 445                     ctos ? "client->server" : "server->client",
 446                     newkeys->enc.name,
 447                     newkeys->mac.name,
 448                     newkeys->comp.name);
 449         }
 450         choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
 451         choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
 452             sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
 453         need = 0;
 454         for (mode = 0; mode < MODE_MAX; mode++) {
 455                 newkeys = kex->newkeys[mode];
 456                 if (need < newkeys->enc.key_len)
 457                         need = newkeys->enc.key_len;
 458                 if (need < newkeys->enc.block_size)
 459                         need = newkeys->enc.block_size;
 460                 if (need < newkeys->mac.key_len)
 461                         need = newkeys->mac.key_len;
 462         }
 463         /* XXX need runden? */
 464         kex->we_need = need;
 465
 466         /* ignore the next message if the proposals do not match */
 467         if (first_kex_follows && !proposals_match(my, peer) &&
 468             !(datafellows & SSH_BUG_FIRSTKEX)) {
 469                 type = packet_read();
 470                 debug2("skipping next packet (type %u)", type);
 471         }
 472
 473         kex_prop_free(my);
 474         kex_prop_free(peer);
 475 }
 476
 477 static u_char *
 478 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
 479     BIGNUM *shared_secret)
 480 {
 481         Buffer b;
 482         EVP_MD_CTX md;
 483         char c = id;
 484         u_int have;
 485         int mdsz;
 486         u_char *digest;
 487
 488         if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
 489                 fatal("bad kex md size %d", mdsz);
 490         digest = xmalloc(roundup(need, mdsz));
 491
 492         buffer_init(&b);
 493         buffer_put_bignum2(&b, shared_secret);
 494
 495         /* K1 = HASH(K || H || "A" || session_id) */
 496         EVP_DigestInit(&md, kex->evp_md);
 497         if (!(datafellows & SSH_BUG_DERIVEKEY))
 498                 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
 499         EVP_DigestUpdate(&md, hash, hashlen);
 500         EVP_DigestUpdate(&md, &c, 1);
 501         EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
 502         EVP_DigestFinal(&md, digest, NULL);
 503
 504         /*
 505          * expand key:
 506          * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
 507          * Key = K1 || K2 || ... || Kn
 508          */
 509         for (have = mdsz; need > have; have += mdsz) {
 510                 EVP_DigestInit(&md, kex->evp_md);
 511                 if (!(datafellows & SSH_BUG_DERIVEKEY))
 512                         EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
 513                 EVP_DigestUpdate(&md, hash, hashlen);
 514                 EVP_DigestUpdate(&md, digest, have);
 515                 EVP_DigestFinal(&md, digest + have, NULL);
 516         }
 517         buffer_free(&b);
 518 #ifdef DEBUG_KEX
 519         fprintf(stderr, "key '%c'== ", c);
 520         dump_digest("key", digest, need);
 521 #endif
 522         return digest;
 523 }
 524
 525 Newkeys *current_keys[MODE_MAX];
 526
 527 #define NKEYS   6
 528 void
 529 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
 530 {
 531         u_char *keys[NKEYS];
 532         u_int i, mode, ctos;
 533
 534         for (i = 0; i < NKEYS; i++) {
 535                 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
 536                     shared_secret);
 537         }
 538
 539         debug2("kex_derive_keys");
 540         for (mode = 0; mode < MODE_MAX; mode++) {
 541                 current_keys[mode] = kex->newkeys[mode];
 542                 kex->newkeys[mode] = NULL;
 543                 ctos = (!kex->server && mode == MODE_OUT) ||
 544                     (kex->server && mode == MODE_IN);
 545                 current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
 546                 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
 547                 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
 548         }
 549 }
 550
 551 Newkeys *
 552 kex_get_newkeys(int mode)
 553 {
 554         Newkeys *ret;
 555
 556         ret = current_keys[mode];
 557         current_keys[mode] = NULL;
 558         return ret;
 559 }
 560
 561 void
 562 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
 563     u_int8_t cookie[8], u_int8_t id[16])
 564 {
 565         const EVP_MD *evp_md = EVP_md5();
 566         EVP_MD_CTX md;
 567         u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
 568         int len;
 569
 570         EVP_DigestInit(&md, evp_md);
 571
 572         len = BN_num_bytes(host_modulus);
 573         if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
 574                 fatal("%s: bad host modulus (len %d)", __func__, len);
 575         BN_bn2bin(host_modulus, nbuf);
 576         EVP_DigestUpdate(&md, nbuf, len);
 577
 578         len = BN_num_bytes(server_modulus);
 579         if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
 580                 fatal("%s: bad server modulus (len %d)", __func__, len);
 581         BN_bn2bin(server_modulus, nbuf);
 582         EVP_DigestUpdate(&md, nbuf, len);
 583
 584         EVP_DigestUpdate(&md, cookie, 8);
 585
 586         EVP_DigestFinal(&md, obuf, NULL);
 587         memcpy(id, obuf, 16);
 588
 589         memset(nbuf, 0, sizeof(nbuf));
 590         memset(obuf, 0, sizeof(obuf));
 591         memset(&md, 0, sizeof(md));
 592 }
 593
 594 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
 595 void
 596 dump_digest(char *msg, u_char *digest, int len)
 597 {
 598         int i;
 599
 600         fprintf(stderr, "%s\n", msg);
 601         for (i = 0; i < len; i++) {
 602                 fprintf(stderr, "%02x", digest[i]);
 603                 if (i%32 == 31)
 604                         fprintf(stderr, "\n");
 605                 else if (i%8 == 7)
 606                         fprintf(stderr, " ");
 607         }
 608         fprintf(stderr, "\n");
 609 }
 610 #endif