kex.c revision 248619 
1/* $OpenBSD: kex.c,v 1.88 2013/01/08 18:49:04 markus Exp $ */
2/* $FreeBSD: head/crypto/openssh/kex.c 248619 2013-03-22 17:55:38Z des $ */
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
29#include <sys/param.h>
30
31#include <signal.h>
32#include <stdarg.h>
33#include <stdio.h>
34#include <stdlib.h>
35#include <string.h>
36
37#include <openssl/crypto.h>
38
39#include "xmalloc.h"
40#include "ssh2.h"
41#include "buffer.h"
42#include "packet.h"
43#include "compat.h"
44#include "cipher.h"
45#include "key.h"
46#include "kex.h"
47#include "log.h"
48#include "mac.h"
49#include "match.h"
50#include "dispatch.h"
51#include "monitor.h"
52#include "roaming.h"
53
54#if OPENSSL_VERSION_NUMBER >= 0x00907000L
55# if defined(HAVE_EVP_SHA256)
56# define evp_ssh_sha256 EVP_sha256
57# else
58extern const EVP_MD *evp_ssh_sha256(void);
59# endif
60#endif
61
62/* prototype */
63static void kex_kexinit_finish(Kex *);
64static void kex_choose_conf(Kex *);
65
66/* Validate KEX method name list */
67int
68kex_names_valid(const char *names)
69{
70	char *s, *cp, *p;
71
72	if (names == NULL || strcmp(names, "") == 0)
73		return 0;
74	s = cp = xstrdup(names);
75	for ((p = strsep(&cp, ",")); p && *p != '\0';
76	    (p = strsep(&cp, ","))) {
77	    	if (strcmp(p, KEX_DHGEX_SHA256) != 0 &&
78		    strcmp(p, KEX_DHGEX_SHA1) != 0 &&
79		    strcmp(p, KEX_DH14) != 0 &&
80		    strcmp(p, KEX_DH1) != 0 &&
81		    (strncmp(p, KEX_ECDH_SHA2_STEM,
82		    sizeof(KEX_ECDH_SHA2_STEM) - 1) != 0 ||
83		    kex_ecdh_name_to_nid(p) == -1)) {
84			error("Unsupported KEX algorithm \"%.100s\"", p);
85			xfree(s);
86			return 0;
87		}
88	}
89	debug3("kex names ok: [%s]", names);
90	xfree(s);
91	return 1;
92}
93
94/* put algorithm proposal into buffer. */
95#ifndef NONE_CIPHER_ENABLED
96static void
97#else
98/* Also used in sshconnect2.c. */
99void
100#endif
101kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
102{
103	u_int i;
104
105	buffer_clear(b);
106	/*
107	 * add a dummy cookie, the cookie will be overwritten by
108	 * kex_send_kexinit(), each time a kexinit is set
109	 */
110	for (i = 0; i < KEX_COOKIE_LEN; i++)
111		buffer_put_char(b, 0);
112	for (i = 0; i < PROPOSAL_MAX; i++)
113		buffer_put_cstring(b, proposal[i]);
114	buffer_put_char(b, 0);			/* first_kex_packet_follows */
115	buffer_put_int(b, 0);			/* uint32 reserved */
116}
117
118/* parse buffer and return algorithm proposal */
119static char **
120kex_buf2prop(Buffer *raw, int *first_kex_follows)
121{
122	Buffer b;
123	u_int i;
124	char **proposal;
125
126	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
127
128	buffer_init(&b);
129	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
130	/* skip cookie */
131	for (i = 0; i < KEX_COOKIE_LEN; i++)
132		buffer_get_char(&b);
133	/* extract kex init proposal strings */
134	for (i = 0; i < PROPOSAL_MAX; i++) {
135		proposal[i] = buffer_get_cstring(&b,NULL);
136		debug2("kex_parse_kexinit: %s", proposal[i]);
137	}
138	/* first kex follows / reserved */
139	i = buffer_get_char(&b);
140	if (first_kex_follows != NULL)
141		*first_kex_follows = i;
142	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
143	i = buffer_get_int(&b);
144	debug2("kex_parse_kexinit: reserved %u ", i);
145	buffer_free(&b);
146	return proposal;
147}
148
149static void
150kex_prop_free(char **proposal)
151{
152	u_int i;
153
154	for (i = 0; i < PROPOSAL_MAX; i++)
155		xfree(proposal[i]);
156	xfree(proposal);
157}
158
159/* ARGSUSED */
160static void
161kex_protocol_error(int type, u_int32_t seq, void *ctxt)
162{
163	error("Hm, kex protocol error: type %d seq %u", type, seq);
164}
165
166static void
167kex_reset_dispatch(void)
168{
169	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
170	    SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
171	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
172}
173
174void
175kex_finish(Kex *kex)
176{
177	kex_reset_dispatch();
178
179	packet_start(SSH2_MSG_NEWKEYS);
180	packet_send();
181	/* packet_write_wait(); */
182	debug("SSH2_MSG_NEWKEYS sent");
183
184	debug("expecting SSH2_MSG_NEWKEYS");
185	packet_read_expect(SSH2_MSG_NEWKEYS);
186	packet_check_eom();
187	debug("SSH2_MSG_NEWKEYS received");
188
189	kex->done = 1;
190	buffer_clear(&kex->peer);
191	/* buffer_clear(&kex->my); */
192	kex->flags &= ~KEX_INIT_SENT;
193	xfree(kex->name);
194	kex->name = NULL;
195}
196
197void
198kex_send_kexinit(Kex *kex)
199{
200	u_int32_t rnd = 0;
201	u_char *cookie;
202	u_int i;
203
204	if (kex == NULL) {
205		error("kex_send_kexinit: no kex, cannot rekey");
206		return;
207	}
208	if (kex->flags & KEX_INIT_SENT) {
209		debug("KEX_INIT_SENT");
210		return;
211	}
212	kex->done = 0;
213
214	/* generate a random cookie */
215	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
216		fatal("kex_send_kexinit: kex proposal too short");
217	cookie = buffer_ptr(&kex->my);
218	for (i = 0; i < KEX_COOKIE_LEN; i++) {
219		if (i % 4 == 0)
220			rnd = arc4random();
221		cookie[i] = rnd;
222		rnd >>= 8;
223	}
224	packet_start(SSH2_MSG_KEXINIT);
225	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
226	packet_send();
227	debug("SSH2_MSG_KEXINIT sent");
228	kex->flags |= KEX_INIT_SENT;
229}
230
231/* ARGSUSED */
232void
233kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
234{
235	char *ptr;
236	u_int i, dlen;
237	Kex *kex = (Kex *)ctxt;
238
239	debug("SSH2_MSG_KEXINIT received");
240	if (kex == NULL)
241		fatal("kex_input_kexinit: no kex, cannot rekey");
242
243	ptr = packet_get_raw(&dlen);
244	buffer_append(&kex->peer, ptr, dlen);
245
246	/* discard packet */
247	for (i = 0; i < KEX_COOKIE_LEN; i++)
248		packet_get_char();
249	for (i = 0; i < PROPOSAL_MAX; i++)
250		xfree(packet_get_string(NULL));
251	/*
252	 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
253	 * KEX method has the server move first, but a server might be using
254	 * a custom method or one that we otherwise don't support. We should
255	 * be prepared to remember first_kex_follows here so we can eat a
256	 * packet later.
257	 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
258	 * for cases where the server *doesn't* go first. I guess we should
259	 * ignore it when it is set for these cases, which is what we do now.
260	 */
261	(void) packet_get_char();	/* first_kex_follows */
262	(void) packet_get_int();	/* reserved */
263	packet_check_eom();
264
265	kex_kexinit_finish(kex);
266}
267
268Kex *
269kex_setup(char *proposal[PROPOSAL_MAX])
270{
271	Kex *kex;
272
273	kex = xcalloc(1, sizeof(*kex));
274	buffer_init(&kex->peer);
275	buffer_init(&kex->my);
276	kex_prop2buf(&kex->my, proposal);
277	kex->done = 0;
278
279	kex_send_kexinit(kex);					/* we start */
280	kex_reset_dispatch();
281
282	return kex;
283}
284
285static void
286kex_kexinit_finish(Kex *kex)
287{
288	if (!(kex->flags & KEX_INIT_SENT))
289		kex_send_kexinit(kex);
290
291	kex_choose_conf(kex);
292
293	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
294	    kex->kex[kex->kex_type] != NULL) {
295		(kex->kex[kex->kex_type])(kex);
296	} else {
297		fatal("Unsupported key exchange %d", kex->kex_type);
298	}
299}
300
301static void
302choose_enc(Enc *enc, char *client, char *server)
303{
304	char *name = match_list(client, server, NULL);
305	if (name == NULL)
306		fatal("no matching cipher found: client %s server %s",
307		    client, server);
308	if ((enc->cipher = cipher_by_name(name)) == NULL)
309		fatal("matching cipher is not supported: %s", name);
310	enc->name = name;
311	enc->enabled = 0;
312	enc->iv = NULL;
313	enc->iv_len = cipher_ivlen(enc->cipher);
314	enc->key = NULL;
315	enc->key_len = cipher_keylen(enc->cipher);
316	enc->block_size = cipher_blocksize(enc->cipher);
317}
318
319static void
320choose_mac(Mac *mac, char *client, char *server)
321{
322	char *name = match_list(client, server, NULL);
323	if (name == NULL)
324		fatal("no matching mac found: client %s server %s",
325		    client, server);
326	if (mac_setup(mac, name) < 0)
327		fatal("unsupported mac %s", name);
328	/* truncate the key */
329	if (datafellows & SSH_BUG_HMAC)
330		mac->key_len = 16;
331	mac->name = name;
332	mac->key = NULL;
333	mac->enabled = 0;
334}
335
336static void
337choose_comp(Comp *comp, char *client, char *server)
338{
339	char *name = match_list(client, server, NULL);
340	if (name == NULL)
341		fatal("no matching comp found: client %s server %s", client, server);
342	if (strcmp(name, "zlib@openssh.com") == 0) {
343		comp->type = COMP_DELAYED;
344	} else if (strcmp(name, "zlib") == 0) {
345		comp->type = COMP_ZLIB;
346	} else if (strcmp(name, "none") == 0) {
347		comp->type = COMP_NONE;
348	} else {
349		fatal("unsupported comp %s", name);
350	}
351	comp->name = name;
352}
353
354static void
355choose_kex(Kex *k, char *client, char *server)
356{
357	k->name = match_list(client, server, NULL);
358	if (k->name == NULL)
359		fatal("Unable to negotiate a key exchange method");
360	if (strcmp(k->name, KEX_DH1) == 0) {
361		k->kex_type = KEX_DH_GRP1_SHA1;
362		k->evp_md = EVP_sha1();
363	} else if (strcmp(k->name, KEX_DH14) == 0) {
364		k->kex_type = KEX_DH_GRP14_SHA1;
365		k->evp_md = EVP_sha1();
366	} else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
367		k->kex_type = KEX_DH_GEX_SHA1;
368		k->evp_md = EVP_sha1();
369#if OPENSSL_VERSION_NUMBER >= 0x00907000L
370	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
371		k->kex_type = KEX_DH_GEX_SHA256;
372		k->evp_md = evp_ssh_sha256();
373	} else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
374	    sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
375 		k->kex_type = KEX_ECDH_SHA2;
376		k->evp_md = kex_ecdh_name_to_evpmd(k->name);
377#endif
378	} else
379		fatal("bad kex alg %s", k->name);
380}
381
382static void
383choose_hostkeyalg(Kex *k, char *client, char *server)
384{
385	char *hostkeyalg = match_list(client, server, NULL);
386	if (hostkeyalg == NULL)
387		fatal("no hostkey alg");
388	k->hostkey_type = key_type_from_name(hostkeyalg);
389	if (k->hostkey_type == KEY_UNSPEC)
390		fatal("bad hostkey alg '%s'", hostkeyalg);
391	xfree(hostkeyalg);
392}
393
394static int
395proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
396{
397	static int check[] = {
398		PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
399	};
400	int *idx;
401	char *p;
402
403	for (idx = &check[0]; *idx != -1; idx++) {
404		if ((p = strchr(my[*idx], ',')) != NULL)
405			*p = '\0';
406		if ((p = strchr(peer[*idx], ',')) != NULL)
407			*p = '\0';
408		if (strcmp(my[*idx], peer[*idx]) != 0) {
409			debug2("proposal mismatch: my %s peer %s",
410			    my[*idx], peer[*idx]);
411			return (0);
412		}
413	}
414	debug2("proposals match");
415	return (1);
416}
417
418static void
419kex_choose_conf(Kex *kex)
420{
421	Newkeys *newkeys;
422	char **my, **peer;
423	char **cprop, **sprop;
424	int nenc, nmac, ncomp;
425	u_int mode, ctos, need, authlen;
426	int first_kex_follows, type;
427#ifdef	NONE_CIPHER_ENABLED
428	int auth_flag;
429#endif
430
431	my   = kex_buf2prop(&kex->my, NULL);
432	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
433
434	if (kex->server) {
435		cprop=peer;
436		sprop=my;
437	} else {
438		cprop=my;
439		sprop=peer;
440	}
441
442	/* Check whether server offers roaming */
443	if (!kex->server) {
444		char *roaming;
445		roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
446		if (roaming) {
447			kex->roaming = 1;
448			xfree(roaming);
449		}
450	}
451
452	/* Algorithm Negotiation */
453#ifdef	NONE_CIPHER_ENABLED
454	auth_flag = packet_get_authentication_state();
455	debug ("AUTH STATE is %d", auth_flag);
456#endif
457	for (mode = 0; mode < MODE_MAX; mode++) {
458		newkeys = xcalloc(1, sizeof(*newkeys));
459		kex->newkeys[mode] = newkeys;
460		ctos = (!kex->server && mode == MODE_OUT) ||
461		    (kex->server && mode == MODE_IN);
462		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
463		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
464		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
465		choose_enc(&newkeys->enc, cprop[nenc], sprop[nenc]);
466		/* ignore mac for authenticated encryption */
467		authlen = cipher_authlen(newkeys->enc.cipher);
468		if (authlen == 0)
469			choose_mac(&newkeys->mac, cprop[nmac], sprop[nmac]);
470		choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
471#ifdef	NONE_CIPHER_ENABLED
472		debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
473		if (strcmp(newkeys->enc.name, "none") == 0) {
474			debug("Requesting NONE. Authflag is %d", auth_flag);
475			if (auth_flag == 1)
476				debug("None requested post authentication.");
477			else
478				fatal("Pre-authentication none cipher requests "
479				    "are not allowed.");
480		}
481#endif
482		debug("kex: %s %s %s %s",
483		    ctos ? "client->server" : "server->client",
484		    newkeys->enc.name,
485		    authlen == 0 ? newkeys->mac.name : "<implicit>",
486		    newkeys->comp.name);
487	}
488	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
489	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
490	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
491	need = 0;
492	for (mode = 0; mode < MODE_MAX; mode++) {
493		newkeys = kex->newkeys[mode];
494		if (need < newkeys->enc.key_len)
495			need = newkeys->enc.key_len;
496		if (need < newkeys->enc.block_size)
497			need = newkeys->enc.block_size;
498		if (need < newkeys->enc.iv_len)
499			need = newkeys->enc.iv_len;
500		if (need < newkeys->mac.key_len)
501			need = newkeys->mac.key_len;
502	}
503	/* XXX need runden? */
504	kex->we_need = need;
505
506	/* ignore the next message if the proposals do not match */
507	if (first_kex_follows && !proposals_match(my, peer) &&
508	    !(datafellows & SSH_BUG_FIRSTKEX)) {
509		type = packet_read();
510		debug2("skipping next packet (type %u)", type);
511	}
512
513	kex_prop_free(my);
514	kex_prop_free(peer);
515}
516
517static u_char *
518derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
519    BIGNUM *shared_secret)
520{
521	Buffer b;
522	EVP_MD_CTX md;
523	char c = id;
524	u_int have;
525	int mdsz;
526	u_char *digest;
527
528	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
529		fatal("bad kex md size %d", mdsz);
530	digest = xmalloc(roundup(need, mdsz));
531
532	buffer_init(&b);
533	buffer_put_bignum2(&b, shared_secret);
534
535	/* K1 = HASH(K || H || "A" || session_id) */
536	EVP_DigestInit(&md, kex->evp_md);
537	if (!(datafellows & SSH_BUG_DERIVEKEY))
538		EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
539	EVP_DigestUpdate(&md, hash, hashlen);
540	EVP_DigestUpdate(&md, &c, 1);
541	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
542	EVP_DigestFinal(&md, digest, NULL);
543
544	/*
545	 * expand key:
546	 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
547	 * Key = K1 || K2 || ... || Kn
548	 */
549	for (have = mdsz; need > have; have += mdsz) {
550		EVP_DigestInit(&md, kex->evp_md);
551		if (!(datafellows & SSH_BUG_DERIVEKEY))
552			EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
553		EVP_DigestUpdate(&md, hash, hashlen);
554		EVP_DigestUpdate(&md, digest, have);
555		EVP_DigestFinal(&md, digest + have, NULL);
556	}
557	buffer_free(&b);
558#ifdef DEBUG_KEX
559	fprintf(stderr, "key '%c'== ", c);
560	dump_digest("key", digest, need);
561#endif
562	return digest;
563}
564
565Newkeys *current_keys[MODE_MAX];
566
567#define NKEYS	6
568void
569kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
570{
571	u_char *keys[NKEYS];
572	u_int i, mode, ctos;
573
574	for (i = 0; i < NKEYS; i++) {
575		keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
576		    shared_secret);
577	}
578
579	debug2("kex_derive_keys");
580	for (mode = 0; mode < MODE_MAX; mode++) {
581		current_keys[mode] = kex->newkeys[mode];
582		kex->newkeys[mode] = NULL;
583		ctos = (!kex->server && mode == MODE_OUT) ||
584		    (kex->server && mode == MODE_IN);
585		current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
586		current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
587		current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
588	}
589}
590
591Newkeys *
592kex_get_newkeys(int mode)
593{
594	Newkeys *ret;
595
596	ret = current_keys[mode];
597	current_keys[mode] = NULL;
598	return ret;
599}
600
601void
602derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
603    u_int8_t cookie[8], u_int8_t id[16])
604{
605	const EVP_MD *evp_md = EVP_md5();
606	EVP_MD_CTX md;
607	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
608	int len;
609
610	EVP_DigestInit(&md, evp_md);
611
612	len = BN_num_bytes(host_modulus);
613	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
614		fatal("%s: bad host modulus (len %d)", __func__, len);
615	BN_bn2bin(host_modulus, nbuf);
616	EVP_DigestUpdate(&md, nbuf, len);
617
618	len = BN_num_bytes(server_modulus);
619	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
620		fatal("%s: bad server modulus (len %d)", __func__, len);
621	BN_bn2bin(server_modulus, nbuf);
622	EVP_DigestUpdate(&md, nbuf, len);
623
624	EVP_DigestUpdate(&md, cookie, 8);
625
626	EVP_DigestFinal(&md, obuf, NULL);
627	memcpy(id, obuf, 16);
628
629	memset(nbuf, 0, sizeof(nbuf));
630	memset(obuf, 0, sizeof(obuf));
631	memset(&md, 0, sizeof(md));
632}
633
634#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
635void
636dump_digest(char *msg, u_char *digest, int len)
637{
638	int i;
639
640	fprintf(stderr, "%s\n", msg);
641	for (i = 0; i < len; i++) {
642		fprintf(stderr, "%02x", digest[i]);
643		if (i%32 == 31)
644			fprintf(stderr, "\n");
645		else if (i%8 == 7)
646			fprintf(stderr, " ");
647	}
648	fprintf(stderr, "\n");
649}
650#endif
651