ssh-ed25519.c revision 264377 
1/* $OpenBSD: ssh-ed25519.c,v 1.3 2014/02/23 20:03:42 djm Exp $ */
2/*
3 * Copyright (c) 2013 Markus Friedl <markus@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include "includes.h"
19
20#include <sys/types.h>
21
22#include "crypto_api.h"
23
24#include <limits.h>
25#include <string.h>
26#include <stdarg.h>
27
28#include "xmalloc.h"
29#include "log.h"
30#include "buffer.h"
31#include "key.h"
32#include "ssh.h"
33
34int
35ssh_ed25519_sign(const Key *key, u_char **sigp, u_int *lenp,
36    const u_char *data, u_int datalen)
37{
38	u_char *sig;
39	u_int slen, len;
40	unsigned long long smlen;
41	int ret;
42	Buffer b;
43
44	if (key == NULL || key_type_plain(key->type) != KEY_ED25519 ||
45	    key->ed25519_sk == NULL) {
46		error("%s: no ED25519 key", __func__);
47		return -1;
48	}
49
50	if (datalen >= UINT_MAX - crypto_sign_ed25519_BYTES) {
51		error("%s: datalen %u too long", __func__, datalen);
52		return -1;
53	}
54	smlen = slen = datalen + crypto_sign_ed25519_BYTES;
55	sig = xmalloc(slen);
56
57	if ((ret = crypto_sign_ed25519(sig, &smlen, data, datalen,
58	    key->ed25519_sk)) != 0 || smlen <= datalen) {
59		error("%s: crypto_sign_ed25519 failed: %d", __func__, ret);
60		free(sig);
61		return -1;
62	}
63	/* encode signature */
64	buffer_init(&b);
65	buffer_put_cstring(&b, "ssh-ed25519");
66	buffer_put_string(&b, sig, smlen - datalen);
67	len = buffer_len(&b);
68	if (lenp != NULL)
69		*lenp = len;
70	if (sigp != NULL) {
71		*sigp = xmalloc(len);
72		memcpy(*sigp, buffer_ptr(&b), len);
73	}
74	buffer_free(&b);
75	explicit_bzero(sig, slen);
76	free(sig);
77
78	return 0;
79}
80
81int
82ssh_ed25519_verify(const Key *key, const u_char *signature, u_int signaturelen,
83    const u_char *data, u_int datalen)
84{
85	Buffer b;
86	char *ktype;
87	u_char *sigblob, *sm, *m;
88	u_int len;
89	unsigned long long smlen, mlen;
90	int rlen, ret;
91
92	if (key == NULL || key_type_plain(key->type) != KEY_ED25519 ||
93	    key->ed25519_pk == NULL) {
94		error("%s: no ED25519 key", __func__);
95		return -1;
96	}
97	buffer_init(&b);
98	buffer_append(&b, signature, signaturelen);
99	ktype = buffer_get_cstring(&b, NULL);
100	if (strcmp("ssh-ed25519", ktype) != 0) {
101		error("%s: cannot handle type %s", __func__, ktype);
102		buffer_free(&b);
103		free(ktype);
104		return -1;
105	}
106	free(ktype);
107	sigblob = buffer_get_string(&b, &len);
108	rlen = buffer_len(&b);
109	buffer_free(&b);
110	if (rlen != 0) {
111		error("%s: remaining bytes in signature %d", __func__, rlen);
112		free(sigblob);
113		return -1;
114	}
115	if (len > crypto_sign_ed25519_BYTES) {
116		error("%s: len %u > crypto_sign_ed25519_BYTES %u", __func__,
117		    len, crypto_sign_ed25519_BYTES);
118		free(sigblob);
119		return -1;
120	}
121	smlen = len + datalen;
122	sm = xmalloc(smlen);
123	memcpy(sm, sigblob, len);
124	memcpy(sm+len, data, datalen);
125	mlen = smlen;
126	m = xmalloc(mlen);
127	if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
128	    key->ed25519_pk)) != 0) {
129		debug2("%s: crypto_sign_ed25519_open failed: %d",
130		    __func__, ret);
131	}
132	if (ret == 0 && mlen != datalen) {
133		debug2("%s: crypto_sign_ed25519_open "
134		    "mlen != datalen (%llu != %u)", __func__, mlen, datalen);
135		ret = -1;
136	}
137	/* XXX compare 'm' and 'data' ? */
138
139	explicit_bzero(sigblob, len);
140	explicit_bzero(sm, smlen);
141	explicit_bzero(m, smlen); /* NB. mlen may be invalid if ret != 0 */
142	free(sigblob);
143	free(sm);
144	free(m);
145	debug("%s: signature %scorrect", __func__, (ret != 0) ? "in" : "");
146
147	/* translate return code carefully */
148	return (ret == 0) ? 1 : -1;
149}
150