1/* $OpenBSD: ssh-ecdsa.c,v 1.5 2012/01/08 13:17:11 miod Exp $ */
2/*
3 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
4 * Copyright (c) 2010 Damien Miller.  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#ifdef OPENSSL_HAS_ECC
30
31#include <sys/types.h>
32
33#include <openssl/bn.h>
34#include <openssl/ec.h>
35#include <openssl/ecdsa.h>
36#include <openssl/evp.h>
37
38#include <string.h>
39
40#include "xmalloc.h"
41#include "buffer.h"
42#include "compat.h"
43#include "log.h"
44#include "key.h"
45
46int
47ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp,
48    const u_char *data, u_int datalen)
49{
50	ECDSA_SIG *sig;
51	const EVP_MD *evp_md;
52	EVP_MD_CTX md;
53	u_char digest[EVP_MAX_MD_SIZE];
54	u_int len, dlen;
55	Buffer b, bb;
56
57	if (key == NULL || key->ecdsa == NULL ||
58	    (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
59		error("%s: no ECDSA key", __func__);
60		return -1;
61	}
62	evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
63	EVP_DigestInit(&md, evp_md);
64	EVP_DigestUpdate(&md, data, datalen);
65	EVP_DigestFinal(&md, digest, &dlen);
66
67	sig = ECDSA_do_sign(digest, dlen, key->ecdsa);
68	memset(digest, 'd', sizeof(digest));
69
70	if (sig == NULL) {
71		error("%s: sign failed", __func__);
72		return -1;
73	}
74
75	buffer_init(&bb);
76	buffer_put_bignum2(&bb, sig->r);
77	buffer_put_bignum2(&bb, sig->s);
78	ECDSA_SIG_free(sig);
79
80	buffer_init(&b);
81	buffer_put_cstring(&b, key_ssh_name_plain(key));
82	buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb));
83	buffer_free(&bb);
84	len = buffer_len(&b);
85	if (lenp != NULL)
86		*lenp = len;
87	if (sigp != NULL) {
88		*sigp = xmalloc(len);
89		memcpy(*sigp, buffer_ptr(&b), len);
90	}
91	buffer_free(&b);
92
93	return 0;
94}
95int
96ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
97    const u_char *data, u_int datalen)
98{
99	ECDSA_SIG *sig;
100	const EVP_MD *evp_md;
101	EVP_MD_CTX md;
102	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
103	u_int len, dlen;
104	int rlen, ret;
105	Buffer b, bb;
106	char *ktype;
107
108	if (key == NULL || key->ecdsa == NULL ||
109	    (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
110		error("%s: no ECDSA key", __func__);
111		return -1;
112	}
113	evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
114
115	/* fetch signature */
116	buffer_init(&b);
117	buffer_append(&b, signature, signaturelen);
118	ktype = buffer_get_string(&b, NULL);
119	if (strcmp(key_ssh_name_plain(key), ktype) != 0) {
120		error("%s: cannot handle type %s", __func__, ktype);
121		buffer_free(&b);
122		xfree(ktype);
123		return -1;
124	}
125	xfree(ktype);
126	sigblob = buffer_get_string(&b, &len);
127	rlen = buffer_len(&b);
128	buffer_free(&b);
129	if (rlen != 0) {
130		error("%s: remaining bytes in signature %d", __func__, rlen);
131		xfree(sigblob);
132		return -1;
133	}
134
135	/* parse signature */
136	if ((sig = ECDSA_SIG_new()) == NULL)
137		fatal("%s: ECDSA_SIG_new failed", __func__);
138	if ((sig->r = BN_new()) == NULL ||
139	    (sig->s = BN_new()) == NULL)
140		fatal("%s: BN_new failed", __func__);
141
142	buffer_init(&bb);
143	buffer_append(&bb, sigblob, len);
144	buffer_get_bignum2(&bb, sig->r);
145	buffer_get_bignum2(&bb, sig->s);
146	if (buffer_len(&bb) != 0)
147		fatal("%s: remaining bytes in inner sigblob", __func__);
148	buffer_free(&bb);
149
150	/* clean up */
151	memset(sigblob, 0, len);
152	xfree(sigblob);
153
154	/* hash the data */
155	EVP_DigestInit(&md, evp_md);
156	EVP_DigestUpdate(&md, data, datalen);
157	EVP_DigestFinal(&md, digest, &dlen);
158
159	ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa);
160	memset(digest, 'd', sizeof(digest));
161
162	ECDSA_SIG_free(sig);
163
164	debug("%s: signature %s", __func__,
165	    ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
166	return ret;
167}
168
169#endif /* OPENSSL_HAS_ECC */
170