ssh-ecdsa.c revision 323129 
1/* $OpenBSD: ssh-ecdsa.c,v 1.13 2016/04/21 06:08:02 djm 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#if defined(WITH_OPENSSL) && defined(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 "sshbuf.h"
41#include "ssherr.h"
42#include "digest.h"
43#define SSHKEY_INTERNAL
44#include "sshkey.h"
45
46/* ARGSUSED */
47int
48ssh_ecdsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
49    const u_char *data, size_t datalen, u_int compat)
50{
51	ECDSA_SIG *sig = NULL;
52	int hash_alg;
53	u_char digest[SSH_DIGEST_MAX_LENGTH];
54	size_t len, dlen;
55	struct sshbuf *b = NULL, *bb = NULL;
56	int ret = SSH_ERR_INTERNAL_ERROR;
57
58	if (lenp != NULL)
59		*lenp = 0;
60	if (sigp != NULL)
61		*sigp = NULL;
62
63	if (key == NULL || key->ecdsa == NULL ||
64	    sshkey_type_plain(key->type) != KEY_ECDSA)
65		return SSH_ERR_INVALID_ARGUMENT;
66
67	if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
68	    (dlen = ssh_digest_bytes(hash_alg)) == 0)
69		return SSH_ERR_INTERNAL_ERROR;
70	if ((ret = ssh_digest_memory(hash_alg, data, datalen,
71	    digest, sizeof(digest))) != 0)
72		goto out;
73
74	if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) {
75		ret = SSH_ERR_LIBCRYPTO_ERROR;
76		goto out;
77	}
78
79	if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) {
80		ret = SSH_ERR_ALLOC_FAIL;
81		goto out;
82	}
83	if ((ret = sshbuf_put_bignum2(bb, sig->r)) != 0 ||
84	    (ret = sshbuf_put_bignum2(bb, sig->s)) != 0)
85		goto out;
86	if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 ||
87	    (ret = sshbuf_put_stringb(b, bb)) != 0)
88		goto out;
89	len = sshbuf_len(b);
90	if (sigp != NULL) {
91		if ((*sigp = malloc(len)) == NULL) {
92			ret = SSH_ERR_ALLOC_FAIL;
93			goto out;
94		}
95		memcpy(*sigp, sshbuf_ptr(b), len);
96	}
97	if (lenp != NULL)
98		*lenp = len;
99	ret = 0;
100 out:
101	explicit_bzero(digest, sizeof(digest));
102	sshbuf_free(b);
103	sshbuf_free(bb);
104	if (sig != NULL)
105		ECDSA_SIG_free(sig);
106	return ret;
107}
108
109/* ARGSUSED */
110int
111ssh_ecdsa_verify(const struct sshkey *key,
112    const u_char *signature, size_t signaturelen,
113    const u_char *data, size_t datalen, u_int compat)
114{
115	ECDSA_SIG *sig = NULL;
116	int hash_alg;
117	u_char digest[SSH_DIGEST_MAX_LENGTH];
118	size_t dlen;
119	int ret = SSH_ERR_INTERNAL_ERROR;
120	struct sshbuf *b = NULL, *sigbuf = NULL;
121	char *ktype = NULL;
122
123	if (key == NULL || key->ecdsa == NULL ||
124	    sshkey_type_plain(key->type) != KEY_ECDSA ||
125	    signature == NULL || signaturelen == 0)
126		return SSH_ERR_INVALID_ARGUMENT;
127
128	if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
129	    (dlen = ssh_digest_bytes(hash_alg)) == 0)
130		return SSH_ERR_INTERNAL_ERROR;
131
132	/* fetch signature */
133	if ((b = sshbuf_from(signature, signaturelen)) == NULL)
134		return SSH_ERR_ALLOC_FAIL;
135	if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
136	    sshbuf_froms(b, &sigbuf) != 0) {
137		ret = SSH_ERR_INVALID_FORMAT;
138		goto out;
139	}
140	if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
141		ret = SSH_ERR_KEY_TYPE_MISMATCH;
142		goto out;
143	}
144	if (sshbuf_len(b) != 0) {
145		ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
146		goto out;
147	}
148
149	/* parse signature */
150	if ((sig = ECDSA_SIG_new()) == NULL) {
151		ret = SSH_ERR_ALLOC_FAIL;
152		goto out;
153	}
154	if (sshbuf_get_bignum2(sigbuf, sig->r) != 0 ||
155	    sshbuf_get_bignum2(sigbuf, sig->s) != 0) {
156		ret = SSH_ERR_INVALID_FORMAT;
157		goto out;
158	}
159	if (sshbuf_len(sigbuf) != 0) {
160		ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
161		goto out;
162	}
163	if ((ret = ssh_digest_memory(hash_alg, data, datalen,
164	    digest, sizeof(digest))) != 0)
165		goto out;
166
167	switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) {
168	case 1:
169		ret = 0;
170		break;
171	case 0:
172		ret = SSH_ERR_SIGNATURE_INVALID;
173		goto out;
174	default:
175		ret = SSH_ERR_LIBCRYPTO_ERROR;
176		goto out;
177	}
178
179 out:
180	explicit_bzero(digest, sizeof(digest));
181	sshbuf_free(sigbuf);
182	sshbuf_free(b);
183	if (sig != NULL)
184		ECDSA_SIG_free(sig);
185	free(ktype);
186	return ret;
187}
188
189#endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */
190