1 /* $OpenBSD: ssh-ecdsa.c,v 1.11 2014/06/24 01:13:21 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 */
47 int
ssh_ecdsa_sign(const struct sshkey * key,u_char ** sigp,size_t * lenp,const u_char * data,size_t datalen,u_int compat)48 ssh_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 if (b != NULL)
103 sshbuf_free(b);
104 if (bb != NULL)
105 sshbuf_free(bb);
106 if (sig != NULL)
107 ECDSA_SIG_free(sig);
108 return ret;
109 }
110
111 /* ARGSUSED */
112 int
ssh_ecdsa_verify(const struct sshkey * key,const u_char * signature,size_t signaturelen,const u_char * data,size_t datalen,u_int compat)113 ssh_ecdsa_verify(const struct sshkey *key,
114 const u_char *signature, size_t signaturelen,
115 const u_char *data, size_t datalen, u_int compat)
116 {
117 ECDSA_SIG *sig = NULL;
118 int hash_alg;
119 u_char digest[SSH_DIGEST_MAX_LENGTH];
120 size_t dlen;
121 int ret = SSH_ERR_INTERNAL_ERROR;
122 struct sshbuf *b = NULL, *sigbuf = NULL;
123 char *ktype = NULL;
124
125 if (key == NULL || key->ecdsa == NULL ||
126 sshkey_type_plain(key->type) != KEY_ECDSA)
127 return SSH_ERR_INVALID_ARGUMENT;
128
129 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
130 (dlen = ssh_digest_bytes(hash_alg)) == 0)
131 return SSH_ERR_INTERNAL_ERROR;
132
133 /* fetch signature */
134 if ((b = sshbuf_from(signature, signaturelen)) == NULL)
135 return SSH_ERR_ALLOC_FAIL;
136 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
137 sshbuf_froms(b, &sigbuf) != 0) {
138 ret = SSH_ERR_INVALID_FORMAT;
139 goto out;
140 }
141 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
142 ret = SSH_ERR_KEY_TYPE_MISMATCH;
143 goto out;
144 }
145 if (sshbuf_len(b) != 0) {
146 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
147 goto out;
148 }
149
150 /* parse signature */
151 if ((sig = ECDSA_SIG_new()) == NULL) {
152 ret = SSH_ERR_ALLOC_FAIL;
153 goto out;
154 }
155 if (sshbuf_get_bignum2(sigbuf, sig->r) != 0 ||
156 sshbuf_get_bignum2(sigbuf, sig->s) != 0) {
157 ret = SSH_ERR_INVALID_FORMAT;
158 goto out;
159 }
160 if (sshbuf_len(sigbuf) != 0) {
161 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
162 goto out;
163 }
164 if ((ret = ssh_digest_memory(hash_alg, data, datalen,
165 digest, sizeof(digest))) != 0)
166 goto out;
167
168 switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) {
169 case 1:
170 ret = 0;
171 break;
172 case 0:
173 ret = SSH_ERR_SIGNATURE_INVALID;
174 goto out;
175 default:
176 ret = SSH_ERR_LIBCRYPTO_ERROR;
177 goto out;
178 }
179
180 out:
181 explicit_bzero(digest, sizeof(digest));
182 if (sigbuf != NULL)
183 sshbuf_free(sigbuf);
184 if (b != NULL)
185 sshbuf_free(b);
186 if (sig != NULL)
187 ECDSA_SIG_free(sig);
188 free(ktype);
189 return ret;
190 }
191
192 #endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */
193