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 */
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 sshbuf_free(b);
103 sshbuf_free(bb);
104 if (sig != NULL)
105 ECDSA_SIG_free(sig);
106 return ret;
107 }
108
109 /* ARGSUSED */
110 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)111 ssh_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