1 /* $OpenBSD: ssh-ecdsa.c,v 1.16 2019/01/21 09:54:11 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 #include "openbsd-compat/openssl-compat.h"
47
48 /* ARGSUSED */
49 int
ssh_ecdsa_sign(const struct sshkey * key,u_char ** sigp,size_t * lenp,const u_char * data,size_t datalen,u_int compat)50 ssh_ecdsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
51 const u_char *data, size_t datalen, u_int compat)
52 {
53 ECDSA_SIG *sig = NULL;
54 const BIGNUM *sig_r, *sig_s;
55 int hash_alg;
56 u_char digest[SSH_DIGEST_MAX_LENGTH];
57 size_t len, dlen;
58 struct sshbuf *b = NULL, *bb = NULL;
59 int ret = SSH_ERR_INTERNAL_ERROR;
60
61 if (lenp != NULL)
62 *lenp = 0;
63 if (sigp != NULL)
64 *sigp = NULL;
65
66 if (key == NULL || key->ecdsa == NULL ||
67 sshkey_type_plain(key->type) != KEY_ECDSA)
68 return SSH_ERR_INVALID_ARGUMENT;
69
70 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
71 (dlen = ssh_digest_bytes(hash_alg)) == 0)
72 return SSH_ERR_INTERNAL_ERROR;
73 if ((ret = ssh_digest_memory(hash_alg, data, datalen,
74 digest, sizeof(digest))) != 0)
75 goto out;
76
77 if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) {
78 ret = SSH_ERR_LIBCRYPTO_ERROR;
79 goto out;
80 }
81
82 if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) {
83 ret = SSH_ERR_ALLOC_FAIL;
84 goto out;
85 }
86 ECDSA_SIG_get0(sig, &sig_r, &sig_s);
87 if ((ret = sshbuf_put_bignum2(bb, sig_r)) != 0 ||
88 (ret = sshbuf_put_bignum2(bb, sig_s)) != 0)
89 goto out;
90 if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 ||
91 (ret = sshbuf_put_stringb(b, bb)) != 0)
92 goto out;
93 len = sshbuf_len(b);
94 if (sigp != NULL) {
95 if ((*sigp = malloc(len)) == NULL) {
96 ret = SSH_ERR_ALLOC_FAIL;
97 goto out;
98 }
99 memcpy(*sigp, sshbuf_ptr(b), len);
100 }
101 if (lenp != NULL)
102 *lenp = len;
103 ret = 0;
104 out:
105 explicit_bzero(digest, sizeof(digest));
106 sshbuf_free(b);
107 sshbuf_free(bb);
108 ECDSA_SIG_free(sig);
109 return ret;
110 }
111
112 /* ARGSUSED */
113 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)114 ssh_ecdsa_verify(const struct sshkey *key,
115 const u_char *signature, size_t signaturelen,
116 const u_char *data, size_t datalen, u_int compat)
117 {
118 ECDSA_SIG *sig = NULL;
119 BIGNUM *sig_r = NULL, *sig_s = NULL;
120 int hash_alg;
121 u_char digest[SSH_DIGEST_MAX_LENGTH];
122 size_t dlen;
123 int ret = SSH_ERR_INTERNAL_ERROR;
124 struct sshbuf *b = NULL, *sigbuf = NULL;
125 char *ktype = NULL;
126
127 if (key == NULL || key->ecdsa == NULL ||
128 sshkey_type_plain(key->type) != KEY_ECDSA ||
129 signature == NULL || signaturelen == 0)
130 return SSH_ERR_INVALID_ARGUMENT;
131
132 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
133 (dlen = ssh_digest_bytes(hash_alg)) == 0)
134 return SSH_ERR_INTERNAL_ERROR;
135
136 /* fetch signature */
137 if ((b = sshbuf_from(signature, signaturelen)) == NULL)
138 return SSH_ERR_ALLOC_FAIL;
139 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
140 sshbuf_froms(b, &sigbuf) != 0) {
141 ret = SSH_ERR_INVALID_FORMAT;
142 goto out;
143 }
144 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
145 ret = SSH_ERR_KEY_TYPE_MISMATCH;
146 goto out;
147 }
148 if (sshbuf_len(b) != 0) {
149 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
150 goto out;
151 }
152
153 /* parse signature */
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 ((sig = ECDSA_SIG_new()) == NULL) {
160 ret = SSH_ERR_ALLOC_FAIL;
161 goto out;
162 }
163 if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) {
164 ret = SSH_ERR_LIBCRYPTO_ERROR;
165 goto out;
166 }
167 sig_r = sig_s = NULL; /* transferred */
168
169 if (sshbuf_len(sigbuf) != 0) {
170 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
171 goto out;
172 }
173 if ((ret = ssh_digest_memory(hash_alg, data, datalen,
174 digest, sizeof(digest))) != 0)
175 goto out;
176
177 switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) {
178 case 1:
179 ret = 0;
180 break;
181 case 0:
182 ret = SSH_ERR_SIGNATURE_INVALID;
183 goto out;
184 default:
185 ret = SSH_ERR_LIBCRYPTO_ERROR;
186 goto out;
187 }
188
189 out:
190 explicit_bzero(digest, sizeof(digest));
191 sshbuf_free(sigbuf);
192 sshbuf_free(b);
193 ECDSA_SIG_free(sig);
194 BN_clear_free(sig_r);
195 BN_clear_free(sig_s);
196 free(ktype);
197 return ret;
198 }
199
200 #endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */
201