1 /* $OpenBSD: ssh-ecdsa.c,v 1.10 2014/02/03 23:28:00 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 #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 #include "digest.h"
46
47 int
ssh_ecdsa_sign(const Key * key,u_char ** sigp,u_int * lenp,const u_char * data,u_int datalen)48 ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp,
49 const u_char *data, u_int datalen)
50 {
51 ECDSA_SIG *sig;
52 int hash_alg;
53 u_char digest[SSH_DIGEST_MAX_LENGTH];
54 u_int len, dlen;
55 Buffer b, bb;
56
57 if (key == NULL || key_type_plain(key->type) != KEY_ECDSA ||
58 key->ecdsa == NULL) {
59 error("%s: no ECDSA key", __func__);
60 return -1;
61 }
62
63 hash_alg = key_ec_nid_to_hash_alg(key->ecdsa_nid);
64 if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
65 error("%s: bad hash algorithm %d", __func__, hash_alg);
66 return -1;
67 }
68 if (ssh_digest_memory(hash_alg, data, datalen,
69 digest, sizeof(digest)) != 0) {
70 error("%s: digest_memory failed", __func__);
71 return -1;
72 }
73
74 sig = ECDSA_do_sign(digest, dlen, key->ecdsa);
75 explicit_bzero(digest, sizeof(digest));
76
77 if (sig == NULL) {
78 error("%s: sign failed", __func__);
79 return -1;
80 }
81
82 buffer_init(&bb);
83 buffer_put_bignum2(&bb, sig->r);
84 buffer_put_bignum2(&bb, sig->s);
85 ECDSA_SIG_free(sig);
86
87 buffer_init(&b);
88 buffer_put_cstring(&b, key_ssh_name_plain(key));
89 buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb));
90 buffer_free(&bb);
91 len = buffer_len(&b);
92 if (lenp != NULL)
93 *lenp = len;
94 if (sigp != NULL) {
95 *sigp = xmalloc(len);
96 memcpy(*sigp, buffer_ptr(&b), len);
97 }
98 buffer_free(&b);
99
100 return 0;
101 }
102 int
ssh_ecdsa_verify(const Key * key,const u_char * signature,u_int signaturelen,const u_char * data,u_int datalen)103 ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
104 const u_char *data, u_int datalen)
105 {
106 ECDSA_SIG *sig;
107 int hash_alg;
108 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob;
109 u_int len, dlen;
110 int rlen, ret;
111 Buffer b, bb;
112 char *ktype;
113
114 if (key == NULL || key_type_plain(key->type) != KEY_ECDSA ||
115 key->ecdsa == NULL) {
116 error("%s: no ECDSA key", __func__);
117 return -1;
118 }
119
120 /* fetch signature */
121 buffer_init(&b);
122 buffer_append(&b, signature, signaturelen);
123 ktype = buffer_get_string(&b, NULL);
124 if (strcmp(key_ssh_name_plain(key), ktype) != 0) {
125 error("%s: cannot handle type %s", __func__, ktype);
126 buffer_free(&b);
127 free(ktype);
128 return -1;
129 }
130 free(ktype);
131 sigblob = buffer_get_string(&b, &len);
132 rlen = buffer_len(&b);
133 buffer_free(&b);
134 if (rlen != 0) {
135 error("%s: remaining bytes in signature %d", __func__, rlen);
136 free(sigblob);
137 return -1;
138 }
139
140 /* parse signature */
141 if ((sig = ECDSA_SIG_new()) == NULL)
142 fatal("%s: ECDSA_SIG_new failed", __func__);
143
144 buffer_init(&bb);
145 buffer_append(&bb, sigblob, len);
146 buffer_get_bignum2(&bb, sig->r);
147 buffer_get_bignum2(&bb, sig->s);
148 if (buffer_len(&bb) != 0)
149 fatal("%s: remaining bytes in inner sigblob", __func__);
150 buffer_free(&bb);
151
152 /* clean up */
153 explicit_bzero(sigblob, len);
154 free(sigblob);
155
156 /* hash the data */
157 hash_alg = key_ec_nid_to_hash_alg(key->ecdsa_nid);
158 if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
159 error("%s: bad hash algorithm %d", __func__, hash_alg);
160 return -1;
161 }
162 if (ssh_digest_memory(hash_alg, data, datalen,
163 digest, sizeof(digest)) != 0) {
164 error("%s: digest_memory failed", __func__);
165 return -1;
166 }
167
168 ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa);
169 explicit_bzero(digest, sizeof(digest));
170
171 ECDSA_SIG_free(sig);
172
173 debug("%s: signature %s", __func__,
174 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
175 return ret;
176 }
177
178 #endif /* OPENSSL_HAS_ECC */
179