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1/* $OpenBSD: ssh-ecdsa.c,v 1.4 2010/09/10 01:04:10 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
46int
47ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp,
48 const u_char *data, u_int datalen)
49{
50 ECDSA_SIG *sig;
51 const EVP_MD *evp_md;
52 EVP_MD_CTX md;
53 u_char digest[EVP_MAX_MD_SIZE];
54 u_int len, dlen;
55 Buffer b, bb;
56
57 if (key == NULL || key->ecdsa == NULL ||
58 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
59 error("%s: no ECDSA key", __func__);
60 return -1;
61 }
62 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
63 EVP_DigestInit(&md, evp_md);
64 EVP_DigestUpdate(&md, data, datalen);
65 EVP_DigestFinal(&md, digest, &dlen);
66
67 sig = ECDSA_do_sign(digest, dlen, key->ecdsa);
68 memset(digest, 'd', sizeof(digest));
69
70 if (sig == NULL) {
71 error("%s: sign failed", __func__);
72 return -1;
73 }
74
75 buffer_init(&bb);
76 buffer_put_bignum2(&bb, sig->r);
77 buffer_put_bignum2(&bb, sig->s);
78 ECDSA_SIG_free(sig);
79
80 buffer_init(&b);
81 buffer_put_cstring(&b, key_ssh_name_plain(key));
82 buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb));
83 buffer_free(&bb);
84 len = buffer_len(&b);
85 if (lenp != NULL)
86 *lenp = len;
87 if (sigp != NULL) {
88 *sigp = xmalloc(len);
89 memcpy(*sigp, buffer_ptr(&b), len);
90 }
91 buffer_free(&b);
92
93 return 0;
94}
95int
96ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
97 const u_char *data, u_int datalen)
98{
99 ECDSA_SIG *sig;
100 const EVP_MD *evp_md;
101 EVP_MD_CTX md;
102 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
103 u_int len, dlen;
104 int rlen, ret;
105 Buffer b, bb;
106 char *ktype;
107
108 if (key == NULL || key->ecdsa == NULL ||
109 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
110 error("%s: no ECDSA key", __func__);
111 return -1;
112 }
113 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
114
115 /* fetch signature */
116 buffer_init(&b);
117 buffer_append(&b, signature, signaturelen);
118 ktype = buffer_get_string(&b, NULL);
119 if (strcmp(key_ssh_name_plain(key), ktype) != 0) {
120 error("%s: cannot handle type %s", __func__, ktype);
121 buffer_free(&b);
122 xfree(ktype);
123 return -1;
124 }
125 xfree(ktype);
126 sigblob = buffer_get_string(&b, &len);
127 rlen = buffer_len(&b);
128 buffer_free(&b);
129 if (rlen != 0) {
130 error("%s: remaining bytes in signature %d", __func__, rlen);
131 xfree(sigblob);
132 return -1;
133 }
134
135 /* parse signature */
136 if ((sig = ECDSA_SIG_new()) == NULL)
137 fatal("%s: ECDSA_SIG_new failed", __func__);
138 if ((sig->r = BN_new()) == NULL ||
139 (sig->s = BN_new()) == NULL)
140 fatal("%s: BN_new failed", __func__);
141
142 buffer_init(&bb);
143 buffer_append(&bb, sigblob, len);
144 buffer_get_bignum2(&bb, sig->r);
145 buffer_get_bignum2(&bb, sig->s);
146 if (buffer_len(&bb) != 0)
147 fatal("%s: remaining bytes in inner sigblob", __func__);
148
149 /* clean up */
150 memset(sigblob, 0, len);
151 xfree(sigblob);
152
153 /* hash the data */
154 EVP_DigestInit(&md, evp_md);
155 EVP_DigestUpdate(&md, data, datalen);
156 EVP_DigestFinal(&md, digest, &dlen);
157
158 ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa);
159 memset(digest, 'd', sizeof(digest));
160
161 ECDSA_SIG_free(sig);
162
163 debug("%s: signature %s", __func__,
164 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
165 return ret;
166}
167
168#endif /* OPENSSL_HAS_ECC */