xref: /openssh-portable/ssh-ecdsa.c (revision 7be8572b)
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