1 /* $OpenBSD: ssh-dss.c,v 1.35 2016/04/21 06:08:02 djm Exp $ */
2 /*
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26 #include "includes.h"
27
28 #ifdef WITH_OPENSSL
29
30 #include <sys/types.h>
31
32 #include <openssl/bn.h>
33 #include <openssl/dsa.h>
34 #include <openssl/evp.h>
35
36 #include <stdarg.h>
37 #include <string.h>
38
39 #include "sshbuf.h"
40 #include "compat.h"
41 #include "ssherr.h"
42 #include "digest.h"
43 #define SSHKEY_INTERNAL
44 #include "sshkey.h"
45
46 #define INTBLOB_LEN 20
47 #define SIGBLOB_LEN (2*INTBLOB_LEN)
48
49 int
ssh_dss_sign(const struct sshkey * key,u_char ** sigp,size_t * lenp,const u_char * data,size_t datalen,u_int compat)50 ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
51 const u_char *data, size_t datalen, u_int compat)
52 {
53 DSA_SIG *sig = NULL;
54 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN];
55 size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
56 struct sshbuf *b = NULL;
57 int ret = SSH_ERR_INVALID_ARGUMENT;
58
59 if (lenp != NULL)
60 *lenp = 0;
61 if (sigp != NULL)
62 *sigp = NULL;
63
64 if (key == NULL || key->dsa == NULL ||
65 sshkey_type_plain(key->type) != KEY_DSA)
66 return SSH_ERR_INVALID_ARGUMENT;
67 if (dlen == 0)
68 return SSH_ERR_INTERNAL_ERROR;
69
70 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
71 digest, sizeof(digest))) != 0)
72 goto out;
73
74 if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) {
75 ret = SSH_ERR_LIBCRYPTO_ERROR;
76 goto out;
77 }
78
79 rlen = BN_num_bytes(sig->r);
80 slen = BN_num_bytes(sig->s);
81 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
82 ret = SSH_ERR_INTERNAL_ERROR;
83 goto out;
84 }
85 explicit_bzero(sigblob, SIGBLOB_LEN);
86 BN_bn2bin(sig->r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen);
87 BN_bn2bin(sig->s, sigblob + SIGBLOB_LEN - slen);
88
89 if (compat & SSH_BUG_SIGBLOB) {
90 if (sigp != NULL) {
91 if ((*sigp = malloc(SIGBLOB_LEN)) == NULL) {
92 ret = SSH_ERR_ALLOC_FAIL;
93 goto out;
94 }
95 memcpy(*sigp, sigblob, SIGBLOB_LEN);
96 }
97 if (lenp != NULL)
98 *lenp = SIGBLOB_LEN;
99 ret = 0;
100 } else {
101 /* ietf-drafts */
102 if ((b = sshbuf_new()) == NULL) {
103 ret = SSH_ERR_ALLOC_FAIL;
104 goto out;
105 }
106 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 ||
107 (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0)
108 goto out;
109 len = sshbuf_len(b);
110 if (sigp != NULL) {
111 if ((*sigp = malloc(len)) == NULL) {
112 ret = SSH_ERR_ALLOC_FAIL;
113 goto out;
114 }
115 memcpy(*sigp, sshbuf_ptr(b), len);
116 }
117 if (lenp != NULL)
118 *lenp = len;
119 ret = 0;
120 }
121 out:
122 explicit_bzero(digest, sizeof(digest));
123 if (sig != NULL)
124 DSA_SIG_free(sig);
125 sshbuf_free(b);
126 return ret;
127 }
128
129 int
ssh_dss_verify(const struct sshkey * key,const u_char * signature,size_t signaturelen,const u_char * data,size_t datalen,u_int compat)130 ssh_dss_verify(const struct sshkey *key,
131 const u_char *signature, size_t signaturelen,
132 const u_char *data, size_t datalen, u_int compat)
133 {
134 DSA_SIG *sig = NULL;
135 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL;
136 size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
137 int ret = SSH_ERR_INTERNAL_ERROR;
138 struct sshbuf *b = NULL;
139 char *ktype = NULL;
140
141 if (key == NULL || key->dsa == NULL ||
142 sshkey_type_plain(key->type) != KEY_DSA ||
143 signature == NULL || signaturelen == 0)
144 return SSH_ERR_INVALID_ARGUMENT;
145 if (dlen == 0)
146 return SSH_ERR_INTERNAL_ERROR;
147
148 /* fetch signature */
149 if (compat & SSH_BUG_SIGBLOB) {
150 if ((sigblob = malloc(signaturelen)) == NULL)
151 return SSH_ERR_ALLOC_FAIL;
152 memcpy(sigblob, signature, signaturelen);
153 len = signaturelen;
154 } else {
155 /* ietf-drafts */
156 if ((b = sshbuf_from(signature, signaturelen)) == NULL)
157 return SSH_ERR_ALLOC_FAIL;
158 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
159 sshbuf_get_string(b, &sigblob, &len) != 0) {
160 ret = SSH_ERR_INVALID_FORMAT;
161 goto out;
162 }
163 if (strcmp("ssh-dss", ktype) != 0) {
164 ret = SSH_ERR_KEY_TYPE_MISMATCH;
165 goto out;
166 }
167 if (sshbuf_len(b) != 0) {
168 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
169 goto out;
170 }
171 }
172
173 if (len != SIGBLOB_LEN) {
174 ret = SSH_ERR_INVALID_FORMAT;
175 goto out;
176 }
177
178 /* parse signature */
179 if ((sig = DSA_SIG_new()) == NULL ||
180 (sig->r = BN_new()) == NULL ||
181 (sig->s = BN_new()) == NULL) {
182 ret = SSH_ERR_ALLOC_FAIL;
183 goto out;
184 }
185 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) ||
186 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) {
187 ret = SSH_ERR_LIBCRYPTO_ERROR;
188 goto out;
189 }
190
191 /* sha1 the data */
192 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
193 digest, sizeof(digest))) != 0)
194 goto out;
195
196 switch (DSA_do_verify(digest, dlen, sig, key->dsa)) {
197 case 1:
198 ret = 0;
199 break;
200 case 0:
201 ret = SSH_ERR_SIGNATURE_INVALID;
202 goto out;
203 default:
204 ret = SSH_ERR_LIBCRYPTO_ERROR;
205 goto out;
206 }
207
208 out:
209 explicit_bzero(digest, sizeof(digest));
210 if (sig != NULL)
211 DSA_SIG_free(sig);
212 sshbuf_free(b);
213 free(ktype);
214 if (sigblob != NULL) {
215 explicit_bzero(sigblob, len);
216 free(sigblob);
217 }
218 return ret;
219 }
220 #endif /* WITH_OPENSSL */
221