1 /*
2 * Copyright (c) 2000 Markus Friedl. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25 #include "includes.h"
26 RCSID("$OpenBSD: ssh-dss.c,v 1.17 2002/07/04 10:41:47 markus Exp $");
27
28 #pragma ident "%Z%%M% %I% %E% SMI"
29
30 #include <openssl/bn.h>
31 #include <openssl/evp.h>
32
33 #include "xmalloc.h"
34 #include "buffer.h"
35 #include "bufaux.h"
36 #include "compat.h"
37 #include "log.h"
38 #include "key.h"
39 #include "ssh-dss.h"
40
41 #define INTBLOB_LEN 20
42 #define SIGBLOB_LEN (2*INTBLOB_LEN)
43
44 int
ssh_dss_sign(Key * key,u_char ** sigp,u_int * lenp,u_char * data,u_int datalen)45 ssh_dss_sign(Key *key, u_char **sigp, u_int *lenp,
46 u_char *data, u_int datalen)
47 {
48 DSA_SIG *sig;
49 const EVP_MD *evp_md = EVP_sha1();
50 EVP_MD_CTX md;
51 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
52 u_int rlen, slen, len, dlen;
53 Buffer b;
54
55 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
56 error("ssh_dss_sign: no DSA key");
57 return -1;
58 }
59 EVP_DigestInit(&md, evp_md);
60 EVP_DigestUpdate(&md, data, datalen);
61 EVP_DigestFinal(&md, digest, &dlen);
62
63 sig = DSA_do_sign(digest, dlen, key->dsa);
64 memset(digest, 'd', sizeof(digest));
65
66 if (sig == NULL) {
67 error("ssh_dss_sign: sign failed");
68 return -1;
69 }
70
71 rlen = BN_num_bytes(sig->r);
72 slen = BN_num_bytes(sig->s);
73 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
74 error("bad sig size %u %u", rlen, slen);
75 DSA_SIG_free(sig);
76 return -1;
77 }
78 memset(sigblob, 0, SIGBLOB_LEN);
79 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
80 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
81 DSA_SIG_free(sig);
82
83 if (datafellows & SSH_BUG_SIGBLOB) {
84 if (lenp != NULL)
85 *lenp = SIGBLOB_LEN;
86 if (sigp != NULL) {
87 *sigp = xmalloc(SIGBLOB_LEN);
88 memcpy(*sigp, sigblob, SIGBLOB_LEN);
89 }
90 } else {
91 /* ietf-drafts */
92 buffer_init(&b);
93 buffer_put_cstring(&b, "ssh-dss");
94 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
95 len = buffer_len(&b);
96 if (lenp != NULL)
97 *lenp = len;
98 if (sigp != NULL) {
99 *sigp = xmalloc(len);
100 memcpy(*sigp, buffer_ptr(&b), len);
101 }
102 buffer_free(&b);
103 }
104 return 0;
105 }
106 int
ssh_dss_verify(Key * key,u_char * signature,u_int signaturelen,u_char * data,u_int datalen)107 ssh_dss_verify(Key *key, u_char *signature, u_int signaturelen,
108 u_char *data, u_int datalen)
109 {
110 DSA_SIG *sig;
111 const EVP_MD *evp_md = EVP_sha1();
112 EVP_MD_CTX md;
113 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
114 u_int len, dlen;
115 int rlen, ret;
116 Buffer b;
117
118 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
119 error("ssh_dss_verify: no DSA key");
120 return -1;
121 }
122
123 /* fetch signature */
124 if (datafellows & SSH_BUG_SIGBLOB) {
125 sigblob = signature;
126 len = signaturelen;
127 } else {
128 /* ietf-drafts */
129 char *ktype;
130 buffer_init(&b);
131 buffer_append(&b, signature, signaturelen);
132 ktype = buffer_get_string(&b, NULL);
133 if (strcmp("ssh-dss", ktype) != 0) {
134 error("ssh_dss_verify: cannot handle type %s", ktype);
135 buffer_free(&b);
136 xfree(ktype);
137 return -1;
138 }
139 xfree(ktype);
140 sigblob = buffer_get_string(&b, &len);
141 rlen = buffer_len(&b);
142 buffer_free(&b);
143 if (rlen != 0) {
144 error("ssh_dss_verify: "
145 "remaining bytes in signature %d", rlen);
146 xfree(sigblob);
147 return -1;
148 }
149 }
150
151 if (len != SIGBLOB_LEN) {
152 fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
153 }
154
155 /* parse signature */
156 if ((sig = DSA_SIG_new()) == NULL)
157 fatal("ssh_dss_verify: DSA_SIG_new failed");
158 if ((sig->r = BN_new()) == NULL)
159 fatal("ssh_dss_verify: BN_new failed");
160 if ((sig->s = BN_new()) == NULL)
161 fatal("ssh_dss_verify: BN_new failed");
162 BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
163 BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
164
165 if (!(datafellows & SSH_BUG_SIGBLOB)) {
166 memset(sigblob, 0, len);
167 xfree(sigblob);
168 }
169
170 /* sha1 the data */
171 EVP_DigestInit(&md, evp_md);
172 EVP_DigestUpdate(&md, data, datalen);
173 EVP_DigestFinal(&md, digest, &dlen);
174
175 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
176 memset(digest, 'd', sizeof(digest));
177
178 DSA_SIG_free(sig);
179
180 debug("ssh_dss_verify: signature %s",
181 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
182 return ret;
183 }
184