1 /* $OpenBSD: ssh-dss.c,v 1.24 2006/11/06 21:25:28 markus Exp $ */
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
28 #include <sys/types.h>
30 #include <openssl/bn.h>
31 #include <openssl/evp.h>
42 #define INTBLOB_LEN 20
43 #define SIGBLOB_LEN (2*INTBLOB_LEN)
46 ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
47 const u_char *data, u_int datalen)
50 const EVP_MD *evp_md = EVP_sha1();
52 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
53 u_int rlen, slen, len, dlen;
56 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
57 error("ssh_dss_sign: no DSA key");
60 EVP_DigestInit(&md, evp_md);
61 EVP_DigestUpdate(&md, data, datalen);
62 EVP_DigestFinal(&md, digest, &dlen);
64 sig = DSA_do_sign(digest, dlen, key->dsa);
65 memset(digest, 'd', sizeof(digest));
68 error("ssh_dss_sign: sign failed");
72 rlen = BN_num_bytes(sig->r);
73 slen = BN_num_bytes(sig->s);
74 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
75 error("bad sig size %u %u", rlen, slen);
79 memset(sigblob, 0, SIGBLOB_LEN);
80 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
81 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
84 if (datafellows & SSH_BUG_SIGBLOB) {
88 *sigp = xmalloc(SIGBLOB_LEN);
89 memcpy(*sigp, sigblob, SIGBLOB_LEN);
94 buffer_put_cstring(&b, "ssh-dss");
95 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
100 *sigp = xmalloc(len);
101 memcpy(*sigp, buffer_ptr(&b), len);
108 ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
109 const u_char *data, u_int datalen)
112 const EVP_MD *evp_md = EVP_sha1();
114 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
119 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
120 error("ssh_dss_verify: no DSA key");
124 /* fetch signature */
125 if (datafellows & SSH_BUG_SIGBLOB) {
126 sigblob = xmalloc(signaturelen);
127 memcpy(sigblob, signature, signaturelen);
133 buffer_append(&b, signature, signaturelen);
134 ktype = buffer_get_string(&b, NULL);
135 if (strcmp("ssh-dss", ktype) != 0) {
136 error("ssh_dss_verify: cannot handle type %s", ktype);
142 sigblob = buffer_get_string(&b, &len);
143 rlen = buffer_len(&b);
146 error("ssh_dss_verify: "
147 "remaining bytes in signature %d", rlen);
153 if (len != SIGBLOB_LEN) {
154 fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
157 /* parse signature */
158 if ((sig = DSA_SIG_new()) == NULL)
159 fatal("ssh_dss_verify: DSA_SIG_new failed");
160 if ((sig->r = BN_new()) == NULL)
161 fatal("ssh_dss_verify: BN_new failed");
162 if ((sig->s = BN_new()) == NULL)
163 fatal("ssh_dss_verify: BN_new failed");
164 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) ||
165 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL))
166 fatal("ssh_dss_verify: BN_bin2bn failed");
169 memset(sigblob, 0, len);
173 EVP_DigestInit(&md, evp_md);
174 EVP_DigestUpdate(&md, data, datalen);
175 EVP_DigestFinal(&md, digest, &dlen);
177 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
178 memset(digest, 'd', sizeof(digest));
182 debug("ssh_dss_verify: signature %s",
183 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");