1 /* $OpenBSD: ssh-dss.c,v 1.27 2010/08/31 09:58:37 djm 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->dsa == NULL || (key->type != KEY_DSA &&
57 key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) {
58 error("ssh_dss_sign: no DSA key");
61 EVP_DigestInit(&md, evp_md);
62 EVP_DigestUpdate(&md, data, datalen);
63 EVP_DigestFinal(&md, digest, &dlen);
65 sig = DSA_do_sign(digest, dlen, key->dsa);
66 memset(digest, 'd', sizeof(digest));
69 error("ssh_dss_sign: sign failed");
73 rlen = BN_num_bytes(sig->r);
74 slen = BN_num_bytes(sig->s);
75 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
76 error("bad sig size %u %u", rlen, slen);
80 memset(sigblob, 0, SIGBLOB_LEN);
81 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
82 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
85 if (datafellows & SSH_BUG_SIGBLOB) {
89 *sigp = xmalloc(SIGBLOB_LEN);
90 memcpy(*sigp, sigblob, SIGBLOB_LEN);
95 buffer_put_cstring(&b, "ssh-dss");
96 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
101 *sigp = xmalloc(len);
102 memcpy(*sigp, buffer_ptr(&b), len);
109 ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
110 const u_char *data, u_int datalen)
113 const EVP_MD *evp_md = EVP_sha1();
115 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
120 if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA &&
121 key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) {
122 error("ssh_dss_verify: no DSA key");
126 /* fetch signature */
127 if (datafellows & SSH_BUG_SIGBLOB) {
128 sigblob = xmalloc(signaturelen);
129 memcpy(sigblob, signature, signaturelen);
135 buffer_append(&b, signature, signaturelen);
136 ktype = buffer_get_cstring(&b, NULL);
137 if (strcmp("ssh-dss", ktype) != 0) {
138 error("ssh_dss_verify: cannot handle type %s", ktype);
144 sigblob = buffer_get_string(&b, &len);
145 rlen = buffer_len(&b);
148 error("ssh_dss_verify: "
149 "remaining bytes in signature %d", rlen);
155 if (len != SIGBLOB_LEN) {
156 fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
159 /* parse signature */
160 if ((sig = DSA_SIG_new()) == NULL)
161 fatal("ssh_dss_verify: DSA_SIG_new failed");
162 if ((sig->r = BN_new()) == NULL)
163 fatal("ssh_dss_verify: BN_new failed");
164 if ((sig->s = BN_new()) == NULL)
165 fatal("ssh_dss_verify: BN_new failed");
166 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) ||
167 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL))
168 fatal("ssh_dss_verify: BN_bin2bn failed");
171 memset(sigblob, 0, len);
175 EVP_DigestInit(&md, evp_md);
176 EVP_DigestUpdate(&md, data, datalen);
177 EVP_DigestFinal(&md, digest, &dlen);
179 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
180 memset(digest, 'd', sizeof(digest));
184 debug("ssh_dss_verify: signature %s",
185 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");