1 /* $OpenBSD: ssh-dss.c,v 1.31 2014/02/02 03:44:31 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>
43 #define INTBLOB_LEN 20
44 #define SIGBLOB_LEN (2*INTBLOB_LEN)
47 ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
48 const u_char *data, u_int datalen)
51 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN];
52 u_int rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
55 if (key == NULL || key_type_plain(key->type) != KEY_DSA ||
57 error("%s: no DSA key", __func__);
61 if (ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
62 digest, sizeof(digest)) != 0) {
63 error("%s: ssh_digest_memory failed", __func__);
67 sig = DSA_do_sign(digest, dlen, key->dsa);
68 explicit_bzero(digest, sizeof(digest));
71 error("ssh_dss_sign: sign failed");
75 rlen = BN_num_bytes(sig->r);
76 slen = BN_num_bytes(sig->s);
77 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
78 error("bad sig size %u %u", rlen, slen);
82 explicit_bzero(sigblob, SIGBLOB_LEN);
83 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
84 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
87 if (datafellows & SSH_BUG_SIGBLOB) {
91 *sigp = xmalloc(SIGBLOB_LEN);
92 memcpy(*sigp, sigblob, SIGBLOB_LEN);
97 buffer_put_cstring(&b, "ssh-dss");
98 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
103 *sigp = xmalloc(len);
104 memcpy(*sigp, buffer_ptr(&b), len);
111 ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
112 const u_char *data, u_int datalen)
115 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob;
116 u_int len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
120 if (key == NULL || key_type_plain(key->type) != KEY_DSA ||
122 error("%s: no DSA key", __func__);
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("%s: cannot handle type %s", __func__, ktype);
144 sigblob = buffer_get_string(&b, &len);
145 rlen = buffer_len(&b);
148 error("%s: remaining bytes in signature %d",
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("%s: DSA_SIG_new failed", __func__);
162 if ((sig->r = BN_new()) == NULL)
163 fatal("%s: BN_new failed", __func__);
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("%s: BN_bin2bn failed", __func__);
171 explicit_bzero(sigblob, len);
175 if (ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
176 digest, sizeof(digest)) != 0) {
177 error("%s: digest_memory failed", __func__);
181 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
182 explicit_bzero(digest, sizeof(digest));
186 debug("%s: signature %s", __func__,
187 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");