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Damien Millera664e872000-04-16 11:52:47 +10001/*
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.
Damien Millera664e872000-04-16 11:52:47 +100012 *
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"
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000026RCSID("$OpenBSD: ssh-dss.c,v 1.17 2002/07/04 10:41:47 markus Exp $");
Damien Millera664e872000-04-16 11:52:47 +100027
Ben Lindstrom226cfa02001-01-22 05:34:40 +000028#include <openssl/bn.h>
29#include <openssl/evp.h>
30
Damien Millera664e872000-04-16 11:52:47 +100031#include "xmalloc.h"
32#include "buffer.h"
33#include "bufaux.h"
34#include "compat.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000035#include "log.h"
Damien Millera664e872000-04-16 11:52:47 +100036#include "key.h"
Ben Lindstrom31ca54a2001-02-09 02:11:24 +000037#include "ssh-dss.h"
Damien Millera664e872000-04-16 11:52:47 +100038
39#define INTBLOB_LEN 20
40#define SIGBLOB_LEN (2*INTBLOB_LEN)
41
Damien Millera664e872000-04-16 11:52:47 +100042int
Ben Lindstrom5c385522002-06-23 21:23:20 +000043ssh_dss_sign(Key *key, u_char **sigp, u_int *lenp,
Ben Lindstrom90fd8142002-02-26 18:09:42 +000044 u_char *data, u_int datalen)
Damien Millera664e872000-04-16 11:52:47 +100045{
Damien Millera664e872000-04-16 11:52:47 +100046 DSA_SIG *sig;
Ben Lindstrom80cb27d2002-03-05 01:33:36 +000047 const EVP_MD *evp_md = EVP_sha1();
Damien Millera664e872000-04-16 11:52:47 +100048 EVP_MD_CTX md;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000049 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
Ben Lindstromc66d4362001-06-09 01:36:21 +000050 u_int rlen, slen, len, dlen;
Damien Millera664e872000-04-16 11:52:47 +100051 Buffer b;
52
53 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
Damien Miller0bc1bd82000-11-13 22:57:25 +110054 error("ssh_dss_sign: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +100055 return -1;
56 }
Damien Millera664e872000-04-16 11:52:47 +100057 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +100058 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +110059 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +100060
Ben Lindstrom226cfa02001-01-22 05:34:40 +000061 sig = DSA_do_sign(digest, dlen, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +110062 memset(digest, 'd', sizeof(digest));
Ben Lindstromc66d4362001-06-09 01:36:21 +000063
Ben Lindstromc66d4362001-06-09 01:36:21 +000064 if (sig == NULL) {
65 error("ssh_dss_sign: sign failed");
66 return -1;
67 }
Damien Millera664e872000-04-16 11:52:47 +100068
69 rlen = BN_num_bytes(sig->r);
70 slen = BN_num_bytes(sig->s);
71 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
Ben Lindstrom5c385522002-06-23 21:23:20 +000072 error("bad sig size %u %u", rlen, slen);
Damien Millera664e872000-04-16 11:52:47 +100073 DSA_SIG_free(sig);
74 return -1;
75 }
Damien Millera664e872000-04-16 11:52:47 +100076 memset(sigblob, 0, SIGBLOB_LEN);
77 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
78 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
79 DSA_SIG_free(sig);
80
Damien Miller30c3d422000-05-09 11:02:59 +100081 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millera664e872000-04-16 11:52:47 +100082 if (lenp != NULL)
83 *lenp = SIGBLOB_LEN;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000084 if (sigp != NULL) {
85 *sigp = xmalloc(SIGBLOB_LEN);
86 memcpy(*sigp, sigblob, SIGBLOB_LEN);
87 }
Damien Millera664e872000-04-16 11:52:47 +100088 } else {
89 /* ietf-drafts */
90 buffer_init(&b);
Damien Miller0bc1bd82000-11-13 22:57:25 +110091 buffer_put_cstring(&b, "ssh-dss");
Damien Millera664e872000-04-16 11:52:47 +100092 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
93 len = buffer_len(&b);
Damien Millera664e872000-04-16 11:52:47 +100094 if (lenp != NULL)
95 *lenp = len;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000096 if (sigp != NULL) {
97 *sigp = xmalloc(len);
98 memcpy(*sigp, buffer_ptr(&b), len);
99 }
100 buffer_free(&b);
Damien Millera664e872000-04-16 11:52:47 +1000101 }
102 return 0;
103}
104int
Ben Lindstrom5c385522002-06-23 21:23:20 +0000105ssh_dss_verify(Key *key, u_char *signature, u_int signaturelen,
Ben Lindstrom90fd8142002-02-26 18:09:42 +0000106 u_char *data, u_int datalen)
Damien Millera664e872000-04-16 11:52:47 +1000107{
Damien Millera664e872000-04-16 11:52:47 +1000108 DSA_SIG *sig;
Ben Lindstrom80cb27d2002-03-05 01:33:36 +0000109 const EVP_MD *evp_md = EVP_sha1();
Damien Millera664e872000-04-16 11:52:47 +1000110 EVP_MD_CTX md;
Damien Millerc516e922002-02-05 11:53:43 +1100111 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000112 u_int len, dlen;
Ben Lindstromc66d4362001-06-09 01:36:21 +0000113 int rlen, ret;
114 Buffer b;
Damien Millera664e872000-04-16 11:52:47 +1000115
116 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
Damien Miller0bc1bd82000-11-13 22:57:25 +1100117 error("ssh_dss_verify: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +1000118 return -1;
119 }
120
Damien Millera664e872000-04-16 11:52:47 +1000121 /* fetch signature */
Damien Miller30c3d422000-05-09 11:02:59 +1000122 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millera664e872000-04-16 11:52:47 +1000123 sigblob = signature;
124 len = signaturelen;
125 } else {
126 /* ietf-drafts */
Damien Miller6536c7d2000-06-22 21:32:31 +1000127 char *ktype;
Damien Millera664e872000-04-16 11:52:47 +1000128 buffer_init(&b);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000129 buffer_append(&b, signature, signaturelen);
Damien Millera664e872000-04-16 11:52:47 +1000130 ktype = buffer_get_string(&b, NULL);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100131 if (strcmp("ssh-dss", ktype) != 0) {
132 error("ssh_dss_verify: cannot handle type %s", ktype);
Damien Miller6536c7d2000-06-22 21:32:31 +1000133 buffer_free(&b);
Damien Miller36e603d2001-11-12 11:03:35 +1100134 xfree(ktype);
Damien Miller6536c7d2000-06-22 21:32:31 +1000135 return -1;
136 }
Damien Miller36e603d2001-11-12 11:03:35 +1100137 xfree(ktype);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000138 sigblob = buffer_get_string(&b, &len);
Damien Millera664e872000-04-16 11:52:47 +1000139 rlen = buffer_len(&b);
Damien Miller36e603d2001-11-12 11:03:35 +1100140 buffer_free(&b);
Ben Lindstrom1c37c6a2001-12-06 18:00:18 +0000141 if (rlen != 0) {
Damien Miller36e603d2001-11-12 11:03:35 +1100142 error("ssh_dss_verify: "
143 "remaining bytes in signature %d", rlen);
144 xfree(sigblob);
Damien Miller6536c7d2000-06-22 21:32:31 +1000145 return -1;
146 }
Damien Millera664e872000-04-16 11:52:47 +1000147 }
148
149 if (len != SIGBLOB_LEN) {
Ben Lindstrom5c385522002-06-23 21:23:20 +0000150 fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
Damien Millera664e872000-04-16 11:52:47 +1000151 }
152
153 /* parse signature */
Damien Millerda755162002-01-22 23:09:22 +1100154 if ((sig = DSA_SIG_new()) == NULL)
155 fatal("ssh_dss_verify: DSA_SIG_new failed");
156 if ((sig->r = BN_new()) == NULL)
157 fatal("ssh_dss_verify: BN_new failed");
158 if ((sig->s = BN_new()) == NULL)
159 fatal("ssh_dss_verify: BN_new failed");
Damien Millera664e872000-04-16 11:52:47 +1000160 BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
161 BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
Damien Miller30c3d422000-05-09 11:02:59 +1000162
163 if (!(datafellows & SSH_BUG_SIGBLOB)) {
Damien Millera664e872000-04-16 11:52:47 +1000164 memset(sigblob, 0, len);
165 xfree(sigblob);
166 }
Kevin Stevesef4eea92001-02-05 12:42:17 +0000167
Damien Millereba71ba2000-04-29 23:57:08 +1000168 /* sha1 the data */
Damien Millera664e872000-04-16 11:52:47 +1000169 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +1000170 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +1100171 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +1000172
Damien Miller0bc1bd82000-11-13 22:57:25 +1100173 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +1100174 memset(digest, 'd', sizeof(digest));
Damien Millera664e872000-04-16 11:52:47 +1000175
Damien Millera664e872000-04-16 11:52:47 +1000176 DSA_SIG_free(sig);
177
Ben Lindstromc66d4362001-06-09 01:36:21 +0000178 debug("ssh_dss_verify: signature %s",
179 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
Damien Millera664e872000-04-16 11:52:47 +1000180 return ret;
181}