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Damien Miller57c30112006-03-26 14:24:48 +11001/* $OpenBSD: ssh-dss.c,v 1.21 2006/03/25 13:17:02 djm Exp $ */
Damien Millera664e872000-04-16 11:52:47 +10002/*
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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.
Damien Millera664e872000-04-16 11:52:47 +100013 *
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.
24 */
25
26#include "includes.h"
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"
37
38#define INTBLOB_LEN 20
39#define SIGBLOB_LEN (2*INTBLOB_LEN)
40
Damien Millera664e872000-04-16 11:52:47 +100041int
Damien Millerf58b58c2003-11-17 21:18:23 +110042ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
43 const u_char *data, u_int datalen)
Damien Millera664e872000-04-16 11:52:47 +100044{
Damien Millera664e872000-04-16 11:52:47 +100045 DSA_SIG *sig;
Ben Lindstrom80cb27d2002-03-05 01:33:36 +000046 const EVP_MD *evp_md = EVP_sha1();
Damien Millera664e872000-04-16 11:52:47 +100047 EVP_MD_CTX md;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000048 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
Ben Lindstromc66d4362001-06-09 01:36:21 +000049 u_int rlen, slen, len, dlen;
Damien Millera664e872000-04-16 11:52:47 +100050 Buffer b;
51
52 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
Damien Miller0bc1bd82000-11-13 22:57:25 +110053 error("ssh_dss_sign: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +100054 return -1;
55 }
Damien Millera664e872000-04-16 11:52:47 +100056 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +100057 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +110058 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +100059
Ben Lindstrom226cfa02001-01-22 05:34:40 +000060 sig = DSA_do_sign(digest, dlen, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +110061 memset(digest, 'd', sizeof(digest));
Ben Lindstromc66d4362001-06-09 01:36:21 +000062
Ben Lindstromc66d4362001-06-09 01:36:21 +000063 if (sig == NULL) {
64 error("ssh_dss_sign: sign failed");
65 return -1;
66 }
Damien Millera664e872000-04-16 11:52:47 +100067
68 rlen = BN_num_bytes(sig->r);
69 slen = BN_num_bytes(sig->s);
70 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
Ben Lindstrom5c385522002-06-23 21:23:20 +000071 error("bad sig size %u %u", rlen, slen);
Damien Millera664e872000-04-16 11:52:47 +100072 DSA_SIG_free(sig);
73 return -1;
74 }
Damien Millera664e872000-04-16 11:52:47 +100075 memset(sigblob, 0, SIGBLOB_LEN);
76 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
77 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
78 DSA_SIG_free(sig);
79
Damien Miller30c3d422000-05-09 11:02:59 +100080 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millera664e872000-04-16 11:52:47 +100081 if (lenp != NULL)
82 *lenp = SIGBLOB_LEN;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000083 if (sigp != NULL) {
84 *sigp = xmalloc(SIGBLOB_LEN);
85 memcpy(*sigp, sigblob, SIGBLOB_LEN);
86 }
Damien Millera664e872000-04-16 11:52:47 +100087 } else {
88 /* ietf-drafts */
89 buffer_init(&b);
Damien Miller0bc1bd82000-11-13 22:57:25 +110090 buffer_put_cstring(&b, "ssh-dss");
Damien Millera664e872000-04-16 11:52:47 +100091 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
92 len = buffer_len(&b);
Damien Millera664e872000-04-16 11:52:47 +100093 if (lenp != NULL)
94 *lenp = len;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000095 if (sigp != NULL) {
96 *sigp = xmalloc(len);
97 memcpy(*sigp, buffer_ptr(&b), len);
98 }
99 buffer_free(&b);
Damien Millera664e872000-04-16 11:52:47 +1000100 }
101 return 0;
102}
103int
Damien Millerf58b58c2003-11-17 21:18:23 +1100104ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
105 const u_char *data, u_int datalen)
Damien Millera664e872000-04-16 11:52:47 +1000106{
Damien Millera664e872000-04-16 11:52:47 +1000107 DSA_SIG *sig;
Ben Lindstrom80cb27d2002-03-05 01:33:36 +0000108 const EVP_MD *evp_md = EVP_sha1();
Damien Millera664e872000-04-16 11:52:47 +1000109 EVP_MD_CTX md;
Damien Millerc516e922002-02-05 11:53:43 +1100110 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000111 u_int len, dlen;
Ben Lindstromc66d4362001-06-09 01:36:21 +0000112 int rlen, ret;
113 Buffer b;
Damien Millera664e872000-04-16 11:52:47 +1000114
115 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
Damien Miller0bc1bd82000-11-13 22:57:25 +1100116 error("ssh_dss_verify: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +1000117 return -1;
118 }
119
Damien Millera664e872000-04-16 11:52:47 +1000120 /* fetch signature */
Damien Miller30c3d422000-05-09 11:02:59 +1000121 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millerf58b58c2003-11-17 21:18:23 +1100122 sigblob = xmalloc(signaturelen);
123 memcpy(sigblob, signature, signaturelen);
Damien Millera664e872000-04-16 11:52:47 +1000124 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
Damien Millerf58b58c2003-11-17 21:18:23 +1100163 /* clean up */
164 memset(sigblob, 0, len);
165 xfree(sigblob);
Kevin Stevesef4eea92001-02-05 12:42:17 +0000166
Damien Millereba71ba2000-04-29 23:57:08 +1000167 /* sha1 the data */
Damien Millera664e872000-04-16 11:52:47 +1000168 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +1000169 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +1100170 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +1000171
Damien Miller0bc1bd82000-11-13 22:57:25 +1100172 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +1100173 memset(digest, 'd', sizeof(digest));
Damien Millera664e872000-04-16 11:52:47 +1000174
Damien Millera664e872000-04-16 11:52:47 +1000175 DSA_SIG_free(sig);
176
Ben Lindstromc66d4362001-06-09 01:36:21 +0000177 debug("ssh_dss_verify: signature %s",
178 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
Damien Millera664e872000-04-16 11:52:47 +1000179 return ret;
180}