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Damien Millerd7834352006-08-05 12:39:39 +10001/* $OpenBSD: ssh-dss.c,v 1.23 2006/08/03 03:34:42 deraadt 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
Damien Millerd7834352006-08-05 12:39:39 +100028#include <sys/types.h>
29
Ben Lindstrom226cfa02001-01-22 05:34:40 +000030#include <openssl/bn.h>
31#include <openssl/evp.h>
32
Damien Millerded319c2006-09-01 15:38:36 +100033#include <stdarg.h>
Damien Millere3476ed2006-07-24 14:13:33 +100034#include <string.h>
35
Damien Millera664e872000-04-16 11:52:47 +100036#include "xmalloc.h"
37#include "buffer.h"
Damien Millera664e872000-04-16 11:52:47 +100038#include "compat.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000039#include "log.h"
Damien Millera664e872000-04-16 11:52:47 +100040#include "key.h"
41
42#define INTBLOB_LEN 20
43#define SIGBLOB_LEN (2*INTBLOB_LEN)
44
Damien Millera664e872000-04-16 11:52:47 +100045int
Damien Millerf58b58c2003-11-17 21:18:23 +110046ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
47 const u_char *data, u_int datalen)
Damien Millera664e872000-04-16 11:52:47 +100048{
Damien Millera664e872000-04-16 11:52:47 +100049 DSA_SIG *sig;
Ben Lindstrom80cb27d2002-03-05 01:33:36 +000050 const EVP_MD *evp_md = EVP_sha1();
Damien Millera664e872000-04-16 11:52:47 +100051 EVP_MD_CTX md;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000052 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
Ben Lindstromc66d4362001-06-09 01:36:21 +000053 u_int rlen, slen, len, dlen;
Damien Millera664e872000-04-16 11:52:47 +100054 Buffer b;
55
56 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
Damien Miller0bc1bd82000-11-13 22:57:25 +110057 error("ssh_dss_sign: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +100058 return -1;
59 }
Damien Millera664e872000-04-16 11:52:47 +100060 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +100061 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +110062 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +100063
Ben Lindstrom226cfa02001-01-22 05:34:40 +000064 sig = DSA_do_sign(digest, dlen, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +110065 memset(digest, 'd', sizeof(digest));
Ben Lindstromc66d4362001-06-09 01:36:21 +000066
Ben Lindstromc66d4362001-06-09 01:36:21 +000067 if (sig == NULL) {
68 error("ssh_dss_sign: sign failed");
69 return -1;
70 }
Damien Millera664e872000-04-16 11:52:47 +100071
72 rlen = BN_num_bytes(sig->r);
73 slen = BN_num_bytes(sig->s);
74 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
Ben Lindstrom5c385522002-06-23 21:23:20 +000075 error("bad sig size %u %u", rlen, slen);
Damien Millera664e872000-04-16 11:52:47 +100076 DSA_SIG_free(sig);
77 return -1;
78 }
Damien Millera664e872000-04-16 11:52:47 +100079 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);
82 DSA_SIG_free(sig);
83
Damien Miller30c3d422000-05-09 11:02:59 +100084 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millera664e872000-04-16 11:52:47 +100085 if (lenp != NULL)
86 *lenp = SIGBLOB_LEN;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000087 if (sigp != NULL) {
88 *sigp = xmalloc(SIGBLOB_LEN);
89 memcpy(*sigp, sigblob, SIGBLOB_LEN);
90 }
Damien Millera664e872000-04-16 11:52:47 +100091 } else {
92 /* ietf-drafts */
93 buffer_init(&b);
Damien Miller0bc1bd82000-11-13 22:57:25 +110094 buffer_put_cstring(&b, "ssh-dss");
Damien Millera664e872000-04-16 11:52:47 +100095 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
96 len = buffer_len(&b);
Damien Millera664e872000-04-16 11:52:47 +100097 if (lenp != NULL)
98 *lenp = len;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000099 if (sigp != NULL) {
100 *sigp = xmalloc(len);
101 memcpy(*sigp, buffer_ptr(&b), len);
102 }
103 buffer_free(&b);
Damien Millera664e872000-04-16 11:52:47 +1000104 }
105 return 0;
106}
107int
Damien Millerf58b58c2003-11-17 21:18:23 +1100108ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
109 const u_char *data, u_int datalen)
Damien Millera664e872000-04-16 11:52:47 +1000110{
Damien Millera664e872000-04-16 11:52:47 +1000111 DSA_SIG *sig;
Ben Lindstrom80cb27d2002-03-05 01:33:36 +0000112 const EVP_MD *evp_md = EVP_sha1();
Damien Millera664e872000-04-16 11:52:47 +1000113 EVP_MD_CTX md;
Damien Millerc516e922002-02-05 11:53:43 +1100114 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000115 u_int len, dlen;
Ben Lindstromc66d4362001-06-09 01:36:21 +0000116 int rlen, ret;
117 Buffer b;
Damien Millera664e872000-04-16 11:52:47 +1000118
119 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
Damien Miller0bc1bd82000-11-13 22:57:25 +1100120 error("ssh_dss_verify: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +1000121 return -1;
122 }
123
Damien Millera664e872000-04-16 11:52:47 +1000124 /* fetch signature */
Damien Miller30c3d422000-05-09 11:02:59 +1000125 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millerf58b58c2003-11-17 21:18:23 +1100126 sigblob = xmalloc(signaturelen);
127 memcpy(sigblob, signature, signaturelen);
Damien Millera664e872000-04-16 11:52:47 +1000128 len = signaturelen;
129 } else {
130 /* ietf-drafts */
Damien Miller6536c7d2000-06-22 21:32:31 +1000131 char *ktype;
Damien Millera664e872000-04-16 11:52:47 +1000132 buffer_init(&b);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000133 buffer_append(&b, signature, signaturelen);
Damien Millera664e872000-04-16 11:52:47 +1000134 ktype = buffer_get_string(&b, NULL);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100135 if (strcmp("ssh-dss", ktype) != 0) {
136 error("ssh_dss_verify: cannot handle type %s", ktype);
Damien Miller6536c7d2000-06-22 21:32:31 +1000137 buffer_free(&b);
Damien Miller36e603d2001-11-12 11:03:35 +1100138 xfree(ktype);
Damien Miller6536c7d2000-06-22 21:32:31 +1000139 return -1;
140 }
Damien Miller36e603d2001-11-12 11:03:35 +1100141 xfree(ktype);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000142 sigblob = buffer_get_string(&b, &len);
Damien Millera664e872000-04-16 11:52:47 +1000143 rlen = buffer_len(&b);
Damien Miller36e603d2001-11-12 11:03:35 +1100144 buffer_free(&b);
Ben Lindstrom1c37c6a2001-12-06 18:00:18 +0000145 if (rlen != 0) {
Damien Miller36e603d2001-11-12 11:03:35 +1100146 error("ssh_dss_verify: "
147 "remaining bytes in signature %d", rlen);
148 xfree(sigblob);
Damien Miller6536c7d2000-06-22 21:32:31 +1000149 return -1;
150 }
Damien Millera664e872000-04-16 11:52:47 +1000151 }
152
153 if (len != SIGBLOB_LEN) {
Ben Lindstrom5c385522002-06-23 21:23:20 +0000154 fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
Damien Millera664e872000-04-16 11:52:47 +1000155 }
156
157 /* parse signature */
Damien Millerda755162002-01-22 23:09:22 +1100158 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");
Damien Millera664e872000-04-16 11:52:47 +1000164 BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
165 BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
Damien Miller30c3d422000-05-09 11:02:59 +1000166
Damien Millerf58b58c2003-11-17 21:18:23 +1100167 /* clean up */
168 memset(sigblob, 0, len);
169 xfree(sigblob);
Kevin Stevesef4eea92001-02-05 12:42:17 +0000170
Damien Millereba71ba2000-04-29 23:57:08 +1000171 /* sha1 the data */
Damien Millera664e872000-04-16 11:52:47 +1000172 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +1000173 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +1100174 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +1000175
Damien Miller0bc1bd82000-11-13 22:57:25 +1100176 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +1100177 memset(digest, 'd', sizeof(digest));
Damien Millera664e872000-04-16 11:52:47 +1000178
Damien Millera664e872000-04-16 11:52:47 +1000179 DSA_SIG_free(sig);
180
Ben Lindstromc66d4362001-06-09 01:36:21 +0000181 debug("ssh_dss_verify: signature %s",
182 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
Damien Millera664e872000-04-16 11:52:47 +1000183 return ret;
184}