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Damien Miller4e270b02010-04-16 15:56:21 +10001/* $OpenBSD: ssh-dss.c,v 1.26 2010/04/16 01:47:26 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
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
Damien Miller4e270b02010-04-16 15:56:21 +100056 if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA &&
57 key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) {
Damien Miller0bc1bd82000-11-13 22:57:25 +110058 error("ssh_dss_sign: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +100059 return -1;
60 }
Damien Millera664e872000-04-16 11:52:47 +100061 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +100062 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +110063 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +100064
Ben Lindstrom226cfa02001-01-22 05:34:40 +000065 sig = DSA_do_sign(digest, dlen, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +110066 memset(digest, 'd', sizeof(digest));
Ben Lindstromc66d4362001-06-09 01:36:21 +000067
Ben Lindstromc66d4362001-06-09 01:36:21 +000068 if (sig == NULL) {
69 error("ssh_dss_sign: sign failed");
70 return -1;
71 }
Damien Millera664e872000-04-16 11:52:47 +100072
73 rlen = BN_num_bytes(sig->r);
74 slen = BN_num_bytes(sig->s);
75 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
Ben Lindstrom5c385522002-06-23 21:23:20 +000076 error("bad sig size %u %u", rlen, slen);
Damien Millera664e872000-04-16 11:52:47 +100077 DSA_SIG_free(sig);
78 return -1;
79 }
Damien Millera664e872000-04-16 11:52:47 +100080 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);
83 DSA_SIG_free(sig);
84
Damien Miller30c3d422000-05-09 11:02:59 +100085 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millera664e872000-04-16 11:52:47 +100086 if (lenp != NULL)
87 *lenp = SIGBLOB_LEN;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000088 if (sigp != NULL) {
89 *sigp = xmalloc(SIGBLOB_LEN);
90 memcpy(*sigp, sigblob, SIGBLOB_LEN);
91 }
Damien Millera664e872000-04-16 11:52:47 +100092 } else {
93 /* ietf-drafts */
94 buffer_init(&b);
Damien Miller0bc1bd82000-11-13 22:57:25 +110095 buffer_put_cstring(&b, "ssh-dss");
Damien Millera664e872000-04-16 11:52:47 +100096 buffer_put_string(&b, sigblob, SIGBLOB_LEN);
97 len = buffer_len(&b);
Damien Millera664e872000-04-16 11:52:47 +100098 if (lenp != NULL)
99 *lenp = len;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +0000100 if (sigp != NULL) {
101 *sigp = xmalloc(len);
102 memcpy(*sigp, buffer_ptr(&b), len);
103 }
104 buffer_free(&b);
Damien Millera664e872000-04-16 11:52:47 +1000105 }
106 return 0;
107}
108int
Damien Millerf58b58c2003-11-17 21:18:23 +1100109ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
110 const u_char *data, u_int datalen)
Damien Millera664e872000-04-16 11:52:47 +1000111{
Damien Millera664e872000-04-16 11:52:47 +1000112 DSA_SIG *sig;
Ben Lindstrom80cb27d2002-03-05 01:33:36 +0000113 const EVP_MD *evp_md = EVP_sha1();
Damien Millera664e872000-04-16 11:52:47 +1000114 EVP_MD_CTX md;
Damien Millerc516e922002-02-05 11:53:43 +1100115 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000116 u_int len, dlen;
Ben Lindstromc66d4362001-06-09 01:36:21 +0000117 int rlen, ret;
118 Buffer b;
Damien Millera664e872000-04-16 11:52:47 +1000119
Damien Miller4e270b02010-04-16 15:56:21 +1000120 if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA &&
121 key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) {
Damien Miller0bc1bd82000-11-13 22:57:25 +1100122 error("ssh_dss_verify: no DSA key");
Damien Millera664e872000-04-16 11:52:47 +1000123 return -1;
124 }
125
Damien Millera664e872000-04-16 11:52:47 +1000126 /* fetch signature */
Damien Miller30c3d422000-05-09 11:02:59 +1000127 if (datafellows & SSH_BUG_SIGBLOB) {
Damien Millerf58b58c2003-11-17 21:18:23 +1100128 sigblob = xmalloc(signaturelen);
129 memcpy(sigblob, signature, signaturelen);
Damien Millera664e872000-04-16 11:52:47 +1000130 len = signaturelen;
131 } else {
132 /* ietf-drafts */
Damien Miller6536c7d2000-06-22 21:32:31 +1000133 char *ktype;
Damien Millera664e872000-04-16 11:52:47 +1000134 buffer_init(&b);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000135 buffer_append(&b, signature, signaturelen);
Damien Millera664e872000-04-16 11:52:47 +1000136 ktype = buffer_get_string(&b, NULL);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100137 if (strcmp("ssh-dss", ktype) != 0) {
138 error("ssh_dss_verify: cannot handle type %s", ktype);
Damien Miller6536c7d2000-06-22 21:32:31 +1000139 buffer_free(&b);
Damien Miller36e603d2001-11-12 11:03:35 +1100140 xfree(ktype);
Damien Miller6536c7d2000-06-22 21:32:31 +1000141 return -1;
142 }
Damien Miller36e603d2001-11-12 11:03:35 +1100143 xfree(ktype);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000144 sigblob = buffer_get_string(&b, &len);
Damien Millera664e872000-04-16 11:52:47 +1000145 rlen = buffer_len(&b);
Damien Miller36e603d2001-11-12 11:03:35 +1100146 buffer_free(&b);
Ben Lindstrom1c37c6a2001-12-06 18:00:18 +0000147 if (rlen != 0) {
Damien Miller36e603d2001-11-12 11:03:35 +1100148 error("ssh_dss_verify: "
149 "remaining bytes in signature %d", rlen);
150 xfree(sigblob);
Damien Miller6536c7d2000-06-22 21:32:31 +1000151 return -1;
152 }
Damien Millera664e872000-04-16 11:52:47 +1000153 }
154
155 if (len != SIGBLOB_LEN) {
Ben Lindstrom5c385522002-06-23 21:23:20 +0000156 fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
Damien Millera664e872000-04-16 11:52:47 +1000157 }
158
159 /* parse signature */
Damien Millerda755162002-01-22 23:09:22 +1100160 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");
Darren Tucker0bc85572006-11-07 23:14:41 +1100166 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");
Damien Miller30c3d422000-05-09 11:02:59 +1000169
Damien Millerf58b58c2003-11-17 21:18:23 +1100170 /* clean up */
171 memset(sigblob, 0, len);
172 xfree(sigblob);
Kevin Stevesef4eea92001-02-05 12:42:17 +0000173
Damien Millereba71ba2000-04-29 23:57:08 +1000174 /* sha1 the data */
Damien Millera664e872000-04-16 11:52:47 +1000175 EVP_DigestInit(&md, evp_md);
Damien Millereba71ba2000-04-29 23:57:08 +1000176 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +1100177 EVP_DigestFinal(&md, digest, &dlen);
Damien Millera664e872000-04-16 11:52:47 +1000178
Damien Miller0bc1bd82000-11-13 22:57:25 +1100179 ret = DSA_do_verify(digest, dlen, sig, key->dsa);
Damien Millerc516e922002-02-05 11:53:43 +1100180 memset(digest, 'd', sizeof(digest));
Damien Millera664e872000-04-16 11:52:47 +1000181
Damien Millera664e872000-04-16 11:52:47 +1000182 DSA_SIG_free(sig);
183
Ben Lindstromc66d4362001-06-09 01:36:21 +0000184 debug("ssh_dss_verify: signature %s",
185 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
Damien Millera664e872000-04-16 11:52:47 +1000186 return ret;
187}