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4f8c6159 | 1 | /* |
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. | |
4f8c6159 | 12 | * |
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" | |
eb9f2fab | 26 | RCSID("$OpenBSD: ssh-dss.c,v 1.17 2002/07/04 10:41:47 markus Exp $"); |
42f11eb2 | 27 | |
28 | #include <openssl/bn.h> | |
29 | #include <openssl/evp.h> | |
4f8c6159 | 30 | |
4f8c6159 | 31 | #include "xmalloc.h" |
32 | #include "buffer.h" | |
33 | #include "bufaux.h" | |
34 | #include "compat.h" | |
42f11eb2 | 35 | #include "log.h" |
4f8c6159 | 36 | #include "key.h" |
5ca51e19 | 37 | #include "ssh-dss.h" |
4f8c6159 | 38 | |
39 | #define INTBLOB_LEN 20 | |
40 | #define SIGBLOB_LEN (2*INTBLOB_LEN) | |
41 | ||
4f8c6159 | 42 | int |
d6133f43 | 43 | ssh_dss_sign(Key *key, u_char **sigp, u_int *lenp, |
c66f9d0e | 44 | u_char *data, u_int datalen) |
4f8c6159 | 45 | { |
4f8c6159 | 46 | DSA_SIG *sig; |
714954dc | 47 | const EVP_MD *evp_md = EVP_sha1(); |
4f8c6159 | 48 | EVP_MD_CTX md; |
eb9f2fab | 49 | u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; |
d87596b0 | 50 | u_int rlen, slen, len, dlen; |
4f8c6159 | 51 | Buffer b; |
52 | ||
53 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 54 | error("ssh_dss_sign: no DSA key"); |
4f8c6159 | 55 | return -1; |
56 | } | |
4f8c6159 | 57 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 58 | EVP_DigestUpdate(&md, data, datalen); |
087dea86 | 59 | EVP_DigestFinal(&md, digest, &dlen); |
4f8c6159 | 60 | |
42f11eb2 | 61 | sig = DSA_do_sign(digest, dlen, key->dsa); |
087dea86 | 62 | memset(digest, 'd', sizeof(digest)); |
d87596b0 | 63 | |
d87596b0 | 64 | if (sig == NULL) { |
65 | error("ssh_dss_sign: sign failed"); | |
66 | return -1; | |
67 | } | |
4f8c6159 | 68 | |
69 | rlen = BN_num_bytes(sig->r); | |
70 | slen = BN_num_bytes(sig->s); | |
71 | if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { | |
d6133f43 | 72 | error("bad sig size %u %u", rlen, slen); |
4f8c6159 | 73 | DSA_SIG_free(sig); |
74 | return -1; | |
75 | } | |
4f8c6159 | 76 | 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 | ||
d0c832f3 | 81 | if (datafellows & SSH_BUG_SIGBLOB) { |
4f8c6159 | 82 | if (lenp != NULL) |
83 | *lenp = SIGBLOB_LEN; | |
eb9f2fab | 84 | if (sigp != NULL) { |
85 | *sigp = xmalloc(SIGBLOB_LEN); | |
86 | memcpy(*sigp, sigblob, SIGBLOB_LEN); | |
87 | } | |
4f8c6159 | 88 | } else { |
89 | /* ietf-drafts */ | |
90 | buffer_init(&b); | |
fa08c86b | 91 | buffer_put_cstring(&b, "ssh-dss"); |
4f8c6159 | 92 | buffer_put_string(&b, sigblob, SIGBLOB_LEN); |
93 | len = buffer_len(&b); | |
4f8c6159 | 94 | if (lenp != NULL) |
95 | *lenp = len; | |
eb9f2fab | 96 | if (sigp != NULL) { |
97 | *sigp = xmalloc(len); | |
98 | memcpy(*sigp, buffer_ptr(&b), len); | |
99 | } | |
100 | buffer_free(&b); | |
4f8c6159 | 101 | } |
102 | return 0; | |
103 | } | |
104 | int | |
d6133f43 | 105 | ssh_dss_verify(Key *key, u_char *signature, u_int signaturelen, |
c66f9d0e | 106 | u_char *data, u_int datalen) |
4f8c6159 | 107 | { |
4f8c6159 | 108 | DSA_SIG *sig; |
714954dc | 109 | const EVP_MD *evp_md = EVP_sha1(); |
4f8c6159 | 110 | EVP_MD_CTX md; |
087dea86 | 111 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; |
1e3b8b07 | 112 | u_int len, dlen; |
d87596b0 | 113 | int rlen, ret; |
114 | Buffer b; | |
4f8c6159 | 115 | |
116 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 117 | error("ssh_dss_verify: no DSA key"); |
4f8c6159 | 118 | return -1; |
119 | } | |
120 | ||
4f8c6159 | 121 | /* fetch signature */ |
d0c832f3 | 122 | if (datafellows & SSH_BUG_SIGBLOB) { |
4f8c6159 | 123 | sigblob = signature; |
124 | len = signaturelen; | |
125 | } else { | |
126 | /* ietf-drafts */ | |
74fc9186 | 127 | char *ktype; |
4f8c6159 | 128 | buffer_init(&b); |
cf54363d | 129 | buffer_append(&b, signature, signaturelen); |
4f8c6159 | 130 | ktype = buffer_get_string(&b, NULL); |
fa08c86b | 131 | if (strcmp("ssh-dss", ktype) != 0) { |
132 | error("ssh_dss_verify: cannot handle type %s", ktype); | |
74fc9186 | 133 | buffer_free(&b); |
abc4e9a7 | 134 | xfree(ktype); |
74fc9186 | 135 | return -1; |
136 | } | |
abc4e9a7 | 137 | xfree(ktype); |
cf54363d | 138 | sigblob = buffer_get_string(&b, &len); |
4f8c6159 | 139 | rlen = buffer_len(&b); |
abc4e9a7 | 140 | buffer_free(&b); |
6aacefa7 | 141 | if (rlen != 0) { |
abc4e9a7 | 142 | error("ssh_dss_verify: " |
143 | "remaining bytes in signature %d", rlen); | |
144 | xfree(sigblob); | |
74fc9186 | 145 | return -1; |
146 | } | |
4f8c6159 | 147 | } |
148 | ||
149 | if (len != SIGBLOB_LEN) { | |
d6133f43 | 150 | fatal("bad sigbloblen %u != SIGBLOB_LEN", len); |
4f8c6159 | 151 | } |
152 | ||
153 | /* parse signature */ | |
b775c6f2 | 154 | 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"); | |
4f8c6159 | 160 | BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); |
161 | BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); | |
d0c832f3 | 162 | |
163 | if (!(datafellows & SSH_BUG_SIGBLOB)) { | |
4f8c6159 | 164 | memset(sigblob, 0, len); |
165 | xfree(sigblob); | |
166 | } | |
2b87da3b | 167 | |
a306f2dd | 168 | /* sha1 the data */ |
4f8c6159 | 169 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 170 | EVP_DigestUpdate(&md, data, datalen); |
087dea86 | 171 | EVP_DigestFinal(&md, digest, &dlen); |
4f8c6159 | 172 | |
fa08c86b | 173 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); |
087dea86 | 174 | memset(digest, 'd', sizeof(digest)); |
4f8c6159 | 175 | |
4f8c6159 | 176 | DSA_SIG_free(sig); |
177 | ||
d87596b0 | 178 | debug("ssh_dss_verify: signature %s", |
179 | ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); | |
4f8c6159 | 180 | return ret; |
181 | } |