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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" | |
b35eb612 | 26 | RCSID("$OpenBSD: ssh-dss.c,v 1.5 2001/02/04 15:32:25 stevesk 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" |
37 | ||
38 | #define INTBLOB_LEN 20 | |
39 | #define SIGBLOB_LEN (2*INTBLOB_LEN) | |
40 | ||
4f8c6159 | 41 | int |
fa08c86b | 42 | ssh_dss_sign( |
4f8c6159 | 43 | Key *key, |
1e3b8b07 | 44 | u_char **sigp, int *lenp, |
45 | u_char *data, int datalen) | |
4f8c6159 | 46 | { |
1e3b8b07 | 47 | u_char *digest; |
48 | u_char *ret; | |
4f8c6159 | 49 | DSA_SIG *sig; |
50 | EVP_MD *evp_md = EVP_sha1(); | |
51 | EVP_MD_CTX md; | |
1e3b8b07 | 52 | u_int rlen; |
53 | u_int slen; | |
42f11eb2 | 54 | u_int len, dlen; |
1e3b8b07 | 55 | u_char sigblob[SIGBLOB_LEN]; |
4f8c6159 | 56 | Buffer b; |
57 | ||
58 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 59 | error("ssh_dss_sign: no DSA key"); |
4f8c6159 | 60 | return -1; |
61 | } | |
42f11eb2 | 62 | dlen = evp_md->md_size; |
63 | digest = xmalloc(dlen); | |
4f8c6159 | 64 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 65 | EVP_DigestUpdate(&md, data, datalen); |
4f8c6159 | 66 | EVP_DigestFinal(&md, digest, NULL); |
67 | ||
42f11eb2 | 68 | sig = DSA_do_sign(digest, dlen, key->dsa); |
a306f2dd | 69 | if (sig == NULL) { |
fa08c86b | 70 | fatal("ssh_dss_sign: cannot sign"); |
a306f2dd | 71 | } |
42f11eb2 | 72 | memset(digest, 0, dlen); |
73 | xfree(digest); | |
4f8c6159 | 74 | |
75 | rlen = BN_num_bytes(sig->r); | |
76 | slen = BN_num_bytes(sig->s); | |
77 | if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { | |
78 | error("bad sig size %d %d", rlen, slen); | |
79 | DSA_SIG_free(sig); | |
80 | return -1; | |
81 | } | |
82 | debug("sig size %d %d", rlen, slen); | |
83 | ||
84 | memset(sigblob, 0, SIGBLOB_LEN); | |
85 | BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); | |
86 | BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); | |
87 | DSA_SIG_free(sig); | |
88 | ||
d0c832f3 | 89 | if (datafellows & SSH_BUG_SIGBLOB) { |
4f8c6159 | 90 | debug("datafellows"); |
91 | ret = xmalloc(SIGBLOB_LEN); | |
92 | memcpy(ret, sigblob, SIGBLOB_LEN); | |
93 | if (lenp != NULL) | |
94 | *lenp = SIGBLOB_LEN; | |
95 | if (sigp != NULL) | |
96 | *sigp = ret; | |
97 | } else { | |
98 | /* ietf-drafts */ | |
99 | buffer_init(&b); | |
fa08c86b | 100 | buffer_put_cstring(&b, "ssh-dss"); |
4f8c6159 | 101 | buffer_put_string(&b, sigblob, SIGBLOB_LEN); |
102 | len = buffer_len(&b); | |
103 | ret = xmalloc(len); | |
104 | memcpy(ret, buffer_ptr(&b), len); | |
105 | buffer_free(&b); | |
106 | if (lenp != NULL) | |
107 | *lenp = len; | |
108 | if (sigp != NULL) | |
109 | *sigp = ret; | |
110 | } | |
111 | return 0; | |
112 | } | |
113 | int | |
fa08c86b | 114 | ssh_dss_verify( |
4f8c6159 | 115 | Key *key, |
1e3b8b07 | 116 | u_char *signature, int signaturelen, |
117 | u_char *data, int datalen) | |
4f8c6159 | 118 | { |
119 | Buffer b; | |
1e3b8b07 | 120 | u_char *digest; |
4f8c6159 | 121 | DSA_SIG *sig; |
122 | EVP_MD *evp_md = EVP_sha1(); | |
123 | EVP_MD_CTX md; | |
1e3b8b07 | 124 | u_char *sigblob; |
4f8c6159 | 125 | char *txt; |
1e3b8b07 | 126 | u_int len, dlen; |
4f8c6159 | 127 | int rlen; |
128 | int ret; | |
129 | ||
130 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 131 | error("ssh_dss_verify: no DSA key"); |
4f8c6159 | 132 | return -1; |
133 | } | |
134 | ||
d0c832f3 | 135 | if (!(datafellows & SSH_BUG_SIGBLOB) && |
136 | signaturelen == SIGBLOB_LEN) { | |
137 | datafellows |= ~SSH_BUG_SIGBLOB; | |
138 | log("autodetect SSH_BUG_SIGBLOB"); | |
139 | } else if ((datafellows & SSH_BUG_SIGBLOB) && | |
140 | signaturelen != SIGBLOB_LEN) { | |
141 | log("autoremove SSH_BUG_SIGBLOB"); | |
142 | datafellows &= ~SSH_BUG_SIGBLOB; | |
4f8c6159 | 143 | } |
144 | ||
145 | debug("len %d datafellows %d", signaturelen, datafellows); | |
146 | ||
147 | /* fetch signature */ | |
d0c832f3 | 148 | if (datafellows & SSH_BUG_SIGBLOB) { |
4f8c6159 | 149 | sigblob = signature; |
150 | len = signaturelen; | |
151 | } else { | |
152 | /* ietf-drafts */ | |
74fc9186 | 153 | char *ktype; |
4f8c6159 | 154 | buffer_init(&b); |
155 | buffer_append(&b, (char *) signature, signaturelen); | |
156 | ktype = buffer_get_string(&b, NULL); | |
fa08c86b | 157 | if (strcmp("ssh-dss", ktype) != 0) { |
158 | error("ssh_dss_verify: cannot handle type %s", ktype); | |
74fc9186 | 159 | buffer_free(&b); |
160 | return -1; | |
161 | } | |
1e3b8b07 | 162 | sigblob = (u_char *)buffer_get_string(&b, &len); |
4f8c6159 | 163 | rlen = buffer_len(&b); |
74fc9186 | 164 | if(rlen != 0) { |
4f8c6159 | 165 | error("remaining bytes in signature %d", rlen); |
74fc9186 | 166 | buffer_free(&b); |
167 | return -1; | |
168 | } | |
4f8c6159 | 169 | buffer_free(&b); |
74fc9186 | 170 | xfree(ktype); |
4f8c6159 | 171 | } |
172 | ||
173 | if (len != SIGBLOB_LEN) { | |
174 | fatal("bad sigbloblen %d != SIGBLOB_LEN", len); | |
175 | } | |
176 | ||
177 | /* parse signature */ | |
178 | sig = DSA_SIG_new(); | |
179 | sig->r = BN_new(); | |
180 | sig->s = BN_new(); | |
181 | BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); | |
182 | BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); | |
d0c832f3 | 183 | |
184 | if (!(datafellows & SSH_BUG_SIGBLOB)) { | |
4f8c6159 | 185 | memset(sigblob, 0, len); |
186 | xfree(sigblob); | |
187 | } | |
2b87da3b | 188 | |
a306f2dd | 189 | /* sha1 the data */ |
fa08c86b | 190 | dlen = evp_md->md_size; |
191 | digest = xmalloc(dlen); | |
4f8c6159 | 192 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 193 | EVP_DigestUpdate(&md, data, datalen); |
4f8c6159 | 194 | EVP_DigestFinal(&md, digest, NULL); |
195 | ||
fa08c86b | 196 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); |
4f8c6159 | 197 | |
fa08c86b | 198 | memset(digest, 0, dlen); |
4f8c6159 | 199 | xfree(digest); |
200 | DSA_SIG_free(sig); | |
201 | ||
202 | switch (ret) { | |
203 | case 1: | |
204 | txt = "correct"; | |
205 | break; | |
206 | case 0: | |
207 | txt = "incorrect"; | |
208 | break; | |
209 | case -1: | |
210 | default: | |
211 | txt = "error"; | |
212 | break; | |
213 | } | |
fa08c86b | 214 | debug("ssh_dss_verify: signature %s", txt); |
4f8c6159 | 215 | return ret; |
216 | } |