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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. | |
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" | |
26 | RCSID("$OpenBSD: ssh-dss.c,v 1.11 2001/12/27 18:22:16 markus Exp $"); | |
27 | ||
28 | #include <openssl/bn.h> | |
29 | #include <openssl/evp.h> | |
30 | ||
31 | #include "xmalloc.h" | |
32 | #include "buffer.h" | |
33 | #include "bufaux.h" | |
34 | #include "compat.h" | |
35 | #include "log.h" | |
36 | #include "key.h" | |
37 | #include "ssh-dss.h" | |
38 | ||
39 | #define INTBLOB_LEN 20 | |
40 | #define SIGBLOB_LEN (2*INTBLOB_LEN) | |
41 | ||
42 | int | |
43 | ssh_dss_sign( | |
44 | Key *key, | |
45 | u_char **sigp, int *lenp, | |
46 | u_char *data, int datalen) | |
47 | { | |
48 | DSA_SIG *sig; | |
49 | EVP_MD *evp_md = EVP_sha1(); | |
50 | EVP_MD_CTX md; | |
51 | u_char *digest, *ret, sigblob[SIGBLOB_LEN]; | |
52 | u_int rlen, slen, len, dlen; | |
53 | Buffer b; | |
54 | ||
55 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
56 | error("ssh_dss_sign: no DSA key"); | |
57 | return -1; | |
58 | } | |
59 | dlen = evp_md->md_size; | |
60 | digest = xmalloc(dlen); | |
61 | EVP_DigestInit(&md, evp_md); | |
62 | EVP_DigestUpdate(&md, data, datalen); | |
63 | EVP_DigestFinal(&md, digest, NULL); | |
64 | ||
65 | sig = DSA_do_sign(digest, dlen, key->dsa); | |
66 | ||
67 | memset(digest, 0, dlen); | |
68 | xfree(digest); | |
69 | if (sig == NULL) { | |
70 | error("ssh_dss_sign: sign failed"); | |
71 | return -1; | |
72 | } | |
73 | ||
74 | rlen = BN_num_bytes(sig->r); | |
75 | slen = BN_num_bytes(sig->s); | |
76 | if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { | |
77 | error("bad sig size %d %d", rlen, slen); | |
78 | DSA_SIG_free(sig); | |
79 | return -1; | |
80 | } | |
81 | memset(sigblob, 0, SIGBLOB_LEN); | |
82 | BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); | |
83 | BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); | |
84 | DSA_SIG_free(sig); | |
85 | ||
86 | if (datafellows & SSH_BUG_SIGBLOB) { | |
87 | ret = xmalloc(SIGBLOB_LEN); | |
88 | memcpy(ret, sigblob, SIGBLOB_LEN); | |
89 | if (lenp != NULL) | |
90 | *lenp = SIGBLOB_LEN; | |
91 | if (sigp != NULL) | |
92 | *sigp = ret; | |
93 | } else { | |
94 | /* ietf-drafts */ | |
95 | buffer_init(&b); | |
96 | buffer_put_cstring(&b, "ssh-dss"); | |
97 | buffer_put_string(&b, sigblob, SIGBLOB_LEN); | |
98 | len = buffer_len(&b); | |
99 | ret = xmalloc(len); | |
100 | memcpy(ret, buffer_ptr(&b), len); | |
101 | buffer_free(&b); | |
102 | if (lenp != NULL) | |
103 | *lenp = len; | |
104 | if (sigp != NULL) | |
105 | *sigp = ret; | |
106 | } | |
107 | return 0; | |
108 | } | |
109 | int | |
110 | ssh_dss_verify( | |
111 | Key *key, | |
112 | u_char *signature, int signaturelen, | |
113 | u_char *data, int datalen) | |
114 | { | |
115 | DSA_SIG *sig; | |
116 | EVP_MD *evp_md = EVP_sha1(); | |
117 | EVP_MD_CTX md; | |
118 | u_char *digest, *sigblob; | |
119 | u_int len, dlen; | |
120 | int rlen, ret; | |
121 | Buffer b; | |
122 | ||
123 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
124 | error("ssh_dss_verify: no DSA key"); | |
125 | return -1; | |
126 | } | |
127 | ||
128 | /* fetch signature */ | |
129 | if (datafellows & SSH_BUG_SIGBLOB) { | |
130 | sigblob = signature; | |
131 | len = signaturelen; | |
132 | } else { | |
133 | /* ietf-drafts */ | |
134 | char *ktype; | |
135 | buffer_init(&b); | |
136 | buffer_append(&b, signature, signaturelen); | |
137 | ktype = buffer_get_string(&b, NULL); | |
138 | if (strcmp("ssh-dss", ktype) != 0) { | |
139 | error("ssh_dss_verify: cannot handle type %s", ktype); | |
140 | buffer_free(&b); | |
141 | xfree(ktype); | |
142 | return -1; | |
143 | } | |
144 | xfree(ktype); | |
145 | sigblob = buffer_get_string(&b, &len); | |
146 | rlen = buffer_len(&b); | |
147 | buffer_free(&b); | |
148 | if (rlen != 0) { | |
149 | error("ssh_dss_verify: " | |
150 | "remaining bytes in signature %d", rlen); | |
151 | xfree(sigblob); | |
152 | return -1; | |
153 | } | |
154 | } | |
155 | ||
156 | if (len != SIGBLOB_LEN) { | |
157 | fatal("bad sigbloblen %d != SIGBLOB_LEN", len); | |
158 | } | |
159 | ||
160 | /* parse signature */ | |
161 | if ((sig = DSA_SIG_new()) == NULL) | |
162 | fatal("ssh_dss_verify: DSA_SIG_new failed"); | |
163 | if ((sig->r = BN_new()) == NULL) | |
164 | fatal("ssh_dss_verify: BN_new failed"); | |
165 | if ((sig->s = BN_new()) == NULL) | |
166 | fatal("ssh_dss_verify: BN_new failed"); | |
167 | BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); | |
168 | BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); | |
169 | ||
170 | if (!(datafellows & SSH_BUG_SIGBLOB)) { | |
171 | memset(sigblob, 0, len); | |
172 | xfree(sigblob); | |
173 | } | |
174 | ||
175 | /* sha1 the data */ | |
176 | dlen = evp_md->md_size; | |
177 | digest = xmalloc(dlen); | |
178 | EVP_DigestInit(&md, evp_md); | |
179 | EVP_DigestUpdate(&md, data, datalen); | |
180 | EVP_DigestFinal(&md, digest, NULL); | |
181 | ||
182 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); | |
183 | ||
184 | memset(digest, 0, dlen); | |
185 | xfree(digest); | |
186 | DSA_SIG_free(sig); | |
187 | ||
188 | debug("ssh_dss_verify: signature %s", | |
189 | ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); | |
190 | return ret; | |
191 | } |