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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 1.19 2003/11/10 16:23:41 jakob 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 | ||
38 | #define INTBLOB_LEN 20 | |
39 | #define SIGBLOB_LEN (2*INTBLOB_LEN) | |
40 | ||
41 | int | |
42 | ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, | |
43 | const u_char *data, u_int datalen) | |
44 | { | |
45 | DSA_SIG *sig; | |
46 | const EVP_MD *evp_md = EVP_sha1(); | |
47 | EVP_MD_CTX md; | |
48 | u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; | |
49 | u_int rlen, slen, len, dlen; | |
50 | Buffer b; | |
51 | ||
52 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
53 | error("ssh_dss_sign: no DSA key"); | |
54 | return -1; | |
55 | } | |
56 | EVP_DigestInit(&md, evp_md); | |
57 | EVP_DigestUpdate(&md, data, datalen); | |
58 | EVP_DigestFinal(&md, digest, &dlen); | |
59 | ||
60 | sig = DSA_do_sign(digest, dlen, key->dsa); | |
61 | memset(digest, 'd', sizeof(digest)); | |
62 | ||
63 | if (sig == NULL) { | |
64 | error("ssh_dss_sign: sign failed"); | |
65 | return -1; | |
66 | } | |
67 | ||
68 | rlen = BN_num_bytes(sig->r); | |
69 | slen = BN_num_bytes(sig->s); | |
70 | if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { | |
71 | error("bad sig size %u %u", rlen, slen); | |
72 | DSA_SIG_free(sig); | |
73 | return -1; | |
74 | } | |
75 | memset(sigblob, 0, SIGBLOB_LEN); | |
76 | BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); | |
77 | BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); | |
78 | DSA_SIG_free(sig); | |
79 | ||
80 | if (datafellows & SSH_BUG_SIGBLOB) { | |
81 | if (lenp != NULL) | |
82 | *lenp = SIGBLOB_LEN; | |
83 | if (sigp != NULL) { | |
84 | *sigp = xmalloc(SIGBLOB_LEN); | |
85 | memcpy(*sigp, sigblob, SIGBLOB_LEN); | |
86 | } | |
87 | } else { | |
88 | /* ietf-drafts */ | |
89 | buffer_init(&b); | |
90 | buffer_put_cstring(&b, "ssh-dss"); | |
91 | buffer_put_string(&b, sigblob, SIGBLOB_LEN); | |
92 | len = buffer_len(&b); | |
93 | if (lenp != NULL) | |
94 | *lenp = len; | |
95 | if (sigp != NULL) { | |
96 | *sigp = xmalloc(len); | |
97 | memcpy(*sigp, buffer_ptr(&b), len); | |
98 | } | |
99 | buffer_free(&b); | |
100 | } | |
101 | return 0; | |
102 | } | |
103 | int | |
104 | ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, | |
105 | const u_char *data, u_int datalen) | |
106 | { | |
107 | DSA_SIG *sig; | |
108 | const EVP_MD *evp_md = EVP_sha1(); | |
109 | EVP_MD_CTX md; | |
110 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; | |
111 | u_int len, dlen; | |
112 | int rlen, ret; | |
113 | Buffer b; | |
114 | ||
115 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
116 | error("ssh_dss_verify: no DSA key"); | |
117 | return -1; | |
118 | } | |
119 | ||
120 | /* fetch signature */ | |
121 | if (datafellows & SSH_BUG_SIGBLOB) { | |
122 | sigblob = xmalloc(signaturelen); | |
123 | memcpy(sigblob, signature, signaturelen); | |
124 | len = signaturelen; | |
125 | } else { | |
126 | /* ietf-drafts */ | |
127 | char *ktype; | |
128 | buffer_init(&b); | |
129 | buffer_append(&b, signature, signaturelen); | |
130 | ktype = buffer_get_string(&b, NULL); | |
131 | if (strcmp("ssh-dss", ktype) != 0) { | |
132 | error("ssh_dss_verify: cannot handle type %s", ktype); | |
133 | buffer_free(&b); | |
134 | xfree(ktype); | |
135 | return -1; | |
136 | } | |
137 | xfree(ktype); | |
138 | sigblob = buffer_get_string(&b, &len); | |
139 | rlen = buffer_len(&b); | |
140 | buffer_free(&b); | |
141 | if (rlen != 0) { | |
142 | error("ssh_dss_verify: " | |
143 | "remaining bytes in signature %d", rlen); | |
144 | xfree(sigblob); | |
145 | return -1; | |
146 | } | |
147 | } | |
148 | ||
149 | if (len != SIGBLOB_LEN) { | |
150 | fatal("bad sigbloblen %u != SIGBLOB_LEN", len); | |
151 | } | |
152 | ||
153 | /* parse signature */ | |
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"); | |
160 | BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); | |
161 | BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); | |
162 | ||
163 | /* clean up */ | |
164 | memset(sigblob, 0, len); | |
165 | xfree(sigblob); | |
166 | ||
167 | /* sha1 the data */ | |
168 | EVP_DigestInit(&md, evp_md); | |
169 | EVP_DigestUpdate(&md, data, datalen); | |
170 | EVP_DigestFinal(&md, digest, &dlen); | |
171 | ||
172 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); | |
173 | memset(digest, 'd', sizeof(digest)); | |
174 | ||
175 | DSA_SIG_free(sig); | |
176 | ||
177 | debug("ssh_dss_verify: signature %s", | |
178 | ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); | |
179 | return ret; | |
180 | } |