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3c0ef626 | 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" | |
416fd2a8 | 26 | RCSID("$OpenBSD: ssh-dss.c,v 1.19 2003/11/10 16:23:41 jakob Exp $"); |
3c0ef626 | 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" | |
3c0ef626 | 37 | |
38 | #define INTBLOB_LEN 20 | |
39 | #define SIGBLOB_LEN (2*INTBLOB_LEN) | |
40 | ||
41 | int | |
416fd2a8 | 42 | ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, |
43 | const u_char *data, u_int datalen) | |
3c0ef626 | 44 | { |
45 | DSA_SIG *sig; | |
e9a17296 | 46 | const EVP_MD *evp_md = EVP_sha1(); |
3c0ef626 | 47 | EVP_MD_CTX md; |
e54b3d7c | 48 | u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; |
3c0ef626 | 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 | } | |
3c0ef626 | 56 | EVP_DigestInit(&md, evp_md); |
57 | EVP_DigestUpdate(&md, data, datalen); | |
e9a17296 | 58 | EVP_DigestFinal(&md, digest, &dlen); |
3c0ef626 | 59 | |
60 | sig = DSA_do_sign(digest, dlen, key->dsa); | |
e9a17296 | 61 | memset(digest, 'd', sizeof(digest)); |
3c0ef626 | 62 | |
3c0ef626 | 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) { | |
ff2d7a98 | 71 | error("bad sig size %u %u", rlen, slen); |
3c0ef626 | 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) { | |
3c0ef626 | 81 | if (lenp != NULL) |
82 | *lenp = SIGBLOB_LEN; | |
e54b3d7c | 83 | if (sigp != NULL) { |
84 | *sigp = xmalloc(SIGBLOB_LEN); | |
85 | memcpy(*sigp, sigblob, SIGBLOB_LEN); | |
86 | } | |
3c0ef626 | 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); | |
3c0ef626 | 93 | if (lenp != NULL) |
94 | *lenp = len; | |
e54b3d7c | 95 | if (sigp != NULL) { |
96 | *sigp = xmalloc(len); | |
97 | memcpy(*sigp, buffer_ptr(&b), len); | |
98 | } | |
99 | buffer_free(&b); | |
3c0ef626 | 100 | } |
101 | return 0; | |
102 | } | |
103 | int | |
416fd2a8 | 104 | ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, |
105 | const u_char *data, u_int datalen) | |
3c0ef626 | 106 | { |
107 | DSA_SIG *sig; | |
e9a17296 | 108 | const EVP_MD *evp_md = EVP_sha1(); |
3c0ef626 | 109 | EVP_MD_CTX md; |
e9a17296 | 110 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; |
3c0ef626 | 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) { | |
416fd2a8 | 122 | sigblob = xmalloc(signaturelen); |
123 | memcpy(sigblob, signature, signaturelen); | |
3c0ef626 | 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); | |
e9a17296 | 141 | if (rlen != 0) { |
3c0ef626 | 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) { | |
ff2d7a98 | 150 | fatal("bad sigbloblen %u != SIGBLOB_LEN", len); |
3c0ef626 | 151 | } |
152 | ||
153 | /* parse signature */ | |
e9a17296 | 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"); | |
3c0ef626 | 160 | BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); |
161 | BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); | |
162 | ||
416fd2a8 | 163 | /* clean up */ |
164 | memset(sigblob, 0, len); | |
165 | xfree(sigblob); | |
3c0ef626 | 166 | |
167 | /* sha1 the data */ | |
3c0ef626 | 168 | EVP_DigestInit(&md, evp_md); |
169 | EVP_DigestUpdate(&md, data, datalen); | |
e9a17296 | 170 | EVP_DigestFinal(&md, digest, &dlen); |
3c0ef626 | 171 | |
172 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); | |
e9a17296 | 173 | memset(digest, 'd', sizeof(digest)); |
3c0ef626 | 174 | |
3c0ef626 | 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 | } |