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c1cb7bae | 1 | /* $OpenBSD: ssh-dss.c,v 1.21 2006/03/25 13:17:02 djm Exp $ */ |
4f8c6159 | 2 | /* |
3 | * Copyright (c) 2000 Markus Friedl. All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms, with or without | |
6 | * modification, are permitted provided that the following conditions | |
7 | * are met: | |
8 | * 1. Redistributions of source code must retain the above copyright | |
9 | * notice, this list of conditions and the following disclaimer. | |
10 | * 2. Redistributions in binary form must reproduce the above copyright | |
11 | * notice, this list of conditions and the following disclaimer in the | |
12 | * documentation and/or other materials provided with the distribution. | |
4f8c6159 | 13 | * |
14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
15 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
16 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
17 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
18 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
19 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
20 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
21 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
22 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
23 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
24 | */ | |
25 | ||
26 | #include "includes.h" | |
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 |
b6c7b7b7 | 42 | ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, |
43 | const u_char *data, u_int datalen) | |
4f8c6159 | 44 | { |
4f8c6159 | 45 | DSA_SIG *sig; |
714954dc | 46 | const EVP_MD *evp_md = EVP_sha1(); |
4f8c6159 | 47 | EVP_MD_CTX md; |
eb9f2fab | 48 | u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; |
d87596b0 | 49 | u_int rlen, slen, len, dlen; |
4f8c6159 | 50 | Buffer b; |
51 | ||
52 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 53 | error("ssh_dss_sign: no DSA key"); |
4f8c6159 | 54 | return -1; |
55 | } | |
4f8c6159 | 56 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 57 | EVP_DigestUpdate(&md, data, datalen); |
087dea86 | 58 | EVP_DigestFinal(&md, digest, &dlen); |
4f8c6159 | 59 | |
42f11eb2 | 60 | sig = DSA_do_sign(digest, dlen, key->dsa); |
087dea86 | 61 | memset(digest, 'd', sizeof(digest)); |
d87596b0 | 62 | |
d87596b0 | 63 | if (sig == NULL) { |
64 | error("ssh_dss_sign: sign failed"); | |
65 | return -1; | |
66 | } | |
4f8c6159 | 67 | |
68 | rlen = BN_num_bytes(sig->r); | |
69 | slen = BN_num_bytes(sig->s); | |
70 | if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { | |
d6133f43 | 71 | error("bad sig size %u %u", rlen, slen); |
4f8c6159 | 72 | DSA_SIG_free(sig); |
73 | return -1; | |
74 | } | |
4f8c6159 | 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 | ||
d0c832f3 | 80 | if (datafellows & SSH_BUG_SIGBLOB) { |
4f8c6159 | 81 | if (lenp != NULL) |
82 | *lenp = SIGBLOB_LEN; | |
eb9f2fab | 83 | if (sigp != NULL) { |
84 | *sigp = xmalloc(SIGBLOB_LEN); | |
85 | memcpy(*sigp, sigblob, SIGBLOB_LEN); | |
86 | } | |
4f8c6159 | 87 | } else { |
88 | /* ietf-drafts */ | |
89 | buffer_init(&b); | |
fa08c86b | 90 | buffer_put_cstring(&b, "ssh-dss"); |
4f8c6159 | 91 | buffer_put_string(&b, sigblob, SIGBLOB_LEN); |
92 | len = buffer_len(&b); | |
4f8c6159 | 93 | if (lenp != NULL) |
94 | *lenp = len; | |
eb9f2fab | 95 | if (sigp != NULL) { |
96 | *sigp = xmalloc(len); | |
97 | memcpy(*sigp, buffer_ptr(&b), len); | |
98 | } | |
99 | buffer_free(&b); | |
4f8c6159 | 100 | } |
101 | return 0; | |
102 | } | |
103 | int | |
b6c7b7b7 | 104 | ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, |
105 | const u_char *data, u_int datalen) | |
4f8c6159 | 106 | { |
4f8c6159 | 107 | DSA_SIG *sig; |
714954dc | 108 | const EVP_MD *evp_md = EVP_sha1(); |
4f8c6159 | 109 | EVP_MD_CTX md; |
087dea86 | 110 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; |
1e3b8b07 | 111 | u_int len, dlen; |
d87596b0 | 112 | int rlen, ret; |
113 | Buffer b; | |
4f8c6159 | 114 | |
115 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 116 | error("ssh_dss_verify: no DSA key"); |
4f8c6159 | 117 | return -1; |
118 | } | |
119 | ||
4f8c6159 | 120 | /* fetch signature */ |
d0c832f3 | 121 | if (datafellows & SSH_BUG_SIGBLOB) { |
b6c7b7b7 | 122 | sigblob = xmalloc(signaturelen); |
123 | memcpy(sigblob, signature, signaturelen); | |
4f8c6159 | 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 | |
b6c7b7b7 | 163 | /* clean up */ |
164 | memset(sigblob, 0, len); | |
165 | xfree(sigblob); | |
2b87da3b | 166 | |
a306f2dd | 167 | /* sha1 the data */ |
4f8c6159 | 168 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 169 | EVP_DigestUpdate(&md, data, datalen); |
087dea86 | 170 | EVP_DigestFinal(&md, digest, &dlen); |
4f8c6159 | 171 | |
fa08c86b | 172 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); |
087dea86 | 173 | memset(digest, 'd', sizeof(digest)); |
4f8c6159 | 174 | |
4f8c6159 | 175 | DSA_SIG_free(sig); |
176 | ||
d87596b0 | 177 | debug("ssh_dss_verify: signature %s", |
178 | ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); | |
4f8c6159 | 179 | return ret; |
180 | } |