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fa08c86b | 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" | |
0caf874a | 26 | RCSID("$OpenBSD: ssh-rsa.c,v 1.25 2002/08/02 22:20:30 markus Exp $"); |
fa08c86b | 27 | |
28 | #include <openssl/evp.h> | |
fa08c86b | 29 | #include <openssl/err.h> |
30 | ||
42f11eb2 | 31 | #include "xmalloc.h" |
32 | #include "log.h" | |
33 | #include "buffer.h" | |
34 | #include "bufaux.h" | |
fa08c86b | 35 | #include "key.h" |
5ca51e19 | 36 | #include "ssh-rsa.h" |
a4da628b | 37 | #include "compat.h" |
82b00264 | 38 | #include "ssh.h" |
fa08c86b | 39 | |
0caf874a | 40 | static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int , RSA *); |
41 | ||
fa08c86b | 42 | /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ |
43 | int | |
d6133f43 | 44 | ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp, |
c66f9d0e | 45 | u_char *data, u_int datalen) |
fa08c86b | 46 | { |
1a92bd7e | 47 | const EVP_MD *evp_md; |
fa08c86b | 48 | EVP_MD_CTX md; |
eb9f2fab | 49 | u_char digest[EVP_MAX_MD_SIZE], *sig; |
1e3b8b07 | 50 | u_int slen, dlen, len; |
1a92bd7e | 51 | int ok, nid; |
fa08c86b | 52 | Buffer b; |
53 | ||
54 | if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { | |
55 | error("ssh_rsa_sign: no RSA key"); | |
56 | return -1; | |
57 | } | |
a4da628b | 58 | nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; |
1a92bd7e | 59 | if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { |
60 | error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); | |
61 | return -1; | |
62 | } | |
fa08c86b | 63 | EVP_DigestInit(&md, evp_md); |
64 | EVP_DigestUpdate(&md, data, datalen); | |
087dea86 | 65 | EVP_DigestFinal(&md, digest, &dlen); |
fa08c86b | 66 | |
1a92bd7e | 67 | slen = RSA_size(key->rsa); |
68 | sig = xmalloc(slen); | |
69 | ||
70 | ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); | |
087dea86 | 71 | memset(digest, 'd', sizeof(digest)); |
fa08c86b | 72 | |
73 | if (ok != 1) { | |
74 | int ecode = ERR_get_error(); | |
d6133f43 | 75 | error("ssh_rsa_sign: RSA_sign failed: %s", |
76 | ERR_error_string(ecode, NULL)); | |
fa08c86b | 77 | xfree(sig); |
78 | return -1; | |
79 | } | |
80 | if (len < slen) { | |
4004c2ac | 81 | u_int diff = slen - len; |
d6133f43 | 82 | debug("slen %u > len %u", slen, len); |
fa08c86b | 83 | memmove(sig + diff, sig, len); |
84 | memset(sig, 0, diff); | |
85 | } else if (len > slen) { | |
d6133f43 | 86 | error("ssh_rsa_sign: slen %u slen2 %u", slen, len); |
fa08c86b | 87 | xfree(sig); |
88 | return -1; | |
89 | } | |
90 | /* encode signature */ | |
91 | buffer_init(&b); | |
92 | buffer_put_cstring(&b, "ssh-rsa"); | |
93 | buffer_put_string(&b, sig, slen); | |
94 | len = buffer_len(&b); | |
eb9f2fab | 95 | if (lenp != NULL) |
96 | *lenp = len; | |
97 | if (sigp != NULL) { | |
98 | *sigp = xmalloc(len); | |
99 | memcpy(*sigp, buffer_ptr(&b), len); | |
100 | } | |
fa08c86b | 101 | buffer_free(&b); |
102 | memset(sig, 's', slen); | |
103 | xfree(sig); | |
104 | ||
fa08c86b | 105 | return 0; |
106 | } | |
107 | ||
108 | int | |
d6133f43 | 109 | ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen, |
c66f9d0e | 110 | u_char *data, u_int datalen) |
fa08c86b | 111 | { |
112 | Buffer b; | |
1a92bd7e | 113 | const EVP_MD *evp_md; |
fa08c86b | 114 | EVP_MD_CTX md; |
115 | char *ktype; | |
087dea86 | 116 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; |
88f24e9d | 117 | u_int len, dlen, modlen; |
1a92bd7e | 118 | int rlen, ret, nid; |
fa08c86b | 119 | |
120 | if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { | |
121 | error("ssh_rsa_verify: no RSA key"); | |
122 | return -1; | |
123 | } | |
82b00264 | 124 | if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { |
b7ced7d1 | 125 | error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", |
126 | BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); | |
b5c334cc | 127 | return -1; |
128 | } | |
fa08c86b | 129 | buffer_init(&b); |
cf54363d | 130 | buffer_append(&b, signature, signaturelen); |
fa08c86b | 131 | ktype = buffer_get_string(&b, NULL); |
132 | if (strcmp("ssh-rsa", ktype) != 0) { | |
133 | error("ssh_rsa_verify: cannot handle type %s", ktype); | |
134 | buffer_free(&b); | |
135 | xfree(ktype); | |
136 | return -1; | |
137 | } | |
138 | xfree(ktype); | |
cf54363d | 139 | sigblob = buffer_get_string(&b, &len); |
fa08c86b | 140 | rlen = buffer_len(&b); |
141 | buffer_free(&b); | |
6aacefa7 | 142 | if (rlen != 0) { |
fa08c86b | 143 | error("ssh_rsa_verify: remaining bytes in signature %d", rlen); |
abc4e9a7 | 144 | xfree(sigblob); |
fa08c86b | 145 | return -1; |
146 | } | |
88f24e9d | 147 | /* RSA_verify expects a signature of RSA_size */ |
148 | modlen = RSA_size(key->rsa); | |
149 | if (len > modlen) { | |
d6133f43 | 150 | error("ssh_rsa_verify: len %u > modlen %u", len, modlen); |
88f24e9d | 151 | xfree(sigblob); |
152 | return -1; | |
153 | } else if (len < modlen) { | |
4004c2ac | 154 | u_int diff = modlen - len; |
d6133f43 | 155 | debug("ssh_rsa_verify: add padding: modlen %u > len %u", |
88f24e9d | 156 | modlen, len); |
157 | sigblob = xrealloc(sigblob, modlen); | |
158 | memmove(sigblob + diff, sigblob, len); | |
159 | memset(sigblob, 0, diff); | |
160 | len = modlen; | |
161 | } | |
a4da628b | 162 | nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; |
1a92bd7e | 163 | if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { |
1a92bd7e | 164 | error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); |
abc4e9a7 | 165 | xfree(sigblob); |
1a92bd7e | 166 | return -1; |
167 | } | |
fa08c86b | 168 | EVP_DigestInit(&md, evp_md); |
169 | EVP_DigestUpdate(&md, data, datalen); | |
087dea86 | 170 | EVP_DigestFinal(&md, digest, &dlen); |
fa08c86b | 171 | |
0caf874a | 172 | ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); |
087dea86 | 173 | memset(digest, 'd', sizeof(digest)); |
fa08c86b | 174 | memset(sigblob, 's', len); |
175 | xfree(sigblob); | |
fa08c86b | 176 | debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); |
177 | return ret; | |
178 | } | |
0caf874a | 179 | |
180 | /* | |
181 | * See: | |
182 | * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ | |
183 | * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn | |
184 | */ | |
185 | /* | |
186 | * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) | |
187 | * oiw(14) secsig(3) algorithms(2) 26 } | |
188 | */ | |
189 | static const u_char id_sha1[] = { | |
190 | 0x30, 0x21, /* type Sequence, length 0x21 (33) */ | |
191 | 0x30, 0x09, /* type Sequence, length 0x09 */ | |
192 | 0x06, 0x05, /* type OID, length 0x05 */ | |
193 | 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ | |
194 | 0x05, 0x00, /* NULL */ | |
195 | 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ | |
196 | }; | |
197 | /* | |
198 | * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) | |
199 | * rsadsi(113549) digestAlgorithm(2) 5 } | |
200 | */ | |
201 | static const u_char id_md5[] = { | |
202 | 0x30, 0x20, /* type Sequence, length 0x20 (32) */ | |
203 | 0x30, 0x0c, /* type Sequence, length 0x09 */ | |
204 | 0x06, 0x08, /* type OID, length 0x05 */ | |
205 | 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */ | |
206 | 0x05, 0x00, /* NULL */ | |
207 | 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */ | |
208 | }; | |
209 | ||
210 | static int | |
211 | openssh_RSA_verify(int type, u_char *hash, u_int hashlen, | |
212 | u_char *sigbuf, u_int siglen, RSA *rsa) | |
213 | { | |
214 | u_int ret, rsasize, len, oidlen = 0, hlen = 0; | |
215 | const u_char *oid = NULL; | |
216 | u_char *decrypted = NULL; | |
217 | ||
218 | ret = 0; | |
219 | switch (type) { | |
220 | case NID_sha1: | |
221 | oid = id_sha1; | |
222 | oidlen = sizeof(id_sha1); | |
223 | hlen = 20; | |
224 | break; | |
225 | case NID_md5: | |
226 | oid = id_md5; | |
227 | oidlen = sizeof(id_md5); | |
228 | hlen = 16; | |
229 | break; | |
230 | default: | |
231 | goto done; | |
232 | break; | |
233 | } | |
234 | if (hashlen != hlen) { | |
235 | error("bad hashlen"); | |
236 | goto done; | |
237 | } | |
238 | rsasize = RSA_size(rsa); | |
239 | if (siglen == 0 || siglen > rsasize) { | |
240 | error("bad siglen"); | |
241 | goto done; | |
242 | } | |
243 | decrypted = xmalloc(rsasize); | |
244 | if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, | |
245 | RSA_PKCS1_PADDING)) < 0) { | |
246 | error("RSA_public_decrypt failed: %s", | |
247 | ERR_error_string(ERR_get_error(), NULL)); | |
248 | goto done; | |
249 | } | |
250 | if (len != hlen + oidlen) { | |
251 | error("bad decrypted len: %d != %d + %d", len, hlen, oidlen); | |
252 | goto done; | |
253 | } | |
254 | if (memcmp(decrypted, oid, oidlen) != 0) { | |
255 | error("oid mismatch"); | |
256 | goto done; | |
257 | } | |
258 | if (memcmp(decrypted + oidlen, hash, hlen) != 0) { | |
259 | error("hash mismatch"); | |
260 | goto done; | |
261 | } | |
262 | ret = 1; | |
263 | done: | |
264 | if (decrypted) | |
265 | xfree(decrypted); | |
266 | return ret; | |
267 | } |