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31652869 | 1 | /* $OpenBSD: ssh-rsa.c,v 1.39 2006/08/03 03:34:42 deraadt Exp $ */ |
fa08c86b | 2 | /* |
c1ffd4bd | 3 | * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org> |
fa08c86b | 4 | * |
c1ffd4bd | 5 | * Permission to use, copy, modify, and distribute this software for any |
6 | * purpose with or without fee is hereby granted, provided that the above | |
7 | * copyright notice and this permission notice appear in all copies. | |
fa08c86b | 8 | * |
c1ffd4bd | 9 | * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
10 | * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | |
11 | * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR | |
12 | * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | |
13 | * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | |
14 | * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF | |
15 | * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. | |
fa08c86b | 16 | */ |
31652869 | 17 | |
fa08c86b | 18 | #include "includes.h" |
fa08c86b | 19 | |
31652869 | 20 | #include <sys/types.h> |
21 | ||
fa08c86b | 22 | #include <openssl/evp.h> |
fa08c86b | 23 | #include <openssl/err.h> |
24 | ||
24436b92 | 25 | #include <stdarg.h> |
00146caa | 26 | #include <string.h> |
27 | ||
42f11eb2 | 28 | #include "xmalloc.h" |
29 | #include "log.h" | |
30 | #include "buffer.h" | |
fa08c86b | 31 | #include "key.h" |
a4da628b | 32 | #include "compat.h" |
82b00264 | 33 | #include "ssh.h" |
fa08c86b | 34 | |
b77a87e5 | 35 | static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *); |
0caf874a | 36 | |
fa08c86b | 37 | /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ |
38 | int | |
b6c7b7b7 | 39 | ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp, |
40 | const u_char *data, u_int datalen) | |
fa08c86b | 41 | { |
1a92bd7e | 42 | const EVP_MD *evp_md; |
fa08c86b | 43 | EVP_MD_CTX md; |
eb9f2fab | 44 | u_char digest[EVP_MAX_MD_SIZE], *sig; |
1e3b8b07 | 45 | u_int slen, dlen, len; |
1a92bd7e | 46 | int ok, nid; |
fa08c86b | 47 | Buffer b; |
48 | ||
49 | if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { | |
50 | error("ssh_rsa_sign: no RSA key"); | |
51 | return -1; | |
52 | } | |
a4da628b | 53 | nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; |
1a92bd7e | 54 | if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { |
55 | error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); | |
56 | return -1; | |
57 | } | |
fa08c86b | 58 | EVP_DigestInit(&md, evp_md); |
59 | EVP_DigestUpdate(&md, data, datalen); | |
087dea86 | 60 | EVP_DigestFinal(&md, digest, &dlen); |
fa08c86b | 61 | |
1a92bd7e | 62 | slen = RSA_size(key->rsa); |
63 | sig = xmalloc(slen); | |
64 | ||
65 | ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); | |
087dea86 | 66 | memset(digest, 'd', sizeof(digest)); |
fa08c86b | 67 | |
68 | if (ok != 1) { | |
69 | int ecode = ERR_get_error(); | |
32596c7b | 70 | |
d6133f43 | 71 | error("ssh_rsa_sign: RSA_sign failed: %s", |
72 | ERR_error_string(ecode, NULL)); | |
fa08c86b | 73 | xfree(sig); |
74 | return -1; | |
75 | } | |
76 | if (len < slen) { | |
4004c2ac | 77 | u_int diff = slen - len; |
d6133f43 | 78 | debug("slen %u > len %u", slen, len); |
fa08c86b | 79 | memmove(sig + diff, sig, len); |
80 | memset(sig, 0, diff); | |
81 | } else if (len > slen) { | |
d6133f43 | 82 | error("ssh_rsa_sign: slen %u slen2 %u", slen, len); |
fa08c86b | 83 | xfree(sig); |
84 | return -1; | |
85 | } | |
86 | /* encode signature */ | |
87 | buffer_init(&b); | |
88 | buffer_put_cstring(&b, "ssh-rsa"); | |
89 | buffer_put_string(&b, sig, slen); | |
90 | len = buffer_len(&b); | |
eb9f2fab | 91 | if (lenp != NULL) |
92 | *lenp = len; | |
93 | if (sigp != NULL) { | |
94 | *sigp = xmalloc(len); | |
95 | memcpy(*sigp, buffer_ptr(&b), len); | |
96 | } | |
fa08c86b | 97 | buffer_free(&b); |
98 | memset(sig, 's', slen); | |
99 | xfree(sig); | |
100 | ||
fa08c86b | 101 | return 0; |
102 | } | |
103 | ||
104 | int | |
b6c7b7b7 | 105 | ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen, |
106 | const u_char *data, u_int datalen) | |
fa08c86b | 107 | { |
108 | Buffer b; | |
1a92bd7e | 109 | const EVP_MD *evp_md; |
fa08c86b | 110 | EVP_MD_CTX md; |
111 | char *ktype; | |
087dea86 | 112 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; |
88f24e9d | 113 | u_int len, dlen, modlen; |
1a92bd7e | 114 | int rlen, ret, nid; |
fa08c86b | 115 | |
116 | if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { | |
117 | error("ssh_rsa_verify: no RSA key"); | |
118 | return -1; | |
119 | } | |
82b00264 | 120 | if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { |
b7ced7d1 | 121 | error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", |
122 | BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); | |
b5c334cc | 123 | return -1; |
124 | } | |
fa08c86b | 125 | buffer_init(&b); |
cf54363d | 126 | buffer_append(&b, signature, signaturelen); |
fa08c86b | 127 | ktype = buffer_get_string(&b, NULL); |
128 | if (strcmp("ssh-rsa", ktype) != 0) { | |
129 | error("ssh_rsa_verify: cannot handle type %s", ktype); | |
130 | buffer_free(&b); | |
131 | xfree(ktype); | |
132 | return -1; | |
133 | } | |
134 | xfree(ktype); | |
cf54363d | 135 | sigblob = buffer_get_string(&b, &len); |
fa08c86b | 136 | rlen = buffer_len(&b); |
137 | buffer_free(&b); | |
6aacefa7 | 138 | if (rlen != 0) { |
fa08c86b | 139 | error("ssh_rsa_verify: remaining bytes in signature %d", rlen); |
abc4e9a7 | 140 | xfree(sigblob); |
fa08c86b | 141 | return -1; |
142 | } | |
88f24e9d | 143 | /* RSA_verify expects a signature of RSA_size */ |
144 | modlen = RSA_size(key->rsa); | |
145 | if (len > modlen) { | |
d6133f43 | 146 | error("ssh_rsa_verify: len %u > modlen %u", len, modlen); |
88f24e9d | 147 | xfree(sigblob); |
148 | return -1; | |
149 | } else if (len < modlen) { | |
4004c2ac | 150 | u_int diff = modlen - len; |
d6133f43 | 151 | debug("ssh_rsa_verify: add padding: modlen %u > len %u", |
88f24e9d | 152 | modlen, len); |
c5d10563 | 153 | sigblob = xrealloc(sigblob, 1, modlen); |
88f24e9d | 154 | memmove(sigblob + diff, sigblob, len); |
155 | memset(sigblob, 0, diff); | |
156 | len = modlen; | |
157 | } | |
a4da628b | 158 | nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; |
1a92bd7e | 159 | if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { |
1a92bd7e | 160 | error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); |
abc4e9a7 | 161 | xfree(sigblob); |
1a92bd7e | 162 | return -1; |
163 | } | |
fa08c86b | 164 | EVP_DigestInit(&md, evp_md); |
165 | EVP_DigestUpdate(&md, data, datalen); | |
087dea86 | 166 | EVP_DigestFinal(&md, digest, &dlen); |
fa08c86b | 167 | |
0caf874a | 168 | ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); |
087dea86 | 169 | memset(digest, 'd', sizeof(digest)); |
fa08c86b | 170 | memset(sigblob, 's', len); |
171 | xfree(sigblob); | |
fa08c86b | 172 | debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); |
173 | return ret; | |
174 | } | |
0caf874a | 175 | |
176 | /* | |
177 | * See: | |
178 | * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ | |
179 | * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn | |
180 | */ | |
181 | /* | |
182 | * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) | |
183 | * oiw(14) secsig(3) algorithms(2) 26 } | |
184 | */ | |
185 | static const u_char id_sha1[] = { | |
186 | 0x30, 0x21, /* type Sequence, length 0x21 (33) */ | |
187 | 0x30, 0x09, /* type Sequence, length 0x09 */ | |
188 | 0x06, 0x05, /* type OID, length 0x05 */ | |
189 | 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ | |
190 | 0x05, 0x00, /* NULL */ | |
191 | 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ | |
192 | }; | |
193 | /* | |
194 | * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) | |
195 | * rsadsi(113549) digestAlgorithm(2) 5 } | |
196 | */ | |
197 | static const u_char id_md5[] = { | |
198 | 0x30, 0x20, /* type Sequence, length 0x20 (32) */ | |
199 | 0x30, 0x0c, /* type Sequence, length 0x09 */ | |
200 | 0x06, 0x08, /* type OID, length 0x05 */ | |
201 | 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */ | |
202 | 0x05, 0x00, /* NULL */ | |
203 | 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */ | |
204 | }; | |
205 | ||
206 | static int | |
207 | openssh_RSA_verify(int type, u_char *hash, u_int hashlen, | |
208 | u_char *sigbuf, u_int siglen, RSA *rsa) | |
209 | { | |
b41baf4d | 210 | u_int ret, rsasize, oidlen = 0, hlen = 0; |
211 | int len; | |
0caf874a | 212 | const u_char *oid = NULL; |
213 | u_char *decrypted = NULL; | |
214 | ||
215 | ret = 0; | |
216 | switch (type) { | |
217 | case NID_sha1: | |
218 | oid = id_sha1; | |
219 | oidlen = sizeof(id_sha1); | |
220 | hlen = 20; | |
221 | break; | |
222 | case NID_md5: | |
223 | oid = id_md5; | |
224 | oidlen = sizeof(id_md5); | |
225 | hlen = 16; | |
226 | break; | |
227 | default: | |
228 | goto done; | |
0caf874a | 229 | } |
230 | if (hashlen != hlen) { | |
231 | error("bad hashlen"); | |
232 | goto done; | |
233 | } | |
234 | rsasize = RSA_size(rsa); | |
235 | if (siglen == 0 || siglen > rsasize) { | |
236 | error("bad siglen"); | |
237 | goto done; | |
238 | } | |
239 | decrypted = xmalloc(rsasize); | |
240 | if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, | |
241 | RSA_PKCS1_PADDING)) < 0) { | |
242 | error("RSA_public_decrypt failed: %s", | |
243 | ERR_error_string(ERR_get_error(), NULL)); | |
244 | goto done; | |
245 | } | |
2ceb8101 | 246 | if (len < 0 || (u_int)len != hlen + oidlen) { |
c1ffd4bd | 247 | error("bad decrypted len: %d != %d + %d", len, hlen, oidlen); |
0caf874a | 248 | goto done; |
249 | } | |
250 | if (memcmp(decrypted, oid, oidlen) != 0) { | |
251 | error("oid mismatch"); | |
252 | goto done; | |
253 | } | |
254 | if (memcmp(decrypted + oidlen, hash, hlen) != 0) { | |
255 | error("hash mismatch"); | |
256 | goto done; | |
257 | } | |
258 | ret = 1; | |
259 | done: | |
260 | if (decrypted) | |
261 | xfree(decrypted); | |
262 | return ret; | |
263 | } |