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-rsa.c,v 1.26 2002/08/27 17:13:56 stevesk Exp $");
27
28 #pragma ident "%Z%%M% %I% %E% SMI"
29
30 #include <openssl/opensslconf.h>
31 #include <openssl/evp.h>
32 #include <openssl/err.h>
33
34 #include "xmalloc.h"
35 #include "log.h"
36 #include "buffer.h"
37 #include "bufaux.h"
38 #include "key.h"
39 #include "ssh-rsa.h"
40 #include "compat.h"
41 #include "ssh.h"
42
43 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int , RSA *);
44
45 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
46 int
47 ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp,
48 u_char *data, u_int datalen)
49 {
50 const EVP_MD *evp_md;
51 EVP_MD_CTX md;
52 u_char digest[EVP_MAX_MD_SIZE], *sig;
53 u_int slen, dlen, len;
54 int ok, nid;
55 Buffer b;
56
57 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
58 error("ssh_rsa_sign: no RSA key");
59 return -1;
60 }
61 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
62 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
63 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
64 return -1;
65 }
66 EVP_DigestInit(&md, evp_md);
67 EVP_DigestUpdate(&md, data, datalen);
68 EVP_DigestFinal(&md, digest, &dlen);
69
70 slen = RSA_size(key->rsa);
71 sig = xmalloc(slen);
72
73 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
74 memset(digest, 'd', sizeof(digest));
75
76 if (ok != 1) {
77 int ecode = ERR_get_error();
78 error("ssh_rsa_sign: RSA_sign failed: %s",
79 ERR_error_string(ecode, NULL));
80 xfree(sig);
81 return -1;
82 }
83 if (len < slen) {
84 u_int diff = slen - len;
85 debug("slen %u > len %u", slen, len);
86 memmove(sig + diff, sig, len);
87 memset(sig, 0, diff);
88 } else if (len > slen) {
89 error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
90 xfree(sig);
91 return -1;
92 }
93 /* encode signature */
94 buffer_init(&b);
95 buffer_put_cstring(&b, "ssh-rsa");
96 buffer_put_string(&b, sig, slen);
97 len = buffer_len(&b);
98 if (lenp != NULL)
99 *lenp = len;
100 if (sigp != NULL) {
101 *sigp = xmalloc(len);
102 memcpy(*sigp, buffer_ptr(&b), len);
103 }
104 buffer_free(&b);
105 memset(sig, 's', slen);
106 xfree(sig);
107
108 return 0;
109 }
110
111 int
112 ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen,
113 u_char *data, u_int datalen)
114 {
115 Buffer b;
116 const EVP_MD *evp_md;
117 EVP_MD_CTX md;
118 char *ktype;
119 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
120 u_int len, dlen, modlen;
121 int rlen, ret, nid;
122
123 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
124 error("ssh_rsa_verify: no RSA key");
125 return -1;
126 }
127 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
128 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
129 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
130 return -1;
131 }
132 buffer_init(&b);
133 buffer_append(&b, signature, signaturelen);
134 ktype = buffer_get_string(&b, NULL);
135 if (strcmp("ssh-rsa", ktype) != 0) {
136 error("ssh_rsa_verify: cannot handle type %s", ktype);
137 buffer_free(&b);
138 xfree(ktype);
139 return -1;
140 }
141 xfree(ktype);
142 sigblob = buffer_get_string(&b, &len);
143 rlen = buffer_len(&b);
144 buffer_free(&b);
145 if (rlen != 0) {
146 error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
147 xfree(sigblob);
148 return -1;
149 }
150 /* RSA_verify expects a signature of RSA_size */
151 modlen = RSA_size(key->rsa);
152 if (len > modlen) {
153 error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
154 xfree(sigblob);
155 return -1;
156 } else if (len < modlen) {
157 u_int diff = modlen - len;
158 debug("ssh_rsa_verify: add padding: modlen %u > len %u",
159 modlen, len);
160 sigblob = xrealloc(sigblob, modlen);
161 memmove(sigblob + diff, sigblob, len);
162 memset(sigblob, 0, diff);
163 len = modlen;
164 }
165 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
166 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
167 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
168 xfree(sigblob);
169 return -1;
170 }
171 EVP_DigestInit(&md, evp_md);
172 EVP_DigestUpdate(&md, data, datalen);
173 EVP_DigestFinal(&md, digest, &dlen);
174
175 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
176 memset(digest, 'd', sizeof(digest));
177 memset(sigblob, 's', len);
178 xfree(sigblob);
179 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
180 return ret;
181 }
182
183 /*
184 * See:
185 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
186 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
187 */
188 /*
189 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
190 * oiw(14) secsig(3) algorithms(2) 26 }
191 */
192 static const u_char id_sha1[] = {
193 0x30, 0x21, /* type Sequence, length 0x21 (33) */
194 0x30, 0x09, /* type Sequence, length 0x09 */
195 0x06, 0x05, /* type OID, length 0x05 */
196 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
197 0x05, 0x00, /* NULL */
198 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
199 };
200 /*
201 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
202 * rsadsi(113549) digestAlgorithm(2) 5 }
203 */
204 static const u_char id_md5[] = {
205 0x30, 0x20, /* type Sequence, length 0x20 (32) */
206 0x30, 0x0c, /* type Sequence, length 0x09 */
207 0x06, 0x08, /* type OID, length 0x05 */
208 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
209 0x05, 0x00, /* NULL */
210 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
211 };
212
213 static int
214 openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
215 u_char *sigbuf, u_int siglen, RSA *rsa)
216 {
217 u_int ret, rsasize, oidlen = 0, hlen = 0;
218 int len;
219 const u_char *oid = NULL;
220 u_char *decrypted = NULL;
221
222 ret = 0;
223 switch (type) {
224 case NID_sha1:
225 oid = id_sha1;
226 oidlen = sizeof(id_sha1);
227 hlen = 20;
228 break;
229 case NID_md5:
230 oid = id_md5;
231 oidlen = sizeof(id_md5);
232 hlen = 16;
233 break;
234 default:
235 goto done;
236 break;
237 }
238 if (hashlen != hlen) {
239 error("bad hashlen");
240 goto done;
241 }
242 rsasize = RSA_size(rsa);
243 if (siglen == 0 || siglen > rsasize) {
244 error("bad siglen");
245 goto done;
246 }
247 decrypted = xmalloc(rsasize);
248 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
249 RSA_PKCS1_PADDING)) < 0) {
250 error("RSA_public_decrypt failed: %s",
251 ERR_error_string(ERR_get_error(), NULL));
252 goto done;
253 }
254 if (len != hlen + oidlen) {
255 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
256 goto done;
257 }
258 if (memcmp(decrypted, oid, oidlen) != 0) {
259 error("oid mismatch");
260 goto done;
261 }
262 if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
263 error("hash mismatch");
264 goto done;
265 }
266 ret = 1;
267 done:
268 if (decrypted)
269 xfree(decrypted);
270 return ret;
271 }