blob: eb422d07e9c70d701b08de043610991625688dac [file] [log] [blame]
Damien Miller0bc1bd82000-11-13 22:57:25 +11001/*
Darren Tuckera251f802003-06-22 20:45:15 +10002 * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
Damien Miller0bc1bd82000-11-13 22:57:25 +11003 *
Darren Tuckera251f802003-06-22 20:45:15 +10004 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
Damien Miller0bc1bd82000-11-13 22:57:25 +11007 *
Darren Tuckera251f802003-06-22 20:45:15 +10008 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
Damien Miller0bc1bd82000-11-13 22:57:25 +110015 */
Damien Miller0bc1bd82000-11-13 22:57:25 +110016#include "includes.h"
Damien Millereccb9de2005-06-17 12:59:34 +100017RCSID("$OpenBSD: ssh-rsa.c,v 1.32 2005/06/17 02:44:33 djm Exp $");
Damien Miller0bc1bd82000-11-13 22:57:25 +110018
19#include <openssl/evp.h>
Damien Miller0bc1bd82000-11-13 22:57:25 +110020#include <openssl/err.h>
21
Ben Lindstrom226cfa02001-01-22 05:34:40 +000022#include "xmalloc.h"
23#include "log.h"
24#include "buffer.h"
25#include "bufaux.h"
Damien Miller0bc1bd82000-11-13 22:57:25 +110026#include "key.h"
Ben Lindstrom60a43812001-03-29 00:32:56 +000027#include "compat.h"
Ben Lindstrom03f39322002-04-02 20:43:11 +000028#include "ssh.h"
Damien Miller0bc1bd82000-11-13 22:57:25 +110029
Ben Lindstrom93576d92002-12-23 02:06:19 +000030static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
Ben Lindstrom0deb5d92002-08-20 18:40:03 +000031
Damien Miller0bc1bd82000-11-13 22:57:25 +110032/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
33int
Damien Millerf58b58c2003-11-17 21:18:23 +110034ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
35 const u_char *data, u_int datalen)
Damien Miller0bc1bd82000-11-13 22:57:25 +110036{
Ben Lindstrom425fb022001-03-29 00:31:20 +000037 const EVP_MD *evp_md;
Damien Miller0bc1bd82000-11-13 22:57:25 +110038 EVP_MD_CTX md;
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000039 u_char digest[EVP_MAX_MD_SIZE], *sig;
Ben Lindstrom46c16222000-12-22 01:43:59 +000040 u_int slen, dlen, len;
Ben Lindstrom425fb022001-03-29 00:31:20 +000041 int ok, nid;
Damien Miller0bc1bd82000-11-13 22:57:25 +110042 Buffer b;
43
44 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
45 error("ssh_rsa_sign: no RSA key");
46 return -1;
47 }
Ben Lindstrom60a43812001-03-29 00:32:56 +000048 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
Ben Lindstrom425fb022001-03-29 00:31:20 +000049 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
50 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
51 return -1;
52 }
Damien Miller0bc1bd82000-11-13 22:57:25 +110053 EVP_DigestInit(&md, evp_md);
54 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +110055 EVP_DigestFinal(&md, digest, &dlen);
Damien Miller0bc1bd82000-11-13 22:57:25 +110056
Ben Lindstrom425fb022001-03-29 00:31:20 +000057 slen = RSA_size(key->rsa);
58 sig = xmalloc(slen);
59
60 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
Damien Millerc516e922002-02-05 11:53:43 +110061 memset(digest, 'd', sizeof(digest));
Damien Miller0bc1bd82000-11-13 22:57:25 +110062
63 if (ok != 1) {
64 int ecode = ERR_get_error();
Ben Lindstrom5c385522002-06-23 21:23:20 +000065 error("ssh_rsa_sign: RSA_sign failed: %s",
66 ERR_error_string(ecode, NULL));
Damien Miller0bc1bd82000-11-13 22:57:25 +110067 xfree(sig);
68 return -1;
69 }
70 if (len < slen) {
Ben Lindstrom0e50d842002-08-20 18:39:14 +000071 u_int diff = slen - len;
Ben Lindstrom5c385522002-06-23 21:23:20 +000072 debug("slen %u > len %u", slen, len);
Damien Miller0bc1bd82000-11-13 22:57:25 +110073 memmove(sig + diff, sig, len);
74 memset(sig, 0, diff);
75 } else if (len > slen) {
Ben Lindstrom5c385522002-06-23 21:23:20 +000076 error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
Damien Miller0bc1bd82000-11-13 22:57:25 +110077 xfree(sig);
78 return -1;
79 }
80 /* encode signature */
81 buffer_init(&b);
82 buffer_put_cstring(&b, "ssh-rsa");
83 buffer_put_string(&b, sig, slen);
84 len = buffer_len(&b);
Ben Lindstrom2bf759c2002-07-07 22:13:31 +000085 if (lenp != NULL)
86 *lenp = len;
87 if (sigp != NULL) {
88 *sigp = xmalloc(len);
89 memcpy(*sigp, buffer_ptr(&b), len);
90 }
Damien Miller0bc1bd82000-11-13 22:57:25 +110091 buffer_free(&b);
92 memset(sig, 's', slen);
93 xfree(sig);
94
Damien Miller0bc1bd82000-11-13 22:57:25 +110095 return 0;
96}
97
98int
Damien Millerf58b58c2003-11-17 21:18:23 +110099ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
100 const u_char *data, u_int datalen)
Damien Miller0bc1bd82000-11-13 22:57:25 +1100101{
102 Buffer b;
Ben Lindstrom425fb022001-03-29 00:31:20 +0000103 const EVP_MD *evp_md;
Damien Miller0bc1bd82000-11-13 22:57:25 +1100104 EVP_MD_CTX md;
105 char *ktype;
Damien Millerc516e922002-02-05 11:53:43 +1100106 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
Ben Lindstromceae9d12002-06-06 20:55:04 +0000107 u_int len, dlen, modlen;
Ben Lindstrom425fb022001-03-29 00:31:20 +0000108 int rlen, ret, nid;
Damien Miller0bc1bd82000-11-13 22:57:25 +1100109
110 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
111 error("ssh_rsa_verify: no RSA key");
112 return -1;
113 }
Ben Lindstrom03f39322002-04-02 20:43:11 +0000114 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
Ben Lindstrom2779d282002-06-11 15:47:42 +0000115 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
116 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
Ben Lindstrombf555ba2001-01-18 02:04:35 +0000117 return -1;
118 }
Damien Miller0bc1bd82000-11-13 22:57:25 +1100119 buffer_init(&b);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000120 buffer_append(&b, signature, signaturelen);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100121 ktype = buffer_get_string(&b, NULL);
122 if (strcmp("ssh-rsa", ktype) != 0) {
123 error("ssh_rsa_verify: cannot handle type %s", ktype);
124 buffer_free(&b);
125 xfree(ktype);
126 return -1;
127 }
128 xfree(ktype);
Ben Lindstrom9e0ddd42001-09-18 05:41:19 +0000129 sigblob = buffer_get_string(&b, &len);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100130 rlen = buffer_len(&b);
131 buffer_free(&b);
Ben Lindstrom1c37c6a2001-12-06 18:00:18 +0000132 if (rlen != 0) {
Damien Miller0bc1bd82000-11-13 22:57:25 +1100133 error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
Damien Miller36e603d2001-11-12 11:03:35 +1100134 xfree(sigblob);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100135 return -1;
136 }
Ben Lindstromceae9d12002-06-06 20:55:04 +0000137 /* RSA_verify expects a signature of RSA_size */
138 modlen = RSA_size(key->rsa);
139 if (len > modlen) {
Ben Lindstrom5c385522002-06-23 21:23:20 +0000140 error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
Ben Lindstromceae9d12002-06-06 20:55:04 +0000141 xfree(sigblob);
142 return -1;
143 } else if (len < modlen) {
Ben Lindstrom0e50d842002-08-20 18:39:14 +0000144 u_int diff = modlen - len;
Ben Lindstrom5c385522002-06-23 21:23:20 +0000145 debug("ssh_rsa_verify: add padding: modlen %u > len %u",
Ben Lindstromceae9d12002-06-06 20:55:04 +0000146 modlen, len);
147 sigblob = xrealloc(sigblob, modlen);
148 memmove(sigblob + diff, sigblob, len);
149 memset(sigblob, 0, diff);
150 len = modlen;
151 }
Ben Lindstrom60a43812001-03-29 00:32:56 +0000152 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
Ben Lindstrom425fb022001-03-29 00:31:20 +0000153 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
Ben Lindstrom425fb022001-03-29 00:31:20 +0000154 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
Damien Miller36e603d2001-11-12 11:03:35 +1100155 xfree(sigblob);
Ben Lindstrom425fb022001-03-29 00:31:20 +0000156 return -1;
157 }
Damien Miller0bc1bd82000-11-13 22:57:25 +1100158 EVP_DigestInit(&md, evp_md);
159 EVP_DigestUpdate(&md, data, datalen);
Damien Millerc516e922002-02-05 11:53:43 +1100160 EVP_DigestFinal(&md, digest, &dlen);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100161
Ben Lindstrom0deb5d92002-08-20 18:40:03 +0000162 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
Damien Millerc516e922002-02-05 11:53:43 +1100163 memset(digest, 'd', sizeof(digest));
Damien Miller0bc1bd82000-11-13 22:57:25 +1100164 memset(sigblob, 's', len);
165 xfree(sigblob);
Damien Miller0bc1bd82000-11-13 22:57:25 +1100166 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
167 return ret;
168}
Ben Lindstrom0deb5d92002-08-20 18:40:03 +0000169
170/*
171 * See:
172 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
173 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
174 */
175/*
176 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
177 * oiw(14) secsig(3) algorithms(2) 26 }
178 */
179static const u_char id_sha1[] = {
180 0x30, 0x21, /* type Sequence, length 0x21 (33) */
181 0x30, 0x09, /* type Sequence, length 0x09 */
182 0x06, 0x05, /* type OID, length 0x05 */
183 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
184 0x05, 0x00, /* NULL */
185 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
186};
187/*
188 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
189 * rsadsi(113549) digestAlgorithm(2) 5 }
190 */
191static const u_char id_md5[] = {
192 0x30, 0x20, /* type Sequence, length 0x20 (32) */
193 0x30, 0x0c, /* type Sequence, length 0x09 */
194 0x06, 0x08, /* type OID, length 0x05 */
195 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
196 0x05, 0x00, /* NULL */
197 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
198};
199
200static int
201openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
202 u_char *sigbuf, u_int siglen, RSA *rsa)
203{
Damien Millerf7c23912002-09-04 16:39:48 +1000204 u_int ret, rsasize, oidlen = 0, hlen = 0;
205 int len;
Ben Lindstrom0deb5d92002-08-20 18:40:03 +0000206 const u_char *oid = NULL;
207 u_char *decrypted = NULL;
208
209 ret = 0;
210 switch (type) {
211 case NID_sha1:
212 oid = id_sha1;
213 oidlen = sizeof(id_sha1);
214 hlen = 20;
215 break;
216 case NID_md5:
217 oid = id_md5;
218 oidlen = sizeof(id_md5);
219 hlen = 16;
220 break;
221 default:
222 goto done;
223 break;
224 }
225 if (hashlen != hlen) {
226 error("bad hashlen");
227 goto done;
228 }
229 rsasize = RSA_size(rsa);
230 if (siglen == 0 || siglen > rsasize) {
231 error("bad siglen");
232 goto done;
233 }
234 decrypted = xmalloc(rsasize);
235 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
236 RSA_PKCS1_PADDING)) < 0) {
237 error("RSA_public_decrypt failed: %s",
238 ERR_error_string(ERR_get_error(), NULL));
239 goto done;
240 }
Damien Millereccb9de2005-06-17 12:59:34 +1000241 if (len < 0 || (u_int)len != hlen + oidlen) {
Darren Tuckera251f802003-06-22 20:45:15 +1000242 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
Ben Lindstrom0deb5d92002-08-20 18:40:03 +0000243 goto done;
244 }
245 if (memcmp(decrypted, oid, oidlen) != 0) {
246 error("oid mismatch");
247 goto done;
248 }
249 if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
250 error("hash mismatch");
251 goto done;
252 }
253 ret = 1;
254done:
255 if (decrypted)
256 xfree(decrypted);
257 return ret;
258}