xref: /titanic_41/usr/src/cmd/ssh/libssh/common/ssh-rsa.c (revision 7c478bd95313f5f23a4c958a745db2134aa03244)
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/evp.h>
31 #include <openssl/err.h>
32 
33 #include "xmalloc.h"
34 #include "log.h"
35 #include "buffer.h"
36 #include "bufaux.h"
37 #include "key.h"
38 #include "ssh-rsa.h"
39 #include "compat.h"
40 #include "ssh.h"
41 
42 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int , RSA *);
43 
44 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
45 int
ssh_rsa_sign(Key * key,u_char ** sigp,u_int * lenp,u_char * data,u_int datalen)46 ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp,
47     u_char *data, u_int datalen)
48 {
49 	const EVP_MD *evp_md;
50 	EVP_MD_CTX md;
51 	u_char digest[EVP_MAX_MD_SIZE], *sig;
52 	u_int slen, dlen, len;
53 	int ok, nid;
54 	Buffer b;
55 
56 	if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
57 		error("ssh_rsa_sign: no RSA key");
58 		return -1;
59 	}
60 	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
61 	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
62 		error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
63 		return -1;
64 	}
65 	EVP_DigestInit(&md, evp_md);
66 	EVP_DigestUpdate(&md, data, datalen);
67 	EVP_DigestFinal(&md, digest, &dlen);
68 
69 	slen = RSA_size(key->rsa);
70 	sig = xmalloc(slen);
71 
72 	ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
73 	memset(digest, 'd', sizeof(digest));
74 
75 	if (ok != 1) {
76 		int ecode = ERR_get_error();
77 		error("ssh_rsa_sign: RSA_sign failed: %s",
78 		    ERR_error_string(ecode, NULL));
79 		xfree(sig);
80 		return -1;
81 	}
82 	if (len < slen) {
83 		u_int diff = slen - len;
84 		debug("slen %u > len %u", slen, len);
85 		memmove(sig + diff, sig, len);
86 		memset(sig, 0, diff);
87 	} else if (len > slen) {
88 		error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
89 		xfree(sig);
90 		return -1;
91 	}
92 	/* encode signature */
93 	buffer_init(&b);
94 	buffer_put_cstring(&b, "ssh-rsa");
95 	buffer_put_string(&b, sig, slen);
96 	len = buffer_len(&b);
97 	if (lenp != NULL)
98 		*lenp = len;
99 	if (sigp != NULL) {
100 		*sigp = xmalloc(len);
101 		memcpy(*sigp, buffer_ptr(&b), len);
102 	}
103 	buffer_free(&b);
104 	memset(sig, 's', slen);
105 	xfree(sig);
106 
107 	return 0;
108 }
109 
110 int
ssh_rsa_verify(Key * key,u_char * signature,u_int signaturelen,u_char * data,u_int datalen)111 ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen,
112     u_char *data, u_int datalen)
113 {
114 	Buffer b;
115 	const EVP_MD *evp_md;
116 	EVP_MD_CTX md;
117 	char *ktype;
118 	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
119 	u_int len, dlen, modlen;
120 	int rlen, ret, nid;
121 
122 	if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
123 		error("ssh_rsa_verify: no RSA key");
124 		return -1;
125 	}
126 	if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
127 		error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
128 		    BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
129 		return -1;
130 	}
131 	buffer_init(&b);
132 	buffer_append(&b, signature, signaturelen);
133 	ktype = buffer_get_string(&b, NULL);
134 	if (strcmp("ssh-rsa", ktype) != 0) {
135 		error("ssh_rsa_verify: cannot handle type %s", ktype);
136 		buffer_free(&b);
137 		xfree(ktype);
138 		return -1;
139 	}
140 	xfree(ktype);
141 	sigblob = buffer_get_string(&b, &len);
142 	rlen = buffer_len(&b);
143 	buffer_free(&b);
144 	if (rlen != 0) {
145 		error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
146 		xfree(sigblob);
147 		return -1;
148 	}
149 	/* RSA_verify expects a signature of RSA_size */
150 	modlen = RSA_size(key->rsa);
151 	if (len > modlen) {
152 		error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
153 		xfree(sigblob);
154 		return -1;
155 	} else if (len < modlen) {
156 		u_int diff = modlen - len;
157 		debug("ssh_rsa_verify: add padding: modlen %u > len %u",
158 		    modlen, len);
159 		sigblob = xrealloc(sigblob, modlen);
160 		memmove(sigblob + diff, sigblob, len);
161 		memset(sigblob, 0, diff);
162 		len = modlen;
163 	}
164 	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
165 	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
166 		error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
167 		xfree(sigblob);
168 		return -1;
169 	}
170 	EVP_DigestInit(&md, evp_md);
171 	EVP_DigestUpdate(&md, data, datalen);
172 	EVP_DigestFinal(&md, digest, &dlen);
173 
174 	ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
175 	memset(digest, 'd', sizeof(digest));
176 	memset(sigblob, 's', len);
177 	xfree(sigblob);
178 	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
179 	return ret;
180 }
181 
182 /*
183  * See:
184  * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
185  * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
186  */
187 /*
188  * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
189  *	oiw(14) secsig(3) algorithms(2) 26 }
190  */
191 static const u_char id_sha1[] = {
192 	0x30, 0x21, /* type Sequence, length 0x21 (33) */
193 	0x30, 0x09, /* type Sequence, length 0x09 */
194 	0x06, 0x05, /* type OID, length 0x05 */
195 	0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
196 	0x05, 0x00, /* NULL */
197 	0x04, 0x14  /* Octet string, length 0x14 (20), followed by sha1 hash */
198 };
199 /*
200  * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
201  *	rsadsi(113549) digestAlgorithm(2) 5 }
202  */
203 static const u_char id_md5[] = {
204 	0x30, 0x20, /* type Sequence, length 0x20 (32) */
205 	0x30, 0x0c, /* type Sequence, length 0x09 */
206 	0x06, 0x08, /* type OID, length 0x05 */
207 	0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
208 	0x05, 0x00, /* NULL */
209 	0x04, 0x10  /* Octet string, length 0x10 (16), followed by md5 hash */
210 };
211 
212 static int
openssh_RSA_verify(int type,u_char * hash,u_int hashlen,u_char * sigbuf,u_int siglen,RSA * rsa)213 openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
214     u_char *sigbuf, u_int siglen, RSA *rsa)
215 {
216 	u_int ret, rsasize, oidlen = 0, hlen = 0;
217 	int len;
218 	const u_char *oid = NULL;
219 	u_char *decrypted = NULL;
220 
221 	ret = 0;
222 	switch (type) {
223 	case NID_sha1:
224 		oid = id_sha1;
225 		oidlen = sizeof(id_sha1);
226 		hlen = 20;
227 		break;
228 	case NID_md5:
229 		oid = id_md5;
230 		oidlen = sizeof(id_md5);
231 		hlen = 16;
232 		break;
233 	default:
234 		goto done;
235 		break;
236 	}
237 	if (hashlen != hlen) {
238 		error("bad hashlen");
239 		goto done;
240 	}
241 	rsasize = RSA_size(rsa);
242 	if (siglen == 0 || siglen > rsasize) {
243 		error("bad siglen");
244 		goto done;
245 	}
246 	decrypted = xmalloc(rsasize);
247 	if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
248 	    RSA_PKCS1_PADDING)) < 0) {
249 		error("RSA_public_decrypt failed: %s",
250 		    ERR_error_string(ERR_get_error(), NULL));
251 		goto done;
252 	}
253 	if (len != hlen + oidlen) {
254 		error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
255 		goto done;
256 	}
257 	if (memcmp(decrypted, oid, oidlen) != 0) {
258 		error("oid mismatch");
259 		goto done;
260 	}
261 	if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
262 		error("hash mismatch");
263 		goto done;
264 	}
265 	ret = 1;
266 done:
267 	if (decrypted)
268 		xfree(decrypted);
269 	return ret;
270 }
271