ssh-rsa.c revision 98675 
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"
26RCSID("$OpenBSD: ssh-rsa.c,v 1.20 2002/06/10 16:53:06 stevesk Exp $");
27
28#include <openssl/evp.h>
29#include <openssl/err.h>
30
31#include "xmalloc.h"
32#include "log.h"
33#include "buffer.h"
34#include "bufaux.h"
35#include "key.h"
36#include "ssh-rsa.h"
37#include "compat.h"
38#include "ssh.h"
39
40/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
41int
42ssh_rsa_sign(
43    Key *key,
44    u_char **sigp, u_int *lenp,
45    u_char *data, u_int datalen)
46{
47	const EVP_MD *evp_md;
48	EVP_MD_CTX md;
49	u_char digest[EVP_MAX_MD_SIZE], *sig, *ret;
50	u_int slen, dlen, len;
51	int ok, nid;
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	}
58	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
59	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
60		error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
61		return -1;
62	}
63	EVP_DigestInit(&md, evp_md);
64	EVP_DigestUpdate(&md, data, datalen);
65	EVP_DigestFinal(&md, digest, &dlen);
66
67	slen = RSA_size(key->rsa);
68	sig = xmalloc(slen);
69
70	ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
71	memset(digest, 'd', sizeof(digest));
72
73	if (ok != 1) {
74		int ecode = ERR_get_error();
75		error("ssh_rsa_sign: RSA_sign failed: %s", ERR_error_string(ecode, NULL));
76		xfree(sig);
77		return -1;
78	}
79	if (len < slen) {
80		int diff = slen - len;
81		debug("slen %d > len %d", slen, len);
82		memmove(sig + diff, sig, len);
83		memset(sig, 0, diff);
84	} else if (len > slen) {
85		error("ssh_rsa_sign: slen %d slen2 %d", slen, len);
86		xfree(sig);
87		return -1;
88	}
89	/* encode signature */
90	buffer_init(&b);
91	buffer_put_cstring(&b, "ssh-rsa");
92	buffer_put_string(&b, sig, slen);
93	len = buffer_len(&b);
94	ret = xmalloc(len);
95	memcpy(ret, buffer_ptr(&b), len);
96	buffer_free(&b);
97	memset(sig, 's', slen);
98	xfree(sig);
99
100	if (lenp != NULL)
101		*lenp = len;
102	if (sigp != NULL)
103		*sigp = ret;
104	return 0;
105}
106
107int
108ssh_rsa_verify(
109    Key *key,
110    u_char *signature, u_int signaturelen,
111    u_char *data, u_int datalen)
112{
113	Buffer b;
114	const EVP_MD *evp_md;
115	EVP_MD_CTX md;
116	char *ktype;
117	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
118	u_int len, dlen, modlen;
119	int rlen, ret, nid;
120
121	if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
122		error("ssh_rsa_verify: no RSA key");
123		return -1;
124	}
125	if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
126		error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
127		    BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
128		return -1;
129	}
130	buffer_init(&b);
131	buffer_append(&b, signature, signaturelen);
132	ktype = buffer_get_string(&b, NULL);
133	if (strcmp("ssh-rsa", ktype) != 0) {
134		error("ssh_rsa_verify: cannot handle type %s", ktype);
135		buffer_free(&b);
136		xfree(ktype);
137		return -1;
138	}
139	xfree(ktype);
140	sigblob = buffer_get_string(&b, &len);
141	rlen = buffer_len(&b);
142	buffer_free(&b);
143	if (rlen != 0) {
144		error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
145		xfree(sigblob);
146		return -1;
147	}
148	/* RSA_verify expects a signature of RSA_size */
149	modlen = RSA_size(key->rsa);
150	if (len > modlen) {
151		error("ssh_rsa_verify: len %d > modlen %d", len, modlen);
152		xfree(sigblob);
153		return -1;
154	} else if (len < modlen) {
155		int diff = modlen - len;
156		debug("ssh_rsa_verify: add padding: modlen %d > len %d",
157		    modlen, len);
158		sigblob = xrealloc(sigblob, modlen);
159		memmove(sigblob + diff, sigblob, len);
160		memset(sigblob, 0, diff);
161		len = modlen;
162	}
163	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
164	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
165		error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
166		xfree(sigblob);
167		return -1;
168	}
169	EVP_DigestInit(&md, evp_md);
170	EVP_DigestUpdate(&md, data, datalen);
171	EVP_DigestFinal(&md, digest, &dlen);
172
173	ret = RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
174	memset(digest, 'd', sizeof(digest));
175	memset(sigblob, 's', len);
176	xfree(sigblob);
177	if (ret == 0) {
178		int ecode = ERR_get_error();
179		error("ssh_rsa_verify: RSA_verify failed: %s", ERR_error_string(ecode, NULL));
180	}
181	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
182	return ret;
183}
184