ssh-rsa.c revision 92555 
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 1.16 2002/02/24 19:14:59 markus 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
39/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
40int
41ssh_rsa_sign(
42    Key *key,
43    u_char **sigp, u_int *lenp,
44    u_char *data, u_int datalen)
45{
46	const EVP_MD *evp_md;
47	EVP_MD_CTX md;
48	u_char digest[EVP_MAX_MD_SIZE], *sig, *ret;
49	u_int slen, dlen, len;
50	int ok, nid;
51	Buffer b;
52
53	if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
54		error("ssh_rsa_sign: no RSA key");
55		return -1;
56	}
57	if (datafellows & SSH_BUG_SIGBLOB) {
58		error("ssh_rsa_sign: SSH_BUG_SIGBLOB not supported");
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", ERR_error_string(ecode, NULL));
79		xfree(sig);
80		return -1;
81	}
82	if (len < slen) {
83		int diff = slen - len;
84		debug("slen %d > len %d", slen, len);
85		memmove(sig + diff, sig, len);
86		memset(sig, 0, diff);
87	} else if (len > slen) {
88		error("ssh_rsa_sign: slen %d slen2 %d", 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	ret = xmalloc(len);
98	memcpy(ret, buffer_ptr(&b), len);
99	buffer_free(&b);
100	memset(sig, 's', slen);
101	xfree(sig);
102
103	if (lenp != NULL)
104		*lenp = len;
105	if (sigp != NULL)
106		*sigp = ret;
107	return 0;
108}
109
110int
111ssh_rsa_verify(
112    Key *key,
113    u_char *signature, u_int signaturelen,
114    u_char *data, u_int datalen)
115{
116	Buffer b;
117	const EVP_MD *evp_md;
118	EVP_MD_CTX md;
119	char *ktype;
120	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
121	u_int len, dlen;
122	int rlen, ret, nid;
123
124	if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
125		error("ssh_rsa_verify: no RSA key");
126		return -1;
127	}
128	if (datafellows & SSH_BUG_SIGBLOB) {
129		error("ssh_rsa_verify: SSH_BUG_SIGBLOB not supported");
130		return -1;
131	}
132	if (BN_num_bits(key->rsa->n) < 768) {
133		error("ssh_rsa_verify: n too small: %d bits",
134		    BN_num_bits(key->rsa->n));
135		return -1;
136	}
137	buffer_init(&b);
138	buffer_append(&b, signature, signaturelen);
139	ktype = buffer_get_string(&b, NULL);
140	if (strcmp("ssh-rsa", ktype) != 0) {
141		error("ssh_rsa_verify: cannot handle type %s", ktype);
142		buffer_free(&b);
143		xfree(ktype);
144		return -1;
145	}
146	xfree(ktype);
147	sigblob = buffer_get_string(&b, &len);
148	rlen = buffer_len(&b);
149	buffer_free(&b);
150	if (rlen != 0) {
151		error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
152		xfree(sigblob);
153		return -1;
154	}
155	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
156	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
157		error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
158		xfree(sigblob);
159		return -1;
160	}
161	EVP_DigestInit(&md, evp_md);
162	EVP_DigestUpdate(&md, data, datalen);
163	EVP_DigestFinal(&md, digest, &dlen);
164
165	ret = RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
166	memset(digest, 'd', sizeof(digest));
167	memset(sigblob, 's', len);
168	xfree(sigblob);
169	if (ret == 0) {
170		int ecode = ERR_get_error();
171		error("ssh_rsa_verify: RSA_verify failed: %s", ERR_error_string(ecode, NULL));
172	}
173	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
174	return ret;
175}
176