ssh-rsa.c revision 76259 
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 1.8 2001/03/27 10:57:00 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, int *lenp,
44    u_char *data, int datalen)
45{
46	const EVP_MD *evp_md;
47	EVP_MD_CTX md;
48	u_char *digest, *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	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
58	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
59		error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
60		return -1;
61	}
62	dlen = evp_md->md_size;
63	digest = xmalloc(dlen);
64	EVP_DigestInit(&md, evp_md);
65	EVP_DigestUpdate(&md, data, datalen);
66	EVP_DigestFinal(&md, digest, NULL);
67
68	slen = RSA_size(key->rsa);
69	sig = xmalloc(slen);
70
71	ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
72	memset(digest, 'd', dlen);
73	xfree(digest);
74
75	if (ok != 1) {
76		int ecode = ERR_get_error();
77		error("ssh_rsa_sign: RSA_sign failed: %s", ERR_error_string(ecode, NULL));
78		xfree(sig);
79		return -1;
80	}
81	if (len < slen) {
82		int diff = slen - len;
83		debug("slen %d > len %d", slen, len);
84		memmove(sig + diff, sig, len);
85		memset(sig, 0, diff);
86	} else if (len > slen) {
87		error("ssh_rsa_sign: slen %d slen2 %d", slen, len);
88		xfree(sig);
89		return -1;
90	}
91	/* encode signature */
92	buffer_init(&b);
93	buffer_put_cstring(&b, "ssh-rsa");
94	buffer_put_string(&b, sig, slen);
95	len = buffer_len(&b);
96	ret = xmalloc(len);
97	memcpy(ret, buffer_ptr(&b), len);
98	buffer_free(&b);
99	memset(sig, 's', slen);
100	xfree(sig);
101
102	if (lenp != NULL)
103		*lenp = len;
104	if (sigp != NULL)
105		*sigp = ret;
106	debug2("ssh_rsa_sign: done");
107	return 0;
108}
109
110int
111ssh_rsa_verify(
112    Key *key,
113    u_char *signature, int signaturelen,
114    u_char *data, int datalen)
115{
116	Buffer b;
117	const EVP_MD *evp_md;
118	EVP_MD_CTX md;
119	char *ktype;
120	u_char *sigblob, *digest;
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 (BN_num_bits(key->rsa->n) < 768) {
129		error("ssh_rsa_verify: n too small: %d bits",
130		    BN_num_bits(key->rsa->n));
131		return -1;
132	}
133	buffer_init(&b);
134	buffer_append(&b, (char *) signature, signaturelen);
135	ktype = buffer_get_string(&b, NULL);
136	if (strcmp("ssh-rsa", ktype) != 0) {
137		error("ssh_rsa_verify: cannot handle type %s", ktype);
138		buffer_free(&b);
139		xfree(ktype);
140		return -1;
141	}
142	xfree(ktype);
143	sigblob = (u_char *)buffer_get_string(&b, &len);
144	rlen = buffer_len(&b);
145	buffer_free(&b);
146	if(rlen != 0) {
147		xfree(sigblob);
148		error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
149		return -1;
150	}
151	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
152	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
153		xfree(sigblob);
154		error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
155		return -1;
156	}
157	dlen = evp_md->md_size;
158	digest = xmalloc(dlen);
159	EVP_DigestInit(&md, evp_md);
160	EVP_DigestUpdate(&md, data, datalen);
161	EVP_DigestFinal(&md, digest, NULL);
162
163	ret = RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
164	memset(digest, 'd', dlen);
165	xfree(digest);
166	memset(sigblob, 's', len);
167	xfree(sigblob);
168	if (ret == 0) {
169		int ecode = ERR_get_error();
170		error("ssh_rsa_verify: RSA_verify failed: %s", ERR_error_string(ecode, NULL));
171	}
172	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
173	return ret;
174}
175