1 /* $OpenBSD: ssh-rsa.c,v 1.51 2014/02/02 03:44:31 djm Exp $ */
3 * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
20 #include <sys/types.h>
22 #include <openssl/evp.h>
23 #include <openssl/err.h>
37 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
39 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
41 ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
42 const u_char *data, u_int datalen)
45 u_char digest[SSH_DIGEST_MAX_LENGTH], *sig;
46 u_int slen, dlen, len;
50 if (key == NULL || key_type_plain(key->type) != KEY_RSA ||
52 error("%s: no RSA key", __func__);
57 hash_alg = SSH_DIGEST_SHA1;
59 if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
60 error("%s: bad hash algorithm %d", __func__, hash_alg);
63 if (ssh_digest_memory(hash_alg, data, datalen,
64 digest, sizeof(digest)) != 0) {
65 error("%s: ssh_digest_memory failed", __func__);
69 slen = RSA_size(key->rsa);
72 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
73 explicit_bzero(digest, sizeof(digest));
76 int ecode = ERR_get_error();
78 error("%s: RSA_sign failed: %s", __func__,
79 ERR_error_string(ecode, NULL));
84 u_int diff = slen - len;
85 debug("slen %u > len %u", slen, len);
86 memmove(sig + diff, sig, len);
87 explicit_bzero(sig, diff);
88 } else if (len > slen) {
89 error("%s: slen %u slen2 %u", __func__, slen, len);
93 /* encode signature */
95 buffer_put_cstring(&b, "ssh-rsa");
96 buffer_put_string(&b, sig, slen);
101 *sigp = xmalloc(len);
102 memcpy(*sigp, buffer_ptr(&b), len);
105 explicit_bzero(sig, slen);
112 ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
113 const u_char *data, u_int datalen)
118 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob;
119 u_int len, dlen, modlen;
122 if (key == NULL || key_type_plain(key->type) != KEY_RSA ||
124 error("%s: no RSA key", __func__);
128 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
129 error("%s: RSA modulus too small: %d < minimum %d bits",
130 __func__, BN_num_bits(key->rsa->n),
131 SSH_RSA_MINIMUM_MODULUS_SIZE);
135 buffer_append(&b, signature, signaturelen);
136 ktype = buffer_get_cstring(&b, NULL);
137 if (strcmp("ssh-rsa", ktype) != 0) {
138 error("%s: cannot handle type %s", __func__, ktype);
144 sigblob = buffer_get_string(&b, &len);
145 rlen = buffer_len(&b);
148 error("%s: remaining bytes in signature %d", __func__, rlen);
152 /* RSA_verify expects a signature of RSA_size */
153 modlen = RSA_size(key->rsa);
155 error("%s: len %u > modlen %u", __func__, len, modlen);
158 } else if (len < modlen) {
159 u_int diff = modlen - len;
160 debug("%s: add padding: modlen %u > len %u", __func__,
162 sigblob = xrealloc(sigblob, 1, modlen);
163 memmove(sigblob + diff, sigblob, len);
164 explicit_bzero(sigblob, diff);
168 hash_alg = SSH_DIGEST_SHA1;
169 if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
170 error("%s: bad hash algorithm %d", __func__, hash_alg);
173 if (ssh_digest_memory(hash_alg, data, datalen,
174 digest, sizeof(digest)) != 0) {
175 error("%s: ssh_digest_memory failed", __func__);
179 ret = openssh_RSA_verify(hash_alg, digest, dlen, sigblob, len,
181 explicit_bzero(digest, sizeof(digest));
182 explicit_bzero(sigblob, len);
184 debug("%s: signature %scorrect", __func__, (ret == 0) ? "in" : "");
190 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
191 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
194 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
195 * oiw(14) secsig(3) algorithms(2) 26 }
197 static const u_char id_sha1[] = {
198 0x30, 0x21, /* type Sequence, length 0x21 (33) */
199 0x30, 0x09, /* type Sequence, length 0x09 */
200 0x06, 0x05, /* type OID, length 0x05 */
201 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
202 0x05, 0x00, /* NULL */
203 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
207 openssh_RSA_verify(int hash_alg, u_char *hash, u_int hashlen,
208 u_char *sigbuf, u_int siglen, RSA *rsa)
210 u_int ret, rsasize, oidlen = 0, hlen = 0;
211 int len, oidmatch, hashmatch;
212 const u_char *oid = NULL;
213 u_char *decrypted = NULL;
217 case SSH_DIGEST_SHA1:
219 oidlen = sizeof(id_sha1);
225 if (hashlen != hlen) {
226 error("bad hashlen");
229 rsasize = RSA_size(rsa);
230 if (siglen == 0 || siglen > rsasize) {
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));
241 if (len < 0 || (u_int)len != hlen + oidlen) {
242 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
245 oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
246 hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
248 error("oid mismatch");
252 error("hash mismatch");