1 /* $OpenBSD: ssh-rsa.c,v 1.39 2006/08/03 03:34:42 deraadt 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>
34 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
36 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
38 ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
39 const u_char *data, u_int datalen)
43 u_char digest[EVP_MAX_MD_SIZE], *sig;
44 u_int slen, dlen, len;
48 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
49 error("ssh_rsa_sign: no RSA key");
52 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
53 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
54 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
57 EVP_DigestInit(&md, evp_md);
58 EVP_DigestUpdate(&md, data, datalen);
59 EVP_DigestFinal(&md, digest, &dlen);
61 slen = RSA_size(key->rsa);
64 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
65 memset(digest, 'd', sizeof(digest));
68 int ecode = ERR_get_error();
70 error("ssh_rsa_sign: RSA_sign failed: %s",
71 ERR_error_string(ecode, NULL));
76 u_int diff = slen - len;
77 debug("slen %u > len %u", slen, len);
78 memmove(sig + diff, sig, len);
80 } else if (len > slen) {
81 error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
85 /* encode signature */
87 buffer_put_cstring(&b, "ssh-rsa");
88 buffer_put_string(&b, sig, slen);
94 memcpy(*sigp, buffer_ptr(&b), len);
97 memset(sig, 's', slen);
104 ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
105 const u_char *data, u_int datalen)
108 const EVP_MD *evp_md;
111 u_char digest[EVP_MAX_MD_SIZE], *sigblob;
112 u_int len, dlen, modlen;
115 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
116 error("ssh_rsa_verify: no RSA key");
119 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
120 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
121 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
125 buffer_append(&b, signature, signaturelen);
126 ktype = buffer_get_string(&b, NULL);
127 if (strcmp("ssh-rsa", ktype) != 0) {
128 error("ssh_rsa_verify: cannot handle type %s", ktype);
134 sigblob = buffer_get_string(&b, &len);
135 rlen = buffer_len(&b);
138 error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
142 /* RSA_verify expects a signature of RSA_size */
143 modlen = RSA_size(key->rsa);
145 error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
148 } else if (len < modlen) {
149 u_int diff = modlen - len;
150 debug("ssh_rsa_verify: add padding: modlen %u > len %u",
152 sigblob = xrealloc(sigblob, 1, modlen);
153 memmove(sigblob + diff, sigblob, len);
154 memset(sigblob, 0, diff);
157 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
158 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
159 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
163 EVP_DigestInit(&md, evp_md);
164 EVP_DigestUpdate(&md, data, datalen);
165 EVP_DigestFinal(&md, digest, &dlen);
167 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
168 memset(digest, 'd', sizeof(digest));
169 memset(sigblob, 's', len);
171 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
177 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
178 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
181 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
182 * oiw(14) secsig(3) algorithms(2) 26 }
184 static const u_char id_sha1[] = {
185 0x30, 0x21, /* type Sequence, length 0x21 (33) */
186 0x30, 0x09, /* type Sequence, length 0x09 */
187 0x06, 0x05, /* type OID, length 0x05 */
188 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
189 0x05, 0x00, /* NULL */
190 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
193 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
194 * rsadsi(113549) digestAlgorithm(2) 5 }
196 static const u_char id_md5[] = {
197 0x30, 0x20, /* type Sequence, length 0x20 (32) */
198 0x30, 0x0c, /* type Sequence, length 0x09 */
199 0x06, 0x08, /* type OID, length 0x05 */
200 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
201 0x05, 0x00, /* NULL */
202 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
206 openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
207 u_char *sigbuf, u_int siglen, RSA *rsa)
209 u_int ret, rsasize, oidlen = 0, hlen = 0;
211 const u_char *oid = NULL;
212 u_char *decrypted = NULL;
218 oidlen = sizeof(id_sha1);
223 oidlen = sizeof(id_md5);
229 if (hashlen != hlen) {
230 error("bad hashlen");
233 rsasize = RSA_size(rsa);
234 if (siglen == 0 || siglen > rsasize) {
238 decrypted = xmalloc(rsasize);
239 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
240 RSA_PKCS1_PADDING)) < 0) {
241 error("RSA_public_decrypt failed: %s",
242 ERR_error_string(ERR_get_error(), NULL));
245 if (len < 0 || (u_int)len != hlen + oidlen) {
246 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
249 if (memcmp(decrypted, oid, oidlen) != 0) {
250 error("oid mismatch");
253 if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
254 error("hash mismatch");