1 /* $OpenBSD: ssh-rsa.c,v 1.67 2018/07/03 11:39:54 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.
22 #include <sys/types.h>
24 #include <openssl/evp.h>
25 #include <openssl/err.h>
33 #define SSHKEY_INTERNAL
38 static int openssh_RSA_verify(int, u_char *, size_t, u_char *, size_t, RSA *);
41 rsa_hash_alg_ident(int hash_alg)
46 case SSH_DIGEST_SHA256:
47 return "rsa-sha2-256";
48 case SSH_DIGEST_SHA512:
49 return "rsa-sha2-512";
55 * Returns the hash algorithm ID for a given algorithm identifier as used
56 * inside the signature blob,
59 rsa_hash_id_from_ident(const char *ident)
61 if (strcmp(ident, "ssh-rsa") == 0)
62 return SSH_DIGEST_SHA1;
63 if (strcmp(ident, "rsa-sha2-256") == 0)
64 return SSH_DIGEST_SHA256;
65 if (strcmp(ident, "rsa-sha2-512") == 0)
66 return SSH_DIGEST_SHA512;
71 * Return the hash algorithm ID for the specified key name. This includes
72 * all the cases of rsa_hash_id_from_ident() but also the certificate key
76 rsa_hash_id_from_keyname(const char *alg)
80 if ((r = rsa_hash_id_from_ident(alg)) != -1)
82 if (strcmp(alg, "ssh-rsa-cert-v01@openssh.com") == 0)
83 return SSH_DIGEST_SHA1;
84 if (strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0)
85 return SSH_DIGEST_SHA256;
86 if (strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0)
87 return SSH_DIGEST_SHA512;
92 rsa_hash_alg_nid(int type)
97 case SSH_DIGEST_SHA256:
99 case SSH_DIGEST_SHA512:
107 ssh_rsa_generate_additional_parameters(struct sshkey *key)
114 if (key == NULL || key->rsa == NULL ||
115 sshkey_type_plain(key->type) != KEY_RSA)
116 return SSH_ERR_INVALID_ARGUMENT;
118 if ((ctx = BN_CTX_new()) == NULL)
119 return SSH_ERR_ALLOC_FAIL;
120 if ((aux = BN_new()) == NULL) {
121 r = SSH_ERR_ALLOC_FAIL;
124 BN_set_flags(aux, BN_FLG_CONSTTIME);
127 BN_with_flags(&d, key->rsa->d, BN_FLG_CONSTTIME);
129 if ((BN_sub(aux, key->rsa->q, BN_value_one()) == 0) ||
130 (BN_mod(key->rsa->dmq1, &d, aux, ctx) == 0) ||
131 (BN_sub(aux, key->rsa->p, BN_value_one()) == 0) ||
132 (BN_mod(key->rsa->dmp1, &d, aux, ctx) == 0)) {
133 r = SSH_ERR_LIBCRYPTO_ERROR;
143 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
145 ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
146 const u_char *data, size_t datalen, const char *alg_ident)
148 u_char digest[SSH_DIGEST_MAX_LENGTH], *sig = NULL;
151 int nid, hash_alg, ret = SSH_ERR_INTERNAL_ERROR;
152 struct sshbuf *b = NULL;
159 if (alg_ident == NULL || strlen(alg_ident) == 0)
160 hash_alg = SSH_DIGEST_SHA1;
162 hash_alg = rsa_hash_id_from_keyname(alg_ident);
163 if (key == NULL || key->rsa == NULL || hash_alg == -1 ||
164 sshkey_type_plain(key->type) != KEY_RSA)
165 return SSH_ERR_INVALID_ARGUMENT;
166 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
167 return SSH_ERR_KEY_LENGTH;
168 slen = RSA_size(key->rsa);
169 if (slen <= 0 || slen > SSHBUF_MAX_BIGNUM)
170 return SSH_ERR_INVALID_ARGUMENT;
173 nid = rsa_hash_alg_nid(hash_alg);
174 if ((dlen = ssh_digest_bytes(hash_alg)) == 0)
175 return SSH_ERR_INTERNAL_ERROR;
176 if ((ret = ssh_digest_memory(hash_alg, data, datalen,
177 digest, sizeof(digest))) != 0)
180 if ((sig = malloc(slen)) == NULL) {
181 ret = SSH_ERR_ALLOC_FAIL;
185 if (RSA_sign(nid, digest, dlen, sig, &len, key->rsa) != 1) {
186 ret = SSH_ERR_LIBCRYPTO_ERROR;
190 size_t diff = slen - len;
191 memmove(sig + diff, sig, len);
192 explicit_bzero(sig, diff);
193 } else if (len > slen) {
194 ret = SSH_ERR_INTERNAL_ERROR;
197 /* encode signature */
198 if ((b = sshbuf_new()) == NULL) {
199 ret = SSH_ERR_ALLOC_FAIL;
202 if ((ret = sshbuf_put_cstring(b, rsa_hash_alg_ident(hash_alg))) != 0 ||
203 (ret = sshbuf_put_string(b, sig, slen)) != 0)
207 if ((*sigp = malloc(len)) == NULL) {
208 ret = SSH_ERR_ALLOC_FAIL;
211 memcpy(*sigp, sshbuf_ptr(b), len);
217 explicit_bzero(digest, sizeof(digest));
224 ssh_rsa_verify(const struct sshkey *key,
225 const u_char *sig, size_t siglen, const u_char *data, size_t datalen,
228 char *sigtype = NULL;
229 int hash_alg, want_alg, ret = SSH_ERR_INTERNAL_ERROR;
230 size_t len = 0, diff, modlen, dlen;
231 struct sshbuf *b = NULL;
232 u_char digest[SSH_DIGEST_MAX_LENGTH], *osigblob, *sigblob = NULL;
234 if (key == NULL || key->rsa == NULL ||
235 sshkey_type_plain(key->type) != KEY_RSA ||
236 sig == NULL || siglen == 0)
237 return SSH_ERR_INVALID_ARGUMENT;
238 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
239 return SSH_ERR_KEY_LENGTH;
241 if ((b = sshbuf_from(sig, siglen)) == NULL)
242 return SSH_ERR_ALLOC_FAIL;
243 if (sshbuf_get_cstring(b, &sigtype, NULL) != 0) {
244 ret = SSH_ERR_INVALID_FORMAT;
247 if ((hash_alg = rsa_hash_id_from_ident(sigtype)) == -1) {
248 ret = SSH_ERR_KEY_TYPE_MISMATCH;
252 * Allow ssh-rsa-cert-v01 certs to generate SHA2 signatures for
253 * legacy reasons, but otherwise the signature type should match.
255 if (alg != NULL && strcmp(alg, "ssh-rsa-cert-v01@openssh.com") != 0) {
256 if ((want_alg = rsa_hash_id_from_keyname(alg)) == -1) {
257 ret = SSH_ERR_INVALID_ARGUMENT;
260 if (hash_alg != want_alg) {
261 ret = SSH_ERR_SIGNATURE_INVALID;
265 if (sshbuf_get_string(b, &sigblob, &len) != 0) {
266 ret = SSH_ERR_INVALID_FORMAT;
269 if (sshbuf_len(b) != 0) {
270 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
273 /* RSA_verify expects a signature of RSA_size */
274 modlen = RSA_size(key->rsa);
276 ret = SSH_ERR_KEY_BITS_MISMATCH;
278 } else if (len < modlen) {
281 if ((sigblob = realloc(sigblob, modlen)) == NULL) {
282 sigblob = osigblob; /* put it back for clear/free */
283 ret = SSH_ERR_ALLOC_FAIL;
286 memmove(sigblob + diff, sigblob, len);
287 explicit_bzero(sigblob, diff);
290 if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
291 ret = SSH_ERR_INTERNAL_ERROR;
294 if ((ret = ssh_digest_memory(hash_alg, data, datalen,
295 digest, sizeof(digest))) != 0)
298 ret = openssh_RSA_verify(hash_alg, digest, dlen, sigblob, len,
301 freezero(sigblob, len);
304 explicit_bzero(digest, sizeof(digest));
310 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
311 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
315 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
316 * oiw(14) secsig(3) algorithms(2) 26 }
318 static const u_char id_sha1[] = {
319 0x30, 0x21, /* type Sequence, length 0x21 (33) */
320 0x30, 0x09, /* type Sequence, length 0x09 */
321 0x06, 0x05, /* type OID, length 0x05 */
322 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
323 0x05, 0x00, /* NULL */
324 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
328 * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html
329 * id-sha256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840)
330 * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2)
333 static const u_char id_sha256[] = {
334 0x30, 0x31, /* type Sequence, length 0x31 (49) */
335 0x30, 0x0d, /* type Sequence, length 0x0d (13) */
336 0x06, 0x09, /* type OID, length 0x09 */
337 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, /* id-sha256 */
338 0x05, 0x00, /* NULL */
339 0x04, 0x20 /* Octet string, length 0x20 (32), followed by sha256 hash */
343 * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html
344 * id-sha512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840)
345 * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2)
348 static const u_char id_sha512[] = {
349 0x30, 0x51, /* type Sequence, length 0x51 (81) */
350 0x30, 0x0d, /* type Sequence, length 0x0d (13) */
351 0x06, 0x09, /* type OID, length 0x09 */
352 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, /* id-sha512 */
353 0x05, 0x00, /* NULL */
354 0x04, 0x40 /* Octet string, length 0x40 (64), followed by sha512 hash */
358 rsa_hash_alg_oid(int hash_alg, const u_char **oidp, size_t *oidlenp)
361 case SSH_DIGEST_SHA1:
363 *oidlenp = sizeof(id_sha1);
365 case SSH_DIGEST_SHA256:
367 *oidlenp = sizeof(id_sha256);
369 case SSH_DIGEST_SHA512:
371 *oidlenp = sizeof(id_sha512);
374 return SSH_ERR_INVALID_ARGUMENT;
380 openssh_RSA_verify(int hash_alg, u_char *hash, size_t hashlen,
381 u_char *sigbuf, size_t siglen, RSA *rsa)
383 size_t rsasize = 0, oidlen = 0, hlen = 0;
384 int ret, len, oidmatch, hashmatch;
385 const u_char *oid = NULL;
386 u_char *decrypted = NULL;
388 if ((ret = rsa_hash_alg_oid(hash_alg, &oid, &oidlen)) != 0)
390 ret = SSH_ERR_INTERNAL_ERROR;
391 hlen = ssh_digest_bytes(hash_alg);
392 if (hashlen != hlen) {
393 ret = SSH_ERR_INVALID_ARGUMENT;
396 rsasize = RSA_size(rsa);
397 if (rsasize <= 0 || rsasize > SSHBUF_MAX_BIGNUM ||
398 siglen == 0 || siglen > rsasize) {
399 ret = SSH_ERR_INVALID_ARGUMENT;
402 if ((decrypted = malloc(rsasize)) == NULL) {
403 ret = SSH_ERR_ALLOC_FAIL;
406 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
407 RSA_PKCS1_PADDING)) < 0) {
408 ret = SSH_ERR_LIBCRYPTO_ERROR;
411 if (len < 0 || (size_t)len != hlen + oidlen) {
412 ret = SSH_ERR_INVALID_FORMAT;
415 oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
416 hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
417 if (!oidmatch || !hashmatch) {
418 ret = SSH_ERR_SIGNATURE_INVALID;
423 freezero(decrypted, rsasize);
426 #endif /* WITH_OPENSSL */