1 /* $NetBSD: ssh-xmss.c,v 1.6 2023/07/26 17:58:16 christos Exp $ */
2 /* $OpenBSD: ssh-xmss.c,v 1.14 2022/10/28 00:44:44 djm Exp $*/
3 /*
4 * Copyright (c) 2017 Stefan-Lukas Gazdag.
5 * Copyright (c) 2017 Markus Friedl.
6 *
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18 */
19 #include "includes.h"
20 __RCSID("$NetBSD: ssh-xmss.c,v 1.6 2023/07/26 17:58:16 christos Exp $");
21 #define SSHKEY_INTERNAL
22 #include <sys/types.h>
23 #include <limits.h>
24
25 #include <stdlib.h>
26 #include <string.h>
27 #include <stdarg.h>
28 #include <stdint.h>
29 #include <unistd.h>
30
31 #include "log.h"
32 #include "sshbuf.h"
33 #include "sshkey.h"
34 #include "sshkey-xmss.h"
35 #include "ssherr.h"
36 #include "ssh.h"
37
38 #include "xmss_fast.h"
39
40 static void
ssh_xmss_cleanup(struct sshkey * k)41 ssh_xmss_cleanup(struct sshkey *k)
42 {
43 freezero(k->xmss_pk, sshkey_xmss_pklen(k));
44 freezero(k->xmss_sk, sshkey_xmss_sklen(k));
45 sshkey_xmss_free_state(k);
46 free(k->xmss_name);
47 free(k->xmss_filename);
48 k->xmss_pk = NULL;
49 k->xmss_sk = NULL;
50 k->xmss_name = NULL;
51 k->xmss_filename = NULL;
52 }
53
54 static int
ssh_xmss_equal(const struct sshkey * a,const struct sshkey * b)55 ssh_xmss_equal(const struct sshkey *a, const struct sshkey *b)
56 {
57 if (a->xmss_pk == NULL || b->xmss_pk == NULL)
58 return 0;
59 if (sshkey_xmss_pklen(a) != sshkey_xmss_pklen(b))
60 return 0;
61 if (memcmp(a->xmss_pk, b->xmss_pk, sshkey_xmss_pklen(a)) != 0)
62 return 0;
63 return 1;
64 }
65
66 static int
ssh_xmss_serialize_public(const struct sshkey * key,struct sshbuf * b,enum sshkey_serialize_rep opts)67 ssh_xmss_serialize_public(const struct sshkey *key, struct sshbuf *b,
68 enum sshkey_serialize_rep opts)
69 {
70 int r;
71
72 if (key->xmss_name == NULL || key->xmss_pk == NULL ||
73 sshkey_xmss_pklen(key) == 0)
74 return SSH_ERR_INVALID_ARGUMENT;
75 if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 ||
76 (r = sshbuf_put_string(b, key->xmss_pk,
77 sshkey_xmss_pklen(key))) != 0 ||
78 (r = sshkey_xmss_serialize_pk_info(key, b, opts)) != 0)
79 return r;
80
81 return 0;
82 }
83
84 static int
ssh_xmss_serialize_private(const struct sshkey * key,struct sshbuf * b,enum sshkey_serialize_rep opts)85 ssh_xmss_serialize_private(const struct sshkey *key, struct sshbuf *b,
86 enum sshkey_serialize_rep opts)
87 {
88 int r;
89
90 if (key->xmss_name == NULL)
91 return SSH_ERR_INVALID_ARGUMENT;
92 /* Note: can't reuse ssh_xmss_serialize_public because of sk order */
93 if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 ||
94 (r = sshbuf_put_string(b, key->xmss_pk,
95 sshkey_xmss_pklen(key))) != 0 ||
96 (r = sshbuf_put_string(b, key->xmss_sk,
97 sshkey_xmss_sklen(key))) != 0 ||
98 (r = sshkey_xmss_serialize_state_opt(key, b, opts)) != 0)
99 return r;
100
101 return 0;
102 }
103
104 static int
ssh_xmss_copy_public(const struct sshkey * from,struct sshkey * to)105 ssh_xmss_copy_public(const struct sshkey *from, struct sshkey *to)
106 {
107 int r = SSH_ERR_INTERNAL_ERROR;
108 u_int32_t left;
109 size_t pklen;
110
111 if ((r = sshkey_xmss_init(to, from->xmss_name)) != 0)
112 return r;
113 if (from->xmss_pk == NULL)
114 return 0; /* XXX SSH_ERR_INTERNAL_ERROR ? */
115
116 if ((pklen = sshkey_xmss_pklen(from)) == 0 ||
117 sshkey_xmss_pklen(to) != pklen)
118 return SSH_ERR_INTERNAL_ERROR;
119 if ((to->xmss_pk = malloc(pklen)) == NULL)
120 return SSH_ERR_ALLOC_FAIL;
121 memcpy(to->xmss_pk, from->xmss_pk, pklen);
122 /* simulate number of signatures left on pubkey */
123 left = sshkey_xmss_signatures_left(from);
124 if (left)
125 sshkey_xmss_enable_maxsign(to, left);
126 return 0;
127 }
128
129 static int
ssh_xmss_deserialize_public(const char * ktype,struct sshbuf * b,struct sshkey * key)130 ssh_xmss_deserialize_public(const char *ktype, struct sshbuf *b,
131 struct sshkey *key)
132 {
133 size_t len = 0;
134 char *xmss_name = NULL;
135 u_char *pk = NULL;
136 int ret = SSH_ERR_INTERNAL_ERROR;
137
138 if ((ret = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0)
139 goto out;
140 if ((ret = sshkey_xmss_init(key, xmss_name)) != 0)
141 goto out;
142 if ((ret = sshbuf_get_string(b, &pk, &len)) != 0)
143 goto out;
144 if (len == 0 || len != sshkey_xmss_pklen(key)) {
145 ret = SSH_ERR_INVALID_FORMAT;
146 goto out;
147 }
148 key->xmss_pk = pk;
149 pk = NULL;
150 if (!sshkey_is_cert(key) &&
151 (ret = sshkey_xmss_deserialize_pk_info(key, b)) != 0)
152 goto out;
153 /* success */
154 ret = 0;
155 out:
156 free(xmss_name);
157 freezero(pk, len);
158 return ret;
159 }
160
161 static int
ssh_xmss_deserialize_private(const char * ktype,struct sshbuf * b,struct sshkey * key)162 ssh_xmss_deserialize_private(const char *ktype, struct sshbuf *b,
163 struct sshkey *key)
164 {
165 int r;
166 char *xmss_name = NULL;
167 size_t pklen = 0, sklen = 0;
168 u_char *xmss_pk = NULL, *xmss_sk = NULL;
169
170 /* Note: can't reuse ssh_xmss_deserialize_public because of sk order */
171 if ((r = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0 ||
172 (r = sshbuf_get_string(b, &xmss_pk, &pklen)) != 0 ||
173 (r = sshbuf_get_string(b, &xmss_sk, &sklen)) != 0)
174 goto out;
175 if (!sshkey_is_cert(key) &&
176 (r = sshkey_xmss_init(key, xmss_name)) != 0)
177 goto out;
178 if (pklen != sshkey_xmss_pklen(key) ||
179 sklen != sshkey_xmss_sklen(key)) {
180 r = SSH_ERR_INVALID_FORMAT;
181 goto out;
182 }
183 key->xmss_pk = xmss_pk;
184 key->xmss_sk = xmss_sk;
185 xmss_pk = xmss_sk = NULL;
186 /* optional internal state */
187 if ((r = sshkey_xmss_deserialize_state_opt(key, b)) != 0)
188 goto out;
189 /* success */
190 r = 0;
191 out:
192 free(xmss_name);
193 freezero(xmss_pk, pklen);
194 freezero(xmss_sk, sklen);
195 return r;
196 }
197
198 static int
ssh_xmss_sign(struct sshkey * key,u_char ** sigp,size_t * lenp,const u_char * data,size_t datalen,const char * alg,const char * sk_provider,const char * sk_pin,u_int compat)199 ssh_xmss_sign(struct sshkey *key,
200 u_char **sigp, size_t *lenp,
201 const u_char *data, size_t datalen,
202 const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)
203 {
204 u_char *sig = NULL;
205 size_t slen = 0, len = 0, required_siglen;
206 unsigned long long smlen;
207 int r, ret;
208 struct sshbuf *b = NULL;
209
210 if (lenp != NULL)
211 *lenp = 0;
212 if (sigp != NULL)
213 *sigp = NULL;
214
215 if (key == NULL ||
216 sshkey_type_plain(key->type) != KEY_XMSS ||
217 key->xmss_sk == NULL ||
218 sshkey_xmss_params(key) == NULL)
219 return SSH_ERR_INVALID_ARGUMENT;
220 if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
221 return r;
222 if (datalen >= INT_MAX - required_siglen)
223 return SSH_ERR_INVALID_ARGUMENT;
224 smlen = slen = datalen + required_siglen;
225 if ((sig = malloc(slen)) == NULL)
226 return SSH_ERR_ALLOC_FAIL;
227 if ((r = sshkey_xmss_get_state(key, 1)) != 0)
228 goto out;
229 if ((ret = xmss_sign(key->xmss_sk, sshkey_xmss_bds_state(key), sig, &smlen,
230 data, datalen, sshkey_xmss_params(key))) != 0 || smlen <= datalen) {
231 r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */
232 goto out;
233 }
234 /* encode signature */
235 if ((b = sshbuf_new()) == NULL) {
236 r = SSH_ERR_ALLOC_FAIL;
237 goto out;
238 }
239 if ((r = sshbuf_put_cstring(b, "ssh-xmss@openssh.com")) != 0 ||
240 (r = sshbuf_put_string(b, sig, smlen - datalen)) != 0)
241 goto out;
242 len = sshbuf_len(b);
243 if (sigp != NULL) {
244 if ((*sigp = malloc(len)) == NULL) {
245 r = SSH_ERR_ALLOC_FAIL;
246 goto out;
247 }
248 memcpy(*sigp, sshbuf_ptr(b), len);
249 }
250 if (lenp != NULL)
251 *lenp = len;
252 /* success */
253 r = 0;
254 out:
255 if ((ret = sshkey_xmss_update_state(key, 1)) != 0) {
256 /* discard signature since we cannot update the state */
257 if (r == 0 && sigp != NULL && *sigp != NULL) {
258 explicit_bzero(*sigp, len);
259 free(*sigp);
260 }
261 if (sigp != NULL)
262 *sigp = NULL;
263 if (lenp != NULL)
264 *lenp = 0;
265 r = ret;
266 }
267 sshbuf_free(b);
268 if (sig != NULL)
269 freezero(sig, slen);
270
271 return r;
272 }
273
274 static int
ssh_xmss_verify(const struct sshkey * key,const u_char * sig,size_t siglen,const u_char * data,size_t dlen,const char * alg,u_int compat,struct sshkey_sig_details ** detailsp)275 ssh_xmss_verify(const struct sshkey *key,
276 const u_char *sig, size_t siglen,
277 const u_char *data, size_t dlen, const char *alg, u_int compat,
278 struct sshkey_sig_details **detailsp)
279 {
280 struct sshbuf *b = NULL;
281 char *ktype = NULL;
282 const u_char *sigblob;
283 u_char *sm = NULL, *m = NULL;
284 size_t len, required_siglen;
285 unsigned long long smlen = 0, mlen = 0;
286 int r, ret;
287
288 if (key == NULL ||
289 sshkey_type_plain(key->type) != KEY_XMSS ||
290 key->xmss_pk == NULL ||
291 sshkey_xmss_params(key) == NULL ||
292 sig == NULL || siglen == 0)
293 return SSH_ERR_INVALID_ARGUMENT;
294 if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
295 return r;
296 if (dlen >= INT_MAX - required_siglen)
297 return SSH_ERR_INVALID_ARGUMENT;
298
299 if ((b = sshbuf_from(sig, siglen)) == NULL)
300 return SSH_ERR_ALLOC_FAIL;
301 if ((r = sshbuf_get_cstring(b, &ktype, NULL)) != 0 ||
302 (r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)
303 goto out;
304 if (strcmp("ssh-xmss@openssh.com", ktype) != 0) {
305 r = SSH_ERR_KEY_TYPE_MISMATCH;
306 goto out;
307 }
308 if (sshbuf_len(b) != 0) {
309 r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
310 goto out;
311 }
312 if (len != required_siglen) {
313 r = SSH_ERR_INVALID_FORMAT;
314 goto out;
315 }
316 if (dlen >= SIZE_MAX - len) {
317 r = SSH_ERR_INVALID_ARGUMENT;
318 goto out;
319 }
320 smlen = len + dlen;
321 mlen = smlen;
322 if ((sm = malloc(smlen)) == NULL || (m = malloc(mlen)) == NULL) {
323 r = SSH_ERR_ALLOC_FAIL;
324 goto out;
325 }
326 memcpy(sm, sigblob, len);
327 memcpy(sm+len, data, dlen);
328 if ((ret = xmss_sign_open(m, &mlen, sm, smlen,
329 key->xmss_pk, sshkey_xmss_params(key))) != 0) {
330 debug2_f("xmss_sign_open failed: %d", ret);
331 }
332 if (ret != 0 || mlen != dlen) {
333 r = SSH_ERR_SIGNATURE_INVALID;
334 goto out;
335 }
336 /* XXX compare 'm' and 'data' ? */
337 /* success */
338 r = 0;
339 out:
340 if (sm != NULL)
341 freezero(sm, smlen);
342 if (m != NULL)
343 freezero(m, smlen);
344 sshbuf_free(b);
345 free(ktype);
346 return r;
347 }
348
349 static const struct sshkey_impl_funcs sshkey_xmss_funcs = {
350 /* .size = */ NULL,
351 /* .alloc = */ NULL,
352 /* .cleanup = */ ssh_xmss_cleanup,
353 /* .equal = */ ssh_xmss_equal,
354 /* .ssh_serialize_public = */ ssh_xmss_serialize_public,
355 /* .ssh_deserialize_public = */ ssh_xmss_deserialize_public,
356 /* .ssh_serialize_private = */ ssh_xmss_serialize_private,
357 /* .ssh_deserialize_private = */ ssh_xmss_deserialize_private,
358 /* .generate = */ sshkey_xmss_generate_private_key,
359 /* .copy_public = */ ssh_xmss_copy_public,
360 /* .sign = */ ssh_xmss_sign,
361 /* .verify = */ ssh_xmss_verify,
362 };
363
364 const struct sshkey_impl sshkey_xmss_impl = {
365 /* .name = */ "ssh-xmss@openssh.com",
366 /* .shortname = */ "XMSS",
367 /* .sigalg = */ NULL,
368 /* .type = */ KEY_XMSS,
369 /* .nid = */ 0,
370 /* .cert = */ 0,
371 /* .sigonly = */ 0,
372 /* .keybits = */ 256,
373 /* .funcs = */ &sshkey_xmss_funcs,
374 };
375
376 const struct sshkey_impl sshkey_xmss_cert_impl = {
377 /* .name = */ "ssh-xmss-cert-v01@openssh.com",
378 /* .shortname = */ "XMSS-CERT",
379 /* .sigalg = */ NULL,
380 /* .type = */ KEY_XMSS_CERT,
381 /* .nid = */ 0,
382 /* .cert = */ 1,
383 /* .sigonly = */ 0,
384 /* .keybits = */ 256,
385 /* .funcs = */ &sshkey_xmss_funcs,
386 };
387