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1/* $OpenBSD: ssh-ed25519.c,v 1.22 2026/02/14 00:18:34 jsg Exp $ */
2/*
3 * Copyright (c) 2013 Markus Friedl <markus@openbsd.org>
4 *
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.
8 *
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.
16 */
17
18#include <sys/types.h>
19#include <limits.h>
20
21#include "crypto_api.h"
22
23#include <string.h>
24#include <stdarg.h>
25
26#include "log.h"
27#include "sshbuf.h"
28#define SSHKEY_INTERNAL
29#include "sshkey.h"
30#include "ssherr.h"
31
32static void
33ssh_ed25519_cleanup(struct sshkey *k)
34{
35 freezero(k->ed25519_pk, ED25519_PK_SZ);
36 freezero(k->ed25519_sk, ED25519_SK_SZ);
37 k->ed25519_pk = NULL;
38 k->ed25519_sk = NULL;
39}
40
41static int
42ssh_ed25519_equal(const struct sshkey *a, const struct sshkey *b)
43{
44 if (a->ed25519_pk == NULL || b->ed25519_pk == NULL)
45 return 0;
46 if (memcmp(a->ed25519_pk, b->ed25519_pk, ED25519_PK_SZ) != 0)
47 return 0;
48 return 1;
49}
50
51static int
52ssh_ed25519_serialize_public(const struct sshkey *key, struct sshbuf *b,
53 enum sshkey_serialize_rep opts)
54{
55 int r;
56
57 if (key->ed25519_pk == NULL)
58 return SSH_ERR_INVALID_ARGUMENT;
59 if ((r = sshbuf_put_string(b, key->ed25519_pk, ED25519_PK_SZ)) != 0)
60 return r;
61
62 return 0;
63}
64
65static int
66ssh_ed25519_serialize_private(const struct sshkey *key, struct sshbuf *b,
67 enum sshkey_serialize_rep opts)
68{
69 int r;
70
71 if ((r = sshbuf_put_string(b, key->ed25519_pk, ED25519_PK_SZ)) != 0 ||
72 (r = sshbuf_put_string(b, key->ed25519_sk, ED25519_SK_SZ)) != 0)
73 return r;
74
75 return 0;
76}
77
78static int
79ssh_ed25519_generate(struct sshkey *k, int bits)
80{
81 if ((k->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL ||
82 (k->ed25519_sk = malloc(ED25519_SK_SZ)) == NULL)
83 return SSH_ERR_ALLOC_FAIL;
84 crypto_sign_ed25519_keypair(k->ed25519_pk, k->ed25519_sk);
85 return 0;
86}
87
88static int
89ssh_ed25519_copy_public(const struct sshkey *from, struct sshkey *to)
90{
91 if (from->ed25519_pk == NULL)
92 return 0; /* XXX SSH_ERR_INTERNAL_ERROR ? */
93 if ((to->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL)
94 return SSH_ERR_ALLOC_FAIL;
95 memcpy(to->ed25519_pk, from->ed25519_pk, ED25519_PK_SZ);
96 return 0;
97}
98
99static int
100ssh_ed25519_deserialize_public(const char *ktype, struct sshbuf *b,
101 struct sshkey *key)
102{
103 u_char *pk = NULL;
104 size_t len = 0;
105 int r;
106
107 if ((r = sshbuf_get_string(b, &pk, &len)) != 0)
108 return r;
109 if (len != ED25519_PK_SZ) {
110 freezero(pk, len);
111 return SSH_ERR_INVALID_FORMAT;
112 }
113 key->ed25519_pk = pk;
114 return 0;
115}
116
117static int
118ssh_ed25519_deserialize_private(const char *ktype, struct sshbuf *b,
119 struct sshkey *key)
120{
121 int r;
122 size_t sklen = 0;
123 u_char *ed25519_sk = NULL;
124
125 if ((r = ssh_ed25519_deserialize_public(NULL, b, key)) != 0)
126 goto out;
127 if ((r = sshbuf_get_string(b, &ed25519_sk, &sklen)) != 0)
128 goto out;
129 if (sklen != ED25519_SK_SZ) {
130 r = SSH_ERR_INVALID_FORMAT;
131 goto out;
132 }
133 key->ed25519_sk = ed25519_sk;
134 ed25519_sk = NULL; /* transferred */
135 /* success */
136 r = 0;
137 out:
138 freezero(ed25519_sk, sklen);
139 return r;
140}
141
142static int
143ssh_ed25519_sign(struct sshkey *key,
144 u_char **sigp, size_t *lenp,
145 const u_char *data, size_t datalen,
146 const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)
147{
148 u_char *sig = NULL;
149 size_t slen = 0;
150 unsigned long long smlen;
151 int r, ret;
152
153 if (lenp != NULL)
154 *lenp = 0;
155 if (sigp != NULL)
156 *sigp = NULL;
157
158 if (key == NULL ||
159 sshkey_type_plain(key->type) != KEY_ED25519 ||
160 key->ed25519_sk == NULL ||
161 datalen >= INT_MAX - crypto_sign_ed25519_BYTES)
162 return SSH_ERR_INVALID_ARGUMENT;
163 smlen = slen = datalen + crypto_sign_ed25519_BYTES;
164 if ((sig = malloc(slen)) == NULL)
165 return SSH_ERR_ALLOC_FAIL;
166
167 if ((ret = crypto_sign_ed25519(sig, &smlen, data, datalen,
168 key->ed25519_sk)) != 0 || smlen <= datalen) {
169 r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */
170 goto out;
171 }
172 if ((r = ssh_ed25519_encode_store_sig(sig, smlen - datalen,
173 sigp, lenp)) != 0)
174 goto out;
175
176 /* success */
177 r = 0;
178 out:
179 freezero(sig, slen);
180 return r;
181}
182
183int
184ssh_ed25519_encode_store_sig(const u_char *sig, size_t slen,
185 u_char **sigp, size_t *lenp)
186{
187 struct sshbuf *b = NULL;
188 int r = -1;
189 size_t len;
190
191 if (lenp != NULL)
192 *lenp = 0;
193 if (sigp != NULL)
194 *sigp = NULL;
195
196 if (slen != crypto_sign_ed25519_BYTES)
197 return SSH_ERR_INVALID_ARGUMENT;
198
199 /* encode signature */
200 if ((b = sshbuf_new()) == NULL) {
201 r = SSH_ERR_ALLOC_FAIL;
202 goto out;
203 }
204 if ((r = sshbuf_put_cstring(b, "ssh-ed25519")) != 0 ||
205 (r = sshbuf_put_string(b, sig, slen)) != 0)
206 goto out;
207 len = sshbuf_len(b);
208 if (sigp != NULL) {
209 if ((*sigp = malloc(len)) == NULL) {
210 r = SSH_ERR_ALLOC_FAIL;
211 goto out;
212 }
213 memcpy(*sigp, sshbuf_ptr(b), len);
214 }
215 if (lenp != NULL)
216 *lenp = len;
217 /* success */
218 r = 0;
219 out:
220 sshbuf_free(b);
221 return r;
222}
223
224static int
225ssh_ed25519_verify(const struct sshkey *key,
226 const u_char *sig, size_t siglen,
227 const u_char *data, size_t dlen, const char *alg, u_int compat,
228 struct sshkey_sig_details **detailsp)
229{
230 struct sshbuf *b = NULL;
231 char *ktype = NULL;
232 const u_char *sigblob;
233 u_char *sm = NULL, *m = NULL;
234 size_t len;
235 unsigned long long smlen = 0, mlen = 0;
236 int r, ret;
237
238 if (key == NULL ||
239 sshkey_type_plain(key->type) != KEY_ED25519 ||
240 key->ed25519_pk == NULL ||
241 dlen >= INT_MAX - crypto_sign_ed25519_BYTES ||
242 sig == NULL || siglen == 0)
243 return SSH_ERR_INVALID_ARGUMENT;
244
245 if ((b = sshbuf_from(sig, siglen)) == NULL)
246 return SSH_ERR_ALLOC_FAIL;
247 if ((r = sshbuf_get_cstring(b, &ktype, NULL)) != 0 ||
248 (r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)
249 goto out;
250 if (strcmp("ssh-ed25519", ktype) != 0) {
251 r = SSH_ERR_KEY_TYPE_MISMATCH;
252 goto out;
253 }
254 if (sshbuf_len(b) != 0) {
255 r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
256 goto out;
257 }
258 if (len > crypto_sign_ed25519_BYTES) {
259 r = SSH_ERR_INVALID_FORMAT;
260 goto out;
261 }
262 if (dlen >= SIZE_MAX - len) {
263 r = SSH_ERR_INVALID_ARGUMENT;
264 goto out;
265 }
266 smlen = len + dlen;
267 mlen = smlen;
268 if ((sm = malloc(smlen)) == NULL || (m = malloc(mlen)) == NULL) {
269 r = SSH_ERR_ALLOC_FAIL;
270 goto out;
271 }
272 memcpy(sm, sigblob, len);
273 memcpy(sm+len, data, dlen);
274 if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
275 key->ed25519_pk)) != 0) {
276 debug2_f("crypto_sign_ed25519_open failed: %d", ret);
277 }
278 if (ret != 0 || mlen != dlen) {
279 r = SSH_ERR_SIGNATURE_INVALID;
280 goto out;
281 }
282 /* XXX compare 'm' and 'data' ? */
283 /* success */
284 r = 0;
285 out:
286 if (sm != NULL)
287 freezero(sm, smlen);
288 if (m != NULL)
289 freezero(m, smlen); /* NB mlen may be invalid if r != 0 */
290 sshbuf_free(b);
291 free(ktype);
292 return r;
293}
294
295/* NB. not static; used by ED25519-SK */
296const struct sshkey_impl_funcs sshkey_ed25519_funcs = {
297 /* .size = */ NULL,
298 /* .alloc = */ NULL,
299 /* .cleanup = */ ssh_ed25519_cleanup,
300 /* .equal = */ ssh_ed25519_equal,
301 /* .ssh_serialize_public = */ ssh_ed25519_serialize_public,
302 /* .ssh_deserialize_public = */ ssh_ed25519_deserialize_public,
303 /* .ssh_serialize_private = */ ssh_ed25519_serialize_private,
304 /* .ssh_deserialize_private = */ ssh_ed25519_deserialize_private,
305 /* .generate = */ ssh_ed25519_generate,
306 /* .copy_public = */ ssh_ed25519_copy_public,
307 /* .sign = */ ssh_ed25519_sign,
308 /* .verify = */ ssh_ed25519_verify,
309};
310
311const struct sshkey_impl sshkey_ed25519_impl = {
312 /* .name = */ "ssh-ed25519",
313 /* .shortname = */ "ED25519",
314 /* .sigalg = */ NULL,
315 /* .type = */ KEY_ED25519,
316 /* .nid = */ 0,
317 /* .cert = */ 0,
318 /* .sigonly = */ 0,
319 /* .keybits = */ 256,
320 /* .funcs = */ &sshkey_ed25519_funcs,
321};
322
323const struct sshkey_impl sshkey_ed25519_cert_impl = {
324 /* .name = */ "ssh-ed25519-cert-v01@openssh.com",
325 /* .shortname = */ "ED25519-CERT",
326 /* .sigalg = */ NULL,
327 /* .type = */ KEY_ED25519_CERT,
328 /* .nid = */ 0,
329 /* .cert = */ 1,
330 /* .sigonly = */ 0,
331 /* .keybits = */ 256,
332 /* .funcs = */ &sshkey_ed25519_funcs,
333};