1/* $OpenBSD: ssh-ed25519.c,v 1.19 2022/10/28 00:44:44 djm 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 "includes.h"
19
20#include <sys/types.h>
21#include <limits.h>
22
23#include "crypto_api.h"
24
25#include <string.h>
26#include <stdarg.h>
27
28#include "log.h"
29#include "sshbuf.h"
30#define SSHKEY_INTERNAL
31#include "sshkey.h"
32#include "ssherr.h"
33#include "ssh.h"
34
35static void
36ssh_ed25519_cleanup(struct sshkey *k)
37{
38	freezero(k->ed25519_pk, ED25519_PK_SZ);
39	freezero(k->ed25519_sk, ED25519_SK_SZ);
40	k->ed25519_pk = NULL;
41	k->ed25519_sk = NULL;
42}
43
44static int
45ssh_ed25519_equal(const struct sshkey *a, const struct sshkey *b)
46{
47	if (a->ed25519_pk == NULL || b->ed25519_pk == NULL)
48		return 0;
49	if (memcmp(a->ed25519_pk, b->ed25519_pk, ED25519_PK_SZ) != 0)
50		return 0;
51	return 1;
52}
53
54static int
55ssh_ed25519_serialize_public(const struct sshkey *key, struct sshbuf *b,
56    enum sshkey_serialize_rep opts)
57{
58	int r;
59
60	if (key->ed25519_pk == NULL)
61		return SSH_ERR_INVALID_ARGUMENT;
62	if ((r = sshbuf_put_string(b, key->ed25519_pk, ED25519_PK_SZ)) != 0)
63		return r;
64
65	return 0;
66}
67
68static int
69ssh_ed25519_serialize_private(const struct sshkey *key, struct sshbuf *b,
70    enum sshkey_serialize_rep opts)
71{
72	int r;
73
74	if ((r = sshbuf_put_string(b, key->ed25519_pk, ED25519_PK_SZ)) != 0 ||
75	    (r = sshbuf_put_string(b, key->ed25519_sk, ED25519_SK_SZ)) != 0)
76		return r;
77
78	return 0;
79}
80
81static int
82ssh_ed25519_generate(struct sshkey *k, int bits)
83{
84	if ((k->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL ||
85	    (k->ed25519_sk = malloc(ED25519_SK_SZ)) == NULL)
86		return SSH_ERR_ALLOC_FAIL;
87	crypto_sign_ed25519_keypair(k->ed25519_pk, k->ed25519_sk);
88	return 0;
89}
90
91static int
92ssh_ed25519_copy_public(const struct sshkey *from, struct sshkey *to)
93{
94	if (from->ed25519_pk == NULL)
95		return 0; /* XXX SSH_ERR_INTERNAL_ERROR ? */
96	if ((to->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL)
97		return SSH_ERR_ALLOC_FAIL;
98	memcpy(to->ed25519_pk, from->ed25519_pk, ED25519_PK_SZ);
99	return 0;
100}
101
102static int
103ssh_ed25519_deserialize_public(const char *ktype, struct sshbuf *b,
104    struct sshkey *key)
105{
106	u_char *pk = NULL;
107	size_t len = 0;
108	int r;
109
110	if ((r = sshbuf_get_string(b, &pk, &len)) != 0)
111		return r;
112	if (len != ED25519_PK_SZ) {
113		freezero(pk, len);
114		return SSH_ERR_INVALID_FORMAT;
115	}
116	key->ed25519_pk = pk;
117	return 0;
118}
119
120static int
121ssh_ed25519_deserialize_private(const char *ktype, struct sshbuf *b,
122    struct sshkey *key)
123{
124	int r;
125	size_t sklen = 0;
126	u_char *ed25519_sk = NULL;
127
128	if ((r = ssh_ed25519_deserialize_public(NULL, b, key)) != 0)
129		goto out;
130	if ((r = sshbuf_get_string(b, &ed25519_sk, &sklen)) != 0)
131		goto out;
132	if (sklen != ED25519_SK_SZ) {
133		r = SSH_ERR_INVALID_FORMAT;
134		goto out;
135	}
136	key->ed25519_sk = ed25519_sk;
137	ed25519_sk = NULL; /* transferred */
138	/* success */
139	r = 0;
140 out:
141	freezero(ed25519_sk, sklen);
142	return r;
143}
144
145static int
146ssh_ed25519_sign(struct sshkey *key,
147    u_char **sigp, size_t *lenp,
148    const u_char *data, size_t datalen,
149    const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)
150{
151	u_char *sig = NULL;
152	size_t slen = 0, len;
153	unsigned long long smlen;
154	int r, ret;
155	struct sshbuf *b = NULL;
156
157	if (lenp != NULL)
158		*lenp = 0;
159	if (sigp != NULL)
160		*sigp = NULL;
161
162	if (key == NULL ||
163	    sshkey_type_plain(key->type) != KEY_ED25519 ||
164	    key->ed25519_sk == NULL ||
165	    datalen >= INT_MAX - crypto_sign_ed25519_BYTES)
166		return SSH_ERR_INVALID_ARGUMENT;
167	smlen = slen = datalen + crypto_sign_ed25519_BYTES;
168	if ((sig = malloc(slen)) == NULL)
169		return SSH_ERR_ALLOC_FAIL;
170
171	if ((ret = crypto_sign_ed25519(sig, &smlen, data, datalen,
172	    key->ed25519_sk)) != 0 || smlen <= datalen) {
173		r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */
174		goto out;
175	}
176	/* encode signature */
177	if ((b = sshbuf_new()) == NULL) {
178		r = SSH_ERR_ALLOC_FAIL;
179		goto out;
180	}
181	if ((r = sshbuf_put_cstring(b, "ssh-ed25519")) != 0 ||
182	    (r = sshbuf_put_string(b, sig, smlen - datalen)) != 0)
183		goto out;
184	len = sshbuf_len(b);
185	if (sigp != NULL) {
186		if ((*sigp = malloc(len)) == NULL) {
187			r = SSH_ERR_ALLOC_FAIL;
188			goto out;
189		}
190		memcpy(*sigp, sshbuf_ptr(b), len);
191	}
192	if (lenp != NULL)
193		*lenp = len;
194	/* success */
195	r = 0;
196 out:
197	sshbuf_free(b);
198	if (sig != NULL)
199		freezero(sig, slen);
200
201	return r;
202}
203
204static int
205ssh_ed25519_verify(const struct sshkey *key,
206    const u_char *sig, size_t siglen,
207    const u_char *data, size_t dlen, const char *alg, u_int compat,
208    struct sshkey_sig_details **detailsp)
209{
210	struct sshbuf *b = NULL;
211	char *ktype = NULL;
212	const u_char *sigblob;
213	u_char *sm = NULL, *m = NULL;
214	size_t len;
215	unsigned long long smlen = 0, mlen = 0;
216	int r, ret;
217
218	if (key == NULL ||
219	    sshkey_type_plain(key->type) != KEY_ED25519 ||
220	    key->ed25519_pk == NULL ||
221	    dlen >= INT_MAX - crypto_sign_ed25519_BYTES ||
222	    sig == NULL || siglen == 0)
223		return SSH_ERR_INVALID_ARGUMENT;
224
225	if ((b = sshbuf_from(sig, siglen)) == NULL)
226		return SSH_ERR_ALLOC_FAIL;
227	if ((r = sshbuf_get_cstring(b, &ktype, NULL)) != 0 ||
228	    (r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)
229		goto out;
230	if (strcmp("ssh-ed25519", ktype) != 0) {
231		r = SSH_ERR_KEY_TYPE_MISMATCH;
232		goto out;
233	}
234	if (sshbuf_len(b) != 0) {
235		r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
236		goto out;
237	}
238	if (len > crypto_sign_ed25519_BYTES) {
239		r = SSH_ERR_INVALID_FORMAT;
240		goto out;
241	}
242	if (dlen >= SIZE_MAX - len) {
243		r = SSH_ERR_INVALID_ARGUMENT;
244		goto out;
245	}
246	smlen = len + dlen;
247	mlen = smlen;
248	if ((sm = malloc(smlen)) == NULL || (m = malloc(mlen)) == NULL) {
249		r = SSH_ERR_ALLOC_FAIL;
250		goto out;
251	}
252	memcpy(sm, sigblob, len);
253	memcpy(sm+len, data, dlen);
254	if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
255	    key->ed25519_pk)) != 0) {
256		debug2_f("crypto_sign_ed25519_open failed: %d", ret);
257	}
258	if (ret != 0 || mlen != dlen) {
259		r = SSH_ERR_SIGNATURE_INVALID;
260		goto out;
261	}
262	/* XXX compare 'm' and 'data' ? */
263	/* success */
264	r = 0;
265 out:
266	if (sm != NULL)
267		freezero(sm, smlen);
268	if (m != NULL)
269		freezero(m, smlen); /* NB mlen may be invalid if r != 0 */
270	sshbuf_free(b);
271	free(ktype);
272	return r;
273}
274
275/* NB. not static; used by ED25519-SK */
276const struct sshkey_impl_funcs sshkey_ed25519_funcs = {
277	/* .size = */		NULL,
278	/* .alloc = */		NULL,
279	/* .cleanup = */	ssh_ed25519_cleanup,
280	/* .equal = */		ssh_ed25519_equal,
281	/* .ssh_serialize_public = */ ssh_ed25519_serialize_public,
282	/* .ssh_deserialize_public = */ ssh_ed25519_deserialize_public,
283	/* .ssh_serialize_private = */ ssh_ed25519_serialize_private,
284	/* .ssh_deserialize_private = */ ssh_ed25519_deserialize_private,
285	/* .generate = */	ssh_ed25519_generate,
286	/* .copy_public = */	ssh_ed25519_copy_public,
287	/* .sign = */		ssh_ed25519_sign,
288	/* .verify = */		ssh_ed25519_verify,
289};
290
291const struct sshkey_impl sshkey_ed25519_impl = {
292	/* .name = */		"ssh-ed25519",
293	/* .shortname = */	"ED25519",
294	/* .sigalg = */		NULL,
295	/* .type = */		KEY_ED25519,
296	/* .nid = */		0,
297	/* .cert = */		0,
298	/* .sigonly = */	0,
299	/* .keybits = */	256,
300	/* .funcs = */		&sshkey_ed25519_funcs,
301};
302
303const struct sshkey_impl sshkey_ed25519_cert_impl = {
304	/* .name = */		"ssh-ed25519-cert-v01@openssh.com",
305	/* .shortname = */	"ED25519-CERT",
306	/* .sigalg = */		NULL,
307	/* .type = */		KEY_ED25519_CERT,
308	/* .nid = */		0,
309	/* .cert = */		1,
310	/* .sigonly = */	0,
311	/* .keybits = */	256,
312	/* .funcs = */		&sshkey_ed25519_funcs,
313};
314