1 /* $OpenBSD: ssh-ed25519-sk.c,v 1.15 2022/10/28 00:44:44 djm Exp $ */
2 /*
3 * Copyright (c) 2019 Markus Friedl. All rights reserved.
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 /* #define DEBUG_SK 1 */
19
20 #define SSHKEY_INTERNAL
21 #include <sys/types.h>
22 #include <limits.h>
23
24 #include "crypto_api.h"
25
26 #include <string.h>
27 #include <stdarg.h>
28
29 #include "log.h"
30 #include "sshbuf.h"
31 #include "sshkey.h"
32 #include "ssherr.h"
33 #include "ssh.h"
34 #include "digest.h"
35
36 /* Reuse some ED25519 internals */
37 extern struct sshkey_impl_funcs sshkey_ed25519_funcs;
38
39 static void
ssh_ed25519_sk_cleanup(struct sshkey * k)40 ssh_ed25519_sk_cleanup(struct sshkey *k)
41 {
42 sshkey_sk_cleanup(k);
43 sshkey_ed25519_funcs.cleanup(k);
44 }
45
46 static int
ssh_ed25519_sk_equal(const struct sshkey * a,const struct sshkey * b)47 ssh_ed25519_sk_equal(const struct sshkey *a, const struct sshkey *b)
48 {
49 if (!sshkey_sk_fields_equal(a, b))
50 return 0;
51 if (!sshkey_ed25519_funcs.equal(a, b))
52 return 0;
53 return 1;
54 }
55
56 static int
ssh_ed25519_sk_serialize_public(const struct sshkey * key,struct sshbuf * b,enum sshkey_serialize_rep opts)57 ssh_ed25519_sk_serialize_public(const struct sshkey *key, struct sshbuf *b,
58 enum sshkey_serialize_rep opts)
59 {
60 int r;
61
62 if ((r = sshkey_ed25519_funcs.serialize_public(key, b, opts)) != 0)
63 return r;
64 if ((r = sshkey_serialize_sk(key, b)) != 0)
65 return r;
66
67 return 0;
68 }
69
70 static int
ssh_ed25519_sk_serialize_private(const struct sshkey * key,struct sshbuf * b,enum sshkey_serialize_rep opts)71 ssh_ed25519_sk_serialize_private(const struct sshkey *key, struct sshbuf *b,
72 enum sshkey_serialize_rep opts)
73 {
74 int r;
75
76 if ((r = sshkey_ed25519_funcs.serialize_public(key, b, opts)) != 0)
77 return r;
78 if ((r = sshkey_serialize_private_sk(key, b)) != 0)
79 return r;
80
81 return 0;
82 }
83
84 static int
ssh_ed25519_sk_copy_public(const struct sshkey * from,struct sshkey * to)85 ssh_ed25519_sk_copy_public(const struct sshkey *from, struct sshkey *to)
86 {
87 int r;
88
89 if ((r = sshkey_ed25519_funcs.copy_public(from, to)) != 0)
90 return r;
91 if ((r = sshkey_copy_public_sk(from, to)) != 0)
92 return r;
93 return 0;
94 }
95
96 static int
ssh_ed25519_sk_deserialize_public(const char * ktype,struct sshbuf * b,struct sshkey * key)97 ssh_ed25519_sk_deserialize_public(const char *ktype, struct sshbuf *b,
98 struct sshkey *key)
99 {
100 int r;
101
102 if ((r = sshkey_ed25519_funcs.deserialize_public(ktype, b, key)) != 0)
103 return r;
104 if ((r = sshkey_deserialize_sk(b, key)) != 0)
105 return r;
106 return 0;
107 }
108
109 static int
ssh_ed25519_sk_deserialize_private(const char * ktype,struct sshbuf * b,struct sshkey * key)110 ssh_ed25519_sk_deserialize_private(const char *ktype, struct sshbuf *b,
111 struct sshkey *key)
112 {
113 int r;
114
115 if ((r = sshkey_ed25519_funcs.deserialize_public(ktype, b, key)) != 0)
116 return r;
117 if ((r = sshkey_private_deserialize_sk(b, key)) != 0)
118 return r;
119 return 0;
120 }
121
122 static int
ssh_ed25519_sk_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)123 ssh_ed25519_sk_verify(const struct sshkey *key,
124 const u_char *sig, size_t siglen,
125 const u_char *data, size_t dlen, const char *alg, u_int compat,
126 struct sshkey_sig_details **detailsp)
127 {
128 struct sshbuf *b = NULL;
129 struct sshbuf *encoded = NULL;
130 char *ktype = NULL;
131 const u_char *sigblob;
132 const u_char *sm;
133 u_char *m = NULL;
134 u_char apphash[32];
135 u_char msghash[32];
136 u_char sig_flags;
137 u_int sig_counter;
138 size_t len;
139 unsigned long long smlen = 0, mlen = 0;
140 int r = SSH_ERR_INTERNAL_ERROR;
141 int ret;
142 struct sshkey_sig_details *details = NULL;
143
144 if (detailsp != NULL)
145 *detailsp = NULL;
146
147 if (key == NULL ||
148 sshkey_type_plain(key->type) != KEY_ED25519_SK ||
149 key->ed25519_pk == NULL ||
150 sig == NULL || siglen == 0)
151 return SSH_ERR_INVALID_ARGUMENT;
152
153 if ((b = sshbuf_from(sig, siglen)) == NULL)
154 return SSH_ERR_ALLOC_FAIL;
155 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
156 sshbuf_get_string_direct(b, &sigblob, &len) != 0 ||
157 sshbuf_get_u8(b, &sig_flags) != 0 ||
158 sshbuf_get_u32(b, &sig_counter) != 0) {
159 r = SSH_ERR_INVALID_FORMAT;
160 goto out;
161 }
162 #ifdef DEBUG_SK
163 fprintf(stderr, "%s: data:\n", __func__);
164 /* sshbuf_dump_data(data, datalen, stderr); */
165 fprintf(stderr, "%s: sigblob:\n", __func__);
166 sshbuf_dump_data(sigblob, len, stderr);
167 fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
168 __func__, sig_flags, sig_counter);
169 #endif
170 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
171 r = SSH_ERR_KEY_TYPE_MISMATCH;
172 goto out;
173 }
174 if (sshbuf_len(b) != 0) {
175 r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
176 goto out;
177 }
178 if (len > crypto_sign_ed25519_BYTES) {
179 r = SSH_ERR_INVALID_FORMAT;
180 goto out;
181 }
182 if (ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application,
183 strlen(key->sk_application), apphash, sizeof(apphash)) != 0 ||
184 ssh_digest_memory(SSH_DIGEST_SHA256, data, dlen,
185 msghash, sizeof(msghash)) != 0) {
186 r = SSH_ERR_INVALID_ARGUMENT;
187 goto out;
188 }
189 #ifdef DEBUG_SK
190 fprintf(stderr, "%s: hashed application:\n", __func__);
191 sshbuf_dump_data(apphash, sizeof(apphash), stderr);
192 fprintf(stderr, "%s: hashed message:\n", __func__);
193 sshbuf_dump_data(msghash, sizeof(msghash), stderr);
194 #endif
195 if ((details = calloc(1, sizeof(*details))) == NULL) {
196 r = SSH_ERR_ALLOC_FAIL;
197 goto out;
198 }
199 details->sk_counter = sig_counter;
200 details->sk_flags = sig_flags;
201 if ((encoded = sshbuf_new()) == NULL) {
202 r = SSH_ERR_ALLOC_FAIL;
203 goto out;
204 }
205 if (sshbuf_put(encoded, sigblob, len) != 0 ||
206 sshbuf_put(encoded, apphash, sizeof(apphash)) != 0 ||
207 sshbuf_put_u8(encoded, sig_flags) != 0 ||
208 sshbuf_put_u32(encoded, sig_counter) != 0 ||
209 sshbuf_put(encoded, msghash, sizeof(msghash)) != 0) {
210 r = SSH_ERR_ALLOC_FAIL;
211 goto out;
212 }
213 #ifdef DEBUG_SK
214 fprintf(stderr, "%s: signed buf:\n", __func__);
215 sshbuf_dump(encoded, stderr);
216 #endif
217 sm = sshbuf_ptr(encoded);
218 smlen = sshbuf_len(encoded);
219 mlen = smlen;
220 if ((m = malloc(smlen)) == NULL) {
221 r = SSH_ERR_ALLOC_FAIL;
222 goto out;
223 }
224 if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
225 key->ed25519_pk)) != 0) {
226 debug2_f("crypto_sign_ed25519_open failed: %d", ret);
227 }
228 if (ret != 0 || mlen != smlen - len) {
229 r = SSH_ERR_SIGNATURE_INVALID;
230 goto out;
231 }
232 /* XXX compare 'm' and 'sm + len' ? */
233 /* success */
234 r = 0;
235 if (detailsp != NULL) {
236 *detailsp = details;
237 details = NULL;
238 }
239 out:
240 if (m != NULL)
241 freezero(m, smlen); /* NB mlen may be invalid if r != 0 */
242 sshkey_sig_details_free(details);
243 sshbuf_free(b);
244 sshbuf_free(encoded);
245 free(ktype);
246 return r;
247 }
248
249 static const struct sshkey_impl_funcs sshkey_ed25519_sk_funcs = {
250 /* .size = */ NULL,
251 /* .alloc = */ NULL,
252 /* .cleanup = */ ssh_ed25519_sk_cleanup,
253 /* .equal = */ ssh_ed25519_sk_equal,
254 /* .ssh_serialize_public = */ ssh_ed25519_sk_serialize_public,
255 /* .ssh_deserialize_public = */ ssh_ed25519_sk_deserialize_public,
256 /* .ssh_serialize_private = */ ssh_ed25519_sk_serialize_private,
257 /* .ssh_deserialize_private = */ ssh_ed25519_sk_deserialize_private,
258 /* .generate = */ NULL,
259 /* .copy_public = */ ssh_ed25519_sk_copy_public,
260 /* .sign = */ NULL,
261 /* .verify = */ ssh_ed25519_sk_verify,
262 };
263
264 const struct sshkey_impl sshkey_ed25519_sk_impl = {
265 /* .name = */ "sk-ssh-ed25519@openssh.com",
266 /* .shortname = */ "ED25519-SK",
267 /* .sigalg = */ NULL,
268 /* .type = */ KEY_ED25519_SK,
269 /* .nid = */ 0,
270 /* .cert = */ 0,
271 /* .sigonly = */ 0,
272 /* .keybits = */ 256,
273 /* .funcs = */ &sshkey_ed25519_sk_funcs,
274 };
275
276 const struct sshkey_impl sshkey_ed25519_sk_cert_impl = {
277 /* .name = */ "sk-ssh-ed25519-cert-v01@openssh.com",
278 /* .shortname = */ "ED25519-SK-CERT",
279 /* .sigalg = */ NULL,
280 /* .type = */ KEY_ED25519_SK_CERT,
281 /* .nid = */ 0,
282 /* .cert = */ 1,
283 /* .sigonly = */ 0,
284 /* .keybits = */ 256,
285 /* .funcs = */ &sshkey_ed25519_sk_funcs,
286 };
287