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-rw-r--r--kexgen.c322
1 files changed, 322 insertions, 0 deletions
diff --git a/kexgen.c b/kexgen.c
new file mode 100644
index 000000000..3983c9f6b
--- /dev/null
+++ b/kexgen.c
@@ -0,0 +1,322 @@
1/* $OpenBSD: kexgen.c,v 1.1 2019/01/21 11:22:00 djm Exp $ */
2/*
3 * Copyright (c) 2019 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include <sys/types.h>
27
28#include <stdio.h>
29#include <string.h>
30#include <signal.h>
31
32#include "sshkey.h"
33#include "kex.h"
34#include "log.h"
35#include "packet.h"
36#include "ssh2.h"
37#include "sshbuf.h"
38#include "digest.h"
39#include "ssherr.h"
40
41static int input_kex_gen_init(int, u_int32_t, struct ssh *);
42static int input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh);
43
44static int
45kex_gen_hash(
46 int hash_alg,
47 const struct sshbuf *client_version,
48 const struct sshbuf *server_version,
49 const u_char *ckexinit, size_t ckexinitlen,
50 const u_char *skexinit, size_t skexinitlen,
51 const u_char *serverhostkeyblob, size_t sbloblen,
52 const struct sshbuf *client_pub,
53 const struct sshbuf *server_pub,
54 const struct sshbuf *shared_secret,
55 u_char *hash, size_t *hashlen)
56{
57 struct sshbuf *b;
58 int r;
59
60 if (*hashlen < ssh_digest_bytes(hash_alg))
61 return SSH_ERR_INVALID_ARGUMENT;
62 if ((b = sshbuf_new()) == NULL)
63 return SSH_ERR_ALLOC_FAIL;
64 if ((r = sshbuf_put_stringb(b, client_version)) != 0 ||
65 (r = sshbuf_put_stringb(b, server_version)) != 0 ||
66 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
67 (r = sshbuf_put_u32(b, ckexinitlen+1)) != 0 ||
68 (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
69 (r = sshbuf_put(b, ckexinit, ckexinitlen)) != 0 ||
70 (r = sshbuf_put_u32(b, skexinitlen+1)) != 0 ||
71 (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
72 (r = sshbuf_put(b, skexinit, skexinitlen)) != 0 ||
73 (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) != 0 ||
74 (r = sshbuf_put_stringb(b, client_pub)) != 0 ||
75 (r = sshbuf_put_stringb(b, server_pub)) != 0 ||
76 (r = sshbuf_putb(b, shared_secret)) != 0) {
77 sshbuf_free(b);
78 return r;
79 }
80#ifdef DEBUG_KEX
81 sshbuf_dump(b, stderr);
82#endif
83 if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
84 sshbuf_free(b);
85 return SSH_ERR_LIBCRYPTO_ERROR;
86 }
87 sshbuf_free(b);
88 *hashlen = ssh_digest_bytes(hash_alg);
89#ifdef DEBUG_KEX
90 dump_digest("hash", hash, *hashlen);
91#endif
92 return 0;
93}
94
95int
96kex_gen_client(struct ssh *ssh)
97{
98 struct kex *kex = ssh->kex;
99 int r;
100
101 switch (kex->kex_type) {
102 case KEX_DH_GRP1_SHA1:
103 case KEX_DH_GRP14_SHA1:
104 case KEX_DH_GRP14_SHA256:
105 case KEX_DH_GRP16_SHA512:
106 case KEX_DH_GRP18_SHA512:
107 r = kex_dh_keypair(kex);
108 break;
109 case KEX_ECDH_SHA2:
110 r = kex_ecdh_keypair(kex);
111 break;
112 case KEX_C25519_SHA256:
113 r = kex_c25519_keypair(kex);
114 break;
115 case KEX_KEM_SNTRUP4591761X25519_SHA512:
116 r = kex_kem_sntrup4591761x25519_keypair(kex);
117 break;
118 default:
119 r = SSH_ERR_INVALID_ARGUMENT;
120 break;
121 }
122 if (r != 0)
123 return r;
124 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
125 (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0 ||
126 (r = sshpkt_send(ssh)) != 0)
127 return r;
128 debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
129 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_gen_reply);
130 return 0;
131}
132
133static int
134input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh)
135{
136 struct kex *kex = ssh->kex;
137 struct sshkey *server_host_key = NULL;
138 struct sshbuf *shared_secret = NULL;
139 struct sshbuf *server_blob = NULL;
140 u_char *server_host_key_blob = NULL, *signature = NULL;
141 u_char hash[SSH_DIGEST_MAX_LENGTH];
142 size_t slen, sbloblen, hashlen;
143 int r;
144
145 /* hostkey */
146 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
147 &sbloblen)) != 0 ||
148 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
149 &server_host_key)) != 0)
150 goto out;
151 if ((r = kex_verify_host_key(ssh, server_host_key)) != 0)
152 goto out;
153
154 /* Q_S, server public key */
155 /* signed H */
156 if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
157 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
158 (r = sshpkt_get_end(ssh)) != 0)
159 goto out;
160
161 /* compute shared secret */
162 switch (kex->kex_type) {
163 case KEX_DH_GRP1_SHA1:
164 case KEX_DH_GRP14_SHA1:
165 case KEX_DH_GRP14_SHA256:
166 case KEX_DH_GRP16_SHA512:
167 case KEX_DH_GRP18_SHA512:
168 r = kex_dh_dec(kex, server_blob, &shared_secret);
169 break;
170 case KEX_ECDH_SHA2:
171 r = kex_ecdh_dec(kex, server_blob, &shared_secret);
172 break;
173 case KEX_C25519_SHA256:
174 r = kex_c25519_dec(kex, server_blob, &shared_secret);
175 break;
176 case KEX_KEM_SNTRUP4591761X25519_SHA512:
177 r = kex_kem_sntrup4591761x25519_dec(kex, server_blob,
178 &shared_secret);
179 break;
180 default:
181 r = SSH_ERR_INVALID_ARGUMENT;
182 break;
183 }
184 if (r !=0 )
185 goto out;
186
187 /* calc and verify H */
188 hashlen = sizeof(hash);
189 if ((r = kex_gen_hash(
190 kex->hash_alg,
191 kex->client_version,
192 kex->server_version,
193 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
194 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
195 server_host_key_blob, sbloblen,
196 kex->client_pub,
197 server_blob,
198 shared_secret,
199 hash, &hashlen)) != 0)
200 goto out;
201
202 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
203 kex->hostkey_alg, ssh->compat)) != 0)
204 goto out;
205
206 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
207 r = kex_send_newkeys(ssh);
208out:
209 explicit_bzero(hash, sizeof(hash));
210 explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
211 explicit_bzero(kex->sntrup4591761_client_key,
212 sizeof(kex->sntrup4591761_client_key));
213 free(server_host_key_blob);
214 free(signature);
215 sshkey_free(server_host_key);
216 sshbuf_free(server_blob);
217 sshbuf_free(shared_secret);
218 sshbuf_free(kex->client_pub);
219 kex->client_pub = NULL;
220 return r;
221}
222
223int
224kex_gen_server(struct ssh *ssh)
225{
226 debug("expecting SSH2_MSG_KEX_ECDH_INIT");
227 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_gen_init);
228 return 0;
229}
230
231static int
232input_kex_gen_init(int type, u_int32_t seq, struct ssh *ssh)
233{
234 struct kex *kex = ssh->kex;
235 struct sshkey *server_host_private, *server_host_public;
236 struct sshbuf *shared_secret = NULL;
237 struct sshbuf *server_pubkey = NULL;
238 struct sshbuf *client_pubkey = NULL;
239 u_char *server_host_key_blob = NULL, *signature = NULL;
240 u_char hash[SSH_DIGEST_MAX_LENGTH];
241 size_t slen, sbloblen, hashlen;
242 int r;
243
244 if ((r = kex_load_hostkey(ssh, &server_host_private,
245 &server_host_public)) != 0)
246 goto out;
247
248 if ((r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 ||
249 (r = sshpkt_get_end(ssh)) != 0)
250 goto out;
251
252 /* compute shared secret */
253 switch (kex->kex_type) {
254 case KEX_DH_GRP1_SHA1:
255 case KEX_DH_GRP14_SHA1:
256 case KEX_DH_GRP14_SHA256:
257 case KEX_DH_GRP16_SHA512:
258 case KEX_DH_GRP18_SHA512:
259 r = kex_dh_enc(kex, client_pubkey, &server_pubkey,
260 &shared_secret);
261 break;
262 case KEX_ECDH_SHA2:
263 r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey,
264 &shared_secret);
265 break;
266 case KEX_C25519_SHA256:
267 r = kex_c25519_enc(kex, client_pubkey, &server_pubkey,
268 &shared_secret);
269 break;
270 case KEX_KEM_SNTRUP4591761X25519_SHA512:
271 r = kex_kem_sntrup4591761x25519_enc(kex, client_pubkey,
272 &server_pubkey, &shared_secret);
273 break;
274 default:
275 r = SSH_ERR_INVALID_ARGUMENT;
276 break;
277 }
278 if (r !=0 )
279 goto out;
280
281 /* calc H */
282 if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
283 &sbloblen)) != 0)
284 goto out;
285 hashlen = sizeof(hash);
286 if ((r = kex_gen_hash(
287 kex->hash_alg,
288 kex->client_version,
289 kex->server_version,
290 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
291 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
292 server_host_key_blob, sbloblen,
293 client_pubkey,
294 server_pubkey,
295 shared_secret,
296 hash, &hashlen)) != 0)
297 goto out;
298
299 /* sign H */
300 if ((r = kex->sign(ssh, server_host_private, server_host_public,
301 &signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0)
302 goto out;
303
304 /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
305 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
306 (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
307 (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
308 (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
309 (r = sshpkt_send(ssh)) != 0)
310 goto out;
311
312 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
313 r = kex_send_newkeys(ssh);
314out:
315 explicit_bzero(hash, sizeof(hash));
316 free(server_host_key_blob);
317 free(signature);
318 sshbuf_free(shared_secret);
319 sshbuf_free(client_pubkey);
320 sshbuf_free(server_pubkey);
321 return r;
322}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 01:39:28 +0000