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-rw-r--r--kexdh.c234
1 files changed, 4 insertions, 230 deletions
diff --git a/kexdh.c b/kexdh.c
index 1e91e2550..4bbb7d1db 100644
--- a/kexdh.c
+++ b/kexdh.c
@@ -23,23 +23,16 @@
23 */ 23 */
24 24
25#include "includes.h" 25#include "includes.h"
26RCSID("$OpenBSD: kexdh.c,v 1.18 2002/03/18 17:50:31 provos Exp $"); 26RCSID("$OpenBSD: kexdh.c,v 1.19 2003/02/16 17:09:57 markus Exp $");
27 27
28#include <openssl/crypto.h> 28#include <openssl/evp.h>
29#include <openssl/bn.h>
30 29
31#include "xmalloc.h"
32#include "buffer.h" 30#include "buffer.h"
33#include "bufaux.h" 31#include "bufaux.h"
34#include "key.h"
35#include "kex.h"
36#include "log.h"
37#include "packet.h"
38#include "dh.h"
39#include "ssh2.h" 32#include "ssh2.h"
40#include "monitor_wrap.h" 33#include "kex.h"
41 34
42static u_char * 35u_char *
43kex_dh_hash( 36kex_dh_hash(
44 char *client_version_string, 37 char *client_version_string,
45 char *server_version_string, 38 char *server_version_string,
@@ -86,222 +79,3 @@ kex_dh_hash(
86#endif 79#endif
87 return digest; 80 return digest;
88} 81}
89
90/* client */
91
92static void
93kexdh_client(Kex *kex)
94{
95 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
96 DH *dh;
97 Key *server_host_key;
98 u_char *server_host_key_blob = NULL, *signature = NULL;
99 u_char *kbuf, *hash;
100 u_int klen, kout, slen, sbloblen;
101
102 /* generate and send 'e', client DH public key */
103 dh = dh_new_group1();
104 dh_gen_key(dh, kex->we_need * 8);
105 packet_start(SSH2_MSG_KEXDH_INIT);
106 packet_put_bignum2(dh->pub_key);
107 packet_send();
108
109 debug("sending SSH2_MSG_KEXDH_INIT");
110#ifdef DEBUG_KEXDH
111 DHparams_print_fp(stderr, dh);
112 fprintf(stderr, "pub= ");
113 BN_print_fp(stderr, dh->pub_key);
114 fprintf(stderr, "\n");
115#endif
116
117 debug("expecting SSH2_MSG_KEXDH_REPLY");
118 packet_read_expect(SSH2_MSG_KEXDH_REPLY);
119
120 /* key, cert */
121 server_host_key_blob = packet_get_string(&sbloblen);
122 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
123 if (server_host_key == NULL)
124 fatal("cannot decode server_host_key_blob");
125 if (server_host_key->type != kex->hostkey_type)
126 fatal("type mismatch for decoded server_host_key_blob");
127 if (kex->verify_host_key == NULL)
128 fatal("cannot verify server_host_key");
129 if (kex->verify_host_key(server_host_key) == -1)
130 fatal("server_host_key verification failed");
131
132 /* DH paramter f, server public DH key */
133 if ((dh_server_pub = BN_new()) == NULL)
134 fatal("dh_server_pub == NULL");
135 packet_get_bignum2(dh_server_pub);
136
137#ifdef DEBUG_KEXDH
138 fprintf(stderr, "dh_server_pub= ");
139 BN_print_fp(stderr, dh_server_pub);
140 fprintf(stderr, "\n");
141 debug("bits %d", BN_num_bits(dh_server_pub));
142#endif
143
144 /* signed H */
145 signature = packet_get_string(&slen);
146 packet_check_eom();
147
148 if (!dh_pub_is_valid(dh, dh_server_pub))
149 packet_disconnect("bad server public DH value");
150
151 klen = DH_size(dh);
152 kbuf = xmalloc(klen);
153 kout = DH_compute_key(kbuf, dh_server_pub, dh);
154#ifdef DEBUG_KEXDH
155 dump_digest("shared secret", kbuf, kout);
156#endif
157 if ((shared_secret = BN_new()) == NULL)
158 fatal("kexdh_client: BN_new failed");
159 BN_bin2bn(kbuf, kout, shared_secret);
160 memset(kbuf, 0, klen);
161 xfree(kbuf);
162
163 /* calc and verify H */
164 hash = kex_dh_hash(
165 kex->client_version_string,
166 kex->server_version_string,
167 buffer_ptr(&kex->my), buffer_len(&kex->my),
168 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
169 server_host_key_blob, sbloblen,
170 dh->pub_key,
171 dh_server_pub,
172 shared_secret
173 );
174 xfree(server_host_key_blob);
175 BN_clear_free(dh_server_pub);
176 DH_free(dh);
177
178 if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
179 fatal("key_verify failed for server_host_key");
180 key_free(server_host_key);
181 xfree(signature);
182
183 /* save session id */
184 if (kex->session_id == NULL) {
185 kex->session_id_len = 20;
186 kex->session_id = xmalloc(kex->session_id_len);
187 memcpy(kex->session_id, hash, kex->session_id_len);
188 }
189
190 kex_derive_keys(kex, hash, shared_secret);
191 BN_clear_free(shared_secret);
192 kex_finish(kex);
193}
194
195/* server */
196
197static void
198kexdh_server(Kex *kex)
199{
200 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
201 DH *dh;
202 Key *server_host_key;
203 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
204 u_int sbloblen, klen, kout;
205 u_int slen;
206
207 /* generate server DH public key */
208 dh = dh_new_group1();
209 dh_gen_key(dh, kex->we_need * 8);
210
211 debug("expecting SSH2_MSG_KEXDH_INIT");
212 packet_read_expect(SSH2_MSG_KEXDH_INIT);
213
214 if (kex->load_host_key == NULL)
215 fatal("Cannot load hostkey");
216 server_host_key = kex->load_host_key(kex->hostkey_type);
217 if (server_host_key == NULL)
218 fatal("Unsupported hostkey type %d", kex->hostkey_type);
219
220 /* key, cert */
221 if ((dh_client_pub = BN_new()) == NULL)
222 fatal("dh_client_pub == NULL");
223 packet_get_bignum2(dh_client_pub);
224 packet_check_eom();
225
226#ifdef DEBUG_KEXDH
227 fprintf(stderr, "dh_client_pub= ");
228 BN_print_fp(stderr, dh_client_pub);
229 fprintf(stderr, "\n");
230 debug("bits %d", BN_num_bits(dh_client_pub));
231#endif
232
233#ifdef DEBUG_KEXDH
234 DHparams_print_fp(stderr, dh);
235 fprintf(stderr, "pub= ");
236 BN_print_fp(stderr, dh->pub_key);
237 fprintf(stderr, "\n");
238#endif
239 if (!dh_pub_is_valid(dh, dh_client_pub))
240 packet_disconnect("bad client public DH value");
241
242 klen = DH_size(dh);
243 kbuf = xmalloc(klen);
244 kout = DH_compute_key(kbuf, dh_client_pub, dh);
245#ifdef DEBUG_KEXDH
246 dump_digest("shared secret", kbuf, kout);
247#endif
248 if ((shared_secret = BN_new()) == NULL)
249 fatal("kexdh_server: BN_new failed");
250 BN_bin2bn(kbuf, kout, shared_secret);
251 memset(kbuf, 0, klen);
252 xfree(kbuf);
253
254 key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
255
256 /* calc H */
257 hash = kex_dh_hash(
258 kex->client_version_string,
259 kex->server_version_string,
260 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
261 buffer_ptr(&kex->my), buffer_len(&kex->my),
262 server_host_key_blob, sbloblen,
263 dh_client_pub,
264 dh->pub_key,
265 shared_secret
266 );
267 BN_clear_free(dh_client_pub);
268
269 /* save session id := H */
270 /* XXX hashlen depends on KEX */
271 if (kex->session_id == NULL) {
272 kex->session_id_len = 20;
273 kex->session_id = xmalloc(kex->session_id_len);
274 memcpy(kex->session_id, hash, kex->session_id_len);
275 }
276
277 /* sign H */
278 /* XXX hashlen depends on KEX */
279 PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
280
281 /* destroy_sensitive_data(); */
282
283 /* send server hostkey, DH pubkey 'f' and singed H */
284 packet_start(SSH2_MSG_KEXDH_REPLY);
285 packet_put_string(server_host_key_blob, sbloblen);
286 packet_put_bignum2(dh->pub_key); /* f */
287 packet_put_string(signature, slen);
288 packet_send();
289
290 xfree(signature);
291 xfree(server_host_key_blob);
292 /* have keys, free DH */
293 DH_free(dh);
294
295 kex_derive_keys(kex, hash, shared_secret);
296 BN_clear_free(shared_secret);
297 kex_finish(kex);
298}
299
300void
301kexdh(Kex *kex)
302{
303 if (kex->server)
304 kexdh_server(kex);
305 else
306 kexdh_client(kex);
307}
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