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authorSimon Wilkinson <simon@sxw.org.uk>2014-02-09 16:09:48 +0000
committerColin Watson <cjwatson@debian.org>2020-06-07 10:24:45 +0100
commit79f9d21b406c172878896ef41cdc2502fc2f84a7 (patch)
tree71507aaefd925223b1543b10f4342f2df9ea0ee3 /kexgssc.c
parent202f5a676221c244cd450086c334c2b59f339e86 (diff)
GSSAPI key exchange support
This patch has been rejected upstream: "None of the OpenSSH developers are in favour of adding this, and this situation has not changed for several years. This is not a slight on Simon's patch, which is of fine quality, but just that a) we don't trust GSSAPI implementations that much and b) we don't like adding new KEX since they are pre-auth attack surface. This one is particularly scary, since it requires hooks out to typically root-owned system resources." However, quite a lot of people rely on this in Debian, and it's better to have it merged into the main openssh package rather than having separate -krb5 packages (as we used to have). It seems to have a generally good security history. Author: Simon Wilkinson <simon@sxw.org.uk> Author: Colin Watson <cjwatson@debian.org> Author: Jakub Jelen <jjelen@redhat.com> Origin: other, https://github.com/openssh-gsskex/openssh-gsskex/commits/debian/master Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1242 Last-Updated: 2020-06-07 Patch-Name: gssapi.patch
Diffstat (limited to 'kexgssc.c')
-rw-r--r--kexgssc.c606
1 files changed, 606 insertions, 0 deletions
diff --git a/kexgssc.c b/kexgssc.c
new file mode 100644
index 000000000..f6e1405eb
--- /dev/null
+++ b/kexgssc.c
@@ -0,0 +1,606 @@
1/*
2 * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include "includes.h"
26
27#if defined(GSSAPI) && defined(WITH_OPENSSL)
28
29#include "includes.h"
30
31#include <openssl/crypto.h>
32#include <openssl/bn.h>
33
34#include <string.h>
35
36#include "xmalloc.h"
37#include "sshbuf.h"
38#include "ssh2.h"
39#include "sshkey.h"
40#include "cipher.h"
41#include "kex.h"
42#include "log.h"
43#include "packet.h"
44#include "dh.h"
45#include "digest.h"
46#include "ssherr.h"
47
48#include "ssh-gss.h"
49
50int
51kexgss_client(struct ssh *ssh)
52{
53 struct kex *kex = ssh->kex;
54 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER,
55 recv_tok = GSS_C_EMPTY_BUFFER,
56 gssbuf, msg_tok = GSS_C_EMPTY_BUFFER, *token_ptr;
57 Gssctxt *ctxt;
58 OM_uint32 maj_status, min_status, ret_flags;
59 struct sshbuf *server_blob = NULL;
60 struct sshbuf *shared_secret = NULL;
61 struct sshbuf *server_host_key_blob = NULL;
62 struct sshbuf *empty = NULL;
63 u_char *msg;
64 int type = 0;
65 int first = 1;
66 u_char hash[SSH_DIGEST_MAX_LENGTH];
67 size_t hashlen;
68 u_char c;
69 int r;
70
71 /* Initialise our GSSAPI world */
72 ssh_gssapi_build_ctx(&ctxt);
73 if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type)
74 == GSS_C_NO_OID)
75 fatal("Couldn't identify host exchange");
76
77 if (ssh_gssapi_import_name(ctxt, kex->gss_host))
78 fatal("Couldn't import hostname");
79
80 if (kex->gss_client &&
81 ssh_gssapi_client_identity(ctxt, kex->gss_client))
82 fatal("Couldn't acquire client credentials");
83
84 /* Step 1 */
85 switch (kex->kex_type) {
86 case KEX_GSS_GRP1_SHA1:
87 case KEX_GSS_GRP14_SHA1:
88 case KEX_GSS_GRP14_SHA256:
89 case KEX_GSS_GRP16_SHA512:
90 r = kex_dh_keypair(kex);
91 break;
92 case KEX_GSS_NISTP256_SHA256:
93 r = kex_ecdh_keypair(kex);
94 break;
95 case KEX_GSS_C25519_SHA256:
96 r = kex_c25519_keypair(kex);
97 break;
98 default:
99 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
100 }
101 if (r != 0)
102 return r;
103
104 token_ptr = GSS_C_NO_BUFFER;
105
106 do {
107 debug("Calling gss_init_sec_context");
108
109 maj_status = ssh_gssapi_init_ctx(ctxt,
110 kex->gss_deleg_creds, token_ptr, &send_tok,
111 &ret_flags);
112
113 if (GSS_ERROR(maj_status)) {
114 /* XXX Useles code: Missing send? */
115 if (send_tok.length != 0) {
116 if ((r = sshpkt_start(ssh,
117 SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
118 (r = sshpkt_put_string(ssh, send_tok.value,
119 send_tok.length)) != 0)
120 fatal("sshpkt failed: %s", ssh_err(r));
121 }
122 fatal("gss_init_context failed");
123 }
124
125 /* If we've got an old receive buffer get rid of it */
126 if (token_ptr != GSS_C_NO_BUFFER)
127 gss_release_buffer(&min_status, &recv_tok);
128
129 if (maj_status == GSS_S_COMPLETE) {
130 /* If mutual state flag is not true, kex fails */
131 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
132 fatal("Mutual authentication failed");
133
134 /* If integ avail flag is not true kex fails */
135 if (!(ret_flags & GSS_C_INTEG_FLAG))
136 fatal("Integrity check failed");
137 }
138
139 /*
140 * If we have data to send, then the last message that we
141 * received cannot have been a 'complete'.
142 */
143 if (send_tok.length != 0) {
144 if (first) {
145 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_INIT)) != 0 ||
146 (r = sshpkt_put_string(ssh, send_tok.value,
147 send_tok.length)) != 0 ||
148 (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0)
149 fatal("failed to construct packet: %s", ssh_err(r));
150 first = 0;
151 } else {
152 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
153 (r = sshpkt_put_string(ssh, send_tok.value,
154 send_tok.length)) != 0)
155 fatal("failed to construct packet: %s", ssh_err(r));
156 }
157 if ((r = sshpkt_send(ssh)) != 0)
158 fatal("failed to send packet: %s", ssh_err(r));
159 gss_release_buffer(&min_status, &send_tok);
160
161 /* If we've sent them data, they should reply */
162 do {
163 type = ssh_packet_read(ssh);
164 if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
165 debug("Received KEXGSS_HOSTKEY");
166 if (server_host_key_blob)
167 fatal("Server host key received more than once");
168 if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
169 fatal("Failed to read server host key: %s", ssh_err(r));
170 }
171 } while (type == SSH2_MSG_KEXGSS_HOSTKEY);
172
173 switch (type) {
174 case SSH2_MSG_KEXGSS_CONTINUE:
175 debug("Received GSSAPI_CONTINUE");
176 if (maj_status == GSS_S_COMPLETE)
177 fatal("GSSAPI Continue received from server when complete");
178 if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
179 &recv_tok)) != 0 ||
180 (r = sshpkt_get_end(ssh)) != 0)
181 fatal("Failed to read token: %s", ssh_err(r));
182 break;
183 case SSH2_MSG_KEXGSS_COMPLETE:
184 debug("Received GSSAPI_COMPLETE");
185 if (msg_tok.value != NULL)
186 fatal("Received GSSAPI_COMPLETE twice?");
187 if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
188 (r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
189 &msg_tok)) != 0)
190 fatal("Failed to read message: %s", ssh_err(r));
191
192 /* Is there a token included? */
193 if ((r = sshpkt_get_u8(ssh, &c)) != 0)
194 fatal("sshpkt failed: %s", ssh_err(r));
195 if (c) {
196 if ((r = ssh_gssapi_sshpkt_get_buffer_desc(
197 ssh, &recv_tok)) != 0)
198 fatal("Failed to read token: %s", ssh_err(r));
199 /* If we're already complete - protocol error */
200 if (maj_status == GSS_S_COMPLETE)
201 sshpkt_disconnect(ssh, "Protocol error: received token when complete");
202 } else {
203 /* No token included */
204 if (maj_status != GSS_S_COMPLETE)
205 sshpkt_disconnect(ssh, "Protocol error: did not receive final token");
206 }
207 if ((r = sshpkt_get_end(ssh)) != 0) {
208 fatal("Expecting end of packet.");
209 }
210 break;
211 case SSH2_MSG_KEXGSS_ERROR:
212 debug("Received Error");
213 if ((r = sshpkt_get_u32(ssh, &maj_status)) != 0 ||
214 (r = sshpkt_get_u32(ssh, &min_status)) != 0 ||
215 (r = sshpkt_get_string(ssh, &msg, NULL)) != 0 ||
216 (r = sshpkt_get_string(ssh, NULL, NULL)) != 0 || /* lang tag */
217 (r = sshpkt_get_end(ssh)) != 0)
218 fatal("sshpkt_get failed: %s", ssh_err(r));
219 fatal("GSSAPI Error: \n%.400s", msg);
220 default:
221 sshpkt_disconnect(ssh, "Protocol error: didn't expect packet type %d",
222 type);
223 }
224 token_ptr = &recv_tok;
225 } else {
226 /* No data, and not complete */
227 if (maj_status != GSS_S_COMPLETE)
228 fatal("Not complete, and no token output");
229 }
230 } while (maj_status & GSS_S_CONTINUE_NEEDED);
231
232 /*
233 * We _must_ have received a COMPLETE message in reply from the
234 * server, which will have set server_blob and msg_tok
235 */
236
237 if (type != SSH2_MSG_KEXGSS_COMPLETE)
238 fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
239
240 /* compute shared secret */
241 switch (kex->kex_type) {
242 case KEX_GSS_GRP1_SHA1:
243 case KEX_GSS_GRP14_SHA1:
244 case KEX_GSS_GRP14_SHA256:
245 case KEX_GSS_GRP16_SHA512:
246 r = kex_dh_dec(kex, server_blob, &shared_secret);
247 break;
248 case KEX_GSS_C25519_SHA256:
249 if (sshbuf_ptr(server_blob)[sshbuf_len(server_blob)] & 0x80)
250 fatal("The received key has MSB of last octet set!");
251 r = kex_c25519_dec(kex, server_blob, &shared_secret);
252 break;
253 case KEX_GSS_NISTP256_SHA256:
254 if (sshbuf_len(server_blob) != 65)
255 fatal("The received NIST-P256 key did not match"
256 "expected length (expected 65, got %zu)", sshbuf_len(server_blob));
257
258 if (sshbuf_ptr(server_blob)[0] != POINT_CONVERSION_UNCOMPRESSED)
259 fatal("The received NIST-P256 key does not have first octet 0x04");
260
261 r = kex_ecdh_dec(kex, server_blob, &shared_secret);
262 break;
263 default:
264 r = SSH_ERR_INVALID_ARGUMENT;
265 break;
266 }
267 if (r != 0)
268 goto out;
269
270 if ((empty = sshbuf_new()) == NULL) {
271 r = SSH_ERR_ALLOC_FAIL;
272 goto out;
273 }
274
275 hashlen = sizeof(hash);
276 if ((r = kex_gen_hash(
277 kex->hash_alg,
278 kex->client_version,
279 kex->server_version,
280 kex->my,
281 kex->peer,
282 (server_host_key_blob ? server_host_key_blob : empty),
283 kex->client_pub,
284 server_blob,
285 shared_secret,
286 hash, &hashlen)) != 0)
287 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
288
289 gssbuf.value = hash;
290 gssbuf.length = hashlen;
291
292 /* Verify that the hash matches the MIC we just got. */
293 if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
294 sshpkt_disconnect(ssh, "Hash's MIC didn't verify");
295
296 gss_release_buffer(&min_status, &msg_tok);
297
298 if (kex->gss_deleg_creds)
299 ssh_gssapi_credentials_updated(ctxt);
300
301 if (gss_kex_context == NULL)
302 gss_kex_context = ctxt;
303 else
304 ssh_gssapi_delete_ctx(&ctxt);
305
306 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
307 r = kex_send_newkeys(ssh);
308
309out:
310 explicit_bzero(hash, sizeof(hash));
311 explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
312 sshbuf_free(empty);
313 sshbuf_free(server_host_key_blob);
314 sshbuf_free(server_blob);
315 sshbuf_free(shared_secret);
316 sshbuf_free(kex->client_pub);
317 kex->client_pub = NULL;
318 return r;
319}
320
321int
322kexgssgex_client(struct ssh *ssh)
323{
324 struct kex *kex = ssh->kex;
325 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER,
326 recv_tok = GSS_C_EMPTY_BUFFER, gssbuf,
327 msg_tok = GSS_C_EMPTY_BUFFER, *token_ptr;
328 Gssctxt *ctxt;
329 OM_uint32 maj_status, min_status, ret_flags;
330 struct sshbuf *shared_secret = NULL;
331 BIGNUM *p = NULL;
332 BIGNUM *g = NULL;
333 struct sshbuf *buf = NULL;
334 struct sshbuf *server_host_key_blob = NULL;
335 struct sshbuf *server_blob = NULL;
336 BIGNUM *dh_server_pub = NULL;
337 u_char *msg;
338 int type = 0;
339 int first = 1;
340 u_char hash[SSH_DIGEST_MAX_LENGTH];
341 size_t hashlen;
342 const BIGNUM *pub_key, *dh_p, *dh_g;
343 int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX;
344 struct sshbuf *empty = NULL;
345 u_char c;
346 int r;
347
348 /* Initialise our GSSAPI world */
349 ssh_gssapi_build_ctx(&ctxt);
350 if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type)
351 == GSS_C_NO_OID)
352 fatal("Couldn't identify host exchange");
353
354 if (ssh_gssapi_import_name(ctxt, kex->gss_host))
355 fatal("Couldn't import hostname");
356
357 if (kex->gss_client &&
358 ssh_gssapi_client_identity(ctxt, kex->gss_client))
359 fatal("Couldn't acquire client credentials");
360
361 debug("Doing group exchange");
362 nbits = dh_estimate(kex->dh_need * 8);
363
364 kex->min = DH_GRP_MIN;
365 kex->max = DH_GRP_MAX;
366 kex->nbits = nbits;
367 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_GROUPREQ)) != 0 ||
368 (r = sshpkt_put_u32(ssh, min)) != 0 ||
369 (r = sshpkt_put_u32(ssh, nbits)) != 0 ||
370 (r = sshpkt_put_u32(ssh, max)) != 0 ||
371 (r = sshpkt_send(ssh)) != 0)
372 fatal("Failed to construct a packet: %s", ssh_err(r));
373
374 if ((r = ssh_packet_read_expect(ssh, SSH2_MSG_KEXGSS_GROUP)) != 0)
375 fatal("Error: %s", ssh_err(r));
376
377 if ((r = sshpkt_get_bignum2(ssh, &p)) != 0 ||
378 (r = sshpkt_get_bignum2(ssh, &g)) != 0 ||
379 (r = sshpkt_get_end(ssh)) != 0)
380 fatal("shpkt_get_bignum2 failed: %s", ssh_err(r));
381
382 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
383 fatal("GSSGRP_GEX group out of range: %d !< %d !< %d",
384 min, BN_num_bits(p), max);
385
386 if ((kex->dh = dh_new_group(g, p)) == NULL)
387 fatal("dn_new_group() failed");
388 p = g = NULL; /* belong to kex->dh now */
389
390 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
391 goto out;
392 DH_get0_key(kex->dh, &pub_key, NULL);
393
394 token_ptr = GSS_C_NO_BUFFER;
395
396 do {
397 /* Step 2 - call GSS_Init_sec_context() */
398 debug("Calling gss_init_sec_context");
399
400 maj_status = ssh_gssapi_init_ctx(ctxt,
401 kex->gss_deleg_creds, token_ptr, &send_tok,
402 &ret_flags);
403
404 if (GSS_ERROR(maj_status)) {
405 /* XXX Useles code: Missing send? */
406 if (send_tok.length != 0) {
407 if ((r = sshpkt_start(ssh,
408 SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
409 (r = sshpkt_put_string(ssh, send_tok.value,
410 send_tok.length)) != 0)
411 fatal("sshpkt failed: %s", ssh_err(r));
412 }
413 fatal("gss_init_context failed");
414 }
415
416 /* If we've got an old receive buffer get rid of it */
417 if (token_ptr != GSS_C_NO_BUFFER)
418 gss_release_buffer(&min_status, &recv_tok);
419
420 if (maj_status == GSS_S_COMPLETE) {
421 /* If mutual state flag is not true, kex fails */
422 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
423 fatal("Mutual authentication failed");
424
425 /* If integ avail flag is not true kex fails */
426 if (!(ret_flags & GSS_C_INTEG_FLAG))
427 fatal("Integrity check failed");
428 }
429
430 /*
431 * If we have data to send, then the last message that we
432 * received cannot have been a 'complete'.
433 */
434 if (send_tok.length != 0) {
435 if (first) {
436 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_INIT)) != 0 ||
437 (r = sshpkt_put_string(ssh, send_tok.value,
438 send_tok.length)) != 0 ||
439 (r = sshpkt_put_bignum2(ssh, pub_key)) != 0)
440 fatal("sshpkt failed: %s", ssh_err(r));
441 first = 0;
442 } else {
443 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
444 (r = sshpkt_put_string(ssh,send_tok.value,
445 send_tok.length)) != 0)
446 fatal("sshpkt failed: %s", ssh_err(r));
447 }
448 if ((r = sshpkt_send(ssh)) != 0)
449 fatal("sshpkt_send failed: %s", ssh_err(r));
450 gss_release_buffer(&min_status, &send_tok);
451
452 /* If we've sent them data, they should reply */
453 do {
454 type = ssh_packet_read(ssh);
455 if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
456 debug("Received KEXGSS_HOSTKEY");
457 if (server_host_key_blob)
458 fatal("Server host key received more than once");
459 if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
460 fatal("sshpkt failed: %s", ssh_err(r));
461 }
462 } while (type == SSH2_MSG_KEXGSS_HOSTKEY);
463
464 switch (type) {
465 case SSH2_MSG_KEXGSS_CONTINUE:
466 debug("Received GSSAPI_CONTINUE");
467 if (maj_status == GSS_S_COMPLETE)
468 fatal("GSSAPI Continue received from server when complete");
469 if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
470 &recv_tok)) != 0 ||
471 (r = sshpkt_get_end(ssh)) != 0)
472 fatal("sshpkt failed: %s", ssh_err(r));
473 break;
474 case SSH2_MSG_KEXGSS_COMPLETE:
475 debug("Received GSSAPI_COMPLETE");
476 if (msg_tok.value != NULL)
477 fatal("Received GSSAPI_COMPLETE twice?");
478 if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
479 (r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
480 &msg_tok)) != 0)
481 fatal("sshpkt failed: %s", ssh_err(r));
482
483 /* Is there a token included? */
484 if ((r = sshpkt_get_u8(ssh, &c)) != 0)
485 fatal("sshpkt failed: %s", ssh_err(r));
486 if (c) {
487 if ((r = ssh_gssapi_sshpkt_get_buffer_desc(
488 ssh, &recv_tok)) != 0 ||
489 (r = sshpkt_get_end(ssh)) != 0)
490 fatal("sshpkt failed: %s", ssh_err(r));
491 /* If we're already complete - protocol error */
492 if (maj_status == GSS_S_COMPLETE)
493 sshpkt_disconnect(ssh, "Protocol error: received token when complete");
494 } else {
495 /* No token included */
496 if (maj_status != GSS_S_COMPLETE)
497 sshpkt_disconnect(ssh, "Protocol error: did not receive final token");
498 }
499 break;
500 case SSH2_MSG_KEXGSS_ERROR:
501 debug("Received Error");
502 if ((r = sshpkt_get_u32(ssh, &maj_status)) != 0 ||
503 (r = sshpkt_get_u32(ssh, &min_status)) != 0 ||
504 (r = sshpkt_get_string(ssh, &msg, NULL)) != 0 ||
505 (r = sshpkt_get_string(ssh, NULL, NULL)) != 0 || /* lang tag */
506 (r = sshpkt_get_end(ssh)) != 0)
507 fatal("sshpkt failed: %s", ssh_err(r));
508 fatal("GSSAPI Error: \n%.400s", msg);
509 default:
510 sshpkt_disconnect(ssh, "Protocol error: didn't expect packet type %d",
511 type);
512 }
513 token_ptr = &recv_tok;
514 } else {
515 /* No data, and not complete */
516 if (maj_status != GSS_S_COMPLETE)
517 fatal("Not complete, and no token output");
518 }
519 } while (maj_status & GSS_S_CONTINUE_NEEDED);
520
521 /*
522 * We _must_ have received a COMPLETE message in reply from the
523 * server, which will have set dh_server_pub and msg_tok
524 */
525
526 if (type != SSH2_MSG_KEXGSS_COMPLETE)
527 fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
528
529 /* 7. C verifies that the key Q_S is valid */
530 /* 8. C computes shared secret */
531 if ((buf = sshbuf_new()) == NULL ||
532 (r = sshbuf_put_stringb(buf, server_blob)) != 0 ||
533 (r = sshbuf_get_bignum2(buf, &dh_server_pub)) != 0)
534 goto out;
535 sshbuf_free(buf);
536 buf = NULL;
537
538 if ((shared_secret = sshbuf_new()) == NULL) {
539 r = SSH_ERR_ALLOC_FAIL;
540 goto out;
541 }
542
543 if ((r = kex_dh_compute_key(kex, dh_server_pub, shared_secret)) != 0)
544 goto out;
545 if ((empty = sshbuf_new()) == NULL) {
546 r = SSH_ERR_ALLOC_FAIL;
547 goto out;
548 }
549
550 DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
551 hashlen = sizeof(hash);
552 if ((r = kexgex_hash(
553 kex->hash_alg,
554 kex->client_version,
555 kex->server_version,
556 kex->my,
557 kex->peer,
558 (server_host_key_blob ? server_host_key_blob : empty),
559 kex->min, kex->nbits, kex->max,
560 dh_p, dh_g,
561 pub_key,
562 dh_server_pub,
563 sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
564 hash, &hashlen)) != 0)
565 fatal("Failed to calculate hash: %s", ssh_err(r));
566
567 gssbuf.value = hash;
568 gssbuf.length = hashlen;
569
570 /* Verify that the hash matches the MIC we just got. */
571 if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
572 sshpkt_disconnect(ssh, "Hash's MIC didn't verify");
573
574 gss_release_buffer(&min_status, &msg_tok);
575
576 /* save session id */
577 if (kex->session_id == NULL) {
578 kex->session_id_len = hashlen;
579 kex->session_id = xmalloc(kex->session_id_len);
580 memcpy(kex->session_id, hash, kex->session_id_len);
581 }
582
583 if (kex->gss_deleg_creds)
584 ssh_gssapi_credentials_updated(ctxt);
585
586 if (gss_kex_context == NULL)
587 gss_kex_context = ctxt;
588 else
589 ssh_gssapi_delete_ctx(&ctxt);
590
591 /* Finally derive the keys and send them */
592 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
593 r = kex_send_newkeys(ssh);
594out:
595 sshbuf_free(buf);
596 sshbuf_free(server_blob);
597 sshbuf_free(empty);
598 explicit_bzero(hash, sizeof(hash));
599 DH_free(kex->dh);
600 kex->dh = NULL;
601 BN_clear_free(dh_server_pub);
602 sshbuf_free(shared_secret);
603 sshbuf_free(server_host_key_blob);
604 return r;
605}
606#endif /* defined(GSSAPI) && defined(WITH_OPENSSL) */
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-02 13:48:48 +0000