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1c14df9e | 1 | /* |
2e437378 | 2 | * Copyright (c) 2001-2006 Simon Wilkinson. All rights reserved. |
1c14df9e | 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 | #ifdef GSSAPI | |
28 | ||
29 | #include <openssl/crypto.h> | |
30 | #include <openssl/bn.h> | |
31 | ||
2e437378 | 32 | #include <string.h> |
33 | ||
1c14df9e | 34 | #include "xmalloc.h" |
35 | #include "buffer.h" | |
2e437378 | 36 | #include "ssh2.h" |
37 | #include "key.h" | |
38 | #include "cipher.h" | |
1c14df9e | 39 | #include "kex.h" |
40 | #include "log.h" | |
41 | #include "packet.h" | |
42 | #include "dh.h" | |
2e437378 | 43 | |
1c14df9e | 44 | #include "ssh-gss.h" |
1c14df9e | 45 | |
1c14df9e | 46 | void |
34fee935 | 47 | kexgss_client(Kex *kex) { |
48 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
2e437378 | 49 | gss_buffer_desc recv_tok, gssbuf, msg_tok, *token_ptr; |
1c14df9e | 50 | Gssctxt *ctxt; |
51 | OM_uint32 maj_status, min_status, ret_flags; | |
e00da40d | 52 | u_int klen, kout, slen = 0, hashlen, strlen; |
1c14df9e | 53 | DH *dh; |
34fee935 | 54 | BIGNUM *dh_server_pub = NULL; |
55 | BIGNUM *shared_secret = NULL; | |
56 | BIGNUM *p = NULL; | |
57 | BIGNUM *g = NULL; | |
e00da40d | 58 | u_char *kbuf, *hash; |
59 | u_char *serverhostkey = NULL; | |
88928908 | 60 | char *msg; |
61 | char *lang; | |
1c14df9e | 62 | int type = 0; |
63 | int first = 1; | |
e00da40d | 64 | int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX; |
34fee935 | 65 | |
66 | /* Initialise our GSSAPI world */ | |
1c14df9e | 67 | ssh_gssapi_build_ctx(&ctxt); |
2e437378 | 68 | if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type) |
69 | == GSS_C_NO_OID) | |
1c14df9e | 70 | fatal("Couldn't identify host exchange"); |
8bb69cbe | 71 | |
34fee935 | 72 | if (ssh_gssapi_import_name(ctxt, kex->gss_host)) |
73 | fatal("Couldn't import hostname"); | |
74 | ||
2e437378 | 75 | switch (kex->kex_type) { |
76 | case KEX_GSS_GRP1_SHA1: | |
77 | dh = dh_new_group1(); | |
78 | break; | |
79 | case KEX_GSS_GRP14_SHA1: | |
80 | dh = dh_new_group14(); | |
81 | break; | |
82 | case KEX_GSS_GEX_SHA1: | |
34fee935 | 83 | debug("Doing group exchange\n"); |
84 | nbits = dh_estimate(kex->we_need * 8); | |
34fee935 | 85 | packet_start(SSH2_MSG_KEXGSS_GROUPREQ); |
86 | packet_put_int(min); | |
87 | packet_put_int(nbits); | |
88 | packet_put_int(max); | |
89 | ||
90 | packet_send(); | |
91 | ||
92 | packet_read_expect(SSH2_MSG_KEXGSS_GROUP); | |
93 | ||
94 | if ((p = BN_new()) == NULL) | |
95 | fatal("BN_new() failed"); | |
96 | packet_get_bignum2(p); | |
97 | if ((g = BN_new()) == NULL) | |
98 | fatal("BN_new() failed"); | |
99 | packet_get_bignum2(g); | |
100 | packet_check_eom(); | |
101 | ||
102 | if (BN_num_bits(p) < min || BN_num_bits(p) > max) | |
103 | fatal("GSSGRP_GEX group out of range: %d !< %d !< %d", | |
104 | min, BN_num_bits(p), max); | |
105 | ||
106 | dh = dh_new_group(g, p); | |
2e437378 | 107 | break; |
108 | default: | |
109 | fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); | |
1c14df9e | 110 | } |
111 | ||
1c14df9e | 112 | /* Step 1 - e is dh->pub_key */ |
1c14df9e | 113 | dh_gen_key(dh, kex->we_need * 8); |
114 | ||
115 | /* This is f, we initialise it now to make life easier */ | |
34fee935 | 116 | dh_server_pub = BN_new(); |
117 | if (dh_server_pub == NULL) | |
118 | fatal("dh_server_pub == NULL"); | |
119 | ||
1c14df9e | 120 | token_ptr = GSS_C_NO_BUFFER; |
121 | ||
122 | do { | |
123 | debug("Calling gss_init_sec_context"); | |
124 | ||
34fee935 | 125 | maj_status = ssh_gssapi_init_ctx(ctxt, |
126 | kex->gss_deleg_creds, token_ptr, &send_tok, | |
127 | &ret_flags); | |
1c14df9e | 128 | |
129 | if (GSS_ERROR(maj_status)) { | |
34fee935 | 130 | if (send_tok.length != 0) { |
88928908 | 131 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); |
132 | packet_put_string(send_tok.value, | |
34fee935 | 133 | send_tok.length); |
134 | } | |
1c14df9e | 135 | fatal("gss_init_context failed"); |
88928908 | 136 | } |
1c14df9e | 137 | |
138 | /* If we've got an old receive buffer get rid of it */ | |
139 | if (token_ptr != GSS_C_NO_BUFFER) | |
34fee935 | 140 | xfree(recv_tok.value); |
141 | ||
1c14df9e | 142 | if (maj_status == GSS_S_COMPLETE) { |
143 | /* If mutual state flag is not true, kex fails */ | |
34fee935 | 144 | if (!(ret_flags & GSS_C_MUTUAL_FLAG)) |
1c14df9e | 145 | fatal("Mutual authentication failed"); |
34fee935 | 146 | |
1c14df9e | 147 | /* If integ avail flag is not true kex fails */ |
34fee935 | 148 | if (!(ret_flags & GSS_C_INTEG_FLAG)) |
1c14df9e | 149 | fatal("Integrity check failed"); |
1c14df9e | 150 | } |
34fee935 | 151 | |
152 | /* | |
153 | * If we have data to send, then the last message that we | |
154 | * received cannot have been a 'complete'. | |
155 | */ | |
156 | if (send_tok.length != 0) { | |
1c14df9e | 157 | if (first) { |
158 | packet_start(SSH2_MSG_KEXGSS_INIT); | |
159 | packet_put_string(send_tok.value, | |
34fee935 | 160 | send_tok.length); |
1c14df9e | 161 | packet_put_bignum2(dh->pub_key); |
34fee935 | 162 | first = 0; |
1c14df9e | 163 | } else { |
164 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | |
165 | packet_put_string(send_tok.value, | |
34fee935 | 166 | send_tok.length); |
1c14df9e | 167 | } |
168 | packet_send(); | |
34fee935 | 169 | gss_release_buffer(&min_status, &send_tok); |
170 | ||
171 | /* If we've sent them data, they should reply */ | |
172 | do { | |
173 | type = packet_read(); | |
174 | if (type == SSH2_MSG_KEXGSS_HOSTKEY) { | |
175 | debug("Received KEXGSS_HOSTKEY"); | |
176 | if (serverhostkey) | |
177 | fatal("Server host key received more than once"); | |
178 | serverhostkey = | |
179 | packet_get_string(&slen); | |
180 | } | |
181 | } while (type == SSH2_MSG_KEXGSS_HOSTKEY); | |
1c14df9e | 182 | |
1c14df9e | 183 | switch (type) { |
1c14df9e | 184 | case SSH2_MSG_KEXGSS_CONTINUE: |
185 | debug("Received GSSAPI_CONTINUE"); | |
186 | if (maj_status == GSS_S_COMPLETE) | |
187 | fatal("GSSAPI Continue received from server when complete"); | |
34fee935 | 188 | recv_tok.value = packet_get_string(&strlen); |
189 | recv_tok.length = strlen; | |
1c14df9e | 190 | break; |
191 | case SSH2_MSG_KEXGSS_COMPLETE: | |
192 | debug("Received GSSAPI_COMPLETE"); | |
34fee935 | 193 | packet_get_bignum2(dh_server_pub); |
194 | msg_tok.value = packet_get_string(&strlen); | |
195 | msg_tok.length = strlen; | |
1c14df9e | 196 | |
197 | /* Is there a token included? */ | |
198 | if (packet_get_char()) { | |
199 | recv_tok.value= | |
88928908 | 200 | packet_get_string(&strlen); |
34fee935 | 201 | recv_tok.length = strlen; |
1c14df9e | 202 | /* If we're already complete - protocol error */ |
203 | if (maj_status == GSS_S_COMPLETE) | |
204 | packet_disconnect("Protocol error: received token when complete"); | |
34fee935 | 205 | } else { |
206 | /* No token included */ | |
207 | if (maj_status != GSS_S_COMPLETE) | |
208 | packet_disconnect("Protocol error: did not receive final token"); | |
1c14df9e | 209 | } |
210 | break; | |
88928908 | 211 | case SSH2_MSG_KEXGSS_ERROR: |
212 | debug("Received Error"); | |
34fee935 | 213 | maj_status = packet_get_int(); |
214 | min_status = packet_get_int(); | |
215 | msg = packet_get_string(NULL); | |
216 | lang = packet_get_string(NULL); | |
2e437378 | 217 | fatal("GSSAPI Error: \n%.400s",msg); |
1c14df9e | 218 | default: |
219 | packet_disconnect("Protocol error: didn't expect packet type %d", | |
220 | type); | |
221 | } | |
34fee935 | 222 | token_ptr = &recv_tok; |
88928908 | 223 | } else { |
224 | /* No data, and not complete */ | |
34fee935 | 225 | if (maj_status != GSS_S_COMPLETE) |
88928908 | 226 | fatal("Not complete, and no token output"); |
1c14df9e | 227 | } |
34fee935 | 228 | } while (maj_status & GSS_S_CONTINUE_NEEDED); |
229 | ||
230 | /* | |
231 | * We _must_ have received a COMPLETE message in reply from the | |
232 | * server, which will have set dh_server_pub and msg_tok | |
233 | */ | |
234 | ||
235 | if (type != SSH2_MSG_KEXGSS_COMPLETE) | |
236 | fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it"); | |
237 | ||
1c14df9e | 238 | /* Check f in range [1, p-1] */ |
34fee935 | 239 | if (!dh_pub_is_valid(dh, dh_server_pub)) |
240 | packet_disconnect("bad server public DH value"); | |
1c14df9e | 241 | |
34fee935 | 242 | /* compute K=f^x mod p */ |
243 | klen = DH_size(dh); | |
244 | kbuf = xmalloc(klen); | |
245 | kout = DH_compute_key(kbuf, dh_server_pub, dh); | |
246 | ||
247 | shared_secret = BN_new(); | |
248 | BN_bin2bn(kbuf,kout, shared_secret); | |
249 | memset(kbuf, 0, klen); | |
250 | xfree(kbuf); | |
251 | ||
2e437378 | 252 | switch (kex->kex_type) { |
253 | case KEX_GSS_GRP1_SHA1: | |
254 | case KEX_GSS_GRP14_SHA1: | |
255 | kex_dh_hash( kex->client_version_string, | |
256 | kex->server_version_string, | |
257 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
258 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
259 | serverhostkey, slen, /* server host key */ | |
260 | dh->pub_key, /* e */ | |
261 | dh_server_pub, /* f */ | |
262 | shared_secret, /* K */ | |
263 | &hash, &hashlen | |
264 | ); | |
265 | break; | |
266 | case KEX_GSS_GEX_SHA1: | |
e00da40d | 267 | kexgex_hash( |
268 | kex->evp_md, | |
269 | kex->client_version_string, | |
34fee935 | 270 | kex->server_version_string, |
271 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
272 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
273 | serverhostkey, slen, | |
274 | min, nbits, max, | |
275 | dh->p, dh->g, | |
276 | dh->pub_key, | |
277 | dh_server_pub, | |
e00da40d | 278 | shared_secret, |
279 | &hash, &hashlen | |
34fee935 | 280 | ); |
2e437378 | 281 | break; |
282 | default: | |
283 | fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); | |
284 | } | |
34fee935 | 285 | |
286 | gssbuf.value = hash; | |
e00da40d | 287 | gssbuf.length = hashlen; |
34fee935 | 288 | |
2e437378 | 289 | /* Verify that the hash matches the MIC we just got. */ |
34fee935 | 290 | if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok))) |
291 | packet_disconnect("Hash's MIC didn't verify"); | |
292 | ||
293 | xfree(msg_tok.value); | |
294 | ||
295 | DH_free(dh); | |
296 | if (serverhostkey) | |
297 | xfree(serverhostkey); | |
298 | BN_clear_free(dh_server_pub); | |
299 | ||
300 | /* save session id */ | |
301 | if (kex->session_id == NULL) { | |
e00da40d | 302 | kex->session_id_len = hashlen; |
34fee935 | 303 | kex->session_id = xmalloc(kex->session_id_len); |
304 | memcpy(kex->session_id, hash, kex->session_id_len); | |
305 | } | |
306 | ||
307 | if (gss_kex_context == NULL) | |
308 | gss_kex_context = ctxt; | |
309 | else | |
310 | ssh_gssapi_delete_ctx(&ctxt); | |
311 | ||
e00da40d | 312 | kex_derive_keys(kex, hash, hashlen, shared_secret); |
1c14df9e | 313 | BN_clear_free(shared_secret); |
34fee935 | 314 | kex_finish(kex); |
1c14df9e | 315 | } |
316 | ||
317 | #endif /* GSSAPI */ |