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Diffstat (limited to 'kexgsss.c')
-rw-r--r-- | kexgsss.c | 295 |
1 files changed, 295 insertions, 0 deletions
diff --git a/kexgsss.c b/kexgsss.c new file mode 100644 index 000000000..31ec6a890 --- /dev/null +++ b/kexgsss.c | |||
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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 | #ifdef GSSAPI | ||
28 | |||
29 | #include <string.h> | ||
30 | |||
31 | #include <openssl/crypto.h> | ||
32 | #include <openssl/bn.h> | ||
33 | |||
34 | #include "xmalloc.h" | ||
35 | #include "sshbuf.h" | ||
36 | #include "ssh2.h" | ||
37 | #include "sshkey.h" | ||
38 | #include "cipher.h" | ||
39 | #include "kex.h" | ||
40 | #include "log.h" | ||
41 | #include "packet.h" | ||
42 | #include "dh.h" | ||
43 | #include "ssh-gss.h" | ||
44 | #include "monitor_wrap.h" | ||
45 | #include "misc.h" | ||
46 | #include "servconf.h" | ||
47 | #include "digest.h" | ||
48 | |||
49 | extern ServerOptions options; | ||
50 | |||
51 | int | ||
52 | kexgss_server(struct ssh *ssh) | ||
53 | { | ||
54 | OM_uint32 maj_status, min_status; | ||
55 | |||
56 | /* | ||
57 | * Some GSSAPI implementations use the input value of ret_flags (an | ||
58 | * output variable) as a means of triggering mechanism specific | ||
59 | * features. Initializing it to zero avoids inadvertently | ||
60 | * activating this non-standard behaviour. | ||
61 | */ | ||
62 | |||
63 | OM_uint32 ret_flags = 0; | ||
64 | gss_buffer_desc gssbuf, recv_tok, msg_tok; | ||
65 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | ||
66 | Gssctxt *ctxt = NULL; | ||
67 | u_int slen, klen, kout; | ||
68 | u_char *kbuf; | ||
69 | DH *dh; | ||
70 | int min = -1, max = -1, nbits = -1; | ||
71 | BIGNUM *shared_secret = NULL; | ||
72 | BIGNUM *dh_client_pub = NULL; | ||
73 | int type = 0; | ||
74 | gss_OID oid; | ||
75 | char *mechs; | ||
76 | u_char hash[SSH_DIGEST_MAX_LENGTH]; | ||
77 | size_t hashlen; | ||
78 | |||
79 | /* Initialise GSSAPI */ | ||
80 | |||
81 | /* If we're rekeying, privsep means that some of the private structures | ||
82 | * in the GSSAPI code are no longer available. This kludges them back | ||
83 | * into life | ||
84 | */ | ||
85 | if (!ssh_gssapi_oid_table_ok()) { | ||
86 | mechs = ssh_gssapi_server_mechanisms(); | ||
87 | free(mechs); | ||
88 | } | ||
89 | |||
90 | debug2("%s: Identifying %s", __func__, ssh->kex->name); | ||
91 | oid = ssh_gssapi_id_kex(NULL, ssh->kex->name, ssh->kex->kex_type); | ||
92 | if (oid == GSS_C_NO_OID) | ||
93 | fatal("Unknown gssapi mechanism"); | ||
94 | |||
95 | debug2("%s: Acquiring credentials", __func__); | ||
96 | |||
97 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) | ||
98 | fatal("Unable to acquire credentials for the server"); | ||
99 | |||
100 | switch (ssh->kex->kex_type) { | ||
101 | case KEX_GSS_GRP1_SHA1: | ||
102 | dh = dh_new_group1(); | ||
103 | break; | ||
104 | case KEX_GSS_GRP14_SHA1: | ||
105 | dh = dh_new_group14(); | ||
106 | break; | ||
107 | case KEX_GSS_GEX_SHA1: | ||
108 | debug("Doing group exchange"); | ||
109 | packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ); | ||
110 | min = packet_get_int(); | ||
111 | nbits = packet_get_int(); | ||
112 | max = packet_get_int(); | ||
113 | packet_check_eom(); | ||
114 | if (max < min || nbits < min || max < nbits) | ||
115 | fatal("GSS_GEX, bad parameters: %d !< %d !< %d", | ||
116 | min, nbits, max); | ||
117 | dh = PRIVSEP(choose_dh(MAX(DH_GRP_MIN, min), | ||
118 | nbits, MIN(DH_GRP_MAX, max))); | ||
119 | if (dh == NULL) | ||
120 | packet_disconnect("Protocol error: no matching group found"); | ||
121 | |||
122 | packet_start(SSH2_MSG_KEXGSS_GROUP); | ||
123 | packet_put_bignum2(dh->p); | ||
124 | packet_put_bignum2(dh->g); | ||
125 | packet_send(); | ||
126 | |||
127 | packet_write_wait(); | ||
128 | break; | ||
129 | default: | ||
130 | fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type); | ||
131 | } | ||
132 | |||
133 | dh_gen_key(dh, ssh->kex->we_need * 8); | ||
134 | |||
135 | do { | ||
136 | debug("Wait SSH2_MSG_GSSAPI_INIT"); | ||
137 | type = packet_read(); | ||
138 | switch(type) { | ||
139 | case SSH2_MSG_KEXGSS_INIT: | ||
140 | if (dh_client_pub != NULL) | ||
141 | fatal("Received KEXGSS_INIT after initialising"); | ||
142 | recv_tok.value = packet_get_string(&slen); | ||
143 | recv_tok.length = slen; | ||
144 | |||
145 | if ((dh_client_pub = BN_new()) == NULL) | ||
146 | fatal("dh_client_pub == NULL"); | ||
147 | |||
148 | packet_get_bignum2(dh_client_pub); | ||
149 | |||
150 | /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */ | ||
151 | break; | ||
152 | case SSH2_MSG_KEXGSS_CONTINUE: | ||
153 | recv_tok.value = packet_get_string(&slen); | ||
154 | recv_tok.length = slen; | ||
155 | break; | ||
156 | default: | ||
157 | packet_disconnect( | ||
158 | "Protocol error: didn't expect packet type %d", | ||
159 | type); | ||
160 | } | ||
161 | |||
162 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok, | ||
163 | &send_tok, &ret_flags)); | ||
164 | |||
165 | free(recv_tok.value); | ||
166 | |||
167 | if (maj_status != GSS_S_COMPLETE && send_tok.length == 0) | ||
168 | fatal("Zero length token output when incomplete"); | ||
169 | |||
170 | if (dh_client_pub == NULL) | ||
171 | fatal("No client public key"); | ||
172 | |||
173 | if (maj_status & GSS_S_CONTINUE_NEEDED) { | ||
174 | debug("Sending GSSAPI_CONTINUE"); | ||
175 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | ||
176 | packet_put_string(send_tok.value, send_tok.length); | ||
177 | packet_send(); | ||
178 | gss_release_buffer(&min_status, &send_tok); | ||
179 | } | ||
180 | } while (maj_status & GSS_S_CONTINUE_NEEDED); | ||
181 | |||
182 | if (GSS_ERROR(maj_status)) { | ||
183 | if (send_tok.length > 0) { | ||
184 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | ||
185 | packet_put_string(send_tok.value, send_tok.length); | ||
186 | packet_send(); | ||
187 | } | ||
188 | fatal("accept_ctx died"); | ||
189 | } | ||
190 | |||
191 | if (!(ret_flags & GSS_C_MUTUAL_FLAG)) | ||
192 | fatal("Mutual Authentication flag wasn't set"); | ||
193 | |||
194 | if (!(ret_flags & GSS_C_INTEG_FLAG)) | ||
195 | fatal("Integrity flag wasn't set"); | ||
196 | |||
197 | if (!dh_pub_is_valid(dh, dh_client_pub)) | ||
198 | packet_disconnect("bad client public DH value"); | ||
199 | |||
200 | klen = DH_size(dh); | ||
201 | kbuf = xmalloc(klen); | ||
202 | kout = DH_compute_key(kbuf, dh_client_pub, dh); | ||
203 | if (kout < 0) | ||
204 | fatal("DH_compute_key: failed"); | ||
205 | |||
206 | shared_secret = BN_new(); | ||
207 | if (shared_secret == NULL) | ||
208 | fatal("kexgss_server: BN_new failed"); | ||
209 | |||
210 | if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) | ||
211 | fatal("kexgss_server: BN_bin2bn failed"); | ||
212 | |||
213 | memset(kbuf, 0, klen); | ||
214 | free(kbuf); | ||
215 | |||
216 | hashlen = sizeof(hash); | ||
217 | switch (ssh->kex->kex_type) { | ||
218 | case KEX_GSS_GRP1_SHA1: | ||
219 | case KEX_GSS_GRP14_SHA1: | ||
220 | kex_dh_hash( | ||
221 | ssh->kex->hash_alg, | ||
222 | ssh->kex->client_version_string, ssh->kex->server_version_string, | ||
223 | sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer), | ||
224 | sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my), | ||
225 | NULL, 0, /* Change this if we start sending host keys */ | ||
226 | dh_client_pub, dh->pub_key, shared_secret, | ||
227 | hash, &hashlen | ||
228 | ); | ||
229 | break; | ||
230 | case KEX_GSS_GEX_SHA1: | ||
231 | kexgex_hash( | ||
232 | ssh->kex->hash_alg, | ||
233 | ssh->kex->client_version_string, ssh->kex->server_version_string, | ||
234 | sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer), | ||
235 | sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my), | ||
236 | NULL, 0, | ||
237 | min, nbits, max, | ||
238 | dh->p, dh->g, | ||
239 | dh_client_pub, | ||
240 | dh->pub_key, | ||
241 | shared_secret, | ||
242 | hash, &hashlen | ||
243 | ); | ||
244 | break; | ||
245 | default: | ||
246 | fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type); | ||
247 | } | ||
248 | |||
249 | BN_clear_free(dh_client_pub); | ||
250 | |||
251 | if (ssh->kex->session_id == NULL) { | ||
252 | ssh->kex->session_id_len = hashlen; | ||
253 | ssh->kex->session_id = xmalloc(ssh->kex->session_id_len); | ||
254 | memcpy(ssh->kex->session_id, hash, ssh->kex->session_id_len); | ||
255 | } | ||
256 | |||
257 | gssbuf.value = hash; | ||
258 | gssbuf.length = hashlen; | ||
259 | |||
260 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok)))) | ||
261 | fatal("Couldn't get MIC"); | ||
262 | |||
263 | packet_start(SSH2_MSG_KEXGSS_COMPLETE); | ||
264 | packet_put_bignum2(dh->pub_key); | ||
265 | packet_put_string(msg_tok.value,msg_tok.length); | ||
266 | |||
267 | if (send_tok.length != 0) { | ||
268 | packet_put_char(1); /* true */ | ||
269 | packet_put_string(send_tok.value, send_tok.length); | ||
270 | } else { | ||
271 | packet_put_char(0); /* false */ | ||
272 | } | ||
273 | packet_send(); | ||
274 | |||
275 | gss_release_buffer(&min_status, &send_tok); | ||
276 | gss_release_buffer(&min_status, &msg_tok); | ||
277 | |||
278 | if (gss_kex_context == NULL) | ||
279 | gss_kex_context = ctxt; | ||
280 | else | ||
281 | ssh_gssapi_delete_ctx(&ctxt); | ||
282 | |||
283 | DH_free(dh); | ||
284 | |||
285 | kex_derive_keys_bn(ssh, hash, hashlen, shared_secret); | ||
286 | BN_clear_free(shared_secret); | ||
287 | kex_send_newkeys(ssh); | ||
288 | |||
289 | /* If this was a rekey, then save out any delegated credentials we | ||
290 | * just exchanged. */ | ||
291 | if (options.gss_store_rekey) | ||
292 | ssh_gssapi_rekey_creds(); | ||
293 | return 0; | ||
294 | } | ||
295 | #endif /* GSSAPI */ | ||