1 /*
2 * Copyright (c) 2001-2003 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 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
26 * Use is subject to license terms.
27 */
28
29 #pragma ident "%Z%%M% %I% %E% SMI"
30
31 #include "includes.h"
32
33 #ifdef GSSAPI
34
35 #include <openssl/crypto.h>
36 #include <openssl/bn.h>
37
38 #include "xmalloc.h"
39 #include "buffer.h"
40 #include "bufaux.h"
41 #include "compat.h"
42 #include "kex.h"
43 #include "log.h"
44 #include "packet.h"
45 #include "dh.h"
46 #include "ssh2.h"
47 #include "ssh-gss.h"
48 #include "auth.h"
49
50 Gssctxt *xxx_gssctxt;
51 extern Authctxt *x_authctxt;
52
53 static void kex_gss_send_error(Gssctxt *ctxt);
54
55 void
56 kexgss_server(Kex *kex)
57 {
58 OM_uint32 maj_status, min_status;
59 gss_buffer_desc gssbuf, send_tok, recv_tok, msg_tok;
60 Gssctxt *ctxt = NULL;
61 unsigned int klen, kout;
62 unsigned int sbloblen = 0;
63 unsigned char *kbuf, *hash;
64 unsigned char *server_host_key_blob = NULL;
65 DH *dh;
66 Key *server_host_key = NULL;
67 BIGNUM *shared_secret = NULL;
68 BIGNUM *dh_client_pub = NULL;
69 int type = 0;
70 uint_t slen;
71 gss_OID oid;
72
73 /*
74 * Load host key to advertise in a SSH_MSG_KEXGSS_HOSTKEY packet
75 * -- unlike KEX_DH/KEX_GEX no host key, no problem since it's
76 * the GSS-API that provides for server host authentication.
77 */
78 if (kex->load_host_key != NULL &&
79 !(datafellows & SSH_BUG_GSSKEX_HOSTKEY))
80 server_host_key = kex->load_host_key(kex->hostkey_type);
81 if (server_host_key != NULL)
82 key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
83
84
85 /* Initialise GSSAPI */
86
87 ssh_gssapi_oid_of_kexname(kex->name, &oid);
88 if (oid == GSS_C_NULL_OID) {
89 fatal("Couldn't match the negotiated GSS key exchange");
90 }
91
92 ssh_gssapi_build_ctx(&xxx_gssctxt, 0, oid);
93
94 ctxt = xxx_gssctxt;
95
96 do {
97 debug("Wait SSH2_MSG_GSSAPI_INIT");
98 type = packet_read();
99 switch (type) {
100 case SSH2_MSG_KEXGSS_INIT:
101 if (dh_client_pub != NULL)
102 fatal("Received KEXGSS_INIT after "
103 "initialising");
104 recv_tok.value = packet_get_string(&slen);
105 recv_tok.length = slen; /* int vs. size_t */
106
107 dh_client_pub = BN_new();
108
109 if (dh_client_pub == NULL)
110 fatal("dh_client_pub == NULL");
111 packet_get_bignum2(dh_client_pub);
112
113 /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
114 if (sbloblen) {
115 packet_start(SSH2_MSG_KEXGSS_HOSTKEY);
116 packet_put_string(server_host_key_blob,
117 sbloblen);
118 packet_send();
119 packet_write_wait();
120 }
121 break;
122 case SSH2_MSG_KEXGSS_CONTINUE:
123 recv_tok.value = packet_get_string(&slen);
124 recv_tok.length = slen; /* int vs. size_t */
125 break;
126 default:
127 packet_disconnect("Protocol error: didn't expect "
128 "packet type %d", type);
129 }
130
131 maj_status = ssh_gssapi_accept_ctx(ctxt, &recv_tok, &send_tok);
132
133 xfree(recv_tok.value); /* We allocated this, not gss */
134
135 if (dh_client_pub == NULL)
136 fatal("No client public key");
137
138 if (maj_status == GSS_S_CONTINUE_NEEDED) {
139 debug("Sending GSSAPI_CONTINUE");
140 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
141 packet_put_string(send_tok.value, send_tok.length);
142 packet_send();
143 packet_write_wait();
144 (void) gss_release_buffer(&min_status, &send_tok);
145 }
146 } while (maj_status == GSS_S_CONTINUE_NEEDED);
147
148 if (GSS_ERROR(maj_status)) {
149 kex_gss_send_error(ctxt);
150 if (send_tok.length > 0) {
151 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
152 packet_put_string(send_tok.value, send_tok.length);
153 packet_send();
154 packet_write_wait();
155 (void) gss_release_buffer(&min_status, &send_tok);
156 }
157 fatal("accept_ctx died");
158 }
159
160 debug("gss_complete");
161 if (!(ctxt->flags & GSS_C_MUTUAL_FLAG))
162 fatal("Mutual authentication flag wasn't set");
163
164 if (!(ctxt->flags & GSS_C_INTEG_FLAG))
165 fatal("Integrity flag wasn't set");
166
167 dh = dh_new_group1();
168 dh_gen_key(dh, kex->we_need * 8);
169
170 if (!dh_pub_is_valid(dh, dh_client_pub))
171 packet_disconnect("bad client public DH value");
172
173 klen = DH_size(dh);
174 kbuf = xmalloc(klen);
175 kout = DH_compute_key(kbuf, dh_client_pub, dh);
176
177 shared_secret = BN_new();
178 BN_bin2bn(kbuf, kout, shared_secret);
179 (void) memset(kbuf, 0, klen);
180 xfree(kbuf);
181
182 /* The GSSAPI hash is identical to the Diffie Helman one */
183 hash = kex_dh_hash(
184 kex->client_version_string,
185 kex->server_version_string,
186 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
187 buffer_ptr(&kex->my), buffer_len(&kex->my),
188 server_host_key_blob, sbloblen,
189 dh_client_pub,
190 dh->pub_key,
191 shared_secret);
192
193 BN_free(dh_client_pub);
194
195 if (kex->session_id == NULL) {
196 kex->session_id_len = 20;
197 kex->session_id = xmalloc(kex->session_id_len);
198 (void) memcpy(kex->session_id, hash, kex->session_id_len);
199 } else if (x_authctxt != NULL && x_authctxt->success) {
200 ssh_gssapi_storecreds(ctxt, x_authctxt);
201 }
202
203 /* Should fix kex_dh_hash to output hash length */
204 gssbuf.length = 20; /* yes, it's always 20 (SHA-1) */
205 gssbuf.value = hash; /* and it's static constant storage */
206
207 if (GSS_ERROR(ssh_gssapi_get_mic(ctxt, &gssbuf, &msg_tok))) {
208 kex_gss_send_error(ctxt);
209 fatal("Couldn't get MIC");
210 }
211
212 packet_start(SSH2_MSG_KEXGSS_COMPLETE);
213 packet_put_bignum2(dh->pub_key);
214 packet_put_string((char *)msg_tok.value, msg_tok.length);
215 (void) gss_release_buffer(&min_status, &msg_tok);
216
217 if (send_tok.length != 0) {
218 packet_put_char(1); /* true */
219 packet_put_string((char *)send_tok.value, send_tok.length);
220 (void) gss_release_buffer(&min_status, &send_tok);
221 } else {
222 packet_put_char(0); /* false */
223 }
224 packet_send();
225 packet_write_wait();
226
227 DH_free(dh);
228
229 kex_derive_keys(kex, hash, shared_secret);
230 BN_clear_free(shared_secret);
231 kex_finish(kex);
232 }
233
234 static void
235 kex_gss_send_error(Gssctxt *ctxt) {
236 char *errstr;
237 OM_uint32 maj, min;
238
239 errstr = ssh_gssapi_last_error(ctxt, &maj, &min);
240 if (errstr) {
241 packet_start(SSH2_MSG_KEXGSS_ERROR);
242 packet_put_int(maj);
243 packet_put_int(min);
244 packet_put_cstring(errstr);
245 packet_put_cstring("");
246 packet_send();
247 packet_write_wait();
248 /* XXX - We should probably log the error locally here */
249 xfree(errstr);
250 }
251 }
252 #endif /* GSSAPI */