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1/*
2 * Copyright (c) 2001-2004 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 <openssl/crypto.h>
30#include <openssl/bn.h>
31
32#include "xmalloc.h"
33#include "buffer.h"
34#include "bufaux.h"
35#include "kex.h"
36#include "log.h"
37#include "packet.h"
38#include "dh.h"
39#include "canohost.h"
40#include "ssh2.h"
41#include "ssh-gss.h"
42
43void
44kexgss_client(Kex *kex) {
45 gss_buffer_desc gssbuf, send_tok, recv_tok, msg_tok, *token_ptr;
46 Gssctxt *ctxt;
47 OM_uint32 maj_status, min_status, ret_flags;
48 unsigned int klen, kout;
49 DH *dh;
50 BIGNUM *dh_server_pub = 0;
51 BIGNUM *shared_secret = 0;
52 unsigned char *kbuf;
53 unsigned char *hash;
54 unsigned char *serverhostkey;
55 char *msg;
56 char *lang;
57 int type = 0;
58 int first = 1;
59 int slen = 0;
60 u_int strlen;
61
62 ssh_gssapi_build_ctx(&ctxt);
63 if (ssh_gssapi_id_kex(ctxt,kex->name) == NULL)
64 fatal("Couldn't identify host exchange");
65
66 if (ssh_gssapi_import_name(ctxt,get_canonical_hostname(1)))
67 fatal("Couldn't import hostname ");
68
69 /* This code should match that in ssh_dh1_client */
70
71 /* Step 1 - e is dh->pub_key */
72 dh = dh_new_group1();
73 dh_gen_key(dh, kex->we_need * 8);
74
75 /* This is f, we initialise it now to make life easier */
76 dh_server_pub = BN_new();
77 if (dh_server_pub == NULL)
78 fatal("dh_server_pub == NULL");
79
80 token_ptr = GSS_C_NO_BUFFER;
81
82 do {
83 debug("Calling gss_init_sec_context");
84
85 maj_status = ssh_gssapi_init_ctx(ctxt,
86 kex->gss_deleg_creds, token_ptr, &send_tok,
87 &ret_flags);
88
89 if (GSS_ERROR(maj_status)) {
90 if (send_tok.length != 0) {
91 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
92 packet_put_string(send_tok.value,
93 send_tok.length);
94 }
95 fatal("gss_init_context failed");
96 }
97
98 /* If we've got an old receive buffer get rid of it */
99 if (token_ptr != GSS_C_NO_BUFFER)
100 (void) gss_release_buffer(&min_status, &recv_tok);
101
102 if (maj_status == GSS_S_COMPLETE) {
103 /* If mutual state flag is not true, kex fails */
104 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
105 fatal("Mutual authentication failed");
106
107 /* If integ avail flag is not true kex fails */
108 if (!(ret_flags & GSS_C_INTEG_FLAG))
109 fatal("Integrity check failed");
110 }
111
112 /*
113 * If we have data to send, then the last message that we
114 * received cannot have been a 'complete'.
115 */
116 if (send_tok.length != 0) {
117 if (first) {
118 packet_start(SSH2_MSG_KEXGSS_INIT);
119 packet_put_string(send_tok.value,
120 send_tok.length);
121 packet_put_bignum2(dh->pub_key);
122 first = 0;
123 } else {
124 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
125 packet_put_string(send_tok.value,
126 send_tok.length);
127 }
128 packet_send();
129
130 /* If we've sent them data, they should reply */
131
132 type = packet_read();
133 switch (type) {
134 case SSH2_MSG_KEXGSS_HOSTKEY:
135 debug("Received KEXGSS_HOSTKEY");
136 serverhostkey = packet_get_string(&slen);
137 break;
138 case SSH2_MSG_KEXGSS_CONTINUE:
139 debug("Received GSSAPI_CONTINUE");
140 if (maj_status == GSS_S_COMPLETE)
141 fatal("GSSAPI Continue received from server when complete");
142 recv_tok.value = packet_get_string(&strlen);
143 recv_tok.length = strlen;
144 break;
145 case SSH2_MSG_KEXGSS_COMPLETE:
146 debug("Received GSSAPI_COMPLETE");
147 packet_get_bignum2(dh_server_pub);
148 msg_tok.value = packet_get_string(&strlen);
149 msg_tok.length = strlen;
150
151 /* Is there a token included? */
152 if (packet_get_char()) {
153 recv_tok.value=
154 packet_get_string(&strlen);
155 recv_tok.length = strlen;
156 /* If we're already complete - protocol error */
157 if (maj_status == GSS_S_COMPLETE)
158 packet_disconnect("Protocol error: received token when complete");
159 } else {
160 /* No token included */
161 if (maj_status != GSS_S_COMPLETE)
162 packet_disconnect("Protocol error: did not receive final token");
163 }
164 break;
165 case SSH2_MSG_KEXGSS_ERROR:
166 debug("Received Error");
167 maj_status = packet_get_int();
168 min_status = packet_get_int();
169 msg = packet_get_string(NULL);
170 lang = packet_get_string(NULL);
171 fprintf(stderr,"GSSAPI Error: \n%s",msg);
172 default:
173 packet_disconnect("Protocol error: didn't expect packet type %d",
174 type);
175 }
176 token_ptr = &recv_tok;
177 } else {
178 /* No data, and not complete */
179 if (maj_status != GSS_S_COMPLETE)
180 fatal("Not complete, and no token output");
181 }
182 } while (maj_status & GSS_S_CONTINUE_NEEDED);
183
184 /*
185 * We _must_ have received a COMPLETE message in reply from the
186 * server, which will have set dh_server_pub and msg_tok
187 */
188
189 if (type!=SSH2_MSG_KEXGSS_COMPLETE)
190 fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
191
192 /* Check f in range [1, p-1] */
193 if (!dh_pub_is_valid(dh, dh_server_pub))
194 packet_disconnect("bad server public DH value");
195
196 /* compute K=f^x mod p */
197 klen = DH_size(dh);
198 kbuf = xmalloc(klen);
199 kout = DH_compute_key(kbuf, dh_server_pub, dh);
200
201 shared_secret = BN_new();
202 BN_bin2bn(kbuf,kout, shared_secret);
203 memset(kbuf, 0, klen);
204 xfree(kbuf);
205
206 /* The GSS hash is identical to the DH one */
207 hash = kex_dh_hash( kex->client_version_string,
208 kex->server_version_string,
209 buffer_ptr(&kex->my), buffer_len(&kex->my),
210 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
211 serverhostkey, slen, /* server host key */
212 dh->pub_key, /* e */
213 dh_server_pub, /* f */
214 shared_secret /* K */
215 );
216
217 gssbuf.value = hash;
218 gssbuf.length = 20;
219
220 /* Verify that the hash matches the MIC we just got. */
221 if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
222 packet_disconnect("Hash's MIC didn't verify");
223
224 DH_free(dh);
225 /* save session id */
226 if (kex->session_id == NULL) {
227 kex->session_id_len = 20;
228 kex->session_id = xmalloc(kex->session_id_len);
229 memcpy(kex->session_id, hash, kex->session_id_len);
230 }
231
232 if (gss_kex_context == NULL)
233 gss_kex_context = ctxt;
234 else
235 ssh_gssapi_delete_ctx(&ctxt);
236
237 kex_derive_keys(kex, hash, shared_secret);
238 BN_clear_free(shared_secret);
239 kex_finish(kex);
240}
241
242#endif /* GSSAPI */