2 * Copyright (c) 2001-2006 Simon Wilkinson. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
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.
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.
31 #include <openssl/crypto.h>
32 #include <openssl/bn.h>
44 #include "monitor_wrap.h"
47 kexgss_server(Kex *kex)
49 OM_uint32 maj_status, min_status;
52 * Some GSSAPI implementations use the input value of ret_flags (an
53 * output variable) as a means of triggering mechanism specific
54 * features. Initializing it to zero avoids inadvertently
55 * activating this non-standard behaviour.
58 OM_uint32 ret_flags = 0;
59 gss_buffer_desc gssbuf, recv_tok, msg_tok;
60 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
62 u_int slen, klen, kout, hashlen;
65 int min = -1, max = -1, nbits = -1;
66 BIGNUM *shared_secret = NULL;
67 BIGNUM *dh_client_pub = NULL;
71 /* Initialise GSSAPI */
73 /* If we're rekeying, privsep means that some of the private structures
74 * in the GSSAPI code are no longer available. This kludges them back
77 if (!ssh_gssapi_oid_table_ok())
78 ssh_gssapi_server_mechanisms();
80 debug2("%s: Identifying %s", __func__, kex->name);
81 oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
82 if (oid == GSS_C_NO_OID)
83 fatal("Unknown gssapi mechanism");
85 debug2("%s: Acquiring credentials", __func__);
87 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
88 fatal("Unable to acquire credentials for the server");
90 switch (kex->kex_type) {
91 case KEX_GSS_GRP1_SHA1:
94 case KEX_GSS_GRP14_SHA1:
95 dh = dh_new_group14();
97 case KEX_GSS_GEX_SHA1:
98 debug("Doing group exchange");
99 packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
100 min = packet_get_int();
101 nbits = packet_get_int();
102 max = packet_get_int();
103 min = MAX(DH_GRP_MIN, min);
104 max = MIN(DH_GRP_MAX, max);
106 if (max < min || nbits < min || max < nbits)
107 fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
109 dh = PRIVSEP(choose_dh(min, nbits, max));
111 packet_disconnect("Protocol error: no matching group found");
113 packet_start(SSH2_MSG_KEXGSS_GROUP);
114 packet_put_bignum2(dh->p);
115 packet_put_bignum2(dh->g);
121 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
124 dh_gen_key(dh, kex->we_need * 8);
127 debug("Wait SSH2_MSG_GSSAPI_INIT");
128 type = packet_read();
130 case SSH2_MSG_KEXGSS_INIT:
131 if (dh_client_pub != NULL)
132 fatal("Received KEXGSS_INIT after initialising");
133 recv_tok.value = packet_get_string(&slen);
134 recv_tok.length = slen;
136 if ((dh_client_pub = BN_new()) == NULL)
137 fatal("dh_client_pub == NULL");
139 packet_get_bignum2(dh_client_pub);
141 /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
143 case SSH2_MSG_KEXGSS_CONTINUE:
144 recv_tok.value = packet_get_string(&slen);
145 recv_tok.length = slen;
149 "Protocol error: didn't expect packet type %d",
153 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
154 &send_tok, &ret_flags));
156 xfree(recv_tok.value);
158 if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
159 fatal("Zero length token output when incomplete");
161 if (dh_client_pub == NULL)
162 fatal("No client public key");
164 if (maj_status & GSS_S_CONTINUE_NEEDED) {
165 debug("Sending GSSAPI_CONTINUE");
166 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
167 packet_put_string(send_tok.value, send_tok.length);
169 gss_release_buffer(&min_status, &send_tok);
171 } while (maj_status & GSS_S_CONTINUE_NEEDED);
173 if (GSS_ERROR(maj_status)) {
174 if (send_tok.length > 0) {
175 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
176 packet_put_string(send_tok.value, send_tok.length);
179 fatal("accept_ctx died");
182 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
183 fatal("Mutual Authentication flag wasn't set");
185 if (!(ret_flags & GSS_C_INTEG_FLAG))
186 fatal("Integrity flag wasn't set");
188 if (!dh_pub_is_valid(dh, dh_client_pub))
189 packet_disconnect("bad client public DH value");
192 kbuf = xmalloc(klen);
193 kout = DH_compute_key(kbuf, dh_client_pub, dh);
195 shared_secret = BN_new();
196 BN_bin2bn(kbuf, kout, shared_secret);
197 memset(kbuf, 0, klen);
200 switch (kex->kex_type) {
201 case KEX_GSS_GRP1_SHA1:
202 case KEX_GSS_GRP14_SHA1:
204 kex->client_version_string, kex->server_version_string,
205 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
206 buffer_ptr(&kex->my), buffer_len(&kex->my),
207 NULL, 0, /* Change this if we start sending host keys */
208 dh_client_pub, dh->pub_key, shared_secret,
212 case KEX_GSS_GEX_SHA1:
215 kex->client_version_string, kex->server_version_string,
216 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
217 buffer_ptr(&kex->my), buffer_len(&kex->my),
228 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
231 BN_free(dh_client_pub);
233 if (kex->session_id == NULL) {
234 kex->session_id_len = hashlen;
235 kex->session_id = xmalloc(kex->session_id_len);
236 memcpy(kex->session_id, hash, kex->session_id_len);
240 gssbuf.length = hashlen;
242 if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
243 fatal("Couldn't get MIC");
245 packet_start(SSH2_MSG_KEXGSS_COMPLETE);
246 packet_put_bignum2(dh->pub_key);
247 packet_put_string(msg_tok.value,msg_tok.length);
249 if (send_tok.length != 0) {
250 packet_put_char(1); /* true */
251 packet_put_string(send_tok.value, send_tok.length);
253 packet_put_char(0); /* false */
257 gss_release_buffer(&min_status, &send_tok);
258 gss_release_buffer(&min_status, &msg_tok);
260 if (gss_kex_context == NULL)
261 gss_kex_context = ctxt;
263 ssh_gssapi_delete_ctx(&ctxt);
267 kex_derive_keys(kex, hash, hashlen, shared_secret);
268 BN_clear_free(shared_secret);