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"
46 static void kex_gss_send_error(Gssctxt *ctxt);
49 kexgss_server(Kex *kex)
51 OM_uint32 maj_status, min_status;
54 * Some GSSAPI implementations use the input value of ret_flags (an
55 * output variable) as a means of triggering mechanism specific
56 * features. Initializing it to zero avoids inadvertently
57 * activating this non-standard behaviour.
60 OM_uint32 ret_flags = 0;
61 gss_buffer_desc gssbuf, recv_tok, msg_tok;
62 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
64 u_int slen, klen, kout, hashlen;
67 int min = -1, max = -1, nbits = -1;
68 BIGNUM *shared_secret = NULL;
69 BIGNUM *dh_client_pub = NULL;
73 /* Initialise GSSAPI */
75 /* If we're rekeying, privsep means that some of the private structures
76 * in the GSSAPI code are no longer available. This kludges them back
79 if (!ssh_gssapi_oid_table_ok())
80 ssh_gssapi_server_mechanisms();
82 debug2("%s: Identifying %s", __func__, kex->name);
83 oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
84 if (oid == GSS_C_NO_OID)
85 fatal("Unknown gssapi mechanism");
87 debug2("%s: Acquiring credentials", __func__);
89 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) {
90 kex_gss_send_error(ctxt);
91 fatal("Unable to acquire credentials for the server");
94 switch (kex->kex_type) {
95 case KEX_GSS_GRP1_SHA1:
98 case KEX_GSS_GRP14_SHA1:
99 dh = dh_new_group14();
101 case KEX_GSS_GEX_SHA1:
102 debug("Doing group exchange");
103 packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
104 min = packet_get_int();
105 nbits = packet_get_int();
106 max = packet_get_int();
107 min = MAX(DH_GRP_MIN, min);
108 max = MIN(DH_GRP_MAX, max);
110 if (max < min || nbits < min || max < nbits)
111 fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
113 dh = PRIVSEP(choose_dh(min, nbits, max));
115 packet_disconnect("Protocol error: no matching group found");
117 packet_start(SSH2_MSG_KEXGSS_GROUP);
118 packet_put_bignum2(dh->p);
119 packet_put_bignum2(dh->g);
125 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
128 dh_gen_key(dh, kex->we_need * 8);
131 debug("Wait SSH2_MSG_GSSAPI_INIT");
132 type = packet_read();
134 case SSH2_MSG_KEXGSS_INIT:
135 if (dh_client_pub != NULL)
136 fatal("Received KEXGSS_INIT after initialising");
137 recv_tok.value = packet_get_string(&slen);
138 recv_tok.length = slen;
140 if ((dh_client_pub = BN_new()) == NULL)
141 fatal("dh_client_pub == NULL");
143 packet_get_bignum2(dh_client_pub);
145 /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
147 case SSH2_MSG_KEXGSS_CONTINUE:
148 recv_tok.value = packet_get_string(&slen);
149 recv_tok.length = slen;
153 "Protocol error: didn't expect packet type %d",
157 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
158 &send_tok, &ret_flags));
160 xfree(recv_tok.value);
162 if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
163 fatal("Zero length token output when incomplete");
165 if (dh_client_pub == NULL)
166 fatal("No client public key");
168 if (maj_status & GSS_S_CONTINUE_NEEDED) {
169 debug("Sending GSSAPI_CONTINUE");
170 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
171 packet_put_string(send_tok.value, send_tok.length);
173 gss_release_buffer(&min_status, &send_tok);
175 } while (maj_status & GSS_S_CONTINUE_NEEDED);
177 if (GSS_ERROR(maj_status)) {
178 kex_gss_send_error(ctxt);
179 if (send_tok.length > 0) {
180 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
181 packet_put_string(send_tok.value, send_tok.length);
184 packet_disconnect("GSSAPI Key Exchange handshake failed");
187 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
188 fatal("Mutual Authentication flag wasn't set");
190 if (!(ret_flags & GSS_C_INTEG_FLAG))
191 fatal("Integrity flag wasn't set");
193 if (!dh_pub_is_valid(dh, dh_client_pub))
194 packet_disconnect("bad client public DH value");
197 kbuf = xmalloc(klen);
198 kout = DH_compute_key(kbuf, dh_client_pub, dh);
200 shared_secret = BN_new();
201 BN_bin2bn(kbuf, kout, shared_secret);
202 memset(kbuf, 0, klen);
205 switch (kex->kex_type) {
206 case KEX_GSS_GRP1_SHA1:
207 case KEX_GSS_GRP14_SHA1:
209 kex->client_version_string, kex->server_version_string,
210 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
211 buffer_ptr(&kex->my), buffer_len(&kex->my),
212 NULL, 0, /* Change this if we start sending host keys */
213 dh_client_pub, dh->pub_key, shared_secret,
217 case KEX_GSS_GEX_SHA1:
220 kex->client_version_string, kex->server_version_string,
221 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
222 buffer_ptr(&kex->my), buffer_len(&kex->my),
233 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
236 BN_free(dh_client_pub);
238 if (kex->session_id == NULL) {
239 kex->session_id_len = hashlen;
240 kex->session_id = xmalloc(kex->session_id_len);
241 memcpy(kex->session_id, hash, kex->session_id_len);
245 gssbuf.length = hashlen;
247 if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
248 fatal("Couldn't get MIC");
250 packet_start(SSH2_MSG_KEXGSS_COMPLETE);
251 packet_put_bignum2(dh->pub_key);
252 packet_put_string((char *)msg_tok.value,msg_tok.length);
254 if (send_tok.length != 0) {
255 packet_put_char(1); /* true */
256 packet_put_string((char *)send_tok.value, send_tok.length);
258 packet_put_char(0); /* false */
262 gss_release_buffer(&min_status, &send_tok);
263 gss_release_buffer(&min_status, &msg_tok);
265 if (gss_kex_context == NULL)
266 gss_kex_context = ctxt;
268 ssh_gssapi_delete_ctx(&ctxt);
272 kex_derive_keys(kex, hash, hashlen, shared_secret);
273 BN_clear_free(shared_secret);
278 kex_gss_send_error(Gssctxt *ctxt) {
282 errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
284 packet_start(SSH2_MSG_KEXGSS_ERROR);
287 packet_put_cstring(errstr);
288 packet_put_cstring("");
291 /* XXX - We should probably log the error locally here */