2 * Copyright (c) 2001-2005 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.
29 #include <openssl/crypto.h>
30 #include <openssl/bn.h>
41 #include "monitor_wrap.h"
43 static void kex_gss_send_error(Gssctxt *ctxt);
46 kexgss_server(Kex *kex)
48 OM_uint32 maj_status, min_status;
51 * Some GSSAPI implementations use the input value of ret_flags (an
52 * output variable) as a means of triggering mechanism specific
53 * features. Initializing it to zero avoids inadvertently
54 * activating this non-standard behaviour.
57 OM_uint32 ret_flags = 0;
58 gss_buffer_desc gssbuf, recv_tok, msg_tok;
59 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
61 unsigned int klen, kout, hashlen;
62 unsigned char *kbuf, *hash;
64 int min = -1, max = -1, nbits = -1;
65 BIGNUM *shared_secret = NULL;
66 BIGNUM *dh_client_pub = NULL;
72 /* Initialise GSSAPI */
74 /* If we're rekeying, privsep means that some of the private structures
75 * in the GSSAPI code are no longer available. This kludges them back
78 if (!ssh_gssapi_oid_table_ok())
79 ssh_gssapi_server_mechanisms();
81 debug2("%s: Identifying %s", __func__, kex->name);
82 oid = ssh_gssapi_id_kex(NULL, kex->name, &gex);
84 fatal("Unknown gssapi mechanism");
86 debug2("%s: Acquiring credentials", __func__);
88 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) {
89 kex_gss_send_error(ctxt);
90 fatal("Unable to acquire credentials for the server");
94 debug("Doing group exchange");
95 packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
96 min = packet_get_int();
97 nbits = packet_get_int();
98 max = packet_get_int();
99 min = MAX(DH_GRP_MIN, min);
100 max = MIN(DH_GRP_MAX, max);
102 if (max < min || nbits < min || max < nbits)
103 fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
105 dh = PRIVSEP(choose_dh(min, nbits, max));
107 packet_disconnect("Protocol error: no matching group found");
109 packet_start(SSH2_MSG_KEXGSS_GROUP);
110 packet_put_bignum2(dh->p);
111 packet_put_bignum2(dh->g);
117 dh = dh_new_group1();
119 dh_gen_key(dh, kex->we_need * 8);
122 debug("Wait SSH2_MSG_GSSAPI_INIT");
123 type = packet_read();
125 case SSH2_MSG_KEXGSS_INIT:
126 if (dh_client_pub != NULL)
127 fatal("Received KEXGSS_INIT after initialising");
128 recv_tok.value = packet_get_string(&slen);
129 recv_tok.length = slen;
131 if ((dh_client_pub = BN_new()) == NULL)
132 fatal("dh_client_pub == NULL");
134 packet_get_bignum2(dh_client_pub);
136 /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
138 case SSH2_MSG_KEXGSS_CONTINUE:
139 recv_tok.value = packet_get_string(&slen);
140 recv_tok.length = slen;
144 "Protocol error: didn't expect packet type %d",
148 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
149 &send_tok, &ret_flags));
151 xfree(recv_tok.value);
153 if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
154 fatal("Zero length token output when incomplete");
156 if (dh_client_pub == NULL)
157 fatal("No client public key");
159 if (maj_status & GSS_S_CONTINUE_NEEDED) {
160 debug("Sending GSSAPI_CONTINUE");
161 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
162 packet_put_string(send_tok.value, send_tok.length);
164 gss_release_buffer(&min_status, &send_tok);
166 } while (maj_status & GSS_S_CONTINUE_NEEDED);
168 if (GSS_ERROR(maj_status)) {
169 kex_gss_send_error(ctxt);
170 if (send_tok.length > 0) {
171 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
172 packet_put_string(send_tok.value, send_tok.length);
175 packet_disconnect("GSSAPI Key Exchange handshake failed");
178 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
179 fatal("Mutual Authentication flag wasn't set");
181 if (!(ret_flags & GSS_C_INTEG_FLAG))
182 fatal("Integrity flag wasn't set");
184 if (!dh_pub_is_valid(dh, dh_client_pub))
185 packet_disconnect("bad client public DH value");
188 kbuf = xmalloc(klen);
189 kout = DH_compute_key(kbuf, dh_client_pub, dh);
191 shared_secret = BN_new();
192 BN_bin2bn(kbuf, kout, shared_secret);
193 memset(kbuf, 0, klen);
199 kex->client_version_string, kex->server_version_string,
200 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
201 buffer_ptr(&kex->my), buffer_len(&kex->my),
212 /* The GSSAPI hash is identical to the Diffie Helman one */
214 kex->client_version_string, kex->server_version_string,
215 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
216 buffer_ptr(&kex->my), buffer_len(&kex->my),
217 NULL, 0, /* Change this if we start sending host keys */
218 dh_client_pub, dh->pub_key, shared_secret,
222 BN_free(dh_client_pub);
224 if (kex->session_id == NULL) {
225 kex->session_id_len = 20;
226 kex->session_id = xmalloc(kex->session_id_len);
227 memcpy(kex->session_id, hash, kex->session_id_len);
231 gssbuf.length = 20; /* Hashlen appears to always be 20 */
233 if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
234 fatal("Couldn't get MIC");
236 packet_start(SSH2_MSG_KEXGSS_COMPLETE);
237 packet_put_bignum2(dh->pub_key);
238 packet_put_string((char *)msg_tok.value,msg_tok.length);
240 if (send_tok.length != 0) {
241 packet_put_char(1); /* true */
242 packet_put_string((char *)send_tok.value, send_tok.length);
244 packet_put_char(0); /* false */
248 gss_release_buffer(&min_status, &send_tok);
249 gss_release_buffer(&min_status, &msg_tok);
251 if (gss_kex_context == NULL)
252 gss_kex_context = ctxt;
254 ssh_gssapi_delete_ctx(&ctxt);
258 kex_derive_keys(kex, hash, hashlen, shared_secret);
259 BN_clear_free(shared_secret);
264 kex_gss_send_error(Gssctxt *ctxt) {
268 errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
270 packet_start(SSH2_MSG_KEXGSS_ERROR);
273 packet_put_cstring(errstr);
274 packet_put_cstring("");
277 /* XXX - We should probably log the error locally here */