[gssapi-openssh.git] / openssh / kexgsss.c

/*
 * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#ifdef GSSAPI

#include <string.h>

#include <openssl/crypto.h>
#include <openssl/bn.h>

#include "xmalloc.h"
#include "buffer.h"
#include "ssh2.h"
#include "key.h"
#include "cipher.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "dh.h"
#include "ssh-gss.h"
#include "monitor_wrap.h"
#include "servconf.h"

extern ServerOptions options;

void
kexgss_server(Kex *kex)
{
	OM_uint32 maj_status, min_status;
	
	/* 
	 * Some GSSAPI implementations use the input value of ret_flags (an
 	 * output variable) as a means of triggering mechanism specific 
 	 * features. Initializing it to zero avoids inadvertently 
 	 * activating this non-standard behaviour.
	 */

	OM_uint32 ret_flags = 0;
	gss_buffer_desc gssbuf, recv_tok, msg_tok;
	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
	Gssctxt *ctxt = NULL;
	u_int slen, klen, kout, hashlen;
	u_char *kbuf, *hash;
	DH *dh;
	int min = -1, max = -1, nbits = -1;
	BIGNUM *shared_secret = NULL;
	BIGNUM *dh_client_pub = NULL;
	int type = 0;
	gss_OID oid;
	char *mechs;

	/* Initialise GSSAPI */

	/* If we're rekeying, privsep means that some of the private structures
	 * in the GSSAPI code are no longer available. This kludges them back
	 * into life
	 */
	if (!ssh_gssapi_oid_table_ok()) 
		if ((mechs = ssh_gssapi_server_mechanisms()))
			xfree(mechs);

	debug2("%s: Identifying %s", __func__, kex->name);
	oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
	if (oid == GSS_C_NO_OID)
	   fatal("Unknown gssapi mechanism");

	debug2("%s: Acquiring credentials", __func__);

	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
		fatal("Unable to acquire credentials for the server");

	switch (kex->kex_type) {
	case KEX_GSS_GRP1_SHA1:
		dh = dh_new_group1();
		break;
	case KEX_GSS_GRP14_SHA1:
		dh = dh_new_group14();
		break;
	case KEX_GSS_GEX_SHA1:
		debug("Doing group exchange");
		packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
		min = packet_get_int();
		nbits = packet_get_int();
		max = packet_get_int();
		min = MAX(DH_GRP_MIN, min);
		max = MIN(DH_GRP_MAX, max);
		packet_check_eom();
		if (max < min || nbits < min || max < nbits)
			fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
			    min, nbits, max);
		dh = PRIVSEP(choose_dh(min, nbits, max));
		if (dh == NULL)
			packet_disconnect("Protocol error: no matching group found");

		packet_start(SSH2_MSG_KEXGSS_GROUP);
		packet_put_bignum2(dh->p);
		packet_put_bignum2(dh->g);
		packet_send();

		packet_write_wait();
		break;
	default:
		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	}

	dh_gen_key(dh, kex->we_need * 8);

	do {
		debug("Wait SSH2_MSG_GSSAPI_INIT");
		type = packet_read();
		switch(type) {
		case SSH2_MSG_KEXGSS_INIT:
			if (dh_client_pub != NULL) 
				fatal("Received KEXGSS_INIT after initialising");
			recv_tok.value = packet_get_string(&slen);
			recv_tok.length = slen; 

			if ((dh_client_pub = BN_new()) == NULL)
				fatal("dh_client_pub == NULL");

			packet_get_bignum2(dh_client_pub);

			/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
			break;
		case SSH2_MSG_KEXGSS_CONTINUE:
			recv_tok.value = packet_get_string(&slen);
			recv_tok.length = slen; 
			break;
		default:
			packet_disconnect(
			    "Protocol error: didn't expect packet type %d",
			    type);
		}

		maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok, 
		    &send_tok, &ret_flags));

		xfree(recv_tok.value);

		if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
			fatal("Zero length token output when incomplete");

		if (dh_client_pub == NULL)
			fatal("No client public key");
		
		if (maj_status & GSS_S_CONTINUE_NEEDED) {
			debug("Sending GSSAPI_CONTINUE");
			packet_start(SSH2_MSG_KEXGSS_CONTINUE);
			packet_put_string(send_tok.value, send_tok.length);
			packet_send();
			gss_release_buffer(&min_status, &send_tok);
		}
	} while (maj_status & GSS_S_CONTINUE_NEEDED);

	if (GSS_ERROR(maj_status)) {
		if (send_tok.length > 0) {
			packet_start(SSH2_MSG_KEXGSS_CONTINUE);
			packet_put_string(send_tok.value, send_tok.length);
			packet_send();
		}
		fatal("accept_ctx died");
	}

	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
		fatal("Mutual Authentication flag wasn't set");

	if (!(ret_flags & GSS_C_INTEG_FLAG))
		fatal("Integrity flag wasn't set");
	
	if (!dh_pub_is_valid(dh, dh_client_pub))
		packet_disconnect("bad client public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen); 
	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	if (kout < 0)
		fatal("DH_compute_key: failed");

	shared_secret = BN_new();
	if (shared_secret == NULL)
		fatal("kexgss_server: BN_new failed");

	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
		fatal("kexgss_server: BN_bin2bn failed");

	memset(kbuf, 0, klen);
	xfree(kbuf);

	switch (kex->kex_type) {
	case KEX_GSS_GRP1_SHA1:
	case KEX_GSS_GRP14_SHA1:
		kex_dh_hash(
		    kex->client_version_string, kex->server_version_string,
		    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
		    buffer_ptr(&kex->my), buffer_len(&kex->my),
		    NULL, 0, /* Change this if we start sending host keys */
		    dh_client_pub, dh->pub_key, shared_secret,
		    &hash, &hashlen
		);
		break;
	case KEX_GSS_GEX_SHA1:
		kexgex_hash(
		    kex->evp_md,
		    kex->client_version_string, kex->server_version_string,
		    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
		    buffer_ptr(&kex->my), buffer_len(&kex->my),
		    NULL, 0,
		    min, nbits, max,
		    dh->p, dh->g,
		    dh_client_pub,
		    dh->pub_key,
		    shared_secret,
		    &hash, &hashlen
		);
		break;
	default:
		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	}

	BN_clear_free(dh_client_pub);

	if (kex->session_id == NULL) {
		kex->session_id_len = hashlen;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	gssbuf.value = hash;
	gssbuf.length = hashlen;

	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
		fatal("Couldn't get MIC");

	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
	packet_put_bignum2(dh->pub_key);
	packet_put_string(msg_tok.value,msg_tok.length);

	if (send_tok.length != 0) {
		packet_put_char(1); /* true */
		packet_put_string(send_tok.value, send_tok.length);
	} else {
		packet_put_char(0); /* false */
	}
	packet_send();

	gss_release_buffer(&min_status, &send_tok);
	gss_release_buffer(&min_status, &msg_tok);

	if (gss_kex_context == NULL)
		gss_kex_context = ctxt;
	else 
		ssh_gssapi_delete_ctx(&ctxt);

	DH_free(dh);

	kex_derive_keys(kex, hash, hashlen, shared_secret);
	BN_clear_free(shared_secret);
	kex_finish(kex);

	/* If this was a rekey, then save out any delegated credentials we
	 * just exchanged.  */
	if (options.gss_store_rekey)
		ssh_gssapi_rekey_creds();
}
#endif /* GSSAPI */
Commit	Line	Data
f97edba6	1	/*
	2	* Copyright (c) 2001-2009 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 <string.h>
	30
	31	#include <openssl/crypto.h>
	32	#include <openssl/bn.h>
	33
	34	#include "xmalloc.h"
	35	#include "buffer.h"
	36	#include "ssh2.h"
	37	#include "key.h"
	38	#include "cipher.h"
	39	#include "kex.h"
	40	#include "log.h"
	41	#include "packet.h"
	42	#include "dh.h"
	43	#include "ssh-gss.h"
	44	#include "monitor_wrap.h"
	45	#include "servconf.h"
	46
	47	extern ServerOptions options;
	48
	49	void
	50	kexgss_server(Kex *kex)
	51	{
	52	OM_uint32 maj_status, min_status;
	53
	54	/*
	55	* Some GSSAPI implementations use the input value of ret_flags (an
	56	* output variable) as a means of triggering mechanism specific
	57	* features. Initializing it to zero avoids inadvertently
	58	* activating this non-standard behaviour.
	59	*/
	60
	61	OM_uint32 ret_flags = 0;
	62	gss_buffer_desc gssbuf, recv_tok, msg_tok;
	63	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
	64	Gssctxt *ctxt = NULL;
65	u_int slen, klen, kout, hashlen;
66	u_char kbuf, hash;
67	DH *dh;
68	int min = -1, max = -1, nbits = -1;
69	BIGNUM *shared_secret = NULL;
70	BIGNUM *dh_client_pub = NULL;
71	int type = 0;
72	gss_OID oid;
73	char *mechs;
74
75	/* Initialise GSSAPI */
76
77	/* If we're rekeying, privsep means that some of the private structures
78	* in the GSSAPI code are no longer available. This kludges them back
79	* into life
80	*/
81	if (!ssh_gssapi_oid_table_ok())
82	if ((mechs = ssh_gssapi_server_mechanisms()))
83	xfree(mechs);
84
85	debug2("%s: Identifying %s", __func__, kex->name);
86	oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
87	if (oid == GSS_C_NO_OID)
88	fatal("Unknown gssapi mechanism");
89
90	debug2("%s: Acquiring credentials", __func__);
91
92	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
93	fatal("Unable to acquire credentials for the server");
94
95	switch (kex->kex_type) {
96	case KEX_GSS_GRP1_SHA1:
97	dh = dh_new_group1();
98	break;
99	case KEX_GSS_GRP14_SHA1:
100	dh = dh_new_group14();
101	break;
102	case KEX_GSS_GEX_SHA1:
103	debug("Doing group exchange");
104	packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
105	min = packet_get_int();
106	nbits = packet_get_int();
107	max = packet_get_int();
108	min = MAX(DH_GRP_MIN, min);
109	max = MIN(DH_GRP_MAX, max);
110	packet_check_eom();
111	if (max < min \|\| nbits < min \|\| max < nbits)
112	fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
113	min, nbits, max);
114	dh = PRIVSEP(choose_dh(min, nbits, max));
115	if (dh == NULL)
116	packet_disconnect("Protocol error: no matching group found");
117
118	packet_start(SSH2_MSG_KEXGSS_GROUP);
119	packet_put_bignum2(dh->p);
120	packet_put_bignum2(dh->g);
121	packet_send();
122
123	packet_write_wait();
124	break;
125	default:
126	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
127	}
128
129	dh_gen_key(dh, kex->we_need * 8);
130
131	do {
132	debug("Wait SSH2_MSG_GSSAPI_INIT");
133	type = packet_read();
134	switch(type) {
135	case SSH2_MSG_KEXGSS_INIT:
136	if (dh_client_pub != NULL)
137	fatal("Received KEXGSS_INIT after initialising");
138	recv_tok.value = packet_get_string(&slen);
139	recv_tok.length = slen;
140
141	if ((dh_client_pub = BN_new()) == NULL)
142	fatal("dh_client_pub == NULL");
143
144	packet_get_bignum2(dh_client_pub);
145
146	/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
147	break;
148	case SSH2_MSG_KEXGSS_CONTINUE:
149	recv_tok.value = packet_get_string(&slen);
150	recv_tok.length = slen;
151	break;
152	default:
153	packet_disconnect(
154	"Protocol error: didn't expect packet type %d",
155	type);
156	}
157
158	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
159	&send_tok, &ret_flags));
160
161	xfree(recv_tok.value);
162
163	if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
164	fatal("Zero length token output when incomplete");
165
166	if (dh_client_pub == NULL)
167	fatal("No client public key");
168
169	if (maj_status & GSS_S_CONTINUE_NEEDED) {
170	debug("Sending GSSAPI_CONTINUE");
171	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
172	packet_put_string(send_tok.value, send_tok.length);
173	packet_send();
174	gss_release_buffer(&min_status, &send_tok);
175	}
176	} while (maj_status & GSS_S_CONTINUE_NEEDED);
177
178	if (GSS_ERROR(maj_status)) {
179	if (send_tok.length > 0) {
180	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
181	packet_put_string(send_tok.value, send_tok.length);
182	packet_send();
183	}
184	fatal("accept_ctx died");
185	}
186
187	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
188	fatal("Mutual Authentication flag wasn't set");
189
190	if (!(ret_flags & GSS_C_INTEG_FLAG))
191	fatal("Integrity flag wasn't set");
192
193	if (!dh_pub_is_valid(dh, dh_client_pub))
194	packet_disconnect("bad client public DH value");
195
196	klen = DH_size(dh);
197	kbuf = xmalloc(klen);
198	kout = DH_compute_key(kbuf, dh_client_pub, dh);
199	if (kout < 0)
200	fatal("DH_compute_key: failed");
201
202	shared_secret = BN_new();
203	if (shared_secret == NULL)
204	fatal("kexgss_server: BN_new failed");
205
206	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
207	fatal("kexgss_server: BN_bin2bn failed");
208
209	memset(kbuf, 0, klen);
210	xfree(kbuf);
211
212	switch (kex->kex_type) {
213	case KEX_GSS_GRP1_SHA1:
214	case KEX_GSS_GRP14_SHA1:
215	kex_dh_hash(
216	kex->client_version_string, kex->server_version_string,
217	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
218	buffer_ptr(&kex->my), buffer_len(&kex->my),
219	NULL, 0, /* Change this if we start sending host keys */
220	dh_client_pub, dh->pub_key, shared_secret,
221	&hash, &hashlen
222	);
223	break;
224	case KEX_GSS_GEX_SHA1:
225	kexgex_hash(
226	kex->evp_md,
227	kex->client_version_string, kex->server_version_string,
228	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
229	buffer_ptr(&kex->my), buffer_len(&kex->my),
230	NULL, 0,
231	min, nbits, max,
232	dh->p, dh->g,
233	dh_client_pub,
234	dh->pub_key,
235	shared_secret,
236	&hash, &hashlen
237	);
238	break;
239	default:
240	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
241	}
242
243	BN_clear_free(dh_client_pub);
244
245	if (kex->session_id == NULL) {
246	kex->session_id_len = hashlen;
247	kex->session_id = xmalloc(kex->session_id_len);
248	memcpy(kex->session_id, hash, kex->session_id_len);
249	}
250
251	gssbuf.value = hash;
252	gssbuf.length = hashlen;
253
254	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
255	fatal("Couldn't get MIC");
256
257	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
258	packet_put_bignum2(dh->pub_key);
259	packet_put_string(msg_tok.value,msg_tok.length);
260
261	if (send_tok.length != 0) {
262	packet_put_char(1); /* true */
263	packet_put_string(send_tok.value, send_tok.length);
264	} else {
265	packet_put_char(0); /* false */
266	}
267	packet_send();
268
269	gss_release_buffer(&min_status, &send_tok);
270	gss_release_buffer(&min_status, &msg_tok);
271
272	if (gss_kex_context == NULL)
273	gss_kex_context = ctxt;
274	else
275	ssh_gssapi_delete_ctx(&ctxt);
276
277	DH_free(dh);
278
279	kex_derive_keys(kex, hash, hashlen, shared_secret);
280	BN_clear_free(shared_secret);
281	kex_finish(kex);
282
283	/* If this was a rekey, then save out any delegated credentials we
284	* just exchanged. */
285	if (options.gss_store_rekey)
286	ssh_gssapi_rekey_creds();
287	}
288	#endif /* GSSAPI */