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

/*
 * Copyright (c) 2001-2005 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 <openssl/crypto.h>
#include <openssl/bn.h>

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

static void kex_gss_send_error(Gssctxt *ctxt);

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;
	int gex;
	gss_OID oid;
	
	/* 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()) 
		ssh_gssapi_server_mechanisms();

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

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

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

	if (gex) {
		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();
		
	} else {
        	dh = dh_new_group1();
	}
	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)) {
		kex_gss_send_error(ctxt);
		if (send_tok.length > 0) {
			packet_start(SSH2_MSG_KEXGSS_CONTINUE);
			packet_put_string(send_tok.value, send_tok.length);
			packet_send();
		}
		packet_disconnect("GSSAPI Key Exchange handshake failed");
	}

	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);

	shared_secret = BN_new();
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	if (gex) {
		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
		);
	}
	else {	
		/* The GSSAPI hash is identical to the Diffie Helman one */
		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
		);
	}
	BN_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((char *)msg_tok.value,msg_tok.length);

	if (send_tok.length != 0) {
		packet_put_char(1); /* true */
		packet_put_string((char *)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);
}

static void 
kex_gss_send_error(Gssctxt *ctxt) {
	char *errstr;
	OM_uint32 maj,min;
		
	errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
	if (errstr) {
		packet_start(SSH2_MSG_KEXGSS_ERROR);
		packet_put_int(maj);
		packet_put_int(min);
		packet_put_cstring(errstr);
		packet_put_cstring("");
		packet_send();
		packet_write_wait();
		/* XXX - We should probably log the error locally here */
		xfree(errstr);
	}
}
#endif /* GSSAPI */
Commit	Line	Data
1c14df9e	1	/*
34fee935	2	* Copyright (c) 2001-2005 Simon Wilkinson. All rights reserved.
1c14df9e	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 "ssh2.h"
	40	#include "ssh-gss.h"
	41	#include "monitor_wrap.h"
88928908	42
88928908	43	static void kex_gss_send_error(Gssctxt *ctxt);
1c14df9e	44
	45	void
	46	kexgss_server(Kex *kex)
	47	{
1c14df9e	48	OM_uint32 maj_status, min_status;
1c14df9e	49
34fee935	50	/*
34fee935	51	* Some GSSAPI implementations use the input value of ret_flags (an
1c14df9e	52	* output variable) as a means of triggering mechanism specific
1c14df9e	53	* features. Initializing it to zero avoids inadvertently
34fee935	54	* activating this non-standard behaviour.
34fee935	55	*/
1c14df9e	56
1c14df9e	57	OM_uint32 ret_flags = 0;
34fee935	58	gss_buffer_desc gssbuf, recv_tok, msg_tok;
34fee935	59	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
1c14df9e	60	Gssctxt *ctxt = NULL;
e00da40d	61	u_int slen, klen, kout, hashlen;
e00da40d	62	u_char kbuf, hash;
34fee935	63	DH *dh;
	64	int min = -1, max = -1, nbits = -1;
	65	BIGNUM *shared_secret = NULL;
	66	BIGNUM *dh_client_pub = NULL;
	67	int type = 0;
	68	int gex;
88928908	69	gss_OID oid;
1c14df9e	70
	71	/* Initialise GSSAPI */
	72
34fee935	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
	75	* into life
	76	*/
	77	if (!ssh_gssapi_oid_table_ok())
	78	ssh_gssapi_server_mechanisms();
	79
	80	debug2("%s: Identifying %s", __func__, kex->name);
	81	oid = ssh_gssapi_id_kex(NULL, kex->name, &gex);
	82	if (oid == NULL)
	83	fatal("Unknown gssapi mechanism");
	84
	85	debug2("%s: Acquiring credentials", __func__);
	86
	87	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) {
88928908	88	kex_gss_send_error(ctxt);
34fee935	89	fatal("Unable to acquire credentials for the server");
	90	}
	91
	92	if (gex) {
	93	debug("Doing group exchange");
	94	packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
	95	min = packet_get_int();
	96	nbits = packet_get_int();
	97	max = packet_get_int();
	98	min = MAX(DH_GRP_MIN, min);
	99	max = MIN(DH_GRP_MAX, max);
	100	packet_check_eom();
	101	if (max < min \|\| nbits < min \|\| max < nbits)
	102	fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
	103	min, nbits, max);
	104	dh = PRIVSEP(choose_dh(min, nbits, max));
	105	if (dh == NULL)
	106	packet_disconnect("Protocol error: no matching group found");
	107
	108	packet_start(SSH2_MSG_KEXGSS_GROUP);
	109	packet_put_bignum2(dh->p);
	110	packet_put_bignum2(dh->g);
	111	packet_send();
	112
	113	packet_write_wait();
	114
	115	} else {
	116	dh = dh_new_group1();
	117	}
	118	dh_gen_key(dh, kex->we_need * 8);
	119
1c14df9e	120	do {
	121	debug("Wait SSH2_MSG_GSSAPI_INIT");
	122	type = packet_read();
	123	switch(type) {
	124	case SSH2_MSG_KEXGSS_INIT:
34fee935	125	if (dh_client_pub != NULL)
	126	fatal("Received KEXGSS_INIT after initialising");
	127	recv_tok.value = packet_get_string(&slen);
	128	recv_tok.length = slen;
	129
	130	if ((dh_client_pub = BN_new()) == NULL)
	131	fatal("dh_client_pub == NULL");
	132
	133	packet_get_bignum2(dh_client_pub);
	134
	135	/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
1c14df9e	136	break;
1c14df9e	137	case SSH2_MSG_KEXGSS_CONTINUE:
34fee935	138	recv_tok.value = packet_get_string(&slen);
34fee935	139	recv_tok.length = slen;
1c14df9e	140	break;
1c14df9e	141	default:
34fee935	142	packet_disconnect(
	143	"Protocol error: didn't expect packet type %d",
	144	type);
1c14df9e	145	}
1c14df9e	146
34fee935	147	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
	148	&send_tok, &ret_flags));
	149
	150	xfree(recv_tok.value);
	151
	152	if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
88928908	153	fatal("Zero length token output when incomplete");
88928908	154
	155	if (dh_client_pub == NULL)
	156	fatal("No client public key");
1c14df9e	157
	158	if (maj_status & GSS_S_CONTINUE_NEEDED) {
	159	debug("Sending GSSAPI_CONTINUE");
	160	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
34fee935	161	packet_put_string(send_tok.value, send_tok.length);
1c14df9e	162	packet_send();
1c14df9e	163	gss_release_buffer(&min_status, &send_tok);
	164	}
	165	} while (maj_status & GSS_S_CONTINUE_NEEDED);
	166
	167	if (GSS_ERROR(maj_status)) {
88928908	168	kex_gss_send_error(ctxt);
34fee935	169	if (send_tok.length > 0) {
88928908	170	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
34fee935	171	packet_put_string(send_tok.value, send_tok.length);
88928908	172	packet_send();
34fee935	173	}
34fee935	174	packet_disconnect("GSSAPI Key Exchange handshake failed");
1c14df9e	175	}
34fee935	176
88928908	177	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
34fee935	178	fatal("Mutual Authentication flag wasn't set");
34fee935	179
88928908	180	if (!(ret_flags & GSS_C_INTEG_FLAG))
34fee935	181	fatal("Integrity flag wasn't set");
1c14df9e	182
34fee935	183	if (!dh_pub_is_valid(dh, dh_client_pub))
34fee935	184	packet_disconnect("bad client public DH value");
1c14df9e	185
34fee935	186	klen = DH_size(dh);
	187	kbuf = xmalloc(klen);
	188	kout = DH_compute_key(kbuf, dh_client_pub, dh);
1c14df9e	189
	190	shared_secret = BN_new();
	191	BN_bin2bn(kbuf, kout, shared_secret);
	192	memset(kbuf, 0, klen);
	193	xfree(kbuf);
34fee935	194
34fee935	195	if (gex) {
e00da40d	196	kexgex_hash(
e00da40d	197	kex->evp_md,
34fee935	198	kex->client_version_string, kex->server_version_string,
	199	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	200	buffer_ptr(&kex->my), buffer_len(&kex->my),
	201	NULL, 0,
	202	min, nbits, max,
	203	dh->p, dh->g,
	204	dh_client_pub,
	205	dh->pub_key,
e00da40d	206	shared_secret,
e00da40d	207	&hash, &hashlen
34fee935	208	);
	209	}
	210	else {
	211	/* The GSSAPI hash is identical to the Diffie Helman one */
e00da40d	212	kex_dh_hash(
34fee935	213	kex->client_version_string, kex->server_version_string,
	214	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	215	buffer_ptr(&kex->my), buffer_len(&kex->my),
	216	NULL, 0, /* Change this if we start sending host keys */
e00da40d	217	dh_client_pub, dh->pub_key, shared_secret,
e00da40d	218	&hash, &hashlen
34fee935	219	);
34fee935	220	}
1c14df9e	221	BN_free(dh_client_pub);
34fee935	222
1c14df9e	223	if (kex->session_id == NULL) {
e00da40d	224	kex->session_id_len = hashlen;
1c14df9e	225	kex->session_id = xmalloc(kex->session_id_len);
	226	memcpy(kex->session_id, hash, kex->session_id_len);
	227	}
34fee935	228
1c14df9e	229	gssbuf.value = hash;
e00da40d	230	gssbuf.length = hashlen;
34fee935	231
34fee935	232	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
88928908	233	fatal("Couldn't get MIC");
34fee935	234
1c14df9e	235	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
	236	packet_put_bignum2(dh->pub_key);
	237	packet_put_string((char *)msg_tok.value,msg_tok.length);
	238
34fee935	239	if (send_tok.length != 0) {
1c14df9e	240	packet_put_char(1); /* true */
34fee935	241	packet_put_string((char *)send_tok.value, send_tok.length);
1c14df9e	242	} else {
	243	packet_put_char(0); /* false */
	244	}
34fee935	245	packet_send();
	246
	247	gss_release_buffer(&min_status, &send_tok);
	248	gss_release_buffer(&min_status, &msg_tok);
	249
	250	if (gss_kex_context == NULL)
	251	gss_kex_context = ctxt;
	252	else
	253	ssh_gssapi_delete_ctx(&ctxt);
	254
1c14df9e	255	DH_free(dh);
1c14df9e	256
e00da40d	257	kex_derive_keys(kex, hash, hashlen, shared_secret);
1c14df9e	258	BN_clear_free(shared_secret);
	259	kex_finish(kex);
	260	}
	261
88928908	262	static void
	263	kex_gss_send_error(Gssctxt *ctxt) {
	264	char *errstr;
	265	OM_uint32 maj,min;
	266
	267	errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
	268	if (errstr) {
	269	packet_start(SSH2_MSG_KEXGSS_ERROR);
	270	packet_put_int(maj);
	271	packet_put_int(min);
	272	packet_put_cstring(errstr);
	273	packet_put_cstring("");
	274	packet_send();
	275	packet_write_wait();
	276	/* XXX - We should probably log the error locally here */
	277	xfree(errstr);
	278	}
	279	}
1c14df9e	280	#endif /* GSSAPI */