[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;
	unsigned int klen, kout;
	unsigned 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;
	u_int slen;
	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) {
		hash = kexgex_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,
		    min, nbits, max,
		    dh->p, dh->g,
		    dh_client_pub,
		    dh->pub_key,
		    shared_secret
		);
	}
	else {	
		/* The GSSAPI hash is identical to the Diffie Helman one */
		hash = 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
		);
	}
	BN_free(dh_client_pub);

	if (kex->session_id == NULL) {
		kex->session_id_len = 20;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	gssbuf.value = hash;
	gssbuf.length = 20; /* Hashlen appears to always be 20 */

	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, 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
b46fa825	1	/*
fe4ad273	2	* Copyright (c) 2001-2005 Simon Wilkinson. All rights reserved.
b46fa825	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"
23987cb8	42
23987cb8	43	static void kex_gss_send_error(Gssctxt *ctxt);
b46fa825	44
	45	void
	46	kexgss_server(Kex *kex)
	47	{
b46fa825	48	OM_uint32 maj_status, min_status;
b46fa825	49
fe4ad273	50	/*
fe4ad273	51	* Some GSSAPI implementations use the input value of ret_flags (an
e23e524c	52	* output variable) as a means of triggering mechanism specific
e23e524c	53	* features. Initializing it to zero avoids inadvertently
fe4ad273	54	* activating this non-standard behaviour.
fe4ad273	55	*/
b46fa825	56
b46fa825	57	OM_uint32 ret_flags = 0;
fe4ad273	58	gss_buffer_desc gssbuf, recv_tok, msg_tok;
fe4ad273	59	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
b46fa825	60	Gssctxt *ctxt = NULL;
fe4ad273	61	unsigned int klen, kout;
	62	unsigned char kbuf, hash;
	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;
b46fa825	69	u_int slen;
23987cb8	70	gss_OID oid;
b46fa825	71
	72	/* Initialise GSSAPI */
	73
fe4ad273	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
	76	* into life
	77	*/
	78	if (!ssh_gssapi_oid_table_ok())
	79	ssh_gssapi_server_mechanisms();
	80
	81	debug2("%s: Identifying %s", __func__, kex->name);
	82	oid = ssh_gssapi_id_kex(NULL, kex->name, &gex);
	83	if (oid == NULL)
	84	fatal("Unknown gssapi mechanism");
	85
	86	debug2("%s: Acquiring credentials", __func__);
	87
	88	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) {
23987cb8	89	kex_gss_send_error(ctxt);
fe4ad273	90	fatal("Unable to acquire credentials for the server");
	91	}
	92
	93	if (gex) {
	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);
	101	packet_check_eom();
	102	if (max < min \|\| nbits < min \|\| max < nbits)
	103	fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
	104	min, nbits, max);
	105	dh = PRIVSEP(choose_dh(min, nbits, max));
	106	if (dh == NULL)
	107	packet_disconnect("Protocol error: no matching group found");
	108
	109	packet_start(SSH2_MSG_KEXGSS_GROUP);
	110	packet_put_bignum2(dh->p);
	111	packet_put_bignum2(dh->g);
	112	packet_send();
	113
	114	packet_write_wait();
	115
	116	} else {
	117	dh = dh_new_group1();
	118	}
	119	dh_gen_key(dh, kex->we_need * 8);
	120
b46fa825	121	do {
	122	debug("Wait SSH2_MSG_GSSAPI_INIT");
	123	type = packet_read();
	124	switch(type) {
	125	case SSH2_MSG_KEXGSS_INIT:
fe4ad273	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;
	130
	131	if ((dh_client_pub = BN_new()) == NULL)
	132	fatal("dh_client_pub == NULL");
	133
	134	packet_get_bignum2(dh_client_pub);
	135
	136	/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
b46fa825	137	break;
b46fa825	138	case SSH2_MSG_KEXGSS_CONTINUE:
fe4ad273	139	recv_tok.value = packet_get_string(&slen);
fe4ad273	140	recv_tok.length = slen;
b46fa825	141	break;
b46fa825	142	default:
fe4ad273	143	packet_disconnect(
	144	"Protocol error: didn't expect packet type %d",
	145	type);
b46fa825	146	}
b46fa825	147
fe4ad273	148	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
	149	&send_tok, &ret_flags));
	150
	151	xfree(recv_tok.value);
	152
	153	if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
	154	fatal("Zero length token output when incomplete");
	155
e23e524c	156	if (dh_client_pub == NULL)
	157	fatal("No client public key");
	158
c045675e	159	if (maj_status & GSS_S_CONTINUE_NEEDED) {
b46fa825	160	debug("Sending GSSAPI_CONTINUE");
b46fa825	161	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
fe4ad273	162	packet_put_string(send_tok.value, send_tok.length);
b46fa825	163	packet_send();
b46fa825	164	gss_release_buffer(&min_status, &send_tok);
	165	}
	166	} while (maj_status & GSS_S_CONTINUE_NEEDED);
	167
	168	if (GSS_ERROR(maj_status)) {
23987cb8	169	kex_gss_send_error(ctxt);
fe4ad273	170	if (send_tok.length > 0) {
e23e524c	171	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
fe4ad273	172	packet_put_string(send_tok.value, send_tok.length);
e23e524c	173	packet_send();
fe4ad273	174	}
fe4ad273	175	packet_disconnect("GSSAPI Key Exchange handshake failed");
b46fa825	176	}
fe4ad273	177
23987cb8	178	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
fe4ad273	179	fatal("Mutual Authentication flag wasn't set");
fe4ad273	180
23987cb8	181	if (!(ret_flags & GSS_C_INTEG_FLAG))
fe4ad273	182	fatal("Integrity flag wasn't set");
b46fa825	183
fe4ad273	184	if (!dh_pub_is_valid(dh, dh_client_pub))
fe4ad273	185	packet_disconnect("bad client public DH value");
b46fa825	186
fe4ad273	187	klen = DH_size(dh);
	188	kbuf = xmalloc(klen);
	189	kout = DH_compute_key(kbuf, dh_client_pub, dh);
b46fa825	190
	191	shared_secret = BN_new();
	192	BN_bin2bn(kbuf, kout, shared_secret);
	193	memset(kbuf, 0, klen);
	194	xfree(kbuf);
fe4ad273	195
	196	if (gex) {
	197	hash = kexgex_hash(
	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,
	206	shared_secret
	207	);
	208	}
	209	else {
	210	/* The GSSAPI hash is identical to the Diffie Helman one */
	211	hash = kex_dh_hash(
	212	kex->client_version_string, kex->server_version_string,
	213	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	214	buffer_ptr(&kex->my), buffer_len(&kex->my),
	215	NULL, 0, /* Change this if we start sending host keys */
	216	dh_client_pub, dh->pub_key, shared_secret
	217	);
	218	}
b46fa825	219	BN_free(dh_client_pub);
fe4ad273	220
b46fa825	221	if (kex->session_id == NULL) {
	222	kex->session_id_len = 20;
	223	kex->session_id = xmalloc(kex->session_id_len);
	224	memcpy(kex->session_id, hash, kex->session_id_len);
	225	}
fe4ad273	226
b46fa825	227	gssbuf.value = hash;
b46fa825	228	gssbuf.length = 20; /* Hashlen appears to always be 20 */
fe4ad273	229
fe4ad273	230	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
23987cb8	231	fatal("Couldn't get MIC");
fe4ad273	232
b46fa825	233	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
	234	packet_put_bignum2(dh->pub_key);
	235	packet_put_string((char *)msg_tok.value,msg_tok.length);
	236
fe4ad273	237	if (send_tok.length != 0) {
b46fa825	238	packet_put_char(1); /* true */
fe4ad273	239	packet_put_string((char *)send_tok.value, send_tok.length);
b46fa825	240	} else {
	241	packet_put_char(0); /* false */
	242	}
fe4ad273	243	packet_send();
	244
	245	gss_release_buffer(&min_status, &send_tok);
	246	gss_release_buffer(&min_status, &msg_tok);
	247
	248	if (gss_kex_context == NULL)
	249	gss_kex_context = ctxt;
	250	else
	251	ssh_gssapi_delete_ctx(&ctxt);
	252
b46fa825	253	DH_free(dh);
	254
	255	kex_derive_keys(kex, hash, shared_secret);
	256	BN_clear_free(shared_secret);
	257	kex_finish(kex);
	258	}
	259
23987cb8	260	static void
	261	kex_gss_send_error(Gssctxt *ctxt) {
	262	char *errstr;
	263	OM_uint32 maj,min;
	264
	265	errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
	266	if (errstr) {
	267	packet_start(SSH2_MSG_KEXGSS_ERROR);
	268	packet_put_int(maj);
	269	packet_put_int(min);
	270	packet_put_cstring(errstr);
	271	packet_put_cstring("");
	272	packet_send();
	273	packet_write_wait();
	274	/* XXX - We should probably log the error locally here */
	275	xfree(errstr);
	276	}
	277	}
b46fa825	278	#endif /* GSSAPI */