[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 "cipher.h"
#include "key.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
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"
30460aeb	35	#include "cipher.h"
30460aeb	36	#include "key.h"
b46fa825	37	#include "kex.h"
	38	#include "log.h"
	39	#include "packet.h"
	40	#include "dh.h"
	41	#include "ssh2.h"
	42	#include "ssh-gss.h"
	43	#include "monitor_wrap.h"
23987cb8	44
23987cb8	45	static void kex_gss_send_error(Gssctxt *ctxt);
b46fa825	46
	47	void
	48	kexgss_server(Kex *kex)
	49	{
b46fa825	50	OM_uint32 maj_status, min_status;
b46fa825	51
fe4ad273	52	/*
fe4ad273	53	* Some GSSAPI implementations use the input value of ret_flags (an
e23e524c	54	* output variable) as a means of triggering mechanism specific
e23e524c	55	* features. Initializing it to zero avoids inadvertently
fe4ad273	56	* activating this non-standard behaviour.
fe4ad273	57	*/
b46fa825	58
b46fa825	59	OM_uint32 ret_flags = 0;
fe4ad273	60	gss_buffer_desc gssbuf, recv_tok, msg_tok;
fe4ad273	61	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
b46fa825	62	Gssctxt *ctxt = NULL;
f472818d	63	u_int slen, klen, kout, hashlen;
f472818d	64	u_char kbuf, hash;
fe4ad273	65	DH *dh;
	66	int min = -1, max = -1, nbits = -1;
	67	BIGNUM *shared_secret = NULL;
	68	BIGNUM *dh_client_pub = NULL;
	69	int type = 0;
	70	int gex;
23987cb8	71	gss_OID oid;
b46fa825	72
	73	/* Initialise GSSAPI */
	74
fe4ad273	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
	77	* into life
	78	*/
	79	if (!ssh_gssapi_oid_table_ok())
	80	ssh_gssapi_server_mechanisms();
	81
	82	debug2("%s: Identifying %s", __func__, kex->name);
	83	oid = ssh_gssapi_id_kex(NULL, kex->name, &gex);
	84	if (oid == NULL)
	85	fatal("Unknown gssapi mechanism");
	86
	87	debug2("%s: Acquiring credentials", __func__);
	88
	89	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) {
23987cb8	90	kex_gss_send_error(ctxt);
fe4ad273	91	fatal("Unable to acquire credentials for the server");
	92	}
	93
	94	if (gex) {
	95	debug("Doing group exchange");
	96	packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
	97	min = packet_get_int();
	98	nbits = packet_get_int();
	99	max = packet_get_int();
	100	min = MAX(DH_GRP_MIN, min);
	101	max = MIN(DH_GRP_MAX, max);
	102	packet_check_eom();
	103	if (max < min \|\| nbits < min \|\| max < nbits)
	104	fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
	105	min, nbits, max);
	106	dh = PRIVSEP(choose_dh(min, nbits, max));
	107	if (dh == NULL)
	108	packet_disconnect("Protocol error: no matching group found");
	109
	110	packet_start(SSH2_MSG_KEXGSS_GROUP);
	111	packet_put_bignum2(dh->p);
	112	packet_put_bignum2(dh->g);
	113	packet_send();
	114
	115	packet_write_wait();
	116
	117	} else {
	118	dh = dh_new_group1();
	119	}
	120	dh_gen_key(dh, kex->we_need * 8);
	121
b46fa825	122	do {
	123	debug("Wait SSH2_MSG_GSSAPI_INIT");
	124	type = packet_read();
	125	switch(type) {
	126	case SSH2_MSG_KEXGSS_INIT:
fe4ad273	127	if (dh_client_pub != NULL)
	128	fatal("Received KEXGSS_INIT after initialising");
	129	recv_tok.value = packet_get_string(&slen);
	130	recv_tok.length = slen;
	131
	132	if ((dh_client_pub = BN_new()) == NULL)
	133	fatal("dh_client_pub == NULL");
	134
	135	packet_get_bignum2(dh_client_pub);
	136
	137	/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
b46fa825	138	break;
b46fa825	139	case SSH2_MSG_KEXGSS_CONTINUE:
fe4ad273	140	recv_tok.value = packet_get_string(&slen);
fe4ad273	141	recv_tok.length = slen;
b46fa825	142	break;
b46fa825	143	default:
fe4ad273	144	packet_disconnect(
	145	"Protocol error: didn't expect packet type %d",
	146	type);
b46fa825	147	}
b46fa825	148
fe4ad273	149	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
	150	&send_tok, &ret_flags));
	151
	152	xfree(recv_tok.value);
	153
	154	if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
	155	fatal("Zero length token output when incomplete");
	156
e23e524c	157	if (dh_client_pub == NULL)
	158	fatal("No client public key");
	159
c045675e	160	if (maj_status & GSS_S_CONTINUE_NEEDED) {
b46fa825	161	debug("Sending GSSAPI_CONTINUE");
b46fa825	162	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
fe4ad273	163	packet_put_string(send_tok.value, send_tok.length);
b46fa825	164	packet_send();
b46fa825	165	gss_release_buffer(&min_status, &send_tok);
	166	}
	167	} while (maj_status & GSS_S_CONTINUE_NEEDED);
	168
	169	if (GSS_ERROR(maj_status)) {
23987cb8	170	kex_gss_send_error(ctxt);
fe4ad273	171	if (send_tok.length > 0) {
e23e524c	172	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
fe4ad273	173	packet_put_string(send_tok.value, send_tok.length);
e23e524c	174	packet_send();
fe4ad273	175	}
fe4ad273	176	packet_disconnect("GSSAPI Key Exchange handshake failed");
b46fa825	177	}
fe4ad273	178
23987cb8	179	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
fe4ad273	180	fatal("Mutual Authentication flag wasn't set");
fe4ad273	181
23987cb8	182	if (!(ret_flags & GSS_C_INTEG_FLAG))
fe4ad273	183	fatal("Integrity flag wasn't set");
b46fa825	184
fe4ad273	185	if (!dh_pub_is_valid(dh, dh_client_pub))
fe4ad273	186	packet_disconnect("bad client public DH value");
b46fa825	187
fe4ad273	188	klen = DH_size(dh);
	189	kbuf = xmalloc(klen);
	190	kout = DH_compute_key(kbuf, dh_client_pub, dh);
b46fa825	191
	192	shared_secret = BN_new();
	193	BN_bin2bn(kbuf, kout, shared_secret);
	194	memset(kbuf, 0, klen);
	195	xfree(kbuf);
fe4ad273	196
fe4ad273	197	if (gex) {
08822d99	198	kexgex_hash(
08822d99	199	kex->evp_md,
fe4ad273	200	kex->client_version_string, kex->server_version_string,
	201	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	202	buffer_ptr(&kex->my), buffer_len(&kex->my),
	203	NULL, 0,
	204	min, nbits, max,
	205	dh->p, dh->g,
	206	dh_client_pub,
	207	dh->pub_key,
08822d99	208	shared_secret,
08822d99	209	&hash, &hashlen
fe4ad273	210	);
	211	}
	212	else {
	213	/* The GSSAPI hash is identical to the Diffie Helman one */
08822d99	214	kex_dh_hash(
fe4ad273	215	kex->client_version_string, kex->server_version_string,
	216	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	217	buffer_ptr(&kex->my), buffer_len(&kex->my),
	218	NULL, 0, /* Change this if we start sending host keys */
08822d99	219	dh_client_pub, dh->pub_key, shared_secret,
08822d99	220	&hash, &hashlen
fe4ad273	221	);
fe4ad273	222	}
b46fa825	223	BN_free(dh_client_pub);
fe4ad273	224
b46fa825	225	if (kex->session_id == NULL) {
d33fd7cd	226	kex->session_id_len = hashlen;
b46fa825	227	kex->session_id = xmalloc(kex->session_id_len);
	228	memcpy(kex->session_id, hash, kex->session_id_len);
	229	}
fe4ad273	230
b46fa825	231	gssbuf.value = hash;
d33fd7cd	232	gssbuf.length = hashlen;
fe4ad273	233
fe4ad273	234	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
23987cb8	235	fatal("Couldn't get MIC");
fe4ad273	236
b46fa825	237	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
	238	packet_put_bignum2(dh->pub_key);
	239	packet_put_string((char *)msg_tok.value,msg_tok.length);
	240
fe4ad273	241	if (send_tok.length != 0) {
b46fa825	242	packet_put_char(1); /* true */
fe4ad273	243	packet_put_string((char *)send_tok.value, send_tok.length);
b46fa825	244	} else {
	245	packet_put_char(0); /* false */
	246	}
fe4ad273	247	packet_send();
	248
	249	gss_release_buffer(&min_status, &send_tok);
	250	gss_release_buffer(&min_status, &msg_tok);
	251
	252	if (gss_kex_context == NULL)
	253	gss_kex_context = ctxt;
	254	else
	255	ssh_gssapi_delete_ctx(&ctxt);
	256
b46fa825	257	DH_free(dh);
b46fa825	258
08822d99	259	kex_derive_keys(kex, hash, hashlen, shared_secret);
b46fa825	260	BN_clear_free(shared_secret);
	261	kex_finish(kex);
	262	}
	263
23987cb8	264	static void
	265	kex_gss_send_error(Gssctxt *ctxt) {
	266	char *errstr;
	267	OM_uint32 maj,min;
	268
	269	errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
	270	if (errstr) {
	271	packet_start(SSH2_MSG_KEXGSS_ERROR);
	272	packet_put_int(maj);
	273	packet_put_int(min);
	274	packet_put_cstring(errstr);
	275	packet_put_cstring("");
	276	packet_send();
	277	packet_write_wait();
	278	/* XXX - We should probably log the error locally here */
	279	xfree(errstr);
	280	}
	281	}
b46fa825	282	#endif /* GSSAPI */