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

/*
 * Copyright (c) 2001-2003 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,send_tok,recv_tok,msg_tok;
	Gssctxt *ctxt = NULL;
        unsigned int klen, kout;
        unsigned char *kbuf;
        unsigned char *hash;
        DH *dh;
        BIGNUM *shared_secret = NULL;
        BIGNUM *dh_client_pub = NULL;
	int type =0;
	u_int slen;
	gss_OID oid;
	
	/* Initialise GSSAPI */

	debug2("%s: Identifying %s",__func__,kex->name);
	oid=ssh_gssapi_id_kex(ctxt,kex->name);
	if (oid==NULL) {
	   packet_disconnect("Unknown gssapi mechanism");
	}
	
	debug2("%s: Acquiring credentials",__func__);
	
	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt,oid)))) {
		kex_gss_send_error(ctxt);
        	packet_disconnect("Unable to acquire credentials for the server");
        }
                                                                                                                                
	do {
		debug("Wait SSH2_MSG_GSSAPI_INIT");
		type = packet_read();
		switch(type) {
		case SSH2_MSG_KEXGSS_INIT:
			if (dh_client_pub!=NULL) 
				packet_disconnect("Received KEXGSS_INIT after initialising");
			recv_tok.value=packet_get_string(&slen);
			recv_tok.length=slen; /* int vs. size_t */

		        dh_client_pub = BN_new();
		        
		        if (dh_client_pub == NULL)
        			packet_disconnect("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:
			if (dh_client_pub == NULL)
				packet_disconnect("Received KEXGSS_CONTINUE without initialising");
			recv_tok.value=packet_get_string(&slen);
			recv_tok.length=slen; /* int vs. size_t */
			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));

		gss_release_buffer(&min_status,&recv_tok);
		
#ifdef GSS_C_GLOBUS_LIMITED_PROXY_FLAG
                if (ret_flags & GSS_C_GLOBUS_LIMITED_PROXY_FLAG) {
                        packet_disconnect("Limited proxy is not allowed in gssapi key exchange.");
                }
#endif

		if ((maj_status & GSS_S_CONTINUE_NEEDED) ||
		    (GSS_ERROR(maj_status) && send_tok.length>0)) {
			debug("Sending GSSAPI_CONTINUE");
			packet_start(SSH2_MSG_KEXGSS_CONTINUE);
			packet_put_string(send_tok.value,send_tok.length);
			packet_send();
			packet_write_wait();
			gss_release_buffer(&min_status, &send_tok);
		}
	} while (maj_status & GSS_S_CONTINUE_NEEDED);

	if (GSS_ERROR(maj_status)) {
		kex_gss_send_error(ctxt);
		packet_disconnect("gssapi key exchange handshake failed");
	}
	
	debug("gss_complete");
	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
		packet_disconnect("gssapi_mutual authentication failed");
		
	if (!(ret_flags & GSS_C_INTEG_FLAG))
		packet_disconnect("gssapi channel integrity not established");
			
	dh = dh_new_group1();
	dh_gen_key(dh, kex->we_need * 8);
	
        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);
	
	/* 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)))) {
		kex_gss_send_error(ctxt);
		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();
	packet_write_wait();

        /* We used to store the client name and credentials here for later
         * use. With privsep, its easier to do this as a by product of the
         * call to accept_context, which stores delegated information when
         * the context is complete */
         
	gss_release_buffer(&min_status, &send_tok);	

	/* If we've got a context, delete it. It may be NULL if we've been
	* using privsep */
	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	/*
23987cb8	2	* Copyright (c) 2001-2003 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;
	49
	50	/* Some GSSAPI implementations use the input value of ret_flags (an
23987cb8	51	* output variable) as a means of triggering mechanism specific
	52	* features. Initializing it to zero avoids inadvertently
	53	* activating this non-standard behaviour.*/
b46fa825	54
	55	OM_uint32 ret_flags = 0;
	56	gss_buffer_desc gssbuf,send_tok,recv_tok,msg_tok;
	57	Gssctxt *ctxt = NULL;
	58	unsigned int klen, kout;
	59	unsigned char *kbuf;
	60	unsigned char *hash;
	61	DH *dh;
	62	BIGNUM *shared_secret = NULL;
	63	BIGNUM *dh_client_pub = NULL;
	64	int type =0;
b46fa825	65	u_int slen;
23987cb8	66	gss_OID oid;
b46fa825	67
	68	/* Initialise GSSAPI */
	69
	70	debug2("%s: Identifying %s",__func__,kex->name);
	71	oid=ssh_gssapi_id_kex(ctxt,kex->name);
	72	if (oid==NULL) {
	73	packet_disconnect("Unknown gssapi mechanism");
	74	}
	75
	76	debug2("%s: Acquiring credentials",__func__);
	77
23987cb8	78	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt,oid)))) {
	79	kex_gss_send_error(ctxt);
	80	packet_disconnect("Unable to acquire credentials for the server");
	81	}
	82
b46fa825	83	do {
	84	debug("Wait SSH2_MSG_GSSAPI_INIT");
	85	type = packet_read();
	86	switch(type) {
	87	case SSH2_MSG_KEXGSS_INIT:
	88	if (dh_client_pub!=NULL)
	89	packet_disconnect("Received KEXGSS_INIT after initialising");
	90	recv_tok.value=packet_get_string(&slen);
	91	recv_tok.length=slen; /* int vs. size_t */
	92
	93	dh_client_pub = BN_new();
	94
	95	if (dh_client_pub == NULL)
23987cb8	96	packet_disconnect("dh_client_pub == NULL");
b46fa825	97	packet_get_bignum2(dh_client_pub);
	98
	99	/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
	100	break;
	101	case SSH2_MSG_KEXGSS_CONTINUE:
	102	if (dh_client_pub == NULL)
	103	packet_disconnect("Received KEXGSS_CONTINUE without initialising");
	104	recv_tok.value=packet_get_string(&slen);
	105	recv_tok.length=slen; /* int vs. size_t */
	106	break;
	107	default:
	108	packet_disconnect("Protocol error: didn't expect packet type %d",
	109	type);
	110	}
	111
	112	maj_status=PRIVSEP(ssh_gssapi_accept_ctx(ctxt,&recv_tok,
23987cb8	113	&send_tok, &ret_flags));
b46fa825	114
b46fa825	115	gss_release_buffer(&min_status,&recv_tok);
23987cb8	116
b46fa825	117	#ifdef GSS_C_GLOBUS_LIMITED_PROXY_FLAG
	118	if (ret_flags & GSS_C_GLOBUS_LIMITED_PROXY_FLAG) {
	119	packet_disconnect("Limited proxy is not allowed in gssapi key exchange.");
	120	}
	121	#endif
23987cb8	122
	123	if ((maj_status & GSS_S_CONTINUE_NEEDED) \|\|
	124	(GSS_ERROR(maj_status) && send_tok.length>0)) {
b46fa825	125	debug("Sending GSSAPI_CONTINUE");
	126	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
	127	packet_put_string(send_tok.value,send_tok.length);
	128	packet_send();
	129	packet_write_wait();
	130	gss_release_buffer(&min_status, &send_tok);
	131	}
	132	} while (maj_status & GSS_S_CONTINUE_NEEDED);
	133
	134	if (GSS_ERROR(maj_status)) {
23987cb8	135	kex_gss_send_error(ctxt);
b46fa825	136	packet_disconnect("gssapi key exchange handshake failed");
b46fa825	137	}
23987cb8	138
b46fa825	139	debug("gss_complete");
23987cb8	140	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
23987cb8	141	packet_disconnect("gssapi_mutual authentication failed");
b46fa825	142
23987cb8	143	if (!(ret_flags & GSS_C_INTEG_FLAG))
b46fa825	144	packet_disconnect("gssapi channel integrity not established");
23987cb8	145
b46fa825	146	dh = dh_new_group1();
	147	dh_gen_key(dh, kex->we_need * 8);
	148
	149	if (!dh_pub_is_valid(dh, dh_client_pub))
	150	packet_disconnect("bad client public DH value");
	151
	152	klen = DH_size(dh);
	153	kbuf = xmalloc(klen);
	154	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	155
	156	shared_secret = BN_new();
	157	BN_bin2bn(kbuf, kout, shared_secret);
	158	memset(kbuf, 0, klen);
	159	xfree(kbuf);
	160
23987cb8	161	/* The GSSAPI hash is identical to the Diffie Helman one */
23987cb8	162	hash = kex_dh_hash(
b46fa825	163	kex->client_version_string,
	164	kex->server_version_string,
	165	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	166	buffer_ptr(&kex->my), buffer_len(&kex->my),
	167	NULL, 0, /* Change this if we start sending host keys */
	168	dh_client_pub,
	169	dh->pub_key,
	170	shared_secret
	171	);
	172	BN_free(dh_client_pub);
	173
	174	if (kex->session_id == NULL) {
	175	kex->session_id_len = 20;
	176	kex->session_id = xmalloc(kex->session_id_len);
	177	memcpy(kex->session_id, hash, kex->session_id_len);
	178	}
	179
	180	gssbuf.value = hash;
	181	gssbuf.length = 20; /* Hashlen appears to always be 20 */
	182
	183	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok)))) {
23987cb8	184	kex_gss_send_error(ctxt);
23987cb8	185	fatal("Couldn't get MIC");
b46fa825	186	}
	187
	188	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
	189	packet_put_bignum2(dh->pub_key);
	190	packet_put_string((char *)msg_tok.value,msg_tok.length);
	191
	192	if (send_tok.length!=0) {
	193	packet_put_char(1); /* true */
	194	packet_put_string((char *)send_tok.value,send_tok.length);
	195	} else {
	196	packet_put_char(0); /* false */
	197	}
	198	packet_send();
	199	packet_write_wait();
	200
	201	/* We used to store the client name and credentials here for later
	202	* use. With privsep, its easier to do this as a by product of the
	203	* call to accept_context, which stores delegated information when
	204	* the context is complete */
	205
	206	gss_release_buffer(&min_status, &send_tok);
	207
	208	/* If we've got a context, delete it. It may be NULL if we've been
23987cb8	209	* using privsep */
b46fa825	210	ssh_gssapi_delete_ctx(&ctxt);
	211
	212	DH_free(dh);
	213
	214	kex_derive_keys(kex, hash, shared_secret);
	215	BN_clear_free(shared_secret);
	216	kex_finish(kex);
	217	}
	218
23987cb8	219	static void
	220	kex_gss_send_error(Gssctxt *ctxt) {
	221	char *errstr;
	222	OM_uint32 maj,min;
	223
	224	errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
	225	if (errstr) {
	226	packet_start(SSH2_MSG_KEXGSS_ERROR);
	227	packet_put_int(maj);
	228	packet_put_int(min);
	229	packet_put_cstring(errstr);
	230	packet_put_cstring("");
	231	packet_send();
	232	packet_write_wait();
	233	/* XXX - We should probably log the error locally here */
	234	xfree(errstr);
	235	}
	236	}
b46fa825	237	#endif /* GSSAPI */