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

/*
 * Copyright (c) 2001,2002 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"

/* This is now the same as the DH hash ... */

u_char *
kex_gssapi_hash(
    char *client_version_string,
    char *server_version_string,
    char *ckexinit, int ckexinitlen,
    char *skexinit, int skexinitlen,
    u_char *serverhostkeyblob, int sbloblen,
    BIGNUM *client_dh_pub,
    BIGNUM *server_dh_pub,
    BIGNUM *shared_secret)
{
	Buffer b;
	static u_char digest[EVP_MAX_MD_SIZE];
	EVP_MD *evp_md = EVP_sha1();
	EVP_MD_CTX md;

	buffer_init(&b);
	buffer_put_string(&b, client_version_string, strlen(client_version_string));
	buffer_put_string(&b, server_version_string, strlen(server_version_string));

	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
	buffer_put_int(&b, ckexinitlen+1);
	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	buffer_append(&b, ckexinit, ckexinitlen);
	buffer_put_int(&b, skexinitlen+1);
	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	buffer_append(&b, skexinit, skexinitlen);

	buffer_put_string(&b, serverhostkeyblob, sbloblen);
	buffer_put_bignum2(&b, client_dh_pub);
	buffer_put_bignum2(&b, server_dh_pub);
	buffer_put_bignum2(&b, shared_secret);

#ifdef DEBUG_KEX
	buffer_dump(&b);
#endif
	EVP_DigestInit(&md, evp_md);
	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	EVP_DigestFinal(&md, digest, NULL);

	buffer_free(&b);

#ifdef DEBUG_KEX
	dump_digest("hash", digest, evp_md->md_size);
#endif
	return digest;
}

void
kexgss_client(Kex *kex)
{
	gss_buffer_desc gssbuf,send_tok,recv_tok, msg_tok, *token_ptr;
	Gssctxt *ctxt;
	OM_uint32 maj_status, min_status, ret_flags;
	unsigned int klen, kout;
	DH *dh; 
	BIGNUM *dh_server_pub = 0;
	BIGNUM *shared_secret = 0;	
	unsigned char *kbuf;
	unsigned char *hash;
	unsigned char *serverhostkey;
	int type = 0;
	int first = 1;
	int slen = 0;
	
	/* Initialise our GSSAPI world */
	ssh_gssapi_build_ctx(&ctxt);
	if (ssh_gssapi_id_kex(ctxt,kex->name)==NULL) {
		fatal("Couldn't identify host exchange");
	}
	if (ssh_gssapi_import_name(ctxt,kex->host)) {
		fatal("Couldn't import hostname ");
	}
	
	/* This code should match that in ssh_dh1_client */
		
	/* Step 1 - e is dh->pub_key */
	dh = dh_new_group1();
	dh_gen_key(dh, kex->we_need * 8);

	/* This is f, we initialise it now to make life easier */
    	dh_server_pub = BN_new();
    	if (dh_server_pub == NULL) {
    		fatal("dh_server_pub == NULL");
    	}
    		
	token_ptr = GSS_C_NO_BUFFER;
			 
	do {
		debug("Calling gss_init_sec_context");
		
		maj_status=ssh_gssapi_init_ctx(ctxt,
					       kex->options.gss_deleg_creds,
					       token_ptr,&send_tok,
					       &ret_flags);

		if (GSS_ERROR(maj_status)) {
			fatal("gss_init_context failed");
		} 

		/* If we've got an old receive buffer get rid of it */
		if (token_ptr != GSS_C_NO_BUFFER)
	  		(void) gss_release_buffer(&min_status, &recv_tok);
 	
		
		if (maj_status == GSS_S_COMPLETE) {
			/* If mutual state flag is not true, kex fails */
			if (!(ret_flags & GSS_C_MUTUAL_FLAG)) {
				fatal("Mutual authentication failed");
			}
			/* If integ avail flag is not true kex fails */
			if (!(ret_flags & GSS_C_INTEG_FLAG)) {
				fatal("Integrity check failed");
			}
		}
		
		/* If we have data to send, then the last message that we
		 * received cannot have been a 'complete'. */
		if (send_tok.length !=0) {
			if (first) {
				packet_start(SSH2_MSG_KEXGSS_INIT);
				packet_put_string(send_tok.value,
					  	  send_tok.length);
				packet_put_bignum2(dh->pub_key);
				first=0;
			} else {
				packet_start(SSH2_MSG_KEXGSS_CONTINUE);
				packet_put_string(send_tok.value,
						  send_tok.length);
			}
			packet_send();
			packet_write_wait();

			
			/* If we've sent them data, they'd better be polite
			 * and reply. */
		
			type = packet_read();
			switch (type) {
			case SSH2_MSG_KEXGSS_HOSTKEY:
				debug("Received KEXGSS_HOSTKEY");
				serverhostkey=packet_get_string(&slen);
				break;
			case SSH2_MSG_KEXGSS_CONTINUE:
				debug("Received GSSAPI_CONTINUE");
				if (maj_status == GSS_S_COMPLETE) 
					fatal("GSSAPI Continue received from server when complete");
				recv_tok.value=packet_get_string(&recv_tok.length);
				break;
			case SSH2_MSG_KEXGSS_COMPLETE:
				debug("Received GSSAPI_COMPLETE");
			        packet_get_bignum2(dh_server_pub);
			    	msg_tok.value=
			    	    packet_get_string(&msg_tok.length);

				/* Is there a token included? */
				if (packet_get_char()) {
					recv_tok.value=
					    packet_get_string(&recv_tok.length);
					/* If we're already complete - protocol error */
					if (maj_status == GSS_S_COMPLETE)
						packet_disconnect("Protocol error: received token when complete");
				} else {
				   	/* No token included */
				   	if (maj_status != GSS_S_COMPLETE)
				   		packet_disconnect("Protocol error: did not receive final token");
				}
				break;
			default:
				packet_disconnect("Protocol error: didn't expect packet type %d",
		    		type);
			}
			token_ptr=&recv_tok;
		}

    	} while (maj_status & GSS_S_CONTINUE_NEEDED);
    	
    	/* We _must_ have received a COMPLETE message in reply from the 
    	 * server, which will have set dh_server_pub and msg_tok */
    	 
    	if (type!=SSH2_MSG_KEXGSS_COMPLETE)
    	   fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
    	 	    	
	/* Check f in range [1, p-1] */
        if (!dh_pub_is_valid(dh, dh_server_pub))
                        packet_disconnect("bad server public DH value");
                        
        /* compute K=f^x mod p */
        klen = DH_size(dh);
        kbuf = xmalloc(klen);
        kout = DH_compute_key(kbuf, dh_server_pub, dh);
        
        shared_secret = BN_new();
        BN_bin2bn(kbuf,kout, shared_secret);
        memset(kbuf, 0, klen);
        xfree(kbuf);
        
        hash = kex_gssapi_hash(
 	    kex->client_version_string,
            kex->server_version_string,
            buffer_ptr(&kex->my), buffer_len(&kex->my),
            buffer_ptr(&kex->peer), buffer_len(&kex->peer),
            serverhostkey, slen, /* server host key */
            dh->pub_key,	/* e */
            dh_server_pub,	/* f */
            shared_secret	/* K */
        );
        
        gssbuf.value=hash;
        gssbuf.length=20;
        
        /* Verify that H matches the token we just got. */
                if ((maj_status = gss_verify_mic(&min_status,
        	       		         ctxt->context,
        	                         &gssbuf,
        	                         &msg_tok,
        	                         NULL))) {

		packet_disconnect("Hash's MIC didn't verify");
      	}	
        
        DH_free(dh);
       	ssh_gssapi_delete_ctx(&ctxt);
        /* save session id */
        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);
        }
        
	kex_derive_keys(kex, hash, shared_secret);
	BN_clear_free(shared_secret);
        kex_finish(kex);
}


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;
	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))))
	   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(&recv_tok.length);

		        dh_client_pub = BN_new();
		        
		        if (dh_client_pub == 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:
			if (dh_client_pub == NULL)
				packet_disconnect("Received KEXGSS_CONTINUE without initialising");
			recv_tok.value=packet_get_string(&recv_tok.length);
			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) {
			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)) {
		ssh_gssapi_send_error(maj_status,min_status);
		packet_disconnect("gssapi key exchange handshake failed");
	}

	debug("gss_complete");
	if (!(ret_flags & GSS_C_MUTUAL_FLAG)) {
		ssh_gssapi_send_error(maj_status,min_status);
		packet_disconnect("gssapi mutual authentication failed");
	}
		
	if (!(ret_flags & GSS_C_INTEG_FLAG)) {
		ssh_gssapi_send_error(maj_status,min_status);
		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);
	
        hash = kex_gssapi_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)))) {
		ssh_gssapi_send_error(maj_status,min_status);
		packet_disconnect("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);
}

void 
kexgss(Kex *kex)
{
	if (kex->server)
		kexgss_server(kex);
	else
		kexgss_client(kex);
}

#endif /* GSSAPI */
Commit	Line	Data
5598e598	1	/*
905081a4	2	* Copyright (c) 2001,2002 Simon Wilkinson. All rights reserved.
5598e598	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"
b59afbfe	41	#include "monitor_wrap.h"
5598e598	42
	43	/* This is now the same as the DH hash ... */
	44
	45	u_char *
	46	kex_gssapi_hash(
	47	char *client_version_string,
	48	char *server_version_string,
	49	char *ckexinit, int ckexinitlen,
	50	char *skexinit, int skexinitlen,
	51	u_char *serverhostkeyblob, int sbloblen,
	52	BIGNUM *client_dh_pub,
	53	BIGNUM *server_dh_pub,
	54	BIGNUM *shared_secret)
	55	{
	56	Buffer b;
	57	static u_char digest[EVP_MAX_MD_SIZE];
	58	EVP_MD *evp_md = EVP_sha1();
	59	EVP_MD_CTX md;
	60
	61	buffer_init(&b);
	62	buffer_put_string(&b, client_version_string, strlen(client_version_string));
	63	buffer_put_string(&b, server_version_string, strlen(server_version_string));
	64
	65	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
	66	buffer_put_int(&b, ckexinitlen+1);
	67	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	68	buffer_append(&b, ckexinit, ckexinitlen);
	69	buffer_put_int(&b, skexinitlen+1);
	70	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	71	buffer_append(&b, skexinit, skexinitlen);
	72
	73	buffer_put_string(&b, serverhostkeyblob, sbloblen);
	74	buffer_put_bignum2(&b, client_dh_pub);
	75	buffer_put_bignum2(&b, server_dh_pub);
	76	buffer_put_bignum2(&b, shared_secret);
	77
	78	#ifdef DEBUG_KEX
	79	buffer_dump(&b);
	80	#endif
	81	EVP_DigestInit(&md, evp_md);
	82	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	83	EVP_DigestFinal(&md, digest, NULL);
	84
	85	buffer_free(&b);
	86
	87	#ifdef DEBUG_KEX
	88	dump_digest("hash", digest, evp_md->md_size);
	89	#endif
	90	return digest;
	91	}
	92
	93	void
	94	kexgss_client(Kex *kex)
	95	{
	96	gss_buffer_desc gssbuf,send_tok,recv_tok, msg_tok, *token_ptr;
b59afbfe	97	Gssctxt *ctxt;
5598e598	98	OM_uint32 maj_status, min_status, ret_flags;
5598e598	99	unsigned int klen, kout;
	100	DH *dh;
	101	BIGNUM *dh_server_pub = 0;
	102	BIGNUM *shared_secret = 0;
	103	unsigned char *kbuf;
	104	unsigned char *hash;
	105	unsigned char *serverhostkey;
	106	int type = 0;
	107	int first = 1;
	108	int slen = 0;
	109
	110	/* Initialise our GSSAPI world */
	111	ssh_gssapi_build_ctx(&ctxt);
b59afbfe	112	if (ssh_gssapi_id_kex(ctxt,kex->name)==NULL) {
5598e598	113	fatal("Couldn't identify host exchange");
5598e598	114	}
b59afbfe	115	if (ssh_gssapi_import_name(ctxt,kex->host)) {
5598e598	116	fatal("Couldn't import hostname ");
	117	}
	118
	119	/* This code should match that in ssh_dh1_client */
	120
	121	/* Step 1 - e is dh->pub_key */
	122	dh = dh_new_group1();
	123	dh_gen_key(dh, kex->we_need * 8);
	124
	125	/* This is f, we initialise it now to make life easier */
	126	dh_server_pub = BN_new();
	127	if (dh_server_pub == NULL) {
	128	fatal("dh_server_pub == NULL");
	129	}
	130
	131	token_ptr = GSS_C_NO_BUFFER;
	132
	133	do {
	134	debug("Calling gss_init_sec_context");
	135
b59afbfe	136	maj_status=ssh_gssapi_init_ctx(ctxt,
5598e598	137	kex->options.gss_deleg_creds,
	138	token_ptr,&send_tok,
	139	&ret_flags);
	140
	141	if (GSS_ERROR(maj_status)) {
	142	fatal("gss_init_context failed");
	143	}
	144
	145	/* If we've got an old receive buffer get rid of it */
	146	if (token_ptr != GSS_C_NO_BUFFER)
	147	(void) gss_release_buffer(&min_status, &recv_tok);
	148
	149
	150	if (maj_status == GSS_S_COMPLETE) {
	151	/* If mutual state flag is not true, kex fails */
	152	if (!(ret_flags & GSS_C_MUTUAL_FLAG)) {
	153	fatal("Mutual authentication failed");
	154	}
	155	/* If integ avail flag is not true kex fails */
	156	if (!(ret_flags & GSS_C_INTEG_FLAG)) {
	157	fatal("Integrity check failed");
	158	}
	159	}
	160
	161	/* If we have data to send, then the last message that we
	162	* received cannot have been a 'complete'. */
	163	if (send_tok.length !=0) {
	164	if (first) {
	165	packet_start(SSH2_MSG_KEXGSS_INIT);
	166	packet_put_string(send_tok.value,
	167	send_tok.length);
	168	packet_put_bignum2(dh->pub_key);
	169	first=0;
	170	} else {
	171	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
	172	packet_put_string(send_tok.value,
	173	send_tok.length);
	174	}
	175	packet_send();
	176	packet_write_wait();
	177
	178
	179	/* If we've sent them data, they'd better be polite
	180	* and reply. */
	181
6d25b646	182	type = packet_read();
5598e598	183	switch (type) {
	184	case SSH2_MSG_KEXGSS_HOSTKEY:
	185	debug("Received KEXGSS_HOSTKEY");
	186	serverhostkey=packet_get_string(&slen);
	187	break;
	188	case SSH2_MSG_KEXGSS_CONTINUE:
	189	debug("Received GSSAPI_CONTINUE");
	190	if (maj_status == GSS_S_COMPLETE)
	191	fatal("GSSAPI Continue received from server when complete");
	192	recv_tok.value=packet_get_string(&recv_tok.length);
	193	break;
	194	case SSH2_MSG_KEXGSS_COMPLETE:
	195	debug("Received GSSAPI_COMPLETE");
6d25b646	196	packet_get_bignum2(dh_server_pub);
5598e598	197	msg_tok.value=
	198	packet_get_string(&msg_tok.length);
	199
	200	/* Is there a token included? */
	201	if (packet_get_char()) {
	202	recv_tok.value=
	203	packet_get_string(&recv_tok.length);
	204	/* If we're already complete - protocol error */
	205	if (maj_status == GSS_S_COMPLETE)
	206	packet_disconnect("Protocol error: received token when complete");
	207	} else {
	208	/* No token included */
	209	if (maj_status != GSS_S_COMPLETE)
	210	packet_disconnect("Protocol error: did not receive final token");
	211	}
	212	break;
	213	default:
	214	packet_disconnect("Protocol error: didn't expect packet type %d",
	215	type);
	216	}
	217	token_ptr=&recv_tok;
	218	}
	219
	220	} while (maj_status & GSS_S_CONTINUE_NEEDED);
	221
	222	/* We _must_ have received a COMPLETE message in reply from the
	223	* server, which will have set dh_server_pub and msg_tok */
	224
	225	if (type!=SSH2_MSG_KEXGSS_COMPLETE)
	226	fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
	227
	228	/* Check f in range [1, p-1] */
	229	if (!dh_pub_is_valid(dh, dh_server_pub))
	230	packet_disconnect("bad server public DH value");
	231
	232	/* compute K=f^x mod p */
	233	klen = DH_size(dh);
	234	kbuf = xmalloc(klen);
	235	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	236
	237	shared_secret = BN_new();
	238	BN_bin2bn(kbuf,kout, shared_secret);
	239	memset(kbuf, 0, klen);
	240	xfree(kbuf);
	241
	242	hash = kex_gssapi_hash(
	243	kex->client_version_string,
	244	kex->server_version_string,
	245	buffer_ptr(&kex->my), buffer_len(&kex->my),
	246	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	247	serverhostkey, slen, /* server host key */
	248	dh->pub_key, /* e */
	249	dh_server_pub, /* f */
	250	shared_secret /* K */
	251	);
	252
	253	gssbuf.value=hash;
	254	gssbuf.length=20;
	255
	256	/* Verify that H matches the token we just got. */
	257	if ((maj_status = gss_verify_mic(&min_status,
b59afbfe	258	ctxt->context,
5598e598	259	&gssbuf,
	260	&msg_tok,
	261	NULL))) {
	262
	263	packet_disconnect("Hash's MIC didn't verify");
	264	}
	265
	266	DH_free(dh);
	267	ssh_gssapi_delete_ctx(&ctxt);
	268	/* save session id */
	269	if (kex->session_id == NULL) {
	270	kex->session_id_len = 20;
	271	kex->session_id = xmalloc(kex->session_id_len);
	272	memcpy(kex->session_id, hash, kex->session_id_len);
	273	}
	274
	275	kex_derive_keys(kex, hash, shared_secret);
	276	BN_clear_free(shared_secret);
	277	kex_finish(kex);
	278	}
	279
	280
	281
	282
	283	void
	284	kexgss_server(Kex *kex)
	285	{
	286
	287	OM_uint32 maj_status, min_status;
	288
	289	/* Some GSSAPI implementations use the input value of ret_flags (an
	290	* output variable) as a means of triggering mechanism specific
	291	* features. Initializing it to zero avoids inadvertently
	292	* activating this non-standard behaviour.*/
	293
	294	OM_uint32 ret_flags = 0;
	295	gss_buffer_desc gssbuf,send_tok,recv_tok,msg_tok;
b59afbfe	296	Gssctxt *ctxt = NULL;
5598e598	297	unsigned int klen, kout;
	298	unsigned char *kbuf;
	299	unsigned char *hash;
	300	DH *dh;
905081a4	301	BIGNUM *shared_secret = NULL;
905081a4	302	BIGNUM *dh_client_pub = NULL;
5598e598	303	int type =0;
b59afbfe	304	gss_OID oid;
5598e598	305
	306	/* Initialise GSSAPI */
	307
b59afbfe	308	debug2("%s: Identifying %s",__func__,kex->name);
	309	oid=ssh_gssapi_id_kex(ctxt,kex->name);
	310	if (oid==NULL) {
	311	packet_disconnect("Unknown gssapi mechanism");
	312	}
	313
	314	debug2("%s: Acquiring credentials",__func__);
	315
	316	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt,oid))))
	317	packet_disconnect("Unable to acquire credentials for the server");
5598e598	318
5598e598	319	do {
5598e598	320	debug("Wait SSH2_MSG_GSSAPI_INIT");
6d25b646	321	type = packet_read();
5598e598	322	switch(type) {
5598e598	323	case SSH2_MSG_KEXGSS_INIT:
905081a4	324	if (dh_client_pub!=NULL)
de4d4506	325	packet_disconnect("Received KEXGSS_INIT after initialising");
5598e598	326	recv_tok.value=packet_get_string(&recv_tok.length);
905081a4	327
	328	dh_client_pub = BN_new();
	329
	330	if (dh_client_pub == NULL)
	331	fatal("dh_client_pub == NULL");
6d25b646	332	packet_get_bignum2(dh_client_pub);
905081a4	333
5598e598	334	/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
	335	break;
	336	case SSH2_MSG_KEXGSS_CONTINUE:
905081a4	337	if (dh_client_pub == NULL)
de4d4506	338	packet_disconnect("Received KEXGSS_CONTINUE without initialising");
5598e598	339	recv_tok.value=packet_get_string(&recv_tok.length);
	340	break;
	341	default:
	342	packet_disconnect("Protocol error: didn't expect packet type %d",
	343	type);
	344	}
b59afbfe	345
	346	maj_status=PRIVSEP(ssh_gssapi_accept_ctx(ctxt,&recv_tok,
	347	&send_tok, &ret_flags));
5598e598	348
5598e598	349	gss_release_buffer(&min_status,&recv_tok);
3d9d1aaf	350
	351	#ifdef GSS_C_GLOBUS_LIMITED_PROXY_FLAG
	352	if (ret_flags & GSS_C_GLOBUS_LIMITED_PROXY_FLAG) {
de4d4506	353	packet_disconnect("Limited proxy is not allowed in gssapi key exchange.");
3d9d1aaf	354	}
3d9d1aaf	355	#endif
5598e598	356
	357	if (maj_status & GSS_S_CONTINUE_NEEDED) {
	358	debug("Sending GSSAPI_CONTINUE");
	359	packet_start(SSH2_MSG_KEXGSS_CONTINUE);
	360	packet_put_string(send_tok.value,send_tok.length);
	361	packet_send();
	362	packet_write_wait();
	363	gss_release_buffer(&min_status, &send_tok);
	364	}
	365	} while (maj_status & GSS_S_CONTINUE_NEEDED);
	366
de4d4506	367	if (GSS_ERROR(maj_status)) {
	368	ssh_gssapi_send_error(maj_status,min_status);
	369	packet_disconnect("gssapi key exchange handshake failed");
	370	}
	371
5598e598	372	debug("gss_complete");
de4d4506	373	if (!(ret_flags & GSS_C_MUTUAL_FLAG)) {
	374	ssh_gssapi_send_error(maj_status,min_status);
	375	packet_disconnect("gssapi mutual authentication failed");
	376	}
5598e598	377
de4d4506	378	if (!(ret_flags & GSS_C_INTEG_FLAG)) {
	379	ssh_gssapi_send_error(maj_status,min_status);
	380	packet_disconnect("gssapi channel integrity not established");
	381	}
5598e598	382
	383	dh = dh_new_group1();
	384	dh_gen_key(dh, kex->we_need * 8);
	385
	386	if (!dh_pub_is_valid(dh, dh_client_pub))
	387	packet_disconnect("bad client public DH value");
	388
	389	klen = DH_size(dh);
	390	kbuf = xmalloc(klen);
	391	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	392
	393	shared_secret = BN_new();
	394	BN_bin2bn(kbuf, kout, shared_secret);
	395	memset(kbuf, 0, klen);
	396	xfree(kbuf);
	397
	398	hash = kex_gssapi_hash(
	399	kex->client_version_string,
	400	kex->server_version_string,
	401	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	402	buffer_ptr(&kex->my), buffer_len(&kex->my),
	403	NULL, 0, /* Change this if we start sending host keys */
	404	dh_client_pub,
	405	dh->pub_key,
	406	shared_secret
	407	);
	408	BN_free(dh_client_pub);
	409
	410	if (kex->session_id == NULL) {
	411	kex->session_id_len = 20;
	412	kex->session_id = xmalloc(kex->session_id_len);
	413	memcpy(kex->session_id, hash, kex->session_id_len);
	414	}
	415
	416	gssbuf.value = hash;
	417	gssbuf.length = 20; /* Hashlen appears to always be 20 */
	418
b59afbfe	419	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok)))) {
de4d4506	420	ssh_gssapi_send_error(maj_status,min_status);
de4d4506	421	packet_disconnect("Couldn't get MIC");
b59afbfe	422	}
b59afbfe	423
5598e598	424	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
	425	packet_put_bignum2(dh->pub_key);
	426	packet_put_string((char *)msg_tok.value,msg_tok.length);
	427
	428	if (send_tok.length!=0) {
	429	packet_put_char(1); /* true */
	430	packet_put_string((char *)send_tok.value,send_tok.length);
	431	} else {
	432	packet_put_char(0); /* false */
	433	}
	434	packet_send();
	435	packet_write_wait();
	436
b59afbfe	437	/* We used to store the client name and credentials here for later
	438	* use. With privsep, its easier to do this as a by product of the
	439	* call to accept_context, which stores delegated information when
	440	* the context is complete */
	441
5598e598	442	gss_release_buffer(&min_status, &send_tok);
b59afbfe	443
	444	/* If we've got a context, delete it. It may be NULL if we've been
	445	* using privsep */
5598e598	446	ssh_gssapi_delete_ctx(&ctxt);
b59afbfe	447
5598e598	448	DH_free(dh);
	449
	450	kex_derive_keys(kex, hash, shared_secret);
	451	BN_clear_free(shared_secret);
	452	kex_finish(kex);
	453	}
	454
	455	void
	456	kexgss(Kex *kex)
	457	{
	458	if (kex->server)
	459	kexgss_server(kex);
	460	else
	461	kexgss_client(kex);
	462	}
	463
	464	#endif /* GSSAPI */