/*
* 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_server_id_kex(kex->name);
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");
}
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; /* int vs. size_t */
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:
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);
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();
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);
if (send_tok.length>0) {
packet_start(SSH2_MSG_KEXGSS_CONTINUE);
packet_put_string(send_tok.value,send_tok.length);
packet_send();
packet_write_wait();
}
fatal("accept_ctx died");
}
debug("gss_complete");
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");
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 */
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