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/* $OpenBSD: auth2-gss.c,v 1.22 2015/01/19 20:07:45 markus Exp $ */
/*
* 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 <sys/types.h>
#include <stdarg.h>
#include "xmalloc.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "ssh2.h"
#include "log.h"
#include "dispatch.h"
#include "buffer.h"
#include "misc.h"
#include "servconf.h"
#include "packet.h"
#include "ssh-gss.h"
#include "monitor_wrap.h"
extern ServerOptions options;
static int input_gssapi_token(int type, u_int32_t plen, void *ctxt);
static int input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
static int input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
static int input_gssapi_errtok(int, u_int32_t, void *);
/*
* We only support those mechanisms that we know about (ie ones that we know
* how to check local user kuserok and the like)
*/
static int
userauth_gssapi(Authctxt *authctxt)
{
gss_OID_desc goid = {0, NULL};
Gssctxt *ctxt = NULL;
int mechs;
int present;
OM_uint32 ms;
u_int len;
u_char *doid = NULL;
if (!authctxt->valid || authctxt->user == NULL)
return (0);
mechs = packet_get_int();
if (mechs == 0) {
debug("Mechanism negotiation is not supported");
return (0);
}
do {
mechs--;
free(doid);
present = 0;
doid = packet_get_string(&len);
if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
doid[1] == len - 2) {
goid.elements = doid + 2;
goid.length = len - 2;
ssh_gssapi_test_oid_supported(&ms, &goid, &present);
} else {
logit("Badly formed OID received");
}
} while (mechs > 0 && !present);
if (!present) {
free(doid);
authctxt->server_caused_failure = 1;
return (0);
}
if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
if (ctxt != NULL)
ssh_gssapi_delete_ctx(&ctxt);
free(doid);
authctxt->server_caused_failure = 1;
return (0);
}
authctxt->methoddata = (void *)ctxt;
packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
/* Return the OID that we received */
packet_put_string(doid, len);
packet_send();
free(doid);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
authctxt->postponed = 1;
return (0);
}
static int
input_gssapi_token(int type, u_int32_t plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
Gssctxt *gssctxt;
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
gss_buffer_desc recv_tok;
OM_uint32 maj_status, min_status, flags;
u_int len;
if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
fatal("No authentication or GSSAPI context");
gssctxt = authctxt->methoddata;
recv_tok.value = packet_get_string(&len);
recv_tok.length = len; /* u_int vs. size_t */
packet_check_eom();
maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
&send_tok, &flags));
free(recv_tok.value);
if (GSS_ERROR(maj_status)) {
if (send_tok.length != 0) {
packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
packet_put_string(send_tok.value, send_tok.length);
packet_send();
}
authctxt->postponed = 0;
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
userauth_finish(authctxt, 0, "gssapi-with-mic", NULL);
} else {
if (send_tok.length != 0) {
packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
packet_put_string(send_tok.value, send_tok.length);
packet_send();
}
if (maj_status == GSS_S_COMPLETE) {
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
if (flags & GSS_C_INTEG_FLAG)
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
&input_gssapi_mic);
else
dispatch_set(
SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
&input_gssapi_exchange_complete);
}
}
gss_release_buffer(&min_status, &send_tok);
return 0;
}
static int
input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
Gssctxt *gssctxt;
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
gss_buffer_desc recv_tok;
OM_uint32 maj_status;
u_int len;
if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
fatal("No authentication or GSSAPI context");
gssctxt = authctxt->methoddata;
recv_tok.value = packet_get_string(&len);
recv_tok.length = len;
packet_check_eom();
/* Push the error token into GSSAPI to see what it says */
maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
&send_tok, NULL));
free(recv_tok.value);
/* We can't return anything to the client, even if we wanted to */
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
/* The client will have already moved on to the next auth */
gss_release_buffer(&maj_status, &send_tok);
return 0;
}
/*
* This is called when the client thinks we've completed authentication.
* It should only be enabled in the dispatch handler by the function above,
* which only enables it once the GSSAPI exchange is complete.
*/
static int
input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
int authenticated;
if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
fatal("No authentication or GSSAPI context");
/*
* We don't need to check the status, because we're only enabled in
* the dispatcher once the exchange is complete
*/
packet_check_eom();
authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
authctxt->postponed = 0;
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
return 0;
}
static int
input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
Gssctxt *gssctxt;
int authenticated = 0;
Buffer b;
gss_buffer_desc mic, gssbuf;
u_int len;
if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
fatal("No authentication or GSSAPI context");
gssctxt = authctxt->methoddata;
mic.value = packet_get_string(&len);
mic.length = len;
ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
"gssapi-with-mic");
gssbuf.value = buffer_ptr(&b);
gssbuf.length = buffer_len(&b);
if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
else
logit("GSSAPI MIC check failed");
buffer_free(&b);
free(mic.value);
authctxt->postponed = 0;
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
return 0;
}
Authmethod method_gssapi = {
"gssapi-with-mic",
userauth_gssapi,
&options.gss_authentication
};
#endif /* GSSAPI */
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