/* $OpenBSD: auth2-gss.c,v 1.22 2015/01/19 20:07:45 markus Exp $ */

/*

* Copyright (c) 2001-2007 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 *);

/*

* The 'gssapi_keyex' userauth mechanism.

*/

static int

userauth_gsskeyex(Authctxt *authctxt)

{

int authenticated = 0;

Buffer b;

gss_buffer_desc mic, gssbuf;

u_int len;

mic.value = packet_get_string(&len);

mic.length = len;

packet_check_eom();

ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,

"gssapi-keyex");

gssbuf.value = buffer_ptr(&b);

gssbuf.length = buffer_len(&b);

/* gss_kex_context is NULL with privsep, so we can't check it here */

if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gss_kex_context,

&gssbuf, &mic))))

authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,

authctxt->pw));

buffer_free(&b);

free(mic.value);

return (authenticated);

}

/*

* 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->pw));

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, authctxt->pw));

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_gsskeyex = {

"gssapi-keyex",

userauth_gsskeyex,

&options.gss_authentication

};

Authmethod method_gssapi = {

"gssapi-with-mic",

userauth_gssapi,

&options.gss_authentication

};

#endif /* GSSAPI */