/* $OpenBSD: auth2-gss.c,v 1.33 2021/12/19 22:12:07 djm 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 "sshkey.h"
#include "hostfile.h"
#include "auth.h"
#include "ssh2.h"
#include "log.h"
#include "dispatch.h"
#include "sshbuf.h"
#include "ssherr.h"
#include "misc.h"
#include "servconf.h"
#include "packet.h"
#include "kex.h"
#include "ssh-gss.h"
#include "monitor_wrap.h"
extern ServerOptions options;
static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh);
static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh);
static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh);
static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
/*
* 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(struct ssh *ssh, const char *method)
{
Authctxt *authctxt = ssh->authctxt;
gss_OID_desc goid = {0, NULL};
Gssctxt *ctxt = NULL;
int r, present;
u_int mechs;
OM_uint32 ms;
size_t len;
u_char *doid = NULL;
if ((r = sshpkt_get_u32(ssh, &mechs)) != 0)
fatal_fr(r, "parse packet");
if (mechs == 0) {
debug("Mechanism negotiation is not supported");
return (0);
}
do {
mechs--;
free(doid);
present = 0;
if ((r = sshpkt_get_string(ssh, &doid, &len)) != 0)
fatal_fr(r, "parse oid");
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 (!authctxt->valid || authctxt->user == NULL) {
debug2_f("disabled because of invalid user");
free(doid);
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;
/* Return the OID that we received */
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE)) != 0 ||
(r = sshpkt_put_string(ssh, doid, len)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
free(doid);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
authctxt->postponed = 1;
return (0);
}
static int
input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
Gssctxt *gssctxt;
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
gss_buffer_desc recv_tok;
OM_uint32 maj_status, min_status, flags;
u_char *p;
size_t len;
int r;
if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
fatal("No authentication or GSSAPI context");
gssctxt = authctxt->methoddata;
if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
fatal_fr(r, "parse packet");
recv_tok.value = p;
recv_tok.length = len;
maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
&send_tok, &flags));
free(p);
if (GSS_ERROR(maj_status)) {
if (send_tok.length != 0) {
if ((r = sshpkt_start(ssh,
SSH2_MSG_USERAUTH_GSSAPI_ERRTOK)) != 0 ||
(r = sshpkt_put_string(ssh, send_tok.value,
send_tok.length)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send ERRTOK packet");
}
authctxt->postponed = 0;
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
userauth_finish(ssh, 0, "gssapi-with-mic", NULL);
} else {
if (send_tok.length != 0) {
if ((r = sshpkt_start(ssh,
SSH2_MSG_USERAUTH_GSSAPI_TOKEN)) != 0 ||
(r = sshpkt_put_string(ssh, send_tok.value,
send_tok.length)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send TOKEN packet");
}
if (maj_status == GSS_S_COMPLETE) {
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
if (flags & GSS_C_INTEG_FLAG)
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC,
&input_gssapi_mic);
else
ssh_dispatch_set(ssh,
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, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
Gssctxt *gssctxt;
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
gss_buffer_desc recv_tok;
OM_uint32 maj_status;
int r;
u_char *p;
size_t len;
if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
fatal("No authentication or GSSAPI context");
gssctxt = authctxt->methoddata;
if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
fatal_fr(r, "parse packet");
recv_tok.value = p;
recv_tok.length = len;
/* 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 */
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
ssh_dispatch_set(ssh, 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, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
int r, authenticated;
const char *displayname;
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
*/
if ((r = sshpkt_get_end(ssh)) != 0)
fatal_fr(r, "parse packet");
authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
if ((!use_privsep || mm_is_monitor()) &&
(displayname = ssh_gssapi_displayname()) != NULL)
auth2_record_info(authctxt, "%s", displayname);
authctxt->postponed = 0;
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
return 0;
}
static int
input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
Gssctxt *gssctxt;
int r, authenticated = 0;
struct sshbuf *b;
gss_buffer_desc mic, gssbuf;
const char *displayname;
u_char *p;
size_t len;
if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
fatal("No authentication or GSSAPI context");
gssctxt = authctxt->methoddata;
if ((r = sshpkt_get_string(ssh, &p, &len)) != 0)
fatal_fr(r, "parse packet");
if ((b = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
mic.value = p;
mic.length = len;
ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
"gssapi-with-mic", ssh->kex->session_id);
if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
fatal_f("sshbuf_mutable_ptr failed");
gssbuf.length = sshbuf_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");
sshbuf_free(b);
free(mic.value);
if ((!use_privsep || mm_is_monitor()) &&
(displayname = ssh_gssapi_displayname()) != NULL)
auth2_record_info(authctxt, "%s", displayname);
authctxt->postponed = 0;
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
return 0;
}
Authmethod method_gssapi = {
"gssapi-with-mic",
NULL,
userauth_gssapi,
&options.gss_authentication
};
#endif /* GSSAPI */
