/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* kdc/tgs_policy.c */
/*
* Copyright (C) 2012 by the Massachusetts Institute of Technology.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * 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 COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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
* COPYRIGHT HOLDER OR CONTRIBUTORS 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 "k5-int.h"
#include "kdc_util.h"
/*
* Routines that validate a TGS request; checks a lot of things. :-)
*
* Returns a Kerberos protocol error number, which is _not_ the same
* as a com_err error number!
*/
struct tgsflagrule {
krb5_flags reqflags; /* Flag(s) in TGS-REQ */
krb5_flags checkflag; /* Flags to check against */
char *status; /* Status string */
int err; /* Protocol error code */
};
/* Service principal TGS policy checking functions */
typedef int (check_tgs_svc_pol_fn)(krb5_kdc_req *, krb5_db_entry,
krb5_ticket *, krb5_timestamp,
const char **);
static check_tgs_svc_pol_fn check_tgs_svc_deny_opts;
static check_tgs_svc_pol_fn check_tgs_svc_deny_all;
static check_tgs_svc_pol_fn check_tgs_svc_reqd_flags;
static check_tgs_svc_pol_fn check_tgs_svc_time;
static check_tgs_svc_pol_fn * const svc_pol_fns[] = {
check_tgs_svc_deny_opts, check_tgs_svc_deny_all, check_tgs_svc_reqd_flags,
check_tgs_svc_time
};
static const struct tgsflagrule tgsflagrules[] = {
{ KDC_OPT_FORWARDED, TKT_FLG_FORWARDABLE,
"TGT NOT FORWARDABLE", KDC_ERR_BADOPTION },
{ KDC_OPT_PROXY, TKT_FLG_PROXIABLE,
"TGT NOT PROXIABLE", KDC_ERR_BADOPTION },
{ (KDC_OPT_ALLOW_POSTDATE | KDC_OPT_POSTDATED), TKT_FLG_MAY_POSTDATE,
"TGT NOT POSTDATABLE", KDC_ERR_BADOPTION },
{ KDC_OPT_VALIDATE, TKT_FLG_INVALID,
"VALIDATE VALID TICKET", KDC_ERR_BADOPTION },
{ KDC_OPT_RENEW, TKT_FLG_RENEWABLE,
"TICKET NOT RENEWABLE", KDC_ERR_BADOPTION }
};
/*
* Some TGS-REQ options require that the ticket have corresponding flags set.
*/
static int
check_tgs_opts(krb5_kdc_req *req, krb5_ticket *tkt, const char **status)
{
size_t i;
size_t nrules = sizeof(tgsflagrules) / sizeof(tgsflagrules[0]);
const struct tgsflagrule *r;
for (i = 0; i < nrules; i++) {
r = &tgsflagrules[i];
if (r->reqflags & req->kdc_options) {
if (!(r->checkflag & tkt->enc_part2->flags)) {
*status = r->status;
return r->err;
}
}
}
return 0;
}
static const struct tgsflagrule svcdenyrules[] = {
{ KDC_OPT_RENEWABLE, KRB5_KDB_DISALLOW_RENEWABLE,
"NON-RENEWABLE TICKET", KDC_ERR_POLICY },
{ KDC_OPT_ALLOW_POSTDATE, KRB5_KDB_DISALLOW_POSTDATED,
"NON-POSTDATABLE TICKET", KDC_ERR_CANNOT_POSTDATE },
{ KDC_OPT_ENC_TKT_IN_SKEY, KRB5_KDB_DISALLOW_DUP_SKEY,
"DUP_SKEY DISALLOWED", KDC_ERR_POLICY }
};
/*
* A service principal can forbid some TGS-REQ options.
*/
static int
check_tgs_svc_deny_opts(krb5_kdc_req *req, krb5_db_entry server,
krb5_ticket *tkt, krb5_timestamp kdc_time,
const char **status)
{
size_t i;
size_t nrules = sizeof(svcdenyrules) / sizeof(svcdenyrules[0]);
const struct tgsflagrule *r;
for (i = 0; i < nrules; i++) {
r = &svcdenyrules[i];
if (!(r->reqflags & req->kdc_options))
continue;
if (r->checkflag & server.attributes) {
*status = r->status;
return r->err;
}
}
return 0;
}
/*
* A service principal can deny all TGS-REQs for it.
*/
static int
check_tgs_svc_deny_all(krb5_kdc_req *req, krb5_db_entry server,
krb5_ticket *tkt, krb5_timestamp kdc_time,
const char **status)
{
if (server.attributes & KRB5_KDB_DISALLOW_ALL_TIX) {
*status = "SERVER LOCKED OUT";
return KDC_ERR_S_PRINCIPAL_UNKNOWN;
}
if ((server.attributes & KRB5_KDB_DISALLOW_SVR) &&
!(req->kdc_options & KDC_OPT_ENC_TKT_IN_SKEY)) {
*status = "SERVER NOT ALLOWED";
return KDC_ERR_MUST_USE_USER2USER;
}
if (server.attributes & KRB5_KDB_DISALLOW_TGT_BASED) {
if (krb5_is_tgs_principal(tkt->server)) {
*status = "TGT BASED NOT ALLOWED";
return KDC_ERR_POLICY;
}
}
return 0;
}
/*
* A service principal can require certain TGT flags.
*/
static int
check_tgs_svc_reqd_flags(krb5_kdc_req *req, krb5_db_entry server,
krb5_ticket *tkt,
krb5_timestamp kdc_time, const char **status)
{
if (server.attributes & KRB5_KDB_REQUIRES_HW_AUTH) {
if (!(tkt->enc_part2->flags & TKT_FLG_HW_AUTH)) {
*status = "NO HW PREAUTH";
return KRB_ERR_GENERIC;
}
}
if (server.attributes & KRB5_KDB_REQUIRES_PRE_AUTH) {
if (!(tkt->enc_part2->flags & TKT_FLG_PRE_AUTH)) {
*status = "NO PREAUTH";
return KRB_ERR_GENERIC;
}
}
return 0;
}
static int
check_tgs_svc_time(krb5_kdc_req *req, krb5_db_entry server, krb5_ticket *tkt,
krb5_timestamp kdc_time, const char **status)
{
if (server.expiration && ts_after(kdc_time, server.expiration)) {
*status = "SERVICE EXPIRED";
return KDC_ERR_SERVICE_EXP;
}
return 0;
}
static int
check_tgs_svc_policy(krb5_kdc_req *req, krb5_db_entry server, krb5_ticket *tkt,
krb5_timestamp kdc_time, const char **status)
{
int errcode;
size_t i;
size_t nfns = sizeof(svc_pol_fns) / sizeof(svc_pol_fns[0]);
for (i = 0; i < nfns; i++) {
errcode = svc_pol_fns[i](req, server, tkt, kdc_time, status);
if (errcode != 0)
return errcode;
}
return 0;
}
/*
* Check header ticket timestamps against the current time.
*/
static int
check_tgs_times(krb5_kdc_req *req, krb5_ticket_times *times,
krb5_timestamp kdc_time, const char **status)
{
krb5_timestamp starttime;
/* For validating a postdated ticket, check the start time vs. the
KDC time. */
if (req->kdc_options & KDC_OPT_VALIDATE) {
starttime = times->starttime ? times->starttime : times->authtime;
if (ts_after(starttime, kdc_time)) {
*status = "NOT_YET_VALID";
return KRB_AP_ERR_TKT_NYV;
}
}
/*
* Check the renew_till time. The endtime was already
* been checked in the initial authentication check.
*/
if ((req->kdc_options & KDC_OPT_RENEW) &&
ts_after(kdc_time, times->renew_till)) {
*status = "TKT_EXPIRED";
return KRB_AP_ERR_TKT_EXPIRED;
}
return 0;
}
static int
check_tgs_s4u2proxy(kdc_realm_t *kdc_active_realm,
krb5_kdc_req *req, const char **status)
{
if (req->kdc_options & KDC_OPT_CNAME_IN_ADDL_TKT) {
/* Check that second ticket is in request. */
if (!req->second_ticket || !req->second_ticket[0]) {
*status = "NO_2ND_TKT";
return KDC_ERR_BADOPTION;
}
}
return 0;
}
static int
check_tgs_u2u(kdc_realm_t *kdc_active_realm,
krb5_kdc_req *req, const char **status)
{
if (req->kdc_options & KDC_OPT_ENC_TKT_IN_SKEY) {
/* Check that second ticket is in request. */
if (!req->second_ticket || !req->second_ticket[0]) {
*status = "NO_2ND_TKT";
return KDC_ERR_BADOPTION;
}
/* Check that second ticket is a TGT. */
if (!krb5_principal_compare(kdc_context,
req->second_ticket[0]->server,
tgs_server)) {
*status = "2ND_TKT_NOT_TGS";
return KDC_ERR_POLICY;
}
}
return 0;
}
/*
* Some TGS-REQ options allow for a non-TGS principal in the ticket. Do some
* checks that are peculiar to these cases. (e.g., ticket service principal
* matches requested service principal)
*/
static int
check_tgs_nontgt(kdc_realm_t *kdc_active_realm,
krb5_kdc_req *req, krb5_ticket *tkt, const char **status)
{
if (!krb5_principal_compare(kdc_context, tkt->server, req->server)) {
*status = "SERVER DIDN'T MATCH TICKET FOR RENEW/FORWARD/ETC";
return KDC_ERR_SERVER_NOMATCH;
}
/* Cannot proxy ticket granting tickets. */
if ((req->kdc_options & KDC_OPT_PROXY) &&
krb5_is_tgs_principal(req->server)) {
*status = "CAN'T PROXY TGT";
return KDC_ERR_BADOPTION;
}
return 0;
}
/*
* Do some checks for a normal TGS-REQ (where the ticket service must be a TGS
* principal).
*/
static int
check_tgs_tgt(kdc_realm_t *kdc_active_realm, krb5_kdc_req *req,
krb5_ticket *tkt, const char **status)
{
/* Make sure it's a TGS principal. */
if (!krb5_is_tgs_principal(tkt->server)) {
*status = "BAD TGS SERVER NAME";
return KRB_AP_ERR_NOT_US;
}
/* TGS principal second component must match service realm. */
if (!data_eq(*krb5_princ_component(kdc_context, tkt->server, 1),
*krb5_princ_realm(kdc_context, req->server))) {
*status = "BAD TGS SERVER INSTANCE";
return KRB_AP_ERR_NOT_US;
}
return 0;
}
int
validate_tgs_request(kdc_realm_t *kdc_active_realm,
krb5_kdc_req *request, krb5_db_entry server,
krb5_ticket *ticket, krb5_timestamp kdc_time,
const char **status, krb5_pa_data ***e_data)
{
int errcode;
krb5_error_code ret;
/* Depends only on request and ticket. */
errcode = check_tgs_opts(request, ticket, status);
if (errcode != 0)
return errcode;
/* Depends only on request, ticket times, and current time. */
errcode = check_tgs_times(request, &ticket->enc_part2->times, kdc_time,
status);
if (errcode != 0)
return errcode;
errcode = check_tgs_svc_policy(request, server, ticket, kdc_time, status);
if (errcode != 0)
return errcode;
if (request->kdc_options & NON_TGT_OPTION)
errcode = check_tgs_nontgt(kdc_active_realm, request, ticket, status);
else
errcode = check_tgs_tgt(kdc_active_realm, request, ticket, status);
if (errcode != 0)
return errcode;
/* Check the hot list */
if (check_hot_list(ticket)) {
*status = "HOT_LIST";
return(KRB_AP_ERR_REPEAT);
}
errcode = check_tgs_u2u(kdc_active_realm, request, status);
if (errcode != 0)
return errcode;
errcode = check_tgs_s4u2proxy(kdc_active_realm, request, status);
if (errcode != 0)
return errcode;
if (check_anon(kdc_active_realm, ticket->enc_part2->client,
request->server) != 0) {
*status = "ANONYMOUS NOT ALLOWED";
return(KDC_ERR_POLICY);
}
/* Perform KDB module policy checks. */
ret = krb5_db_check_policy_tgs(kdc_context, request, &server,
ticket, status, e_data);
if (ret && ret != KRB5_PLUGIN_OP_NOTSUPP)
return errcode_to_protocol(ret);
return 0;
}