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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* kdc/kdc_preauth_ec.c - Encrypted challenge kdcpreauth module */
/*
* Copyright (C) 2009 by the Massachusetts Institute of Technology.
* All rights reserved.
*
* Export of this software from the United States of America may
* require a specific license from the United States Government.
* It is the responsibility of any person or organization contemplating
* export to obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
/*
* Implement Encrypted Challenge fast factor from
* draft-ietf-krb-wg-preauth-framework
*/
#include <k5-int.h>
#include <krb5/kdcpreauth_plugin.h>
#include "kdc_util.h"
static void
ec_edata(krb5_context context, krb5_kdc_req *request,
krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock,
krb5_kdcpreauth_moddata moddata, krb5_preauthtype pa_type,
krb5_kdcpreauth_edata_respond_fn respond, void *arg)
{
krb5_keyblock *armor_key = cb->fast_armor(context, rock);
/* Encrypted challenge only works with FAST, and requires a client key. */
if (armor_key == NULL || !cb->have_client_keys(context, rock))
(*respond)(arg, ENOENT, NULL);
else
(*respond)(arg, 0, NULL);
}
static void
ec_verify(krb5_context context, krb5_data *req_pkt, krb5_kdc_req *request,
krb5_enc_tkt_part *enc_tkt_reply, krb5_pa_data *data,
krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock,
krb5_kdcpreauth_moddata moddata,
krb5_kdcpreauth_verify_respond_fn respond, void *arg)
{
krb5_error_code retval = 0;
krb5_timestamp now;
krb5_enc_data *enc = NULL;
krb5_data scratch, plain;
krb5_keyblock *armor_key = cb->fast_armor(context, rock);
krb5_pa_enc_ts *ts = NULL;
krb5_keyblock *client_keys = NULL;
krb5_keyblock *challenge_key = NULL;
krb5_keyblock *kdc_challenge_key;
krb5_kdcpreauth_modreq modreq = NULL;
int i = 0;
plain.data = NULL;
if (armor_key == NULL) {
retval = ENOENT;
k5_setmsg(context, ENOENT,
_("Encrypted Challenge used outside of FAST tunnel"));
}
scratch.data = (char *) data->contents;
scratch.length = data->length;
if (retval == 0)
retval = decode_krb5_enc_data(&scratch, &enc);
if (retval == 0) {
plain.data = malloc(enc->ciphertext.length);
plain.length = enc->ciphertext.length;
if (plain.data == NULL)
retval = ENOMEM;
}
if (retval == 0)
retval = cb->client_keys(context, rock, &client_keys);
if (retval == 0) {
for (i = 0; client_keys[i].enctype&& (retval == 0); i++ ) {
retval = krb5_c_fx_cf2_simple(context,
armor_key, "clientchallengearmor",
&client_keys[i], "challengelongterm",
&challenge_key);
if (retval == 0)
retval = krb5_c_decrypt(context, challenge_key,
KRB5_KEYUSAGE_ENC_CHALLENGE_CLIENT,
NULL, enc, &plain);
if (challenge_key)
krb5_free_keyblock(context, challenge_key);
challenge_key = NULL;
if (retval == 0)
break;
/*We failed to decrypt. Try next key*/
retval = 0;
}
if (client_keys[i].enctype == 0) {
retval = KRB5KDC_ERR_PREAUTH_FAILED;
k5_setmsg(context, retval,
_("Incorrect password in encrypted challenge"));
}
}
if (retval == 0)
retval = decode_krb5_pa_enc_ts(&plain, &ts);
if (retval == 0)
retval = krb5_timeofday(context, &now);
if (retval == 0) {
if (labs(now-ts->patimestamp) < context->clockskew) {
enc_tkt_reply->flags |= TKT_FLG_PRE_AUTH;
/*
* If this fails, we won't generate a reply to the client. That
* may cause the client to fail, but at this point the KDC has
* considered this a success, so the return value is ignored.
*/
if (krb5_c_fx_cf2_simple(context, armor_key, "kdcchallengearmor",
&client_keys[i], "challengelongterm",
&kdc_challenge_key) == 0)
modreq = (krb5_kdcpreauth_modreq)kdc_challenge_key;
} else { /*skew*/
retval = KRB5KRB_AP_ERR_SKEW;
}
}
cb->free_keys(context, rock, client_keys);
if (plain.data)
free(plain.data);
if (enc)
krb5_free_enc_data(context, enc);
if (ts)
krb5_free_pa_enc_ts(context, ts);
(*respond)(arg, retval, modreq, NULL, NULL);
}
static krb5_error_code
ec_return(krb5_context context, krb5_pa_data *padata, krb5_data *req_pkt,
krb5_kdc_req *request, krb5_kdc_rep *reply,
krb5_keyblock *encrypting_key, krb5_pa_data **send_pa,
krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock,
krb5_kdcpreauth_moddata moddata, krb5_kdcpreauth_modreq modreq)
{
krb5_error_code retval = 0;
krb5_keyblock *challenge_key = (krb5_keyblock *)modreq;
krb5_pa_enc_ts ts;
krb5_data *plain = NULL;
krb5_enc_data enc;
krb5_data *encoded = NULL;
krb5_pa_data *pa = NULL;
if (challenge_key == NULL)
return 0;
enc.ciphertext.data = NULL; /* In case of error pass through */
retval = krb5_us_timeofday(context, &ts.patimestamp, &ts.pausec);
if (retval == 0)
retval = encode_krb5_pa_enc_ts(&ts, &plain);
if (retval == 0)
retval = krb5_encrypt_helper(context, challenge_key,
KRB5_KEYUSAGE_ENC_CHALLENGE_KDC,
plain, &enc);
if (retval == 0)
retval = encode_krb5_enc_data(&enc, &encoded);
if (retval == 0) {
pa = calloc(1, sizeof(krb5_pa_data));
if (pa == NULL)
retval = ENOMEM;
}
if (retval == 0) {
pa->pa_type = KRB5_PADATA_ENCRYPTED_CHALLENGE;
pa->contents = (unsigned char *) encoded->data;
pa->length = encoded->length;
encoded->data = NULL;
*send_pa = pa;
pa = NULL;
}
if (challenge_key)
krb5_free_keyblock(context, challenge_key);
if (encoded)
krb5_free_data(context, encoded);
if (plain)
krb5_free_data(context, plain);
if (enc.ciphertext.data)
krb5_free_data_contents(context, &enc.ciphertext);
return retval;
}
static krb5_preauthtype ec_types[] = {
KRB5_PADATA_ENCRYPTED_CHALLENGE, 0};
krb5_error_code
kdcpreauth_encrypted_challenge_initvt(krb5_context context, int maj_ver,
int min_ver, krb5_plugin_vtable vtable)
{
krb5_kdcpreauth_vtable vt;
if (maj_ver != 1)
return KRB5_PLUGIN_VER_NOTSUPP;
vt = (krb5_kdcpreauth_vtable)vtable;
vt->name = "encrypted_challenge";
vt->pa_type_list = ec_types;
vt->edata = ec_edata;
vt->verify = ec_verify;
vt->return_padata = ec_return;
return 0;
}
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