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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* lib/krb5/krb/fast.c
*
* 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.
*
*
*
*/
#include <k5-int.h>
/*
* It is possible to support sending a request that includes both a
* FAST and normal version. This would complicate the
* pre-authentication logic significantly. You would need to maintain
* two contexts, one for FAST and one for normal use. In adition, you
* would need to manage the security issues surrounding downgrades.
* However trying FAST at all requires an armor key. Generally in
* obtaining the armor key, the client learns enough to know that FAST
* is supported. If not, the client can see FAST in the
* preauth_required error's padata and retry with FAST. So, this
* implementation does not support FAST+normal.
*
* We store the outer version of the request to use . The caller
* stores the inner version. We handle the encoding of the request
* body (and request) and provide encoded request bodies for the
* caller to use as these may be used for checksums. In the AS case
* we also evaluate whether to continue a conversation as one of the
* important questions there is the presence of a cookie.
*/
#include "fast.h"
#include "int-proto.h"
static krb5_error_code fast_armor_ap_request
(krb5_context context, struct krb5int_fast_request_state *state,
krb5_ccache ccache, krb5_data *target_realm)
{
krb5_error_code retval = 0;
krb5_creds creds, *out_creds = NULL;
krb5_auth_context authcontext = NULL;
krb5_data encoded_authenticator;
krb5_fast_armor *armor = NULL;
krb5_keyblock *subkey = NULL, *armor_key = NULL;
encoded_authenticator.data = NULL;
memset(&creds, 0, sizeof(creds));
retval = krb5_tgtname(context, target_realm, target_realm, &creds.server);
if (retval ==0)
retval = krb5_cc_get_principal(context, ccache, &creds.client);
if (retval == 0)
retval = krb5_get_credentials(context, 0, ccache, &creds, &out_creds);
if (retval == 0)
retval = krb5_mk_req_extended(context, &authcontext, AP_OPTS_USE_SUBKEY, NULL /*data*/,
out_creds, &encoded_authenticator);
if (retval == 0)
retval = krb5_auth_con_getsendsubkey(context, authcontext, &subkey);
if (retval == 0)
retval = krb5_c_fx_cf2_simple(context, subkey, "subkeyarmor",
&out_creds->keyblock, "ticketarmor", &armor_key);
if (retval == 0) {
armor = calloc(1, sizeof(krb5_fast_armor));
if (armor == NULL)
retval = ENOMEM;
}
if (retval == 0) {
armor->armor_type = KRB5_FAST_ARMOR_AP_REQUEST;
armor->armor_value = encoded_authenticator;
encoded_authenticator.data = NULL;
encoded_authenticator.length = 0;
state->armor = armor;
armor = NULL;
state->armor_key = armor_key;
armor_key = NULL;
}
krb5_free_keyblock(context, armor_key);
krb5_free_keyblock(context, subkey);
if (out_creds)
krb5_free_creds(context, out_creds);
krb5_free_cred_contents(context, &creds);
if (encoded_authenticator.data)
krb5_free_data_contents(context, &encoded_authenticator);
krb5_auth_con_free(context, authcontext);
return retval;
}
krb5_error_code
krb5int_fast_prep_req_body(krb5_context context, struct krb5int_fast_request_state *state,
krb5_kdc_req *request, krb5_data **encoded_request_body)
{
krb5_error_code retval = 0;
krb5_data *local_encoded_request_body = NULL;
assert(state != NULL);
*encoded_request_body = NULL;
if (state->armor_key == NULL) {
return encode_krb5_kdc_req_body(request, encoded_request_body);
}
state->fast_outer_request = *request;
state->fast_outer_request.padata = NULL;
if (retval == 0)
retval = encode_krb5_kdc_req_body(&state->fast_outer_request,
&local_encoded_request_body);
if (retval == 0) {
*encoded_request_body = local_encoded_request_body;
local_encoded_request_body = NULL;
}
if (local_encoded_request_body != NULL)
krb5_free_data(context, local_encoded_request_body);
return retval;
}
krb5_error_code krb5int_fast_as_armor
(krb5_context context, struct krb5int_fast_request_state *state,
krb5_gic_opt_ext *opte,
krb5_kdc_req *request)
{
krb5_error_code retval = 0;
krb5_ccache ccache = NULL;
krb5_clear_error_message(context);
if (opte->opt_private->fast_ccache_name) {
retval = krb5_cc_resolve(context, opte->opt_private->fast_ccache_name,
&ccache);
if (retval==0)
retval = fast_armor_ap_request(context, state, ccache,
krb5_princ_realm(context, request->server));
if (retval != 0) {
const char * errmsg;
errmsg = krb5_get_error_message(context, retval);
if (errmsg) {
krb5_set_error_message(context, retval, "%s constructing AP-REQ armor", errmsg);
krb5_free_error_message(context, errmsg);
}
}
}
if (ccache)
krb5_cc_close(context, ccache);
return retval;
}
krb5_error_code
krb5int_fast_prep_req (krb5_context context, struct krb5int_fast_request_state *state,
krb5_kdc_req *request,
const krb5_data *to_be_checksummed, kdc_req_encoder_proc encoder,
krb5_data **encoded_request)
{
krb5_error_code retval = 0;
krb5_pa_data *pa_array[2];
krb5_pa_data pa[2];
krb5_fast_req fast_req;
krb5_fast_armored_req *armored_req = NULL;
krb5_data *encoded_fast_req = NULL;
krb5_data *encoded_armored_req = NULL;
krb5_data *local_encoded_result = NULL;
krb5_cksumtype cksumtype;
krb5_data random_data;
char random_buf[4];
assert(state != NULL);
assert(state->fast_outer_request.padata == NULL);
memset(pa_array, 0, sizeof pa_array);
if (state->armor_key == NULL) {
return encoder(request, encoded_request);
}
/* Fill in a fresh random nonce for each inner request*/
random_data.length = 4;
random_data.data = (char *)random_buf;
retval = krb5_c_random_make_octets(context, &random_data);
if (retval == 0) {
request->nonce = 0x7fffffff & load_32_n(random_buf);
state->nonce = request->nonce;
}
fast_req.req_body = request;
if (fast_req.req_body->padata == NULL) {
fast_req.req_body->padata = calloc(1, sizeof(krb5_pa_data *));
if (fast_req.req_body->padata == NULL)
retval = ENOMEM;
}
fast_req.fast_options = state->fast_options;
if (retval == 0)
retval = encode_krb5_fast_req(&fast_req, &encoded_fast_req);
if (retval == 0) {
armored_req = calloc(1, sizeof(krb5_fast_armored_req));
if (armored_req == NULL)
retval = ENOMEM;
}
if (retval == 0)
armored_req->armor = state->armor;
if (retval == 0)
retval = krb5int_c_mandatory_cksumtype(context, state->armor_key->enctype,
&cksumtype);
if (retval ==0)
retval = krb5_c_make_checksum(context, cksumtype, state->armor_key,
KRB5_KEYUSAGE_FAST_REQ_CHKSUM, to_be_checksummed,
&armored_req->req_checksum);
if (retval == 0)
retval = krb5_encrypt_helper(context, state->armor_key,
KRB5_KEYUSAGE_FAST_ENC, encoded_fast_req,
&armored_req->enc_part);
if (retval == 0)
retval = encode_krb5_pa_fx_fast_request(armored_req, &encoded_armored_req);
if (retval==0) {
pa[0].pa_type = KRB5_PADATA_FX_FAST;
pa[0].contents = (unsigned char *) encoded_armored_req->data;
pa[0].length = encoded_armored_req->length;
pa_array[0] = &pa[0];
}
state->fast_outer_request.padata = pa_array;
if(retval == 0)
retval = encoder(&state->fast_outer_request, &local_encoded_result);
if (retval == 0) {
*encoded_request = local_encoded_result;
local_encoded_result = NULL;
}
if (encoded_armored_req)
krb5_free_data(context, encoded_armored_req);
if (armored_req) {
armored_req->armor = NULL; /*owned by state*/
krb5_free_fast_armored_req(context, armored_req);
}
if (encoded_fast_req)
krb5_free_data(context, encoded_fast_req);
if (local_encoded_result)
krb5_free_data(context, local_encoded_result);
state->fast_outer_request.padata = NULL;
return retval;
}
static krb5_error_code decrypt_fast_reply
(krb5_context context, struct krb5int_fast_request_state *state,
krb5_pa_data **in_padata,
krb5_fast_response **response)
{
krb5_error_code retval = 0;
krb5_data scratch;
krb5_enc_data *encrypted_response = NULL;
krb5_pa_data *fx_reply = NULL;
krb5_fast_response *local_resp = NULL;
assert(state != NULL);
assert(state->armor_key);
fx_reply = krb5int_find_pa_data(context, in_padata, KRB5_PADATA_FX_FAST);
if (fx_reply == NULL)
retval = KRB5_ERR_FAST_REQUIRED;
if (retval == 0) {
scratch.data = (char *) fx_reply->contents;
scratch.length = fx_reply->length;
retval = decode_krb5_pa_fx_fast_reply(&scratch, &encrypted_response);
}
scratch.data = NULL;
if (retval == 0) {
scratch.data = malloc(encrypted_response->ciphertext.length);
if (scratch.data == NULL)
retval = ENOMEM;
scratch.length = encrypted_response->ciphertext.length;
}
if (retval == 0)
retval = krb5_c_decrypt(context, state->armor_key,
KRB5_KEYUSAGE_FAST_REP, NULL,
encrypted_response, &scratch);
if (retval != 0) {
const char * errmsg;
errmsg = krb5_get_error_message(context, retval);
krb5_set_error_message(context, retval, "%s while decrypting FAST reply", errmsg);
krb5_free_error_message(context, errmsg);
}
if (retval == 0)
retval = decode_krb5_fast_response(&scratch, &local_resp);
if (retval == 0) {
if (local_resp->nonce != state->nonce) {
retval = KRB5_KDCREP_MODIFIED;
krb5_set_error_message(context, retval, "nonce modified in FAST response: KDC response modified");
}
}
if (retval == 0) {
*response = local_resp;
local_resp = NULL;
}
if (scratch.data)
free(scratch.data);
if (encrypted_response)
krb5_free_enc_data(context, encrypted_response);
if (local_resp)
krb5_free_fast_response(context, local_resp);
return retval;
}
/*
* FAST separates two concepts: the set of padata we're using to
* decide what pre-auth mechanisms to use and the set of padata we're
* making available to mechanisms in order for them to respond to an
* error. The plugin interface in March 2009 does not permit
* separating these concepts for the plugins. This function makes
* both available for future revisions to the plugin interface. It
* also re-encodes the padata from the current error as a encoded
* typed-data and puts that in the e_data field. That will allow
* existing plugins with the old interface to find the error data.
* The output parameter out_padata contains the padata from the error
* whenever padata is available (all the time with fast).
*/
krb5_error_code
krb5int_fast_process_error(krb5_context context, struct krb5int_fast_request_state *state,
krb5_error **err_replyptr , krb5_pa_data ***out_padata,
krb5_boolean *retry)
{
krb5_error_code retval = 0;
krb5_error *err_reply = *err_replyptr;
*out_padata = NULL;
*retry = 0;
if (state->armor_key) {
krb5_pa_data *fx_error_pa;
krb5_pa_data **result = NULL;
krb5_data scratch, *encoded_td = NULL;
krb5_error *fx_error = NULL;
krb5_fast_response *fast_response = NULL;
retval = decode_krb5_padata_sequence(&err_reply->e_data, &result);
if (retval == 0)
retval = decrypt_fast_reply(context, state, result, &fast_response);
if (retval) {
/*This can happen if the KDC does not understand FAST. We
* don't expect that, but treating it as the fatal error
* indicated by the KDC seems reasonable.
*/
*retry = 0;
krb5_free_pa_data(context, result);
return 0;
}
krb5_free_pa_data(context, result);
result = NULL;
if (retval == 0) {
fx_error_pa = krb5int_find_pa_data(context, fast_response->padata, KRB5_PADATA_FX_ERROR);
if (fx_error_pa == NULL) {
krb5_set_error_message(context, KRB5KDC_ERR_PREAUTH_FAILED, "Expecting FX_ERROR pa-data inside FAST container");
retval = KRB5KDC_ERR_PREAUTH_FAILED;
}
}
if (retval == 0) {
scratch.data = (char *) fx_error_pa->contents;
scratch.length = fx_error_pa->length;
retval = decode_krb5_error(&scratch, &fx_error);
}
/*
* krb5_pa_data and krb5_typed_data are safe to cast between:
* they have the same type fields in the same order.
* (krb5_preauthtype is a krb5_int32). If krb5_typed_data is
* ever changed then this will need to be a copy not a cast.
*/
if (retval == 0)
retval = encode_krb5_typed_data( (krb5_typed_data **) fast_response->padata,
&encoded_td);
if (retval == 0) {
fx_error->e_data = *encoded_td;
free(encoded_td); /*contents owned by fx_error*/
encoded_td = NULL;
krb5_free_error(context, err_reply);
*err_replyptr = fx_error;
fx_error = NULL;
*out_padata = fast_response->padata;
fast_response->padata = NULL;
/*
* If there is more than the fx_error padata, then we want
* to retry the error if a cookie is present
*/
*retry = (*out_padata)[1] != NULL;
if (krb5int_find_pa_data(context, *out_padata, KRB5_PADATA_FX_COOKIE) == NULL)
*retry = 0;
}
if (fx_error)
krb5_free_error(context, fx_error);
krb5_free_fast_response(context, fast_response);
} else { /*not FAST*/
*retry = (err_reply->e_data.length > 0);
if ((err_reply->error == KDC_ERR_PREAUTH_REQUIRED
||err_reply->error == KDC_ERR_PREAUTH_FAILED) && err_reply->e_data.length) {
krb5_pa_data **result = NULL;
retval = decode_krb5_padata_sequence(&err_reply->e_data, &result);
if (retval == 0)
if (retval == 0) {
*out_padata = result;
return 0;
}
krb5_free_pa_data(context, result);
krb5_set_error_message(context, retval,
"Error decoding padata in error reply");
return retval;
}
}
return retval;
}
krb5_error_code krb5int_fast_process_response
(krb5_context context, struct krb5int_fast_request_state *state,
krb5_kdc_rep *resp,
krb5_keyblock **strengthen_key)
{
krb5_error_code retval = 0;
krb5_fast_response *fast_response = NULL;
krb5_data *encoded_ticket = NULL;
krb5_boolean cksum_valid;
krb5_clear_error_message(context);
*strengthen_key = NULL;
if (state->armor_key == 0)
return 0;
retval = decrypt_fast_reply(context, state, resp->padata,
&fast_response);
if (retval == 0) {
if (fast_response->finished == 0) {
retval = KRB5_KDCREP_MODIFIED;
krb5_set_error_message(context, retval, "FAST response missing finish message in KDC reply");
}
}
if (retval == 0)
retval = encode_krb5_ticket(resp->ticket, &encoded_ticket);
if (retval == 0)
retval = krb5_c_verify_checksum(context, state->armor_key,
KRB5_KEYUSAGE_FAST_FINISHED,
encoded_ticket,
&fast_response->finished->ticket_checksum,
&cksum_valid);
if (retval == 0 && cksum_valid == 0) {
retval = KRB5_KDCREP_MODIFIED;
krb5_set_error_message(context, retval, "ticket modified in KDC reply");
}
if (retval == 0) {
krb5_free_principal(context, resp->client);
resp->client = fast_response->finished->client;
fast_response->finished->client = NULL;
*strengthen_key = fast_response->strengthen_key;
fast_response->strengthen_key = NULL;
krb5_free_pa_data(context, resp->padata);
resp->padata = fast_response->padata;
fast_response->padata = NULL;
}
if (fast_response)
krb5_free_fast_response(context, fast_response);
if (encoded_ticket)
krb5_free_data(context, encoded_ticket);
return retval;
}
krb5_error_code krb5int_fast_reply_key(krb5_context context,
krb5_keyblock *strengthen_key,
krb5_keyblock *existing_key,
krb5_keyblock *out_key)
{
krb5_keyblock *key = NULL;
krb5_error_code retval = 0;
krb5_free_keyblock_contents(context, out_key);
if (strengthen_key) {
retval = krb5_c_fx_cf2_simple(context, strengthen_key,
"strengthenkey", existing_key, "replykey", &key);
if (retval == 0) {
*out_key = *key;
free(key);
}
} else {
retval = krb5_copy_keyblock_contents(context, existing_key, out_key);
}
return retval;
}
krb5_error_code
krb5int_fast_make_state( krb5_context context, struct krb5int_fast_request_state **state)
{
struct krb5int_fast_request_state *local_state ;
local_state = malloc(sizeof *local_state);
if (local_state == NULL)
return ENOMEM;
memset(local_state, 0, sizeof(*local_state));
*state = local_state;
return 0;
}
void
krb5int_fast_free_state( krb5_context context, struct krb5int_fast_request_state *state)
{
/*We are responsible for none of the store in the fast_outer_req*/
krb5_free_keyblock(context, state->armor_key);
krb5_free_fast_armor(context, state->armor);
free(state);
}
krb5_pa_data * krb5int_find_pa_data
(krb5_context context, krb5_pa_data *const *padata, krb5_preauthtype pa_type)
{
krb5_pa_data * const *tmppa;
if (padata == NULL)
return NULL;
for (tmppa = padata; *tmppa != NULL; tmppa++) {
if ((*tmppa)->pa_type == pa_type)
break;
}
return *tmppa;
}
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