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/*
Unix SMB/CIFS implementation.
DNS server handler for signed packets
Copyright (C) 2012 Kai Blin <kai@samba.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
#include "lib/crypto/hmacmd5.h"
#include "system/network.h"
#include "librpc/ndr/libndr.h"
#include "librpc/gen_ndr/ndr_dns.h"
#include "dns_server/dns_server.h"
#include "libcli/util/ntstatus.h"
#include "auth/auth.h"
#include "auth/gensec/gensec.h"
struct dns_server_tkey *dns_find_tkey(struct dns_server_tkey_store *store,
const char *name)
{
struct dns_server_tkey *tkey = NULL;
uint16_t i = 0;
do {
struct dns_server_tkey *tmp_key = store->tkeys[i];
i++;
i %= TKEY_BUFFER_SIZE;
if (tmp_key == NULL) {
continue;
}
if (dns_name_equal(name, tmp_key->name)) {
tkey = tmp_key;
break;
}
} while (i != 0);
return tkey;
}
WERROR dns_sign_tsig(struct dns_server *dns,
TALLOC_CTX *mem_ctx,
struct dns_request_state *state,
struct dns_name_packet *packet,
uint16_t error)
{
WERROR werror;
NTSTATUS status;
enum ndr_err_code ndr_err;
time_t current_time = time(NULL);
DATA_BLOB packet_blob, tsig_blob, sig;
uint8_t *buffer = NULL;
size_t buffer_len = 0;
struct dns_server_tkey * tkey = NULL;
struct dns_res_rec *tsig = talloc_zero(mem_ctx, struct dns_res_rec);
struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx,
struct dns_fake_tsig_rec);
if (tsig == NULL) {
return WERR_NOMEM;
}
if (check_rec == NULL) {
return WERR_NOMEM;
}
tkey = dns_find_tkey(dns->tkeys, state->key_name);
if (tkey == NULL) {
/* FIXME: read up on what to do when we can't find a key */
return WERR_OK;
}
/* first build and verify check packet */
check_rec->name = talloc_strdup(check_rec, tkey->name);
if (check_rec->name == NULL) {
return WERR_NOMEM;
}
check_rec->rr_class = DNS_QCLASS_ANY;
check_rec->ttl = 0;
check_rec->algorithm_name = talloc_strdup(check_rec, tkey->algorithm);
if (check_rec->algorithm_name == NULL) {
return WERR_NOMEM;
}
check_rec->time_prefix = 0;
check_rec->time = current_time;
check_rec->fudge = 300;
check_rec->error = state->tsig_error;
check_rec->other_size = 0;
check_rec->other_data = NULL;
ndr_err = ndr_push_struct_blob(&packet_blob, mem_ctx, packet,
(ndr_push_flags_fn_t)ndr_push_dns_name_packet);
if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
DEBUG(1, ("Failed to push packet: %s!\n",
ndr_errstr(ndr_err)));
return DNS_ERR(SERVER_FAILURE);
}
ndr_err = ndr_push_struct_blob(&tsig_blob, mem_ctx, check_rec,
(ndr_push_flags_fn_t)ndr_push_dns_fake_tsig_rec);
if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
DEBUG(1, ("Failed to push packet: %s!\n",
ndr_errstr(ndr_err)));
return DNS_ERR(SERVER_FAILURE);
}
buffer_len = packet_blob.length + tsig_blob.length;
buffer = talloc_zero_array(mem_ctx, uint8_t, buffer_len);
if (buffer == NULL) {
return WERR_NOMEM;
}
memcpy(buffer, packet_blob.data, packet_blob.length);
memcpy(buffer+packet_blob.length, tsig_blob.data, tsig_blob.length);
status = gensec_sign_packet(tkey->gensec, mem_ctx, buffer, buffer_len,
buffer, buffer_len, &sig);
if (!NT_STATUS_IS_OK(status)) {
return ntstatus_to_werror(status);
}
tsig->name = talloc_strdup(tsig, check_rec->name);
if (tsig->name == NULL) {
return WERR_NOMEM;
}
tsig->rr_class = check_rec->rr_class;
tsig->rr_type = DNS_QTYPE_TSIG;
tsig->ttl = 0;
tsig->length = UINT16_MAX;
tsig->rdata.tsig_record.algorithm_name = talloc_strdup(tsig,
check_rec->algorithm_name);
tsig->rdata.tsig_record.time_prefix = check_rec->time_prefix;
tsig->rdata.tsig_record.time = check_rec->time;
tsig->rdata.tsig_record.fudge = check_rec->fudge;
tsig->rdata.tsig_record.error = state->tsig_error;
tsig->rdata.tsig_record.original_id = packet->id;
tsig->rdata.tsig_record.other_size = 0;
tsig->rdata.tsig_record.other_data = NULL;
tsig->rdata.tsig_record.mac_size = sig.length;
tsig->rdata.tsig_record.mac = talloc_memdup(tsig, sig.data, sig.length);
if (packet->arcount == 0) {
packet->additional = talloc_zero(mem_ctx, struct dns_res_rec);
if (packet->additional == NULL) {
return WERR_NOMEM;
}
}
packet->additional = talloc_realloc(mem_ctx, packet->additional,
struct dns_res_rec,
packet->arcount + 1);
if (packet->additional == NULL) {
return WERR_NOMEM;
}
werror = dns_copy_tsig(mem_ctx, tsig,
&packet->additional[packet->arcount]);
if (!W_ERROR_IS_OK(werror)) {
return werror;
}
packet->arcount++;
return WERR_OK;
}
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