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https://github.com/samba-team/samba.git
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40fb810de3
We had customer problems where level 10 logs were not good enough in order to find the reason for failing dns updates. With the new debug message there's at least a chance to find out what the problem could be. Signed-off-by: Stefan Metzmacher <metze@samba.org> Reviewed-by: Andreas Schneider <asn@samba.org> Reviewed-by: Ralph Boehme <slow@samba.org>
449 lines
13 KiB
C
449 lines
13 KiB
C
/*
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Unix SMB/CIFS implementation.
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DNS server handler for signed packets
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Copyright (C) 2012 Kai Blin <kai@samba.org>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "includes.h"
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#include "system/network.h"
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#include "librpc/ndr/libndr.h"
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#include "librpc/gen_ndr/ndr_dns.h"
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#include "dns_server/dns_server.h"
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#include "libcli/util/ntstatus.h"
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#include "auth/auth.h"
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#include "auth/gensec/gensec.h"
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#undef DBGC_CLASS
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#define DBGC_CLASS DBGC_DNS
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static WERROR dns_copy_tsig(TALLOC_CTX *mem_ctx,
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struct dns_res_rec *old,
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struct dns_res_rec *new_rec)
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{
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new_rec->name = talloc_strdup(mem_ctx, old->name);
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W_ERROR_HAVE_NO_MEMORY(new_rec->name);
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new_rec->rr_type = old->rr_type;
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new_rec->rr_class = old->rr_class;
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new_rec->ttl = old->ttl;
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new_rec->length = old->length;
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new_rec->rdata.tsig_record.algorithm_name = talloc_strdup(mem_ctx,
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old->rdata.tsig_record.algorithm_name);
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W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.algorithm_name);
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new_rec->rdata.tsig_record.time_prefix = old->rdata.tsig_record.time_prefix;
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new_rec->rdata.tsig_record.time = old->rdata.tsig_record.time;
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new_rec->rdata.tsig_record.fudge = old->rdata.tsig_record.fudge;
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new_rec->rdata.tsig_record.mac_size = old->rdata.tsig_record.mac_size;
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new_rec->rdata.tsig_record.mac = talloc_memdup(mem_ctx,
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old->rdata.tsig_record.mac,
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old->rdata.tsig_record.mac_size);
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W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.mac);
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new_rec->rdata.tsig_record.original_id = old->rdata.tsig_record.original_id;
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new_rec->rdata.tsig_record.error = old->rdata.tsig_record.error;
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new_rec->rdata.tsig_record.other_size = old->rdata.tsig_record.other_size;
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new_rec->rdata.tsig_record.other_data = talloc_memdup(mem_ctx,
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old->rdata.tsig_record.other_data,
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old->rdata.tsig_record.other_size);
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W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.other_data);
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return WERR_OK;
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}
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struct dns_server_tkey *dns_find_tkey(struct dns_server_tkey_store *store,
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const char *name)
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{
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struct dns_server_tkey *tkey = NULL;
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uint16_t i = 0;
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do {
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struct dns_server_tkey *tmp_key = store->tkeys[i];
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i++;
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i %= TKEY_BUFFER_SIZE;
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if (tmp_key == NULL) {
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continue;
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}
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if (samba_dns_name_equal(name, tmp_key->name)) {
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tkey = tmp_key;
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break;
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}
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} while (i != 0);
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return tkey;
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}
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WERROR dns_verify_tsig(struct dns_server *dns,
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TALLOC_CTX *mem_ctx,
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struct dns_request_state *state,
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struct dns_name_packet *packet,
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DATA_BLOB *in)
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{
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WERROR werror;
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NTSTATUS status;
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enum ndr_err_code ndr_err;
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uint16_t i, arcount = 0;
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DATA_BLOB tsig_blob, fake_tsig_blob, sig;
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uint8_t *buffer = NULL;
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size_t buffer_len = 0, packet_len = 0;
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struct dns_server_tkey *tkey = NULL;
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struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx,
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struct dns_fake_tsig_rec);
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/* Find the first TSIG record in the additional records */
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for (i=0; i < packet->arcount; i++) {
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if (packet->additional[i].rr_type == DNS_QTYPE_TSIG) {
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break;
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}
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}
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if (i == packet->arcount) {
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/* no TSIG around */
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return WERR_OK;
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}
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/* The TSIG record needs to be the last additional record */
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if (i + 1 != packet->arcount) {
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DEBUG(1, ("TSIG record not the last additional record!\n"));
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return DNS_ERR(FORMAT_ERROR);
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}
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/* We got a TSIG, so we need to sign our reply */
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state->sign = true;
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DBG_DEBUG("Got TSIG\n");
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state->tsig = talloc_zero(state->mem_ctx, struct dns_res_rec);
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if (state->tsig == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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werror = dns_copy_tsig(state->tsig, &packet->additional[i],
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state->tsig);
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if (!W_ERROR_IS_OK(werror)) {
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return werror;
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}
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packet->arcount--;
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tkey = dns_find_tkey(dns->tkeys, state->tsig->name);
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if (tkey == NULL) {
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DBG_DEBUG("dns_find_tkey() => NOTAUTH / DNS_RCODE_BADKEY\n");
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/*
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* We must save the name for use in the TSIG error
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* response and have no choice here but to save the
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* keyname from the TSIG request.
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*/
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state->key_name = talloc_strdup(state->mem_ctx,
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state->tsig->name);
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if (state->key_name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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state->tsig_error = DNS_RCODE_BADKEY;
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return DNS_ERR(NOTAUTH);
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}
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DBG_DEBUG("dns_find_tkey() => found\n");
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/*
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* Remember the keyname that found an existing tkey, used
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* later to fetch the key with dns_find_tkey() when signing
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* and adding a TSIG record with MAC.
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*/
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state->key_name = talloc_strdup(state->mem_ctx, tkey->name);
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if (state->key_name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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/* FIXME: check TSIG here */
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if (check_rec == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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/* first build and verify check packet */
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check_rec->name = talloc_strdup(check_rec, tkey->name);
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if (check_rec->name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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check_rec->rr_class = DNS_QCLASS_ANY;
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check_rec->ttl = 0;
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check_rec->algorithm_name = talloc_strdup(check_rec, tkey->algorithm);
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if (check_rec->algorithm_name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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check_rec->time_prefix = 0;
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check_rec->time = state->tsig->rdata.tsig_record.time;
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check_rec->fudge = state->tsig->rdata.tsig_record.fudge;
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check_rec->error = 0;
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check_rec->other_size = 0;
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check_rec->other_data = NULL;
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ndr_err = ndr_push_struct_blob(&tsig_blob, mem_ctx, state->tsig,
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(ndr_push_flags_fn_t)ndr_push_dns_res_rec);
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if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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DEBUG(1, ("Failed to push packet: %s!\n",
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ndr_errstr(ndr_err)));
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return DNS_ERR(SERVER_FAILURE);
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}
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ndr_err = ndr_push_struct_blob(&fake_tsig_blob, mem_ctx, check_rec,
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(ndr_push_flags_fn_t)ndr_push_dns_fake_tsig_rec);
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if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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DEBUG(1, ("Failed to push packet: %s!\n",
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ndr_errstr(ndr_err)));
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return DNS_ERR(SERVER_FAILURE);
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}
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/* we need to work some magic here. we need to keep the input packet
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* exactly like we got it, but we need to cut off the tsig record */
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packet_len = in->length - tsig_blob.length;
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buffer_len = packet_len + fake_tsig_blob.length;
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buffer = talloc_zero_array(mem_ctx, uint8_t, buffer_len);
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if (buffer == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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memcpy(buffer, in->data, packet_len);
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memcpy(buffer + packet_len, fake_tsig_blob.data, fake_tsig_blob.length);
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sig.length = state->tsig->rdata.tsig_record.mac_size;
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sig.data = talloc_memdup(mem_ctx, state->tsig->rdata.tsig_record.mac, sig.length);
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if (sig.data == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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/* Now we also need to count down the additional record counter */
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arcount = RSVAL(buffer, 10);
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RSSVAL(buffer, 10, arcount-1);
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status = gensec_check_packet(tkey->gensec, buffer, buffer_len,
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buffer, buffer_len, &sig);
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if (NT_STATUS_EQUAL(NT_STATUS_ACCESS_DENIED, status)) {
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dump_data_dbgc(DBGC_DNS, 8, sig.data, sig.length);
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dump_data_dbgc(DBGC_DNS, 8, buffer, buffer_len);
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DBG_NOTICE("Verifying tsig failed: %s\n", nt_errstr(status));
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state->tsig_error = DNS_RCODE_BADSIG;
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return DNS_ERR(NOTAUTH);
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}
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if (!NT_STATUS_IS_OK(status)) {
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dump_data_dbgc(DBGC_DNS, 8, sig.data, sig.length);
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dump_data_dbgc(DBGC_DNS, 8, buffer, buffer_len);
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DEBUG(1, ("Verifying tsig failed: %s\n", nt_errstr(status)));
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return ntstatus_to_werror(status);
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}
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state->authenticated = true;
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DBG_DEBUG("AUTHENTICATED\n");
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return WERR_OK;
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}
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static WERROR dns_tsig_compute_mac(TALLOC_CTX *mem_ctx,
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struct dns_request_state *state,
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struct dns_name_packet *packet,
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struct dns_server_tkey *tkey,
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time_t current_time,
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DATA_BLOB *_psig)
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{
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NTSTATUS status;
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enum ndr_err_code ndr_err;
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DATA_BLOB packet_blob, tsig_blob, sig;
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uint8_t *buffer = NULL;
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uint8_t *p = NULL;
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size_t buffer_len = 0;
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struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx,
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struct dns_fake_tsig_rec);
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size_t mac_size = 0;
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if (check_rec == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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/* first build and verify check packet */
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check_rec->name = talloc_strdup(check_rec, tkey->name);
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if (check_rec->name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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check_rec->rr_class = DNS_QCLASS_ANY;
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check_rec->ttl = 0;
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check_rec->algorithm_name = talloc_strdup(check_rec, tkey->algorithm);
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if (check_rec->algorithm_name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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check_rec->time_prefix = 0;
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check_rec->time = current_time;
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check_rec->fudge = 300;
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check_rec->error = state->tsig_error;
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check_rec->other_size = 0;
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check_rec->other_data = NULL;
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ndr_err = ndr_push_struct_blob(&packet_blob, mem_ctx, packet,
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(ndr_push_flags_fn_t)ndr_push_dns_name_packet);
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if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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DEBUG(1, ("Failed to push packet: %s!\n",
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ndr_errstr(ndr_err)));
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return DNS_ERR(SERVER_FAILURE);
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}
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ndr_err = ndr_push_struct_blob(&tsig_blob, mem_ctx, check_rec,
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(ndr_push_flags_fn_t)ndr_push_dns_fake_tsig_rec);
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if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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DEBUG(1, ("Failed to push packet: %s!\n",
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ndr_errstr(ndr_err)));
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return DNS_ERR(SERVER_FAILURE);
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}
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if (state->tsig != NULL) {
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mac_size = state->tsig->rdata.tsig_record.mac_size;
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}
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buffer_len = mac_size;
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buffer_len += packet_blob.length;
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if (buffer_len < packet_blob.length) {
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return WERR_INVALID_PARAMETER;
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}
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buffer_len += tsig_blob.length;
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if (buffer_len < tsig_blob.length) {
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return WERR_INVALID_PARAMETER;
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}
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buffer = talloc_zero_array(mem_ctx, uint8_t, buffer_len);
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if (buffer == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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p = buffer;
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/*
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* RFC 2845 "4.2 TSIG on Answers", how to lay out the buffer
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* that we're going to sign:
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* 1. MAC of request (if present)
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* 2. Outgoing packet
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* 3. TSIG record
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*/
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if (mac_size > 0) {
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memcpy(p, state->tsig->rdata.tsig_record.mac, mac_size);
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p += mac_size;
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}
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memcpy(p, packet_blob.data, packet_blob.length);
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p += packet_blob.length;
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memcpy(p, tsig_blob.data, tsig_blob.length);
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status = gensec_sign_packet(tkey->gensec, mem_ctx, buffer, buffer_len,
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buffer, buffer_len, &sig);
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if (!NT_STATUS_IS_OK(status)) {
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return ntstatus_to_werror(status);
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}
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*_psig = sig;
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return WERR_OK;
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}
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WERROR dns_sign_tsig(struct dns_server *dns,
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TALLOC_CTX *mem_ctx,
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struct dns_request_state *state,
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struct dns_name_packet *packet,
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uint16_t error)
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{
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WERROR werror;
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time_t current_time = time(NULL);
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struct dns_res_rec *tsig = NULL;
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DATA_BLOB sig = (DATA_BLOB) {
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.data = NULL,
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.length = 0
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};
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tsig = talloc_zero(mem_ctx, struct dns_res_rec);
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if (tsig == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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if (state->tsig_error == DNS_RCODE_OK) {
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struct dns_server_tkey *tkey = dns_find_tkey(
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dns->tkeys, state->key_name);
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if (tkey == NULL) {
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DBG_WARNING("dns_find_tkey() => NULL)\n");
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return DNS_ERR(SERVER_FAILURE);
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}
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werror = dns_tsig_compute_mac(mem_ctx, state, packet,
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tkey, current_time, &sig);
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DBG_DEBUG("dns_tsig_compute_mac() => %s\n", win_errstr(werror));
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if (!W_ERROR_IS_OK(werror)) {
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return werror;
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}
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}
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tsig->name = talloc_strdup(tsig, state->key_name);
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if (tsig->name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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tsig->rr_class = DNS_QCLASS_ANY;
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tsig->rr_type = DNS_QTYPE_TSIG;
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tsig->ttl = 0;
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tsig->length = UINT16_MAX;
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tsig->rdata.tsig_record.algorithm_name = talloc_strdup(tsig, "gss-tsig");
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if (tsig->rdata.tsig_record.algorithm_name == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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tsig->rdata.tsig_record.time_prefix = 0;
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tsig->rdata.tsig_record.time = current_time;
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tsig->rdata.tsig_record.fudge = 300;
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tsig->rdata.tsig_record.error = state->tsig_error;
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tsig->rdata.tsig_record.original_id = packet->id;
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tsig->rdata.tsig_record.other_size = 0;
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tsig->rdata.tsig_record.other_data = NULL;
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if (sig.length > 0) {
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tsig->rdata.tsig_record.mac_size = sig.length;
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tsig->rdata.tsig_record.mac = talloc_memdup(tsig, sig.data, sig.length);
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if (tsig->rdata.tsig_record.mac == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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}
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DBG_DEBUG("sig.length=%zu\n", sig.length);
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if (packet->arcount == 0) {
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packet->additional = talloc_zero(mem_ctx, struct dns_res_rec);
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if (packet->additional == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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}
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packet->additional = talloc_realloc(mem_ctx, packet->additional,
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struct dns_res_rec,
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packet->arcount + 1);
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if (packet->additional == NULL) {
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return WERR_NOT_ENOUGH_MEMORY;
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}
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werror = dns_copy_tsig(mem_ctx, tsig,
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&packet->additional[packet->arcount]);
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DBG_DEBUG("dns_copy_tsig() => %s\n", win_errstr(werror));
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if (!W_ERROR_IS_OK(werror)) {
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return werror;
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}
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packet->arcount++;
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return WERR_OK;
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}
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