source4/dns_server/dns_crypto.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    DNS server handler for signed packets
   5
   6    Copyright (C) 2012 Kai Blin  <kai@samba.org>
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "includes.h"
  23 #include "lib/crypto/hmacmd5.h"
  24 #include "system/network.h"
  25 #include "librpc/ndr/libndr.h"
  26 #include "librpc/gen_ndr/ndr_dns.h"
  27 #include "dns_server/dns_server.h"
  28 #include "libcli/util/ntstatus.h"
  29 #include "auth/auth.h"
  30 #include "auth/gensec/gensec.h"
  31
  32 static WERROR dns_copy_tsig(TALLOC_CTX *mem_ctx,
  33                             struct dns_res_rec *old,
  34                             struct dns_res_rec *new_rec)
  35 {
  36         new_rec->name = talloc_strdup(mem_ctx, old->name);
  37         W_ERROR_HAVE_NO_MEMORY(new_rec->name);
  38
  39         new_rec->rr_type = old->rr_type;
  40         new_rec->rr_class = old->rr_class;
  41         new_rec->ttl = old->ttl;
  42         new_rec->length = old->length;
  43         new_rec->rdata.tsig_record.algorithm_name = talloc_strdup(mem_ctx,
  44                                 old->rdata.tsig_record.algorithm_name);
  45         W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.algorithm_name);
  46
  47         new_rec->rdata.tsig_record.time_prefix = old->rdata.tsig_record.time_prefix;
  48         new_rec->rdata.tsig_record.time = old->rdata.tsig_record.time;
  49         new_rec->rdata.tsig_record.fudge = old->rdata.tsig_record.fudge;
  50         new_rec->rdata.tsig_record.mac_size = old->rdata.tsig_record.mac_size;
  51         new_rec->rdata.tsig_record.mac = talloc_memdup(mem_ctx,
  52                                         old->rdata.tsig_record.mac,
  53                                         old->rdata.tsig_record.mac_size);
  54         W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.mac);
  55
  56         new_rec->rdata.tsig_record.original_id = old->rdata.tsig_record.original_id;
  57         new_rec->rdata.tsig_record.error = old->rdata.tsig_record.error;
  58         new_rec->rdata.tsig_record.other_size = old->rdata.tsig_record.other_size;
  59         new_rec->rdata.tsig_record.other_data = talloc_memdup(mem_ctx,
  60                                         old->rdata.tsig_record.other_data,
  61                                         old->rdata.tsig_record.other_size);
  62         W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.other_data);
  63
  64         return WERR_OK;
  65 }
  66
  67 struct dns_server_tkey *dns_find_tkey(struct dns_server_tkey_store *store,
  68                                       const char *name)
  69 {
  70         struct dns_server_tkey *tkey = NULL;
  71         uint16_t i = 0;
  72
  73         do {
  74                 struct dns_server_tkey *tmp_key = store->tkeys[i];
  75
  76                 i++;
  77                 i %= TKEY_BUFFER_SIZE;
  78
  79                 if (tmp_key == NULL) {
  80                         continue;
  81                 }
  82                 if (dns_name_equal(name, tmp_key->name)) {
  83                         tkey = tmp_key;
  84                         break;
  85                 }
  86         } while (i != 0);
  87
  88         return tkey;
  89 }
  90
  91 WERROR dns_verify_tsig(struct dns_server *dns,
  92                        TALLOC_CTX *mem_ctx,
  93                        struct dns_request_state *state,
  94                        struct dns_name_packet *packet)
  95 {
  96         WERROR werror;
  97         NTSTATUS status;
  98         enum ndr_err_code ndr_err;
  99         bool found_tsig = false;
 100         uint16_t i;
 101         DATA_BLOB packet_blob, tsig_blob, sig;
 102         uint8_t *buffer = NULL;
 103         size_t buffer_len = 0;
 104         struct dns_server_tkey *tkey = NULL;
 105         struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx,
 106                         struct dns_fake_tsig_rec);
 107
 108
 109         /* Find the first TSIG record in the additional records */
 110         for (i=0; i < packet->arcount; i++) {
 111                 if (packet->additional[i].rr_type == DNS_QTYPE_TSIG) {
 112                         found_tsig = true;
 113                         break;
 114                 }
 115         }
 116
 117         if (!found_tsig) {
 118                 return WERR_OK;
 119         }
 120
 121         /* The TSIG record needs to be the last additional record */
 122         if (found_tsig && i + 1 != packet->arcount) {
 123                 DEBUG(0, ("TSIG record not the last additional record!\n"));
 124                 return DNS_ERR(FORMAT_ERROR);
 125         }
 126
 127         /* We got a TSIG, so we need to sign our reply */
 128         state->sign = true;
 129
 130         state->tsig = talloc_zero(mem_ctx, struct dns_res_rec);
 131         if (state->tsig == NULL) {
 132                 return WERR_NOMEM;
 133         }
 134
 135         werror = dns_copy_tsig(state->tsig, &packet->additional[i],
 136                                state->tsig);
 137         if (!W_ERROR_IS_OK(werror)) {
 138                 return werror;
 139         }
 140
 141         packet->arcount--;
 142
 143         tkey = dns_find_tkey(dns->tkeys, state->tsig->name);
 144         if (tkey == NULL) {
 145                 state->tsig_error = DNS_RCODE_BADKEY;
 146                 return DNS_ERR(NOTAUTH);
 147         }
 148
 149         /* FIXME: check TSIG here */
 150         if (check_rec == NULL) {
 151                 return WERR_NOMEM;
 152         }
 153
 154         /* first build and verify check packet */
 155         check_rec->name = talloc_strdup(check_rec, tkey->name);
 156         if (check_rec->name == NULL) {
 157                 return WERR_NOMEM;
 158         }
 159         check_rec->rr_class = DNS_QCLASS_ANY;
 160         check_rec->ttl = 0;
 161         check_rec->algorithm_name = talloc_strdup(check_rec, tkey->algorithm);
 162         if (check_rec->algorithm_name == NULL) {
 163                 return WERR_NOMEM;
 164         }
 165         check_rec->time_prefix = 0;
 166         check_rec->time = state->tsig->rdata.tsig_record.time;
 167         check_rec->fudge = state->tsig->rdata.tsig_record.fudge;
 168         check_rec->error = 0;
 169         check_rec->other_size = 0;
 170         check_rec->other_data = NULL;
 171
 172         ndr_err = ndr_push_struct_blob(&packet_blob, mem_ctx, packet,
 173                 (ndr_push_flags_fn_t)ndr_push_dns_name_packet);
 174         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 175                 DEBUG(1, ("Failed to push packet: %s!\n",
 176                           ndr_errstr(ndr_err)));
 177                 return DNS_ERR(SERVER_FAILURE);
 178         }
 179
 180         ndr_err = ndr_push_struct_blob(&tsig_blob, mem_ctx, check_rec,
 181                 (ndr_push_flags_fn_t)ndr_push_dns_fake_tsig_rec);
 182         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 183                 DEBUG(1, ("Failed to push packet: %s!\n",
 184                           ndr_errstr(ndr_err)));
 185                 return DNS_ERR(SERVER_FAILURE);
 186         }
 187
 188         buffer_len = packet_blob.length + tsig_blob.length;
 189         buffer = talloc_zero_array(mem_ctx, uint8_t, buffer_len);
 190         if (buffer == NULL) {
 191                 return WERR_NOMEM;
 192         }
 193
 194         memcpy(buffer, packet_blob.data, packet_blob.length);
 195         memcpy(buffer, tsig_blob.data, tsig_blob.length);
 196
 197         sig.length = state->tsig->rdata.tsig_record.mac_size;
 198         sig.data = talloc_memdup(mem_ctx, state->tsig->rdata.tsig_record.mac, sig.length);
 199         if (sig.data == NULL) {
 200                 return WERR_NOMEM;
 201         }
 202
 203
 204         status = gensec_check_packet(tkey->gensec, buffer, buffer_len,
 205                                     buffer, buffer_len, &sig);
 206         if (NT_STATUS_EQUAL(NT_STATUS_ACCESS_DENIED, status)) {
 207                 return DNS_ERR(BADKEY);
 208         }
 209
 210         if (!NT_STATUS_IS_OK(status)) {
 211                 DEBUG(0, ("Verifying tsig failed: %s\n", nt_errstr(status)));
 212                 return ntstatus_to_werror(status);
 213         }
 214
 215         state->authenticated = true;
 216
 217         return WERR_OK;
 218 }
 219
 220 WERROR dns_sign_tsig(struct dns_server *dns,
 221                      TALLOC_CTX *mem_ctx,
 222                      struct dns_request_state *state,
 223                      struct dns_name_packet *packet,
 224                      uint16_t error)
 225 {
 226         WERROR werror;
 227         NTSTATUS status;
 228         enum ndr_err_code ndr_err;
 229         time_t current_time = time(NULL);
 230         DATA_BLOB packet_blob, tsig_blob, sig;
 231         uint8_t *buffer = NULL;
 232         size_t buffer_len = 0;
 233         struct dns_server_tkey * tkey = NULL;
 234         struct dns_res_rec *tsig = talloc_zero(mem_ctx, struct dns_res_rec);
 235
 236         struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx,
 237                         struct dns_fake_tsig_rec);
 238
 239         if (tsig == NULL) {
 240                 return WERR_NOMEM;
 241         }
 242
 243         if (check_rec == NULL) {
 244                 return WERR_NOMEM;
 245         }
 246
 247         tkey = dns_find_tkey(dns->tkeys, state->key_name);
 248         if (tkey == NULL) {
 249                 /* FIXME: read up on what to do when we can't find a key */
 250                 return WERR_OK;
 251         }
 252
 253         /* first build and verify check packet */
 254         check_rec->name = talloc_strdup(check_rec, tkey->name);
 255         if (check_rec->name == NULL) {
 256                 return WERR_NOMEM;
 257         }
 258         check_rec->rr_class = DNS_QCLASS_ANY;
 259         check_rec->ttl = 0;
 260         check_rec->algorithm_name = talloc_strdup(check_rec, tkey->algorithm);
 261         if (check_rec->algorithm_name == NULL) {
 262                 return WERR_NOMEM;
 263         }
 264         check_rec->time_prefix = 0;
 265         check_rec->time = current_time;
 266         check_rec->fudge = 300;
 267         check_rec->error = state->tsig_error;
 268         check_rec->other_size = 0;
 269         check_rec->other_data = NULL;
 270
 271         ndr_err = ndr_push_struct_blob(&packet_blob, mem_ctx, packet,
 272                 (ndr_push_flags_fn_t)ndr_push_dns_name_packet);
 273         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 274                 DEBUG(1, ("Failed to push packet: %s!\n",
 275                           ndr_errstr(ndr_err)));
 276                 return DNS_ERR(SERVER_FAILURE);
 277         }
 278
 279         ndr_err = ndr_push_struct_blob(&tsig_blob, mem_ctx, check_rec,
 280                 (ndr_push_flags_fn_t)ndr_push_dns_fake_tsig_rec);
 281         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 282                 DEBUG(1, ("Failed to push packet: %s!\n",
 283                           ndr_errstr(ndr_err)));
 284                 return DNS_ERR(SERVER_FAILURE);
 285         }
 286
 287         buffer_len = packet_blob.length + tsig_blob.length;
 288         buffer = talloc_zero_array(mem_ctx, uint8_t, buffer_len);
 289         if (buffer == NULL) {
 290                 return WERR_NOMEM;
 291         }
 292
 293         memcpy(buffer, packet_blob.data, packet_blob.length);
 294         memcpy(buffer+packet_blob.length, tsig_blob.data, tsig_blob.length);
 295
 296
 297         status = gensec_sign_packet(tkey->gensec, mem_ctx, buffer, buffer_len,
 298                                     buffer, buffer_len, &sig);
 299         if (!NT_STATUS_IS_OK(status)) {
 300                 return ntstatus_to_werror(status);
 301         }
 302
 303         tsig->name = talloc_strdup(tsig, check_rec->name);
 304         if (tsig->name == NULL) {
 305                 return WERR_NOMEM;
 306         }
 307         tsig->rr_class = check_rec->rr_class;
 308         tsig->rr_type = DNS_QTYPE_TSIG;
 309         tsig->ttl = 0;
 310         tsig->length = UINT16_MAX;
 311         tsig->rdata.tsig_record.algorithm_name = talloc_strdup(tsig,
 312                         check_rec->algorithm_name);
 313         tsig->rdata.tsig_record.time_prefix = check_rec->time_prefix;
 314         tsig->rdata.tsig_record.time = check_rec->time;
 315         tsig->rdata.tsig_record.fudge = check_rec->fudge;
 316         tsig->rdata.tsig_record.error = state->tsig_error;
 317         tsig->rdata.tsig_record.original_id = packet->id;
 318         tsig->rdata.tsig_record.other_size = 0;
 319         tsig->rdata.tsig_record.other_data = NULL;
 320         tsig->rdata.tsig_record.mac_size = sig.length;
 321         tsig->rdata.tsig_record.mac = talloc_memdup(tsig, sig.data, sig.length);
 322
 323
 324         if (packet->arcount == 0) {
 325                 packet->additional = talloc_zero(mem_ctx, struct dns_res_rec);
 326                 if (packet->additional == NULL) {
 327                         return WERR_NOMEM;
 328                 }
 329         }
 330         packet->additional = talloc_realloc(mem_ctx, packet->additional,
 331                                             struct dns_res_rec,
 332                                             packet->arcount + 1);
 333         if (packet->additional == NULL) {
 334                 return WERR_NOMEM;
 335         }
 336
 337         werror = dns_copy_tsig(mem_ctx, tsig,
 338                                &packet->additional[packet->arcount]);
 339         if (!W_ERROR_IS_OK(werror)) {
 340                 return werror;
 341         }
 342         packet->arcount++;
 343
 344         return WERR_OK;
 345 }