source4/libcli/resolve/dns_ex.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    async getaddrinfo()/dns_lookup() name resolution module
   5
   6    Copyright (C) Andrew Tridgell 2005
   7    Copyright (C) Stefan Metzmacher 2008
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21 */
  22
  23 /*
  24   this module uses a fork() per getaddrinfo() or dns_looup() call.
  25   At first that might seem crazy, but it is actually very fast,
  26   and solves many of the tricky problems of keeping a child
  27   hanging around in a librar (like what happens when the parent forks).
  28   We use a talloc destructor to ensure that the child is cleaned up
  29   when we have finished with this name resolution.
  30 */
  31
  32 #include "includes.h"
  33 #include "lib/events/events.h"
  34 #include "system/network.h"
  35 #include "system/filesys.h"
  36 #include "lib/socket/socket.h"
  37 #include "libcli/composite/composite.h"
  38 #include "librpc/gen_ndr/ndr_nbt.h"
  39 #include "libcli/resolve/resolve.h"
  40 #include "heimdal/lib/roken/resolve.h"
  41
  42 struct dns_ex_state {
  43         bool do_getaddrinfo;
  44         bool do_fallback;
  45         bool do_srv;
  46         uint32_t flags;
  47         struct nbt_name name;
  48         struct socket_address **addrs;
  49         char **names;
  50         pid_t child;
  51         int child_fd;
  52         struct fd_event *fde;
  53         struct event_context *event_ctx;
  54 };
  55
  56 /*
  57   kill off a wayward child if needed. This allows us to stop an async
  58   name resolution without leaving a potentially blocking call running
  59   in a child
  60 */
  61 static int dns_ex_destructor(struct dns_ex_state *state)
  62 {
  63         int status;
  64
  65         kill(state->child, SIGTERM);
  66         close(state->child_fd);
  67         if (waitpid(state->child, &status, WNOHANG) == 0) {
  68                 kill(state->child, SIGKILL);
  69                 waitpid(state->child, &status, 0);
  70         }
  71
  72         return 0;
  73 }
  74
  75 /*
  76   the blocking child
  77 */
  78 static void run_child_dns_lookup(struct dns_ex_state *state, int fd)
  79 {
  80         struct dns_reply *reply;
  81         struct resource_record *rr;
  82         uint32_t count = 0;
  83         uint32_t srv_valid = 0;
  84         struct resource_record **srv_rr;
  85         uint32_t addrs_valid = 0;
  86         struct resource_record **addrs_rr;
  87         char *addrs;
  88         bool first;
  89         uint32_t i;
  90
  91         /* this is the blocking call we are going to lots of trouble
  92            to avoid in the parent */
  93         reply = dns_lookup(state->name.name, state->do_srv?"SRV":"A");
  94         if (!reply) {
  95                 goto done;
  96         }
  97
  98         if (state->do_srv) {
  99                 dns_srv_order(reply);
 100         }
 101
 102         /* Loop over all returned records and pick the "srv" records */
 103         for (rr=reply->head; rr; rr=rr->next) {
 104                 /* we are only interested in the IN class */
 105                 if (rr->class != C_IN) {
 106                         continue;
 107                 }
 108
 109                 if (state->do_srv) {
 110                         /* we are only interested in SRV records */
 111                         if (rr->type != T_SRV) {
 112                                 continue;
 113                         }
 114
 115                         /* verify we actually have a SRV record here */
 116                         if (!rr->u.srv) {
 117                                 continue;
 118                         }
 119
 120                         /* Verify we got a port */
 121                         if (rr->u.srv->port == 0) {
 122                                 continue;
 123                         }
 124                 } else {
 125                         /* we are only interested in A records */
 126                         /* TODO: add AAAA support */
 127                         if (rr->type != T_A) {
 128                                 continue;
 129                         }
 130
 131                         /* verify we actually have a A record here */
 132                         if (!rr->u.a) {
 133                                 continue;
 134                         }
 135                 }
 136                 count++;
 137         }
 138
 139         if (count == 0) {
 140                 goto done;
 141         }
 142
 143         srv_rr = talloc_zero_array(state,
 144                                    struct resource_record *,
 145                                    count);
 146         if (!srv_rr) {
 147                 goto done;
 148         }
 149
 150         addrs_rr = talloc_zero_array(state,
 151                                      struct resource_record *,
 152                                      count);
 153         if (!addrs_rr) {
 154                 goto done;
 155         }
 156
 157         /* Loop over all returned records and pick the records */
 158         for (rr=reply->head;rr;rr=rr->next) {
 159                 /* we are only interested in the IN class */
 160                 if (rr->class != C_IN) {
 161                         continue;
 162                 }
 163
 164                 if (state->do_srv) {
 165                         /* we are only interested in SRV records */
 166                         if (rr->type != T_SRV) {
 167                                 continue;
 168                         }
 169
 170                         /* verify we actually have a srv record here */
 171                         if (!rr->u.srv) {
 172                                 continue;
 173                         }
 174
 175                         /* Verify we got a port */
 176                         if (rr->u.srv->port == 0) {
 177                                 continue;
 178                         }
 179
 180                         srv_rr[srv_valid] = rr;
 181                         srv_valid++;
 182                 } else {
 183                         /* we are only interested in A records */
 184                         /* TODO: add AAAA support */
 185                         if (rr->type != T_A) {
 186                                 continue;
 187                         }
 188
 189                         /* verify we actually have a A record here */
 190                         if (!rr->u.a) {
 191                                 continue;
 192                         }
 193
 194                         addrs_rr[addrs_valid] = rr;
 195                         addrs_valid++;
 196                 }
 197         }
 198
 199         for (i=0; i < srv_valid; i++) {
 200                 for (rr=reply->head;rr;rr=rr->next) {
 201
 202                         if (rr->class != C_IN) {
 203                                 continue;
 204                         }
 205
 206                         /* we are only interested in SRV records */
 207                         if (rr->type != T_A) {
 208                                 continue;
 209                         }
 210
 211                         /* verify we actually have a srv record here */
 212                         if (strcmp(&srv_rr[i]->u.srv->target[0], rr->domain) != 0) {
 213                                 continue;
 214                         }
 215
 216                         addrs_rr[i] = rr;
 217                         addrs_valid++;
 218                         break;
 219                 }
 220         }
 221
 222         if (addrs_valid == 0) {
 223                 goto done;
 224         }
 225
 226         addrs = talloc_strdup(state, "");
 227         if (!addrs) {
 228                 goto done;
 229         }
 230         first = true;
 231         for (i=0; i < count; i++) {
 232                 if (!addrs_rr[i]) {
 233                         continue;
 234                 }
 235                 addrs = talloc_asprintf_append_buffer(addrs, "%s%s:%u/%s",
 236                                                       first?"":",",
 237                                                       inet_ntoa(*addrs_rr[i]->u.a),
 238                                                       srv_rr[i]?srv_rr[i]->u.srv->port:0,
 239                                                       addrs_rr[i]->domain);
 240                 if (!addrs) {
 241                         goto done;
 242                 }
 243                 first = false;
 244         }
 245
 246         if (addrs) {
 247                 write(fd, addrs, talloc_get_size(addrs));
 248         }
 249
 250 done:
 251         close(fd);
 252 }
 253
 254 /*
 255   the blocking child
 256 */
 257 static void run_child_getaddrinfo(struct dns_ex_state *state, int fd)
 258 {
 259         int ret;
 260         struct addrinfo hints;
 261         struct addrinfo *res;
 262         struct addrinfo *res_list = NULL;
 263         char *addrs;
 264         bool first;
 265
 266         ZERO_STRUCT(hints);
 267         hints.ai_socktype = SOCK_STREAM;
 268         hints.ai_family = AF_INET;/* TODO: add AF_INET6 support */
 269         hints.ai_flags = AI_ADDRCONFIG | AI_NUMERICSERV;
 270
 271         ret = getaddrinfo(state->name.name, "0", &hints, &res_list);
 272         if (ret == EAI_NODATA && state->do_fallback) {
 273                 /* getaddrinfo() doesn't handle CNAME records */
 274                 run_child_dns_lookup(state, fd);
 275                 return;
 276         }
 277         if (ret != 0) {
 278                 goto done;
 279         }
 280
 281         addrs = talloc_strdup(state, "");
 282         if (!addrs) {
 283                 goto done;
 284         }
 285         first = true;
 286         for (res = res_list; res; res = res->ai_next) {
 287                 struct sockaddr_in *in;
 288
 289                 if (res->ai_family != AF_INET) {
 290                         continue;
 291                 }
 292                 in = (struct sockaddr_in *)res->ai_addr;
 293
 294                 addrs = talloc_asprintf_append_buffer(addrs, "%s%s:%u/%s",
 295                                                       first?"":",",
 296                                                       inet_ntoa(in->sin_addr),
 297                                                       0, state->name.name);
 298                 if (!addrs) {
 299                         goto done;
 300                 }
 301                 first = false;
 302         }
 303
 304         if (addrs) {
 305                 write(fd, addrs, talloc_get_size(addrs));
 306         }
 307 done:
 308         if (res_list) {
 309                 freeaddrinfo(res_list);
 310         }
 311         close(fd);
 312 }
 313
 314 /*
 315   handle a read event on the pipe
 316 */
 317 static void pipe_handler(struct event_context *ev, struct fd_event *fde,
 318                          uint16_t flags, void *private_data)
 319 {
 320         struct composite_context *c = talloc_get_type(private_data, struct composite_context);
 321         struct dns_ex_state *state = talloc_get_type(c->private_data,
 322                                      struct dns_ex_state);
 323         char *address;
 324         uint32_t num_addrs, i;
 325         char **addrs;
 326         int ret;
 327         int status;
 328         int value = 0;
 329
 330         /* if we get any event from the child then we know that we
 331            won't need to kill it off */
 332         talloc_set_destructor(state, NULL);
 333
 334         if (ioctl(state->child_fd, FIONREAD, &value) != 0) {
 335                 value = 8192;
 336         }
 337
 338         address = talloc_array(state, char, value+1);
 339         if (address) {
 340                 /* yes, we don't care about EAGAIN or other niceities
 341                    here. They just can't happen with this parent/child
 342                    relationship, and even if they did then giving an error is
 343                    the right thing to do */
 344                 ret = read(state->child_fd, address, value);
 345         } else {
 346                 ret = -1;
 347         }
 348         close(state->child_fd);
 349         if (waitpid(state->child, &status, WNOHANG) == 0) {
 350                 kill(state->child, SIGKILL);
 351                 waitpid(state->child, &status, 0);
 352         }
 353
 354         if (ret <= 0) {
 355                 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
 356                 return;
 357         }
 358
 359         /* enusre the address looks good */
 360         address[ret] = 0;
 361
 362         addrs = str_list_make(state, address, ",");
 363         if (composite_nomem(addrs, c)) return;
 364
 365         num_addrs = str_list_length((const char * const *)addrs);
 366
 367         state->addrs = talloc_array(state, struct socket_address *,
 368                                     num_addrs+1);
 369         if (composite_nomem(state->addrs, c)) return;
 370
 371         state->names = talloc_array(state, char *, num_addrs+1);
 372         if (composite_nomem(state->names, c)) return;
 373
 374         for (i=0; i < num_addrs; i++) {
 375                 uint32_t port = 0;
 376                 char *p = strrchr(addrs[i], ':');
 377                 char *n;
 378
 379                 if (!p) {
 380                         composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
 381                         return;
 382                 }
 383
 384                 *p = '\0';
 385                 p++;
 386
 387                 n = strrchr(p, '/');
 388                 if (!n) {
 389                         composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
 390                         return;
 391                 }
 392
 393                 *n = '\0';
 394                 n++;
 395
 396                 if (strcmp(addrs[i], "0.0.0.0") == 0 ||
 397                     inet_addr(addrs[i]) == INADDR_NONE) {
 398                         composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
 399                         return;
 400                 }
 401                 port = strtoul(p, NULL, 10);
 402                 if (port > UINT16_MAX) {
 403                         port = 0;
 404                 }
 405                 state->addrs[i] = socket_address_from_strings(state->addrs,
 406                                                               "ipv4",
 407                                                               addrs[i],
 408                                                               port);
 409                 if (composite_nomem(state->addrs[i], c)) return;
 410
 411                 state->names[i] = talloc_strdup(state->names, n);
 412                 if (composite_nomem(state->names[i], c)) return;
 413         }
 414         state->addrs[i] = NULL;
 415         state->names[i] = NULL;
 416
 417         composite_done(c);
 418 }
 419
 420 /*
 421   getaddrinfo() or dns_lookup() name resolution method - async send
 422  */
 423 struct composite_context *resolve_name_dns_ex_send(TALLOC_CTX *mem_ctx,
 424                                                    struct event_context *event_ctx,
 425                                                    void *privdata,
 426                                                    uint32_t flags,
 427                                                    struct nbt_name *name,
 428                                                    bool do_getaddrinfo,
 429                                                    bool do_fallback,
 430                                                    bool do_srv)
 431 {
 432         struct composite_context *c;
 433         struct dns_ex_state *state;
 434         int fd[2] = { -1, -1 };
 435         int ret;
 436
 437         c = composite_create(mem_ctx, event_ctx);
 438         if (c == NULL) return NULL;
 439
 440         if (composite_nomem(c->event_ctx, c)) return c;
 441
 442         state = talloc_zero(c, struct dns_ex_state);
 443         if (composite_nomem(state, c)) return c;
 444         c->private_data = state;
 445
 446         c->status = nbt_name_dup(state, name, &state->name);
 447         if (!composite_is_ok(c)) return c;
 448
 449         /* setup a pipe to chat to our child */
 450         ret = pipe(fd);
 451         if (ret == -1) {
 452                 composite_error(c, map_nt_error_from_unix(errno));
 453                 return c;
 454         }
 455
 456         state->do_getaddrinfo = do_getaddrinfo;
 457         state->do_fallback = do_fallback;
 458         state->do_srv = do_srv;
 459         state->flags = flags;
 460
 461         state->child_fd = fd[0];
 462         state->event_ctx = c->event_ctx;
 463
 464         /* we need to put the child in our event context so
 465            we know when the dns_lookup() has finished */
 466         state->fde = event_add_fd(c->event_ctx, c, state->child_fd, EVENT_FD_READ,
 467                                   pipe_handler, c);
 468         if (composite_nomem(state->fde, c)) {
 469                 close(fd[0]);
 470                 close(fd[1]);
 471                 return c;
 472         }
 473
 474         state->child = fork();
 475         if (state->child == (pid_t)-1) {
 476                 composite_error(c, map_nt_error_from_unix(errno));
 477                 return c;
 478         }
 479
 480         if (state->child == 0) {
 481                 close(fd[0]);
 482                 if (state->do_getaddrinfo) {
 483                         run_child_getaddrinfo(state, fd[1]);
 484                 } else {
 485                         run_child_dns_lookup(state, fd[1]);
 486                 }
 487                 _exit(0);
 488         }
 489         close(fd[1]);
 490
 491         /* cleanup wayward children */
 492         talloc_set_destructor(state, dns_ex_destructor);
 493
 494         return c;
 495 }
 496
 497 /*
 498   getaddrinfo() or dns_lookup() name resolution method - recv side
 499 */
 500 NTSTATUS resolve_name_dns_ex_recv(struct composite_context *c,
 501                                   TALLOC_CTX *mem_ctx,
 502                                   struct socket_address ***addrs,
 503                                   char ***names)
 504 {
 505         NTSTATUS status;
 506
 507         status = composite_wait(c);
 508
 509         if (NT_STATUS_IS_OK(status)) {
 510                 struct dns_ex_state *state = talloc_get_type(c->private_data,
 511                                              struct dns_ex_state);
 512                 *addrs = talloc_steal(mem_ctx, state->addrs);
 513                 if (names) {
 514                         *names = talloc_steal(mem_ctx, state->names);
 515                 }
 516         }
 517
 518         talloc_free(c);
 519         return status;
 520 }