src/resolve/resolved-dns-packet.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2014 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20  ***/
  21
  22 #include "utf8.h"
  23 #include "util.h"
  24 #include "strv.h"
  25 #include "resolved-dns-domain.h"
  26 #include "resolved-dns-packet.h"
  27
  28 int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
  29         DnsPacket *p;
  30         size_t a;
  31
  32         assert(ret);
  33
  34         if (mtu <= 0)
  35                 a = DNS_PACKET_SIZE_START;
  36         else
  37                 a = mtu;
  38
  39         if (a < DNS_PACKET_HEADER_SIZE)
  40                 a = DNS_PACKET_HEADER_SIZE;
  41
  42         /* round up to next page size */
  43         a = PAGE_ALIGN(ALIGN(sizeof(DnsPacket)) + a) - ALIGN(sizeof(DnsPacket));
  44
  45         /* make sure we never allocate more than useful */
  46         if (a > DNS_PACKET_SIZE_MAX)
  47                 a = DNS_PACKET_SIZE_MAX;
  48
  49         p = malloc0(ALIGN(sizeof(DnsPacket)) + a);
  50         if (!p)
  51                 return -ENOMEM;
  52
  53         p->size = p->rindex = DNS_PACKET_HEADER_SIZE;
  54         p->allocated = a;
  55         p->protocol = protocol;
  56         p->n_ref = 1;
  57
  58         *ret = p;
  59
  60         return 0;
  61 }
  62
  63 int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
  64         DnsPacket *p;
  65         DnsPacketHeader *h;
  66         int r;
  67
  68         assert(ret);
  69
  70         r = dns_packet_new(&p, protocol, mtu);
  71         if (r < 0)
  72                 return r;
  73
  74         h = DNS_PACKET_HEADER(p);
  75
  76         if (protocol == DNS_PROTOCOL_LLMNR)
  77                 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
  78                                                          0 /* opcode */,
  79                                                          0 /* c */,
  80                                                          0 /* tc */,
  81                                                          0 /* t */,
  82                                                          0 /* ra */,
  83                                                          0 /* ad */,
  84                                                          0 /* cd */,
  85                                                          0 /* rcode */));
  86         else
  87                 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
  88                                                          0 /* opcode */,
  89                                                          0 /* aa */,
  90                                                          0 /* tc */,
  91                                                          1 /* rd (ask for recursion) */,
  92                                                          0 /* ra */,
  93                                                          0 /* ad */,
  94                                                          0 /* cd */,
  95                                                          0 /* rcode */));
  96
  97         *ret = p;
  98         return 0;
  99 }
 100
 101 DnsPacket *dns_packet_ref(DnsPacket *p) {
 102
 103         if (!p)
 104                 return NULL;
 105
 106         assert(p->n_ref > 0);
 107         p->n_ref++;
 108         return p;
 109 }
 110
 111 static void dns_packet_free(DnsPacket *p) {
 112         char *s;
 113
 114         assert(p);
 115
 116         dns_question_unref(p->question);
 117         dns_answer_unref(p->answer);
 118
 119         while ((s = hashmap_steal_first_key(p->names)))
 120                 free(s);
 121         hashmap_free(p->names);
 122
 123         free(p->_data);
 124         free(p);
 125 }
 126
 127 DnsPacket *dns_packet_unref(DnsPacket *p) {
 128         if (!p)
 129                 return NULL;
 130
 131         assert(p->n_ref > 0);
 132
 133         if (p->n_ref == 1)
 134                 dns_packet_free(p);
 135         else
 136                 p->n_ref--;
 137
 138         return NULL;
 139 }
 140
 141 int dns_packet_validate(DnsPacket *p) {
 142         assert(p);
 143
 144         if (p->size < DNS_PACKET_HEADER_SIZE)
 145                 return -EBADMSG;
 146
 147         if (p->size > DNS_PACKET_SIZE_MAX)
 148                 return -EBADMSG;
 149
 150         return 1;
 151 }
 152
 153 int dns_packet_validate_reply(DnsPacket *p) {
 154         int r;
 155
 156         assert(p);
 157
 158         r = dns_packet_validate(p);
 159         if (r < 0)
 160                 return r;
 161
 162         if (DNS_PACKET_QR(p) != 1)
 163                 return 0;
 164
 165         if (DNS_PACKET_OPCODE(p) != 0)
 166                 return -EBADMSG;
 167
 168         /* RFC 4795, Section 2.1.1. says to discard all replies with QDCOUNT != 1 */
 169         if (p->protocol == DNS_PROTOCOL_LLMNR &&
 170             DNS_PACKET_QDCOUNT(p) != 1)
 171                 return -EBADMSG;
 172
 173         return 1;
 174 }
 175
 176 int dns_packet_validate_query(DnsPacket *p) {
 177         int r;
 178
 179         assert(p);
 180
 181         r = dns_packet_validate(p);
 182         if (r < 0)
 183                 return r;
 184
 185         if (DNS_PACKET_QR(p) != 0)
 186                 return 0;
 187
 188         if (DNS_PACKET_OPCODE(p) != 0)
 189                 return -EBADMSG;
 190
 191         if (DNS_PACKET_TC(p))
 192                 return -EBADMSG;
 193
 194         /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
 195         if (p->protocol == DNS_PROTOCOL_LLMNR &&
 196             DNS_PACKET_QDCOUNT(p) != 1)
 197                 return -EBADMSG;
 198
 199         /* RFC 4795, Section 2.1.1. says to discard all queries with ANCOUNT != 0 */
 200         if (DNS_PACKET_ANCOUNT(p) > 0)
 201                 return -EBADMSG;
 202
 203         /* RFC 4795, Section 2.1.1. says to discard all queries with NSCOUNT != 0 */
 204         if (DNS_PACKET_NSCOUNT(p) > 0)
 205                 return -EBADMSG;
 206
 207         return 1;
 208 }
 209
 210 static int dns_packet_extend(DnsPacket *p, size_t add, void **ret, size_t *start) {
 211         assert(p);
 212
 213         if (p->size + add > p->allocated) {
 214                 size_t a;
 215
 216                 a = PAGE_ALIGN((p->size + add) * 2);
 217                 if (a > DNS_PACKET_SIZE_MAX)
 218                         a = DNS_PACKET_SIZE_MAX;
 219
 220                 if (p->size + add > a)
 221                         return -EMSGSIZE;
 222
 223                 if (p->_data) {
 224                         void *d;
 225
 226                         d = realloc(p->_data, a);
 227                         if (!d)
 228                                 return -ENOMEM;
 229
 230                         p->_data = d;
 231                 } else {
 232                         p->_data = malloc(a);
 233                         if (!p->_data)
 234                                 return -ENOMEM;
 235
 236                         memcpy(p->_data, (uint8_t*) p + ALIGN(sizeof(DnsPacket)), p->size);
 237                         memzero((uint8_t*) p->_data + p->size, a - p->size);
 238                 }
 239
 240                 p->allocated = a;
 241         }
 242
 243         if (start)
 244                 *start = p->size;
 245
 246         if (ret)
 247                 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->size;
 248
 249         p->size += add;
 250         return 0;
 251 }
 252
 253 static void dns_packet_truncate(DnsPacket *p, size_t sz) {
 254         Iterator i;
 255         char *s;
 256         void *n;
 257
 258         assert(p);
 259
 260         if (p->size <= sz)
 261                 return;
 262
 263         HASHMAP_FOREACH_KEY(s, n, p->names, i) {
 264
 265                 if (PTR_TO_SIZE(n) < sz)
 266                         continue;
 267
 268                 hashmap_remove(p->names, s);
 269                 free(s);
 270         }
 271
 272         p->size = sz;
 273 }
 274
 275 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t l, size_t *start) {
 276         void *q;
 277         int r;
 278
 279         assert(p);
 280
 281         r = dns_packet_extend(p, l, &q, start);
 282         if (r < 0)
 283                 return r;
 284
 285         memcpy(q, d, l);
 286         return 0;
 287 }
 288
 289 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start) {
 290         void *d;
 291         int r;
 292
 293         assert(p);
 294
 295         r = dns_packet_extend(p, sizeof(uint8_t), &d, start);
 296         if (r < 0)
 297                 return r;
 298
 299         ((uint8_t*) d)[0] = v;
 300
 301         return 0;
 302 }
 303
 304 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start) {
 305         void *d;
 306         int r;
 307
 308         assert(p);
 309
 310         r = dns_packet_extend(p, sizeof(uint16_t), &d, start);
 311         if (r < 0)
 312                 return r;
 313
 314         ((uint8_t*) d)[0] = (uint8_t) (v >> 8);
 315         ((uint8_t*) d)[1] = (uint8_t) v;
 316
 317         return 0;
 318 }
 319
 320 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start) {
 321         void *d;
 322         int r;
 323
 324         assert(p);
 325
 326         r = dns_packet_extend(p, sizeof(uint32_t), &d, start);
 327         if (r < 0)
 328                 return r;
 329
 330         ((uint8_t*) d)[0] = (uint8_t) (v >> 24);
 331         ((uint8_t*) d)[1] = (uint8_t) (v >> 16);
 332         ((uint8_t*) d)[2] = (uint8_t) (v >> 8);
 333         ((uint8_t*) d)[3] = (uint8_t) v;
 334
 335         return 0;
 336 }
 337
 338 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start) {
 339         void *d;
 340         size_t l;
 341         int r;
 342
 343         assert(p);
 344         assert(s);
 345
 346         l = strlen(s);
 347         if (l > 255)
 348                 return -E2BIG;
 349
 350         r = dns_packet_extend(p, 1 + l, &d, start);
 351         if (r < 0)
 352                 return r;
 353
 354         ((uint8_t*) d)[0] = (uint8_t) l;
 355         memcpy(((uint8_t*) d) + 1, s, l);
 356
 357         return 0;
 358 }
 359
 360 int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, size_t *start) {
 361         void *w;
 362         int r;
 363
 364         assert(p);
 365         assert(d);
 366
 367         if (l > DNS_LABEL_MAX)
 368                 return -E2BIG;
 369
 370         r = dns_packet_extend(p, 1 + l, &w, start);
 371         if (r < 0)
 372                 return r;
 373
 374         ((uint8_t*) w)[0] = (uint8_t) l;
 375         memcpy(((uint8_t*) w) + 1, d, l);
 376
 377         return 0;
 378 }
 379
 380 int dns_packet_append_name(DnsPacket *p, const char *name, size_t *start) {
 381         size_t saved_size;
 382         int r;
 383
 384         assert(p);
 385         assert(name);
 386
 387         saved_size = p->size;
 388
 389         while (*name) {
 390                 _cleanup_free_ char *s = NULL;
 391                 char label[DNS_LABEL_MAX];
 392                 size_t n;
 393                 int k;
 394
 395                 n = PTR_TO_SIZE(hashmap_get(p->names, name));
 396                 if (n > 0) {
 397                         assert(n < p->size);
 398
 399                         if (n < 0x4000) {
 400                                 r = dns_packet_append_uint16(p, 0xC000 | n, NULL);
 401                                 if (r < 0)
 402                                         goto fail;
 403
 404                                 goto done;
 405                         }
 406                 }
 407
 408                 s = strdup(name);
 409                 if (!s) {
 410                         r = -ENOMEM;
 411                         goto fail;
 412                 }
 413
 414                 r = dns_label_unescape(&name, label, sizeof(label));
 415                 if (r < 0)
 416                         goto fail;
 417
 418                 if (p->protocol == DNS_PROTOCOL_DNS)
 419                         k = dns_label_apply_idna(label, r, label, sizeof(label));
 420                 else
 421                         k = dns_label_undo_idna(label, r, label, sizeof(label));
 422                 if (k < 0) {
 423                         r = k;
 424                         goto fail;
 425                 }
 426                 if (k > 0)
 427                         r = k;
 428
 429                 r = dns_packet_append_label(p, label, r, &n);
 430                 if (r < 0)
 431                         goto fail;
 432
 433                 r = hashmap_ensure_allocated(&p->names, dns_name_hash_func, dns_name_compare_func);
 434                 if (r < 0)
 435                         goto fail;
 436
 437                 r = hashmap_put(p->names, s, SIZE_TO_PTR(n));
 438                 if (r < 0)
 439                         goto fail;
 440
 441                 s = NULL;
 442         }
 443
 444         r = dns_packet_append_uint8(p, 0, NULL);
 445         if (r < 0)
 446                 return r;
 447
 448 done:
 449         if (start)
 450                 *start = saved_size;
 451
 452         return 0;
 453
 454 fail:
 455         dns_packet_truncate(p, saved_size);
 456         return r;
 457 }
 458
 459 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, size_t *start) {
 460         size_t saved_size;
 461         int r;
 462
 463         assert(p);
 464         assert(k);
 465
 466         saved_size = p->size;
 467
 468         r = dns_packet_append_name(p, DNS_RESOURCE_KEY_NAME(k), NULL);
 469         if (r < 0)
 470                 goto fail;
 471
 472         r = dns_packet_append_uint16(p, k->type, NULL);
 473         if (r < 0)
 474                 goto fail;
 475
 476         r = dns_packet_append_uint16(p, k->class, NULL);
 477         if (r < 0)
 478                 goto fail;
 479
 480         if (start)
 481                 *start = saved_size;
 482
 483         return 0;
 484
 485 fail:
 486         dns_packet_truncate(p, saved_size);
 487         return r;
 488 }
 489
 490 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start) {
 491         size_t saved_size, rdlength_offset, end, rdlength;
 492         int r;
 493
 494         assert(p);
 495         assert(rr);
 496
 497         saved_size = p->size;
 498
 499         r = dns_packet_append_key(p, rr->key, NULL);
 500         if (r < 0)
 501                 goto fail;
 502
 503         r = dns_packet_append_uint32(p, rr->ttl, NULL);
 504         if (r < 0)
 505                 goto fail;
 506
 507         /* Initially we write 0 here */
 508         r = dns_packet_append_uint16(p, 0, &rdlength_offset);
 509         if (r < 0)
 510                 goto fail;
 511
 512         switch (rr->unparseable ? _DNS_TYPE_INVALID : rr->key->type) {
 513
 514         case DNS_TYPE_SRV:
 515                 r = dns_packet_append_uint16(p, rr->srv.priority, NULL);
 516                 if (r < 0)
 517                         goto fail;
 518
 519                 r = dns_packet_append_uint16(p, rr->srv.weight, NULL);
 520                 if (r < 0)
 521                         goto fail;
 522
 523                 r = dns_packet_append_uint16(p, rr->srv.port, NULL);
 524                 if (r < 0)
 525                         goto fail;
 526
 527                 r = dns_packet_append_name(p, rr->srv.name, NULL);
 528                 break;
 529
 530         case DNS_TYPE_PTR:
 531         case DNS_TYPE_NS:
 532         case DNS_TYPE_CNAME:
 533         case DNS_TYPE_DNAME:
 534                 r = dns_packet_append_name(p, rr->ptr.name, NULL);
 535                 break;
 536
 537         case DNS_TYPE_HINFO:
 538                 r = dns_packet_append_string(p, rr->hinfo.cpu, NULL);
 539                 if (r < 0)
 540                         goto fail;
 541
 542                 r = dns_packet_append_string(p, rr->hinfo.os, NULL);
 543                 break;
 544
 545         case DNS_TYPE_SPF: /* exactly the same as TXT */
 546         case DNS_TYPE_TXT: {
 547                 char **s;
 548
 549                 STRV_FOREACH(s, rr->txt.strings) {
 550                         r = dns_packet_append_string(p, *s, NULL);
 551                         if (r < 0)
 552                                 goto fail;
 553                 }
 554
 555                 r = 0;
 556                 break;
 557         }
 558
 559         case DNS_TYPE_A:
 560                 r = dns_packet_append_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
 561                 break;
 562
 563         case DNS_TYPE_AAAA:
 564                 r = dns_packet_append_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
 565                 break;
 566
 567         case DNS_TYPE_SOA:
 568                 r = dns_packet_append_name(p, rr->soa.mname, NULL);
 569                 if (r < 0)
 570                         goto fail;
 571
 572                 r = dns_packet_append_name(p, rr->soa.rname, NULL);
 573                 if (r < 0)
 574                         goto fail;
 575
 576                 r = dns_packet_append_uint32(p, rr->soa.serial, NULL);
 577                 if (r < 0)
 578                         goto fail;
 579
 580                 r = dns_packet_append_uint32(p, rr->soa.refresh, NULL);
 581                 if (r < 0)
 582                         goto fail;
 583
 584                 r = dns_packet_append_uint32(p, rr->soa.retry, NULL);
 585                 if (r < 0)
 586                         goto fail;
 587
 588                 r = dns_packet_append_uint32(p, rr->soa.expire, NULL);
 589                 if (r < 0)
 590                         goto fail;
 591
 592                 r = dns_packet_append_uint32(p, rr->soa.minimum, NULL);
 593                 break;
 594
 595         case DNS_TYPE_MX:
 596                 r = dns_packet_append_uint16(p, rr->mx.priority, NULL);
 597                 if (r < 0)
 598                         goto fail;
 599
 600                 r = dns_packet_append_name(p, rr->mx.exchange, NULL);
 601                 break;
 602
 603         case DNS_TYPE_LOC:
 604                 r = dns_packet_append_uint8(p, rr->loc.version, NULL);
 605                 if (r < 0)
 606                         goto fail;
 607
 608                 r = dns_packet_append_uint8(p, rr->loc.size, NULL);
 609                 if (r < 0)
 610                         goto fail;
 611
 612                 r = dns_packet_append_uint8(p, rr->loc.horiz_pre, NULL);
 613                 if (r < 0)
 614                         goto fail;
 615
 616                 r = dns_packet_append_uint8(p, rr->loc.vert_pre, NULL);
 617                 if (r < 0)
 618                         goto fail;
 619
 620                 r = dns_packet_append_uint32(p, rr->loc.latitude, NULL);
 621                 if (r < 0)
 622                         goto fail;
 623
 624                 r = dns_packet_append_uint32(p, rr->loc.longitude, NULL);
 625                 if (r < 0)
 626                         goto fail;
 627
 628                 r = dns_packet_append_uint32(p, rr->loc.altitude, NULL);
 629                 break;
 630
 631         case DNS_TYPE_SSHFP:
 632                 r = dns_packet_append_uint8(p, rr->sshfp.algorithm, NULL);
 633                 if (r < 0)
 634                         goto fail;
 635
 636                 r = dns_packet_append_uint8(p, rr->sshfp.fptype, NULL);
 637                 if (r < 0)
 638                         goto fail;
 639
 640                 r = dns_packet_append_blob(p, rr->sshfp.key, rr->sshfp.key_size, NULL);
 641                 break;
 642
 643         case DNS_TYPE_DNSKEY:
 644                 r = dns_packet_append_uint16(p, dnskey_to_flags(rr), NULL);
 645                 if (r < 0)
 646                         goto fail;
 647
 648                 r = dns_packet_append_uint8(p, 3u, NULL);
 649                 if (r < 0)
 650                         goto fail;
 651
 652                 r = dns_packet_append_uint8(p, rr->dnskey.algorithm, NULL);
 653                 if (r < 0)
 654                         goto fail;
 655
 656                 r = dns_packet_append_blob(p, rr->dnskey.key, rr->dnskey.key_size, NULL);
 657                 break;
 658
 659         case _DNS_TYPE_INVALID: /* unparseable */
 660         default:
 661
 662                 r = dns_packet_append_blob(p, rr->generic.data, rr->generic.size, NULL);
 663                 break;
 664         }
 665         if (r < 0)
 666                 goto fail;
 667
 668         /* Let's calculate the actual data size and update the field */
 669         rdlength = p->size - rdlength_offset - sizeof(uint16_t);
 670         if (rdlength > 0xFFFF) {
 671                 r = ENOSPC;
 672                 goto fail;
 673         }
 674
 675         end = p->size;
 676         p->size = rdlength_offset;
 677         r = dns_packet_append_uint16(p, rdlength, NULL);
 678         if (r < 0)
 679                 goto fail;
 680         p->size = end;
 681
 682         if (start)
 683                 *start = saved_size;
 684
 685         return 0;
 686
 687 fail:
 688         dns_packet_truncate(p, saved_size);
 689         return r;
 690 }
 691
 692
 693 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
 694         assert(p);
 695
 696         if (p->rindex + sz > p->size)
 697                 return -EMSGSIZE;
 698
 699         if (ret)
 700                 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex;
 701
 702         if (start)
 703                 *start = p->rindex;
 704
 705         p->rindex += sz;
 706         return 0;
 707 }
 708
 709 void dns_packet_rewind(DnsPacket *p, size_t idx) {
 710         assert(p);
 711         assert(idx <= p->size);
 712         assert(idx >= DNS_PACKET_HEADER_SIZE);
 713
 714         p->rindex = idx;
 715 }
 716
 717 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start) {
 718         const void *q;
 719         int r;
 720
 721         assert(p);
 722         assert(d);
 723
 724         r = dns_packet_read(p, sz, &q, start);
 725         if (r < 0)
 726                 return r;
 727
 728         memcpy(d, q, sz);
 729         return 0;
 730 }
 731
 732 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) {
 733         const void *d;
 734         int r;
 735
 736         assert(p);
 737
 738         r = dns_packet_read(p, sizeof(uint8_t), &d, start);
 739         if (r < 0)
 740                 return r;
 741
 742         *ret = ((uint8_t*) d)[0];
 743         return 0;
 744 }
 745
 746 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) {
 747         const void *d;
 748         int r;
 749
 750         assert(p);
 751
 752         r = dns_packet_read(p, sizeof(uint16_t), &d, start);
 753         if (r < 0)
 754                 return r;
 755
 756         *ret = (((uint16_t) ((uint8_t*) d)[0]) << 8) |
 757                 ((uint16_t) ((uint8_t*) d)[1]);
 758         return 0;
 759 }
 760
 761 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) {
 762         const void *d;
 763         int r;
 764
 765         assert(p);
 766
 767         r = dns_packet_read(p, sizeof(uint32_t), &d, start);
 768         if (r < 0)
 769                 return r;
 770
 771         *ret = (((uint32_t) ((uint8_t*) d)[0]) << 24) |
 772                (((uint32_t) ((uint8_t*) d)[1]) << 16) |
 773                (((uint32_t) ((uint8_t*) d)[2]) << 8) |
 774                 ((uint32_t) ((uint8_t*) d)[3]);
 775
 776         return 0;
 777 }
 778
 779 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) {
 780         size_t saved_rindex;
 781         const void *d;
 782         char *t;
 783         uint8_t c;
 784         int r;
 785
 786         assert(p);
 787
 788         saved_rindex = p->rindex;
 789
 790         r = dns_packet_read_uint8(p, &c, NULL);
 791         if (r < 0)
 792                 goto fail;
 793
 794         r = dns_packet_read(p, c, &d, NULL);
 795         if (r < 0)
 796                 goto fail;
 797
 798         if (memchr(d, 0, c)) {
 799                 r = -EBADMSG;
 800                 goto fail;
 801         }
 802
 803         t = strndup(d, c);
 804         if (!t) {
 805                 r = -ENOMEM;
 806                 goto fail;
 807         }
 808
 809         if (!utf8_is_valid(t)) {
 810                 free(t);
 811                 r = -EBADMSG;
 812                 goto fail;
 813         }
 814
 815         *ret = t;
 816
 817         if (start)
 818                 *start = saved_rindex;
 819
 820         return 0;
 821
 822 fail:
 823         dns_packet_rewind(p, saved_rindex);
 824         return r;
 825 }
 826
 827 int dns_packet_read_name(DnsPacket *p, char **_ret, size_t *start) {
 828         size_t saved_rindex, after_rindex = 0;
 829         _cleanup_free_ char *ret = NULL;
 830         size_t n = 0, allocated = 0;
 831         bool first = true;
 832         int r;
 833
 834         assert(p);
 835         assert(_ret);
 836
 837         saved_rindex = p->rindex;
 838
 839         for (;;) {
 840                 uint8_t c, d;
 841
 842                 r = dns_packet_read_uint8(p, &c, NULL);
 843                 if (r < 0)
 844                         goto fail;
 845
 846                 if (c == 0)
 847                         /* End of name */
 848                         break;
 849                 else if (c <= 63) {
 850                         _cleanup_free_ char *t = NULL;
 851                         const char *label;
 852
 853                         /* Literal label */
 854                         r = dns_packet_read(p, c, (const void**) &label, NULL);
 855                         if (r < 0)
 856                                 goto fail;
 857
 858                         r = dns_label_escape(label, c, &t);
 859                         if (r < 0)
 860                                 goto fail;
 861
 862                         if (!GREEDY_REALLOC(ret, allocated, n + !first + strlen(t) + 1)) {
 863                                 r = -ENOMEM;
 864                                 goto fail;
 865                         }
 866
 867                         if (!first)
 868                                 ret[n++] = '.';
 869                         else
 870                                 first = false;
 871
 872                         memcpy(ret + n, t, r);
 873                         n += r;
 874                         continue;
 875                 } else if ((c & 0xc0) == 0xc0) {
 876                         uint16_t ptr;
 877
 878                         /* Pointer */
 879                         r = dns_packet_read_uint8(p, &d, NULL);
 880                         if (r < 0)
 881                                 goto fail;
 882
 883                         ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
 884                         if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= saved_rindex) {
 885                                 r = -EBADMSG;
 886                                 goto fail;
 887                         }
 888
 889                         if (after_rindex == 0)
 890                                 after_rindex = p->rindex;
 891
 892                         p->rindex = ptr;
 893                 } else
 894                         goto fail;
 895         }
 896
 897         if (!GREEDY_REALLOC(ret, allocated, n + 1)) {
 898                 r = -ENOMEM;
 899                 goto fail;
 900         }
 901
 902         ret[n] = 0;
 903
 904         if (after_rindex != 0)
 905                 p->rindex= after_rindex;
 906
 907         *_ret = ret;
 908         ret = NULL;
 909
 910         if (start)
 911                 *start = saved_rindex;
 912
 913         return 0;
 914
 915 fail:
 916         dns_packet_rewind(p, saved_rindex);
 917         return r;
 918 }
 919
 920 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
 921         _cleanup_free_ char *name = NULL;
 922         uint16_t class, type;
 923         DnsResourceKey *key;
 924         size_t saved_rindex;
 925         int r;
 926
 927         assert(p);
 928         assert(ret);
 929
 930         saved_rindex = p->rindex;
 931
 932         r = dns_packet_read_name(p, &name, NULL);
 933         if (r < 0)
 934                 goto fail;
 935
 936         r = dns_packet_read_uint16(p, &type, NULL);
 937         if (r < 0)
 938                 goto fail;
 939
 940         r = dns_packet_read_uint16(p, &class, NULL);
 941         if (r < 0)
 942                 goto fail;
 943
 944         key = dns_resource_key_new_consume(class, type, name);
 945         if (!key) {
 946                 r = -ENOMEM;
 947                 goto fail;
 948         }
 949
 950         name = NULL;
 951         *ret = key;
 952
 953         if (start)
 954                 *start = saved_rindex;
 955
 956         return 0;
 957 fail:
 958         dns_packet_rewind(p, saved_rindex);
 959         return r;
 960 }
 961
 962 static int dns_packet_read_public_key(DnsPacket *p, size_t length,
 963                                       void **dp, size_t *lengthp,
 964                                       size_t *start) {
 965         int r;
 966         const void *d;
 967         void *d2;
 968
 969         r = dns_packet_read(p, length, &d, NULL);
 970         if (r < 0)
 971                 return r;
 972
 973         d2 = memdup(d, length);
 974         if (!d2)
 975                 return -ENOMEM;
 976
 977         *dp = d2;
 978         *lengthp = length;
 979         return 0;
 980 }
 981
 982 static bool loc_size_ok(uint8_t size) {
 983         uint8_t m = size >> 4, e = size & 0xF;
 984
 985         return m <= 9 && e <= 9 && (m > 0 || e == 0);
 986 }
 987
 988 static int dnskey_parse_flags(DnsResourceRecord *rr, uint16_t flags) {
 989         if (flags & ~(DNSKEY_FLAG_SEP | DNSKEY_FLAG_ZONE_KEY))
 990                 return -EBADMSG;
 991
 992         rr->dnskey.zone_key_flag = flags & DNSKEY_FLAG_ZONE_KEY;
 993         rr->dnskey.sep_flag = flags & DNSKEY_FLAG_SEP;
 994         return 0;
 995 }
 996
 997 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 998         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
 999         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1000         size_t saved_rindex, offset;
1001         uint16_t rdlength;
1002         const void *d;
1003         int r;
1004
1005         assert(p);
1006         assert(ret);
1007
1008         saved_rindex = p->rindex;
1009
1010         r = dns_packet_read_key(p, &key, NULL);
1011         if (r < 0)
1012                 goto fail;
1013
1014         if (key->class == DNS_CLASS_ANY ||
1015             key->type == DNS_TYPE_ANY) {
1016                 r = -EBADMSG;
1017                 goto fail;
1018         }
1019
1020         rr = dns_resource_record_new(key);
1021         if (!rr) {
1022                 r = -ENOMEM;
1023                 goto fail;
1024         }
1025
1026         r = dns_packet_read_uint32(p, &rr->ttl, NULL);
1027         if (r < 0)
1028                 goto fail;
1029
1030         r = dns_packet_read_uint16(p, &rdlength, NULL);
1031         if (r < 0)
1032                 goto fail;
1033
1034         if (p->rindex + rdlength > p->size) {
1035                 r = -EBADMSG;
1036                 goto fail;
1037         }
1038
1039         offset = p->rindex;
1040
1041         switch (rr->key->type) {
1042
1043         case DNS_TYPE_SRV:
1044                 r = dns_packet_read_uint16(p, &rr->srv.priority, NULL);
1045                 if (r < 0)
1046                         goto fail;
1047                 r = dns_packet_read_uint16(p, &rr->srv.weight, NULL);
1048                 if (r < 0)
1049                         goto fail;
1050                 r = dns_packet_read_uint16(p, &rr->srv.port, NULL);
1051                 if (r < 0)
1052                         goto fail;
1053                 r = dns_packet_read_name(p, &rr->srv.name, NULL);
1054                 break;
1055
1056         case DNS_TYPE_PTR:
1057         case DNS_TYPE_NS:
1058         case DNS_TYPE_CNAME:
1059         case DNS_TYPE_DNAME:
1060                 r = dns_packet_read_name(p, &rr->ptr.name, NULL);
1061                 break;
1062
1063         case DNS_TYPE_HINFO:
1064                 r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
1065                 if (r < 0)
1066                         goto fail;
1067
1068                 r = dns_packet_read_string(p, &rr->hinfo.os, NULL);
1069                 break;
1070
1071         case DNS_TYPE_SPF: /* exactly the same as TXT */
1072         case DNS_TYPE_TXT: {
1073                 char *s;
1074
1075                 while (p->rindex < offset + rdlength) {
1076                         r = dns_packet_read_string(p, &s, NULL);
1077                         if (r < 0)
1078                                 goto fail;
1079
1080                         r = strv_consume(&rr->txt.strings, s);
1081                         if (r < 0)
1082                                 goto fail;
1083                 }
1084
1085                 r = 0;
1086                 break;
1087         }
1088
1089         case DNS_TYPE_A:
1090                 r = dns_packet_read_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
1091                 break;
1092
1093         case DNS_TYPE_AAAA:
1094                 r = dns_packet_read_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
1095                 break;
1096
1097         case DNS_TYPE_SOA:
1098                 r = dns_packet_read_name(p, &rr->soa.mname, NULL);
1099                 if (r < 0)
1100                         goto fail;
1101
1102                 r = dns_packet_read_name(p, &rr->soa.rname, NULL);
1103                 if (r < 0)
1104                         goto fail;
1105
1106                 r = dns_packet_read_uint32(p, &rr->soa.serial, NULL);
1107                 if (r < 0)
1108                         goto fail;
1109
1110                 r = dns_packet_read_uint32(p, &rr->soa.refresh, NULL);
1111                 if (r < 0)
1112                         goto fail;
1113
1114                 r = dns_packet_read_uint32(p, &rr->soa.retry, NULL);
1115                 if (r < 0)
1116                         goto fail;
1117
1118                 r = dns_packet_read_uint32(p, &rr->soa.expire, NULL);
1119                 if (r < 0)
1120                         goto fail;
1121
1122                 r = dns_packet_read_uint32(p, &rr->soa.minimum, NULL);
1123                 break;
1124
1125         case DNS_TYPE_MX:
1126                 r = dns_packet_read_uint16(p, &rr->mx.priority, NULL);
1127                 if (r < 0)
1128                         goto fail;
1129
1130                 r = dns_packet_read_name(p, &rr->mx.exchange, NULL);
1131                 break;
1132
1133         case DNS_TYPE_LOC: {
1134                 uint8_t t;
1135                 size_t pos;
1136
1137                 r = dns_packet_read_uint8(p, &t, &pos);
1138                 if (r < 0)
1139                         goto fail;
1140
1141                 if (t == 0) {
1142                         rr->loc.version = t;
1143
1144                         r = dns_packet_read_uint8(p, &rr->loc.size, NULL);
1145                         if (r < 0)
1146                                 goto fail;
1147
1148                         if (!loc_size_ok(rr->loc.size)) {
1149                                 r = -EBADMSG;
1150                                 goto fail;
1151                         }
1152
1153                         r = dns_packet_read_uint8(p, &rr->loc.horiz_pre, NULL);
1154                         if (r < 0)
1155                                 goto fail;
1156
1157                         if (!loc_size_ok(rr->loc.horiz_pre)) {
1158                                 r = -EBADMSG;
1159                                 goto fail;
1160                         }
1161
1162                         r = dns_packet_read_uint8(p, &rr->loc.vert_pre, NULL);
1163                         if (r < 0)
1164                                 goto fail;
1165
1166                         if (!loc_size_ok(rr->loc.vert_pre)) {
1167                                 r = -EBADMSG;
1168                                 goto fail;
1169                         }
1170
1171                         r = dns_packet_read_uint32(p, &rr->loc.latitude, NULL);
1172                         if (r < 0)
1173                                 goto fail;
1174
1175                         r = dns_packet_read_uint32(p, &rr->loc.longitude, NULL);
1176                         if (r < 0)
1177                                 goto fail;
1178
1179                         r = dns_packet_read_uint32(p, &rr->loc.altitude, NULL);
1180                         if (r < 0)
1181                                 goto fail;
1182
1183                         break;
1184                 } else {
1185                         dns_packet_rewind(p, pos);
1186                         rr->unparseable = true;
1187                         goto unparseable;
1188                 }
1189         }
1190
1191         case DNS_TYPE_SSHFP:
1192                 r = dns_packet_read_uint8(p, &rr->sshfp.algorithm, NULL);
1193                 if (r < 0)
1194                         goto fail;
1195
1196                 r = dns_packet_read_uint8(p, &rr->sshfp.fptype, NULL);
1197                 if (r < 0)
1198                         goto fail;
1199
1200                 r = dns_packet_read_public_key(p, rdlength - 2,
1201                                                &rr->sshfp.key, &rr->sshfp.key_size,
1202                                                NULL);
1203                 break;
1204
1205         case DNS_TYPE_DNSKEY: {
1206                 uint16_t flags;
1207                 uint8_t proto;
1208
1209                 r = dns_packet_read_uint16(p, &flags, NULL);
1210                 if (r < 0)
1211                         goto fail;
1212
1213                 r = dnskey_parse_flags(rr, flags);
1214                 if (r < 0)
1215                         goto fail;
1216
1217                 r = dns_packet_read_uint8(p, &proto, NULL);
1218                 if (r < 0)
1219                         goto fail;
1220
1221                 /* protocol is required to be always 3 */
1222                 if (proto != 3) {
1223                         r = -EBADMSG;
1224                         goto fail;
1225                 }
1226
1227                 r = dns_packet_read_uint8(p, &rr->dnskey.algorithm, NULL);
1228                 if (r < 0)
1229                         goto fail;
1230
1231                 r = dns_packet_read_public_key(p, rdlength - 4,
1232                                                &rr->dnskey.key, &rr->dnskey.key_size,
1233                                                NULL);
1234                 break;
1235         }
1236
1237         default:
1238         unparseable:
1239                 r = dns_packet_read(p, rdlength, &d, NULL);
1240                 if (r < 0)
1241                         goto fail;
1242
1243                 rr->generic.data = memdup(d, rdlength);
1244                 if (!rr->generic.data) {
1245                         r = -ENOMEM;
1246                         goto fail;
1247                 }
1248
1249                 rr->generic.size = rdlength;
1250                 break;
1251         }
1252         if (r < 0)
1253                 goto fail;
1254         if (p->rindex != offset + rdlength) {
1255                 r = -EBADMSG;
1256                 goto fail;
1257         }
1258
1259         *ret = rr;
1260         rr = NULL;
1261
1262         if (start)
1263                 *start = saved_rindex;
1264
1265         return 0;
1266 fail:
1267         dns_packet_rewind(p, saved_rindex);
1268         return r;
1269 }
1270
1271 int dns_packet_extract(DnsPacket *p) {
1272         _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
1273         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
1274         size_t saved_rindex;
1275         unsigned n, i;
1276         int r;
1277
1278         saved_rindex = p->rindex;
1279         dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
1280
1281         n = DNS_PACKET_QDCOUNT(p);
1282         if (n > 0) {
1283                 question = dns_question_new(n);
1284                 if (!question) {
1285                         r = -ENOMEM;
1286                         goto finish;
1287                 }
1288
1289                 for (i = 0; i < n; i++) {
1290                         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1291
1292                         r = dns_packet_read_key(p, &key, NULL);
1293                         if (r < 0)
1294                                 goto finish;
1295
1296                         r = dns_question_add(question, key);
1297                         if (r < 0)
1298                                 goto finish;
1299                 }
1300         }
1301
1302         n = DNS_PACKET_RRCOUNT(p);
1303         if (n > 0) {
1304                 answer = dns_answer_new(n);
1305                 if (!answer) {
1306                         r = -ENOMEM;
1307                         goto finish;
1308                 }
1309
1310                 for (i = 0; i < n; i++) {
1311                         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1312
1313                         r = dns_packet_read_rr(p, &rr, NULL);
1314                         if (r < 0)
1315                                 goto finish;
1316
1317                         r = dns_answer_add(answer, rr);
1318                         if (r < 0)
1319                                 goto finish;
1320                 }
1321         }
1322
1323         p->question = question;
1324         question = NULL;
1325
1326         p->answer = answer;
1327         answer = NULL;
1328
1329         r = 0;
1330
1331 finish:
1332         p->rindex = saved_rindex;
1333         return r;
1334 }
1335
1336 static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
1337         [DNS_RCODE_SUCCESS] = "SUCCESS",
1338         [DNS_RCODE_FORMERR] = "FORMERR",
1339         [DNS_RCODE_SERVFAIL] = "SERVFAIL",
1340         [DNS_RCODE_NXDOMAIN] = "NXDOMAIN",
1341         [DNS_RCODE_NOTIMP] = "NOTIMP",
1342         [DNS_RCODE_REFUSED] = "REFUSED",
1343         [DNS_RCODE_YXDOMAIN] = "YXDOMAIN",
1344         [DNS_RCODE_YXRRSET] = "YRRSET",
1345         [DNS_RCODE_NXRRSET] = "NXRRSET",
1346         [DNS_RCODE_NOTAUTH] = "NOTAUTH",
1347         [DNS_RCODE_NOTZONE] = "NOTZONE",
1348         [DNS_RCODE_BADVERS] = "BADVERS",
1349         [DNS_RCODE_BADKEY] = "BADKEY",
1350         [DNS_RCODE_BADTIME] = "BADTIME",
1351         [DNS_RCODE_BADMODE] = "BADMODE",
1352         [DNS_RCODE_BADNAME] = "BADNAME",
1353         [DNS_RCODE_BADALG] = "BADALG",
1354         [DNS_RCODE_BADTRUNC] = "BADTRUNC",
1355 };
1356 DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int);
1357
1358 static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = {
1359         [DNS_PROTOCOL_DNS] = "dns",
1360         [DNS_PROTOCOL_MDNS] = "mdns",
1361         [DNS_PROTOCOL_LLMNR] = "llmnr",
1362 };
1363 DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol);