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
 394                 n = PTR_TO_SIZE(hashmap_get(p->names, name));
 395                 if (n > 0) {
 396                         assert(n < p->size);
 397
 398                         if (n < 0x4000) {
 399                                 r = dns_packet_append_uint16(p, 0xC000 | n, NULL);
 400                                 if (r < 0)
 401                                         goto fail;
 402
 403                                 goto done;
 404                         }
 405                 }
 406
 407                 s = strdup(name);
 408                 if (!s) {
 409                         r = -ENOMEM;
 410                         goto fail;
 411                 }
 412
 413                 r = dns_label_unescape(&name, label, sizeof(label));
 414                 if (r < 0)
 415                         goto fail;
 416
 417                 r = dns_packet_append_label(p, label, r, &n);
 418                 if (r < 0)
 419                         goto fail;
 420
 421                 r = hashmap_ensure_allocated(&p->names, dns_name_hash_func, dns_name_compare_func);
 422                 if (r < 0)
 423                         goto fail;
 424
 425                 r = hashmap_put(p->names, s, SIZE_TO_PTR(n));
 426                 if (r < 0)
 427                         goto fail;
 428
 429                 s = NULL;
 430         }
 431
 432         r = dns_packet_append_uint8(p, 0, NULL);
 433         if (r < 0)
 434                 return r;
 435
 436 done:
 437         if (start)
 438                 *start = saved_size;
 439
 440         return 0;
 441
 442 fail:
 443         dns_packet_truncate(p, saved_size);
 444         return r;
 445 }
 446
 447 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, size_t *start) {
 448         size_t saved_size;
 449         int r;
 450
 451         assert(p);
 452         assert(k);
 453
 454         saved_size = p->size;
 455
 456         r = dns_packet_append_name(p, DNS_RESOURCE_KEY_NAME(k), NULL);
 457         if (r < 0)
 458                 goto fail;
 459
 460         r = dns_packet_append_uint16(p, k->type, NULL);
 461         if (r < 0)
 462                 goto fail;
 463
 464         r = dns_packet_append_uint16(p, k->class, NULL);
 465         if (r < 0)
 466                 goto fail;
 467
 468         if (start)
 469                 *start = saved_size;
 470
 471         return 0;
 472
 473 fail:
 474         dns_packet_truncate(p, saved_size);
 475         return r;
 476 }
 477
 478 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start) {
 479         size_t saved_size, rdlength_offset, end, rdlength;
 480         int r;
 481
 482         assert(p);
 483         assert(rr);
 484
 485         saved_size = p->size;
 486
 487         r = dns_packet_append_key(p, rr->key, NULL);
 488         if (r < 0)
 489                 goto fail;
 490
 491         r = dns_packet_append_uint32(p, rr->ttl, NULL);
 492         if (r < 0)
 493                 goto fail;
 494
 495         /* Initially we write 0 here */
 496         r = dns_packet_append_uint16(p, 0, &rdlength_offset);
 497         if (r < 0)
 498                 goto fail;
 499
 500         switch (rr->unparseable ? _DNS_TYPE_INVALID : rr->key->type) {
 501
 502         case DNS_TYPE_PTR:
 503         case DNS_TYPE_NS:
 504         case DNS_TYPE_CNAME:
 505                 r = dns_packet_append_name(p, rr->ptr.name, NULL);
 506                 break;
 507
 508         case DNS_TYPE_HINFO:
 509                 r = dns_packet_append_string(p, rr->hinfo.cpu, NULL);
 510                 if (r < 0)
 511                         goto fail;
 512
 513                 r = dns_packet_append_string(p, rr->hinfo.os, NULL);
 514                 break;
 515
 516         case DNS_TYPE_SPF: /* exactly the same as TXT */
 517         case DNS_TYPE_TXT: {
 518                 char **s;
 519
 520                 STRV_FOREACH(s, rr->txt.strings) {
 521                         r = dns_packet_append_string(p, *s, NULL);
 522                         if (r < 0)
 523                                 goto fail;
 524                 }
 525
 526                 break;
 527         }
 528
 529         case DNS_TYPE_A:
 530                 r = dns_packet_append_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
 531                 break;
 532
 533         case DNS_TYPE_AAAA:
 534                 r = dns_packet_append_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
 535                 break;
 536
 537         case DNS_TYPE_SOA:
 538                 r = dns_packet_append_name(p, rr->soa.mname, NULL);
 539                 if (r < 0)
 540                         goto fail;
 541
 542                 r = dns_packet_append_name(p, rr->soa.rname, NULL);
 543                 if (r < 0)
 544                         goto fail;
 545
 546                 r = dns_packet_append_uint32(p, rr->soa.serial, NULL);
 547                 if (r < 0)
 548                         goto fail;
 549
 550                 r = dns_packet_append_uint32(p, rr->soa.refresh, NULL);
 551                 if (r < 0)
 552                         goto fail;
 553
 554                 r = dns_packet_append_uint32(p, rr->soa.retry, NULL);
 555                 if (r < 0)
 556                         goto fail;
 557
 558                 r = dns_packet_append_uint32(p, rr->soa.expire, NULL);
 559                 if (r < 0)
 560                         goto fail;
 561
 562                 r = dns_packet_append_uint32(p, rr->soa.minimum, NULL);
 563                 break;
 564
 565         case DNS_TYPE_MX:
 566                 r = dns_packet_append_uint16(p, rr->mx.priority, NULL);
 567                 if (r < 0)
 568                         goto fail;
 569
 570                 r = dns_packet_append_name(p, rr->mx.exchange, NULL);
 571                 break;
 572
 573         case DNS_TYPE_LOC:
 574                 r = dns_packet_append_uint8(p, rr->loc.version, NULL);
 575                 if (r < 0)
 576                         goto fail;
 577
 578                 r = dns_packet_append_uint8(p, rr->loc.size, NULL);
 579                 if (r < 0)
 580                         goto fail;
 581
 582                 r = dns_packet_append_uint8(p, rr->loc.horiz_pre, NULL);
 583                 if (r < 0)
 584                         goto fail;
 585
 586                 r = dns_packet_append_uint8(p, rr->loc.vert_pre, NULL);
 587                 if (r < 0)
 588                         goto fail;
 589
 590                 r = dns_packet_append_uint16(p, rr->loc.latitude, NULL);
 591                 if (r < 0)
 592                         goto fail;
 593
 594                 r = dns_packet_append_uint16(p, rr->loc.longitude, NULL);
 595                 if (r < 0)
 596                         goto fail;
 597
 598                 r = dns_packet_append_uint16(p, rr->loc.altitude, NULL);
 599                 break;
 600
 601         case DNS_TYPE_SRV:
 602         case DNS_TYPE_DNAME:
 603         case DNS_TYPE_SSHFP:
 604         case _DNS_TYPE_INVALID: /* unparseable */
 605         default:
 606
 607                 r = dns_packet_append_blob(p, rr->generic.data, rr->generic.size, NULL);
 608                 break;
 609         }
 610         if (r < 0)
 611                 goto fail;
 612
 613         /* Let's calculate the actual data size and update the field */
 614         rdlength = p->size - rdlength_offset - sizeof(uint16_t);
 615         if (rdlength > 0xFFFF) {
 616                 r = ENOSPC;
 617                 goto fail;
 618         }
 619
 620         end = p->size;
 621         p->size = rdlength_offset;
 622         r = dns_packet_append_uint16(p, rdlength, NULL);
 623         if (r < 0)
 624                 goto fail;
 625         p->size = end;
 626
 627         if (start)
 628                 *start = saved_size;
 629
 630         return 0;
 631
 632 fail:
 633         dns_packet_truncate(p, saved_size);
 634         return r;
 635 }
 636
 637
 638 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
 639         assert(p);
 640
 641         if (p->rindex + sz > p->size)
 642                 return -EMSGSIZE;
 643
 644         if (ret)
 645                 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex;
 646
 647         if (start)
 648                 *start = p->rindex;
 649
 650         p->rindex += sz;
 651         return 0;
 652 }
 653
 654 void dns_packet_rewind(DnsPacket *p, size_t idx) {
 655         assert(p);
 656         assert(idx <= p->size);
 657         assert(idx >= DNS_PACKET_HEADER_SIZE);
 658
 659         p->rindex = idx;
 660 }
 661
 662 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start) {
 663         const void *q;
 664         int r;
 665
 666         assert(p);
 667         assert(d);
 668
 669         r = dns_packet_read(p, sz, &q, start);
 670         if (r < 0)
 671                 return r;
 672
 673         memcpy(d, q, sz);
 674         return 0;
 675 }
 676
 677 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) {
 678         const void *d;
 679         int r;
 680
 681         assert(p);
 682
 683         r = dns_packet_read(p, sizeof(uint8_t), &d, start);
 684         if (r < 0)
 685                 return r;
 686
 687         *ret = ((uint8_t*) d)[0];
 688         return 0;
 689 }
 690
 691 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) {
 692         const void *d;
 693         int r;
 694
 695         assert(p);
 696
 697         r = dns_packet_read(p, sizeof(uint16_t), &d, start);
 698         if (r < 0)
 699                 return r;
 700
 701         *ret = (((uint16_t) ((uint8_t*) d)[0]) << 8) |
 702                 ((uint16_t) ((uint8_t*) d)[1]);
 703         return 0;
 704 }
 705
 706 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) {
 707         const void *d;
 708         int r;
 709
 710         assert(p);
 711
 712         r = dns_packet_read(p, sizeof(uint32_t), &d, start);
 713         if (r < 0)
 714                 return r;
 715
 716         *ret = (((uint32_t) ((uint8_t*) d)[0]) << 24) |
 717                (((uint32_t) ((uint8_t*) d)[1]) << 16) |
 718                (((uint32_t) ((uint8_t*) d)[2]) << 8) |
 719                 ((uint32_t) ((uint8_t*) d)[3]);
 720
 721         return 0;
 722 }
 723
 724 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) {
 725         size_t saved_rindex;
 726         const void *d;
 727         char *t;
 728         uint8_t c;
 729         int r;
 730
 731         assert(p);
 732
 733         saved_rindex = p->rindex;
 734
 735         r = dns_packet_read_uint8(p, &c, NULL);
 736         if (r < 0)
 737                 goto fail;
 738
 739         r = dns_packet_read(p, c, &d, NULL);
 740         if (r < 0)
 741                 goto fail;
 742
 743         if (memchr(d, 0, c)) {
 744                 r = -EBADMSG;
 745                 goto fail;
 746         }
 747
 748         t = strndup(d, c);
 749         if (!t) {
 750                 r = -ENOMEM;
 751                 goto fail;
 752         }
 753
 754         if (!utf8_is_valid(t)) {
 755                 free(t);
 756                 r = -EBADMSG;
 757                 goto fail;
 758         }
 759
 760         *ret = t;
 761
 762         if (start)
 763                 *start = saved_rindex;
 764
 765         return 0;
 766
 767 fail:
 768         dns_packet_rewind(p, saved_rindex);
 769         return r;
 770 }
 771
 772 int dns_packet_read_name(DnsPacket *p, char **_ret, size_t *start) {
 773         size_t saved_rindex, after_rindex = 0;
 774         _cleanup_free_ char *ret = NULL;
 775         size_t n = 0, allocated = 0;
 776         bool first = true;
 777         int r;
 778
 779         assert(p);
 780         assert(_ret);
 781
 782         saved_rindex = p->rindex;
 783
 784         for (;;) {
 785                 uint8_t c, d;
 786
 787                 r = dns_packet_read_uint8(p, &c, NULL);
 788                 if (r < 0)
 789                         goto fail;
 790
 791                 if (c == 0)
 792                         /* End of name */
 793                         break;
 794                 else if (c <= 63) {
 795                         _cleanup_free_ char *t = NULL;
 796                         const char *label;
 797
 798                         /* Literal label */
 799                         r = dns_packet_read(p, c, (const void**) &label, NULL);
 800                         if (r < 0)
 801                                 goto fail;
 802
 803                         r = dns_label_escape(label, c, &t);
 804                         if (r < 0)
 805                                 goto fail;
 806
 807                         if (!GREEDY_REALLOC(ret, allocated, n + !first + strlen(t) + 1)) {
 808                                 r = -ENOMEM;
 809                                 goto fail;
 810                         }
 811
 812                         if (!first)
 813                                 ret[n++] = '.';
 814                         else
 815                                 first = false;
 816
 817                         memcpy(ret + n, t, c);
 818                         n += r;
 819                         continue;
 820                 } else if ((c & 0xc0) == 0xc0) {
 821                         uint16_t ptr;
 822
 823                         /* Pointer */
 824                         r = dns_packet_read_uint8(p, &d, NULL);
 825                         if (r < 0)
 826                                 goto fail;
 827
 828                         ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
 829                         if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= saved_rindex) {
 830                                 r = -EBADMSG;
 831                                 goto fail;
 832                         }
 833
 834                         if (after_rindex == 0)
 835                                 after_rindex = p->rindex;
 836
 837                         p->rindex = ptr;
 838                 } else
 839                         goto fail;
 840         }
 841
 842         if (!GREEDY_REALLOC(ret, allocated, n + 1)) {
 843                 r = -ENOMEM;
 844                 goto fail;
 845         }
 846
 847         ret[n] = 0;
 848
 849         if (after_rindex != 0)
 850                 p->rindex= after_rindex;
 851
 852         *_ret = ret;
 853         ret = NULL;
 854
 855         if (start)
 856                 *start = saved_rindex;
 857
 858         return 0;
 859
 860 fail:
 861         dns_packet_rewind(p, saved_rindex);
 862         return r;
 863 }
 864
 865 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
 866         _cleanup_free_ char *name = NULL;
 867         uint16_t class, type;
 868         DnsResourceKey *key;
 869         size_t saved_rindex;
 870         int r;
 871
 872         assert(p);
 873         assert(ret);
 874
 875         saved_rindex = p->rindex;
 876
 877         r = dns_packet_read_name(p, &name, NULL);
 878         if (r < 0)
 879                 goto fail;
 880
 881         r = dns_packet_read_uint16(p, &type, NULL);
 882         if (r < 0)
 883                 goto fail;
 884
 885         r = dns_packet_read_uint16(p, &class, NULL);
 886         if (r < 0)
 887                 goto fail;
 888
 889         key = dns_resource_key_new_consume(class, type, name);
 890         if (!key) {
 891                 r = -ENOMEM;
 892                 goto fail;
 893         }
 894
 895         name = NULL;
 896         *ret = key;
 897
 898         if (start)
 899                 *start = saved_rindex;
 900
 901         return 0;
 902 fail:
 903         dns_packet_rewind(p, saved_rindex);
 904         return r;
 905 }
 906
 907 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 908         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
 909         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
 910         size_t saved_rindex, offset;
 911         uint16_t rdlength;
 912         const void *d;
 913         int r;
 914
 915         assert(p);
 916         assert(ret);
 917
 918         saved_rindex = p->rindex;
 919
 920         r = dns_packet_read_key(p, &key, NULL);
 921         if (r < 0)
 922                 goto fail;
 923
 924         if (key->class == DNS_CLASS_ANY ||
 925             key->type == DNS_TYPE_ANY) {
 926                 r = -EBADMSG;
 927                 goto fail;
 928         }
 929
 930         rr = dns_resource_record_new(key);
 931         if (!rr) {
 932                 r = -ENOMEM;
 933                 goto fail;
 934         }
 935
 936         r = dns_packet_read_uint32(p, &rr->ttl, NULL);
 937         if (r < 0)
 938                 goto fail;
 939
 940         r = dns_packet_read_uint16(p, &rdlength, NULL);
 941         if (r < 0)
 942                 goto fail;
 943
 944         if (p->rindex + rdlength > p->size) {
 945                 r = -EBADMSG;
 946                 goto fail;
 947         }
 948
 949         offset = p->rindex;
 950
 951         switch (rr->key->type) {
 952
 953         case DNS_TYPE_PTR:
 954         case DNS_TYPE_NS:
 955         case DNS_TYPE_CNAME:
 956                 r = dns_packet_read_name(p, &rr->ptr.name, NULL);
 957                 break;
 958
 959         case DNS_TYPE_HINFO:
 960                 r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
 961                 if (r < 0)
 962                         goto fail;
 963
 964                 r = dns_packet_read_string(p, &rr->hinfo.os, NULL);
 965                 break;
 966
 967         case DNS_TYPE_SPF: /* exactly the same as TXT */
 968         case DNS_TYPE_TXT: {
 969                 char *s;
 970
 971                 while (p->rindex < offset + rdlength) {
 972                         r = dns_packet_read_string(p, &s, NULL);
 973                         if (r < 0)
 974                                 goto fail;
 975
 976                         r = strv_consume(&rr->txt.strings, s);
 977                         if (r < 0)
 978                                 goto fail;
 979                 };
 980                 break;
 981         }
 982
 983         case DNS_TYPE_A:
 984                 r = dns_packet_read_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
 985                 break;
 986
 987         case DNS_TYPE_AAAA:
 988                 r = dns_packet_read_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
 989                 break;
 990
 991         case DNS_TYPE_SOA:
 992                 r = dns_packet_read_name(p, &rr->soa.mname, NULL);
 993                 if (r < 0)
 994                         goto fail;
 995
 996                 r = dns_packet_read_name(p, &rr->soa.rname, NULL);
 997                 if (r < 0)
 998                         goto fail;
 999
1000                 r = dns_packet_read_uint32(p, &rr->soa.serial, NULL);
1001                 if (r < 0)
1002                         goto fail;
1003
1004                 r = dns_packet_read_uint32(p, &rr->soa.refresh, NULL);
1005                 if (r < 0)
1006                         goto fail;
1007
1008                 r = dns_packet_read_uint32(p, &rr->soa.retry, NULL);
1009                 if (r < 0)
1010                         goto fail;
1011
1012                 r = dns_packet_read_uint32(p, &rr->soa.expire, NULL);
1013                 if (r < 0)
1014                         goto fail;
1015
1016                 r = dns_packet_read_uint32(p, &rr->soa.minimum, NULL);
1017                 break;
1018
1019         case DNS_TYPE_MX:
1020                 r = dns_packet_read_uint16(p, &rr->mx.priority, NULL);
1021                 if (r < 0)
1022                         goto fail;
1023
1024                 r = dns_packet_read_name(p, &rr->mx.exchange, NULL);
1025                 break;
1026
1027         case DNS_TYPE_LOC: {
1028                 uint8_t t;
1029                 size_t pos;
1030
1031                 r = dns_packet_read_uint8(p, &t, &pos);
1032                 if (r < 0)
1033                         goto fail;
1034
1035                 if (t == 0) {
1036                         rr->loc.version = t;
1037
1038                         r = dns_packet_read_uint8(p, &rr->loc.size, NULL);
1039                         if (r < 0)
1040                                 goto fail;
1041
1042                         r = dns_packet_read_uint8(p, &rr->loc.horiz_pre, NULL);
1043                         if (r < 0)
1044                                 goto fail;
1045
1046                         r = dns_packet_read_uint8(p, &rr->loc.vert_pre, NULL);
1047                         if (r < 0)
1048                                 goto fail;
1049
1050                         r = dns_packet_read_uint32(p, &rr->loc.latitude, NULL);
1051                         if (r < 0)
1052                                 goto fail;
1053
1054                         r = dns_packet_read_uint32(p, &rr->loc.longitude, NULL);
1055                         if (r < 0)
1056                                 goto fail;
1057
1058                         r = dns_packet_read_uint32(p, &rr->loc.altitude, NULL);
1059                         if (r < 0)
1060                                 goto fail;
1061
1062                         break;
1063                 } else {
1064                         dns_packet_rewind(p, pos);
1065                         rr->unparseable = true;
1066                         /* fall through */
1067                 }
1068         }
1069
1070         case DNS_TYPE_SRV:
1071         case DNS_TYPE_DNAME:
1072         case DNS_TYPE_SSHFP:
1073         default:
1074                 r = dns_packet_read(p, rdlength, &d, NULL);
1075                 if (r < 0)
1076                         goto fail;
1077
1078                 rr->generic.data = memdup(d, rdlength);
1079                 if (!rr->generic.data) {
1080                         r = -ENOMEM;
1081                         goto fail;
1082                 }
1083
1084                 rr->generic.size = rdlength;
1085                 break;
1086         }
1087         if (r < 0)
1088                 goto fail;
1089         if (p->rindex != offset + rdlength) {
1090                 r = -EBADMSG;
1091                 goto fail;
1092         }
1093
1094         *ret = rr;
1095         rr = NULL;
1096
1097         if (start)
1098                 *start = saved_rindex;
1099
1100         return 0;
1101 fail:
1102         dns_packet_rewind(p, saved_rindex);
1103         return r;
1104 }
1105
1106 int dns_packet_extract(DnsPacket *p) {
1107         _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
1108         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
1109         size_t saved_rindex;
1110         unsigned n, i;
1111         int r;
1112
1113         saved_rindex = p->rindex;
1114         dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
1115
1116         n = DNS_PACKET_QDCOUNT(p);
1117         if (n > 0) {
1118                 question = dns_question_new(n);
1119                 if (!question) {
1120                         r = -ENOMEM;
1121                         goto finish;
1122                 }
1123
1124                 for (i = 0; i < n; i++) {
1125                         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1126
1127                         r = dns_packet_read_key(p, &key, NULL);
1128                         if (r < 0)
1129                                 goto finish;
1130
1131                         r = dns_question_add(question, key);
1132                         if (r < 0)
1133                                 goto finish;
1134                 }
1135         }
1136
1137         n = DNS_PACKET_RRCOUNT(p);
1138         if (n > 0) {
1139                 answer = dns_answer_new(n);
1140                 if (!answer) {
1141                         r = -ENOMEM;
1142                         goto finish;
1143                 }
1144
1145                 for (i = 0; i < n; i++) {
1146                         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1147
1148                         r = dns_packet_read_rr(p, &rr, NULL);
1149                         if (r < 0)
1150                                 goto finish;
1151
1152                         r = dns_answer_add(answer, rr);
1153                         if (r < 0)
1154                                 goto finish;
1155                 }
1156         }
1157
1158         p->question = question;
1159         question = NULL;
1160
1161         p->answer = answer;
1162         answer = NULL;
1163
1164         r = 0;
1165
1166 finish:
1167         p->rindex = saved_rindex;
1168         return r;
1169 }
1170
1171 static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
1172         [DNS_RCODE_SUCCESS] = "SUCCESS",
1173         [DNS_RCODE_FORMERR] = "FORMERR",
1174         [DNS_RCODE_SERVFAIL] = "SERVFAIL",
1175         [DNS_RCODE_NXDOMAIN] = "NXDOMAIN",
1176         [DNS_RCODE_NOTIMP] = "NOTIMP",
1177         [DNS_RCODE_REFUSED] = "REFUSED",
1178         [DNS_RCODE_YXDOMAIN] = "YXDOMAIN",
1179         [DNS_RCODE_YXRRSET] = "YRRSET",
1180         [DNS_RCODE_NXRRSET] = "NXRRSET",
1181         [DNS_RCODE_NOTAUTH] = "NOTAUTH",
1182         [DNS_RCODE_NOTZONE] = "NOTZONE",
1183         [DNS_RCODE_BADVERS] = "BADVERS",
1184         [DNS_RCODE_BADKEY] = "BADKEY",
1185         [DNS_RCODE_BADTIME] = "BADTIME",
1186         [DNS_RCODE_BADMODE] = "BADMODE",
1187         [DNS_RCODE_BADNAME] = "BADNAME",
1188         [DNS_RCODE_BADALG] = "BADALG",
1189         [DNS_RCODE_BADTRUNC] = "BADTRUNC",
1190 };
1191 DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int);
1192
1193 static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = {
1194         [DNS_PROTOCOL_DNS] = "dns",
1195         [DNS_PROTOCOL_MDNS] = "mdns",
1196         [DNS_PROTOCOL_LLMNR] = "llmnr",
1197 };
1198 DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol);