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_SRV:
 503                 r = dns_packet_append_uint16(p, rr->srv.priority, NULL);
 504                 if (r < 0)
 505                         goto fail;
 506
 507                 r = dns_packet_append_uint16(p, rr->srv.weight, NULL);
 508                 if (r < 0)
 509                         goto fail;
 510
 511                 r = dns_packet_append_uint16(p, rr->srv.port, NULL);
 512                 if (r < 0)
 513                         goto fail;
 514
 515                 r = dns_packet_append_name(p, rr->srv.name, NULL);
 516                 break;
 517
 518         case DNS_TYPE_PTR:
 519         case DNS_TYPE_NS:
 520         case DNS_TYPE_CNAME:
 521         case DNS_TYPE_DNAME:
 522                 r = dns_packet_append_name(p, rr->ptr.name, NULL);
 523                 break;
 524
 525         case DNS_TYPE_HINFO:
 526                 r = dns_packet_append_string(p, rr->hinfo.cpu, NULL);
 527                 if (r < 0)
 528                         goto fail;
 529
 530                 r = dns_packet_append_string(p, rr->hinfo.os, NULL);
 531                 break;
 532
 533         case DNS_TYPE_SPF: /* exactly the same as TXT */
 534         case DNS_TYPE_TXT: {
 535                 char **s;
 536
 537                 STRV_FOREACH(s, rr->txt.strings) {
 538                         r = dns_packet_append_string(p, *s, NULL);
 539                         if (r < 0)
 540                                 goto fail;
 541                 }
 542
 543                 r = 0;
 544                 break;
 545         }
 546
 547         case DNS_TYPE_A:
 548                 r = dns_packet_append_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
 549                 break;
 550
 551         case DNS_TYPE_AAAA:
 552                 r = dns_packet_append_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
 553                 break;
 554
 555         case DNS_TYPE_SOA:
 556                 r = dns_packet_append_name(p, rr->soa.mname, NULL);
 557                 if (r < 0)
 558                         goto fail;
 559
 560                 r = dns_packet_append_name(p, rr->soa.rname, NULL);
 561                 if (r < 0)
 562                         goto fail;
 563
 564                 r = dns_packet_append_uint32(p, rr->soa.serial, NULL);
 565                 if (r < 0)
 566                         goto fail;
 567
 568                 r = dns_packet_append_uint32(p, rr->soa.refresh, NULL);
 569                 if (r < 0)
 570                         goto fail;
 571
 572                 r = dns_packet_append_uint32(p, rr->soa.retry, NULL);
 573                 if (r < 0)
 574                         goto fail;
 575
 576                 r = dns_packet_append_uint32(p, rr->soa.expire, NULL);
 577                 if (r < 0)
 578                         goto fail;
 579
 580                 r = dns_packet_append_uint32(p, rr->soa.minimum, NULL);
 581                 break;
 582
 583         case DNS_TYPE_MX:
 584                 r = dns_packet_append_uint16(p, rr->mx.priority, NULL);
 585                 if (r < 0)
 586                         goto fail;
 587
 588                 r = dns_packet_append_name(p, rr->mx.exchange, NULL);
 589                 break;
 590
 591         case DNS_TYPE_LOC:
 592                 r = dns_packet_append_uint8(p, rr->loc.version, NULL);
 593                 if (r < 0)
 594                         goto fail;
 595
 596                 r = dns_packet_append_uint8(p, rr->loc.size, NULL);
 597                 if (r < 0)
 598                         goto fail;
 599
 600                 r = dns_packet_append_uint8(p, rr->loc.horiz_pre, NULL);
 601                 if (r < 0)
 602                         goto fail;
 603
 604                 r = dns_packet_append_uint8(p, rr->loc.vert_pre, NULL);
 605                 if (r < 0)
 606                         goto fail;
 607
 608                 r = dns_packet_append_uint16(p, rr->loc.latitude, NULL);
 609                 if (r < 0)
 610                         goto fail;
 611
 612                 r = dns_packet_append_uint16(p, rr->loc.longitude, NULL);
 613                 if (r < 0)
 614                         goto fail;
 615
 616                 r = dns_packet_append_uint16(p, rr->loc.altitude, NULL);
 617                 break;
 618
 619         case DNS_TYPE_SSHFP:
 620                 r = dns_packet_append_uint8(p, rr->sshfp.algorithm, NULL);
 621                 if (r < 0)
 622                         goto fail;
 623                 r = dns_packet_append_uint8(p, rr->sshfp.fptype, NULL);
 624                 if (r < 0)
 625                         goto fail;
 626
 627                 r = dns_packet_append_blob(p, rr->sshfp.key, rr->sshfp.key_size, NULL);
 628                 break;
 629
 630         case _DNS_TYPE_INVALID: /* unparseable */
 631         default:
 632
 633                 r = dns_packet_append_blob(p, rr->generic.data, rr->generic.size, NULL);
 634                 break;
 635         }
 636         if (r < 0)
 637                 goto fail;
 638
 639         /* Let's calculate the actual data size and update the field */
 640         rdlength = p->size - rdlength_offset - sizeof(uint16_t);
 641         if (rdlength > 0xFFFF) {
 642                 r = ENOSPC;
 643                 goto fail;
 644         }
 645
 646         end = p->size;
 647         p->size = rdlength_offset;
 648         r = dns_packet_append_uint16(p, rdlength, NULL);
 649         if (r < 0)
 650                 goto fail;
 651         p->size = end;
 652
 653         if (start)
 654                 *start = saved_size;
 655
 656         return 0;
 657
 658 fail:
 659         dns_packet_truncate(p, saved_size);
 660         return r;
 661 }
 662
 663
 664 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
 665         assert(p);
 666
 667         if (p->rindex + sz > p->size)
 668                 return -EMSGSIZE;
 669
 670         if (ret)
 671                 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex;
 672
 673         if (start)
 674                 *start = p->rindex;
 675
 676         p->rindex += sz;
 677         return 0;
 678 }
 679
 680 void dns_packet_rewind(DnsPacket *p, size_t idx) {
 681         assert(p);
 682         assert(idx <= p->size);
 683         assert(idx >= DNS_PACKET_HEADER_SIZE);
 684
 685         p->rindex = idx;
 686 }
 687
 688 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start) {
 689         const void *q;
 690         int r;
 691
 692         assert(p);
 693         assert(d);
 694
 695         r = dns_packet_read(p, sz, &q, start);
 696         if (r < 0)
 697                 return r;
 698
 699         memcpy(d, q, sz);
 700         return 0;
 701 }
 702
 703 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) {
 704         const void *d;
 705         int r;
 706
 707         assert(p);
 708
 709         r = dns_packet_read(p, sizeof(uint8_t), &d, start);
 710         if (r < 0)
 711                 return r;
 712
 713         *ret = ((uint8_t*) d)[0];
 714         return 0;
 715 }
 716
 717 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) {
 718         const void *d;
 719         int r;
 720
 721         assert(p);
 722
 723         r = dns_packet_read(p, sizeof(uint16_t), &d, start);
 724         if (r < 0)
 725                 return r;
 726
 727         *ret = (((uint16_t) ((uint8_t*) d)[0]) << 8) |
 728                 ((uint16_t) ((uint8_t*) d)[1]);
 729         return 0;
 730 }
 731
 732 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) {
 733         const void *d;
 734         int r;
 735
 736         assert(p);
 737
 738         r = dns_packet_read(p, sizeof(uint32_t), &d, start);
 739         if (r < 0)
 740                 return r;
 741
 742         *ret = (((uint32_t) ((uint8_t*) d)[0]) << 24) |
 743                (((uint32_t) ((uint8_t*) d)[1]) << 16) |
 744                (((uint32_t) ((uint8_t*) d)[2]) << 8) |
 745                 ((uint32_t) ((uint8_t*) d)[3]);
 746
 747         return 0;
 748 }
 749
 750 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) {
 751         size_t saved_rindex;
 752         const void *d;
 753         char *t;
 754         uint8_t c;
 755         int r;
 756
 757         assert(p);
 758
 759         saved_rindex = p->rindex;
 760
 761         r = dns_packet_read_uint8(p, &c, NULL);
 762         if (r < 0)
 763                 goto fail;
 764
 765         r = dns_packet_read(p, c, &d, NULL);
 766         if (r < 0)
 767                 goto fail;
 768
 769         if (memchr(d, 0, c)) {
 770                 r = -EBADMSG;
 771                 goto fail;
 772         }
 773
 774         t = strndup(d, c);
 775         if (!t) {
 776                 r = -ENOMEM;
 777                 goto fail;
 778         }
 779
 780         if (!utf8_is_valid(t)) {
 781                 free(t);
 782                 r = -EBADMSG;
 783                 goto fail;
 784         }
 785
 786         *ret = t;
 787
 788         if (start)
 789                 *start = saved_rindex;
 790
 791         return 0;
 792
 793 fail:
 794         dns_packet_rewind(p, saved_rindex);
 795         return r;
 796 }
 797
 798 int dns_packet_read_name(DnsPacket *p, char **_ret, size_t *start) {
 799         size_t saved_rindex, after_rindex = 0;
 800         _cleanup_free_ char *ret = NULL;
 801         size_t n = 0, allocated = 0;
 802         bool first = true;
 803         int r;
 804
 805         assert(p);
 806         assert(_ret);
 807
 808         saved_rindex = p->rindex;
 809
 810         for (;;) {
 811                 uint8_t c, d;
 812
 813                 r = dns_packet_read_uint8(p, &c, NULL);
 814                 if (r < 0)
 815                         goto fail;
 816
 817                 if (c == 0)
 818                         /* End of name */
 819                         break;
 820                 else if (c <= 63) {
 821                         _cleanup_free_ char *t = NULL;
 822                         const char *label;
 823
 824                         /* Literal label */
 825                         r = dns_packet_read(p, c, (const void**) &label, NULL);
 826                         if (r < 0)
 827                                 goto fail;
 828
 829                         r = dns_label_escape(label, c, &t);
 830                         if (r < 0)
 831                                 goto fail;
 832
 833                         if (!GREEDY_REALLOC(ret, allocated, n + !first + strlen(t) + 1)) {
 834                                 r = -ENOMEM;
 835                                 goto fail;
 836                         }
 837
 838                         if (!first)
 839                                 ret[n++] = '.';
 840                         else
 841                                 first = false;
 842
 843                         memcpy(ret + n, t, r);
 844                         n += r;
 845                         continue;
 846                 } else if ((c & 0xc0) == 0xc0) {
 847                         uint16_t ptr;
 848
 849                         /* Pointer */
 850                         r = dns_packet_read_uint8(p, &d, NULL);
 851                         if (r < 0)
 852                                 goto fail;
 853
 854                         ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
 855                         if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= saved_rindex) {
 856                                 r = -EBADMSG;
 857                                 goto fail;
 858                         }
 859
 860                         if (after_rindex == 0)
 861                                 after_rindex = p->rindex;
 862
 863                         p->rindex = ptr;
 864                 } else
 865                         goto fail;
 866         }
 867
 868         if (!GREEDY_REALLOC(ret, allocated, n + 1)) {
 869                 r = -ENOMEM;
 870                 goto fail;
 871         }
 872
 873         ret[n] = 0;
 874
 875         if (after_rindex != 0)
 876                 p->rindex= after_rindex;
 877
 878         *_ret = ret;
 879         ret = NULL;
 880
 881         if (start)
 882                 *start = saved_rindex;
 883
 884         return 0;
 885
 886 fail:
 887         dns_packet_rewind(p, saved_rindex);
 888         return r;
 889 }
 890
 891 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
 892         _cleanup_free_ char *name = NULL;
 893         uint16_t class, type;
 894         DnsResourceKey *key;
 895         size_t saved_rindex;
 896         int r;
 897
 898         assert(p);
 899         assert(ret);
 900
 901         saved_rindex = p->rindex;
 902
 903         r = dns_packet_read_name(p, &name, NULL);
 904         if (r < 0)
 905                 goto fail;
 906
 907         r = dns_packet_read_uint16(p, &type, NULL);
 908         if (r < 0)
 909                 goto fail;
 910
 911         r = dns_packet_read_uint16(p, &class, NULL);
 912         if (r < 0)
 913                 goto fail;
 914
 915         key = dns_resource_key_new_consume(class, type, name);
 916         if (!key) {
 917                 r = -ENOMEM;
 918                 goto fail;
 919         }
 920
 921         name = NULL;
 922         *ret = key;
 923
 924         if (start)
 925                 *start = saved_rindex;
 926
 927         return 0;
 928 fail:
 929         dns_packet_rewind(p, saved_rindex);
 930         return r;
 931 }
 932
 933 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 934         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
 935         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
 936         size_t saved_rindex, offset;
 937         uint16_t rdlength;
 938         const void *d;
 939         int r;
 940
 941         assert(p);
 942         assert(ret);
 943
 944         saved_rindex = p->rindex;
 945
 946         r = dns_packet_read_key(p, &key, NULL);
 947         if (r < 0)
 948                 goto fail;
 949
 950         if (key->class == DNS_CLASS_ANY ||
 951             key->type == DNS_TYPE_ANY) {
 952                 r = -EBADMSG;
 953                 goto fail;
 954         }
 955
 956         rr = dns_resource_record_new(key);
 957         if (!rr) {
 958                 r = -ENOMEM;
 959                 goto fail;
 960         }
 961
 962         r = dns_packet_read_uint32(p, &rr->ttl, NULL);
 963         if (r < 0)
 964                 goto fail;
 965
 966         r = dns_packet_read_uint16(p, &rdlength, NULL);
 967         if (r < 0)
 968                 goto fail;
 969
 970         if (p->rindex + rdlength > p->size) {
 971                 r = -EBADMSG;
 972                 goto fail;
 973         }
 974
 975         offset = p->rindex;
 976
 977         switch (rr->key->type) {
 978
 979         case DNS_TYPE_SRV:
 980                 r = dns_packet_read_uint16(p, &rr->srv.priority, NULL);
 981                 if (r < 0)
 982                         goto fail;
 983                 r = dns_packet_read_uint16(p, &rr->srv.weight, NULL);
 984                 if (r < 0)
 985                         goto fail;
 986                 r = dns_packet_read_uint16(p, &rr->srv.port, NULL);
 987                 if (r < 0)
 988                         goto fail;
 989                 r = dns_packet_read_name(p, &rr->srv.name, NULL);
 990                 break;
 991
 992         case DNS_TYPE_PTR:
 993         case DNS_TYPE_NS:
 994         case DNS_TYPE_CNAME:
 995         case DNS_TYPE_DNAME:
 996                 r = dns_packet_read_name(p, &rr->ptr.name, NULL);
 997                 break;
 998
 999         case DNS_TYPE_HINFO:
1000                 r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
1001                 if (r < 0)
1002                         goto fail;
1003
1004                 r = dns_packet_read_string(p, &rr->hinfo.os, NULL);
1005                 break;
1006
1007         case DNS_TYPE_SPF: /* exactly the same as TXT */
1008         case DNS_TYPE_TXT: {
1009                 char *s;
1010
1011                 while (p->rindex < offset + rdlength) {
1012                         r = dns_packet_read_string(p, &s, NULL);
1013                         if (r < 0)
1014                                 goto fail;
1015
1016                         r = strv_consume(&rr->txt.strings, s);
1017                         if (r < 0)
1018                                 goto fail;
1019                 }
1020
1021                 r = 0;
1022                 break;
1023         }
1024
1025         case DNS_TYPE_A:
1026                 r = dns_packet_read_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
1027                 break;
1028
1029         case DNS_TYPE_AAAA:
1030                 r = dns_packet_read_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
1031                 break;
1032
1033         case DNS_TYPE_SOA:
1034                 r = dns_packet_read_name(p, &rr->soa.mname, NULL);
1035                 if (r < 0)
1036                         goto fail;
1037
1038                 r = dns_packet_read_name(p, &rr->soa.rname, NULL);
1039                 if (r < 0)
1040                         goto fail;
1041
1042                 r = dns_packet_read_uint32(p, &rr->soa.serial, NULL);
1043                 if (r < 0)
1044                         goto fail;
1045
1046                 r = dns_packet_read_uint32(p, &rr->soa.refresh, NULL);
1047                 if (r < 0)
1048                         goto fail;
1049
1050                 r = dns_packet_read_uint32(p, &rr->soa.retry, NULL);
1051                 if (r < 0)
1052                         goto fail;
1053
1054                 r = dns_packet_read_uint32(p, &rr->soa.expire, NULL);
1055                 if (r < 0)
1056                         goto fail;
1057
1058                 r = dns_packet_read_uint32(p, &rr->soa.minimum, NULL);
1059                 break;
1060
1061         case DNS_TYPE_MX:
1062                 r = dns_packet_read_uint16(p, &rr->mx.priority, NULL);
1063                 if (r < 0)
1064                         goto fail;
1065
1066                 r = dns_packet_read_name(p, &rr->mx.exchange, NULL);
1067                 break;
1068
1069         case DNS_TYPE_LOC: {
1070                 uint8_t t;
1071                 size_t pos;
1072
1073                 r = dns_packet_read_uint8(p, &t, &pos);
1074                 if (r < 0)
1075                         goto fail;
1076
1077                 if (t == 0) {
1078                         rr->loc.version = t;
1079
1080                         r = dns_packet_read_uint8(p, &rr->loc.size, NULL);
1081                         if (r < 0)
1082                                 goto fail;
1083
1084                         r = dns_packet_read_uint8(p, &rr->loc.horiz_pre, NULL);
1085                         if (r < 0)
1086                                 goto fail;
1087
1088                         r = dns_packet_read_uint8(p, &rr->loc.vert_pre, NULL);
1089                         if (r < 0)
1090                                 goto fail;
1091
1092                         r = dns_packet_read_uint32(p, &rr->loc.latitude, NULL);
1093                         if (r < 0)
1094                                 goto fail;
1095
1096                         r = dns_packet_read_uint32(p, &rr->loc.longitude, NULL);
1097                         if (r < 0)
1098                                 goto fail;
1099
1100                         r = dns_packet_read_uint32(p, &rr->loc.altitude, NULL);
1101                         if (r < 0)
1102                                 goto fail;
1103
1104                         break;
1105                 } else {
1106                         dns_packet_rewind(p, pos);
1107                         rr->unparseable = true;
1108                         /* fall through */
1109                 }
1110         }
1111
1112         case DNS_TYPE_SSHFP:
1113
1114                 r = dns_packet_read_uint8(p, &rr->sshfp.algorithm, NULL);
1115                 if (r < 0)
1116                         goto fail;
1117
1118                 r = dns_packet_read_uint8(p, &rr->sshfp.fptype, NULL);
1119                 if (r < 0)
1120                         goto fail;
1121
1122                 r = dns_packet_read(p, rdlength - 2, &d, NULL);
1123                 if (r < 0)
1124                         goto fail;
1125
1126                 rr->sshfp.key = memdup(d, rdlength - 2);
1127                 if (!rr->sshfp.key) {
1128                         r = -ENOMEM;
1129                         goto fail;
1130                 }
1131
1132                 rr->sshfp.key_size = rdlength - 2;
1133                 break;
1134
1135         default:
1136                 r = dns_packet_read(p, rdlength, &d, NULL);
1137                 if (r < 0)
1138                         goto fail;
1139
1140                 rr->generic.data = memdup(d, rdlength);
1141                 if (!rr->generic.data) {
1142                         r = -ENOMEM;
1143                         goto fail;
1144                 }
1145
1146                 rr->generic.size = rdlength;
1147                 break;
1148         }
1149         if (r < 0)
1150                 goto fail;
1151         if (p->rindex != offset + rdlength) {
1152                 r = -EBADMSG;
1153                 goto fail;
1154         }
1155
1156         *ret = rr;
1157         rr = NULL;
1158
1159         if (start)
1160                 *start = saved_rindex;
1161
1162         return 0;
1163 fail:
1164         dns_packet_rewind(p, saved_rindex);
1165         return r;
1166 }
1167
1168 int dns_packet_extract(DnsPacket *p) {
1169         _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
1170         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
1171         size_t saved_rindex;
1172         unsigned n, i;
1173         int r;
1174
1175         saved_rindex = p->rindex;
1176         dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
1177
1178         n = DNS_PACKET_QDCOUNT(p);
1179         if (n > 0) {
1180                 question = dns_question_new(n);
1181                 if (!question) {
1182                         r = -ENOMEM;
1183                         goto finish;
1184                 }
1185
1186                 for (i = 0; i < n; i++) {
1187                         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1188
1189                         r = dns_packet_read_key(p, &key, NULL);
1190                         if (r < 0)
1191                                 goto finish;
1192
1193                         r = dns_question_add(question, key);
1194                         if (r < 0)
1195                                 goto finish;
1196                 }
1197         }
1198
1199         n = DNS_PACKET_RRCOUNT(p);
1200         if (n > 0) {
1201                 answer = dns_answer_new(n);
1202                 if (!answer) {
1203                         r = -ENOMEM;
1204                         goto finish;
1205                 }
1206
1207                 for (i = 0; i < n; i++) {
1208                         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1209
1210                         r = dns_packet_read_rr(p, &rr, NULL);
1211                         if (r < 0)
1212                                 goto finish;
1213
1214                         r = dns_answer_add(answer, rr);
1215                         if (r < 0)
1216                                 goto finish;
1217                 }
1218         }
1219
1220         p->question = question;
1221         question = NULL;
1222
1223         p->answer = answer;
1224         answer = NULL;
1225
1226         r = 0;
1227
1228 finish:
1229         p->rindex = saved_rindex;
1230         return r;
1231 }
1232
1233 static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
1234         [DNS_RCODE_SUCCESS] = "SUCCESS",
1235         [DNS_RCODE_FORMERR] = "FORMERR",
1236         [DNS_RCODE_SERVFAIL] = "SERVFAIL",
1237         [DNS_RCODE_NXDOMAIN] = "NXDOMAIN",
1238         [DNS_RCODE_NOTIMP] = "NOTIMP",
1239         [DNS_RCODE_REFUSED] = "REFUSED",
1240         [DNS_RCODE_YXDOMAIN] = "YXDOMAIN",
1241         [DNS_RCODE_YXRRSET] = "YRRSET",
1242         [DNS_RCODE_NXRRSET] = "NXRRSET",
1243         [DNS_RCODE_NOTAUTH] = "NOTAUTH",
1244         [DNS_RCODE_NOTZONE] = "NOTZONE",
1245         [DNS_RCODE_BADVERS] = "BADVERS",
1246         [DNS_RCODE_BADKEY] = "BADKEY",
1247         [DNS_RCODE_BADTIME] = "BADTIME",
1248         [DNS_RCODE_BADMODE] = "BADMODE",
1249         [DNS_RCODE_BADNAME] = "BADNAME",
1250         [DNS_RCODE_BADALG] = "BADALG",
1251         [DNS_RCODE_BADTRUNC] = "BADTRUNC",
1252 };
1253 DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int);
1254
1255 static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = {
1256         [DNS_PROTOCOL_DNS] = "dns",
1257         [DNS_PROTOCOL_MDNS] = "mdns",
1258         [DNS_PROTOCOL_LLMNR] = "llmnr",
1259 };
1260 DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol);