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 "resolved-dns-domain.h"
  25 #include "resolved-dns-packet.h"
  26
  27 int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
  28         DnsPacket *p;
  29         size_t a;
  30
  31         assert(ret);
  32
  33         if (mtu <= 0)
  34                 a = DNS_PACKET_SIZE_START;
  35         else
  36                 a = mtu;
  37
  38         if (a < DNS_PACKET_HEADER_SIZE)
  39                 a = DNS_PACKET_HEADER_SIZE;
  40
  41         /* round up to next page size */
  42         a = PAGE_ALIGN(ALIGN(sizeof(DnsPacket)) + a) - ALIGN(sizeof(DnsPacket));
  43
  44         /* make sure we never allocate more than useful */
  45         if (a > DNS_PACKET_SIZE_MAX)
  46                 a = DNS_PACKET_SIZE_MAX;
  47
  48         p = malloc0(ALIGN(sizeof(DnsPacket)) + a);
  49         if (!p)
  50                 return -ENOMEM;
  51
  52         p->size = p->rindex = DNS_PACKET_HEADER_SIZE;
  53         p->allocated = a;
  54         p->protocol = protocol;
  55         p->n_ref = 1;
  56
  57         *ret = p;
  58
  59         return 0;
  60 }
  61
  62 int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
  63         DnsPacket *p;
  64         DnsPacketHeader *h;
  65         int r;
  66
  67         assert(ret);
  68
  69         r = dns_packet_new(&p, protocol, mtu);
  70         if (r < 0)
  71                 return r;
  72
  73         h = DNS_PACKET_HEADER(p);
  74
  75         if (protocol == DNS_PROTOCOL_LLMNR)
  76                 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
  77                                                          0 /* opcode */,
  78                                                          0 /* c */,
  79                                                          0 /* tc */,
  80                                                          0 /* t */,
  81                                                          0 /* ra */,
  82                                                          0 /* ad */,
  83                                                          0 /* cd */,
  84                                                          0 /* rcode */));
  85         else
  86                 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
  87                                                          0 /* opcode */,
  88                                                          0 /* aa */,
  89                                                          0 /* tc */,
  90                                                          1 /* rd (ask for recursion) */,
  91                                                          0 /* ra */,
  92                                                          0 /* ad */,
  93                                                          0 /* cd */,
  94                                                          0 /* rcode */));
  95
  96         *ret = p;
  97         return 0;
  98 }
  99
 100 DnsPacket *dns_packet_ref(DnsPacket *p) {
 101
 102         if (!p)
 103                 return NULL;
 104
 105         assert(p->n_ref > 0);
 106         p->n_ref++;
 107         return p;
 108 }
 109
 110 static void dns_packet_free(DnsPacket *p) {
 111         char *s;
 112
 113         assert(p);
 114
 115         dns_question_unref(p->question);
 116         dns_answer_unref(p->answer);
 117
 118         while ((s = hashmap_steal_first_key(p->names)))
 119                 free(s);
 120         hashmap_free(p->names);
 121
 122         free(p->_data);
 123         free(p);
 124 }
 125
 126 DnsPacket *dns_packet_unref(DnsPacket *p) {
 127         if (!p)
 128                 return NULL;
 129
 130         assert(p->n_ref > 0);
 131
 132         if (p->n_ref == 1)
 133                 dns_packet_free(p);
 134         else
 135                 p->n_ref--;
 136
 137         return NULL;
 138 }
 139
 140 int dns_packet_validate(DnsPacket *p) {
 141         assert(p);
 142
 143         if (p->size < DNS_PACKET_HEADER_SIZE)
 144                 return -EBADMSG;
 145
 146         if (p->size > DNS_PACKET_SIZE_MAX)
 147                 return -EBADMSG;
 148
 149         return 1;
 150 }
 151
 152 int dns_packet_validate_reply(DnsPacket *p) {
 153         int r;
 154
 155         assert(p);
 156
 157         r = dns_packet_validate(p);
 158         if (r < 0)
 159                 return r;
 160
 161         if (DNS_PACKET_QR(p) != 1)
 162                 return 0;
 163
 164         if (DNS_PACKET_OPCODE(p) != 0)
 165                 return -EBADMSG;
 166
 167         /* RFC 4795, Section 2.1.1. says to discard all replies with QDCOUNT != 1 */
 168         if (p->protocol == DNS_PROTOCOL_LLMNR &&
 169             DNS_PACKET_QDCOUNT(p) != 1)
 170                 return -EBADMSG;
 171
 172         return 1;
 173 }
 174
 175 int dns_packet_validate_query(DnsPacket *p) {
 176         int r;
 177
 178         assert(p);
 179
 180         r = dns_packet_validate(p);
 181         if (r < 0)
 182                 return r;
 183
 184         if (DNS_PACKET_QR(p) != 0)
 185                 return 0;
 186
 187         if (DNS_PACKET_OPCODE(p) != 0)
 188                 return -EBADMSG;
 189
 190         if (DNS_PACKET_TC(p))
 191                 return -EBADMSG;
 192
 193         /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
 194         if (p->protocol == DNS_PROTOCOL_LLMNR &&
 195             DNS_PACKET_QDCOUNT(p) != 1)
 196                 return -EBADMSG;
 197
 198         /* RFC 4795, Section 2.1.1. says to discard all queries with ANCOUNT != 0 */
 199         if (DNS_PACKET_ANCOUNT(p) > 0)
 200                 return -EBADMSG;
 201
 202         /* RFC 4795, Section 2.1.1. says to discard all queries with NSCOUNT != 0 */
 203         if (DNS_PACKET_NSCOUNT(p) > 0)
 204                 return -EBADMSG;
 205
 206         return 1;
 207 }
 208
 209 static int dns_packet_extend(DnsPacket *p, size_t add, void **ret, size_t *start) {
 210         assert(p);
 211
 212         if (p->size + add > p->allocated) {
 213                 size_t a;
 214
 215                 a = PAGE_ALIGN((p->size + add) * 2);
 216                 if (a > DNS_PACKET_SIZE_MAX)
 217                         a = DNS_PACKET_SIZE_MAX;
 218
 219                 if (p->size + add > a)
 220                         return -EMSGSIZE;
 221
 222                 if (p->_data) {
 223                         void *d;
 224
 225                         d = realloc(p->_data, a);
 226                         if (!d)
 227                                 return -ENOMEM;
 228
 229                         p->_data = d;
 230                 } else {
 231                         p->_data = malloc(a);
 232                         if (!p->_data)
 233                                 return -ENOMEM;
 234
 235                         memcpy(p->_data, (uint8_t*) p + ALIGN(sizeof(DnsPacket)), p->size);
 236                         memzero((uint8_t*) p->_data + p->size, a - p->size);
 237                 }
 238
 239                 p->allocated = a;
 240         }
 241
 242         if (start)
 243                 *start = p->size;
 244
 245         if (ret)
 246                 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->size;
 247
 248         p->size += add;
 249         return 0;
 250 }
 251
 252 static void dns_packet_truncate(DnsPacket *p, size_t sz) {
 253         Iterator i;
 254         char *s;
 255         void *n;
 256
 257         assert(p);
 258
 259         if (p->size <= sz)
 260                 return;
 261
 262         HASHMAP_FOREACH_KEY(s, n, p->names, i) {
 263
 264                 if (PTR_TO_SIZE(n) < sz)
 265                         continue;
 266
 267                 hashmap_remove(p->names, s);
 268                 free(s);
 269         }
 270
 271         p->size = sz;
 272 }
 273
 274 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t l, size_t *start) {
 275         void *q;
 276         int r;
 277
 278         assert(p);
 279
 280         r = dns_packet_extend(p, l, &q, start);
 281         if (r < 0)
 282                 return r;
 283
 284         memcpy(q, d, l);
 285         return 0;
 286 }
 287
 288 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start) {
 289         void *d;
 290         int r;
 291
 292         assert(p);
 293
 294         r = dns_packet_extend(p, sizeof(uint8_t), &d, start);
 295         if (r < 0)
 296                 return r;
 297
 298         ((uint8_t*) d)[0] = v;
 299
 300         return 0;
 301 }
 302
 303 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start) {
 304         void *d;
 305         int r;
 306
 307         assert(p);
 308
 309         r = dns_packet_extend(p, sizeof(uint16_t), &d, start);
 310         if (r < 0)
 311                 return r;
 312
 313         ((uint8_t*) d)[0] = (uint8_t) (v >> 8);
 314         ((uint8_t*) d)[1] = (uint8_t) v;
 315
 316         return 0;
 317 }
 318
 319 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start) {
 320         void *d;
 321         int r;
 322
 323         assert(p);
 324
 325         r = dns_packet_extend(p, sizeof(uint32_t), &d, start);
 326         if (r < 0)
 327                 return r;
 328
 329         ((uint8_t*) d)[0] = (uint8_t) (v >> 24);
 330         ((uint8_t*) d)[1] = (uint8_t) (v >> 16);
 331         ((uint8_t*) d)[2] = (uint8_t) (v >> 8);
 332         ((uint8_t*) d)[3] = (uint8_t) v;
 333
 334         return 0;
 335 }
 336
 337 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start) {
 338         void *d;
 339         size_t l;
 340         int r;
 341
 342         assert(p);
 343         assert(s);
 344
 345         l = strlen(s);
 346         if (l > 255)
 347                 return -E2BIG;
 348
 349         r = dns_packet_extend(p, 1 + l, &d, start);
 350         if (r < 0)
 351                 return r;
 352
 353         ((uint8_t*) d)[0] = (uint8_t) l;
 354         memcpy(((uint8_t*) d) + 1, s, l);
 355
 356         return 0;
 357 }
 358
 359 int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, size_t *start) {
 360         void *w;
 361         int r;
 362
 363         assert(p);
 364         assert(d);
 365
 366         if (l > DNS_LABEL_MAX)
 367                 return -E2BIG;
 368
 369         r = dns_packet_extend(p, 1 + l, &w, start);
 370         if (r < 0)
 371                 return r;
 372
 373         ((uint8_t*) w)[0] = (uint8_t) l;
 374         memcpy(((uint8_t*) w) + 1, d, l);
 375
 376         return 0;
 377 }
 378
 379 int dns_packet_append_name(DnsPacket *p, const char *name, size_t *start) {
 380         size_t saved_size;
 381         int r;
 382
 383         assert(p);
 384         assert(name);
 385
 386         saved_size = p->size;
 387
 388         while (*name) {
 389                 _cleanup_free_ char *s = NULL;
 390                 char label[DNS_LABEL_MAX];
 391                 size_t n;
 392
 393                 n = PTR_TO_SIZE(hashmap_get(p->names, name));
 394                 if (n > 0) {
 395                         assert(n < p->size);
 396
 397                         if (n < 0x4000) {
 398                                 r = dns_packet_append_uint16(p, 0xC000 | n, NULL);
 399                                 if (r < 0)
 400                                         goto fail;
 401
 402                                 goto done;
 403                         }
 404                 }
 405
 406                 s = strdup(name);
 407                 if (!s) {
 408                         r = -ENOMEM;
 409                         goto fail;
 410                 }
 411
 412                 r = dns_label_unescape(&name, label, sizeof(label));
 413                 if (r < 0)
 414                         goto fail;
 415
 416                 r = dns_packet_append_label(p, label, r, &n);
 417                 if (r < 0)
 418                         goto fail;
 419
 420                 r = hashmap_ensure_allocated(&p->names, dns_name_hash_func, dns_name_compare_func);
 421                 if (r < 0)
 422                         goto fail;
 423
 424                 r = hashmap_put(p->names, s, SIZE_TO_PTR(n));
 425                 if (r < 0)
 426                         goto fail;
 427
 428                 s = NULL;
 429         }
 430
 431         r = dns_packet_append_uint8(p, 0, NULL);
 432         if (r < 0)
 433                 return r;
 434
 435 done:
 436         if (start)
 437                 *start = saved_size;
 438
 439         return 0;
 440
 441 fail:
 442         dns_packet_truncate(p, saved_size);
 443         return r;
 444 }
 445
 446 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, size_t *start) {
 447         size_t saved_size;
 448         int r;
 449
 450         assert(p);
 451         assert(k);
 452
 453         saved_size = p->size;
 454
 455         r = dns_packet_append_name(p, DNS_RESOURCE_KEY_NAME(k), NULL);
 456         if (r < 0)
 457                 goto fail;
 458
 459         r = dns_packet_append_uint16(p, k->type, NULL);
 460         if (r < 0)
 461                 goto fail;
 462
 463         r = dns_packet_append_uint16(p, k->class, NULL);
 464         if (r < 0)
 465                 goto fail;
 466
 467         if (start)
 468                 *start = saved_size;
 469
 470         return 0;
 471
 472 fail:
 473         dns_packet_truncate(p, saved_size);
 474         return r;
 475 }
 476
 477 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start) {
 478         size_t saved_size, rdlength_offset, end, rdlength;
 479         int r;
 480
 481         assert(p);
 482         assert(rr);
 483
 484         saved_size = p->size;
 485
 486         r = dns_packet_append_key(p, rr->key, NULL);
 487         if (r < 0)
 488                 goto fail;
 489
 490         r = dns_packet_append_uint32(p, rr->ttl, NULL);
 491         if (r < 0)
 492                 goto fail;
 493
 494         /* Initially we write 0 here */
 495         r = dns_packet_append_uint16(p, 0, &rdlength_offset);
 496         if (r < 0)
 497                 goto fail;
 498
 499         switch (rr->key->type) {
 500
 501         case DNS_TYPE_PTR:
 502         case DNS_TYPE_NS:
 503         case DNS_TYPE_CNAME:
 504                 r = dns_packet_append_name(p, rr->ptr.name, NULL);
 505                 break;
 506
 507         case DNS_TYPE_HINFO:
 508                 r = dns_packet_append_string(p, rr->hinfo.cpu, NULL);
 509                 if (r < 0)
 510                         goto fail;
 511
 512                 r = dns_packet_append_string(p, rr->hinfo.os, NULL);
 513                 break;
 514
 515         case DNS_TYPE_A:
 516                 r = dns_packet_append_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
 517                 break;
 518
 519         case DNS_TYPE_AAAA:
 520                 r = dns_packet_append_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
 521                 break;
 522
 523         case DNS_TYPE_SOA:
 524                 r = dns_packet_append_name(p, rr->soa.mname, NULL);
 525                 if (r < 0)
 526                         goto fail;
 527
 528                 r = dns_packet_append_name(p, rr->soa.rname, NULL);
 529                 if (r < 0)
 530                         goto fail;
 531
 532                 r = dns_packet_append_uint32(p, rr->soa.serial, NULL);
 533                 if (r < 0)
 534                         goto fail;
 535
 536                 r = dns_packet_append_uint32(p, rr->soa.refresh, NULL);
 537                 if (r < 0)
 538                         goto fail;
 539
 540                 r = dns_packet_append_uint32(p, rr->soa.retry, NULL);
 541                 if (r < 0)
 542                         goto fail;
 543
 544                 r = dns_packet_append_uint32(p, rr->soa.expire, NULL);
 545                 if (r < 0)
 546                         goto fail;
 547
 548                 r = dns_packet_append_uint32(p, rr->soa.minimum, NULL);
 549                 break;
 550
 551         case DNS_TYPE_MX:
 552         case DNS_TYPE_TXT:
 553         case DNS_TYPE_SRV:
 554         case DNS_TYPE_DNAME:
 555         case DNS_TYPE_SSHFP:
 556         default:
 557                 r = dns_packet_append_blob(p, rr->generic.data, rr->generic.size, NULL);
 558                 break;
 559         }
 560         if (r < 0)
 561                 goto fail;
 562
 563         /* Let's calculate the actual data size and update the field */
 564         rdlength = p->size - rdlength_offset - sizeof(uint16_t);
 565         if (rdlength > 0xFFFF) {
 566                 r = ENOSPC;
 567                 goto fail;
 568         }
 569
 570         end = p->size;
 571         p->size = rdlength_offset;
 572         r = dns_packet_append_uint16(p, rdlength, NULL);
 573         if (r < 0)
 574                 goto fail;
 575         p->size = end;
 576
 577         return 0;
 578
 579 fail:
 580         dns_packet_truncate(p, saved_size);
 581         return r;
 582 }
 583
 584
 585 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
 586         assert(p);
 587
 588         if (p->rindex + sz > p->size)
 589                 return -EMSGSIZE;
 590
 591         if (ret)
 592                 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex;
 593
 594         if (start)
 595                 *start = p->rindex;
 596
 597         p->rindex += sz;
 598         return 0;
 599 }
 600
 601 void dns_packet_rewind(DnsPacket *p, size_t idx) {
 602         assert(p);
 603         assert(idx <= p->size);
 604         assert(idx >= DNS_PACKET_HEADER_SIZE);
 605
 606         p->rindex = idx;
 607 }
 608
 609 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start) {
 610         const void *q;
 611         int r;
 612
 613         assert(p);
 614         assert(d);
 615
 616         r = dns_packet_read(p, sz, &q, start);
 617         if (r < 0)
 618                 return r;
 619
 620         memcpy(d, q, sz);
 621         return 0;
 622 }
 623
 624 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) {
 625         const void *d;
 626         int r;
 627
 628         assert(p);
 629
 630         r = dns_packet_read(p, sizeof(uint8_t), &d, start);
 631         if (r < 0)
 632                 return r;
 633
 634         *ret = ((uint8_t*) d)[0];
 635         return 0;
 636 }
 637
 638 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) {
 639         const void *d;
 640         int r;
 641
 642         assert(p);
 643
 644         r = dns_packet_read(p, sizeof(uint16_t), &d, start);
 645         if (r < 0)
 646                 return r;
 647
 648         *ret = (((uint16_t) ((uint8_t*) d)[0]) << 8) |
 649                 ((uint16_t) ((uint8_t*) d)[1]);
 650         return 0;
 651 }
 652
 653 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) {
 654         const void *d;
 655         int r;
 656
 657         assert(p);
 658
 659         r = dns_packet_read(p, sizeof(uint32_t), &d, start);
 660         if (r < 0)
 661                 return r;
 662
 663         *ret = (((uint32_t) ((uint8_t*) d)[0]) << 24) |
 664                (((uint32_t) ((uint8_t*) d)[1]) << 16) |
 665                (((uint32_t) ((uint8_t*) d)[2]) << 8) |
 666                 ((uint32_t) ((uint8_t*) d)[3]);
 667
 668         return 0;
 669 }
 670
 671 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) {
 672         size_t saved_rindex;
 673         const void *d;
 674         char *t;
 675         uint8_t c;
 676         int r;
 677
 678         assert(p);
 679
 680         saved_rindex = p->rindex;
 681
 682         r = dns_packet_read_uint8(p, &c, NULL);
 683         if (r < 0)
 684                 goto fail;
 685
 686         r = dns_packet_read(p, c, &d, NULL);
 687         if (r < 0)
 688                 goto fail;
 689
 690         if (memchr(d, 0, c)) {
 691                 r = -EBADMSG;
 692                 goto fail;
 693         }
 694
 695         t = strndup(d, c);
 696         if (!t) {
 697                 r = -ENOMEM;
 698                 goto fail;
 699         }
 700
 701         if (!utf8_is_valid(t)) {
 702                 free(t);
 703                 r = -EBADMSG;
 704                 goto fail;
 705         }
 706
 707         *ret = t;
 708
 709         if (start)
 710                 *start = saved_rindex;
 711
 712         return 0;
 713
 714 fail:
 715         dns_packet_rewind(p, saved_rindex);
 716         return r;
 717 }
 718
 719 int dns_packet_read_name(DnsPacket *p, char **_ret, size_t *start) {
 720         size_t saved_rindex, after_rindex = 0;
 721         _cleanup_free_ char *ret = NULL;
 722         size_t n = 0, allocated = 0;
 723         bool first = true;
 724         int r;
 725
 726         assert(p);
 727         assert(_ret);
 728
 729         saved_rindex = p->rindex;
 730
 731         for (;;) {
 732                 uint8_t c, d;
 733
 734                 r = dns_packet_read_uint8(p, &c, NULL);
 735                 if (r < 0)
 736                         goto fail;
 737
 738                 if (c == 0)
 739                         /* End of name */
 740                         break;
 741                 else if (c <= 63) {
 742                         _cleanup_free_ char *t = NULL;
 743                         const char *label;
 744
 745                         /* Literal label */
 746                         r = dns_packet_read(p, c, (const void**) &label, NULL);
 747                         if (r < 0)
 748                                 goto fail;
 749
 750                         r = dns_label_escape(label, c, &t);
 751                         if (r < 0)
 752                                 goto fail;
 753
 754                         if (!GREEDY_REALLOC(ret, allocated, n + !first + strlen(t) + 1)) {
 755                                 r = -ENOMEM;
 756                                 goto fail;
 757                         }
 758
 759                         if (!first)
 760                                 ret[n++] = '.';
 761                         else
 762                                 first = false;
 763
 764                         memcpy(ret + n, t, c);
 765                         n += r;
 766                         continue;
 767                 } else if ((c & 0xc0) == 0xc0) {
 768                         uint16_t ptr;
 769
 770                         /* Pointer */
 771                         r = dns_packet_read_uint8(p, &d, NULL);
 772                         if (r < 0)
 773                                 goto fail;
 774
 775                         ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
 776                         if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= saved_rindex) {
 777                                 r = -EBADMSG;
 778                                 goto fail;
 779                         }
 780
 781                         if (after_rindex == 0)
 782                                 after_rindex = p->rindex;
 783
 784                         p->rindex = ptr;
 785                 } else
 786                         goto fail;
 787         }
 788
 789         if (!GREEDY_REALLOC(ret, allocated, n + 1)) {
 790                 r = -ENOMEM;
 791                 goto fail;
 792         }
 793
 794         ret[n] = 0;
 795
 796         if (after_rindex != 0)
 797                 p->rindex= after_rindex;
 798
 799         *_ret = ret;
 800         ret = NULL;
 801
 802         if (start)
 803                 *start = saved_rindex;
 804
 805         return 0;
 806
 807 fail:
 808         dns_packet_rewind(p, saved_rindex);
 809         return r;
 810 }
 811
 812 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
 813         _cleanup_free_ char *name = NULL;
 814         uint16_t class, type;
 815         DnsResourceKey *key;
 816         size_t saved_rindex;
 817         int r;
 818
 819         assert(p);
 820         assert(ret);
 821
 822         saved_rindex = p->rindex;
 823
 824         r = dns_packet_read_name(p, &name, NULL);
 825         if (r < 0)
 826                 goto fail;
 827
 828         r = dns_packet_read_uint16(p, &type, NULL);
 829         if (r < 0)
 830                 goto fail;
 831
 832         r = dns_packet_read_uint16(p, &class, NULL);
 833         if (r < 0)
 834                 goto fail;
 835
 836         key = dns_resource_key_new_consume(class, type, name);
 837         if (!key) {
 838                 r = -ENOMEM;
 839                 goto fail;
 840         }
 841
 842         name = NULL;
 843         *ret = key;
 844
 845         if (start)
 846                 *start = saved_rindex;
 847
 848         return 0;
 849 fail:
 850         dns_packet_rewind(p, saved_rindex);
 851         return r;
 852 }
 853
 854 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 855         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
 856         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
 857         size_t saved_rindex, offset;
 858         uint16_t rdlength;
 859         const void *d;
 860         int r;
 861
 862         assert(p);
 863         assert(ret);
 864
 865         saved_rindex = p->rindex;
 866
 867         r = dns_packet_read_key(p, &key, NULL);
 868         if (r < 0)
 869                 goto fail;
 870
 871         if (key->class == DNS_CLASS_ANY ||
 872             key->type == DNS_TYPE_ANY) {
 873                 r = -EBADMSG;
 874                 goto fail;
 875         }
 876
 877         rr = dns_resource_record_new(key);
 878         if (!rr) {
 879                 r = -ENOMEM;
 880                 goto fail;
 881         }
 882
 883         r = dns_packet_read_uint32(p, &rr->ttl, NULL);
 884         if (r < 0)
 885                 goto fail;
 886
 887         r = dns_packet_read_uint16(p, &rdlength, NULL);
 888         if (r < 0)
 889                 goto fail;
 890
 891         if (p->rindex + rdlength > p->size) {
 892                 r = -EBADMSG;
 893                 goto fail;
 894         }
 895
 896         offset = p->rindex;
 897
 898         switch (rr->key->type) {
 899
 900         case DNS_TYPE_PTR:
 901         case DNS_TYPE_NS:
 902         case DNS_TYPE_CNAME:
 903                 r = dns_packet_read_name(p, &rr->ptr.name, NULL);
 904                 break;
 905
 906         case DNS_TYPE_HINFO:
 907                 r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
 908                 if (r < 0)
 909                         goto fail;
 910
 911                 r = dns_packet_read_string(p, &rr->hinfo.os, NULL);
 912                 break;
 913
 914         case DNS_TYPE_A:
 915                 r = dns_packet_read_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
 916                 break;
 917
 918         case DNS_TYPE_AAAA:
 919                 r = dns_packet_read_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
 920                 break;
 921
 922         case DNS_TYPE_SOA:
 923                 r = dns_packet_read_name(p, &rr->soa.mname, NULL);
 924                 if (r < 0)
 925                         goto fail;
 926
 927                 r = dns_packet_read_name(p, &rr->soa.rname, NULL);
 928                 if (r < 0)
 929                         goto fail;
 930
 931                 r = dns_packet_read_uint32(p, &rr->soa.serial, NULL);
 932                 if (r < 0)
 933                         goto fail;
 934
 935                 r = dns_packet_read_uint32(p, &rr->soa.refresh, NULL);
 936                 if (r < 0)
 937                         goto fail;
 938
 939                 r = dns_packet_read_uint32(p, &rr->soa.retry, NULL);
 940                 if (r < 0)
 941                         goto fail;
 942
 943                 r = dns_packet_read_uint32(p, &rr->soa.expire, NULL);
 944                 if (r < 0)
 945                         goto fail;
 946
 947                 r = dns_packet_read_uint32(p, &rr->soa.minimum, NULL);
 948                 break;
 949
 950         case DNS_TYPE_MX:
 951         case DNS_TYPE_TXT:
 952         case DNS_TYPE_SRV:
 953         case DNS_TYPE_DNAME:
 954         case DNS_TYPE_SSHFP:
 955         default:
 956                 r = dns_packet_read(p, rdlength, &d, NULL);
 957                 if (r < 0)
 958                         goto fail;
 959
 960                 rr->generic.data = memdup(d, rdlength);
 961                 if (!rr->generic.data) {
 962                         r = -ENOMEM;
 963                         goto fail;
 964                 }
 965
 966                 rr->generic.size = rdlength;
 967                 break;
 968         }
 969         if (r < 0)
 970                 goto fail;
 971         if (p->rindex != offset + rdlength) {
 972                 r = -EBADMSG;
 973                 goto fail;
 974         }
 975
 976         *ret = rr;
 977         rr = NULL;
 978
 979         if (start)
 980                 *start = saved_rindex;
 981
 982         return 0;
 983 fail:
 984         dns_packet_rewind(p, saved_rindex);
 985         return r;
 986 }
 987
 988 int dns_packet_extract(DnsPacket *p) {
 989         _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
 990         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
 991         size_t saved_rindex;
 992         unsigned n, i;
 993         int r;
 994
 995         saved_rindex = p->rindex;
 996         dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
 997
 998         n = DNS_PACKET_QDCOUNT(p);
 999         if (n > 0) {
1000                 question = dns_question_new(n);
1001                 if (!question) {
1002                         r = -ENOMEM;
1003                         goto finish;
1004                 }
1005
1006                 for (i = 0; i < n; i++) {
1007                         _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1008
1009                         r = dns_packet_read_key(p, &key, NULL);
1010                         if (r < 0)
1011                                 goto finish;
1012
1013                         r = dns_question_add(question, key);
1014                         if (r < 0)
1015                                 goto finish;
1016                 }
1017         }
1018
1019         n = DNS_PACKET_RRCOUNT(p);
1020         if (n > 0) {
1021                 answer = dns_answer_new(n);
1022                 if (!answer) {
1023                         r = -ENOMEM;
1024                         goto finish;
1025                 }
1026
1027                 for (i = 0; i < n; i++) {
1028                         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1029
1030                         r = dns_packet_read_rr(p, &rr, NULL);
1031                         if (r < 0)
1032                                 goto finish;
1033
1034                         r = dns_answer_add(answer, rr);
1035                         if (r < 0)
1036                                 goto finish;
1037                 }
1038         }
1039
1040         p->question = question;
1041         question = NULL;
1042
1043         p->answer = answer;
1044         answer = NULL;
1045
1046         r = 0;
1047
1048 finish:
1049         p->rindex = saved_rindex;
1050         return r;
1051 }
1052
1053 static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
1054         [DNS_RCODE_SUCCESS] = "SUCCESS",
1055         [DNS_RCODE_FORMERR] = "FORMERR",
1056         [DNS_RCODE_SERVFAIL] = "SERVFAIL",
1057         [DNS_RCODE_NXDOMAIN] = "NXDOMAIN",
1058         [DNS_RCODE_NOTIMP] = "NOTIMP",
1059         [DNS_RCODE_REFUSED] = "REFUSED",
1060         [DNS_RCODE_YXDOMAIN] = "YXDOMAIN",
1061         [DNS_RCODE_YXRRSET] = "YRRSET",
1062         [DNS_RCODE_NXRRSET] = "NXRRSET",
1063         [DNS_RCODE_NOTAUTH] = "NOTAUTH",
1064         [DNS_RCODE_NOTZONE] = "NOTZONE",
1065         [DNS_RCODE_BADVERS] = "BADVERS",
1066         [DNS_RCODE_BADKEY] = "BADKEY",
1067         [DNS_RCODE_BADTIME] = "BADTIME",
1068         [DNS_RCODE_BADMODE] = "BADMODE",
1069         [DNS_RCODE_BADNAME] = "BADNAME",
1070         [DNS_RCODE_BADALG] = "BADALG",
1071         [DNS_RCODE_BADTRUNC] = "BADTRUNC",
1072 };
1073 DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int);
1074
1075 static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = {
1076         [DNS_PROTOCOL_DNS] = "dns",
1077         [DNS_PROTOCOL_MDNS] = "mdns",
1078         [DNS_PROTOCOL_LLMNR] = "llmnr",
1079 };
1080 DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol);