resolv/tst-resolv-edns.c

   1 /* Test EDNS handling in the stub resolver.
   2    Copyright (C) 2016-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <netdb.h>
  21 #include <resolv.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <support/check.h>
  26 #include <support/resolv_test.h>
  27 #include <support/support.h>
  28 #include <support/test-driver.h>
  29 #include <support/xthread.h>
  30
  31 /* Data produced by a test query.  */
  32 struct response_data
  33 {
  34   char *qname;
  35   uint16_t qtype;
  36   struct resolv_edns_info edns;
  37 };
  38
  39 /* Global array used by put_response and get_response to record
  40    response data.  The test DNS server returns the index of the array
  41    element which contains the actual response data.  This enables the
  42    test case to return arbitrary amounts of data with the limited
  43    number of bits which fit into an IP addres.
  44
  45    The volatile specifier is needed because the test case accesses
  46    these variables from a callback function called from a function
  47    which is marked as __THROW (i.e., a leaf function which actually is
  48    not).  */
  49 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
  50 static struct response_data ** volatile response_data_array;
  51 volatile static size_t response_data_count;
  52
  53 /* Extract information from the query, store it in a struct
  54    response_data object, and return its index in the
  55    response_data_array.  */
  56 static unsigned int
  57 put_response (const struct resolv_response_context *ctx,
  58                  const char *qname, uint16_t qtype)
  59 {
  60   xpthread_mutex_lock (&mutex);
  61   ++response_data_count;
  62   /* We only can represent 2**24 indexes in 10.0.0.0/8.  */
  63   TEST_VERIFY (response_data_count < (1 << 24));
  64   response_data_array = xrealloc
  65     (response_data_array, sizeof (*response_data_array) * response_data_count);
  66   unsigned int index = response_data_count - 1;
  67   struct response_data *data = xmalloc (sizeof (*data));
  68   *data = (struct response_data)
  69     {
  70       .qname = xstrdup (qname),
  71       .qtype = qtype,
  72       .edns = ctx->edns,
  73     };
  74   response_data_array[index] = data;
  75   xpthread_mutex_unlock (&mutex);
  76   return index;
  77 }
  78
  79 /* Verify the index into the response_data array and return the data
  80    at it.  */
  81 static struct response_data *
  82 get_response (unsigned int index)
  83 {
  84   xpthread_mutex_lock (&mutex);
  85   TEST_VERIFY_EXIT (index < response_data_count);
  86   struct response_data *result = response_data_array[index];
  87   xpthread_mutex_unlock (&mutex);
  88   return result;
  89 }
  90
  91 /* Deallocate all response data.  */
  92 static void
  93 free_response_data (void)
  94 {
  95   xpthread_mutex_lock (&mutex);
  96   size_t count = response_data_count;
  97   struct response_data **array = response_data_array;
  98   for (unsigned int i = 0; i < count; ++i)
  99     {
 100       struct response_data *data = array[i];
 101       free (data->qname);
 102       free (data);
 103     }
 104   free (array);
 105   response_data_array = NULL;
 106   response_data_count = 0;
 107   xpthread_mutex_unlock (&mutex);
 108 }
 109
 110 #define EDNS_PROBE_EXAMPLE "edns-probe.example"
 111
 112 static void
 113 response (const struct resolv_response_context *ctx,
 114           struct resolv_response_builder *b,
 115           const char *qname, uint16_t qclass, uint16_t qtype)
 116 {
 117   TEST_VERIFY_EXIT (qname != NULL);
 118
 119   const char *qname_compare = qname;
 120
 121   /* The "formerr." prefix can be used to request a FORMERR response on the
 122      first server.  */
 123   bool send_formerr;
 124   if (strncmp ("formerr.", qname, strlen ("formerr.")) == 0)
 125     {
 126       send_formerr = true;
 127       qname_compare = qname + strlen ("formerr.");
 128     }
 129   else
 130     {
 131       send_formerr = false;
 132       qname_compare = qname;
 133     }
 134
 135   /* The "tcp." prefix can be used to request TCP fallback.  */
 136   bool force_tcp;
 137   if (strncmp ("tcp.", qname_compare, strlen ("tcp.")) == 0)
 138     {
 139       force_tcp = true;
 140       qname_compare += strlen ("tcp.");
 141     }
 142   else
 143     force_tcp = false;
 144
 145   enum {edns_probe} requested_qname;
 146   if (strcmp (qname_compare, EDNS_PROBE_EXAMPLE) == 0)
 147     requested_qname = edns_probe;
 148   else
 149     {
 150       support_record_failure ();
 151       printf ("error: unexpected QNAME: %s (reduced: %s)\n",
 152               qname, qname_compare);
 153       return;
 154     }
 155   TEST_VERIFY_EXIT (qclass == C_IN);
 156   struct resolv_response_flags flags = { };
 157   flags.tc = force_tcp && !ctx->tcp;
 158   if (!flags.tc && send_formerr && ctx->server_index == 0)
 159     /* Send a FORMERR for the first full response from the first
 160        server.  */
 161     flags.rcode = 1;          /* FORMERR */
 162   resolv_response_init (b, flags);
 163   resolv_response_add_question (b, qname, qclass, qtype);
 164   if (flags.tc || flags.rcode != 0)
 165     return;
 166
 167   if (test_verbose)
 168     printf ("info: edns=%d payload_size=%d\n",
 169             ctx->edns.active, ctx->edns.payload_size);
 170
 171   /* Encode the response_data object in multiple address records.
 172      Each record carries two bytes of payload data, and an index.  */
 173   resolv_response_section (b, ns_s_an);
 174   switch (requested_qname)
 175     {
 176     case edns_probe:
 177       {
 178         unsigned int index = put_response (ctx, qname, qtype);
 179         switch (qtype)
 180           {
 181           case T_A:
 182             {
 183               uint32_t addr = htonl (0x0a000000 | index);
 184               resolv_response_open_record (b, qname, qclass, qtype, 0);
 185               resolv_response_add_data (b, &addr, sizeof (addr));
 186               resolv_response_close_record (b);
 187             }
 188             break;
 189           case T_AAAA:
 190             {
 191               char addr[16]
 192                 = {0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 193                    index >> 16, index >> 8, index};
 194               resolv_response_open_record (b, qname, qclass, qtype, 0);
 195               resolv_response_add_data (b, &addr, sizeof (addr));
 196               resolv_response_close_record (b);
 197             }
 198           }
 199       }
 200       break;
 201     }
 202 }
 203
 204 /* Update *DATA with data from ADDRESS of SIZE.  Set the corresponding
 205    flag in SHADOW for each byte written.  */
 206 static struct response_data *
 207 decode_address (const void *address, size_t size)
 208 {
 209   switch (size)
 210     {
 211     case 4:
 212       TEST_VERIFY (memcmp (address, "\x0a", 1) == 0);
 213       break;
 214     case 16:
 215       TEST_VERIFY (memcmp (address, "\x20\x01\x0d\xb8", 4) == 0);
 216       break;
 217     default:
 218       FAIL_EXIT1 ("unexpected address size %zu", size);
 219     }
 220   const unsigned char *addr = address;
 221   unsigned int index = addr[size - 3] * 256 * 256
 222     + addr[size - 2] * 256
 223     + addr[size - 1];
 224   return get_response (index);
 225 }
 226
 227 static struct response_data *
 228 decode_hostent (struct hostent *e)
 229 {
 230   TEST_VERIFY_EXIT (e != NULL);
 231   TEST_VERIFY_EXIT (e->h_addr_list[0] != NULL);
 232   TEST_VERIFY (e->h_addr_list[1] == NULL);
 233   return decode_address (e->h_addr_list[0], e->h_length);
 234 }
 235
 236 static struct response_data *
 237 decode_addrinfo (struct addrinfo *ai, int family)
 238 {
 239   struct response_data *data = NULL;
 240   while (ai != NULL)
 241     {
 242       if (ai->ai_family == family)
 243         {
 244           struct response_data *new_data;
 245           switch (family)
 246             {
 247             case AF_INET:
 248               {
 249                 struct sockaddr_in *pin = (struct sockaddr_in *) ai->ai_addr;
 250                 new_data = decode_address (&pin->sin_addr.s_addr, 4);
 251               }
 252               break;
 253             case AF_INET6:
 254               {
 255                 struct sockaddr_in6 *pin = (struct sockaddr_in6 *) ai->ai_addr;
 256                 new_data = decode_address (&pin->sin6_addr.s6_addr, 16);
 257               }
 258               break;
 259             default:
 260               FAIL_EXIT1 ("invalid address family %d", ai->ai_family);
 261             }
 262           if (data == NULL)
 263             data = new_data;
 264           else
 265             /* Check pointer equality because this should be the same
 266                response (same index).  */
 267             TEST_VERIFY (data == new_data);
 268         }
 269       ai = ai->ai_next;
 270     }
 271   TEST_VERIFY_EXIT (data != NULL);
 272   return data;
 273 }
 274
 275 /* Updated by the main test loop in accordance with what is set in
 276    _res.options.  */
 277 static bool use_edns;
 278 static bool use_dnssec;
 279
 280 /* Verify the decoded response data against the flags above.  */
 281 static void
 282 verify_response_data_payload (struct response_data *data,
 283                               size_t expected_payload)
 284 {
 285   bool edns = use_edns || use_dnssec;
 286   TEST_VERIFY (data->edns.active == edns);
 287   if (!edns)
 288     expected_payload = 0;
 289   if (data->edns.payload_size != expected_payload)
 290     {
 291       support_record_failure ();
 292       printf ("error: unexpected payload size %d (edns=%d)\n",
 293               (int) data->edns.payload_size, edns);
 294     }
 295   uint16_t expected_flags = 0;
 296   if (use_dnssec)
 297     expected_flags |= 0x8000;   /* DO flag.  */
 298   if (data->edns.flags != expected_flags)
 299     {
 300       support_record_failure ();
 301       printf ("error: unexpected EDNS flags 0x%04x (edns=%d)\n",
 302               (int) data->edns.flags, edns);
 303     }
 304 }
 305
 306 /* Same as verify_response_data_payload, but use the default
 307    payload.  */
 308 static void
 309 verify_response_data (struct response_data *data)
 310 {
 311   verify_response_data_payload (data, 1200);
 312 }
 313
 314 static void
 315 check_hostent (struct hostent *e)
 316 {
 317   TEST_VERIFY_EXIT (e != NULL);
 318   verify_response_data (decode_hostent (e));
 319 }
 320
 321 static void
 322 do_ai (int family)
 323 {
 324   struct addrinfo hints = { .ai_family = family };
 325   struct addrinfo *ai;
 326   int ret = getaddrinfo (EDNS_PROBE_EXAMPLE, "80", &hints, &ai);
 327   TEST_VERIFY_EXIT (ret == 0);
 328   switch (family)
 329     {
 330     case AF_INET:
 331     case AF_INET6:
 332       verify_response_data (decode_addrinfo (ai, family));
 333       break;
 334     case AF_UNSPEC:
 335       verify_response_data (decode_addrinfo (ai, AF_INET));
 336       verify_response_data (decode_addrinfo (ai, AF_INET6));
 337       break;
 338     default:
 339       FAIL_EXIT1 ("invalid address family %d", family);
 340     }
 341   freeaddrinfo (ai);
 342 }
 343
 344 enum res_op
 345 {
 346   res_op_search,
 347   res_op_query,
 348   res_op_querydomain,
 349   res_op_nsearch,
 350   res_op_nquery,
 351   res_op_nquerydomain,
 352
 353   res_op_last = res_op_nquerydomain,
 354 };
 355
 356 static const char *
 357 res_op_string (enum res_op op)
 358 {
 359   switch (op)
 360     {
 361       case res_op_search:
 362         return "res_search";
 363       case res_op_query:
 364         return "res_query";
 365       case res_op_querydomain:
 366         return "res_querydomain";
 367       case res_op_nsearch:
 368         return "res_nsearch";
 369       case res_op_nquery:
 370         return "res_nquery";
 371       case res_op_nquerydomain:
 372         return "res_nquerydomain";
 373     }
 374   FAIL_EXIT1 ("invalid res_op value %d", (int) op);
 375 }
 376
 377 /* Call libresolv function OP to look up PROBE_NAME, with an answer
 378    buffer of SIZE bytes.  Check that the advertised UDP buffer size is
 379    in fact EXPECTED_BUFFER_SIZE.  */
 380 static void
 381 do_res_search (const char *probe_name, enum res_op op, size_t size,
 382                size_t expected_buffer_size)
 383 {
 384   if (test_verbose)
 385     printf ("info: testing %s with buffer size %zu\n",
 386             res_op_string (op), size);
 387   unsigned char *buffer = xmalloc (size);
 388   int ret = -1;
 389   switch (op)
 390     {
 391     case res_op_search:
 392       ret = res_search (probe_name, C_IN, T_A, buffer, size);
 393       break;
 394     case res_op_query:
 395       ret = res_query (probe_name, C_IN, T_A, buffer, size);
 396       break;
 397     case res_op_nsearch:
 398       ret = res_nsearch (&_res, probe_name, C_IN, T_A, buffer, size);
 399       break;
 400     case res_op_nquery:
 401       ret = res_nquery (&_res, probe_name, C_IN, T_A, buffer, size);
 402       break;
 403     case res_op_querydomain:
 404     case res_op_nquerydomain:
 405       {
 406         char *example_stripped = xstrdup (probe_name);
 407         char *dot_example = strstr (example_stripped, ".example");
 408         if (dot_example != NULL && strcmp (dot_example, ".example") == 0)
 409           {
 410             /* Truncate the domain name.  */
 411             *dot_example = '\0';
 412             if (op == res_op_querydomain)
 413               ret = res_querydomain
 414               (example_stripped, "example", C_IN, T_A, buffer, size);
 415             else
 416               ret = res_nquerydomain
 417                 (&_res, example_stripped, "example", C_IN, T_A, buffer, size);
 418           }
 419         else
 420           FAIL_EXIT1 ("invalid probe name: %s", probe_name);
 421         free (example_stripped);
 422       }
 423       break;
 424     }
 425   TEST_VERIFY_EXIT (ret > 12);
 426   unsigned char *end = buffer + ret;
 427
 428   HEADER *hd = (HEADER *) buffer;
 429   TEST_VERIFY (ntohs (hd->qdcount) == 1);
 430   TEST_VERIFY (ntohs (hd->ancount) == 1);
 431   /* Skip over the header.  */
 432   unsigned char *p = buffer + sizeof (*hd);
 433   /* Skip over the question.  */
 434   ret = dn_skipname (p, end);
 435   TEST_VERIFY_EXIT (ret > 0);
 436   p += ret;
 437   TEST_VERIFY_EXIT (end - p >= 4);
 438   p += 4;
 439   /* Skip over the RNAME and the RR header, but stop at the RDATA
 440      length.  */
 441   ret = dn_skipname (p, end);
 442   TEST_VERIFY_EXIT (ret > 0);
 443   p += ret;
 444   TEST_VERIFY_EXIT (end - p >= 2 + 2 + 4 + 2 + 4);
 445   p += 2 + 2 + 4;
 446   /* The IP address should be 4 bytes long.  */
 447   TEST_VERIFY_EXIT (p[0] == 0);
 448   TEST_VERIFY_EXIT (p[1] == 4);
 449   /* Extract the address information.   */
 450   p += 2;
 451   struct response_data *data = decode_address (p, 4);
 452
 453   verify_response_data_payload (data, expected_buffer_size);
 454
 455   free (buffer);
 456 }
 457
 458 static void
 459 run_test (const char *probe_name)
 460 {
 461   if (test_verbose)
 462     printf ("\ninfo: * use_edns=%d use_dnssec=%d\n",
 463             use_edns, use_dnssec);
 464   check_hostent (gethostbyname (probe_name));
 465   check_hostent (gethostbyname2 (probe_name, AF_INET));
 466   check_hostent (gethostbyname2 (probe_name, AF_INET6));
 467   do_ai (AF_UNSPEC);
 468   do_ai (AF_INET);
 469   do_ai (AF_INET6);
 470
 471   for (int op = 0; op <= res_op_last; ++op)
 472     {
 473       do_res_search (probe_name, op, 301, 512);
 474       do_res_search (probe_name, op, 511, 512);
 475       do_res_search (probe_name, op, 512, 512);
 476       do_res_search (probe_name, op, 513, 513);
 477       do_res_search (probe_name, op, 657, 657);
 478       do_res_search (probe_name, op, 1199, 1199);
 479       do_res_search (probe_name, op, 1200, 1200);
 480       do_res_search (probe_name, op, 1201, 1200);
 481       do_res_search (probe_name, op, 65535, 1200);
 482     }
 483 }
 484
 485 static int
 486 do_test (void)
 487 {
 488   for (int do_edns = 0; do_edns < 2; ++do_edns)
 489     for (int do_dnssec = 0; do_dnssec < 2; ++do_dnssec)
 490       for (int do_tcp = 0; do_tcp < 2; ++do_tcp)
 491         for (int do_formerr = 0; do_formerr < 2; ++do_formerr)
 492           {
 493             struct resolv_test *aux = resolv_test_start
 494               ((struct resolv_redirect_config)
 495                {
 496                  .response_callback = response,
 497                });
 498
 499             use_edns = do_edns;
 500             if (do_edns)
 501               _res.options |= RES_USE_EDNS0;
 502             use_dnssec = do_dnssec;
 503             if (do_dnssec)
 504               _res.options |= RES_USE_DNSSEC;
 505
 506             char *probe_name = xstrdup (EDNS_PROBE_EXAMPLE);
 507             if (do_tcp)
 508               {
 509                 char *n = xasprintf ("tcp.%s", probe_name);
 510                 free (probe_name);
 511                 probe_name = n;
 512               }
 513             if (do_formerr)
 514               {
 515                 /* Send a garbage query in an attempt to trigger EDNS
 516                    fallback.  */
 517                 char *n = xasprintf ("formerr.%s", probe_name);
 518                 gethostbyname (n);
 519                 free (n);
 520               }
 521
 522             run_test (probe_name);
 523
 524             free (probe_name);
 525             resolv_test_end (aux);
 526           }
 527
 528   free_response_data ();
 529   return 0;
 530 }
 531
 532 #include <support/test-driver.c>