nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2025 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <resolv/resolv-internal.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <stdint.h>
  23 #include <arpa/nameser.h>
  24 #include <not-cancel.h>
  25
  26 #include "nscd-client.h"
  27 #include "nscd_proto.h"
  28
  29 int __nss_not_use_nscd_hosts;
  30
  31 static int nscd_gethst_r (const char *key, size_t keylen, request_type type,
  32                           struct hostent *resultbuf, char *buffer,
  33                           size_t buflen, struct hostent **result,
  34                           int *h_errnop);
  35
  36
  37 int
  38 __nscd_gethostbyname_r (const char *name, struct hostent *resultbuf,
  39                         char *buffer, size_t buflen, struct hostent **result,
  40                         int *h_errnop)
  41 {
  42   return nscd_gethst_r (name, strlen (name) + 1, GETHOSTBYNAME, resultbuf,
  43                         buffer, buflen, result, h_errnop);
  44 }
  45
  46
  47 int
  48 __nscd_gethostbyname2_r (const char *name, int af, struct hostent *resultbuf,
  49                          char *buffer, size_t buflen, struct hostent **result,
  50                          int *h_errnop)
  51 {
  52   request_type reqtype;
  53
  54   reqtype = af == AF_INET6 ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  55
  56   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  57                         buffer, buflen, result, h_errnop);
  58 }
  59
  60
  61 int
  62 __nscd_gethostbyaddr_r (const void *addr, socklen_t len, int type,
  63                         struct hostent *resultbuf, char *buffer, size_t buflen,
  64                         struct hostent **result, int *h_errnop)
  65 {
  66   request_type reqtype;
  67
  68   if (!((len == INADDRSZ && type == AF_INET)
  69         || (len == IN6ADDRSZ && type == AF_INET6)))
  70     /* LEN and TYPE do not match.  */
  71     return -1;
  72
  73   reqtype = type == AF_INET6 ? GETHOSTBYADDRv6 : GETHOSTBYADDR;
  74
  75   return nscd_gethst_r (addr, len, reqtype, resultbuf, buffer, buflen, result,
  76                         h_errnop);
  77 }
  78
  79
  80 libc_locked_map_ptr (, __hst_map_handle) attribute_hidden;
  81 /* Note that we only free the structure if necessary.  The memory
  82    mapping is not removed since it is not visible to the malloc
  83    handling.  */
  84 void
  85 __nscd_hst_map_freemem (void)
  86 {
  87   if (__hst_map_handle.mapped != NO_MAPPING)
  88     {
  89       void *p = __hst_map_handle.mapped;
  90       __hst_map_handle.mapped = NO_MAPPING;
  91       free (p);
  92     }
  93 }
  94
  95
  96 uint32_t
  97 __nscd_get_nl_timestamp (void)
  98 {
  99   uint32_t retval;
 100   if (__nss_not_use_nscd_hosts != 0)
 101     return 0;
 102
 103   /* __nscd_get_mapping can change hst_map_handle.mapped to NO_MAPPING.
 104    However, __nscd_get_mapping assumes the prior value was not NO_MAPPING.
 105    Thus we have to acquire the lock to prevent this thread from changing
 106    hst_map_handle.mapped to NO_MAPPING while another thread is inside
 107     __nscd_get_mapping.  */
 108   if (!__nscd_acquire_maplock (&__hst_map_handle))
 109     return 0;
 110
 111   struct mapped_database *map = __hst_map_handle.mapped;
 112
 113   if (map == NULL
 114       || (map != NO_MAPPING
 115           && map->head->nscd_certainly_running == 0
 116           && map->head->timestamp + MAPPING_TIMEOUT < time64_now ()))
 117     map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
 118
 119   if (map == NO_MAPPING)
 120     retval = 0;
 121   else
 122     retval = map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
 123
 124   /* Release the lock.  */
 125   __hst_map_handle.lock = 0;
 126
 127   return retval;
 128 }
 129
 130
 131 int __nss_have_localdomain attribute_hidden;
 132
 133 static int
 134 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 135                struct hostent *resultbuf, char *buffer, size_t buflen,
 136                struct hostent **result, int *h_errnop)
 137 {
 138   if (__glibc_unlikely (__nss_have_localdomain >= 0))
 139     {
 140       if (__nss_have_localdomain == 0)
 141         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 142       if (__nss_have_localdomain > 0)
 143         {
 144           __nss_not_use_nscd_hosts = 1;
 145           return -1;
 146         }
 147     }
 148
 149   int gc_cycle;
 150   int nretries = 0;
 151
 152   /* If the mapping is available, try to search there instead of
 153      communicating with the nscd.  */
 154   struct mapped_database *mapped;
 155   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 156                                &gc_cycle);
 157
 158  retry:;
 159   const char *h_name = NULL;
 160   const uint32_t *aliases_len = NULL;
 161   const char *addr_list = NULL;
 162   size_t addr_list_len = 0;
 163   int retval = -1;
 164   const char *recend = (const char *) ~UINTMAX_C (0);
 165   int sock = -1;
 166   hst_response_header hst_resp;
 167   if (mapped != NO_MAPPING)
 168     {
 169       /* No const qualifier, as it can change during garbage collection.  */
 170       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 171                                                     sizeof hst_resp);
 172       if (found != NULL)
 173         {
 174           h_name = (char *) (&found->data[0].hstdata + 1);
 175           hst_resp = found->data[0].hstdata;
 176           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 177           addr_list = ((char *) aliases_len
 178                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 179           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 180           recend = (const char *) found->data + found->recsize;
 181           /* Now check if we can trust hst_resp fields.  If GC is
 182              in progress, it can contain anything.  */
 183           if (mapped->head->gc_cycle != gc_cycle)
 184             {
 185               retval = -2;
 186               goto out;
 187             }
 188
 189           /* The aliases_len array in the mapped database might very
 190              well be unaligned.  We will access it word-wise so on
 191              platforms which do not tolerate unaligned accesses we
 192              need to make an aligned copy.  */
 193           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 194               != 0)
 195             {
 196               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 197                                       * sizeof (uint32_t));
 198               aliases_len = memcpy (tmp, aliases_len,
 199                                     hst_resp.h_aliases_cnt
 200                                     * sizeof (uint32_t));
 201             }
 202           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 203             {
 204               if (hst_resp.h_length == INADDRSZ)
 205                 addr_list += addr_list_len;
 206               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 207             }
 208           if (__builtin_expect ((const char *) addr_list + addr_list_len
 209                                 > recend, 0))
 210             goto out;
 211         }
 212     }
 213
 214   if (h_name == NULL)
 215     {
 216       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 217                                  sizeof (hst_resp));
 218       if (sock == -1)
 219         {
 220           __nss_not_use_nscd_hosts = 1;
 221           goto out;
 222         }
 223     }
 224
 225   /* No value found so far.  */
 226   *result = NULL;
 227
 228   if (__glibc_unlikely (hst_resp.found == -1))
 229     {
 230       /* The daemon does not cache this database.  */
 231       __nss_not_use_nscd_hosts = 1;
 232       goto out_close;
 233     }
 234
 235   if (hst_resp.found == 1)
 236     {
 237       char *cp = buffer;
 238       uintptr_t align1;
 239       uintptr_t align2;
 240       size_t total_len;
 241       ssize_t cnt;
 242       char *ignore;
 243       int n;
 244
 245       /* A first check whether the buffer is sufficiently large is possible.  */
 246       /* Now allocate the buffer the array for the group members.  We must
 247          align the pointer and the base of the h_addr_list pointers.  */
 248       align1 = ((__alignof__ (char *) - ((uintptr_t) cp))
 249                 & (__alignof__ (char *) - 1));
 250       align2 = ((__alignof__ (char *) - ((uintptr_t) (cp + align1 + hst_resp.h_name_len)))
 251                 & (__alignof__ (char *) - 1));
 252       if (buflen < (align1 + hst_resp.h_name_len + align2
 253                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 254                         + 2)
 255                        * sizeof (char *))
 256                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 257                                                   ? INADDRSZ : IN6ADDRSZ)))
 258         {
 259         no_room:
 260           *h_errnop = NETDB_INTERNAL;
 261           __set_errno (ERANGE);
 262           retval = ERANGE;
 263           goto out_close;
 264         }
 265       cp += align1;
 266
 267       /* Prepare the result as far as we can.  */
 268       resultbuf->h_aliases = (char **) cp;
 269       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 270       resultbuf->h_addr_list = (char **) cp;
 271       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 272
 273       resultbuf->h_name = cp;
 274       cp += hst_resp.h_name_len + align2;
 275
 276       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 277         {
 278           resultbuf->h_addrtype = AF_INET;
 279           resultbuf->h_length = INADDRSZ;
 280         }
 281       else
 282         {
 283           resultbuf->h_addrtype = AF_INET6;
 284           resultbuf->h_length = IN6ADDRSZ;
 285         }
 286       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 287         {
 288           resultbuf->h_addr_list[cnt] = cp;
 289           cp += resultbuf->h_length;
 290         }
 291       resultbuf->h_addr_list[cnt] = NULL;
 292
 293       if (h_name == NULL)
 294         {
 295           struct iovec vec[4];
 296
 297           vec[0].iov_base = resultbuf->h_name;
 298           vec[0].iov_len = hst_resp.h_name_len;
 299           total_len = hst_resp.h_name_len;
 300           n = 1;
 301
 302           if (hst_resp.h_aliases_cnt > 0)
 303             {
 304               aliases_len = alloca (hst_resp.h_aliases_cnt
 305                                     * sizeof (uint32_t));
 306               vec[n].iov_base = (void *) aliases_len;
 307               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 308
 309               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 310               ++n;
 311             }
 312
 313           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 314             {
 315               vec[n].iov_base = resultbuf->h_addr_list[0];
 316               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 317
 318               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 319
 320               ++n;
 321             }
 322           else
 323             {
 324               if (hst_resp.h_length == INADDRSZ)
 325                 {
 326                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 327                   vec[n].iov_base = ignore;
 328                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 329
 330                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 331
 332                   ++n;
 333                 }
 334
 335               vec[n].iov_base = resultbuf->h_addr_list[0];
 336               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 337
 338               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 339
 340               ++n;
 341             }
 342
 343           if ((size_t) __readvall (sock, vec, n) != total_len)
 344             goto out_close;
 345         }
 346       else
 347         {
 348           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 349           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 350         }
 351
 352       /*  Now we also can read the aliases.  */
 353       total_len = 0;
 354       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 355         {
 356           resultbuf->h_aliases[cnt] = cp;
 357           cp += aliases_len[cnt];
 358           total_len += aliases_len[cnt];
 359         }
 360       resultbuf->h_aliases[cnt] = NULL;
 361
 362       if (__builtin_expect ((const char *) addr_list + addr_list_len
 363                             + total_len > recend, 0))
 364         {
 365           /* aliases_len array might contain garbage during nscd GC cycle,
 366              retry rather than fail in that case.  */
 367           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 368             retval = -2;
 369           goto out_close;
 370         }
 371       /* See whether this would exceed the buffer capacity.  */
 372       if (__glibc_unlikely (cp > buffer + buflen))
 373         {
 374           /* aliases_len array might contain garbage during nscd GC cycle,
 375              retry rather than fail in that case.  */
 376           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 377             {
 378               retval = -2;
 379               goto out_close;
 380             }
 381           goto no_room;
 382         }
 383
 384       /* And finally read the aliases.  */
 385       if (addr_list == NULL)
 386         {
 387           if (total_len == 0
 388               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 389                   == total_len))
 390             {
 391               retval = 0;
 392               *result = resultbuf;
 393             }
 394         }
 395       else
 396         {
 397           memcpy (resultbuf->h_aliases[0],
 398                   (const char *) addr_list + addr_list_len, total_len);
 399
 400           /* Try to detect corrupt databases.  */
 401           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 402               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 403                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 404                          != '\0')
 405                        break;
 406                    cnt < hst_resp.h_aliases_cnt; }))
 407             {
 408               /* We cannot use the database.  */
 409               if (mapped->head->gc_cycle != gc_cycle)
 410                 retval = -2;
 411               goto out_close;
 412             }
 413
 414           retval = 0;
 415           *result = resultbuf;
 416         }
 417     }
 418   else
 419     {
 420       /* Store the error number.  */
 421       *h_errnop = hst_resp.error;
 422
 423       /* Set errno to 0 to indicate no error, just no found record.  */
 424       __set_errno (0);
 425       /* Even though we have not found anything, the result is zero.  */
 426       retval = 0;
 427     }
 428
 429  out_close:
 430   if (sock != -1)
 431     __close_nocancel_nostatus (sock);
 432  out:
 433   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 434     {
 435       /* When we come here this means there has been a GC cycle while we
 436          were looking for the data.  This means the data might have been
 437          inconsistent.  Retry if possible.  */
 438       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 439         {
 440           /* nscd is just running gc now.  Disable using the mapping.  */
 441           if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
 442             __nscd_unmap (mapped);
 443           mapped = NO_MAPPING;
 444         }
 445
 446       if (retval != -1)
 447         goto retry;
 448     }
 449
 450   return retval;
 451 }