nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2020 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   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 <resolv/resolv-internal.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <stdint.h>
  24 #include <arpa/nameser.h>
  25 #include <not-cancel.h>
  26
  27 #include "nscd-client.h"
  28 #include "nscd_proto.h"
  29
  30 int __nss_not_use_nscd_hosts;
  31
  32 static int nscd_gethst_r (const char *key, size_t keylen, request_type type,
  33                           struct hostent *resultbuf, char *buffer,
  34                           size_t buflen, struct hostent **result,
  35                           int *h_errnop);
  36
  37
  38 int
  39 __nscd_gethostbyname_r (const char *name, struct hostent *resultbuf,
  40                         char *buffer, size_t buflen, struct hostent **result,
  41                         int *h_errnop)
  42 {
  43   return nscd_gethst_r (name, strlen (name) + 1, GETHOSTBYNAME, resultbuf,
  44                         buffer, buflen, result, h_errnop);
  45 }
  46
  47
  48 int
  49 __nscd_gethostbyname2_r (const char *name, int af, struct hostent *resultbuf,
  50                          char *buffer, size_t buflen, struct hostent **result,
  51                          int *h_errnop)
  52 {
  53   request_type reqtype;
  54
  55   reqtype = af == AF_INET6 ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  56
  57   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  58                         buffer, buflen, result, h_errnop);
  59 }
  60
  61
  62 int
  63 __nscd_gethostbyaddr_r (const void *addr, socklen_t len, int type,
  64                         struct hostent *resultbuf, char *buffer, size_t buflen,
  65                         struct hostent **result, int *h_errnop)
  66 {
  67   request_type reqtype;
  68
  69   if (!((len == INADDRSZ && type == AF_INET)
  70         || (len == IN6ADDRSZ && type == AF_INET6)))
  71     /* LEN and TYPE do not match.  */
  72     return -1;
  73
  74   reqtype = type == AF_INET6 ? GETHOSTBYADDRv6 : GETHOSTBYADDR;
  75
  76   return nscd_gethst_r (addr, len, reqtype, resultbuf, buffer, buflen, result,
  77                         h_errnop);
  78 }
  79
  80
  81 libc_locked_map_ptr (, __hst_map_handle) attribute_hidden;
  82 /* Note that we only free the structure if necessary.  The memory
  83    mapping is not removed since it is not visible to the malloc
  84    handling.  */
  85 libc_freeres_fn (hst_map_free)
  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 < time_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 #if !_STRING_ARCH_unaligned
 190           /* The aliases_len array in the mapped database might very
 191              well be unaligned.  We will access it word-wise so on
 192              platforms which do not tolerate unaligned accesses we
 193              need to make an aligned copy.  */
 194           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 195               != 0)
 196             {
 197               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 198                                       * sizeof (uint32_t));
 199               aliases_len = memcpy (tmp, aliases_len,
 200                                     hst_resp.h_aliases_cnt
 201                                     * sizeof (uint32_t));
 202             }
 203 #endif
 204           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 205             {
 206               if (hst_resp.h_length == INADDRSZ)
 207                 addr_list += addr_list_len;
 208               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 209             }
 210           if (__builtin_expect ((const char *) addr_list + addr_list_len
 211                                 > recend, 0))
 212             goto out;
 213         }
 214     }
 215
 216   if (h_name == NULL)
 217     {
 218       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 219                                  sizeof (hst_resp));
 220       if (sock == -1)
 221         {
 222           __nss_not_use_nscd_hosts = 1;
 223           goto out;
 224         }
 225     }
 226
 227   /* No value found so far.  */
 228   *result = NULL;
 229
 230   if (__glibc_unlikely (hst_resp.found == -1))
 231     {
 232       /* The daemon does not cache this database.  */
 233       __nss_not_use_nscd_hosts = 1;
 234       goto out_close;
 235     }
 236
 237   if (hst_resp.found == 1)
 238     {
 239       char *cp = buffer;
 240       uintptr_t align1;
 241       uintptr_t align2;
 242       size_t total_len;
 243       ssize_t cnt;
 244       char *ignore;
 245       int n;
 246
 247       /* A first check whether the buffer is sufficiently large is possible.  */
 248       /* Now allocate the buffer the array for the group members.  We must
 249          align the pointer and the base of the h_addr_list pointers.  */
 250       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 251                 & (__alignof__ (char *) - 1));
 252       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 253                                          - ((char *) 0)))
 254                 & (__alignof__ (char *) - 1));
 255       if (buflen < (align1 + hst_resp.h_name_len + align2
 256                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 257                         + 2)
 258                        * sizeof (char *))
 259                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 260                                                   ? INADDRSZ : IN6ADDRSZ)))
 261         {
 262         no_room:
 263           *h_errnop = NETDB_INTERNAL;
 264           __set_errno (ERANGE);
 265           retval = ERANGE;
 266           goto out_close;
 267         }
 268       cp += align1;
 269
 270       /* Prepare the result as far as we can.  */
 271       resultbuf->h_aliases = (char **) cp;
 272       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 273       resultbuf->h_addr_list = (char **) cp;
 274       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 275
 276       resultbuf->h_name = cp;
 277       cp += hst_resp.h_name_len + align2;
 278
 279       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 280         {
 281           resultbuf->h_addrtype = AF_INET;
 282           resultbuf->h_length = INADDRSZ;
 283         }
 284       else
 285         {
 286           resultbuf->h_addrtype = AF_INET6;
 287           resultbuf->h_length = IN6ADDRSZ;
 288         }
 289       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 290         {
 291           resultbuf->h_addr_list[cnt] = cp;
 292           cp += resultbuf->h_length;
 293         }
 294       resultbuf->h_addr_list[cnt] = NULL;
 295
 296       if (h_name == NULL)
 297         {
 298           struct iovec vec[4];
 299
 300           vec[0].iov_base = resultbuf->h_name;
 301           vec[0].iov_len = hst_resp.h_name_len;
 302           total_len = hst_resp.h_name_len;
 303           n = 1;
 304
 305           if (hst_resp.h_aliases_cnt > 0)
 306             {
 307               aliases_len = alloca (hst_resp.h_aliases_cnt
 308                                     * sizeof (uint32_t));
 309               vec[n].iov_base = (void *) aliases_len;
 310               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 311
 312               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 313               ++n;
 314             }
 315
 316           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 317             {
 318               vec[n].iov_base = resultbuf->h_addr_list[0];
 319               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 320
 321               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 322
 323               ++n;
 324             }
 325           else
 326             {
 327               if (hst_resp.h_length == INADDRSZ)
 328                 {
 329                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 330                   vec[n].iov_base = ignore;
 331                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 332
 333                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 334
 335                   ++n;
 336                 }
 337
 338               vec[n].iov_base = resultbuf->h_addr_list[0];
 339               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 340
 341               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 342
 343               ++n;
 344             }
 345
 346           if ((size_t) __readvall (sock, vec, n) != total_len)
 347             goto out_close;
 348         }
 349       else
 350         {
 351           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 352           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 353         }
 354
 355       /*  Now we also can read the aliases.  */
 356       total_len = 0;
 357       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 358         {
 359           resultbuf->h_aliases[cnt] = cp;
 360           cp += aliases_len[cnt];
 361           total_len += aliases_len[cnt];
 362         }
 363       resultbuf->h_aliases[cnt] = NULL;
 364
 365       if (__builtin_expect ((const char *) addr_list + addr_list_len
 366                             + total_len > recend, 0))
 367         {
 368           /* aliases_len array might contain garbage during nscd GC cycle,
 369              retry rather than fail in that case.  */
 370           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 371             retval = -2;
 372           goto out_close;
 373         }
 374       /* See whether this would exceed the buffer capacity.  */
 375       if (__glibc_unlikely (cp > buffer + buflen))
 376         {
 377           /* aliases_len array might contain garbage during nscd GC cycle,
 378              retry rather than fail in that case.  */
 379           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 380             {
 381               retval = -2;
 382               goto out_close;
 383             }
 384           goto no_room;
 385         }
 386
 387       /* And finally read the aliases.  */
 388       if (addr_list == NULL)
 389         {
 390           if (total_len == 0
 391               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 392                   == total_len))
 393             {
 394               retval = 0;
 395               *result = resultbuf;
 396             }
 397         }
 398       else
 399         {
 400           memcpy (resultbuf->h_aliases[0],
 401                   (const char *) addr_list + addr_list_len, total_len);
 402
 403           /* Try to detect corrupt databases.  */
 404           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 405               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 406                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 407                          != '\0')
 408                        break;
 409                    cnt < hst_resp.h_aliases_cnt; }))
 410             {
 411               /* We cannot use the database.  */
 412               if (mapped->head->gc_cycle != gc_cycle)
 413                 retval = -2;
 414               goto out_close;
 415             }
 416
 417           retval = 0;
 418           *result = resultbuf;
 419         }
 420     }
 421   else
 422     {
 423       /* Store the error number.  */
 424       *h_errnop = hst_resp.error;
 425
 426       /* Set errno to 0 to indicate no error, just no found record.  */
 427       __set_errno (0);
 428       /* Even though we have not found anything, the result is zero.  */
 429       retval = 0;
 430     }
 431
 432  out_close:
 433   if (sock != -1)
 434     __close_nocancel_nostatus (sock);
 435  out:
 436   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 437     {
 438       /* When we come here this means there has been a GC cycle while we
 439          were looking for the data.  This means the data might have been
 440          inconsistent.  Retry if possible.  */
 441       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 442         {
 443           /* nscd is just running gc now.  Disable using the mapping.  */
 444           if (atomic_decrement_val (&mapped->counter) == 0)
 445             __nscd_unmap (mapped);
 446           mapped = NO_MAPPING;
 447         }
 448
 449       if (retval != -1)
 450         goto retry;
 451     }
 452
 453   return retval;
 454 }