nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2017 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    <http://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   request_type reqtype;
  44
  45   reqtype = res_use_inet6 () ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  46
  47   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  48                         buffer, buflen, result, h_errnop);
  49 }
  50
  51
  52 int
  53 __nscd_gethostbyname2_r (const char *name, int af, struct hostent *resultbuf,
  54                          char *buffer, size_t buflen, struct hostent **result,
  55                          int *h_errnop)
  56 {
  57   request_type reqtype;
  58
  59   reqtype = af == AF_INET6 ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  60
  61   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  62                         buffer, buflen, result, h_errnop);
  63 }
  64
  65
  66 int
  67 __nscd_gethostbyaddr_r (const void *addr, socklen_t len, int type,
  68                         struct hostent *resultbuf, char *buffer, size_t buflen,
  69                         struct hostent **result, int *h_errnop)
  70 {
  71   request_type reqtype;
  72
  73   if (!((len == INADDRSZ && type == AF_INET)
  74         || (len == IN6ADDRSZ && type == AF_INET6)))
  75     /* LEN and TYPE do not match.  */
  76     return -1;
  77
  78   reqtype = type == AF_INET6 ? GETHOSTBYADDRv6 : GETHOSTBYADDR;
  79
  80   return nscd_gethst_r (addr, len, reqtype, resultbuf, buffer, buflen, result,
  81                         h_errnop);
  82 }
  83
  84
  85 libc_locked_map_ptr (, __hst_map_handle) attribute_hidden;
  86 /* Note that we only free the structure if necessary.  The memory
  87    mapping is not removed since it is not visible to the malloc
  88    handling.  */
  89 libc_freeres_fn (hst_map_free)
  90 {
  91   if (__hst_map_handle.mapped != NO_MAPPING)
  92     {
  93       void *p = __hst_map_handle.mapped;
  94       __hst_map_handle.mapped = NO_MAPPING;
  95       free (p);
  96     }
  97 }
  98
  99
 100 uint32_t
 101 __nscd_get_nl_timestamp (void)
 102 {
 103   uint32_t retval;
 104   if (__nss_not_use_nscd_hosts != 0)
 105     return 0;
 106
 107   /* __nscd_get_mapping can change hst_map_handle.mapped to NO_MAPPING.
 108    However, __nscd_get_mapping assumes the prior value was not NO_MAPPING.
 109    Thus we have to acquire the lock to prevent this thread from changing
 110    hst_map_handle.mapped to NO_MAPPING while another thread is inside
 111     __nscd_get_mapping.  */
 112   if (!__nscd_acquire_maplock (&__hst_map_handle))
 113     return 0;
 114
 115   struct mapped_database *map = __hst_map_handle.mapped;
 116
 117   if (map == NULL
 118       || (map != NO_MAPPING
 119           && map->head->nscd_certainly_running == 0
 120           && map->head->timestamp + MAPPING_TIMEOUT < time (NULL)))
 121     map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
 122
 123   if (map == NO_MAPPING)
 124     retval = 0;
 125   else
 126     retval = map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
 127
 128   /* Release the lock.  */
 129   __hst_map_handle.lock = 0;
 130
 131   return retval;
 132 }
 133
 134
 135 int __nss_have_localdomain attribute_hidden;
 136
 137 static int
 138 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 139                struct hostent *resultbuf, char *buffer, size_t buflen,
 140                struct hostent **result, int *h_errnop)
 141 {
 142   if (__glibc_unlikely (__nss_have_localdomain >= 0))
 143     {
 144       if (__nss_have_localdomain == 0)
 145         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 146       if (__nss_have_localdomain > 0)
 147         {
 148           __nss_not_use_nscd_hosts = 1;
 149           return -1;
 150         }
 151     }
 152
 153   int gc_cycle;
 154   int nretries = 0;
 155
 156   /* If the mapping is available, try to search there instead of
 157      communicating with the nscd.  */
 158   struct mapped_database *mapped;
 159   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 160                                &gc_cycle);
 161
 162  retry:;
 163   const char *h_name = NULL;
 164   const uint32_t *aliases_len = NULL;
 165   const char *addr_list = NULL;
 166   size_t addr_list_len = 0;
 167   int retval = -1;
 168   const char *recend = (const char *) ~UINTMAX_C (0);
 169   int sock = -1;
 170   hst_response_header hst_resp;
 171   if (mapped != NO_MAPPING)
 172     {
 173       /* No const qualifier, as it can change during garbage collection.  */
 174       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 175                                                     sizeof hst_resp);
 176       if (found != NULL)
 177         {
 178           h_name = (char *) (&found->data[0].hstdata + 1);
 179           hst_resp = found->data[0].hstdata;
 180           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 181           addr_list = ((char *) aliases_len
 182                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 183           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 184           recend = (const char *) found->data + found->recsize;
 185           /* Now check if we can trust hst_resp fields.  If GC is
 186              in progress, it can contain anything.  */
 187           if (mapped->head->gc_cycle != gc_cycle)
 188             {
 189               retval = -2;
 190               goto out;
 191             }
 192
 193 #if !_STRING_ARCH_unaligned
 194           /* The aliases_len array in the mapped database might very
 195              well be unaligned.  We will access it word-wise so on
 196              platforms which do not tolerate unaligned accesses we
 197              need to make an aligned copy.  */
 198           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 199               != 0)
 200             {
 201               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 202                                       * sizeof (uint32_t));
 203               aliases_len = memcpy (tmp, aliases_len,
 204                                     hst_resp.h_aliases_cnt
 205                                     * sizeof (uint32_t));
 206             }
 207 #endif
 208           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 209             {
 210               if (hst_resp.h_length == INADDRSZ)
 211                 addr_list += addr_list_len;
 212               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 213             }
 214           if (__builtin_expect ((const char *) addr_list + addr_list_len
 215                                 > recend, 0))
 216             goto out;
 217         }
 218     }
 219
 220   if (h_name == NULL)
 221     {
 222       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 223                                  sizeof (hst_resp));
 224       if (sock == -1)
 225         {
 226           __nss_not_use_nscd_hosts = 1;
 227           goto out;
 228         }
 229     }
 230
 231   /* No value found so far.  */
 232   *result = NULL;
 233
 234   if (__glibc_unlikely (hst_resp.found == -1))
 235     {
 236       /* The daemon does not cache this database.  */
 237       __nss_not_use_nscd_hosts = 1;
 238       goto out_close;
 239     }
 240
 241   if (hst_resp.found == 1)
 242     {
 243       char *cp = buffer;
 244       uintptr_t align1;
 245       uintptr_t align2;
 246       size_t total_len;
 247       ssize_t cnt;
 248       char *ignore;
 249       int n;
 250
 251       /* A first check whether the buffer is sufficiently large is possible.  */
 252       /* Now allocate the buffer the array for the group members.  We must
 253          align the pointer and the base of the h_addr_list pointers.  */
 254       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 255                 & (__alignof__ (char *) - 1));
 256       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 257                                          - ((char *) 0)))
 258                 & (__alignof__ (char *) - 1));
 259       if (buflen < (align1 + hst_resp.h_name_len + align2
 260                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 261                         + 2)
 262                        * sizeof (char *))
 263                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 264                                                   ? INADDRSZ : IN6ADDRSZ)))
 265         {
 266         no_room:
 267           *h_errnop = NETDB_INTERNAL;
 268           __set_errno (ERANGE);
 269           retval = ERANGE;
 270           goto out_close;
 271         }
 272       cp += align1;
 273
 274       /* Prepare the result as far as we can.  */
 275       resultbuf->h_aliases = (char **) cp;
 276       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 277       resultbuf->h_addr_list = (char **) cp;
 278       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 279
 280       resultbuf->h_name = cp;
 281       cp += hst_resp.h_name_len + align2;
 282
 283       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 284         {
 285           resultbuf->h_addrtype = AF_INET;
 286           resultbuf->h_length = INADDRSZ;
 287         }
 288       else
 289         {
 290           resultbuf->h_addrtype = AF_INET6;
 291           resultbuf->h_length = IN6ADDRSZ;
 292         }
 293       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 294         {
 295           resultbuf->h_addr_list[cnt] = cp;
 296           cp += resultbuf->h_length;
 297         }
 298       resultbuf->h_addr_list[cnt] = NULL;
 299
 300       if (h_name == NULL)
 301         {
 302           struct iovec vec[4];
 303
 304           vec[0].iov_base = resultbuf->h_name;
 305           vec[0].iov_len = hst_resp.h_name_len;
 306           total_len = hst_resp.h_name_len;
 307           n = 1;
 308
 309           if (hst_resp.h_aliases_cnt > 0)
 310             {
 311               aliases_len = alloca (hst_resp.h_aliases_cnt
 312                                     * sizeof (uint32_t));
 313               vec[n].iov_base = (void *) aliases_len;
 314               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 315
 316               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 317               ++n;
 318             }
 319
 320           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 321             {
 322               vec[n].iov_base = resultbuf->h_addr_list[0];
 323               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 324
 325               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 326
 327               ++n;
 328             }
 329           else
 330             {
 331               if (hst_resp.h_length == INADDRSZ)
 332                 {
 333                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 334                   vec[n].iov_base = ignore;
 335                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 336
 337                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 338
 339                   ++n;
 340                 }
 341
 342               vec[n].iov_base = resultbuf->h_addr_list[0];
 343               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 344
 345               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 346
 347               ++n;
 348             }
 349
 350           if ((size_t) __readvall (sock, vec, n) != total_len)
 351             goto out_close;
 352         }
 353       else
 354         {
 355           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 356           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 357         }
 358
 359       /*  Now we also can read the aliases.  */
 360       total_len = 0;
 361       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 362         {
 363           resultbuf->h_aliases[cnt] = cp;
 364           cp += aliases_len[cnt];
 365           total_len += aliases_len[cnt];
 366         }
 367       resultbuf->h_aliases[cnt] = NULL;
 368
 369       if (__builtin_expect ((const char *) addr_list + addr_list_len
 370                             + total_len > recend, 0))
 371         {
 372           /* aliases_len array might contain garbage during nscd GC cycle,
 373              retry rather than fail in that case.  */
 374           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 375             retval = -2;
 376           goto out_close;
 377         }
 378       /* See whether this would exceed the buffer capacity.  */
 379       if (__glibc_unlikely (cp > buffer + buflen))
 380         {
 381           /* aliases_len array might contain garbage during nscd GC cycle,
 382              retry rather than fail in that case.  */
 383           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 384             {
 385               retval = -2;
 386               goto out_close;
 387             }
 388           goto no_room;
 389         }
 390
 391       /* And finally read the aliases.  */
 392       if (addr_list == NULL)
 393         {
 394           if (total_len == 0
 395               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 396                   == total_len))
 397             {
 398               retval = 0;
 399               *result = resultbuf;
 400             }
 401         }
 402       else
 403         {
 404           memcpy (resultbuf->h_aliases[0],
 405                   (const char *) addr_list + addr_list_len, total_len);
 406
 407           /* Try to detect corrupt databases.  */
 408           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 409               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 410                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 411                          != '\0')
 412                        break;
 413                    cnt < hst_resp.h_aliases_cnt; }))
 414             {
 415               /* We cannot use the database.  */
 416               if (mapped->head->gc_cycle != gc_cycle)
 417                 retval = -2;
 418               goto out_close;
 419             }
 420
 421           retval = 0;
 422           *result = resultbuf;
 423         }
 424     }
 425   else
 426     {
 427       /* Store the error number.  */
 428       *h_errnop = hst_resp.error;
 429
 430       /* Set errno to 0 to indicate no error, just no found record.  */
 431       __set_errno (0);
 432       /* Even though we have not found anything, the result is zero.  */
 433       retval = 0;
 434     }
 435
 436  out_close:
 437   if (sock != -1)
 438     __close_nocancel_nostatus (sock);
 439  out:
 440   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 441     {
 442       /* When we come here this means there has been a GC cycle while we
 443          were looking for the data.  This means the data might have been
 444          inconsistent.  Retry if possible.  */
 445       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 446         {
 447           /* nscd is just running gc now.  Disable using the mapping.  */
 448           if (atomic_decrement_val (&mapped->counter) == 0)
 449             __nscd_unmap (mapped);
 450           mapped = NO_MAPPING;
 451         }
 452
 453       if (retval != -1)
 454         goto retry;
 455     }
 456
 457   return retval;
 458 }