nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2015 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.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) internal_function;
  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.options & 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 internal_function
 139 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 140                struct hostent *resultbuf, char *buffer, size_t buflen,
 141                struct hostent **result, int *h_errnop)
 142 {
 143   if (__glibc_unlikely (__nss_have_localdomain >= 0))
 144     {
 145       if (__nss_have_localdomain == 0)
 146         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 147       if (__nss_have_localdomain > 0)
 148         {
 149           __nss_not_use_nscd_hosts = 1;
 150           return -1;
 151         }
 152     }
 153
 154   int gc_cycle;
 155   int nretries = 0;
 156
 157   /* If the mapping is available, try to search there instead of
 158      communicating with the nscd.  */
 159   struct mapped_database *mapped;
 160   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 161                                &gc_cycle);
 162
 163  retry:;
 164   const char *h_name = NULL;
 165   const uint32_t *aliases_len = NULL;
 166   const char *addr_list = NULL;
 167   size_t addr_list_len = 0;
 168   int retval = -1;
 169   const char *recend = (const char *) ~UINTMAX_C (0);
 170   int sock = -1;
 171   hst_response_header hst_resp;
 172   if (mapped != NO_MAPPING)
 173     {
 174       /* No const qualifier, as it can change during garbage collection.  */
 175       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 176                                                     sizeof hst_resp);
 177       if (found != NULL)
 178         {
 179           h_name = (char *) (&found->data[0].hstdata + 1);
 180           hst_resp = found->data[0].hstdata;
 181           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 182           addr_list = ((char *) aliases_len
 183                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 184           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 185           recend = (const char *) found->data + found->recsize;
 186           /* Now check if we can trust hst_resp fields.  If GC is
 187              in progress, it can contain anything.  */
 188           if (mapped->head->gc_cycle != gc_cycle)
 189             {
 190               retval = -2;
 191               goto out;
 192             }
 193
 194 #if !_STRING_ARCH_unaligned
 195           /* The aliases_len array in the mapped database might very
 196              well be unaligned.  We will access it word-wise so on
 197              platforms which do not tolerate unaligned accesses we
 198              need to make an aligned copy.  */
 199           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 200               != 0)
 201             {
 202               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 203                                       * sizeof (uint32_t));
 204               aliases_len = memcpy (tmp, aliases_len,
 205                                     hst_resp.h_aliases_cnt
 206                                     * sizeof (uint32_t));
 207             }
 208 #endif
 209           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 210             {
 211               if (hst_resp.h_length == INADDRSZ)
 212                 addr_list += addr_list_len;
 213               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 214             }
 215           if (__builtin_expect ((const char *) addr_list + addr_list_len
 216                                 > recend, 0))
 217             goto out;
 218         }
 219     }
 220
 221   if (h_name == NULL)
 222     {
 223       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 224                                  sizeof (hst_resp));
 225       if (sock == -1)
 226         {
 227           __nss_not_use_nscd_hosts = 1;
 228           goto out;
 229         }
 230     }
 231
 232   /* No value found so far.  */
 233   *result = NULL;
 234
 235   if (__glibc_unlikely (hst_resp.found == -1))
 236     {
 237       /* The daemon does not cache this database.  */
 238       __nss_not_use_nscd_hosts = 1;
 239       goto out_close;
 240     }
 241
 242   if (hst_resp.found == 1)
 243     {
 244       char *cp = buffer;
 245       uintptr_t align1;
 246       uintptr_t align2;
 247       size_t total_len;
 248       ssize_t cnt;
 249       char *ignore;
 250       int n;
 251
 252       /* A first check whether the buffer is sufficiently large is possible.  */
 253       /* Now allocate the buffer the array for the group members.  We must
 254          align the pointer and the base of the h_addr_list pointers.  */
 255       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 256                 & (__alignof__ (char *) - 1));
 257       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 258                                          - ((char *) 0)))
 259                 & (__alignof__ (char *) - 1));
 260       if (buflen < (align1 + hst_resp.h_name_len + align2
 261                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 262                         + 2)
 263                        * sizeof (char *))
 264                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 265                                                   ? INADDRSZ : IN6ADDRSZ)))
 266         {
 267         no_room:
 268           *h_errnop = NETDB_INTERNAL;
 269           __set_errno (ERANGE);
 270           retval = ERANGE;
 271           goto out_close;
 272         }
 273       cp += align1;
 274
 275       /* Prepare the result as far as we can.  */
 276       resultbuf->h_aliases = (char **) cp;
 277       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 278       resultbuf->h_addr_list = (char **) cp;
 279       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 280
 281       resultbuf->h_name = cp;
 282       cp += hst_resp.h_name_len + align2;
 283
 284       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 285         {
 286           resultbuf->h_addrtype = AF_INET;
 287           resultbuf->h_length = INADDRSZ;
 288         }
 289       else
 290         {
 291           resultbuf->h_addrtype = AF_INET6;
 292           resultbuf->h_length = IN6ADDRSZ;
 293         }
 294       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 295         {
 296           resultbuf->h_addr_list[cnt] = cp;
 297           cp += resultbuf->h_length;
 298         }
 299       resultbuf->h_addr_list[cnt] = NULL;
 300
 301       if (h_name == NULL)
 302         {
 303           struct iovec vec[4];
 304
 305           vec[0].iov_base = resultbuf->h_name;
 306           vec[0].iov_len = hst_resp.h_name_len;
 307           total_len = hst_resp.h_name_len;
 308           n = 1;
 309
 310           if (hst_resp.h_aliases_cnt > 0)
 311             {
 312               aliases_len = alloca (hst_resp.h_aliases_cnt
 313                                     * sizeof (uint32_t));
 314               vec[n].iov_base = (void *) aliases_len;
 315               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 316
 317               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 318               ++n;
 319             }
 320
 321           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 322             {
 323               vec[n].iov_base = resultbuf->h_addr_list[0];
 324               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 325
 326               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 327
 328               ++n;
 329             }
 330           else
 331             {
 332               if (hst_resp.h_length == INADDRSZ)
 333                 {
 334                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 335                   vec[n].iov_base = ignore;
 336                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 337
 338                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 339
 340                   ++n;
 341                 }
 342
 343               vec[n].iov_base = resultbuf->h_addr_list[0];
 344               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 345
 346               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 347
 348               ++n;
 349             }
 350
 351           if ((size_t) __readvall (sock, vec, n) != total_len)
 352             goto out_close;
 353         }
 354       else
 355         {
 356           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 357           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 358         }
 359
 360       /*  Now we also can read the aliases.  */
 361       total_len = 0;
 362       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 363         {
 364           resultbuf->h_aliases[cnt] = cp;
 365           cp += aliases_len[cnt];
 366           total_len += aliases_len[cnt];
 367         }
 368       resultbuf->h_aliases[cnt] = NULL;
 369
 370       if (__builtin_expect ((const char *) addr_list + addr_list_len
 371                             + total_len > recend, 0))
 372         {
 373           /* aliases_len array might contain garbage during nscd GC cycle,
 374              retry rather than fail in that case.  */
 375           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 376             retval = -2;
 377           goto out_close;
 378         }
 379       /* See whether this would exceed the buffer capacity.  */
 380       if (__glibc_unlikely (cp > buffer + buflen))
 381         {
 382           /* aliases_len array might contain garbage during nscd GC cycle,
 383              retry rather than fail in that case.  */
 384           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 385             {
 386               retval = -2;
 387               goto out_close;
 388             }
 389           goto no_room;
 390         }
 391
 392       /* And finally read the aliases.  */
 393       if (addr_list == NULL)
 394         {
 395           if (total_len == 0
 396               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 397                   == total_len))
 398             {
 399               retval = 0;
 400               *result = resultbuf;
 401             }
 402         }
 403       else
 404         {
 405           memcpy (resultbuf->h_aliases[0],
 406                   (const char *) addr_list + addr_list_len, total_len);
 407
 408           /* Try to detect corrupt databases.  */
 409           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 410               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 411                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 412                          != '\0')
 413                        break;
 414                    cnt < hst_resp.h_aliases_cnt; }))
 415             {
 416               /* We cannot use the database.  */
 417               if (mapped->head->gc_cycle != gc_cycle)
 418                 retval = -2;
 419               goto out_close;
 420             }
 421
 422           retval = 0;
 423           *result = resultbuf;
 424         }
 425     }
 426   else
 427     {
 428       /* Store the error number.  */
 429       *h_errnop = hst_resp.error;
 430
 431       /* Set errno to 0 to indicate no error, just no found record.  */
 432       __set_errno (0);
 433       /* Even though we have not found anything, the result is zero.  */
 434       retval = 0;
 435     }
 436
 437  out_close:
 438   if (sock != -1)
 439     close_not_cancel_no_status (sock);
 440  out:
 441   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 442     {
 443       /* When we come here this means there has been a GC cycle while we
 444          were looking for the data.  This means the data might have been
 445          inconsistent.  Retry if possible.  */
 446       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 447         {
 448           /* nscd is just running gc now.  Disable using the mapping.  */
 449           if (atomic_decrement_val (&mapped->counter) == 0)
 450             __nscd_unmap (mapped);
 451           mapped = NO_MAPPING;
 452         }
 453
 454       if (retval != -1)
 455         goto retry;
 456     }
 457
 458   return retval;
 459 }