nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2005, 2006, 2007, 2008, 2009, 2011
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <resolv.h>
  22 #include <stdio.h>
  23 #include <string.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   if (__nss_not_use_nscd_hosts != 0)
 104     return 0;
 105
 106   struct mapped_database *map = __hst_map_handle.mapped;
 107
 108   if (map == NULL
 109       || (map != NO_MAPPING
 110           && map->head->nscd_certainly_running == 0
 111           && map->head->timestamp + MAPPING_TIMEOUT < time (NULL)))
 112     map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
 113
 114   if (map == NO_MAPPING)
 115     return 0;
 116
 117   return map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
 118 }
 119
 120
 121 int __nss_have_localdomain attribute_hidden;
 122
 123 static int
 124 internal_function
 125 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 126                struct hostent *resultbuf, char *buffer, size_t buflen,
 127                struct hostent **result, int *h_errnop)
 128 {
 129   if (__builtin_expect (__nss_have_localdomain >= 0, 0))
 130     {
 131       if (__nss_have_localdomain == 0)
 132         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 133       if (__nss_have_localdomain > 0)
 134         {
 135           __nss_not_use_nscd_hosts = 1;
 136           return -1;
 137         }
 138     }
 139
 140   int gc_cycle;
 141   int nretries = 0;
 142
 143   /* If the mapping is available, try to search there instead of
 144      communicating with the nscd.  */
 145   struct mapped_database *mapped;
 146   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 147                                &gc_cycle);
 148
 149  retry:;
 150   const char *h_name = NULL;
 151   const uint32_t *aliases_len = NULL;
 152   const char *addr_list = NULL;
 153   size_t addr_list_len = 0;
 154   int retval = -1;
 155   const char *recend = (const char *) ~UINTMAX_C (0);
 156   int sock = -1;
 157   hst_response_header hst_resp;
 158   if (mapped != NO_MAPPING)
 159     {
 160       /* No const qualifier, as it can change during garbage collection.  */
 161       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 162                                                     sizeof hst_resp);
 163       if (found != NULL)
 164         {
 165           h_name = (char *) (&found->data[0].hstdata + 1);
 166           hst_resp = found->data[0].hstdata;
 167           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 168           addr_list = ((char *) aliases_len
 169                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 170           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 171           recend = (const char *) found->data + found->recsize;
 172           /* Now check if we can trust hst_resp fields.  If GC is
 173              in progress, it can contain anything.  */
 174           if (mapped->head->gc_cycle != gc_cycle)
 175             {
 176               retval = -2;
 177               goto out;
 178             }
 179
 180 #ifndef _STRING_ARCH_unaligned
 181           /* The aliases_len array in the mapped database might very
 182              well be unaligned.  We will access it word-wise so on
 183              platforms which do not tolerate unaligned accesses we
 184              need to make an aligned copy.  */
 185           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 186               != 0)
 187             {
 188               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 189                                       * sizeof (uint32_t));
 190               aliases_len = memcpy (tmp, aliases_len,
 191                                     hst_resp.h_aliases_cnt
 192                                     * sizeof (uint32_t));
 193             }
 194 #endif
 195           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 196             {
 197               if (hst_resp.h_length == INADDRSZ)
 198                 addr_list += addr_list_len;
 199               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 200             }
 201           if (__builtin_expect ((const char *) addr_list + addr_list_len
 202                                 > recend, 0))
 203             goto out;
 204         }
 205     }
 206
 207   if (h_name == NULL)
 208     {
 209       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 210                                  sizeof (hst_resp));
 211       if (sock == -1)
 212         {
 213           __nss_not_use_nscd_hosts = 1;
 214           goto out;
 215         }
 216     }
 217
 218   /* No value found so far.  */
 219   *result = NULL;
 220
 221   if (__builtin_expect (hst_resp.found == -1, 0))
 222     {
 223       /* The daemon does not cache this database.  */
 224       __nss_not_use_nscd_hosts = 1;
 225       goto out_close;
 226     }
 227
 228   if (hst_resp.found == 1)
 229     {
 230       char *cp = buffer;
 231       uintptr_t align1;
 232       uintptr_t align2;
 233       size_t total_len;
 234       ssize_t cnt;
 235       char *ignore;
 236       int n;
 237
 238       /* A first check whether the buffer is sufficiently large is possible.  */
 239       /* Now allocate the buffer the array for the group members.  We must
 240          align the pointer and the base of the h_addr_list pointers.  */
 241       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 242                 & (__alignof__ (char *) - 1));
 243       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 244                                          - ((char *) 0)))
 245                 & (__alignof__ (char *) - 1));
 246       if (buflen < (align1 + hst_resp.h_name_len + align2
 247                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 248                         + 2)
 249                        * sizeof (char *))
 250                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 251                                                   ? INADDRSZ : IN6ADDRSZ)))
 252         {
 253         no_room:
 254           *h_errnop = NETDB_INTERNAL;
 255           __set_errno (ERANGE);
 256           retval = ERANGE;
 257           goto out_close;
 258         }
 259       cp += align1;
 260
 261       /* Prepare the result as far as we can.  */
 262       resultbuf->h_aliases = (char **) cp;
 263       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 264       resultbuf->h_addr_list = (char **) cp;
 265       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 266
 267       resultbuf->h_name = cp;
 268       cp += hst_resp.h_name_len + align2;
 269
 270       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 271         {
 272           resultbuf->h_addrtype = AF_INET;
 273           resultbuf->h_length = INADDRSZ;
 274         }
 275       else
 276         {
 277           resultbuf->h_addrtype = AF_INET6;
 278           resultbuf->h_length = IN6ADDRSZ;
 279         }
 280       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 281         {
 282           resultbuf->h_addr_list[cnt] = cp;
 283           cp += resultbuf->h_length;
 284         }
 285       resultbuf->h_addr_list[cnt] = NULL;
 286
 287       if (h_name == NULL)
 288         {
 289           struct iovec vec[4];
 290
 291           vec[0].iov_base = resultbuf->h_name;
 292           vec[0].iov_len = hst_resp.h_name_len;
 293           total_len = hst_resp.h_name_len;
 294           n = 1;
 295
 296           if (hst_resp.h_aliases_cnt > 0)
 297             {
 298               aliases_len = alloca (hst_resp.h_aliases_cnt
 299                                     * sizeof (uint32_t));
 300               vec[n].iov_base = (void *) aliases_len;
 301               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 302
 303               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 304               ++n;
 305             }
 306
 307           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 308             {
 309               vec[n].iov_base = resultbuf->h_addr_list[0];
 310               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 311
 312               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 313
 314               ++n;
 315             }
 316           else
 317             {
 318               if (hst_resp.h_length == INADDRSZ)
 319                 {
 320                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 321                   vec[n].iov_base = ignore;
 322                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 323
 324                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 325
 326                   ++n;
 327                 }
 328
 329               vec[n].iov_base = resultbuf->h_addr_list[0];
 330               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 331
 332               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 333
 334               ++n;
 335             }
 336
 337           if ((size_t) __readvall (sock, vec, n) != total_len)
 338             goto out_close;
 339         }
 340       else
 341         {
 342           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 343           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 344         }
 345
 346       /*  Now we also can read the aliases.  */
 347       total_len = 0;
 348       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 349         {
 350           resultbuf->h_aliases[cnt] = cp;
 351           cp += aliases_len[cnt];
 352           total_len += aliases_len[cnt];
 353         }
 354       resultbuf->h_aliases[cnt] = NULL;
 355
 356       if (__builtin_expect ((const char *) addr_list + addr_list_len
 357                             + total_len > recend, 0))
 358         {
 359           /* aliases_len array might contain garbage during nscd GC cycle,
 360              retry rather than fail in that case.  */
 361           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 362             retval = -2;
 363           goto out_close;
 364         }
 365       /* See whether this would exceed the buffer capacity.  */
 366       if (__builtin_expect (cp > buffer + buflen, 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             {
 372               retval = -2;
 373               goto out_close;
 374             }
 375           goto no_room;
 376         }
 377
 378       /* And finally read the aliases.  */
 379       if (addr_list == NULL)
 380         {
 381           if (total_len == 0
 382               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 383                   == total_len))
 384             {
 385               retval = 0;
 386               *result = resultbuf;
 387             }
 388         }
 389       else
 390         {
 391           memcpy (resultbuf->h_aliases[0],
 392                   (const char *) addr_list + addr_list_len, total_len);
 393
 394           /* Try to detect corrupt databases.  */
 395           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 396               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 397                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 398                          != '\0')
 399                        break;
 400                    cnt < hst_resp.h_aliases_cnt; }))
 401             {
 402               /* We cannot use the database.  */
 403               if (mapped->head->gc_cycle != gc_cycle)
 404                 retval = -2;
 405               goto out_close;
 406             }
 407
 408           retval = 0;
 409           *result = resultbuf;
 410         }
 411     }
 412   else
 413     {
 414       /* Store the error number.  */
 415       *h_errnop = hst_resp.error;
 416
 417       /* Set errno to 0 to indicate no error, just no found record.  */
 418       __set_errno (0);
 419       /* Even though we have not found anything, the result is zero.  */
 420       retval = 0;
 421     }
 422
 423  out_close:
 424   if (sock != -1)
 425     close_not_cancel_no_status (sock);
 426  out:
 427   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 428     {
 429       /* When we come here this means there has been a GC cycle while we
 430          were looking for the data.  This means the data might have been
 431          inconsistent.  Retry if possible.  */
 432       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 433         {
 434           /* nscd is just running gc now.  Disable using the mapping.  */
 435           if (atomic_decrement_val (&mapped->counter) == 0)
 436             __nscd_unmap (mapped);
 437           mapped = NO_MAPPING;
 438         }
 439
 440       if (retval != -1)
 441         goto retry;
 442     }
 443
 444   return retval;
 445 }