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 <sys/socket.h>
  25 #include <arpa/nameser.h>
  26 #include <not-cancel.h>
  27
  28 #include "nscd-client.h"
  29 #include "nscd_proto.h"
  30
  31 int __nss_not_use_nscd_hosts;
  32
  33 static int nscd_gethst_r (const char *key, size_t keylen, request_type type,
  34                           struct hostent *resultbuf, char *buffer,
  35                           size_t buflen, struct hostent **result,
  36                           int *h_errnop);
  37
  38
  39 int
  40 __nscd_gethostbyname_r (const char *name, struct hostent *resultbuf,
  41                         char *buffer, size_t buflen, struct hostent **result,
  42                         int *h_errnop)
  43 {
  44   return nscd_gethst_r (name, strlen (name) + 1, GETHOSTBYNAME, resultbuf,
  45                         buffer, buflen, result, h_errnop);
  46 }
  47
  48
  49 int
  50 __nscd_gethostbyname2_r (const char *name, int af, struct hostent *resultbuf,
  51                          char *buffer, size_t buflen, struct hostent **result,
  52                          int *h_errnop)
  53 {
  54   request_type reqtype;
  55
  56   reqtype = af == AF_INET6 ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  57
  58   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  59                         buffer, buflen, result, h_errnop);
  60 }
  61
  62
  63 int
  64 __nscd_gethostbyaddr_r (const void *addr, socklen_t len, int type,
  65                         struct hostent *resultbuf, char *buffer, size_t buflen,
  66                         struct hostent **result, int *h_errnop)
  67 {
  68   request_type reqtype;
  69
  70   if (!((len == INADDRSZ && type == AF_INET)
  71         || (len == IN6ADDRSZ && type == AF_INET6)))
  72     /* LEN and TYPE do not match.  */
  73     return -1;
  74
  75   reqtype = type == AF_INET6 ? GETHOSTBYADDRv6 : GETHOSTBYADDR;
  76
  77   return nscd_gethst_r (addr, len, reqtype, resultbuf, buffer, buflen, result,
  78                         h_errnop);
  79 }
  80
  81
  82 libc_locked_map_ptr (, __hst_map_handle) attribute_hidden;
  83 /* Note that we only free the structure if necessary.  The memory
  84    mapping is not removed since it is not visible to the malloc
  85    handling.  */
  86 libc_freeres_fn (hst_map_free)
  87 {
  88   if (__hst_map_handle.mapped != NO_MAPPING)
  89     {
  90       void *p = __hst_map_handle.mapped;
  91       __hst_map_handle.mapped = NO_MAPPING;
  92       free (p);
  93     }
  94 }
  95
  96
  97 uint32_t
  98 __nscd_get_nl_timestamp (void)
  99 {
 100   uint32_t retval;
 101   if (__nss_not_use_nscd_hosts != 0)
 102     return 0;
 103
 104   /* __nscd_get_mapping can change hst_map_handle.mapped to NO_MAPPING.
 105    However, __nscd_get_mapping assumes the prior value was not NO_MAPPING.
 106    Thus we have to acquire the lock to prevent this thread from changing
 107    hst_map_handle.mapped to NO_MAPPING while another thread is inside
 108     __nscd_get_mapping.  */
 109   if (!__nscd_acquire_maplock (&__hst_map_handle))
 110     return 0;
 111
 112   struct mapped_database *map = __hst_map_handle.mapped;
 113
 114   if (map == NULL
 115       || (map != NO_MAPPING
 116           && map->head->nscd_certainly_running == 0
 117           && map->head->timestamp + MAPPING_TIMEOUT < time_now ()))
 118     map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
 119
 120   if (map == NO_MAPPING)
 121     retval = 0;
 122   else
 123     retval = map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
 124
 125   /* Release the lock.  */
 126   __hst_map_handle.lock = 0;
 127
 128   return retval;
 129 }
 130
 131
 132 int __nss_have_localdomain attribute_hidden;
 133
 134 static int
 135 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 136                struct hostent *resultbuf, char *buffer, size_t buflen,
 137                struct hostent **result, int *h_errnop)
 138 {
 139   if (__glibc_unlikely (__nss_have_localdomain >= 0))
 140     {
 141       if (__nss_have_localdomain == 0)
 142         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 143       if (__nss_have_localdomain > 0)
 144         {
 145           __nss_not_use_nscd_hosts = 1;
 146           return -1;
 147         }
 148     }
 149
 150   int gc_cycle;
 151   int nretries = 0;
 152
 153   /* If the mapping is available, try to search there instead of
 154      communicating with the nscd.  */
 155   struct mapped_database *mapped;
 156   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 157                                &gc_cycle);
 158
 159  retry:;
 160   const char *h_name = NULL;
 161   const uint32_t *aliases_len = NULL;
 162   const char *addr_list = NULL;
 163   size_t addr_list_len = 0;
 164   int retval = -1;
 165   const char *recend = (const char *) ~UINTMAX_C (0);
 166   int sock = -1;
 167   hst_response_header hst_resp;
 168   if (mapped != NO_MAPPING)
 169     {
 170       /* No const qualifier, as it can change during garbage collection.  */
 171       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 172                                                     sizeof hst_resp);
 173       if (found != NULL)
 174         {
 175           h_name = (char *) (&found->data[0].hstdata + 1);
 176           hst_resp = found->data[0].hstdata;
 177           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 178           addr_list = ((char *) aliases_len
 179                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 180           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 181           recend = (const char *) found->data + found->recsize;
 182           /* Now check if we can trust hst_resp fields.  If GC is
 183              in progress, it can contain anything.  */
 184           if (mapped->head->gc_cycle != gc_cycle)
 185             {
 186               retval = -2;
 187               goto out;
 188             }
 189
 190 #if !_STRING_ARCH_unaligned
 191           /* The aliases_len array in the mapped database might very
 192              well be unaligned.  We will access it word-wise so on
 193              platforms which do not tolerate unaligned accesses we
 194              need to make an aligned copy.  */
 195           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 196               != 0)
 197             {
 198               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 199                                       * sizeof (uint32_t));
 200               aliases_len = memcpy (tmp, aliases_len,
 201                                     hst_resp.h_aliases_cnt
 202                                     * sizeof (uint32_t));
 203             }
 204 #endif
 205           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 206             {
 207               if (hst_resp.h_length == INADDRSZ)
 208                 addr_list += addr_list_len;
 209               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 210             }
 211           if (__builtin_expect ((const char *) addr_list + addr_list_len
 212                                 > recend, 0))
 213             goto out;
 214         }
 215     }
 216
 217   if (h_name == NULL)
 218     {
 219       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 220                                  sizeof (hst_resp));
 221       if (sock == -1)
 222         {
 223           __nss_not_use_nscd_hosts = 1;
 224           goto out;
 225         }
 226     }
 227
 228   /* No value found so far.  */
 229   *result = NULL;
 230
 231   if (__glibc_unlikely (hst_resp.found == -1))
 232     {
 233       /* The daemon does not cache this database.  */
 234       __nss_not_use_nscd_hosts = 1;
 235       goto out_close;
 236     }
 237
 238   if (hst_resp.found == 1)
 239     {
 240       char *cp = buffer;
 241       uintptr_t align1;
 242       uintptr_t align2;
 243       size_t total_len;
 244       ssize_t cnt;
 245       char *ignore;
 246       int n;
 247
 248       /* A first check whether the buffer is sufficiently large is possible.  */
 249       /* Now allocate the buffer the array for the group members.  We must
 250          align the pointer and the base of the h_addr_list pointers.  */
 251       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 252                 & (__alignof__ (char *) - 1));
 253       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 254                                          - ((char *) 0)))
 255                 & (__alignof__ (char *) - 1));
 256       if (buflen < (align1 + hst_resp.h_name_len + align2
 257                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 258                         + 2)
 259                        * sizeof (char *))
 260                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 261                                                   ? INADDRSZ : IN6ADDRSZ)))
 262         {
 263         no_room:
 264           *h_errnop = NETDB_INTERNAL;
 265           __set_errno (ERANGE);
 266           retval = ERANGE;
 267           goto out_close;
 268         }
 269       cp += align1;
 270
 271       /* Prepare the result as far as we can.  */
 272       resultbuf->h_aliases = (char **) cp;
 273       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 274       resultbuf->h_addr_list = (char **) cp;
 275       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 276
 277       resultbuf->h_name = cp;
 278       cp += hst_resp.h_name_len + align2;
 279
 280       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 281         {
 282           resultbuf->h_addrtype = AF_INET;
 283           resultbuf->h_length = INADDRSZ;
 284         }
 285       else
 286         {
 287           resultbuf->h_addrtype = AF_INET6;
 288           resultbuf->h_length = IN6ADDRSZ;
 289         }
 290       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 291         {
 292           resultbuf->h_addr_list[cnt] = cp;
 293           cp += resultbuf->h_length;
 294         }
 295       resultbuf->h_addr_list[cnt] = NULL;
 296
 297       if (h_name == NULL)
 298         {
 299           struct iovec vec[4];
 300
 301           vec[0].iov_base = resultbuf->h_name;
 302           vec[0].iov_len = hst_resp.h_name_len;
 303           total_len = hst_resp.h_name_len;
 304           n = 1;
 305
 306           if (hst_resp.h_aliases_cnt > 0)
 307             {
 308               aliases_len = alloca (hst_resp.h_aliases_cnt
 309                                     * sizeof (uint32_t));
 310               vec[n].iov_base = (void *) aliases_len;
 311               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 312
 313               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 314               ++n;
 315             }
 316
 317           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 318             {
 319               vec[n].iov_base = resultbuf->h_addr_list[0];
 320               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 321
 322               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 323
 324               ++n;
 325             }
 326           else
 327             {
 328               if (hst_resp.h_length == INADDRSZ)
 329                 {
 330                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 331                   vec[n].iov_base = ignore;
 332                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 333
 334                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 335
 336                   ++n;
 337                 }
 338
 339               vec[n].iov_base = resultbuf->h_addr_list[0];
 340               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 341
 342               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 343
 344               ++n;
 345             }
 346
 347           if ((size_t) __readvall (sock, vec, n) != total_len)
 348             goto out_close;
 349         }
 350       else
 351         {
 352           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 353           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 354         }
 355
 356       /*  Now we also can read the aliases.  */
 357       total_len = 0;
 358       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 359         {
 360           resultbuf->h_aliases[cnt] = cp;
 361           cp += aliases_len[cnt];
 362           total_len += aliases_len[cnt];
 363         }
 364       resultbuf->h_aliases[cnt] = NULL;
 365
 366       if (__builtin_expect ((const char *) addr_list + addr_list_len
 367                             + total_len > recend, 0))
 368         {
 369           /* aliases_len array might contain garbage during nscd GC cycle,
 370              retry rather than fail in that case.  */
 371           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 372             retval = -2;
 373           goto out_close;
 374         }
 375       /* See whether this would exceed the buffer capacity.  */
 376       if (__glibc_unlikely (cp > buffer + buflen))
 377         {
 378           /* aliases_len array might contain garbage during nscd GC cycle,
 379              retry rather than fail in that case.  */
 380           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 381             {
 382               retval = -2;
 383               goto out_close;
 384             }
 385           goto no_room;
 386         }
 387
 388       /* And finally read the aliases.  */
 389       if (addr_list == NULL)
 390         {
 391           if (total_len == 0
 392               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 393                   == total_len))
 394             {
 395               retval = 0;
 396               *result = resultbuf;
 397             }
 398         }
 399       else
 400         {
 401           memcpy (resultbuf->h_aliases[0],
 402                   (const char *) addr_list + addr_list_len, total_len);
 403
 404           /* Try to detect corrupt databases.  */
 405           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 406               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 407                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 408                          != '\0')
 409                        break;
 410                    cnt < hst_resp.h_aliases_cnt; }))
 411             {
 412               /* We cannot use the database.  */
 413               if (mapped->head->gc_cycle != gc_cycle)
 414                 retval = -2;
 415               goto out_close;
 416             }
 417
 418           retval = 0;
 419           *result = resultbuf;
 420         }
 421     }
 422   else
 423     {
 424       /* Store the error number.  */
 425       *h_errnop = hst_resp.error;
 426
 427       /* Set errno to 0 to indicate no error, just no found record.  */
 428       __set_errno (0);
 429       /* Even though we have not found anything, the result is zero.  */
 430       retval = 0;
 431     }
 432
 433  out_close:
 434   if (sock != -1)
 435     __close_nocancel_nostatus (sock);
 436  out:
 437   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 438     {
 439       /* When we come here this means there has been a GC cycle while we
 440          were looking for the data.  This means the data might have been
 441          inconsistent.  Retry if possible.  */
 442       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 443         {
 444           /* nscd is just running gc now.  Disable using the mapping.  */
 445           if (atomic_decrement_val (&mapped->counter) == 0)
 446             __nscd_unmap (mapped);
 447           mapped = NO_MAPPING;
 448         }
 449
 450       if (retval != -1)
 451         goto retry;
 452     }
 453
 454   return retval;
 455 }