nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <resolv/resolv-internal.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <stdint.h>
  23 #include <arpa/nameser.h>
  24 #include <not-cancel.h>
  25
  26 #include "nscd-client.h"
  27 #include "nscd_proto.h"
  28
  29 int __nss_not_use_nscd_hosts;
  30
  31 static int nscd_gethst_r (const char *key, size_t keylen, request_type type,
  32                           struct hostent *resultbuf, char *buffer,
  33                           size_t buflen, struct hostent **result,
  34                           int *h_errnop);
  35
  36
  37 int
  38 __nscd_gethostbyname_r (const char *name, struct hostent *resultbuf,
  39                         char *buffer, size_t buflen, struct hostent **result,
  40                         int *h_errnop)
  41 {
  42   return nscd_gethst_r (name, strlen (name) + 1, GETHOSTBYNAME, resultbuf,
  43                         buffer, buflen, result, h_errnop);
  44 }
  45
  46
  47 int
  48 __nscd_gethostbyname2_r (const char *name, int af, struct hostent *resultbuf,
  49                          char *buffer, size_t buflen, struct hostent **result,
  50                          int *h_errnop)
  51 {
  52   request_type reqtype;
  53
  54   reqtype = af == AF_INET6 ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  55
  56   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  57                         buffer, buflen, result, h_errnop);
  58 }
  59
  60
  61 int
  62 __nscd_gethostbyaddr_r (const void *addr, socklen_t len, int type,
  63                         struct hostent *resultbuf, char *buffer, size_t buflen,
  64                         struct hostent **result, int *h_errnop)
  65 {
  66   request_type reqtype;
  67
  68   if (!((len == INADDRSZ && type == AF_INET)
  69         || (len == IN6ADDRSZ && type == AF_INET6)))
  70     /* LEN and TYPE do not match.  */
  71     return -1;
  72
  73   reqtype = type == AF_INET6 ? GETHOSTBYADDRv6 : GETHOSTBYADDR;
  74
  75   return nscd_gethst_r (addr, len, reqtype, resultbuf, buffer, buflen, result,
  76                         h_errnop);
  77 }
  78
  79
  80 libc_locked_map_ptr (, __hst_map_handle) attribute_hidden;
  81 /* Note that we only free the structure if necessary.  The memory
  82    mapping is not removed since it is not visible to the malloc
  83    handling.  */
  84 libc_freeres_fn (hst_map_free)
  85 {
  86   if (__hst_map_handle.mapped != NO_MAPPING)
  87     {
  88       void *p = __hst_map_handle.mapped;
  89       __hst_map_handle.mapped = NO_MAPPING;
  90       free (p);
  91     }
  92 }
  93
  94
  95 uint32_t
  96 __nscd_get_nl_timestamp (void)
  97 {
  98   uint32_t retval;
  99   if (__nss_not_use_nscd_hosts != 0)
 100     return 0;
 101
 102   /* __nscd_get_mapping can change hst_map_handle.mapped to NO_MAPPING.
 103    However, __nscd_get_mapping assumes the prior value was not NO_MAPPING.
 104    Thus we have to acquire the lock to prevent this thread from changing
 105    hst_map_handle.mapped to NO_MAPPING while another thread is inside
 106     __nscd_get_mapping.  */
 107   if (!__nscd_acquire_maplock (&__hst_map_handle))
 108     return 0;
 109
 110   struct mapped_database *map = __hst_map_handle.mapped;
 111
 112   if (map == NULL
 113       || (map != NO_MAPPING
 114           && map->head->nscd_certainly_running == 0
 115           && map->head->timestamp + MAPPING_TIMEOUT < time64_now ()))
 116     map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
 117
 118   if (map == NO_MAPPING)
 119     retval = 0;
 120   else
 121     retval = map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
 122
 123   /* Release the lock.  */
 124   __hst_map_handle.lock = 0;
 125
 126   return retval;
 127 }
 128
 129
 130 int __nss_have_localdomain attribute_hidden;
 131
 132 static int
 133 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 134                struct hostent *resultbuf, char *buffer, size_t buflen,
 135                struct hostent **result, int *h_errnop)
 136 {
 137   if (__glibc_unlikely (__nss_have_localdomain >= 0))
 138     {
 139       if (__nss_have_localdomain == 0)
 140         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 141       if (__nss_have_localdomain > 0)
 142         {
 143           __nss_not_use_nscd_hosts = 1;
 144           return -1;
 145         }
 146     }
 147
 148   int gc_cycle;
 149   int nretries = 0;
 150
 151   /* If the mapping is available, try to search there instead of
 152      communicating with the nscd.  */
 153   struct mapped_database *mapped;
 154   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 155                                &gc_cycle);
 156
 157  retry:;
 158   const char *h_name = NULL;
 159   const uint32_t *aliases_len = NULL;
 160   const char *addr_list = NULL;
 161   size_t addr_list_len = 0;
 162   int retval = -1;
 163   const char *recend = (const char *) ~UINTMAX_C (0);
 164   int sock = -1;
 165   hst_response_header hst_resp;
 166   if (mapped != NO_MAPPING)
 167     {
 168       /* No const qualifier, as it can change during garbage collection.  */
 169       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 170                                                     sizeof hst_resp);
 171       if (found != NULL)
 172         {
 173           h_name = (char *) (&found->data[0].hstdata + 1);
 174           hst_resp = found->data[0].hstdata;
 175           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 176           addr_list = ((char *) aliases_len
 177                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 178           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 179           recend = (const char *) found->data + found->recsize;
 180           /* Now check if we can trust hst_resp fields.  If GC is
 181              in progress, it can contain anything.  */
 182           if (mapped->head->gc_cycle != gc_cycle)
 183             {
 184               retval = -2;
 185               goto out;
 186             }
 187
 188 #if !_STRING_ARCH_unaligned
 189           /* The aliases_len array in the mapped database might very
 190              well be unaligned.  We will access it word-wise so on
 191              platforms which do not tolerate unaligned accesses we
 192              need to make an aligned copy.  */
 193           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 194               != 0)
 195             {
 196               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 197                                       * sizeof (uint32_t));
 198               aliases_len = memcpy (tmp, aliases_len,
 199                                     hst_resp.h_aliases_cnt
 200                                     * sizeof (uint32_t));
 201             }
 202 #endif
 203           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 204             {
 205               if (hst_resp.h_length == INADDRSZ)
 206                 addr_list += addr_list_len;
 207               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 208             }
 209           if (__builtin_expect ((const char *) addr_list + addr_list_len
 210                                 > recend, 0))
 211             goto out;
 212         }
 213     }
 214
 215   if (h_name == NULL)
 216     {
 217       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 218                                  sizeof (hst_resp));
 219       if (sock == -1)
 220         {
 221           __nss_not_use_nscd_hosts = 1;
 222           goto out;
 223         }
 224     }
 225
 226   /* No value found so far.  */
 227   *result = NULL;
 228
 229   if (__glibc_unlikely (hst_resp.found == -1))
 230     {
 231       /* The daemon does not cache this database.  */
 232       __nss_not_use_nscd_hosts = 1;
 233       goto out_close;
 234     }
 235
 236   if (hst_resp.found == 1)
 237     {
 238       char *cp = buffer;
 239       uintptr_t align1;
 240       uintptr_t align2;
 241       size_t total_len;
 242       ssize_t cnt;
 243       char *ignore;
 244       int n;
 245
 246       /* A first check whether the buffer is sufficiently large is possible.  */
 247       /* Now allocate the buffer the array for the group members.  We must
 248          align the pointer and the base of the h_addr_list pointers.  */
 249       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 250                 & (__alignof__ (char *) - 1));
 251       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 252                                          - ((char *) 0)))
 253                 & (__alignof__ (char *) - 1));
 254       if (buflen < (align1 + hst_resp.h_name_len + align2
 255                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 256                         + 2)
 257                        * sizeof (char *))
 258                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 259                                                   ? INADDRSZ : IN6ADDRSZ)))
 260         {
 261         no_room:
 262           *h_errnop = NETDB_INTERNAL;
 263           __set_errno (ERANGE);
 264           retval = ERANGE;
 265           goto out_close;
 266         }
 267       cp += align1;
 268
 269       /* Prepare the result as far as we can.  */
 270       resultbuf->h_aliases = (char **) cp;
 271       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 272       resultbuf->h_addr_list = (char **) cp;
 273       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 274
 275       resultbuf->h_name = cp;
 276       cp += hst_resp.h_name_len + align2;
 277
 278       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 279         {
 280           resultbuf->h_addrtype = AF_INET;
 281           resultbuf->h_length = INADDRSZ;
 282         }
 283       else
 284         {
 285           resultbuf->h_addrtype = AF_INET6;
 286           resultbuf->h_length = IN6ADDRSZ;
 287         }
 288       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 289         {
 290           resultbuf->h_addr_list[cnt] = cp;
 291           cp += resultbuf->h_length;
 292         }
 293       resultbuf->h_addr_list[cnt] = NULL;
 294
 295       if (h_name == NULL)
 296         {
 297           struct iovec vec[4];
 298
 299           vec[0].iov_base = resultbuf->h_name;
 300           vec[0].iov_len = hst_resp.h_name_len;
 301           total_len = hst_resp.h_name_len;
 302           n = 1;
 303
 304           if (hst_resp.h_aliases_cnt > 0)
 305             {
 306               aliases_len = alloca (hst_resp.h_aliases_cnt
 307                                     * sizeof (uint32_t));
 308               vec[n].iov_base = (void *) aliases_len;
 309               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 310
 311               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 312               ++n;
 313             }
 314
 315           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 316             {
 317               vec[n].iov_base = resultbuf->h_addr_list[0];
 318               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 319
 320               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 321
 322               ++n;
 323             }
 324           else
 325             {
 326               if (hst_resp.h_length == INADDRSZ)
 327                 {
 328                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 329                   vec[n].iov_base = ignore;
 330                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 331
 332                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 333
 334                   ++n;
 335                 }
 336
 337               vec[n].iov_base = resultbuf->h_addr_list[0];
 338               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 339
 340               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 341
 342               ++n;
 343             }
 344
 345           if ((size_t) __readvall (sock, vec, n) != total_len)
 346             goto out_close;
 347         }
 348       else
 349         {
 350           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 351           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 352         }
 353
 354       /*  Now we also can read the aliases.  */
 355       total_len = 0;
 356       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 357         {
 358           resultbuf->h_aliases[cnt] = cp;
 359           cp += aliases_len[cnt];
 360           total_len += aliases_len[cnt];
 361         }
 362       resultbuf->h_aliases[cnt] = NULL;
 363
 364       if (__builtin_expect ((const char *) addr_list + addr_list_len
 365                             + total_len > recend, 0))
 366         {
 367           /* aliases_len array might contain garbage during nscd GC cycle,
 368              retry rather than fail in that case.  */
 369           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 370             retval = -2;
 371           goto out_close;
 372         }
 373       /* See whether this would exceed the buffer capacity.  */
 374       if (__glibc_unlikely (cp > buffer + buflen))
 375         {
 376           /* aliases_len array might contain garbage during nscd GC cycle,
 377              retry rather than fail in that case.  */
 378           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 379             {
 380               retval = -2;
 381               goto out_close;
 382             }
 383           goto no_room;
 384         }
 385
 386       /* And finally read the aliases.  */
 387       if (addr_list == NULL)
 388         {
 389           if (total_len == 0
 390               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 391                   == total_len))
 392             {
 393               retval = 0;
 394               *result = resultbuf;
 395             }
 396         }
 397       else
 398         {
 399           memcpy (resultbuf->h_aliases[0],
 400                   (const char *) addr_list + addr_list_len, total_len);
 401
 402           /* Try to detect corrupt databases.  */
 403           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 404               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 405                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 406                          != '\0')
 407                        break;
 408                    cnt < hst_resp.h_aliases_cnt; }))
 409             {
 410               /* We cannot use the database.  */
 411               if (mapped->head->gc_cycle != gc_cycle)
 412                 retval = -2;
 413               goto out_close;
 414             }
 415
 416           retval = 0;
 417           *result = resultbuf;
 418         }
 419     }
 420   else
 421     {
 422       /* Store the error number.  */
 423       *h_errnop = hst_resp.error;
 424
 425       /* Set errno to 0 to indicate no error, just no found record.  */
 426       __set_errno (0);
 427       /* Even though we have not found anything, the result is zero.  */
 428       retval = 0;
 429     }
 430
 431  out_close:
 432   if (sock != -1)
 433     __close_nocancel_nostatus (sock);
 434  out:
 435   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 436     {
 437       /* When we come here this means there has been a GC cycle while we
 438          were looking for the data.  This means the data might have been
 439          inconsistent.  Retry if possible.  */
 440       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 441         {
 442           /* nscd is just running gc now.  Disable using the mapping.  */
 443           if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
 444             __nscd_unmap (mapped);
 445           mapped = NO_MAPPING;
 446         }
 447
 448       if (retval != -1)
 449         goto retry;
 450     }
 451
 452   return retval;
 453 }