nscd/nscd_getserv_r.c

   1 /* Copyright (C) 2007-2024 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 <assert.h>
  19 #include <errno.h>
  20 #include <string.h>
  21 #include <not-cancel.h>
  22 #include <_itoa.h>
  23 #include <stdint.h>
  24
  25 #include "nscd-client.h"
  26 #include "nscd_proto.h"
  27
  28
  29 int __nss_not_use_nscd_services;
  30
  31
  32 static int nscd_getserv_r (const char *crit, size_t critlen, const char *proto,
  33                            request_type type, struct servent *resultbuf,
  34                            char *buf, size_t buflen, struct servent **result);
  35
  36
  37 int
  38 __nscd_getservbyname_r (const char *name, const char *proto,
  39                         struct servent *result_buf, char *buf, size_t buflen,
  40                         struct servent **result)
  41 {
  42   return nscd_getserv_r (name, strlen (name), proto, GETSERVBYNAME, result_buf,
  43                          buf, buflen, result);
  44 }
  45
  46
  47 int
  48 __nscd_getservbyport_r (int port, const char *proto,
  49                         struct servent *result_buf, char *buf, size_t buflen,
  50                         struct servent **result)
  51 {
  52   char portstr[3 * sizeof (int) + 2];
  53   portstr[sizeof (portstr) - 1] = '\0';
  54   char *cp = _itoa_word (port, portstr + sizeof (portstr) - 1, 10, 0);
  55
  56   return nscd_getserv_r (cp, portstr + sizeof (portstr) - 1 - cp, proto,
  57                          GETSERVBYPORT, result_buf, buf, buflen, result);
  58 }
  59
  60
  61 libc_locked_map_ptr (, __serv_map_handle) attribute_hidden;
  62 /* Note that we only free the structure if necessary.  The memory
  63    mapping is not removed since it is not visible to the malloc
  64    handling.  */
  65 void
  66 __nscd_serv_map_freemem (void)
  67 {
  68   if (__serv_map_handle.mapped != NO_MAPPING)
  69     {
  70       void *p = __serv_map_handle.mapped;
  71       __serv_map_handle.mapped = NO_MAPPING;
  72       free (p);
  73     }
  74 }
  75
  76
  77 static int
  78 nscd_getserv_r (const char *crit, size_t critlen, const char *proto,
  79                 request_type type, struct servent *resultbuf,
  80                 char *buf, size_t buflen, struct servent **result)
  81 {
  82   int gc_cycle;
  83   int nretries = 0;
  84   size_t alloca_used = 0;
  85
  86   /* If the mapping is available, try to search there instead of
  87      communicating with the nscd.  */
  88   struct mapped_database *mapped;
  89   mapped = __nscd_get_map_ref (GETFDSERV, "services", &__serv_map_handle,
  90                                &gc_cycle);
  91   size_t protolen = proto == NULL ? 0 : strlen (proto);
  92   size_t keylen = critlen + 1 + protolen + 1;
  93   int alloca_key = __libc_use_alloca (keylen);
  94   char *key;
  95   if (alloca_key)
  96     key = alloca_account (keylen, alloca_used);
  97   else
  98     {
  99       key = malloc (keylen);
 100       if (key == NULL)
 101         return -1;
 102     }
 103   memcpy (__mempcpy (__mempcpy (key, crit, critlen),
 104                      "/", 1), proto ?: "", protolen + 1);
 105
 106  retry:;
 107   const char *s_name = NULL;
 108   const char *s_proto = NULL;
 109   int alloca_aliases_len = 0;
 110   const uint32_t *aliases_len = NULL;
 111   const char *aliases_list = NULL;
 112   int retval = -1;
 113   const char *recend = (const char *) ~UINTMAX_C (0);
 114   int sock = -1;
 115   serv_response_header serv_resp;
 116
 117   if (mapped != NO_MAPPING)
 118     {
 119       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 120                                                     sizeof serv_resp);
 121
 122       if (found != NULL)
 123         {
 124           s_name = (char *) (&found->data[0].servdata + 1);
 125           serv_resp = found->data[0].servdata;
 126           s_proto = s_name + serv_resp.s_name_len;
 127           alloca_aliases_len = 1;
 128           aliases_len = (uint32_t *) (s_proto + serv_resp.s_proto_len);
 129           aliases_list = ((char *) aliases_len
 130                           + serv_resp.s_aliases_cnt * sizeof (uint32_t));
 131           recend = (const char *) found->data + found->recsize;
 132           /* Now check if we can trust serv_resp fields.  If GC is
 133              in progress, it can contain anything.  */
 134           if (mapped->head->gc_cycle != gc_cycle)
 135             {
 136               retval = -2;
 137               goto out;
 138             }
 139           if (__builtin_expect ((const char *) aliases_len
 140                                 + serv_resp.s_aliases_cnt * sizeof (uint32_t)
 141                                 > recend, 0))
 142             goto out;
 143
 144           /* The aliases_len array in the mapped database might very
 145              well be unaligned.  We will access it word-wise so on
 146              platforms which do not tolerate unaligned accesses we
 147              need to make an aligned copy.  */
 148           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 149               != 0)
 150             {
 151               uint32_t *tmp;
 152               alloca_aliases_len
 153                 = __libc_use_alloca (alloca_used
 154                                      + (serv_resp.s_aliases_cnt
 155                                         * sizeof (uint32_t)));
 156               if (alloca_aliases_len)
 157                 tmp = alloca_account (serv_resp.s_aliases_cnt
 158                                       * sizeof (uint32_t),
 159                                       alloca_used);
 160               else
 161                 {
 162                   tmp = malloc (serv_resp.s_aliases_cnt * sizeof (uint32_t));
 163                   if (tmp == NULL)
 164                     {
 165                       retval = ENOMEM;
 166                       goto out;
 167                     }
 168                 }
 169               aliases_len = memcpy (tmp, aliases_len,
 170                                     serv_resp.s_aliases_cnt
 171                                     * sizeof (uint32_t));
 172             }
 173         }
 174     }
 175
 176   if (s_name == NULL)
 177     {
 178       sock = __nscd_open_socket (key, keylen, type, &serv_resp,
 179                                  sizeof (serv_resp));
 180       if (sock == -1)
 181         {
 182           __nss_not_use_nscd_services = 1;
 183           goto out;
 184         }
 185     }
 186
 187   /* No value found so far.  */
 188   *result = NULL;
 189
 190   if (__glibc_unlikely (serv_resp.found == -1))
 191     {
 192       /* The daemon does not cache this database.  */
 193       __nss_not_use_nscd_services = 1;
 194       goto out_close;
 195     }
 196
 197   if (serv_resp.found == 1)
 198     {
 199       char *cp = buf;
 200       uintptr_t align1;
 201       uintptr_t align2;
 202       size_t total_len;
 203       ssize_t cnt;
 204       int n;
 205
 206       /* A first check whether the buffer is sufficiently large is possible.  */
 207       /* Now allocate the buffer the array for the group members.  We must
 208          align the pointer and the base of the h_addr_list pointers.  */
 209       align1 = ((__alignof__ (char *) - ((uintptr_t) cp))
 210                 & (__alignof__ (char *) - 1));
 211       align2 = ((__alignof__ (char *) - ((uintptr_t) (cp + align1 + serv_resp.s_name_len
 212                                           + serv_resp.s_proto_len)))
 213                 & (__alignof__ (char *) - 1));
 214       if (buflen < (align1 + serv_resp.s_name_len + serv_resp.s_proto_len
 215                     + align2
 216                     + (serv_resp.s_aliases_cnt + 1) * sizeof (char *)))
 217         {
 218         no_room:
 219           __set_errno (ERANGE);
 220           retval = ERANGE;
 221           goto out_close;
 222         }
 223       cp += align1;
 224
 225       /* Prepare the result as far as we can.  */
 226       resultbuf->s_aliases = (char **) cp;
 227       cp += (serv_resp.s_aliases_cnt + 1) * sizeof (char *);
 228
 229       resultbuf->s_name = cp;
 230       cp += serv_resp.s_name_len;
 231       resultbuf->s_proto = cp;
 232       cp += serv_resp.s_proto_len + align2;
 233       resultbuf->s_port = serv_resp.s_port;
 234
 235       if (s_name == NULL)
 236         {
 237           struct iovec vec[2];
 238
 239           vec[0].iov_base = resultbuf->s_name;
 240           vec[0].iov_len = serv_resp.s_name_len + serv_resp.s_proto_len;
 241           total_len = vec[0].iov_len;
 242           n = 1;
 243
 244           if (serv_resp.s_aliases_cnt > 0)
 245             {
 246               assert (alloca_aliases_len == 0);
 247               alloca_aliases_len
 248                 = __libc_use_alloca (alloca_used
 249                                      + (serv_resp.s_aliases_cnt
 250                                         * sizeof (uint32_t)));
 251               if (alloca_aliases_len)
 252                 aliases_len = alloca_account (serv_resp.s_aliases_cnt
 253                                               * sizeof (uint32_t),
 254                                               alloca_used);
 255               else
 256                 {
 257                   aliases_len = malloc (serv_resp.s_aliases_cnt
 258                                         * sizeof (uint32_t));
 259                   if (aliases_len == NULL)
 260                     {
 261                       retval = ENOMEM;
 262                       goto out_close;
 263                     }
 264                 }
 265               vec[n].iov_base = (void *) aliases_len;
 266               vec[n].iov_len = serv_resp.s_aliases_cnt * sizeof (uint32_t);
 267
 268               total_len += serv_resp.s_aliases_cnt * sizeof (uint32_t);
 269               ++n;
 270             }
 271
 272           if ((size_t) __readvall (sock, vec, n) != total_len)
 273             goto out_close;
 274         }
 275       else
 276         memcpy (resultbuf->s_name, s_name,
 277                 serv_resp.s_name_len + serv_resp.s_proto_len);
 278
 279       /*  Now we also can read the aliases.  */
 280       total_len = 0;
 281       for (cnt = 0; cnt < serv_resp.s_aliases_cnt; ++cnt)
 282         {
 283           resultbuf->s_aliases[cnt] = cp;
 284           cp += aliases_len[cnt];
 285           total_len += aliases_len[cnt];
 286         }
 287       resultbuf->s_aliases[cnt] = NULL;
 288
 289       if (__builtin_expect ((const char *) aliases_list + total_len > recend,
 290                             0))
 291         {
 292           /* aliases_len array might contain garbage during nscd GC cycle,
 293              retry rather than fail in that case.  */
 294           if (aliases_list != NULL && mapped->head->gc_cycle != gc_cycle)
 295             retval = -2;
 296           goto out_close;
 297         }
 298
 299       /* See whether this would exceed the buffer capacity.  */
 300       if (__glibc_unlikely (cp > buf + buflen))
 301         {
 302           /* aliases_len array might contain garbage during nscd GC cycle,
 303              retry rather than fail in that case.  */
 304           if (aliases_list != NULL && mapped->head->gc_cycle != gc_cycle)
 305             {
 306               retval = -2;
 307               goto out_close;
 308             }
 309           goto no_room;
 310         }
 311
 312       /* And finally read the aliases.  */
 313       if (aliases_list == NULL)
 314         {
 315           if (total_len == 0
 316               || ((size_t) __readall (sock, resultbuf->s_aliases[0], total_len)
 317                   == total_len))
 318             {
 319               retval = 0;
 320               *result = resultbuf;
 321             }
 322         }
 323       else
 324         {
 325           memcpy (resultbuf->s_aliases[0], aliases_list, total_len);
 326
 327           /* Try to detect corrupt databases.  */
 328           if (resultbuf->s_name[serv_resp.s_name_len - 1] != '\0'
 329               || resultbuf->s_proto[serv_resp.s_proto_len - 1] != '\0'
 330               || ({for (cnt = 0; cnt < serv_resp.s_aliases_cnt; ++cnt)
 331                      if (resultbuf->s_aliases[cnt][aliases_len[cnt] - 1]
 332                          != '\0')
 333                        break;
 334                    cnt < serv_resp.s_aliases_cnt; }))
 335             {
 336               /* We cannot use the database.  */
 337               if (mapped->head->gc_cycle != gc_cycle)
 338                 retval = -2;
 339               goto out_close;
 340             }
 341
 342           retval = 0;
 343           *result = resultbuf;
 344         }
 345     }
 346   else
 347     {
 348       /* Set errno to 0 to indicate no error, just no found record.  */
 349       __set_errno (0);
 350       /* Even though we have not found anything, the result is zero.  */
 351       retval = 0;
 352     }
 353
 354  out_close:
 355   if (sock != -1)
 356     __close_nocancel_nostatus (sock);
 357  out:
 358   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 359     {
 360       /* When we come here this means there has been a GC cycle while we
 361          were looking for the data.  This means the data might have been
 362          inconsistent.  Retry if possible.  */
 363       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 364         {
 365           /* nscd is just running gc now.  Disable using the mapping.  */
 366           if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
 367             __nscd_unmap (mapped);
 368           mapped = NO_MAPPING;
 369         }
 370
 371       if (retval != -1)
 372         {
 373           if (!alloca_aliases_len)
 374             free ((void *) aliases_len);
 375           goto retry;
 376         }
 377     }
 378
 379   if (!alloca_aliases_len)
 380     free ((void *) aliases_len);
 381   if (!alloca_key)
 382     free (key);
 383
 384   return retval;
 385 }