nscd/nscd_getserv_r.c

   1 /* Copyright (C) 2007-2023 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 <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 libc_freeres_fn (serv_map_free)
  66 {
  67   if (__serv_map_handle.mapped != NO_MAPPING)
  68     {
  69       void *p = __serv_map_handle.mapped;
  70       __serv_map_handle.mapped = NO_MAPPING;
  71       free (p);
  72     }
  73 }
  74
  75
  76 static int
  77 nscd_getserv_r (const char *crit, size_t critlen, const char *proto,
  78                 request_type type, struct servent *resultbuf,
  79                 char *buf, size_t buflen, struct servent **result)
  80 {
  81   int gc_cycle;
  82   int nretries = 0;
  83   size_t alloca_used = 0;
  84
  85   /* If the mapping is available, try to search there instead of
  86      communicating with the nscd.  */
  87   struct mapped_database *mapped;
  88   mapped = __nscd_get_map_ref (GETFDSERV, "services", &__serv_map_handle,
  89                                &gc_cycle);
  90   size_t protolen = proto == NULL ? 0 : strlen (proto);
  91   size_t keylen = critlen + 1 + protolen + 1;
  92   int alloca_key = __libc_use_alloca (keylen);
  93   char *key;
  94   if (alloca_key)
  95     key = alloca_account (keylen, alloca_used);
  96   else
  97     {
  98       key = malloc (keylen);
  99       if (key == NULL)
 100         return -1;
 101     }
 102   memcpy (__mempcpy (__mempcpy (key, crit, critlen),
 103                      "/", 1), proto ?: "", protolen + 1);
 104
 105  retry:;
 106   const char *s_name = NULL;
 107   const char *s_proto = NULL;
 108   int alloca_aliases_len = 0;
 109   const uint32_t *aliases_len = NULL;
 110   const char *aliases_list = NULL;
 111   int retval = -1;
 112   const char *recend = (const char *) ~UINTMAX_C (0);
 113   int sock = -1;
 114   serv_response_header serv_resp;
 115
 116   if (mapped != NO_MAPPING)
 117     {
 118       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 119                                                     sizeof serv_resp);
 120
 121       if (found != NULL)
 122         {
 123           s_name = (char *) (&found->data[0].servdata + 1);
 124           serv_resp = found->data[0].servdata;
 125           s_proto = s_name + serv_resp.s_name_len;
 126           alloca_aliases_len = 1;
 127           aliases_len = (uint32_t *) (s_proto + serv_resp.s_proto_len);
 128           aliases_list = ((char *) aliases_len
 129                           + serv_resp.s_aliases_cnt * sizeof (uint32_t));
 130           recend = (const char *) found->data + found->recsize;
 131           /* Now check if we can trust serv_resp fields.  If GC is
 132              in progress, it can contain anything.  */
 133           if (mapped->head->gc_cycle != gc_cycle)
 134             {
 135               retval = -2;
 136               goto out;
 137             }
 138           if (__builtin_expect ((const char *) aliases_len
 139                                 + serv_resp.s_aliases_cnt * sizeof (uint32_t)
 140                                 > recend, 0))
 141             goto out;
 142
 143           /* The aliases_len array in the mapped database might very
 144              well be unaligned.  We will access it word-wise so on
 145              platforms which do not tolerate unaligned accesses we
 146              need to make an aligned copy.  */
 147           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 148               != 0)
 149             {
 150               uint32_t *tmp;
 151               alloca_aliases_len
 152                 = __libc_use_alloca (alloca_used
 153                                      + (serv_resp.s_aliases_cnt
 154                                         * sizeof (uint32_t)));
 155               if (alloca_aliases_len)
 156                 tmp = alloca_account (serv_resp.s_aliases_cnt
 157                                       * sizeof (uint32_t),
 158                                       alloca_used);
 159               else
 160                 {
 161                   tmp = malloc (serv_resp.s_aliases_cnt * sizeof (uint32_t));
 162                   if (tmp == NULL)
 163                     {
 164                       retval = ENOMEM;
 165                       goto out;
 166                     }
 167                 }
 168               aliases_len = memcpy (tmp, aliases_len,
 169                                     serv_resp.s_aliases_cnt
 170                                     * sizeof (uint32_t));
 171             }
 172         }
 173     }
 174
 175   if (s_name == NULL)
 176     {
 177       sock = __nscd_open_socket (key, keylen, type, &serv_resp,
 178                                  sizeof (serv_resp));
 179       if (sock == -1)
 180         {
 181           __nss_not_use_nscd_services = 1;
 182           goto out;
 183         }
 184     }
 185
 186   /* No value found so far.  */
 187   *result = NULL;
 188
 189   if (__glibc_unlikely (serv_resp.found == -1))
 190     {
 191       /* The daemon does not cache this database.  */
 192       __nss_not_use_nscd_services = 1;
 193       goto out_close;
 194     }
 195
 196   if (serv_resp.found == 1)
 197     {
 198       char *cp = buf;
 199       uintptr_t align1;
 200       uintptr_t align2;
 201       size_t total_len;
 202       ssize_t cnt;
 203       int n;
 204
 205       /* A first check whether the buffer is sufficiently large is possible.  */
 206       /* Now allocate the buffer the array for the group members.  We must
 207          align the pointer and the base of the h_addr_list pointers.  */
 208       align1 = ((__alignof__ (char *) - ((uintptr_t) cp))
 209                 & (__alignof__ (char *) - 1));
 210       align2 = ((__alignof__ (char *) - ((uintptr_t) (cp + align1 + serv_resp.s_name_len
 211                                           + serv_resp.s_proto_len)))
 212                 & (__alignof__ (char *) - 1));
 213       if (buflen < (align1 + serv_resp.s_name_len + serv_resp.s_proto_len
 214                     + align2
 215                     + (serv_resp.s_aliases_cnt + 1) * sizeof (char *)))
 216         {
 217         no_room:
 218           __set_errno (ERANGE);
 219           retval = ERANGE;
 220           goto out_close;
 221         }
 222       cp += align1;
 223
 224       /* Prepare the result as far as we can.  */
 225       resultbuf->s_aliases = (char **) cp;
 226       cp += (serv_resp.s_aliases_cnt + 1) * sizeof (char *);
 227
 228       resultbuf->s_name = cp;
 229       cp += serv_resp.s_name_len;
 230       resultbuf->s_proto = cp;
 231       cp += serv_resp.s_proto_len + align2;
 232       resultbuf->s_port = serv_resp.s_port;
 233
 234       if (s_name == NULL)
 235         {
 236           struct iovec vec[2];
 237
 238           vec[0].iov_base = resultbuf->s_name;
 239           vec[0].iov_len = serv_resp.s_name_len + serv_resp.s_proto_len;
 240           total_len = vec[0].iov_len;
 241           n = 1;
 242
 243           if (serv_resp.s_aliases_cnt > 0)
 244             {
 245               assert (alloca_aliases_len == 0);
 246               alloca_aliases_len
 247                 = __libc_use_alloca (alloca_used
 248                                      + (serv_resp.s_aliases_cnt
 249                                         * sizeof (uint32_t)));
 250               if (alloca_aliases_len)
 251                 aliases_len = alloca_account (serv_resp.s_aliases_cnt
 252                                               * sizeof (uint32_t),
 253                                               alloca_used);
 254               else
 255                 {
 256                   aliases_len = malloc (serv_resp.s_aliases_cnt
 257                                         * sizeof (uint32_t));
 258                   if (aliases_len == NULL)
 259                     {
 260                       retval = ENOMEM;
 261                       goto out_close;
 262                     }
 263                 }
 264               vec[n].iov_base = (void *) aliases_len;
 265               vec[n].iov_len = serv_resp.s_aliases_cnt * sizeof (uint32_t);
 266
 267               total_len += serv_resp.s_aliases_cnt * sizeof (uint32_t);
 268               ++n;
 269             }
 270
 271           if ((size_t) __readvall (sock, vec, n) != total_len)
 272             goto out_close;
 273         }
 274       else
 275         memcpy (resultbuf->s_name, s_name,
 276                 serv_resp.s_name_len + serv_resp.s_proto_len);
 277
 278       /*  Now we also can read the aliases.  */
 279       total_len = 0;
 280       for (cnt = 0; cnt < serv_resp.s_aliases_cnt; ++cnt)
 281         {
 282           resultbuf->s_aliases[cnt] = cp;
 283           cp += aliases_len[cnt];
 284           total_len += aliases_len[cnt];
 285         }
 286       resultbuf->s_aliases[cnt] = NULL;
 287
 288       if (__builtin_expect ((const char *) aliases_list + total_len > recend,
 289                             0))
 290         {
 291           /* aliases_len array might contain garbage during nscd GC cycle,
 292              retry rather than fail in that case.  */
 293           if (aliases_list != NULL && mapped->head->gc_cycle != gc_cycle)
 294             retval = -2;
 295           goto out_close;
 296         }
 297
 298       /* See whether this would exceed the buffer capacity.  */
 299       if (__glibc_unlikely (cp > buf + buflen))
 300         {
 301           /* aliases_len array might contain garbage during nscd GC cycle,
 302              retry rather than fail in that case.  */
 303           if (aliases_list != NULL && mapped->head->gc_cycle != gc_cycle)
 304             {
 305               retval = -2;
 306               goto out_close;
 307             }
 308           goto no_room;
 309         }
 310
 311       /* And finally read the aliases.  */
 312       if (aliases_list == NULL)
 313         {
 314           if (total_len == 0
 315               || ((size_t) __readall (sock, resultbuf->s_aliases[0], total_len)
 316                   == total_len))
 317             {
 318               retval = 0;
 319               *result = resultbuf;
 320             }
 321         }
 322       else
 323         {
 324           memcpy (resultbuf->s_aliases[0], aliases_list, total_len);
 325
 326           /* Try to detect corrupt databases.  */
 327           if (resultbuf->s_name[serv_resp.s_name_len - 1] != '\0'
 328               || resultbuf->s_proto[serv_resp.s_proto_len - 1] != '\0'
 329               || ({for (cnt = 0; cnt < serv_resp.s_aliases_cnt; ++cnt)
 330                      if (resultbuf->s_aliases[cnt][aliases_len[cnt] - 1]
 331                          != '\0')
 332                        break;
 333                    cnt < serv_resp.s_aliases_cnt; }))
 334             {
 335               /* We cannot use the database.  */
 336               if (mapped->head->gc_cycle != gc_cycle)
 337                 retval = -2;
 338               goto out_close;
 339             }
 340
 341           retval = 0;
 342           *result = resultbuf;
 343         }
 344     }
 345   else
 346     {
 347       /* Set errno to 0 to indicate no error, just no found record.  */
 348       __set_errno (0);
 349       /* Even though we have not found anything, the result is zero.  */
 350       retval = 0;
 351     }
 352
 353  out_close:
 354   if (sock != -1)
 355     __close_nocancel_nostatus (sock);
 356  out:
 357   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 358     {
 359       /* When we come here this means there has been a GC cycle while we
 360          were looking for the data.  This means the data might have been
 361          inconsistent.  Retry if possible.  */
 362       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 363         {
 364           /* nscd is just running gc now.  Disable using the mapping.  */
 365           if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
 366             __nscd_unmap (mapped);
 367           mapped = NO_MAPPING;
 368         }
 369
 370       if (retval != -1)
 371         {
 372           if (!alloca_aliases_len)
 373             free ((void *) aliases_len);
 374           goto retry;
 375         }
 376     }
 377
 378   if (!alloca_aliases_len)
 379     free ((void *) aliases_len);
 380   if (!alloca_key)
 381     free (key);
 382
 383   return retval;
 384 }