nscd/initgrcache.c

   1 /* Cache handling for host lookup.
   2    Copyright (C) 2004 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
   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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <assert.h>
  22 #include <errno.h>
  23 #include <grp.h>
  24 #include <libintl.h>
  25 #include <string.h>
  26 #include <time.h>
  27 #include <unistd.h>
  28 #include <sys/mman.h>
  29 #include <dbg_log.h>
  30 #include <nscd.h>
  31
  32 #include "../nss/nsswitch.h"
  33
  34
  35 /* Type of the lookup function.  */
  36 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  37                                                     long int *, long int *,
  38                                                     gid_t **, long int, int *);
  39
  40
  41 static const initgr_response_header notfound =
  42 {
  43   .version = NSCD_VERSION,
  44   .found = 0,
  45   .ngrps = 0
  46 };
  47
  48
  49 #include "../grp/compat-initgroups.c"
  50
  51
  52 static void
  53 addinitgroupsX (struct database_dyn *db, int fd, request_header *req,
  54                 void *key, uid_t uid, struct hashentry *he,
  55                 struct datahead *dh)
  56 {
  57   /* Search for the entry matching the key.  Please note that we don't
  58      look again in the table whether the dataset is now available.  We
  59      simply insert it.  It does not matter if it is in there twice.  The
  60      pruning function only will look at the timestamp.  */
  61
  62
  63   /* We allocate all data in one memory block: the iov vector,
  64      the response header and the dataset itself.  */
  65   struct dataset
  66   {
  67     struct datahead head;
  68     initgr_response_header resp;
  69     char strdata[0];
  70   } *dataset = NULL;
  71
  72   if (__builtin_expect (debug_level > 0, 0))
  73     {
  74       if (he == NULL)
  75         dbg_log (_("Haven't found \"%s\" in group cache!"), (char *) key);
  76       else
  77         dbg_log (_("Reloading \"%s\" in group cache!"), (char *) key);
  78     }
  79
  80   static service_user *group_database;
  81   service_user *nip = NULL;
  82   int no_more;
  83
  84   if (group_database != NULL)
  85     {
  86       nip = group_database;
  87       no_more = 0;
  88     }
  89   else
  90     no_more = __nss_database_lookup ("group", NULL,
  91                                      "compat [NOTFOUND=return] files", &nip);
  92
  93  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
  94      limit can be raised in the kernel configuration without having to
  95      recompile libc.  */
  96   long int limit = __sysconf (_SC_NGROUPS_MAX);
  97
  98   long int size;
  99   if (limit > 0)
 100     /* We limit the size of the intially allocated array.  */
 101     size = MIN (limit, 64);
 102   else
 103     /* No fixed limit on groups.  Pick a starting buffer size.  */
 104     size = 16;
 105
 106   long int start = 0;
 107   bool all_tryagain = true;
 108
 109   /* This is temporary memory, we need not (ad must not) call
 110      mempool_alloc.  */
 111   // XXX This really should use alloca.  need to change the backends.
 112   gid_t *groups = (gid_t *) malloc (size * sizeof (gid_t));
 113   if (__builtin_expect (groups == NULL, 0))
 114     /* No more memory.  */
 115     goto out;
 116
 117   /* Nothing added yet.  */
 118   while (! no_more)
 119     {
 120       long int prev_start = start;
 121       enum nss_status status;
 122       initgroups_dyn_function fct;
 123       fct = __nss_lookup_function (nip, "initgroups_dyn");
 124
 125       if (fct == NULL)
 126         {
 127           status = compat_call (nip, key, -1, &start, &size, &groups,
 128                                 limit, &errno);
 129
 130           if (nss_next_action (nip, NSS_STATUS_UNAVAIL) != NSS_ACTION_CONTINUE)
 131             break;
 132         }
 133       else
 134         status = DL_CALL_FCT (fct, (key, -1, &start, &size, &groups,
 135                                     limit, &errno));
 136
 137       /* Remove duplicates.  */
 138       long int cnt = prev_start;
 139       while (cnt < start)
 140         {
 141           long int inner;
 142           for (inner = 0; inner < prev_start; ++inner)
 143             if (groups[inner] == groups[cnt])
 144               break;
 145
 146           if (inner < prev_start)
 147             groups[cnt] = groups[--start];
 148           else
 149             ++cnt;
 150         }
 151
 152       if (status != NSS_STATUS_TRYAGAIN)
 153         all_tryagain = false;
 154
 155       /* This is really only for debugging.  */
 156       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 157         __libc_fatal ("illegal status in internal_getgrouplist");
 158
 159       if (status != NSS_STATUS_SUCCESS
 160           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 161          break;
 162
 163       if (nip->next == NULL)
 164         no_more = -1;
 165       else
 166         nip = nip->next;
 167     }
 168
 169   ssize_t total;
 170   ssize_t written;
 171  out:
 172   if (start == 0)
 173     {
 174       /* Nothing found.  Create a negative result record.  */
 175       written = total = sizeof (notfound);
 176
 177       if (he != NULL && all_tryagain)
 178         {
 179           /* If we have an old record available but cannot find one now
 180              because the service is not available we keep the old record
 181              and make sure it does not get removed.  */
 182           if (reload_count != UINT_MAX && dh->nreloads == reload_count)
 183             /* Do not reset the value if we never not reload the record.  */
 184             dh->nreloads = reload_count - 1;
 185         }
 186       else
 187         {
 188           /* We have no data.  This means we send the standard reply for this
 189              case.  */
 190           if (fd != -1)
 191             written = TEMP_FAILURE_RETRY (write (fd, &notfound, total));
 192
 193           dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len);
 194           /* If we cannot permanently store the result, so be it.  */
 195           if (dataset != NULL)
 196             {
 197               dataset->head.allocsize = sizeof (struct dataset) + req->key_len;
 198               dataset->head.recsize = total;
 199               dataset->head.notfound = true;
 200               dataset->head.nreloads = 0;
 201               dataset->head.usable = true;
 202
 203               /* Compute the timeout time.  */
 204               dataset->head.timeout = time (NULL) + db->negtimeout;
 205
 206               /* This is the reply.  */
 207               memcpy (&dataset->resp, &notfound, total);
 208
 209               /* Copy the key data.  */
 210               char *key_copy = memcpy (dataset->strdata, key, req->key_len);
 211
 212               /* If necessary, we also propagate the data to disk.  */
 213               if (db->persistent)
 214                 {
 215                   // XXX async OK?
 216                   uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 217                   msync ((void *) pval,
 218                          ((uintptr_t) dataset & pagesize_m1)
 219                          + sizeof (struct dataset) + req->key_len, MS_ASYNC);
 220                 }
 221
 222               /* Now get the lock to safely insert the records.  */
 223               pthread_rwlock_rdlock (&db->lock);
 224
 225               if (cache_add (req->type, key_copy, req->key_len,
 226                              &dataset->head, true, db, uid) < 0)
 227                 /* Ensure the data can be recovered.  */
 228                 dataset->head.usable = false;
 229
 230               pthread_rwlock_unlock (&db->lock);
 231
 232               /* Mark the old entry as obsolete.  */
 233               if (dh != NULL)
 234                 dh->usable = false;
 235             }
 236           else
 237             ++db->head->addfailed;
 238         }
 239     }
 240   else
 241     {
 242
 243       written = total = sizeof (struct dataset) + start * sizeof (int32_t);
 244
 245       /* If we refill the cache, first assume the reconrd did not
 246          change.  Allocate memory on the cache since it is likely
 247          discarded anyway.  If it turns out to be necessary to have a
 248          new record we can still allocate real memory.  */
 249       bool alloca_used = false;
 250       dataset = NULL;
 251
 252       if (he == NULL)
 253         {
 254           dataset = (struct dataset *) mempool_alloc (db,
 255                                                       total + req->key_len);
 256           if (dataset == NULL)
 257             ++db->head->addfailed;
 258         }
 259
 260       if (dataset == NULL)
 261         {
 262           /* We cannot permanently add the result in the moment.  But
 263              we can provide the result as is.  Store the data in some
 264              temporary memory.  */
 265           dataset = (struct dataset *) alloca (total + req->key_len);
 266
 267           /* We cannot add this record to the permanent database.  */
 268           alloca_used = true;
 269         }
 270
 271       dataset->head.allocsize = total + req->key_len;
 272       dataset->head.recsize = total - offsetof (struct dataset, resp);
 273       dataset->head.notfound = false;
 274       dataset->head.nreloads = he == NULL ? 0 : (dh->nreloads + 1);
 275       dataset->head.usable = true;
 276
 277       /* Compute the timeout time.  */
 278       dataset->head.timeout = time (NULL) + db->postimeout;
 279
 280       dataset->resp.version = NSCD_VERSION;
 281       dataset->resp.found = 1;
 282       dataset->resp.ngrps = start;
 283
 284       char *cp = dataset->strdata;
 285
 286       /* Copy the GID values.  If the size of the types match this is
 287          very simple.  */
 288       if (sizeof (gid_t) == sizeof (int32_t))
 289         cp = mempcpy (cp, groups, start * sizeof (gid_t));
 290       else
 291         {
 292           gid_t *gcp = (gid_t *) cp;
 293
 294           for (int i = 0; i < start; ++i)
 295             *gcp++ = groups[i];
 296
 297           cp = (char *) gcp;
 298         }
 299
 300       /* Finally the user name.  */
 301       memcpy (cp, key, req->key_len);
 302
 303       /* Now we can determine whether on refill we have to create a new
 304          record or not.  */
 305       if (he != NULL)
 306         {
 307           assert (fd == -1);
 308
 309           if (total + req->key_len == dh->allocsize
 310               && total - offsetof (struct dataset, resp) == dh->recsize
 311               && memcmp (&dataset->resp, dh->data,
 312                          dh->allocsize - offsetof (struct dataset, resp)) == 0)
 313             {
 314               /* The data has not changed.  We will just bump the
 315                  timeout value.  Note that the new record has been
 316                  allocated on the stack and need not be freed.  */
 317               dh->timeout = dataset->head.timeout;
 318               ++dh->nreloads;
 319             }
 320           else
 321             {
 322               /* We have to create a new record.  Just allocate
 323                  appropriate memory and copy it.  */
 324               struct dataset *newp
 325                 = (struct dataset *) mempool_alloc (db, total + req->key_len);
 326               if (newp != NULL)
 327                 {
 328                   /* Adjust pointer into the memory block.  */
 329                   cp = (char *) newp + (cp - (char *) dataset);
 330
 331                   dataset = memcpy (newp, dataset, total + req->key_len);
 332                   alloca_used = false;
 333                 }
 334
 335               /* Mark the old record as obsolete.  */
 336               dh->usable = false;
 337             }
 338         }
 339       else
 340         {
 341           /* We write the dataset before inserting it to the database
 342              since while inserting this thread might block and so would
 343              unnecessarily let the receiver wait.  */
 344           assert (fd != -1);
 345
 346           written = TEMP_FAILURE_RETRY (write (fd, &dataset->resp, total));
 347         }
 348
 349
 350       /* Add the record to the database.  But only if it has not been
 351          stored on the stack.  */
 352       if (! alloca_used)
 353         {
 354           /* If necessary, we also propagate the data to disk.  */
 355           if (db->persistent)
 356             {
 357               // XXX async OK?
 358               uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 359               msync ((void *) pval,
 360                      ((uintptr_t) dataset & pagesize_m1) + total +
 361                      req->key_len, MS_ASYNC);
 362             }
 363
 364           /* Now get the lock to safely insert the records.  */
 365           pthread_rwlock_rdlock (&db->lock);
 366
 367           if (cache_add (INITGROUPS, cp, req->key_len, &dataset->head, true,
 368                          db, uid) < 0)
 369             /* Could not allocate memory.  Make sure the data gets
 370                discarded.  */
 371             dataset->head.usable = false;
 372
 373           pthread_rwlock_unlock (&db->lock);
 374         }
 375     }
 376
 377   free (groups);
 378
 379   if (__builtin_expect (written != total, 0) && debug_level > 0)
 380     {
 381       char buf[256];
 382       dbg_log (_("short write in %s: %s"), __FUNCTION__,
 383                strerror_r (errno, buf, sizeof (buf)));
 384     }
 385 }
 386
 387
 388 void
 389 addinitgroups (struct database_dyn *db, int fd, request_header *req, void *key,
 390                uid_t uid)
 391 {
 392   addinitgroupsX (db, fd, req, key, uid, NULL, NULL);
 393 }
 394
 395
 396 void
 397 readdinitgroups (struct database_dyn *db, struct hashentry *he,
 398                  struct datahead *dh)
 399 {
 400   request_header req =
 401     {
 402       .type = INITGROUPS,
 403       .key_len = he->len
 404     };
 405
 406   addinitgroupsX (db, -1, &req, db->data + he->key, he->owner, he, dh);
 407 }