nscd/initgrcache.c

   1 /* Cache handling for host lookup.
   2    Copyright (C) 2004-2017 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    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published
   8    by the Free Software Foundation; version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program 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
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <grp.h>
  22 #include <libintl.h>
  23 #include <string.h>
  24 #include <time.h>
  25 #include <unistd.h>
  26 #include <sys/mman.h>
  27 #include <scratch_buffer.h>
  28 #include <config.h>
  29
  30 #include "dbg_log.h"
  31 #include "nscd.h"
  32 #ifdef HAVE_SENDFILE
  33 # include <kernel-features.h>
  34 #endif
  35
  36 #include "../nss/nsswitch.h"
  37
  38 #ifdef LINK_OBSOLETE_NSL
  39 # define DEFAULT_CONFIG "compat [NOTFOUND=return] files"
  40 #else
  41 # define DEFAULT_CONFIG "files"
  42 #endif
  43
  44 /* Type of the lookup function.  */
  45 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  46                                                     long int *, long int *,
  47                                                     gid_t **, long int, int *);
  48
  49
  50 static const initgr_response_header notfound =
  51 {
  52   .version = NSCD_VERSION,
  53   .found = 0,
  54   .ngrps = 0
  55 };
  56
  57
  58 #include "../grp/compat-initgroups.c"
  59
  60
  61 static time_t
  62 addinitgroupsX (struct database_dyn *db, int fd, request_header *req,
  63                 void *key, uid_t uid, struct hashentry *const he,
  64                 struct datahead *dh)
  65 {
  66   /* Search for the entry matching the key.  Please note that we don't
  67      look again in the table whether the dataset is now available.  We
  68      simply insert it.  It does not matter if it is in there twice.  The
  69      pruning function only will look at the timestamp.  */
  70
  71
  72   /* We allocate all data in one memory block: the iov vector,
  73      the response header and the dataset itself.  */
  74   struct dataset
  75   {
  76     struct datahead head;
  77     initgr_response_header resp;
  78     char strdata[0];
  79   } *dataset = NULL;
  80
  81   if (__glibc_unlikely (debug_level > 0))
  82     {
  83       if (he == NULL)
  84         dbg_log (_("Haven't found \"%s\" in group cache!"), (char *) key);
  85       else
  86         dbg_log (_("Reloading \"%s\" in group cache!"), (char *) key);
  87     }
  88
  89   static service_user *group_database;
  90   service_user *nip;
  91   int no_more;
  92
  93   if (group_database == NULL)
  94     no_more = __nss_database_lookup ("group", NULL, DEFAULT_CONFIG,
  95                                      &group_database);
  96   else
  97     no_more = 0;
  98   nip = group_database;
  99
 100  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 101      limit can be raised in the kernel configuration without having to
 102      recompile libc.  */
 103   long int limit = __sysconf (_SC_NGROUPS_MAX);
 104
 105   long int size;
 106   if (limit > 0)
 107     /* We limit the size of the intially allocated array.  */
 108     size = MIN (limit, 64);
 109   else
 110     /* No fixed limit on groups.  Pick a starting buffer size.  */
 111     size = 16;
 112
 113   long int start = 0;
 114   bool all_tryagain = true;
 115   bool any_success = false;
 116
 117   /* This is temporary memory, we need not (and must not) call
 118      mempool_alloc.  */
 119   // XXX This really should use alloca.  need to change the backends.
 120   gid_t *groups = (gid_t *) malloc (size * sizeof (gid_t));
 121   if (__glibc_unlikely (groups == NULL))
 122     /* No more memory.  */
 123     goto out;
 124
 125   /* Nothing added yet.  */
 126   while (! no_more)
 127     {
 128       long int prev_start = start;
 129       enum nss_status status;
 130       initgroups_dyn_function fct;
 131       fct = __nss_lookup_function (nip, "initgroups_dyn");
 132
 133       if (fct == NULL)
 134         {
 135           status = compat_call (nip, key, -1, &start, &size, &groups,
 136                                 limit, &errno);
 137
 138           if (nss_next_action (nip, NSS_STATUS_UNAVAIL) != NSS_ACTION_CONTINUE)
 139             break;
 140         }
 141       else
 142         status = DL_CALL_FCT (fct, (key, -1, &start, &size, &groups,
 143                                     limit, &errno));
 144
 145       /* Remove duplicates.  */
 146       long int cnt = prev_start;
 147       while (cnt < start)
 148         {
 149           long int inner;
 150           for (inner = 0; inner < prev_start; ++inner)
 151             if (groups[inner] == groups[cnt])
 152               break;
 153
 154           if (inner < prev_start)
 155             groups[cnt] = groups[--start];
 156           else
 157             ++cnt;
 158         }
 159
 160       if (status != NSS_STATUS_TRYAGAIN)
 161         all_tryagain = false;
 162
 163       /* This is really only for debugging.  */
 164       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 165         __libc_fatal ("illegal status in internal_getgrouplist");
 166
 167       any_success |= status == NSS_STATUS_SUCCESS;
 168
 169       if (status != NSS_STATUS_SUCCESS
 170           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 171          break;
 172
 173       if (nip->next == NULL)
 174         no_more = -1;
 175       else
 176         nip = nip->next;
 177     }
 178
 179   bool all_written;
 180   ssize_t total;
 181   time_t timeout;
 182  out:
 183   all_written = true;
 184   timeout = MAX_TIMEOUT_VALUE;
 185   if (!any_success)
 186     {
 187       /* Nothing found.  Create a negative result record.  */
 188       total = sizeof (notfound);
 189
 190       if (he != NULL && all_tryagain)
 191         {
 192           /* If we have an old record available but cannot find one now
 193              because the service is not available we keep the old record
 194              and make sure it does not get removed.  */
 195           if (reload_count != UINT_MAX && dh->nreloads == reload_count)
 196             /* Do not reset the value if we never not reload the record.  */
 197             dh->nreloads = reload_count - 1;
 198
 199           /* Reload with the same time-to-live value.  */
 200           timeout = dh->timeout = time (NULL) + db->postimeout;
 201         }
 202       else
 203         {
 204           /* We have no data.  This means we send the standard reply for this
 205              case.  */
 206           if (fd != -1
 207               && TEMP_FAILURE_RETRY (send (fd, &notfound, total,
 208                                            MSG_NOSIGNAL)) != total)
 209             all_written = false;
 210
 211           /* If we have a transient error or cannot permanently store
 212              the result, so be it.  */
 213           if (all_tryagain || __builtin_expect (db->negtimeout == 0, 0))
 214             {
 215               /* Mark the old entry as obsolete.  */
 216               if (dh != NULL)
 217                 dh->usable = false;
 218             }
 219           else if ((dataset = mempool_alloc (db, (sizeof (struct dataset)
 220                                                   + req->key_len), 1)) != NULL)
 221             {
 222               timeout = datahead_init_neg (&dataset->head,
 223                                            (sizeof (struct dataset)
 224                                             + req->key_len), total,
 225                                            db->negtimeout);
 226
 227               /* This is the reply.  */
 228               memcpy (&dataset->resp, &notfound, total);
 229
 230               /* Copy the key data.  */
 231               char *key_copy = memcpy (dataset->strdata, key, req->key_len);
 232
 233               /* If necessary, we also propagate the data to disk.  */
 234               if (db->persistent)
 235                 {
 236                   // XXX async OK?
 237                   uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 238                   msync ((void *) pval,
 239                          ((uintptr_t) dataset & pagesize_m1)
 240                          + sizeof (struct dataset) + req->key_len, MS_ASYNC);
 241                 }
 242
 243               (void) cache_add (req->type, key_copy, req->key_len,
 244                                 &dataset->head, true, db, uid, he == NULL);
 245
 246               pthread_rwlock_unlock (&db->lock);
 247
 248               /* Mark the old entry as obsolete.  */
 249               if (dh != NULL)
 250                 dh->usable = false;
 251             }
 252         }
 253     }
 254   else
 255     {
 256
 257       total = offsetof (struct dataset, strdata) + start * sizeof (int32_t);
 258
 259       /* If we refill the cache, first assume the reconrd did not
 260          change.  Allocate memory on the cache since it is likely
 261          discarded anyway.  If it turns out to be necessary to have a
 262          new record we can still allocate real memory.  */
 263       bool alloca_used = false;
 264       dataset = NULL;
 265
 266       if (he == NULL)
 267         dataset = (struct dataset *) mempool_alloc (db, total + req->key_len,
 268                                                     1);
 269
 270       if (dataset == NULL)
 271         {
 272           /* We cannot permanently add the result in the moment.  But
 273              we can provide the result as is.  Store the data in some
 274              temporary memory.  */
 275           dataset = (struct dataset *) alloca (total + req->key_len);
 276
 277           /* We cannot add this record to the permanent database.  */
 278           alloca_used = true;
 279         }
 280
 281       timeout = datahead_init_pos (&dataset->head, total + req->key_len,
 282                                    total - offsetof (struct dataset, resp),
 283                                    he == NULL ? 0 : dh->nreloads + 1,
 284                                    db->postimeout);
 285
 286       dataset->resp.version = NSCD_VERSION;
 287       dataset->resp.found = 1;
 288       dataset->resp.ngrps = start;
 289
 290       char *cp = dataset->strdata;
 291
 292       /* Copy the GID values.  If the size of the types match this is
 293          very simple.  */
 294       if (sizeof (gid_t) == sizeof (int32_t))
 295         cp = mempcpy (cp, groups, start * sizeof (gid_t));
 296       else
 297         {
 298           gid_t *gcp = (gid_t *) cp;
 299
 300           for (int i = 0; i < start; ++i)
 301             *gcp++ = groups[i];
 302
 303           cp = (char *) gcp;
 304         }
 305
 306       /* Finally the user name.  */
 307       memcpy (cp, key, req->key_len);
 308
 309       assert (cp == dataset->strdata + total - offsetof (struct dataset,
 310                                                          strdata));
 311
 312       /* Now we can determine whether on refill we have to create a new
 313          record or not.  */
 314       if (he != NULL)
 315         {
 316           assert (fd == -1);
 317
 318           if (total + req->key_len == dh->allocsize
 319               && total - offsetof (struct dataset, resp) == dh->recsize
 320               && memcmp (&dataset->resp, dh->data,
 321                          dh->allocsize - offsetof (struct dataset, resp)) == 0)
 322             {
 323               /* The data has not changed.  We will just bump the
 324                  timeout value.  Note that the new record has been
 325                  allocated on the stack and need not be freed.  */
 326               dh->timeout = dataset->head.timeout;
 327               ++dh->nreloads;
 328             }
 329           else
 330             {
 331               /* We have to create a new record.  Just allocate
 332                  appropriate memory and copy it.  */
 333               struct dataset *newp
 334                 = (struct dataset *) mempool_alloc (db, total + req->key_len,
 335                                                     1);
 336               if (newp != NULL)
 337                 {
 338                   /* Adjust pointer into the memory block.  */
 339                   cp = (char *) newp + (cp - (char *) dataset);
 340
 341                   dataset = memcpy (newp, dataset, total + req->key_len);
 342                   alloca_used = false;
 343                 }
 344
 345               /* Mark the old record as obsolete.  */
 346               dh->usable = false;
 347             }
 348         }
 349       else
 350         {
 351           /* We write the dataset before inserting it to the database
 352              since while inserting this thread might block and so would
 353              unnecessarily let the receiver wait.  */
 354           assert (fd != -1);
 355
 356 #ifdef HAVE_SENDFILE
 357           if (__builtin_expect (db->mmap_used, 1) && !alloca_used)
 358             {
 359               assert (db->wr_fd != -1);
 360               assert ((char *) &dataset->resp > (char *) db->data);
 361               assert ((char *) dataset - (char *) db->head
 362                       + total
 363                       <= (sizeof (struct database_pers_head)
 364                           + db->head->module * sizeof (ref_t)
 365                           + db->head->data_size));
 366               ssize_t written = sendfileall (fd, db->wr_fd,
 367                                              (char *) &dataset->resp
 368                                              - (char *) db->head,
 369                                              dataset->head.recsize);
 370               if (written != dataset->head.recsize)
 371                 {
 372 # ifndef __ASSUME_SENDFILE
 373                   if (written == -1 && errno == ENOSYS)
 374                     goto use_write;
 375 # endif
 376                   all_written = false;
 377                 }
 378             }
 379           else
 380 # ifndef __ASSUME_SENDFILE
 381           use_write:
 382 # endif
 383 #endif
 384             if (writeall (fd, &dataset->resp, dataset->head.recsize)
 385                 != dataset->head.recsize)
 386               all_written = false;
 387         }
 388
 389
 390       /* Add the record to the database.  But only if it has not been
 391          stored on the stack.  */
 392       if (! alloca_used)
 393         {
 394           /* If necessary, we also propagate the data to disk.  */
 395           if (db->persistent)
 396             {
 397               // XXX async OK?
 398               uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 399               msync ((void *) pval,
 400                      ((uintptr_t) dataset & pagesize_m1) + total +
 401                      req->key_len, MS_ASYNC);
 402             }
 403
 404           (void) cache_add (INITGROUPS, cp, req->key_len, &dataset->head, true,
 405                             db, uid, he == NULL);
 406
 407           pthread_rwlock_unlock (&db->lock);
 408         }
 409     }
 410
 411   free (groups);
 412
 413   if (__builtin_expect (!all_written, 0) && debug_level > 0)
 414     {
 415       char buf[256];
 416       dbg_log (_("short write in %s: %s"), __FUNCTION__,
 417                strerror_r (errno, buf, sizeof (buf)));
 418     }
 419
 420   return timeout;
 421 }
 422
 423
 424 void
 425 addinitgroups (struct database_dyn *db, int fd, request_header *req, void *key,
 426                uid_t uid)
 427 {
 428   addinitgroupsX (db, fd, req, key, uid, NULL, NULL);
 429 }
 430
 431
 432 time_t
 433 readdinitgroups (struct database_dyn *db, struct hashentry *he,
 434                  struct datahead *dh)
 435 {
 436   request_header req =
 437     {
 438       .type = INITGROUPS,
 439       .key_len = he->len
 440     };
 441
 442   return addinitgroupsX (db, -1, &req, db->data + he->key, he->owner, he, dh);
 443 }