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