nscd/grpcache.c

   1 /* Cache handling for group lookup.
   2    Copyright (C) 1998-2005, 2006, 2007 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   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 version 2 as
   8    published by the Free Software Foundation.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 #include <alloca.h>
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <error.h>
  23 #include <grp.h>
  24 #include <libintl.h>
  25 #include <stdbool.h>
  26 #include <stddef.h>
  27 #include <stdio.h>
  28 #include <stdint.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <unistd.h>
  32 #include <sys/mman.h>
  33 #include <sys/socket.h>
  34 #include <stackinfo.h>
  35
  36 #include "nscd.h"
  37 #include "dbg_log.h"
  38 #ifdef HAVE_SENDFILE
  39 # include <kernel-features.h>
  40 #endif
  41
  42 /* This is the standard reply in case the service is disabled.  */
  43 static const gr_response_header disabled =
  44 {
  45   .version = NSCD_VERSION,
  46   .found = -1,
  47   .gr_name_len = 0,
  48   .gr_passwd_len = 0,
  49   .gr_gid = -1,
  50   .gr_mem_cnt = 0,
  51 };
  52
  53 /* This is the struct describing how to write this record.  */
  54 const struct iovec grp_iov_disabled =
  55 {
  56   .iov_base = (void *) &disabled,
  57   .iov_len = sizeof (disabled)
  58 };
  59
  60
  61 /* This is the standard reply in case we haven't found the dataset.  */
  62 static const gr_response_header notfound =
  63 {
  64   .version = NSCD_VERSION,
  65   .found = 0,
  66   .gr_name_len = 0,
  67   .gr_passwd_len = 0,
  68   .gr_gid = -1,
  69   .gr_mem_cnt = 0,
  70 };
  71
  72
  73 static void
  74 cache_addgr (struct database_dyn *db, int fd, request_header *req,
  75              const void *key, struct group *grp, uid_t owner,
  76              struct hashentry *he, struct datahead *dh, int errval)
  77 {
  78   ssize_t total;
  79   ssize_t written;
  80   time_t t = time (NULL);
  81
  82   /* We allocate all data in one memory block: the iov vector,
  83      the response header and the dataset itself.  */
  84   struct dataset
  85   {
  86     struct datahead head;
  87     gr_response_header resp;
  88     char strdata[0];
  89   } *dataset;
  90
  91   assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data));
  92
  93   if (grp == NULL)
  94     {
  95       if (he != NULL && errval == EAGAIN)
  96         {
  97           /* If we have an old record available but cannot find one
  98              now because the service is not available we keep the old
  99              record and make sure it does not get removed.  */
 100           if (reload_count != UINT_MAX)
 101             /* Do not reset the value if we never not reload the record.  */
 102             dh->nreloads = reload_count - 1;
 103
 104           written = total = 0;
 105         }
 106       else
 107         {
 108           /* We have no data.  This means we send the standard reply for this
 109              case.  */
 110           total = sizeof (notfound);
 111
 112           written = TEMP_FAILURE_RETRY (send (fd, &notfound, total,
 113                                               MSG_NOSIGNAL));
 114
 115           dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len);
 116           /* If we cannot permanently store the result, so be it.  */
 117           if (dataset != NULL)
 118             {
 119               dataset->head.allocsize = sizeof (struct dataset) + req->key_len;
 120               dataset->head.recsize = total;
 121               dataset->head.notfound = true;
 122               dataset->head.nreloads = 0;
 123               dataset->head.usable = true;
 124
 125               /* Compute the timeout time.  */
 126               dataset->head.timeout = t + db->negtimeout;
 127
 128               /* This is the reply.  */
 129               memcpy (&dataset->resp, &notfound, total);
 130
 131               /* Copy the key data.  */
 132               memcpy (dataset->strdata, key, req->key_len);
 133
 134               /* If necessary, we also propagate the data to disk.  */
 135               if (db->persistent)
 136                 {
 137                   // XXX async OK?
 138                   uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 139                   msync ((void *) pval,
 140                          ((uintptr_t) dataset & pagesize_m1)
 141                          + sizeof (struct dataset) + req->key_len, MS_ASYNC);
 142                 }
 143
 144               /* Now get the lock to safely insert the records.  */
 145               pthread_rwlock_rdlock (&db->lock);
 146
 147               if (cache_add (req->type, &dataset->strdata, req->key_len,
 148                              &dataset->head, true, db, owner) < 0)
 149                 /* Ensure the data can be recovered.  */
 150                 dataset->head.usable = false;
 151
 152               pthread_rwlock_unlock (&db->lock);
 153
 154               /* Mark the old entry as obsolete.  */
 155               if (dh != NULL)
 156                 dh->usable = false;
 157             }
 158           else
 159             ++db->head->addfailed;
 160         }
 161     }
 162   else
 163     {
 164       /* Determine the I/O structure.  */
 165       size_t gr_name_len = strlen (grp->gr_name) + 1;
 166       size_t gr_passwd_len = strlen (grp->gr_passwd) + 1;
 167       size_t gr_mem_cnt = 0;
 168       uint32_t *gr_mem_len;
 169       size_t gr_mem_len_total = 0;
 170       char *gr_name;
 171       char *cp;
 172       const size_t key_len = strlen (key);
 173       const size_t buf_len = 3 * sizeof (grp->gr_gid) + key_len + 1;
 174       char *buf = alloca (buf_len);
 175       ssize_t n;
 176       size_t cnt;
 177
 178       /* We need this to insert the `bygid' entry.  */
 179       int key_offset;
 180       n = snprintf (buf, buf_len, "%d%c%n%s", grp->gr_gid, '\0',
 181                     &key_offset, (char *) key) + 1;
 182
 183       /* Determine the length of all members.  */
 184       while (grp->gr_mem[gr_mem_cnt])
 185         ++gr_mem_cnt;
 186       gr_mem_len = (uint32_t *) alloca (gr_mem_cnt * sizeof (uint32_t));
 187       for (gr_mem_cnt = 0; grp->gr_mem[gr_mem_cnt]; ++gr_mem_cnt)
 188         {
 189           gr_mem_len[gr_mem_cnt] = strlen (grp->gr_mem[gr_mem_cnt]) + 1;
 190           gr_mem_len_total += gr_mem_len[gr_mem_cnt];
 191         }
 192
 193       written = total = (sizeof (struct dataset)
 194                          + gr_mem_cnt * sizeof (uint32_t)
 195                          + gr_name_len + gr_passwd_len + gr_mem_len_total);
 196
 197       /* If we refill the cache, first assume the reconrd did not
 198          change.  Allocate memory on the cache since it is likely
 199          discarded anyway.  If it turns out to be necessary to have a
 200          new record we can still allocate real memory.  */
 201       bool alloca_used = false;
 202       dataset = NULL;
 203
 204       if (he == NULL)
 205         {
 206           dataset = (struct dataset *) mempool_alloc (db, total + n);
 207           if (dataset == NULL)
 208             ++db->head->addfailed;
 209         }
 210
 211       if (dataset == NULL)
 212         {
 213           /* We cannot permanently add the result in the moment.  But
 214              we can provide the result as is.  Store the data in some
 215              temporary memory.  */
 216           dataset = (struct dataset *) alloca (total + n);
 217
 218           /* We cannot add this record to the permanent database.  */
 219           alloca_used = true;
 220         }
 221
 222       dataset->head.allocsize = total + n;
 223       dataset->head.recsize = total - offsetof (struct dataset, resp);
 224       dataset->head.notfound = false;
 225       dataset->head.nreloads = he == NULL ? 0 : (dh->nreloads + 1);
 226       dataset->head.usable = true;
 227
 228       /* Compute the timeout time.  */
 229       dataset->head.timeout = t + db->postimeout;
 230
 231       dataset->resp.version = NSCD_VERSION;
 232       dataset->resp.found = 1;
 233       dataset->resp.gr_name_len = gr_name_len;
 234       dataset->resp.gr_passwd_len = gr_passwd_len;
 235       dataset->resp.gr_gid = grp->gr_gid;
 236       dataset->resp.gr_mem_cnt = gr_mem_cnt;
 237
 238       cp = dataset->strdata;
 239
 240       /* This is the member string length array.  */
 241       cp = mempcpy (cp, gr_mem_len, gr_mem_cnt * sizeof (uint32_t));
 242       gr_name = cp;
 243       cp = mempcpy (cp, grp->gr_name, gr_name_len);
 244       cp = mempcpy (cp, grp->gr_passwd, gr_passwd_len);
 245
 246       for (cnt = 0; cnt < gr_mem_cnt; ++cnt)
 247         cp = mempcpy (cp, grp->gr_mem[cnt], gr_mem_len[cnt]);
 248
 249       /* Finally the stringified GID value.  */
 250       memcpy (cp, buf, n);
 251       char *key_copy = cp + key_offset;
 252       assert (key_copy == (char *) rawmemchr (cp, '\0') + 1);
 253
 254       /* Now we can determine whether on refill we have to create a new
 255          record or not.  */
 256       if (he != NULL)
 257         {
 258           assert (fd == -1);
 259
 260           if (total + n == dh->allocsize
 261               && total - offsetof (struct dataset, resp) == dh->recsize
 262               && memcmp (&dataset->resp, dh->data,
 263                          dh->allocsize - offsetof (struct dataset, resp)) == 0)
 264             {
 265               /* The data has not changed.  We will just bump the
 266                  timeout value.  Note that the new record has been
 267                  allocated on the stack and need not be freed.  */
 268               dh->timeout = dataset->head.timeout;
 269               ++dh->nreloads;
 270             }
 271           else
 272             {
 273               /* We have to create a new record.  Just allocate
 274                  appropriate memory and copy it.  */
 275               struct dataset *newp
 276                 = (struct dataset *) mempool_alloc (db, total + n);
 277               if (newp != NULL)
 278                 {
 279                   /* Adjust pointers into the memory block.  */
 280                   gr_name = (char *) newp + (gr_name - (char *) dataset);
 281                   cp = (char *) newp + (cp - (char *) dataset);
 282                   key_copy = (char *) newp + (key_copy - (char *) dataset);
 283
 284                   dataset = memcpy (newp, dataset, total + n);
 285                   alloca_used = false;
 286                 }
 287
 288               /* Mark the old record as obsolete.  */
 289               dh->usable = false;
 290             }
 291         }
 292       else
 293         {
 294           /* We write the dataset before inserting it to the database
 295              since while inserting this thread might block and so would
 296              unnecessarily let the receiver wait.  */
 297           assert (fd != -1);
 298
 299 #ifdef HAVE_SENDFILE
 300           if (__builtin_expect (db->mmap_used, 1) && !alloca_used)
 301             {
 302               assert (db->wr_fd != -1);
 303               assert ((char *) &dataset->resp > (char *) db->data);
 304               assert ((char *) &dataset->resp - (char *) db->head
 305                       + total
 306                       <= (sizeof (struct database_pers_head)
 307                           + db->head->module * sizeof (ref_t)
 308                           + db->head->data_size));
 309               written = sendfileall (fd, db->wr_fd,
 310                                      (char *) &dataset->resp
 311                                      - (char *) db->head, total);
 312 # ifndef __ASSUME_SENDFILE
 313               if (written == -1 && errno == ENOSYS)
 314                 goto use_write;
 315 # endif
 316             }
 317           else
 318 # ifndef __ASSUME_SENDFILE
 319           use_write:
 320 # endif
 321 #endif
 322             written = writeall (fd, &dataset->resp, total);
 323         }
 324
 325       /* Add the record to the database.  But only if it has not been
 326          stored on the stack.  */
 327       if (! alloca_used)
 328         {
 329           /* If necessary, we also propagate the data to disk.  */
 330           if (db->persistent)
 331             {
 332               // XXX async OK?
 333               uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 334               msync ((void *) pval,
 335                      ((uintptr_t) dataset & pagesize_m1) + total + n,
 336                      MS_ASYNC);
 337             }
 338
 339           /* Now get the lock to safely insert the records.  */
 340           pthread_rwlock_rdlock (&db->lock);
 341
 342           /* NB: in the following code we always must add the entry
 343              marked with FIRST first.  Otherwise we end up with
 344              dangling "pointers" in case a latter hash entry cannot be
 345              added.  */
 346           bool first = true;
 347
 348           /* If the request was by GID, add that entry first.  */
 349           if (req->type == GETGRBYGID)
 350             {
 351               if (cache_add (GETGRBYGID, cp, key_offset, &dataset->head, true,
 352                              db, owner) < 0)
 353                 {
 354                   /* Could not allocate memory.  Make sure the data gets
 355                      discarded.  */
 356                   dataset->head.usable = false;
 357                   goto out;
 358                 }
 359
 360               first = false;
 361             }
 362           /* If the key is different from the name add a separate entry.  */
 363           else if (strcmp (key_copy, gr_name) != 0)
 364             {
 365               if (cache_add (GETGRBYNAME, key_copy, key_len + 1,
 366                              &dataset->head, true, db, owner) < 0)
 367                 {
 368                   /* Could not allocate memory.  Make sure the data gets
 369                      discarded.  */
 370                   dataset->head.usable = false;
 371                   goto out;
 372                 }
 373
 374               first = false;
 375             }
 376
 377           /* We have to add the value for both, byname and byuid.  */
 378           if ((req->type == GETGRBYNAME || db->propagate)
 379               && __builtin_expect (cache_add (GETGRBYNAME, gr_name,
 380                                               gr_name_len,
 381                                               &dataset->head, first, db, owner)
 382                                    == 0, 1))
 383             {
 384               if (req->type == GETGRBYNAME && db->propagate)
 385                 (void) cache_add (GETGRBYGID, cp, key_offset, &dataset->head,
 386                                   req->type != GETGRBYNAME, db, owner);
 387             }
 388           else if (first)
 389             /* Could not allocate memory.  Make sure the data gets
 390                discarded.  */
 391             dataset->head.usable = false;
 392
 393         out:
 394           pthread_rwlock_unlock (&db->lock);
 395         }
 396     }
 397
 398   if (__builtin_expect (written != total, 0) && debug_level > 0)
 399     {
 400       char buf[256];
 401       dbg_log (_("short write in %s: %s"),  __FUNCTION__,
 402                strerror_r (errno, buf, sizeof (buf)));
 403     }
 404 }
 405
 406
 407 union keytype
 408 {
 409   void *v;
 410   gid_t g;
 411 };
 412
 413
 414 static int
 415 lookup (int type, union keytype key, struct group *resultbufp, char *buffer,
 416         size_t buflen, struct group **grp)
 417 {
 418   if (type == GETGRBYNAME)
 419     return __getgrnam_r (key.v, resultbufp, buffer, buflen, grp);
 420   else
 421     return __getgrgid_r (key.g, resultbufp, buffer, buflen, grp);
 422 }
 423
 424
 425 static void
 426 addgrbyX (struct database_dyn *db, int fd, request_header *req,
 427           union keytype key, const char *keystr, uid_t uid,
 428           struct hashentry *he, struct datahead *dh)
 429 {
 430   /* Search for the entry matching the key.  Please note that we don't
 431      look again in the table whether the dataset is now available.  We
 432      simply insert it.  It does not matter if it is in there twice.  The
 433      pruning function only will look at the timestamp.  */
 434   size_t buflen = 1024;
 435   char *buffer = (char *) alloca (buflen);
 436   struct group resultbuf;
 437   struct group *grp;
 438   bool use_malloc = false;
 439   int errval = 0;
 440
 441   if (__builtin_expect (debug_level > 0, 0))
 442     {
 443       if (he == NULL)
 444         dbg_log (_("Haven't found \"%s\" in group cache!"), keystr);
 445       else
 446         dbg_log (_("Reloading \"%s\" in group cache!"), keystr);
 447     }
 448
 449   while (lookup (req->type, key, &resultbuf, buffer, buflen, &grp) != 0
 450          && (errval = errno) == ERANGE)
 451     {
 452       errno = 0;
 453
 454       if (__builtin_expect (buflen > 32768, 0))
 455         {
 456           char *old_buffer = buffer;
 457           buflen *= 2;
 458           buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
 459           if (buffer == NULL)
 460             {
 461               /* We ran out of memory.  We cannot do anything but
 462                  sending a negative response.  In reality this should
 463                  never happen.  */
 464               grp = NULL;
 465               buffer = old_buffer;
 466
 467               /* We set the error to indicate this is (possibly) a
 468                  temporary error and that it does not mean the entry
 469                  is not available at all.  */
 470               errval = EAGAIN;
 471               break;
 472             }
 473           use_malloc = true;
 474         }
 475       else
 476         /* Allocate a new buffer on the stack.  If possible combine it
 477            with the previously allocated buffer.  */
 478         buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen);
 479     }
 480
 481   cache_addgr (db, fd, req, keystr, grp, uid, he, dh, errval);
 482
 483   if (use_malloc)
 484     free (buffer);
 485 }
 486
 487
 488 void
 489 addgrbyname (struct database_dyn *db, int fd, request_header *req,
 490              void *key, uid_t uid)
 491 {
 492   union keytype u = { .v = key };
 493
 494   addgrbyX (db, fd, req, u, key, uid, NULL, NULL);
 495 }
 496
 497
 498 void
 499 readdgrbyname (struct database_dyn *db, struct hashentry *he,
 500                struct datahead *dh)
 501 {
 502   request_header req =
 503     {
 504       .type = GETGRBYNAME,
 505       .key_len = he->len
 506     };
 507   union keytype u = { .v = db->data + he->key };
 508
 509   addgrbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);
 510 }
 511
 512
 513 void
 514 addgrbygid (struct database_dyn *db, int fd, request_header *req,
 515             void *key, uid_t uid)
 516 {
 517   char *ep;
 518   gid_t gid = strtoul ((char *) key, &ep, 10);
 519
 520   if (*(char *) key == '\0' || *ep != '\0')  /* invalid numeric uid */
 521     {
 522       if (debug_level > 0)
 523         dbg_log (_("Invalid numeric gid \"%s\"!"), (char *) key);
 524
 525       errno = EINVAL;
 526       return;
 527     }
 528
 529   union keytype u = { .g = gid };
 530
 531   addgrbyX (db, fd, req, u, key, uid, NULL, NULL);
 532 }
 533
 534
 535 void
 536 readdgrbygid (struct database_dyn *db, struct hashentry *he,
 537               struct datahead *dh)
 538 {
 539   char *ep;
 540   gid_t gid = strtoul (db->data + he->key, &ep, 10);
 541
 542   /* Since the key has been added before it must be OK.  */
 543   assert (*(db->data + he->key) != '\0' && *ep == '\0');
 544
 545   request_header req =
 546     {
 547       .type = GETGRBYGID,
 548       .key_len = he->len
 549     };
 550   union keytype u = { .g = gid };
 551
 552   addgrbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);
 553 }