nscd/grpcache.c

   1 /* Cache handling for group lookup.
   2    Copyright (C) 1998-2002, 2003, 2004 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    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 <alloca.h>
  22 #include <assert.h>
  23 #include <errno.h>
  24 #include <error.h>
  25 #include <grp.h>
  26 #include <libintl.h>
  27 #include <stdbool.h>
  28 #include <stddef.h>
  29 #include <stdio.h>
  30 #include <stdint.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33 #include <unistd.h>
  34 #include <sys/mman.h>
  35 #include <stackinfo.h>
  36
  37 #include "nscd.h"
  38 #include "dbg_log.h"
  39
  40 /* This is the standard reply in case the service is disabled.  */
  41 static const gr_response_header disabled =
  42 {
  43   .version = NSCD_VERSION,
  44   .found = -1,
  45   .gr_name_len = 0,
  46   .gr_passwd_len = 0,
  47   .gr_gid = -1,
  48   .gr_mem_cnt = 0,
  49 };
  50
  51 /* This is the struct describing how to write this record.  */
  52 const struct iovec grp_iov_disabled =
  53 {
  54   .iov_base = (void *) &disabled,
  55   .iov_len = sizeof (disabled)
  56 };
  57
  58
  59 /* This is the standard reply in case we haven't found the dataset.  */
  60 static const gr_response_header notfound =
  61 {
  62   .version = NSCD_VERSION,
  63   .found = 0,
  64   .gr_name_len = 0,
  65   .gr_passwd_len = 0,
  66   .gr_gid = -1,
  67   .gr_mem_cnt = 0,
  68 };
  69
  70
  71 static void
  72 cache_addgr (struct database_dyn *db, int fd, request_header *req,
  73              const void *key, struct group *grp, uid_t owner,
  74              struct hashentry *he, struct datahead *dh, int errval)
  75 {
  76   ssize_t total;
  77   ssize_t written;
  78   time_t t = time (NULL);
  79
  80   /* We allocate all data in one memory block: the iov vector,
  81      the response header and the dataset itself.  */
  82   struct dataset
  83   {
  84     struct datahead head;
  85     gr_response_header resp;
  86     char strdata[0];
  87   } *dataset;
  88
  89   assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data));
  90
  91   if (grp == NULL)
  92     {
  93       if (he != NULL && errval == EAGAIN)
  94         {
  95           /* If we have an old record available but cannot find one
  96              now because the service is not available we keep the old
  97              record and make sure it does not get removed.  */
  98           if (reload_count != UINT_MAX)
  99             /* Do not reset the value if we never not reload the record.  */
 100             dh->nreloads = reload_count - 1;
 101
 102           written = total = 0;
 103         }
 104       else
 105         {
 106           /* We have no data.  This means we send the standard reply for this
 107              case.  */
 108           total = sizeof (notfound);
 109
 110           written = TEMP_FAILURE_RETRY (write (fd, &notfound, total));
 111
 112           dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len);
 113           /* If we cannot permanently store the result, so be it.  */
 114           if (dataset != NULL)
 115             {
 116               dataset->head.allocsize = sizeof (struct dataset) + req->key_len;
 117               dataset->head.recsize = total;
 118               dataset->head.notfound = true;
 119               dataset->head.nreloads = 0;
 120               dataset->head.usable = true;
 121
 122               /* Compute the timeout time.  */
 123               dataset->head.timeout = t + db->negtimeout;
 124
 125               /* This is the reply.  */
 126               memcpy (&dataset->resp, &notfound, total);
 127
 128               /* Copy the key data.  */
 129               memcpy (dataset->strdata, key, req->key_len);
 130
 131               /* If necessary, we also propagate the data to disk.  */
 132               if (db->persistent)
 133                 {
 134                   // XXX async OK?
 135                   uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 136                   msync ((void *) pval,
 137                          ((uintptr_t) dataset & pagesize_m1)
 138                          + sizeof (struct dataset) + req->key_len, MS_ASYNC);
 139                 }
 140
 141               /* Now get the lock to safely insert the records.  */
 142               pthread_rwlock_rdlock (&db->lock);
 143
 144               if (cache_add (req->type, &dataset->strdata, req->key_len,
 145                              &dataset->head, true, db, owner) < 0)
 146                 /* Ensure the data can be recovered.  */
 147                 dataset->head.usable = false;
 148
 149               pthread_rwlock_unlock (&db->lock);
 150
 151               /* Mark the old entry as obsolete.  */
 152               if (dh != NULL)
 153                 dh->usable = false;
 154             }
 155           else
 156             ++db->head->addfailed;
 157         }
 158     }
 159   else
 160     {
 161       /* Determine the I/O structure.  */
 162       size_t gr_name_len = strlen (grp->gr_name) + 1;
 163       size_t gr_passwd_len = strlen (grp->gr_passwd) + 1;
 164       size_t gr_mem_cnt = 0;
 165       uint32_t *gr_mem_len;
 166       size_t gr_mem_len_total = 0;
 167       char *gr_name;
 168       char *cp;
 169       const size_t key_len = strlen (key);
 170       const size_t buf_len = 3 + sizeof (grp->gr_gid) + key_len + 1;
 171       char *buf = alloca (buf_len);
 172       ssize_t n;
 173       size_t cnt;
 174
 175       /* We need this to insert the `bygid' entry.  */
 176       int key_offset;
 177       n = snprintf (buf, buf_len, "%d%c%n%s", grp->gr_gid, '\0',
 178                     &key_offset, (char *) key) + 1;
 179
 180       /* Determine the length of all members.  */
 181       while (grp->gr_mem[gr_mem_cnt])
 182         ++gr_mem_cnt;
 183       gr_mem_len = (uint32_t *) alloca (gr_mem_cnt * sizeof (uint32_t));
 184       for (gr_mem_cnt = 0; grp->gr_mem[gr_mem_cnt]; ++gr_mem_cnt)
 185         {
 186           gr_mem_len[gr_mem_cnt] = strlen (grp->gr_mem[gr_mem_cnt]) + 1;
 187           gr_mem_len_total += gr_mem_len[gr_mem_cnt];
 188         }
 189
 190       written = total = (sizeof (struct dataset)
 191                          + gr_mem_cnt * sizeof (uint32_t)
 192                          + gr_name_len + gr_passwd_len + gr_mem_len_total);
 193
 194       /* If we refill the cache, first assume the reconrd did not
 195          change.  Allocate memory on the cache since it is likely
 196          discarded anyway.  If it turns out to be necessary to have a
 197          new record we can still allocate real memory.  */
 198       bool alloca_used = false;
 199       dataset = NULL;
 200
 201       if (he == NULL)
 202         {
 203           dataset = (struct dataset *) mempool_alloc (db, total + n);
 204           if (dataset == NULL)
 205             ++db->head->addfailed;
 206         }
 207
 208       if (dataset == NULL)
 209         {
 210           /* We cannot permanently add the result in the moment.  But
 211              we can provide the result as is.  Store the data in some
 212              temporary memory.  */
 213           dataset = (struct dataset *) alloca (total + n);
 214
 215           /* We cannot add this record to the permanent database.  */
 216           alloca_used = true;
 217         }
 218
 219       dataset->head.allocsize = total + n;
 220       dataset->head.recsize = total - offsetof (struct dataset, resp);
 221       dataset->head.notfound = false;
 222       dataset->head.nreloads = he == NULL ? 0 : (dh->nreloads + 1);
 223       dataset->head.usable = true;
 224
 225       /* Compute the timeout time.  */
 226       dataset->head.timeout = t + db->postimeout;
 227
 228       dataset->resp.version = NSCD_VERSION;
 229       dataset->resp.found = 1;
 230       dataset->resp.gr_name_len = gr_name_len;
 231       dataset->resp.gr_passwd_len = gr_passwd_len;
 232       dataset->resp.gr_gid = grp->gr_gid;
 233       dataset->resp.gr_mem_cnt = gr_mem_cnt;
 234
 235       cp = dataset->strdata;
 236
 237       /* This is the member string length array.  */
 238       cp = mempcpy (cp, gr_mem_len, gr_mem_cnt * sizeof (uint32_t));
 239       gr_name = cp;
 240       cp = mempcpy (cp, grp->gr_name, gr_name_len);
 241       cp = mempcpy (cp, grp->gr_passwd, gr_passwd_len);
 242
 243       for (cnt = 0; cnt < gr_mem_cnt; ++cnt)
 244         cp = mempcpy (cp, grp->gr_mem[cnt], gr_mem_len[cnt]);
 245
 246       /* Finally the stringified GID value.  */
 247       memcpy (cp, buf, n);
 248       char *key_copy = cp + key_offset;
 249       assert (key_copy == (char *) rawmemchr (cp, '\0') + 1);
 250
 251       /* Now we can determine whether on refill we have to create a new
 252          record or not.  */
 253       if (he != NULL)
 254         {
 255           assert (fd == -1);
 256
 257           if (total + n == dh->allocsize
 258               && total - offsetof (struct dataset, resp) == dh->recsize
 259               && memcmp (&dataset->resp, dh->data,
 260                          dh->allocsize - offsetof (struct dataset, resp)) == 0)
 261             {
 262               /* The data has not changed.  We will just bump the
 263                  timeout value.  Note that the new record has been
 264                  allocated on the stack and need not be freed.  */
 265               dh->timeout = dataset->head.timeout;
 266               ++dh->nreloads;
 267             }
 268           else
 269             {
 270               /* We have to create a new record.  Just allocate
 271                  appropriate memory and copy it.  */
 272               struct dataset *newp
 273                 = (struct dataset *) mempool_alloc (db, total + n);
 274               if (newp != NULL)
 275                 {
 276                   /* Adjust pointers into the memory block.  */
 277                   gr_name = (char *) newp + (gr_name - (char *) dataset);
 278                   cp = (char *) newp + (cp - (char *) dataset);
 279
 280                   dataset = memcpy (newp, dataset, total + n);
 281                   alloca_used = false;
 282                 }
 283
 284               /* Mark the old record as obsolete.  */
 285               dh->usable = false;
 286             }
 287         }
 288       else
 289         {
 290           /* We write the dataset before inserting it to the database
 291              since while inserting this thread might block and so would
 292              unnecessarily let the receiver wait.  */
 293           assert (fd != -1);
 294
 295           written = TEMP_FAILURE_RETRY (write (fd, &dataset->resp, total));
 296         }
 297
 298       /* Add the record to the database.  But only if it has not been
 299          stored on the stack.  */
 300       if (! alloca_used)
 301         {
 302           /* If necessary, we also propagate the data to disk.  */
 303           if (db->persistent)
 304             {
 305               // XXX async OK?
 306               uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 307               msync ((void *) pval,
 308                      ((uintptr_t) dataset & pagesize_m1) + total + n,
 309                      MS_ASYNC);
 310             }
 311
 312           /* Now get the lock to safely insert the records.  */
 313           pthread_rwlock_rdlock (&db->lock);
 314
 315           /* NB: in the following code we always must add the entry
 316              marked with FIRST first.  Otherwise we end up with
 317              dangling "pointers" in case a latter hash entry cannot be
 318              added.  */
 319           bool first = req->type == GETGRBYNAME;
 320
 321           /* If the request was by GID, add that entry first.  */
 322           if (req->type != GETGRBYNAME)
 323             {
 324               if (cache_add (GETGRBYGID, cp, key_offset, &dataset->head, true,
 325                              db, owner) < 0)
 326                 {
 327                   /* Could not allocate memory.  Make sure the data gets
 328                      discarded.  */
 329                   dataset->head.usable = false;
 330                   goto out;
 331                 }
 332             }
 333           /* If the key is different from the name add a separate entry.  */
 334           else if (strcmp (key_copy, gr_name) != 0)
 335             {
 336               if (cache_add (GETGRBYNAME, key_copy, key_len + 1,
 337                              &dataset->head, first, db, owner) < 0)
 338                 {
 339                   /* Could not allocate memory.  Make sure the data gets
 340                      discarded.  */
 341                   dataset->head.usable = false;
 342                   goto out;
 343                 }
 344
 345               first = false;
 346             }
 347
 348           /* We have to add the value for both, byname and byuid.  */
 349           if (__builtin_expect (cache_add (GETGRBYNAME, gr_name, gr_name_len,
 350                                            &dataset->head, first, db, owner)
 351                                 == 0, 1))
 352             {
 353               if (req->type == GETGRBYNAME)
 354                 (void) cache_add (GETGRBYGID, cp, key_offset, &dataset->head,
 355                                   req->type != GETGRBYNAME, db, owner);
 356             }
 357           else if (first)
 358             /* Could not allocate memory.  Make sure the data gets
 359                discarded.  */
 360             dataset->head.usable = false;
 361
 362         out:
 363           pthread_rwlock_unlock (&db->lock);
 364         }
 365     }
 366
 367   if (__builtin_expect (written != total, 0) && debug_level > 0)
 368     {
 369       char buf[256];
 370       dbg_log (_("short write in %s: %s"),  __FUNCTION__,
 371                strerror_r (errno, buf, sizeof (buf)));
 372     }
 373 }
 374
 375
 376 union keytype
 377 {
 378   void *v;
 379   gid_t g;
 380 };
 381
 382
 383 static int
 384 lookup (int type, union keytype key, struct group *resultbufp, char *buffer,
 385         size_t buflen, struct group **grp)
 386 {
 387   if (type == GETGRBYNAME)
 388     return __getgrnam_r (key.v, resultbufp, buffer, buflen, grp);
 389   else
 390     return __getgrgid_r (key.g, resultbufp, buffer, buflen, grp);
 391 }
 392
 393
 394 static void
 395 addgrbyX (struct database_dyn *db, int fd, request_header *req,
 396           union keytype key, const char *keystr, uid_t uid,
 397           struct hashentry *he, struct datahead *dh)
 398 {
 399   /* Search for the entry matching the key.  Please note that we don't
 400      look again in the table whether the dataset is now available.  We
 401      simply insert it.  It does not matter if it is in there twice.  The
 402      pruning function only will look at the timestamp.  */
 403   size_t buflen = 1024;
 404   char *buffer = (char *) alloca (buflen);
 405   struct group resultbuf;
 406   struct group *grp;
 407   bool use_malloc = false;
 408   int errval = 0;
 409
 410   if (__builtin_expect (debug_level > 0, 0))
 411     {
 412       if (he == NULL)
 413         dbg_log (_("Haven't found \"%s\" in group cache!"), keystr);
 414       else
 415         dbg_log (_("Reloading \"%s\" in group cache!"), keystr);
 416     }
 417
 418 #if 0
 419   uid_t oldeuid = 0;
 420   if (db->secure)
 421     {
 422       oldeuid = geteuid ();
 423       pthread_seteuid_np (uid);
 424     }
 425 #endif
 426
 427   while (lookup (req->type, key, &resultbuf, buffer, buflen, &grp) != 0
 428          && (errval = errno) == ERANGE)
 429     {
 430       char *old_buffer = buffer;
 431       errno = 0;
 432 #define INCR 1024
 433
 434       if (__builtin_expect (buflen > 32768, 0))
 435         {
 436           buflen += INCR;
 437           buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
 438           if (buffer == NULL)
 439             {
 440               /* We ran out of memory.  We cannot do anything but
 441                  sending a negative response.  In reality this should
 442                  never happen.  */
 443               grp = NULL;
 444               buffer = old_buffer;
 445
 446               /* We set the error to indicate this is (possibly) a
 447                  temporary error and that it does not mean the entry
 448                  is not available at all.  */
 449               errval = EAGAIN;
 450               break;
 451             }
 452           use_malloc = true;
 453         }
 454       else
 455         /* Allocate a new buffer on the stack.  If possible combine it
 456            with the previously allocated buffer.  */
 457         buffer = (char *) extend_alloca (buffer, buflen, buflen + INCR);
 458     }
 459
 460 #if 0
 461   if (db->secure)
 462     pthread_seteuid_np (oldeuid);
 463 #endif
 464
 465   cache_addgr (db, fd, req, keystr, grp, uid, he, dh, errval);
 466
 467   if (use_malloc)
 468     free (buffer);
 469 }
 470
 471
 472 void
 473 addgrbyname (struct database_dyn *db, int fd, request_header *req,
 474              void *key, uid_t uid)
 475 {
 476   union keytype u = { .v = key };
 477
 478   addgrbyX (db, fd, req, u, key, uid, NULL, NULL);
 479 }
 480
 481
 482 void
 483 readdgrbyname (struct database_dyn *db, struct hashentry *he,
 484                struct datahead *dh)
 485 {
 486   request_header req =
 487     {
 488       .type = GETGRBYNAME,
 489       .key_len = he->len
 490     };
 491   union keytype u = { .v = db->data + he->key };
 492
 493   addgrbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);
 494 }
 495
 496
 497 void
 498 addgrbygid (struct database_dyn *db, int fd, request_header *req,
 499             void *key, uid_t uid)
 500 {
 501   char *ep;
 502   gid_t gid = strtoul ((char *) key, &ep, 10);
 503
 504   if (*(char *) key == '\0' || *ep != '\0')  /* invalid numeric uid */
 505     {
 506       if (debug_level > 0)
 507         dbg_log (_("Invalid numeric gid \"%s\"!"), (char *) key);
 508
 509       errno = EINVAL;
 510       return;
 511     }
 512
 513   union keytype u = { .g = gid };
 514
 515   addgrbyX (db, fd, req, u, key, uid, NULL, NULL);
 516 }
 517
 518
 519 void
 520 readdgrbygid (struct database_dyn *db, struct hashentry *he,
 521               struct datahead *dh)
 522 {
 523   char *ep;
 524   gid_t gid = strtoul (db->data + he->key, &ep, 10);
 525
 526   /* Since the key has been added before it must be OK.  */
 527   assert (*(db->data + he->key) != '\0' && *ep == '\0');
 528
 529   request_header req =
 530     {
 531       .type = GETGRBYGID,
 532       .key_len = he->len
 533     };
 534   union keytype u = { .g = gid };
 535
 536   addgrbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);
 537 }