nscd/pwdcache.c

   1 /* Cache handling for passwd lookup.
   2    Copyright (C) 1998-2002, 2003, 2004, 2005 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 <libintl.h>
  26 #include <pwd.h>
  27 #include <stdbool.h>
  28 #include <stddef.h>
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <time.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 pw_response_header disabled =
  42 {
  43   .version = NSCD_VERSION,
  44   .found = -1,
  45   .pw_name_len = 0,
  46   .pw_passwd_len = 0,
  47   .pw_uid = -1,
  48   .pw_gid = -1,
  49   .pw_gecos_len = 0,
  50   .pw_dir_len = 0,
  51   .pw_shell_len = 0
  52 };
  53
  54 /* This is the struct describing how to write this record.  */
  55 const struct iovec pwd_iov_disabled =
  56 {
  57   .iov_base = (void *) &disabled,
  58   .iov_len = sizeof (disabled)
  59 };
  60
  61
  62 /* This is the standard reply in case we haven't found the dataset.  */
  63 static const pw_response_header notfound =
  64 {
  65   .version = NSCD_VERSION,
  66   .found = 0,
  67   .pw_name_len = 0,
  68   .pw_passwd_len = 0,
  69   .pw_uid = -1,
  70   .pw_gid = -1,
  71   .pw_gecos_len = 0,
  72   .pw_dir_len = 0,
  73   .pw_shell_len = 0
  74 };
  75
  76
  77 static void
  78 cache_addpw (struct database_dyn *db, int fd, request_header *req,
  79              const void *key, struct passwd *pwd, uid_t owner,
  80              struct hashentry *he, struct datahead *dh, int errval)
  81 {
  82   ssize_t total;
  83   ssize_t written;
  84   time_t t = time (NULL);
  85
  86   /* We allocate all data in one memory block: the iov vector,
  87      the response header and the dataset itself.  */
  88   struct dataset
  89   {
  90     struct datahead head;
  91     pw_response_header resp;
  92     char strdata[0];
  93   } *dataset;
  94
  95   assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data));
  96
  97   if (pwd == NULL)
  98     {
  99       if (he != NULL && errval == EAGAIN)
 100         {
 101           /* If we have an old record available but cannot find one
 102              now because the service is not available we keep the old
 103              record and make sure it does not get removed.  */
 104           if (reload_count != UINT_MAX && dh->nreloads == reload_count)
 105             /* Do not reset the value if we never not reload the record.  */
 106             dh->nreloads = reload_count - 1;
 107
 108           written = total = 0;
 109         }
 110       else
 111         {
 112           /* We have no data.  This means we send the standard reply for this
 113              case.  */
 114           written = total = sizeof (notfound);
 115
 116           if (fd != -1)
 117             written = TEMP_FAILURE_RETRY (send (fd, &notfound, total,
 118                                                 MSG_NOSIGNAL));
 119
 120           dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len);
 121           /* If we cannot permanently store the result, so be it.  */
 122           if (dataset != NULL)
 123             {
 124               dataset->head.allocsize = sizeof (struct dataset) + req->key_len;
 125               dataset->head.recsize = total;
 126               dataset->head.notfound = true;
 127               dataset->head.nreloads = 0;
 128               dataset->head.usable = true;
 129
 130               /* Compute the timeout time.  */
 131               dataset->head.timeout = t + db->negtimeout;
 132
 133               /* This is the reply.  */
 134               memcpy (&dataset->resp, &notfound, total);
 135
 136               /* Copy the key data.  */
 137               char *key_copy = memcpy (dataset->strdata, key, req->key_len);
 138
 139               /* If necessary, we also propagate the data to disk.  */
 140               if (db->persistent)
 141                 {
 142                   // XXX async OK?
 143                   uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 144                   msync ((void *) pval,
 145                          ((uintptr_t) dataset & pagesize_m1)
 146                          + sizeof (struct dataset) + req->key_len, MS_ASYNC);
 147                 }
 148
 149               /* Now get the lock to safely insert the records.  */
 150               pthread_rwlock_rdlock (&db->lock);
 151
 152               if (cache_add (req->type, key_copy, req->key_len,
 153                              &dataset->head, true, db, owner) < 0)
 154                 /* Ensure the data can be recovered.  */
 155                 dataset->head.usable = false;
 156
 157
 158               pthread_rwlock_unlock (&db->lock);
 159
 160               /* Mark the old entry as obsolete.  */
 161               if (dh != NULL)
 162                 dh->usable = false;
 163             }
 164           else
 165             ++db->head->addfailed;
 166         }
 167     }
 168   else
 169     {
 170       /* Determine the I/O structure.  */
 171       size_t pw_name_len = strlen (pwd->pw_name) + 1;
 172       size_t pw_passwd_len = strlen (pwd->pw_passwd) + 1;
 173       size_t pw_gecos_len = strlen (pwd->pw_gecos) + 1;
 174       size_t pw_dir_len = strlen (pwd->pw_dir) + 1;
 175       size_t pw_shell_len = strlen (pwd->pw_shell) + 1;
 176       char *cp;
 177       const size_t key_len = strlen (key);
 178       const size_t buf_len = 3 * sizeof (pwd->pw_uid) + key_len + 1;
 179       char *buf = alloca (buf_len);
 180       ssize_t n;
 181
 182       /* We need this to insert the `byuid' entry.  */
 183       int key_offset;
 184       n = snprintf (buf, buf_len, "%d%c%n%s", pwd->pw_uid, '\0',
 185                     &key_offset, (char *) key) + 1;
 186
 187       written = total = (sizeof (struct dataset) + pw_name_len + pw_passwd_len
 188                          + pw_gecos_len + pw_dir_len + pw_shell_len);
 189
 190       /* If we refill the cache, first assume the reconrd did not
 191          change.  Allocate memory on the cache since it is likely
 192          discarded anyway.  If it turns out to be necessary to have a
 193          new record we can still allocate real memory.  */
 194       bool alloca_used = false;
 195       dataset = NULL;
 196
 197       if (he == NULL)
 198         {
 199           dataset = (struct dataset *) mempool_alloc (db, total + n);
 200           if (dataset == NULL)
 201             ++db->head->addfailed;
 202         }
 203
 204       if (dataset == NULL)
 205         {
 206           /* We cannot permanently add the result in the moment.  But
 207              we can provide the result as is.  Store the data in some
 208              temporary memory.  */
 209           dataset = (struct dataset *) alloca (total + n);
 210
 211           /* We cannot add this record to the permanent database.  */
 212           alloca_used = true;
 213         }
 214
 215       dataset->head.allocsize = total + n;
 216       dataset->head.recsize = total - offsetof (struct dataset, resp);
 217       dataset->head.notfound = false;
 218       dataset->head.nreloads = he == NULL ? 0 : (dh->nreloads + 1);
 219       dataset->head.usable = true;
 220
 221       /* Compute the timeout time.  */
 222       dataset->head.timeout = t + db->postimeout;
 223
 224       dataset->resp.version = NSCD_VERSION;
 225       dataset->resp.found = 1;
 226       dataset->resp.pw_name_len = pw_name_len;
 227       dataset->resp.pw_passwd_len = pw_passwd_len;
 228       dataset->resp.pw_uid = pwd->pw_uid;
 229       dataset->resp.pw_gid = pwd->pw_gid;
 230       dataset->resp.pw_gecos_len = pw_gecos_len;
 231       dataset->resp.pw_dir_len = pw_dir_len;
 232       dataset->resp.pw_shell_len = pw_shell_len;
 233
 234       cp = dataset->strdata;
 235
 236       /* Copy the strings over into the buffer.  */
 237       cp = mempcpy (cp, pwd->pw_name, pw_name_len);
 238       cp = mempcpy (cp, pwd->pw_passwd, pw_passwd_len);
 239       cp = mempcpy (cp, pwd->pw_gecos, pw_gecos_len);
 240       cp = mempcpy (cp, pwd->pw_dir, pw_dir_len);
 241       cp = mempcpy (cp, pwd->pw_shell, pw_shell_len);
 242
 243       /* Finally the stringified UID value.  */
 244       memcpy (cp, buf, n);
 245       char *key_copy = cp + key_offset;
 246       assert (key_copy == (char *) rawmemchr (cp, '\0') + 1);
 247
 248       /* Now we can determine whether on refill we have to create a new
 249          record or not.  */
 250       if (he != NULL)
 251         {
 252           assert (fd == -1);
 253
 254           if (total + n == dh->allocsize
 255               && total - offsetof (struct dataset, resp) == dh->recsize
 256               && memcmp (&dataset->resp, dh->data,
 257                          dh->allocsize - offsetof (struct dataset, resp)) == 0)
 258             {
 259               /* The data has not changed.  We will just bump the
 260                  timeout value.  Note that the new record has been
 261                  allocated on the stack and need not be freed.  */
 262               dh->timeout = dataset->head.timeout;
 263               ++dh->nreloads;
 264             }
 265           else
 266             {
 267               /* We have to create a new record.  Just allocate
 268                  appropriate memory and copy it.  */
 269               struct dataset *newp
 270                 = (struct dataset *) mempool_alloc (db, total + n);
 271               if (newp != NULL)
 272                 {
 273                   /* Adjust pointer into the memory block.  */
 274                   cp = (char *) newp + (cp - (char *) dataset);
 275
 276                   dataset = memcpy (newp, dataset, total + n);
 277                   alloca_used = false;
 278                 }
 279
 280               /* Mark the old record as obsolete.  */
 281               dh->usable = false;
 282             }
 283         }
 284       else
 285         {
 286           /* We write the dataset before inserting it to the database
 287              since while inserting this thread might block and so would
 288              unnecessarily let the receiver wait.  */
 289           assert (fd != -1);
 290
 291           written = writeall (fd, &dataset->resp, total);
 292         }
 293
 294
 295       /* Add the record to the database.  But only if it has not been
 296          stored on the stack.  */
 297       if (! alloca_used)
 298         {
 299           /* If necessary, we also propagate the data to disk.  */
 300           if (db->persistent)
 301             {
 302               // XXX async OK?
 303               uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 304               msync ((void *) pval,
 305                      ((uintptr_t) dataset & pagesize_m1) + total + n,
 306                      MS_ASYNC);
 307             }
 308
 309           /* Now get the lock to safely insert the records.  */
 310           pthread_rwlock_rdlock (&db->lock);
 311
 312           /* NB: in the following code we always must add the entry
 313              marked with FIRST first.  Otherwise we end up with
 314              dangling "pointers" in case a latter hash entry cannot be
 315              added.  */
 316           bool first = req->type == GETPWBYNAME;
 317
 318           /* If the request was by UID, add that entry first.  */
 319           if (req->type != GETPWBYNAME)
 320             {
 321               if (cache_add (GETPWBYUID, cp, key_offset, &dataset->head, true,
 322                              db, owner) < 0)
 323                 {
 324                   /* Could not allocate memory.  Make sure the data gets
 325                      discarded.  */
 326                   dataset->head.usable = false;
 327                   goto out;
 328                 }
 329             }
 330           /* If the key is different from the name add a separate entry.  */
 331           else if (strcmp (key_copy, dataset->strdata) != 0)
 332             {
 333               if (cache_add (GETPWBYNAME, key_copy, key_len + 1,
 334                              &dataset->head, first, db, owner) < 0)
 335                 {
 336                   /* Could not allocate memory.  Make sure the data gets
 337                      discarded.  */
 338                   dataset->head.usable = false;
 339                   goto out;
 340                 }
 341
 342               first = false;
 343             }
 344
 345           /* We have to add the value for both, byname and byuid.  */
 346           if (__builtin_expect (cache_add (GETPWBYNAME, dataset->strdata,
 347                                            pw_name_len, &dataset->head, first,
 348                                            db, owner) == 0, 1))
 349             {
 350               if (req->type == GETPWBYNAME)
 351                 (void) cache_add (GETPWBYUID, cp, key_offset, &dataset->head,
 352                                   req->type != GETPWBYNAME, db, owner);
 353             }
 354           else if (first)
 355             /* Could not allocate memory.  Make sure the data gets
 356                discarded.  */
 357             dataset->head.usable = false;
 358
 359         out:
 360           pthread_rwlock_unlock (&db->lock);
 361         }
 362     }
 363
 364   if (__builtin_expect (written != total, 0) && debug_level > 0)
 365     {
 366       char buf[256];
 367       dbg_log (_("short write in %s: %s"),  __FUNCTION__,
 368                strerror_r (errno, buf, sizeof (buf)));
 369     }
 370 }
 371
 372
 373 union keytype
 374 {
 375   void *v;
 376   uid_t u;
 377 };
 378
 379
 380 static int
 381 lookup (int type, union keytype key, struct passwd *resultbufp, char *buffer,
 382         size_t buflen, struct passwd **pwd)
 383 {
 384   if (type == GETPWBYNAME)
 385     return __getpwnam_r (key.v, resultbufp, buffer, buflen, pwd);
 386   else
 387     return __getpwuid_r (key.u, resultbufp, buffer, buflen, pwd);
 388 }
 389
 390
 391 static void
 392 addpwbyX (struct database_dyn *db, int fd, request_header *req,
 393           union keytype key, const char *keystr, uid_t c_uid,
 394           struct hashentry *he, struct datahead *dh)
 395 {
 396   /* Search for the entry matching the key.  Please note that we don't
 397      look again in the table whether the dataset is now available.  We
 398      simply insert it.  It does not matter if it is in there twice.  The
 399      pruning function only will look at the timestamp.  */
 400   size_t buflen = 1024;
 401   char *buffer = (char *) alloca (buflen);
 402   struct passwd resultbuf;
 403   struct passwd *pwd;
 404   bool use_malloc = false;
 405   int errval = 0;
 406
 407   if (__builtin_expect (debug_level > 0, 0))
 408     {
 409       if (he == NULL)
 410         dbg_log (_("Haven't found \"%s\" in password cache!"), keystr);
 411       else
 412         dbg_log (_("Reloading \"%s\" in password cache!"), keystr);
 413     }
 414
 415 #if 0
 416   uid_t oldeuid = 0;
 417   if (db->secure)
 418     {
 419       oldeuid = geteuid ();
 420       pthread_seteuid_np (c_uid);
 421     }
 422 #endif
 423
 424   while (lookup (req->type, key, &resultbuf, buffer, buflen, &pwd) != 0
 425          && (errval = errno) == ERANGE)
 426     {
 427       char *old_buffer = buffer;
 428       errno = 0;
 429
 430       if (__builtin_expect (buflen > 32768, 0))
 431         {
 432           buflen *= 2;
 433           buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
 434           if (buffer == NULL)
 435             {
 436               /* We ran out of memory.  We cannot do anything but
 437                  sending a negative response.  In reality this should
 438                  never happen.  */
 439               pwd = NULL;
 440               buffer = old_buffer;
 441
 442               /* We set the error to indicate this is (possibly) a
 443                  temporary error and that it does not mean the entry
 444                  is not available at all.  */
 445               errval = EAGAIN;
 446               break;
 447             }
 448           use_malloc = true;
 449         }
 450       else
 451         /* Allocate a new buffer on the stack.  If possible combine it
 452            with the previously allocated buffer.  */
 453         buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen);
 454     }
 455
 456 #if 0
 457   if (db->secure)
 458     pthread_seteuid_np (oldeuid);
 459 #endif
 460
 461   /* Add the entry to the cache.  */
 462   cache_addpw (db, fd, req, keystr, pwd, c_uid, he, dh, errval);
 463
 464   if (use_malloc)
 465     free (buffer);
 466 }
 467
 468
 469 void
 470 addpwbyname (struct database_dyn *db, int fd, request_header *req,
 471              void *key, uid_t c_uid)
 472 {
 473   union keytype u = { .v = key };
 474
 475   addpwbyX (db, fd, req, u, key, c_uid, NULL, NULL);
 476 }
 477
 478
 479 void
 480 readdpwbyname (struct database_dyn *db, struct hashentry *he,
 481                struct datahead *dh)
 482 {
 483   request_header req =
 484     {
 485       .type = GETPWBYNAME,
 486       .key_len = he->len
 487     };
 488   union keytype u = { .v = db->data + he->key };
 489
 490   addpwbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);
 491 }
 492
 493
 494 void
 495 addpwbyuid (struct database_dyn *db, int fd, request_header *req,
 496             void *key, uid_t c_uid)
 497 {
 498   char *ep;
 499   uid_t uid = strtoul ((char *) key, &ep, 10);
 500
 501   if (*(char *) key == '\0' || *ep != '\0')  /* invalid numeric uid */
 502     {
 503       if (debug_level > 0)
 504         dbg_log (_("Invalid numeric uid \"%s\"!"), (char *) key);
 505
 506       errno = EINVAL;
 507       return;
 508     }
 509
 510   union keytype u = { .u = uid };
 511
 512   addpwbyX (db, fd, req, u, key, c_uid, NULL, NULL);
 513 }
 514
 515
 516 void
 517 readdpwbyuid (struct database_dyn *db, struct hashentry *he,
 518               struct datahead *dh)
 519 {
 520   char *ep;
 521   uid_t uid = strtoul (db->data + he->key, &ep, 10);
 522
 523   /* Since the key has been added before it must be OK.  */
 524   assert (*(db->data + he->key) != '\0' && *ep == '\0');
 525
 526   request_header req =
 527     {
 528       .type = GETPWBYUID,
 529       .key_len = he->len
 530     };
 531   union keytype u = { .u = uid };
 532
 533   addpwbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);
 534 }