glibc/nscd/initgrcache.c

/* Cache handling for host lookup.
   Copyright (C) 2004 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <assert.h>
#include <errno.h>
#include <grp.h>
#include <libintl.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/mman.h>
#include <dbg_log.h>
#include <nscd.h>

#include "../nss/nsswitch.h"


/* Type of the lookup function.  */
typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
						    long int *, long int *,
						    gid_t **, long int, int *);


static const initgr_response_header notfound =
{
  .version = NSCD_VERSION,
  .found = 0,
  .ngrps = 0
};


#include "../grp/compat-initgroups.c"


static void
addinitgroupsX (struct database_dyn *db, int fd, request_header *req,
		void *key, uid_t uid, struct hashentry *he,
		struct datahead *dh)
{
  /* Search for the entry matching the key.  Please note that we don't
     look again in the table whether the dataset is now available.  We
     simply insert it.  It does not matter if it is in there twice.  The
     pruning function only will look at the timestamp.  */


  /* We allocate all data in one memory block: the iov vector,
     the response header and the dataset itself.  */
  struct dataset
  {
    struct datahead head;
    initgr_response_header resp;
    char strdata[0];
  } *dataset = NULL;

  if (__builtin_expect (debug_level > 0, 0))
    {
      if (he == NULL)
	dbg_log (_("Haven't found \"%s\" in group cache!"), (char *) key);
      else
	dbg_log (_("Reloading \"%s\" in group cache!"), (char *) key);
    }

  static service_user *group_database;
  service_user *nip = NULL;
  int no_more;

  if (group_database != NULL)
    {
      nip = group_database;
      no_more = 0;
    }
  else
    no_more = __nss_database_lookup ("group", NULL,
				     "compat [NOTFOUND=return] files", &nip);

 /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
     limit can be raised in the kernel configuration without having to
     recompile libc.  */
  long int limit = __sysconf (_SC_NGROUPS_MAX);

  long int size;
  if (limit > 0)
    /* We limit the size of the intially allocated array.  */
    size = MIN (limit, 64);
  else
    /* No fixed limit on groups.  Pick a starting buffer size.  */
    size = 16;

  long int start = 0;
  bool all_tryagain = true;

  /* This is temporary memory, we need not (ad must not) call
     mempool_alloc.  */
  // XXX This really should use alloca.  need to change the backends.
  gid_t *groups = (gid_t *) malloc (size * sizeof (gid_t));
  if (__builtin_expect (groups == NULL, 0))
    /* No more memory.  */
    goto out;

  /* Nothing added yet.  */
  while (! no_more)
    {
      enum nss_status status;
      initgroups_dyn_function fct;
      fct = __nss_lookup_function (nip, "initgroups_dyn");

      if (fct == NULL)
	{
	  status = compat_call (nip, key, -1, &start, &size, &groups,
				limit, &errno);

	  if (nss_next_action (nip, NSS_STATUS_UNAVAIL) != NSS_ACTION_CONTINUE)
	    break;
	}
      else
	status = DL_CALL_FCT (fct, (key, -1, &start, &size, &groups,
				    limit, &errno));

      if (status != NSS_STATUS_TRYAGAIN)
	all_tryagain = false;

      /* This is really only for debugging.  */
      if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
	__libc_fatal ("illegal status in internal_getgrouplist");

      if (status != NSS_STATUS_SUCCESS
	  && nss_next_action (nip, status) == NSS_ACTION_RETURN)
	 break;

      if (nip->next == NULL)
	no_more = -1;
      else
	nip = nip->next;
    }

  ssize_t total;
  ssize_t written;
 out:
  if (start == 0)
    {
      /* Nothing found.  Create a negative result record.  */
      written = total = sizeof (notfound);

      if (he != NULL && all_tryagain)
	{
	  /* If we have an old record available but cannot find one now
	     because the service is not available we keep the old record
	     and make sure it does not get removed.  */
	  if (reload_count != UINT_MAX && dh->nreloads == reload_count)
	    /* Do not reset the value if we never not reload the record.  */
	    dh->nreloads = reload_count - 1;
	}
      else
	{
	  /* We have no data.  This means we send the standard reply for this
	     case.  */
	  if (fd != -1)
	    written = TEMP_FAILURE_RETRY (write (fd, &notfound, total));

	  dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len);
	  /* If we cannot permanently store the result, so be it.  */
	  if (dataset != NULL)
	    {
	      dataset->head.allocsize = sizeof (struct dataset) + req->key_len;
	      dataset->head.recsize = total;
	      dataset->head.notfound = true;
	      dataset->head.nreloads = 0;
	      dataset->head.usable = true;

	      /* Compute the timeout time.  */
	      dataset->head.timeout = time (NULL) + db->negtimeout;

	      /* This is the reply.  */
	      memcpy (&dataset->resp, &notfound, total);

	      /* Copy the key data.  */
	      char *key_copy = memcpy (dataset->strdata, key, req->key_len);

	      /* If necessary, we also propagate the data to disk.  */
	      if (db->persistent)
		{
		  // XXX async OK?
		  uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
		  msync ((void *) pval,
			 ((uintptr_t) dataset & pagesize_m1)
			 + sizeof (struct dataset) + req->key_len, MS_ASYNC);
		}

	      /* Now get the lock to safely insert the records.  */
	      pthread_rwlock_rdlock (&db->lock);

	      if (cache_add (req->type, key_copy, req->key_len,
			     &dataset->head, true, db, uid) < 0)
		/* Ensure the data can be recovered.  */
		dataset->head.usable = false;

	      pthread_rwlock_unlock (&db->lock);

	      /* Mark the old entry as obsolete.  */
	      if (dh != NULL)
		dh->usable = false;
	    }
	  else
	    ++db->head->addfailed;
	}
    }
  else
    {

      written = total = sizeof (struct dataset) + start * sizeof (int32_t);

      /* If we refill the cache, first assume the reconrd did not
	 change.  Allocate memory on the cache since it is likely
	 discarded anyway.  If it turns out to be necessary to have a
	 new record we can still allocate real memory.  */
      bool alloca_used = false;
      dataset = NULL;

      if (he == NULL)
	{
	  dataset = (struct dataset *) mempool_alloc (db,
						      total + req->key_len);
	  if (dataset == NULL)
	    ++db->head->addfailed;
	}

      if (dataset == NULL)
	{
	  /* We cannot permanently add the result in the moment.  But
	     we can provide the result as is.  Store the data in some
	     temporary memory.  */
	  dataset = (struct dataset *) alloca (total + req->key_len);

	  /* We cannot add this record to the permanent database.  */
	  alloca_used = true;
	}

      dataset->head.allocsize = total + req->key_len;
      dataset->head.recsize = total - offsetof (struct dataset, resp);
      dataset->head.notfound = false;
      dataset->head.nreloads = he == NULL ? 0 : (dh->nreloads + 1);
      dataset->head.usable = true;

      /* Compute the timeout time.  */
      dataset->head.timeout = time (NULL) + db->postimeout;

      dataset->resp.version = NSCD_VERSION;
      dataset->resp.found = 1;
      dataset->resp.ngrps = start;

      char *cp = dataset->strdata;

      /* Copy the GID values.  If the size of the types match this is
	 very simple.  */
      if (sizeof (gid_t) == sizeof (int32_t))
	cp = mempcpy (cp, groups, start * sizeof (gid_t));
      else
	{
	  gid_t *gcp = (gid_t *) cp;

	  for (int i = 0; i < start; ++i)
	    *gcp++ = groups[i];

	  cp = (char *) gcp;
	}

      /* Finally the user name.  */
      memcpy (cp, key, req->key_len);

      /* Now we can determine whether on refill we have to create a new
	 record or not.  */
      if (he != NULL)
	{
	  assert (fd == -1);

	  if (total + req->key_len == dh->allocsize
	      && total - offsetof (struct dataset, resp) == dh->recsize
	      && memcmp (&dataset->resp, dh->data,
			 dh->allocsize - offsetof (struct dataset, resp)) == 0)
	    {
	      /* The data has not changed.  We will just bump the
		 timeout value.  Note that the new record has been
		 allocated on the stack and need not be freed.  */
	      dh->timeout = dataset->head.timeout;
	      ++dh->nreloads;
	    }
	  else
	    {
	      /* We have to create a new record.  Just allocate
		 appropriate memory and copy it.  */
	      struct dataset *newp
		= (struct dataset *) mempool_alloc (db, total + req->key_len);
	      if (newp != NULL)
		{
		  /* Adjust pointer into the memory block.  */
		  cp = (char *) newp + (cp - (char *) dataset);

		  dataset = memcpy (newp, dataset, total + req->key_len);
		  alloca_used = false;
		}

	      /* Mark the old record as obsolete.  */
	      dh->usable = false;
	    }
	}
      else
	{
	  /* We write the dataset before inserting it to the database
	     since while inserting this thread might block and so would
	     unnecessarily let the receiver wait.  */
	  assert (fd != -1);

	  written = TEMP_FAILURE_RETRY (write (fd, &dataset->resp, total));
	}


      /* Add the record to the database.  But only if it has not been
	 stored on the stack.  */
      if (! alloca_used)
	{
	  /* If necessary, we also propagate the data to disk.  */
	  if (db->persistent)
	    {
	      // XXX async OK?
	      uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
	      msync ((void *) pval,
		     ((uintptr_t) dataset & pagesize_m1) + total +
		     req->key_len, MS_ASYNC);
	    }

	  /* Now get the lock to safely insert the records.  */
	  pthread_rwlock_rdlock (&db->lock);

	  if (cache_add (INITGROUPS, cp, req->key_len, &dataset->head, true,
			 db, uid) < 0)
	    /* Could not allocate memory.  Make sure the data gets
	       discarded.  */
	    dataset->head.usable = false;

	  pthread_rwlock_unlock (&db->lock);
	}
    }

  free (groups);

  if (__builtin_expect (written != total, 0) && debug_level > 0)
    {
      char buf[256];
      dbg_log (_("short write in %s: %s"), __FUNCTION__,
	       strerror_r (errno, buf, sizeof (buf)));
    }
}


void
addinitgroups (struct database_dyn *db, int fd, request_header *req, void *key,
	       uid_t uid)
{
  addinitgroupsX (db, fd, req, key, uid, NULL, NULL);
}


void
readdinitgroups (struct database_dyn *db, struct hashentry *he,
		 struct datahead *dh)
{
  request_header req =
    {
      .type = INITGROUPS,
      .key_len = he->len
    };

  addinitgroupsX (db, -1, &req, db->data + he->key, he->owner, he, dh);
}