connections.c

/* Inner loops of cache daemon.
   Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.

   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 <error.h>
#include <errno.h>
#include <grp.h>
#include <pthread.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <libintl.h>
#include <arpa/inet.h>
#include <sys/param.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>

#include "nscd.h"
#include "dbg_log.h"

/* Wrapper functions with error checking for standard functions.  */
extern void *xmalloc (size_t n);
extern void *xcalloc (size_t n, size_t s);
extern void *xrealloc (void *o, size_t n);

/* Support to run nscd as an unprivileged user */
const char *server_user;
static uid_t server_uid;
static gid_t server_gid;
static gid_t *server_groups;
#ifndef NGROUPS
# define NGROUPS 32
#endif
static int server_ngroups = NGROUPS;

static void begin_drop_privileges (void);
static void finish_drop_privileges (void);


/* Mapping of request type to database.  */
static const dbtype serv2db[LASTDBREQ + 1] =
{
  [GETPWBYNAME] = pwddb,
  [GETPWBYUID] = pwddb,
  [GETGRBYNAME] = grpdb,
  [GETGRBYGID] = grpdb,
  [GETHOSTBYNAME] = hstdb,
  [GETHOSTBYNAMEv6] = hstdb,
  [GETHOSTBYADDR] = hstdb,
  [GETHOSTBYADDRv6] = hstdb,
};

/* Map request type to a string.  */
const char *serv2str[LASTREQ] =
{
  [GETPWBYNAME] = "GETPWBYNAME",
  [GETPWBYUID] = "GETPWBYUID",
  [GETGRBYNAME] = "GETGRBYNAME",
  [GETGRBYGID] = "GETGRBYGID",
  [GETHOSTBYNAME] = "GETHOSTBYNAME",
  [GETHOSTBYNAMEv6] = "GETHOSTBYNAMEv6",
  [GETHOSTBYADDR] = "GETHOSTBYADDR",
  [GETHOSTBYADDRv6] = "GETHOSTBYADDRv6",
  [SHUTDOWN] = "SHUTDOWN",
  [GETSTAT] = "GETSTAT",
  [INVALIDATE] = "INVALIDATE"
};

/* The control data structures for the services.  */
static struct database dbs[lastdb] =
{
  [pwddb] = {
    .lock = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP,
    .enabled = 0,
    .check_file = 1,
    .filename = "/etc/passwd",
    .module = 211,
    .disabled_iov = &pwd_iov_disabled,
    .postimeout = 3600,
    .negtimeout = 20
  },
  [grpdb] = {
    .lock = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP,
    .enabled = 0,
    .check_file = 1,
    .filename = "/etc/group",
    .module = 211,
    .disabled_iov = &grp_iov_disabled,
    .postimeout = 3600,
    .negtimeout = 60
  },
  [hstdb] = {
    .lock = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP,
    .enabled = 0,
    .check_file = 1,
    .filename = "/etc/hosts",
    .module = 211,
    .disabled_iov = &hst_iov_disabled,
    .postimeout = 3600,
    .negtimeout = 20
  }
};

/* Number of seconds between two cache pruning runs.  */
#define CACHE_PRUNE_INTERVAL	15

/* Number of threads to use.  */
int nthreads = -1;

/* Socket for incoming connections.  */
static int sock;


/* Initialize database information structures.  */
void
nscd_init (const char *conffile)
{
  struct sockaddr_un sock_addr;
  size_t cnt;

  /* Read the configuration file.  */
  if (nscd_parse_file (conffile, dbs) != 0)
    {
      /* We couldn't read the configuration file.  Disable all services
	 by shutting down the srever.  */
      dbg_log (_("cannot read configuration file; this is fatal"));
      exit (1);
    }

  /* Secure mode and unprivileged mode are incompatible */
  if (server_user != NULL && secure_in_use)
    {
      dbg_log (_("Cannot run nscd in secure mode as unprivileged user"));
      exit (1);
    }

  /* Look up unprivileged uid/gid/groups before we start listening on the
     socket  */
  if (server_user != NULL)
    begin_drop_privileges ();

  if (nthreads == -1)
    /* No configuration for this value, assume a default.  */
    nthreads = 2 * lastdb;

  for (cnt = 0; cnt < lastdb; ++cnt)
    if (dbs[cnt].enabled)
      {
	pthread_rwlock_init (&dbs[cnt].lock, NULL);

	dbs[cnt].array = (struct hashentry **)
	  calloc (dbs[cnt].module, sizeof (struct hashentry *));
	if (dbs[cnt].array == NULL)
	  error (EXIT_FAILURE, errno, "while allocating cache");

	if (dbs[cnt].check_file)
	  {
	    /* We need the modification date of the file.  */
	    struct stat st;

	    if (stat (dbs[cnt].filename, &st) < 0)
	      {
		char buf[128];
		/* We cannot stat() the file, disable file checking.  */
		dbg_log (_("cannot stat() file `%s': %s"),
			 dbs[cnt].filename,
			 strerror_r (errno, buf, sizeof (buf)));
		dbs[cnt].check_file = 0;
	      }
	    else
	      dbs[cnt].file_mtime = st.st_mtime;
	  }
      }

  /* Create the socket.  */
  sock = socket (AF_UNIX, SOCK_STREAM, 0);
  if (sock < 0)
    {
      dbg_log (_("cannot open socket: %s"), strerror (errno));
      exit (1);
    }
  /* Bind a name to the socket.  */
  sock_addr.sun_family = AF_UNIX;
  strcpy (sock_addr.sun_path, _PATH_NSCDSOCKET);
  if (bind (sock, (struct sockaddr *) &sock_addr, sizeof (sock_addr)) < 0)
    {
      dbg_log ("%s: %s", _PATH_NSCDSOCKET, strerror (errno));
      exit (1);
    }

  /* Set permissions for the socket.  */
  chmod (_PATH_NSCDSOCKET, 0666);

  /* Set the socket up to accept connections.  */
  if (listen (sock, SOMAXCONN) < 0)
    {
      dbg_log (_("cannot enable socket to accept connections: %s"),
	       strerror (errno));
      exit (1);
    }

  /* Change to unprivileged uid/gid/groups if specifed in config file */
  if (server_user != NULL)
    finish_drop_privileges ();
}


/* Close the connections.  */
void
close_sockets (void)
{
  close (sock);
}

static void
invalidate_cache (char *key)
{
  dbtype number;

  if (strcmp (key, "passwd") == 0)
    number = pwddb;
  else if (strcmp (key, "group") == 0)
    number = grpdb;
  else if (__builtin_expect (strcmp (key, "hosts"), 0) == 0)
    number = hstdb;
  else
    return;

  if (dbs[number].enabled)
    prune_cache (&dbs[number], LONG_MAX);
}


/* Handle new request.  */
static void
handle_request (int fd, request_header *req, void *key, uid_t uid)
{
  if (__builtin_expect (debug_level, 0) > 0)
    dbg_log (_("handle_request: request received (Version = %d)"),
	     req->version);

  if (__builtin_expect (req->version, NSCD_VERSION) != NSCD_VERSION)
    {
      if (debug_level > 0)
	dbg_log (_("\
cannot handle old request version %d; current version is %d"),
		 req->version, NSCD_VERSION);
      return;
    }

  if (__builtin_expect (req->type, GETPWBYNAME) >= GETPWBYNAME
      && __builtin_expect (req->type, LASTDBREQ) <= LASTDBREQ)
    {
      struct hashentry *cached;
      struct database *db = &dbs[serv2db[req->type]];

      if (__builtin_expect (debug_level, 0) > 0)
	{
	  if (req->type == GETHOSTBYADDR || req->type == GETHOSTBYADDRv6)
	    {
	      char buf[INET6_ADDRSTRLEN];

	      dbg_log ("\t%s (%s)", serv2str[req->type],
		       inet_ntop (req->type == GETHOSTBYADDR
				  ? AF_INET : AF_INET6,
				  key, buf, sizeof (buf)));
	    }
	  else
	    dbg_log ("\t%s (%s)", serv2str[req->type], (char *)key);
	}

      /* Is this service enabled?  */
      if (!db->enabled)
	{
	  /* No, sent the prepared record.  */
	  if (TEMP_FAILURE_RETRY (write (fd, db->disabled_iov->iov_base,
					 db->disabled_iov->iov_len))
	      != db->disabled_iov->iov_len
	      && __builtin_expect (debug_level, 0) > 0)
	    {
	      /* We have problems sending the result.  */
	      char buf[256];
	      dbg_log (_("cannot write result: %s"),
		       strerror_r (errno, buf, sizeof (buf)));
	    }

	  return;
	}

      /* Be sure we can read the data.  */
      pthread_rwlock_rdlock (&db->lock);

      /* See whether we can handle it from the cache.  */
      cached = (struct hashentry *) cache_search (req->type, key, req->key_len,
						  db, uid);
      if (cached != NULL)
	{
	  /* Hurray it's in the cache.  */
	  if (TEMP_FAILURE_RETRY (write (fd, cached->packet, cached->total))
	      != cached->total
	      && __builtin_expect (debug_level, 0) > 0)
	    {
	      /* We have problems sending the result.  */
	      char buf[256];
	      dbg_log (_("cannot write result: %s"),
		       strerror_r (errno, buf, sizeof (buf)));
	    }

	  pthread_rwlock_unlock (&db->lock);

	  return;
	}

      pthread_rwlock_unlock (&db->lock);
    }
  else if (__builtin_expect (debug_level, 0) > 0)
    {
      if (req->type == INVALIDATE)
	dbg_log ("\t%s (%s)", serv2str[req->type], (char *)key);
      else
	dbg_log ("\t%s", serv2str[req->type]);
    }

  /* Handle the request.  */
  switch (req->type)
    {
    case GETPWBYNAME:
      addpwbyname (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETPWBYUID:
      addpwbyuid (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETGRBYNAME:
      addgrbyname (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETGRBYGID:
      addgrbygid (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETHOSTBYNAME:
      addhstbyname (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETHOSTBYNAMEv6:
      addhstbynamev6 (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETHOSTBYADDR:
      addhstbyaddr (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETHOSTBYADDRv6:
      addhstbyaddrv6 (&dbs[serv2db[req->type]], fd, req, key, uid);
      break;

    case GETSTAT:
    case SHUTDOWN:
    case INVALIDATE:
      /* Accept shutdown, getstat and invalidate only from root */
      if (secure_in_use && uid == 0)
	{
	  if (req->type == GETSTAT)
	    send_stats (fd, dbs);
	  else if (req->type == INVALIDATE)
	    invalidate_cache (key);
	  else
	    termination_handler (0);
	}
      else
	{
	  /* Some systems have no SO_PEERCRED implementation.  They don't
	     care about security so we don't as well.  */
#ifdef SO_PEERCRED
	  struct ucred caller;
	  socklen_t optlen = sizeof (caller);

	  if (getsockopt (fd, SOL_SOCKET, SO_PEERCRED, &caller, &optlen) < 0)
	    {
	      char buf[256];

	      dbg_log (_("error getting callers id: %s"),
		       strerror_r (errno, buf, sizeof (buf)));
	    }
	  else
	    if (caller.uid == 0)
#endif
	      {
		if (req->type == GETSTAT)
		  send_stats (fd, dbs);
		else if (req->type == INVALIDATE)
		  invalidate_cache (key);
		else
		  termination_handler (0);
	      }
	}
      break;

    default:
      /* Ignore the command, it's nothing we know.  */
      break;
    }
}


/* This is the main loop.  It is replicated in different threads but the
   `poll' call makes sure only one thread handles an incoming connection.  */
static void *
__attribute__ ((__noreturn__))
nscd_run (void *p)
{
  long int my_number = (long int) p;
  struct pollfd conn;
  int run_prune = my_number < lastdb && dbs[my_number].enabled;
  time_t now = time (NULL);
  time_t next_prune = now + CACHE_PRUNE_INTERVAL;
  int timeout = run_prune ? 1000 * (next_prune - now) : -1;

  conn.fd = sock;
  conn.events = POLLRDNORM;

  while (1)
    {
      int nr = poll (&conn, 1, timeout);

      if (nr == 0)
	{
	  /* The `poll' call timed out.  It's time to clean up the cache.  */
	  assert (my_number < lastdb);
	  now = time (NULL);
	  prune_cache (&dbs[my_number], now);
	  next_prune = now + CACHE_PRUNE_INTERVAL;
	  timeout = 1000 * (next_prune - now);
	  continue;
	}

      /* We have a new incoming connection.  */
      if (conn.revents & (POLLRDNORM|POLLERR|POLLHUP|POLLNVAL))
	{
	  /* Accept the connection.  */
	  int fd = accept (conn.fd, NULL, NULL);
	  request_header req;
	  char buf[256];
	  uid_t uid = 0;

	  if (__builtin_expect (fd, 0) < 0)
	    {
	      dbg_log (_("while accepting connection: %s"),
		       strerror_r (errno, buf, sizeof (buf)));
	      continue;
	    }

	  /* Now read the request.  */
	  if (__builtin_expect (TEMP_FAILURE_RETRY (read (fd, &req,
							  sizeof (req)))
				!= sizeof (req), 0))
	    {
	      if (debug_level > 0)
		dbg_log (_("short read while reading request: %s"),
			 strerror_r (errno, buf, sizeof (buf)));
	      close (fd);
	      continue;
	    }

	  /* Some systems have no SO_PEERCRED implementation.  They don't
	     care about security so we don't as well.  */
#ifdef SO_PEERCRED
	  if (secure_in_use)
	    {
	      struct ucred caller;
	      socklen_t optlen = sizeof (caller);

	      if (getsockopt (fd, SOL_SOCKET, SO_PEERCRED,
			      &caller, &optlen) < 0)
		{
		  dbg_log (_("error getting callers id: %s"),
			   strerror_r (errno, buf, sizeof (buf)));
		  close (fd);
		  continue;
		}

	      if (req.type < GETPWBYNAME || req.type > LASTDBREQ
		  || secure[serv2db[req.type]])
		uid = caller.uid;
	    }
#endif

	  /* It should not be possible to crash the nscd with a silly
	     request (i.e., a terribly large key).  We limit the size
	     to 1kb.  */
	  if (__builtin_expect (req.key_len, 1) < 0
	      || __builtin_expect (req.key_len, 1) > 1024)
	    {
	      if (debug_level > 0)
		dbg_log (_("key length in request too long: %d"), req.key_len);
	      close (fd);
	      continue;
	    }
	  else
	    {
	      /* Get the key.  */
	      char keybuf[req.key_len];

	      if (__builtin_expect (TEMP_FAILURE_RETRY (read (fd, keybuf,
							      req.key_len))
				    != req.key_len, 0))
		{
		  if (debug_level > 0)
		    dbg_log (_("short read while reading request key: %s"),
			     strerror_r (errno, buf, sizeof (buf)));
		  close (fd);
		  continue;
		}

	      /* Phew, we got all the data, now process it.  */
	      handle_request (fd, &req, keybuf, uid);

	      /* We are done.  */
	      close (fd);
	    }
	}

      if (run_prune)
	{
	  now = time (NULL);
	  timeout = now < next_prune ? 1000 * (next_prune - now) : 0;
	}
    }
}


/* Start all the threads we want.  The initial process is thread no. 1.  */
void
start_threads (void)
{
  long int i;
  pthread_attr_t attr;
  pthread_t th;

  pthread_attr_init (&attr);
  pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);

  /* We allow less than LASTDB threads only for debugging.  */
  if (debug_level == 0)
    nthreads = MAX (nthreads, lastdb);

  for (i = 1; i < nthreads; ++i)
    pthread_create (&th, &attr, nscd_run, (void *) i);

  pthread_attr_destroy (&attr);

  nscd_run ((void *) 0);
}


/* Look up the uid, gid, and supplementary groups to run nscd as. When
   this function is called, we are not listening on the nscd socket yet so
   we can just use the ordinary lookup functions without causing a lockup  */
static void
begin_drop_privileges (void)
{
  struct passwd *pwd;

  pwd = getpwnam (server_user);

  if (pwd == NULL)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      error (EXIT_FAILURE, 0, _("Failed to run nscd as user '%s'"),
	     server_user);
    }

  server_uid = pwd->pw_uid;
  server_gid = pwd->pw_gid;

  server_groups = (gid_t *) xmalloc (server_ngroups * sizeof (gid_t));

  if (getgrouplist (server_user, server_gid, server_groups, &server_ngroups)
      == 0)
    return;

  server_groups = (gid_t *) xrealloc (server_groups,
				      server_ngroups * sizeof (gid_t));

  if (getgrouplist (server_user, server_gid, server_groups, &server_ngroups)
      == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      error (EXIT_FAILURE, errno, _("getgrouplist failed"));
    }
}


/* Call setgroups(), setgid(), and setuid() to drop root privileges and
   run nscd as the user specified in the configuration file.  */
static void
finish_drop_privileges (void)
{
  if (setgroups (server_ngroups, server_groups) == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      error (EXIT_FAILURE, errno, _("setgroups failed"));
    }

  if (setgid (server_gid) == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      perror ("setgid");
      exit (1);
    }

  if (setuid (server_uid) == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      perror ("setuid");
      exit (1);
    }
}