path: root/libnetfs/dir-lookup.c

/*
   Copyright (C) 1995-2002, 2013-2019 Free Software Foundation, Inc.
   Written by Michael I. Bushnell, p/BSG.

   This file is part of the GNU Hurd.

   The GNU Hurd is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2, or (at
   your option) any later version.

   The GNU Hurd 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
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with the GNU Hurd.  If not, see <http://www.gnu.org/licenses/>.  */

#include <fcntl.h>
#include <assert-backtrace.h>
#include <string.h>
#include <stdio.h>
#include <hurd/paths.h>
#include "netfs.h"
#include "fs_S.h"
#include "callbacks.h"
#include "misc.h"

kern_return_t
netfs_S_dir_lookup (struct protid *dircred,
		    const_string_t filename,
		    int flags,
		    mode_t mode,
		    retry_type *do_retry,
		    string_t retry_name,
		    mach_port_t *retry_port,
		    mach_msg_type_name_t *retry_port_type)
{
  int create;			/* true if O_CREAT flag set */
  int excl;			/* true if O_EXCL flag set */
  int mustbedir = 0;		/* true if the result must be S_IFDIR */
  int lastcomp = 0;		/* true if we are at the last component */
  int newnode = 0;		/* true if this node is newly created */
  int nsymlinks = 0;
  struct node *dnp, *np;
  char *nextname;
  char *relpath;
  error_t err;
  struct protid *newpi = NULL;
  struct iouser *user;

  if (!dircred)
    return EOPNOTSUPP;

  create = (flags & O_CREAT);
  excl = (flags & O_EXCL);

  /* Skip leading slashes */
  while (*filename == '/')
    filename++;

  /* Preserve the path relative to dircred->po->path.  */
  relpath = strdup (filename);
  if (! relpath)
    return ENOMEM;

  /* Keep a pointer to the start of the filename for length
     calculations.  */
  const char *filename_start = filename;

  *retry_port_type = MACH_MSG_TYPE_MAKE_SEND;
  *do_retry = FS_RETRY_NORMAL;
  *retry_name = '\0';

  if (*filename == '\0')
    {
      /* Set things up in the state expected by the code from gotit: on. */
      dnp = 0;
      np = dircred->po->np;
      pthread_mutex_lock (&np->lock);
      netfs_nref (np);
      goto gotit;
    }

  dnp = dircred->po->np;
  pthread_mutex_lock (&dnp->lock);

  netfs_nref (dnp);		/* acquire a reference for later netfs_nput */

  do
    {
      assert_backtrace (!lastcomp);

      /* Find the name of the next pathname component */
      nextname = index (filename, '/');

      if (nextname)
	{
	  *nextname++ = '\0';
	  while (*nextname == '/')
	    nextname++;
	  if (*nextname == '\0')
	    {
	      /* These are the rules for filenames ending in /. */
	      nextname = 0;
	      lastcomp = 1;
	      mustbedir = 1;
	      create = 0;
	    }
	  else
	    lastcomp = 0;
	}
      else
	lastcomp = 1;

      np = 0;

    retry_lookup:

      if ((dnp == netfs_root_node || dnp == dircred->po->shadow_root)
	  && filename[0] == '.' && filename[1] == '.' && filename[2] == '\0')
	if (dnp == dircred->po->shadow_root)
	  /* We're at the root of a shadow tree.  */
	  {
	    if (dircred->po->shadow_root_parent == MACH_PORT_NULL)
	      {
		/* This is a shadow root with no parent, meaning
		   we should treat it as a virtual root disconnected
		   from its real .. directory.	*/
		err = 0;
		np = dnp;
		netfs_nref (np);
	      }
	    else
	      {
		/* Punt the client up to the shadow root parent.  */
		*do_retry = FS_RETRY_REAUTH;
		*retry_port = dircred->po->shadow_root_parent;
		*retry_port_type = MACH_MSG_TYPE_COPY_SEND;
		if (lastcomp && mustbedir) /* Trailing slash.  */
		  strcpy (retry_name, "/");
		else if (!lastcomp)
		  strcpy (retry_name, nextname);
		err = 0;
		pthread_mutex_unlock (&dnp->lock);
		goto out;
	      }
	  }
	else if (dircred->po->root_parent != MACH_PORT_NULL)
	  /* We're at a real translator root; even if DIRCRED->po has a
	     shadow root, we can get here if its in a directory that was
	     renamed out from under it...  */
	  {
	    *do_retry = FS_RETRY_REAUTH;
	    *retry_port = dircred->po->root_parent;
	    *retry_port_type = MACH_MSG_TYPE_COPY_SEND;
	    if (lastcomp && mustbedir) /* Trailing slash.  */
	      strcpy (retry_name, "/");
	    else if (!lastcomp)
	      strcpy (retry_name, nextname);
	    err = 0;
	    pthread_mutex_unlock (&dnp->lock);
	    goto out;
	  }
	else
	  /* We are global root */
	  {
	    err = 0;
	    np = dnp;
	    netfs_nref (np);
	  }
      else
	/* Attempt a lookup on the next pathname component. */
	err = netfs_attempt_lookup (dircred->user, dnp, filename, &np);

      /* At this point, DNP is unlocked */

      /* Implement O_EXCL flag here */
      if (lastcomp && create && excl && !err)
	err = EEXIST;

      /* Create the new node if necessary */
      if (lastcomp && create && err == ENOENT)
	{
	  mode &= ~(S_IFMT | S_ISPARE | S_ISVTX);
	  mode |= S_IFREG;
	  pthread_mutex_lock (&dnp->lock);
	  err = netfs_attempt_create_file (dircred->user, dnp,
					   filename, mode, &np);

	  /* If someone has already created the file (between our lookup
	     and this create) then we just got EEXIST.  If we are
	     EXCL, that's fine; otherwise, we have to retry the lookup. */
	  if (err == EEXIST && !excl)
	    {
	      pthread_mutex_lock (&dnp->lock);
	      goto retry_lookup;
	    }

	  newnode = 1;
	}

      /* All remaining errors get returned to the user */
      if (err)
	goto out;

      err = netfs_validate_stat (np, dircred->user);
      if (err)
	goto out;

      if ((((flags & O_NOTRANS) == 0) || !lastcomp || mustbedir)
	  && ((np->nn_translated & S_IPTRANS)
	      || S_ISFIFO (np->nn_translated)
	      || S_ISCHR (np->nn_translated)
	      || S_ISBLK (np->nn_translated)
	      || fshelp_translated (&np->transbox)))
	{
	  mach_port_t dirport;

	  /* Create an unauthenticated port for DNP, and then
	     unlock it. */
	  err = iohelp_create_empty_iouser (&user);
	  if (! err)
	    {
	      newpi = netfs_make_protid (netfs_make_peropen (dnp, 0,
							     dircred->po),
					 user);
	      if (! newpi)
	        {
		  err = errno;
		  iohelp_free_iouser (user);
		}
	    }

	  if (! err)
	    {
	      struct fshelp_stat_cookie2 cookie = {
		.statp = &np->nn_stat,
		.modep = &np->nn_translated,
		.next = dircred->po,
	      };

	      dirport = ports_get_send_right (newpi);

	      err = fshelp_fetch_root (&np->transbox,
				       &cookie,
				       dirport,
				       dircred->user,
				       lastcomp ? flags : 0,
				       ((np->nn_translated & S_IPTRANS)
					? _netfs_translator_callback1
					: fshelp_short_circuited_callback1),
				       _netfs_translator_callback2,
				       do_retry, retry_name, retry_port);
	      /* fetch_root copies DIRPORT for success, so we always should
		 deallocate our send right.  */
	      mach_port_deallocate (mach_task_self (), dirport);
	    }

	  if (err != ENOENT)
	    {
	      *retry_port_type = MACH_MSG_TYPE_MOVE_SEND;
	      if (!err)
		{
		  char *end = strchr (retry_name, '\0');
		  if (mustbedir)
		    *end++ = '/'; /* Trailing slash.  */
		  else if (!lastcomp) {
		    if (end != retry_name)
		      *end++ = '/';
		    strcpy (end, nextname);
		  }
		}

	      {
		char *translator_path = strdupa (relpath);
		char *end;
		char *complete_path;
                struct port_info *notify_port;

		if (nextname != NULL)
		  {
		    /* This was not the last path component.
		       NEXTNAME points to the next component, locate
		       the end of the current component and use it
		       to trim TRANSLATOR_PATH.  */
		    end = nextname;
		    while (*end != 0)
		      end--;
		    translator_path[end - filename_start] = '\0';
		  }

		/* Trim trailing slashes.  */
		end = &translator_path[strlen (translator_path) - 1];
		while (*end == '/' && end >= translator_path)
		  *end = '\0', end--;

		if (dircred->po->path == NULL
		    || !strcmp (dircred->po->path,"."))
		  /* dircred is the root directory.  */
		  complete_path = translator_path;
		else
		  asprintf (&complete_path, "%s/%s", dircred->po->path,
			    translator_path);

                notify_port = newpi->pi.bucket->notify_port;
                err = fshelp_set_active_translator (notify_port,
						    complete_path,
						    &np->transbox);
		if (complete_path != translator_path)
		  free(complete_path);
		if (err)
		  {
		    ports_port_deref (newpi);
		    goto out;
		  }
	      }

	      ports_port_deref (newpi);
	      goto out;
	    }

	  ports_port_deref (newpi);

	  /* ENOENT means there was a hiccup, and the translator vanished
	     while NP was unlocked inside fshelp_fetch_root; continue as normal. */
	  err = 0;
	}

      if (S_ISLNK (np->nn_translated)
	  && (!lastcomp
	      || mustbedir	/* "foo/" must see that foo points to a dir */
	      || !(flags & (O_NOLINK|O_NOTRANS))))
	{
	  size_t nextnamelen, newnamelen, linklen;
	  char *linkbuf;

	  /* Handle symlink interpretation */
	  if (nsymlinks++ > netfs_maxsymlinks)
	    {
	      err = ELOOP;
	      goto out;
	    }

	  linklen = np->nn_stat.st_size;

	  nextnamelen = nextname ? strlen (nextname) + 1 : 0;
	  newnamelen = nextnamelen + linklen + 1 + 1;
	  linkbuf = alloca (newnamelen);

	  err = netfs_attempt_readlink (dircred->user, np, linkbuf);
	  if (err)
	    goto out;

	  if (nextname)
	    {
	      linkbuf[linklen] = '/';
	      memcpy (linkbuf + linklen + 1, nextname,
		     nextnamelen - 1);
	    }
	  if (mustbedir)
	    {
	      linkbuf[nextnamelen + linklen] = '/';
	      linkbuf[nextnamelen + linklen + 1] = '\0';
	    }
	  else
	    linkbuf[nextnamelen + linklen] = '\0';

	  if (linkbuf[0] == '/')
	    {
	      /* Punt to the caller */
	      *do_retry = FS_RETRY_MAGICAL;
	      *retry_port = MACH_PORT_NULL;
	      strcpy (retry_name, linkbuf);
	      goto out;
	    }

	  filename = linkbuf;
	  mustbedir = 0;
	  if (lastcomp)
	    {
	      lastcomp = 0;

	      /* Symlinks to nonexistent files aren't allowed to cause
		 creation, so clear the flag here. */
	      create = 0;
	    }
	  netfs_nput (np);
	  pthread_mutex_lock (&dnp->lock);
	  np = 0;
	}
      else
	{
	  /* Normal nodes here for next filename component */
	  filename = nextname;
	  netfs_nrele (dnp);

	  if (lastcomp)
	    dnp = 0;
	  else
	    {
	      dnp = np;
	      np = 0;
	    }
	}
    }
  while (filename && *filename);

  /* At this point, NP is the node to return.  */
 gotit:

  if (mustbedir || (flags & O_DIRECTORY))
    {
      err = netfs_validate_stat (np, dircred->user);
      if (err)
	goto out;
      if (!S_ISDIR (np->nn_stat.st_mode))
	{
	  err = ENOTDIR;
	  goto out;
	}
    }
  err = netfs_check_open_permissions (dircred->user, np,
				      flags, newnode);
  if (err)
    goto out;

  flags &= ~OPENONLY_STATE_MODES;

  err = iohelp_dup_iouser (&user, dircred->user);
  if (err)
    goto out;

  newpi = netfs_make_protid (netfs_make_peropen (np, flags, dircred->po),
			     user);
  if (! newpi)
    {
      iohelp_free_iouser (user);
      err = errno;
      goto out;
    }

  mach_port_t rendezvous = MACH_PORT_NULL;
  struct flock64 lock =
    {
    l_start: 0,
    l_len: 0,
    l_whence: SEEK_SET
    };

  if (flags & O_EXLOCK)
    {
      lock.l_type = F_WRLCK;
      err = fshelp_rlock_tweak (&np->userlock, &np->lock,
				&newpi->po->lock_status, flags, 0, 0,
				F_SETLK64, &lock, rendezvous);
    }
  else if (flags & O_SHLOCK)
    {
      lock.l_type = F_RDLCK;
      err = fshelp_rlock_tweak (&np->userlock, &np->lock,
				&newpi->po->lock_status, flags, 0, 0,
				F_SETLK64, &lock, rendezvous);
    }

  if (! err)
    {
      free (newpi->po->path);
      if (dircred->po->path == NULL || !strcmp (dircred->po->path,"."))
	{
	  /* dircred is the root directory.  */
	  newpi->po->path = relpath;
	  relpath = NULL; /* Do not free relpath.  */
	}
      else
	{
	  newpi->po->path = NULL;
	  asprintf (&newpi->po->path, "%s/%s", dircred->po->path, relpath);
	}

      if (! newpi->po->path)
	err = errno;

      *retry_port = ports_get_right (newpi);
      ports_port_deref (newpi);
    }

 out:
  if (np)
    netfs_nput (np);
  if (dnp)
    netfs_nrele (dnp);
  free (relpath);
  return err;
}