path: root/libfshelp/fshelp.h

/* FS helper library definitions
   Copyright (C) 1994, 1995, 1996 Free Software Foundation

   This program 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.

   This program 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 this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */

#ifndef _HURD_FSHELP_
#define _HURD_FSHELP_

/* This library implements various things that are generic to
   all or most implementors of the filesystem protocol.  It 
   presumes that you are using the iohelp library as well.  It
   is divided into separate facilities which may be used independently.  */

#include <errno.h>
#include <mach.h>
#include <hurd/hurd_types.h>
#include <cthreads.h>
#include <iohelp.h>

#ifndef FSHELP_EI
#define FSHELP_EI extern inline
#endif


/* Passive translator linkage */
/* These routines are self-contained and start passive translators,
   returning the control port.  They do not require multi threading
   or the ports library. */

/* A callback used by the translator starting functions, which should be a
   function that given some open flags, opens the appropiate file, and
   returns the node port.  */
typedef error_t (*fshelp_open_fn_t) (int flags,
				     file_t *node,
				     mach_msg_type_name_t *node_type);

/* Start a passive translator NAME with arguments ARGZ (length
   ARGZ_LEN).  Initialize the initports to PORTS (length PORTS_LEN),
   the initints to INTS (length INTS_LEN), and the file descriptor
   table to FDS (length FDS_LEN).  Return the control port in
   *CONTROL.  If the translator doesn't respond or die in TIMEOUT
   milliseconds (if TIMEOUT > 0), return an appropriate error.  If the
   translator dies before responding, return EDIED.  */
error_t
fshelp_start_translator_long (fshelp_open_fn_t underlying_open_fn,
			      char *name, char *argz, int argz_len,
			      mach_port_t *fds, 
			      mach_msg_type_name_t fds_type, int fds_len,
			      mach_port_t *ports, 
			      mach_msg_type_name_t ports_type, int ports_len,
			      int *ints, int ints_len,
			      int timeout, fsys_t *control);


/* Same as fshelp_start_translator_long, except the initports and ints
   are copied from our own state, fd[2] is copied from our own stderr,
   and the other fds are cleared.  */
error_t
fshelp_start_translator (fshelp_open_fn_t underlying_open_fn,
			 char *name, char *argz, int argz_len,
			 int timeout, fsys_t *control);


/* Active translator linkage */

/* These routines implement the linkage to active translators needed
   by any filesystem which supports them.  They require cthreads and
   use the passive translator routines above, but they don't require
   the ports library at all.  */

struct transbox 
{
  fsys_t active;
  struct mutex *lock;
  int flags;
  struct condition wakeup;
  void *cookie;
};
#define TRANSBOX_STARTING 1
#define TRANSBOX_WANTED 2

/* This interface is complex, because creating the ports and state
   necessary for start_translator_long is expensive.  The caller to
   fshelp_fetch_root should not need to create them on every call, since
   usually there will be an existing active translator. */

/* This routine is called by fshelp_fetch_root to fetch more information.
   Return the owner and group of the underlying translated file in *UID and
   *GID; point *ARGZ at the entire passive translator spec for the file
   (setting *ARGZ_LEN to the length.)  If there is no passive translator,
   then return ENOENT.  COOKIE1 is the cookie passed in fshelp_transbox_init.
   COOKIE2 is the cookie passed in the call to fshelp_fetch_root.  */
typedef error_t (*fshelp_fetch_root_callback1_t) (void *cookie1, void *cookie2,
						  uid_t *uid, gid_t *gid, 
						  char **argz, int *argz_len);

/* This routine is called by fshelp_fetch_root to fetch more information.
   Return an unauthenticated node for the file itself in *UNDERLYING and
   *UNDERLYING_TYPE (opened with FLAGS).  COOKIE1 is the cookie passed in
   fshelp_transbox_init.  COOKIE2 is the cookie passed in the call to
   fshelp_fetch_root.  */
typedef error_t (*fshelp_fetch_root_callback2_t) (void *cookie1, void *cookie2,
						  int flags,
						  mach_port_t *underlying,
						  mach_msg_type_name_t
						  *underlying_type);

/* Fetch the root from TRANSBOX.  DOTDOT is an unauthenticated port
   for the directory in which we are looking; USER specifies the ids
   of the user responsible for the call.  FLAGS are as for
   dir_pathtrans (but O_CREAT and O_EXCL are not meaningful and are
   ignored).  The trasnbox lock (as set by fshelp_transbox_init) must
   be held before the call, and will be held upon return, but may be
   released during the operation of the call.  */
error_t
fshelp_fetch_root (struct transbox *transbox, void *cookie,
		   file_t dotdot, 
		   struct iouser *user,
		   int flags,
		   fshelp_fetch_root_callback1_t callback1,
		   fshelp_fetch_root_callback2_t callback2,
		   retry_type *retry, char *retryname, mach_port_t *root);

void
fshelp_transbox_init (struct transbox *transbox,
		      struct mutex *lock,
		      void *cookie);

/* Return true iff there is an active translator on this box */
FSHELP_EI int
fshelp_translated (struct transbox *box)
{
  return (box->active != MACH_PORT_NULL);
}

/* Atomically replace the existing active translator port for this box
   with NEWACTIVE.  If EXCL is non-zero then don't frob an existing
   active; return EBUSY instead.  */
error_t fshelp_set_active (struct transbox *box,
			   fsys_t newactive, int excl);

/* Fetch the control port to make a request on it.  It's a bad idea
   to do fsys_getroot with the result; use fetch_root instead. */
error_t fshelp_fetch_control (struct transbox *box,
			      mach_port_t *control);

/* A transbox is being deallocated, clean associated state. */
void fshelp_drop_transbox (struct transbox *box);



/* Flock handling. */
struct lock_box
{
  int type;
  struct condition wait;
  int waiting;
  int shcount;
};

/* Call when a user makes a request to acquire an lock via file_lock.
   There should be one lock box per object and one int per open; these
   are passed as arguments BOX and USER respectively.  FLAGS are as
   per file_lock.  MUT is a mutex which will be held whenever this
   routine is called, to lock BOX->wait.  */ 
error_t fshelp_acquire_lock (struct lock_box *box, int *user, 
			     struct mutex *mut, int flags);

  
/* Initialize lock_box BOX.  (The user int passed to fshelp_acquire_lock
   should be initialized with LOCK_UN.).  */
void fshelp_lock_init (struct lock_box *box);



struct port_bucket;		/* shut up C compiler */
/* Return an identity port in *PT for the node numbered FILENO,
   suitable for returning from io_identity; exactly one send right
   must be created from the returned value.  FILENO should be the same
   value returned as the `fileno' out-parameter in io_identity, and in
   the enclosing directory (except for mount points), and in the
   st_ino stat field.  BUCKET should be a ports port bucket; fshelp
   requires the caller to make sure port operations (for no-senders
   notifications) are used.
   */
error_t fshelp_get_identity (struct port_bucket *bucket,
			     ino_t fileno, mach_port_t *pt);



/* Try to hand off responsibility from a translator to the server located on
   the node SERVER_NAME.  REQUESTOR is the translator's bootstrap port, and
   ARGV is the command line.  If SERVER_NAME is NULL, then a name is
   concocted by appending ARGV[0] to _SERVERS.  */
error_t fshelp_delegate_translation (char *server_name,
				     mach_port_t requestor, char **argv);

struct idvec;			/* Include <idvec.h> to get the real thing. */

/* If SUID or SGID is true, adds UID and/or GID respectively to the
   authentication in PORTS[INIT_PORT_AUTH], and replaces it with the result.
   All the other ports in PORTS and FDS are then reauthenticated, using any
   privileges available through AUTH.  If GET_FILE_IDS is non-NULL, and the
   auth port in PORTS[INIT_PORT_AUTH] is bogus, it is called to get a list of
   uids and gids from the file to use as a replacement.  If SECURE is
   non-NULL, whether not the added ids are new is returned in it.  If either
   the uid or gid case fails, then the other may still be applied.  */
error_t
fshelp_exec_reauth (int suid, uid_t uid, int sgid, gid_t gid,
		    auth_t auth,
		    error_t
		      (*get_file_ids)(struct idvec *uids, struct idvec *gids),
		    mach_port_t *ports, mach_msg_type_number_t num_ports,
		    mach_port_t *fds, mach_msg_type_number_t num_fds,
		    int *secure);

struct argp;			/* Include <argp.h> to get the real thing.  */

/* Invoke ARGP with data from DATA & LEN, in the standard way.  */
error_t fshelp_set_options (struct argp *argp, int flags,
			    char *argz, size_t argz_len, void *input);

/* Puts data from the malloced buffer BUF, LEN bytes long, into RBUF & RLEN,
   suitable for returning from a mach rpc.  If LEN > 0, BUF is freed,
   regardless of whether an error is returned or not.  */
error_t fshelp_return_malloced_buffer (char *buf, size_t len,
				       char **rbuf,
				       mach_msg_type_number_t *rlen);



/*  Standardized filesystem permission checking */

/* Check to see whether USER should be considered the owner of the
   file identified by ST.  If so, return zero; otherwise return an
   appropriate error code. */
FSHELP_EI error_t
fshelp_isowner (struct stat *st, struct iouser *user)
{
  /* Permitted if the user has the owner UID, the superuser UID, or if
     the user is in the group of the file and has the group ID as
     their user ID.  */
  if (idvec_contains (user->uids, st->st_uid)
      || idvec_contains (user->uids, 0)
      || (idvec_contains (user->gids, st->st_gid)
	  && idvec_contains (user->uids, st->st_gid)))
    return 0;
  else 
    return EPERM;
}


/* Check to see whether the user USER can operate on a file identified
   by ST.  OP is one of S_IREAD, S_IWRITE, and S_IEXEC.  If the access
   is permitted, return zero; otherwise return an appropriate error
   code.  */
FSHELP_EI error_t
fshelp_access (struct stat *st, int op, struct iouser *user)
{
  if (idvec_contains (user->uids, 0))
    gotit = 1;
  else if (user->uids->num == 0 && (st->st_mode & S_IUSEUNK))
    gotit = st->st_mode & (op << S_IUSEUNKSHIFT);
  else if (!fshelp_isowner (st, user))
    gotit = st->st_mode & op;
  else if (idvec_contains (user->gids, st->st_gid))
    gotit = st->st_mode & (op >> 3);
  else
    gotit = st->st_mode & (op >> 6);
  return gotit ? 0 : EACCES;
}

/* Check to see whether USER is allowed to modify DIR with respect to
   existing file ST.  (If there is no existing file, pass 0 for ST.)
   If the access is permissable return 0; otherwise return an
   appropriate error code.  */
FSHELP_EI error_t
fshelp_checkdirmod (struct stat *dir, struct stat *st, struct iouser *user)
{
  error_t err;
  
  /* The user must be able to write the directory. */
  err = fshelp_access (dir, S_IWRITE, user);
  if (err)
    return err;

  /* If the directory is sticky, the user must own either it or the file.  */
  if ((dir->st_mode & S_ISVTX) && st
      && fshelp_isowner (dir, user) && fshelp_isowner (st, user))
    return EACCES;

  return 0;
}

#endif