file_subs.c

早期freebsd实现

/*-
 * Copyright (c) 1992 Keith Muller.
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Keith Muller of the University of California, San Diego.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)file_subs.c	8.1 (Berkeley) 5/31/93";
#endif /* not lint */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/param.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <errno.h>
#include <sys/uio.h>
#include <stdlib.h>
#include "pax.h"
#include "extern.h"

static int
mk_link __P((register char *,register struct stat *,register char *, int));

/*
 * routines that deal with file operations such as: creating, removing;
 * and setting access modes, uid/gid and times of files
 */

#define FILEBITS		(S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
#define SETBITS			(S_ISUID | S_ISGID)
#define ABITS			(FILEBITS | SETBITS)

/*
 * file_creat()
 *	Create and open a file.
 * Return:
 *	file descriptor or -1 for failure
 */

#if __STDC__
int
file_creat(register ARCHD *arcn)
#else
int
file_creat(arcn)
	register ARCHD *arcn;
#endif
{
	int fd = -1;
	mode_t file_mode;
	int oerrno;

	/*
	 * assume file doesn't exist, so just try to create it, most times this
	 * works. We have to take special handling when the file does exist. To
	 * detect this, we use O_EXCL. For example when trying to create a
	 * file and a character device or fifo exists with the same name, we
	 * can accidently open the device by mistake (or block waiting to open)
	 * If we find that the open has failed, then figure spend the effore to
	 * figure out why. This strategy was found to have better average
	 * performance in common use than checking the file (and the path)
	 * first with lstat.
	 */
	file_mode = arcn->sb.st_mode & FILEBITS;
	if ((fd = open(arcn->name, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL,
	    file_mode)) >= 0)
		return(fd);

	/*
	 * the file seems to exist. First we try to get rid of it (found to be
	 * the second most common failure when traced). If this fails, only
	 * then we go to the expense to check and create the path to the file
	 */
	if (unlnk_exist(arcn->name, arcn->type) != 0)
		return(-1);

	for (;;) {
		/*
		 * try to open it again, if this fails, check all the nodes in
		 * the path and give it a final try. if chk_path() finds that
		 * it cannot fix anything, we will skip the last attempt
		 */
		if ((fd = open(arcn->name, O_WRONLY | O_CREAT | O_TRUNC,
		    file_mode)) >= 0)
			break;
		oerrno = errno;
		if (chk_path(arcn->name,arcn->sb.st_uid,arcn->sb.st_gid) < 0) {
			syswarn(1, oerrno, "Unable to create %s", arcn->name);
			return(-1);
		}
	}
	return(fd);
}

/*
 * file_close()
 *	Close file descriptor to a file just created by pax. Sets modes,
 *	ownership and times as required.
 * Return:
 *	0 for success, -1 for failure
 */

#if __STDC__
void
file_close(register ARCHD *arcn, int fd)
#else
void
file_close(arcn, fd)
	register ARCHD *arcn;
	int fd;
#endif
{
	int res = 0;

	if (fd < 0)
		return;
	if (close(fd) < 0)
		syswarn(0, errno, "Unable to close file descriptor on %s",
		    arcn->name);

	/*
	 * set owner/groups first as this may strip off mode bits we want
	 * then set file permission modes. Then set file access and
	 * modification times. 
	 */
	if (pids)
		res = set_ids(arcn->name, arcn->sb.st_uid, arcn->sb.st_gid);

	/*
	 * IMPORTANT SECURITY NOTE:
	 * if not preserving mode or we cannot set uid/gid, then PROHIBIT
	 * set uid/gid bits
	 */
	if (!pmode || res)
		arcn->sb.st_mode &= ~(SETBITS);
	if (pmode)
		set_pmode(arcn->name, arcn->sb.st_mode);
	if (patime || pmtime)
		set_ftime(arcn->name, arcn->sb.st_mtime, arcn->sb.st_atime, 0);
}

/*
 * lnk_creat()
 *	Create a hard link to arcn->ln_name from arcn->name. arcn->ln_name
 *	must exist; 
 * Return:
 *	0 if ok, -1 otherwise
 */

#if __STDC__
int
lnk_creat(register ARCHD *arcn)
#else
int
lnk_creat(arcn)
	register ARCHD *arcn;
#endif
{
	struct stat sb;

	/*
	 * we may be running as root, so we have to be sure that link target
	 * is not a directory, so we lstat and check
	 */
	if (lstat(arcn->ln_name, &sb) < 0) {
		syswarn(1,errno,"Unable to link to %s from %s", arcn->ln_name,
		    arcn->name);
		return(-1);
	}

	if (S_ISDIR(sb.st_mode)) {
		warn(1, "A hard link to the directory %s is not allowed",
		    arcn->ln_name);
		return(-1);
	}

	return(mk_link(arcn->ln_name, &sb, arcn->name, 0));
}

/*
 * cross_lnk()
 *	Create a hard link to arcn->org_name from arcn->name. Only used in copy
 *	with the -l flag. No warning or error if this does not succeed (we will
 *	then just create the file)
 * Return:
 *	1 if copy() should try to create this file node
 *	0 if cross_lnk() ok, -1 for fatal flaw (like linking to self).
 */

#if __STDC__
int
cross_lnk(register ARCHD *arcn)
#else
int
cross_lnk(arcn)
	register ARCHD *arcn;
#endif
{
	/*
	 * try to make a link to orginal file (-l flag in copy mode). make sure
	 * we do not try to link to directories in case we are running as root
	 * (and it might succeed).
	 */
	if (arcn->type == PAX_DIR)
		return(1);
	return(mk_link(arcn->org_name, &(arcn->sb), arcn->name, 1));
}

/*
 * chk_same()
 *	In copy mode if we are not trying to make hard links between the src
 *	and destinations, make sure we are not going to overwrite ourselves by
 *	accident. This slows things down a little, but we have to protect all
 *	those people who make typing errors.
 * Return:
 *	1 the target does not exist, go ahead and copy
 *	0 skip it file exists (-k) or may be the same as source file
 */

#if __STDC__
int
chk_same(register ARCHD *arcn)
#else
int
chk_same(arcn)
	register ARCHD *arcn;
#endif
{
	struct stat sb;

	/* 
	 * if file does not exist, return. if file exists and -k, skip it
	 * quietly
	 */
	if (lstat(arcn->name, &sb) < 0)
		return(1);
	if (kflag)
		return(0);

	/*
	 * better make sure the user does not have src == dest by mistake
	 */
	if ((arcn->sb.st_dev == sb.st_dev) && (arcn->sb.st_ino == sb.st_ino)) {
		warn(1, "Unable to copy %s, file would overwrite itself",
		    arcn->name);
		return(0);
	}
	return(1);
}

/*
 * mk_link()
 *	try to make a hard link between two files. if ign set, we do not
 *	complain.
 * Return:
 *	0 if successful (or we are done with this file but no error, such as
 *	finding the from file exists and the user has set -k).
 *	1 when ign was set to indicates we could not make the link but we
 *	should try to copy/extract the file as that might work (and is an
 *	allowed option). -1 an error occurred.
 */

#if __STDC__
static int
mk_link(register char *to, register struct stat *to_sb, register char *from,
	int ign)
#else
static int
mk_link(to, to_sb, from, ign)
	register char *to;
	register struct stat *to_sb;
	register char *from;
	int ign;
#endif
{
	struct stat sb;
	int oerrno;

	/*
	 * if from file exists, it has to be unlinked to make the link. If the
	 * file exists and -k is set, skip it quietly
	 */
	if (lstat(from, &sb) == 0) {
		if (kflag)
			return(0);

		/*
		 * make sure it is not the same file, protect the user
		 */
		if ((to_sb->st_dev==sb.st_dev)&&(to_sb->st_ino == sb.st_ino)) {
			warn(1, "Unable to link file %s to itself", to);
			return(-1);;
		}

		/*
		 * try to get rid of the file, based on the type
		 */
		if (S_ISDIR(sb.st_mode)) {
			if (rmdir(from) < 0) {
				syswarn(1, errno, "Unable to remove %s", from);
				return(-1);
			}
		} else if (unlink(from) < 0) {
			if (!ign) {
				syswarn(1, errno, "Unable to remove %s", from);
				return(-1);
			}
			return(1);
		}
	}

	/*
	 * from file is gone (or did not exist), try to make the hard link.
	 * if it fails, check the path and try it again (if chk_path() says to
	 * try again)
	 */
	for (;;) {
		if (link(to, from) == 0)
			break;
		oerrno = errno;
		if (chk_path(from, to_sb->st_uid, to_sb->st_gid) == 0)
			continue;
		if (!ign) {
			syswarn(1, oerrno, "Could not link to %s from %s", to,
			    from);
			return(-1);
		}
		return(1);
	}

	/*
	 * all right the link was made
	 */
	return(0);
}

/*
 * node_creat()
 *	create an entry in the file system (other than a file or hard link).
 *	If successful, sets uid/gid modes and times as required.
 * Return:
 *	0 if ok, -1 otherwise
 */

#if __STDC__
int
node_creat(register ARCHD *arcn)
#else
int
node_creat(arcn)
	register ARCHD *arcn;
#endif
{
	register int res;
	register int ign = 0;
	register int oerrno;
	register int pass = 0;
	mode_t file_mode;
	struct stat sb;

	/*
	 * create node based on type, if that fails try to unlink the node and
	 * try again. finally check the path and try again. As noted in the
	 * file and link creation routines, this method seems to exhibit the
	 * best performance in general use workloads.
	 */
	file_mode = arcn->sb.st_mode & FILEBITS;

	for (;;) {
		switch(arcn->type) {
		case PAX_DIR:
			res = mkdir(arcn->name, file_mode);
			if (ign)
				res = 0;
			break;
		case PAX_CHR:
			file_mode |= S_IFCHR;
			res = mknod(arcn->name, file_mode, arcn->sb.st_rdev);
			break;
		case PAX_BLK:
			file_mode |= S_IFBLK;
			res = mknod(arcn->name, file_mode, arcn->sb.st_rdev);
			break;
		case PAX_FIF:
			res = mkfifo(arcn->name, file_mode);
			break;
		case PAX_SCK:
			/*
			 * Skip sockets, operation has no meaning under BSD
			 */
			warn(0,
			    "%s skipped. Sockets cannot be copied or extracted",
			    arcn->name);
			return(-1);
		case PAX_SLK:
			if ((res = symlink(arcn->ln_name, arcn->name)) == 0)
				return(0);
			break;
		case PAX_CTG:
		case PAX_HLK:
		case PAX_HRG:
		case PAX_REG:
		default:
			/*
			 * we should never get here
			 */
			warn(0, "%s has an unknown file type, skipping",
				arcn->name);
			return(-1);
		}

		/*
		 * if we were able to create the node break out of the loop,
		 * otherwise try to unlink the node and try again. if that
		 * fails check the full path and try a final time.
		 */
		if (res == 0)
			break;

		/*
		 * we failed to make the node
		 */
		oerrno = errno;
		if ((ign = unlnk_exist(arcn->name, arcn->type)) < 0)
			return(-1);

		if (++pass <= 1)
			continue;

		if (chk_path(arcn->name,arcn->sb.st_uid,arcn->sb.st_gid) < 0) {
			syswarn(1, oerrno, "Could not create: %s", arcn->name);
			return(-1);
		}
	}

	/*
	 * we were able to create the node. set uid/gid, modes and times
	 */
	if (pids)
		res = set_ids(arcn->name, arcn->sb.st_uid, arcn->sb.st_gid);
	else
		res = 0;

	/*
	 * IMPORTANT SECURITY NOTE:
	 * if not preserving mode or we cannot set uid/gid, then PROHIBIT any
	 * set uid/gid bits
	 */
	if (!pmode || res)
		arcn->sb.st_mode &= ~(SETBITS);
	if (pmode)
		set_pmode(arcn->name, arcn->sb.st_mode);

	if (arcn->type == PAX_DIR) {
		/*
		 * Dirs must be processed again at end of extract to set times
		 * and modes to agree with those stored in the archive. However
		 * to allow extract to continue, we may have to also set owner
		 * rights. This allows nodes in the archive that are children
		 * of this directory to be extracted without failure. Both time
		 * and modes will be fixed after the entire archive is read and
		 * before pax exits.
		 */
		if (access(arcn->name, R_OK | W_OK | X_OK) < 0) {
			if (lstat(arcn->name, &sb) < 0) {
				syswarn(0, errno,"Could not access %s (stat)",
				    arcn->name);
				set_pmode(arcn->name,file_mode | S_IRWXU);
			} else {
				/*
				 * We have to add rights to the dir, so we make
				 * sure to restore the mode. The mode must be
				 * restored AS CREATED and not as stored if
				 * pmode is not set.
				 */
				set_pmode(arcn->name,
				    ((sb.st_mode & FILEBITS) | S_IRWXU));
				if (!pmode)
					arcn->sb.st_mode = sb.st_mode;
			}

			/*
			 * we have to force the mode to what was set here,
			 * since we changed it from the default as created.
			 */
			add_dir(arcn->name, arcn->nlen, &(arcn->sb), 1);
		} else if (pmode || patime || pmtime)
			add_dir(arcn->name, arcn->nlen, &(arcn->sb), 0);
	}

	if (patime || pmtime)
		set_ftime(arcn->name, arcn->sb.st_mtime, arcn->sb.st_atime, 0);