xref: /src/bin/pax/tar.c

/*	$NetBSD: tar.c,v 1.60 2004/10/17 18:51:29 dsl Exp $	*/

/*-
 * 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. 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.
 */

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#include <sys/cdefs.h>
#if !defined(lint)
#if 0
static char sccsid[] = "@(#)tar.c	8.2 (Berkeley) 4/18/94";
#else
__RCSID("$NetBSD: tar.c,v 1.60 2004/10/17 18:51:29 dsl Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/param.h>

#include <ctype.h>
#include <errno.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "pax.h"
#include "extern.h"
#include "tar.h"

/*
 * Routines for reading, writing and header identify of various versions of tar
 */

static int expandname(char *, size_t,  char **, size_t *, const char *, size_t);
static void longlink(ARCHD *, int);
static u_long tar_chksm(char *, int);
static char *name_split(char *, int);
static int ul_oct(u_long, char *, int, int);
#if !defined(NET2_STAT) && !defined(_LP64)
static int ull_oct(unsigned long long, char *, int, int);
#endif
static int tar_gnutar_exclude_one(const char *, size_t);
static int check_sum(char *, size_t, char *, size_t, int);

/*
 * Routines common to all versions of tar
 */

static int tar_nodir;			/* do not write dirs under old tar */
int is_gnutar;				/* behave like gnu tar; enable gnu
					 * extensions and skip end-ofvolume
					 * checks
					 */
static int seen_gnu_warning;		/* Have we warned yet? */
static char *gnu_hack_string;		/* ././@LongLink hackery */
static int gnu_hack_len;		/* len of gnu_hack_string */
char *gnu_name_string;			/* ././@LongLink hackery name */
char *gnu_link_string;			/* ././@LongLink hackery link */
size_t gnu_name_length;			/* ././@LongLink hackery name */
size_t gnu_link_length;			/* ././@LongLink hackery link */
static int gnu_short_trailer;		/* gnu short trailer */

static const char LONG_LINK[] = "././@LongLink";

#ifdef _PAX_
char DEV_0[] = "/dev/rst0";
char DEV_1[] = "/dev/rst1";
char DEV_4[] = "/dev/rst4";
char DEV_5[] = "/dev/rst5";
char DEV_7[] = "/dev/rst7";
char DEV_8[] = "/dev/rst8";
#endif

static int
check_sum(char *hd, size_t hdlen, char *bl, size_t bllen, int quiet)
{
	u_long hdck, blck;

	hdck = asc_ul(hd, hdlen, OCT);
	blck = tar_chksm(bl, bllen);

	if (hdck != blck) {
		if (!quiet)
			tty_warn(0, "Header checksum %lo does not match %lo",
			    hdck, blck);
		return(-1);
	}
	return(0);
}


/*
 * tar_endwr()
 *	add the tar trailer of two null blocks
 * Return:
 *	0 if ok, -1 otherwise (what wr_skip returns)
 */

int
tar_endwr(void)
{
	return(wr_skip((off_t)(NULLCNT * BLKMULT)));
}

/*
 * tar_endrd()
 *	no cleanup needed here, just return size of trailer (for append)
 * Return:
 *	size of trailer BLKMULT
 */

off_t
tar_endrd(void)
{
	return((off_t)((gnu_short_trailer ? 1 : NULLCNT) * BLKMULT));
}

/*
 * tar_trail()
 *	Called to determine if a header block is a valid trailer. We are passed
 *	the block, the in_sync flag (which tells us we are in resync mode;
 *	looking for a valid header), and cnt (which starts at zero) which is
 *	used to count the number of empty blocks we have seen so far.
 * Return:
 *	0 if a valid trailer, -1 if not a valid trailer, or 1 if the block
 *	could never contain a header.
 */

int
tar_trail(char *buf, int in_resync, int *cnt)
{
	int i;

	gnu_short_trailer = 0;
	/*
	 * look for all zero, trailer is two consecutive blocks of zero
	 */
	for (i = 0; i < BLKMULT; ++i) {
		if (buf[i] != '\0')
			break;
	}

	/*
	 * if not all zero it is not a trailer, but MIGHT be a header.
	 */
	if (i != BLKMULT)
		return(-1);

	/*
	 * When given a zero block, we must be careful!
	 * If we are not in resync mode, check for the trailer. Have to watch
	 * out that we do not mis-identify file data as the trailer, so we do
	 * NOT try to id a trailer during resync mode. During resync mode we
	 * might as well throw this block out since a valid header can NEVER be
	 * a block of all 0 (we must have a valid file name).
	 */
	if (!in_resync) {
		++*cnt;
		/*
		 * old GNU tar (up through 1.13) only writes one block of
		 * trailers, so we pretend we got another
		 */
		if (is_gnutar) {
			gnu_short_trailer = 1;
			++*cnt;
		}
		if (*cnt >= NULLCNT)
			return(0);
	}
	return(1);
}

/*
 * ul_oct()
 *	convert an unsigned long to an octal string. many oddball field
 *	termination characters are used by the various versions of tar in the
 *	different fields. term selects which kind to use. str is '0' padded
 *	at the front to len. we are unable to use only one format as many old
 *	tar readers are very cranky about this.
 * Return:
 *	0 if the number fit into the string, -1 otherwise
 */

static int
ul_oct(u_long val, char *str, int len, int term)
{
	char *pt;

	/*
	 * term selects the appropriate character(s) for the end of the string
	 */
	pt = str + len - 1;
	switch(term) {
	case 3:
		*pt-- = '\0';
		break;
	case 2:
		*pt-- = ' ';
		*pt-- = '\0';
		break;
	case 1:
		*pt-- = ' ';
		break;
	case 0:
	default:
		*pt-- = '\0';
		*pt-- = ' ';
		break;
	}

	/*
	 * convert and blank pad if there is space
	 */
	while (pt >= str) {
		*pt-- = '0' + (char)(val & 0x7);
		if ((val = val >> 3) == (u_long)0)
			break;
	}

	while (pt >= str)
		*pt-- = '0';
	if (val != (u_long)0)
		return(-1);
	return(0);
}

#if !defined(NET2_STAT) && !defined(_LP64)
/*
 * ull_oct()
 *	convert an unsigned long long to an octal string. one of many oddball
 *	field termination characters are used by the various versions of tar
 *	in the different fields. term selects which kind to use. str is '0'
 *	padded at the front to len. we are unable to use only one format as
 *	many old tar readers are very cranky about this.
 * Return:
 *	0 if the number fit into the string, -1 otherwise
 */

static int
ull_oct(unsigned long long val, char *str, int len, int term)
{
	char *pt;

	/*
	 * term selects the appropriate character(s) for the end of the string
	 */
	pt = str + len - 1;
	switch(term) {
	case 3:
		*pt-- = '\0';
		break;
	case 2:
		*pt-- = ' ';
		*pt-- = '\0';
		break;
	case 1:
		*pt-- = ' ';
		break;
	case 0:
	default:
		*pt-- = '\0';
		*pt-- = ' ';
		break;
	}

	/*
	 * convert and blank pad if there is space
	 */
	while (pt >= str) {
		*pt-- = '0' + (char)(val & 0x7);
		if ((val = val >> 3) == 0)
			break;
	}

	while (pt >= str)
		*pt-- = '0';
	if (val != (unsigned long long)0)
		return(-1);
	return(0);
}
#endif

/*
 * tar_chksm()
 *	calculate the checksum for a tar block counting the checksum field as
 *	all blanks (BLNKSUM is that value pre-calculated, the sum of 8 blanks).
 *	NOTE: we use len to short circuit summing 0's on write since we ALWAYS
 *	pad headers with 0.
 * Return:
 *	unsigned long checksum
 */

static u_long
tar_chksm(char *blk, int len)
{
	char *stop;
	char *pt;
	u_long chksm = BLNKSUM;	/* initial value is checksum field sum */

	/*
	 * add the part of the block before the checksum field
	 */
	pt = blk;
	stop = blk + CHK_OFFSET;
	while (pt < stop)
		chksm += (u_long)(*pt++ & 0xff);
	/*
	 * move past the checksum field and keep going, spec counts the
	 * checksum field as the sum of 8 blanks (which is pre-computed as
	 * BLNKSUM).
	 * ASSUMED: len is greater than CHK_OFFSET. (len is where our 0 padding
	 * starts, no point in summing zero's)
	 */
	pt += CHK_LEN;
	stop = blk + len;
	while (pt < stop)
		chksm += (u_long)(*pt++ & 0xff);
	return(chksm);
}

/*
 * Routines for old BSD style tar (also made portable to sysV tar)
 */

/*
 * tar_id()
 *	determine if a block given to us is a valid tar header (and not a USTAR
 *	header). We have to be on the lookout for those pesky blocks of	all
 *	zero's.
 * Return:
 *	0 if a tar header, -1 otherwise
 */

int
tar_id(char *blk, int size)
{
	HD_TAR *hd;
	HD_USTAR *uhd;

	if (size < BLKMULT)
		return(-1);
	hd = (HD_TAR *)blk;
	uhd = (HD_USTAR *)blk;

	/*
	 * check for block of zero's first, a simple and fast test, then make
	 * sure this is not a ustar header by looking for the ustar magic
	 * cookie. We should use TMAGLEN, but some USTAR archive programs are
	 * wrong and create archives missing the \0. Last we check the
	 * checksum. If this is ok we have to assume it is a valid header.
	 */
	if (hd->name[0] == '\0')
		return(-1);
	if (strncmp(uhd->magic, TMAGIC, TMAGLEN - 1) == 0)
		return(-1);
	return check_sum(hd->chksum, sizeof(hd->chksum), blk, BLKMULT, 1);
}

/*
 * tar_opt()
 *	handle tar format specific -o options
 * Return:
 *	0 if ok -1 otherwise
 */

int
tar_opt(void)
{
	OPLIST *opt;

	while ((opt = opt_next()) != NULL) {
		if (strcmp(opt->name, TAR_OPTION) ||
		    strcmp(opt->value, TAR_NODIR)) {
			tty_warn(1,
			    "Unknown tar format -o option/value pair %s=%s",
			    opt->name, opt->value);
			tty_warn(1,
			    "%s=%s is the only supported tar format option",
			    TAR_OPTION, TAR_NODIR);
			return(-1);
		}

		/*
		 * we only support one option, and only when writing
		 */
		if ((act != APPND) && (act != ARCHIVE)) {
			tty_warn(1, "%s=%s is only supported when writing.",
			    opt->name, opt->value);
			return(-1);
		}
		tar_nodir = 1;
	}
	return(0);
}


/*
 * tar_rd()
 *	extract the values out of block already determined to be a tar header.
 *	store the values in the ARCHD parameter.
 * Return:
 *	0
 */

int
tar_rd(ARCHD *arcn, char *buf)
{
	HD_TAR *hd;
	char *pt;

	/*
	 * we only get proper sized buffers passed to us
	 */
	if (tar_id(buf, BLKMULT) < 0)
		return(-1);
	memset(arcn, 0, sizeof(*arcn));
	arcn->org_name = arcn->name;
	arcn->pat = NULL;
	arcn->sb.st_nlink = 1;

	/*
	 * copy out the name and values in the stat buffer
	 */
	hd = (HD_TAR *)buf;
	if (hd->linkflag != LONGLINKTYPE && hd->linkflag != LONGNAMETYPE) {
		arcn->nlen = expandname(arcn->name, sizeof(arcn->name),
		    &gnu_name_string, &gnu_name_length, hd->name,
		    sizeof(hd->name));
		arcn->ln_nlen = expandname(arcn->ln_name, sizeof(arcn->ln_name),
		    &gnu_link_string, &gnu_link_length, hd->linkname,
		    sizeof(hd->linkname));
	}
	arcn->sb.st_mode = (mode_t)(asc_ul(hd->mode,sizeof(hd->mode),OCT) &
	    0xfff);
	arcn->sb.st_uid = (uid_t)asc_ul(hd->uid, sizeof(hd->uid), OCT);
	arcn->sb.st_gid = (gid_t)asc_ul(hd->gid, sizeof(hd->gid), OCT);
	arcn->sb.st_size = (off_t)ASC_OFFT(hd->size, sizeof(hd->size), OCT);
	arcn->sb.st_mtime = (time_t)asc_ul(hd->mtime, sizeof(hd->mtime), OCT);
	arcn->sb.st_ctime = arcn->sb.st_atime = arcn->sb.st_mtime;

	/*
	 * have to look at the last character, it may be a '/' and that is used
	 * to encode this as a directory
	 */
	pt = &(arcn->name[arcn->nlen - 1]);
	arcn->pad = 0;
	arcn->skip = 0;
	switch(hd->linkflag) {
	case SYMTYPE:
		/*
		 * symbolic link, need to get the link name and set the type in
		 * the st_mode so -v printing will look correct.
		 */
		arcn->type = PAX_SLK;
		arcn->sb.st_mode |= S_IFLNK;
		break;
	case LNKTYPE:
		/*
		 * hard link, need to get the link name, set the type in the
		 * st_mode and st_nlink so -v printing will look better.
		 */
		arcn->type = PAX_HLK;
		arcn->sb.st_nlink = 2;

		/*
		 * no idea of what type this thing really points at, but
		 * we set something for printing only.
		 */
		arcn->sb.st_mode |= S_IFREG;
		break;
	case LONGLINKTYPE:
	case LONGNAMETYPE:
		/*
		 * GNU long link/file; we tag these here and let the
		 * pax internals deal with it -- too ugly otherwise.
		 */
		if (hd->linkflag != LONGLINKTYPE)
			arcn->type = PAX_GLF;
		else
			arcn->type = PAX_GLL;
		arcn->pad = TAR_PAD(arcn->sb.st_size);
		arcn->skip = arcn->sb.st_size;
		break;
	case AREGTYPE:
	case REGTYPE:
	case DIRTYPE:	/* see below */
	default:
		/*
		 * If we have a trailing / this is a directory and NOT a file.
		 * Note: V7 tar doesn't actually have DIRTYPE, but it was
		 * reported that V7 archives using USTAR directories do exist.
		 */
		if (*pt == '/' || hd->linkflag == DIRTYPE) {
			/*
			 * it is a directory, set the mode for -v printing
			 */
			arcn->type = PAX_DIR;
			arcn->sb.st_mode |= S_IFDIR;
			arcn->sb.st_nlink = 2;
		} else {
			/*
			 * have a file that will be followed by data. Set the
			 * skip value to the size field and calculate the size
			 * of the padding.
			 */
			arcn->type = PAX_REG;
			arcn->sb.st_mode |= S_IFREG;
			arcn->pad = TAR_PAD(arcn->sb.st_size);
			arcn->skip = arcn->sb.st_size;
		}
		break;
	}

	/*
	 * strip off any trailing slash.
	 */
	if (*pt == '/') {
		*pt = '\0';
		--arcn->nlen;
	}
	return(0);
}

/*
 * tar_wr()
 *	write a tar header for the file specified in the ARCHD to the archive.
 *	Have to check for file types that cannot be stored and file names that
 *	are too long. Be careful of the term (last arg) to ul_oct, each field
 *	of tar has it own spec for the termination character(s).
 *	ASSUMED: space after header in header block is zero filled
 * Return:
 *	0 if file has data to be written after the header, 1 if file has NO
 *	data to write after the header, -1 if archive write failed
 */

int
tar_wr(ARCHD *arcn)
{
	HD_TAR *hd;
	int len;
	char hdblk[sizeof(HD_TAR)];

	/*
	 * check for those file system types which tar cannot store
	 */
	switch(arcn->type) {
	case PAX_DIR:
		/*
		 * user asked that dirs not be written to the archive
		 */
		if (tar_nodir)
			return(1);
		break;
	case PAX_CHR:
		tty_warn(1, "Tar cannot archive a character device %s",
		    arcn->org_name);
		return(1);
	case PAX_BLK:
		tty_warn(1,
		    "Tar cannot archive a block device %s", arcn->org_name);
		return(1);
	case PAX_SCK:
		tty_warn(1, "Tar cannot archive a socket %s", arcn->org_name);
		return(1);
	case PAX_FIF:
		tty_warn(1, "Tar cannot archive a fifo %s", arcn->org_name);
		return(1);
	case PAX_SLK:
	case PAX_HLK:
	case PAX_HRG:
		if (arcn->ln_nlen > sizeof(hd->linkname)) {
			tty_warn(1,"Link name too long for tar %s",
			    arcn->ln_name);
			return(1);
		}
		break;
	case PAX_REG:
	case PAX_CTG:
	default:
		break;
	}

	/*
	 * check file name len, remember extra char for dirs (the / at the end)
	 */
	len = arcn->nlen;
	if (arcn->type == PAX_DIR)
		++len;
	if (len >= sizeof(hd->name)) {
		tty_warn(1, "File name too long for tar %s", arcn->name);
		return(1);
	}

	/*
	 * copy the data out of the ARCHD into the tar header based on the type
	 * of the file. Remember many tar readers want the unused fields to be
	 * padded with zero. We set the linkflag field (type), the linkname
	 * (or zero if not used),the size, and set the padding (if any) to be
	 * added after the file data (0 for all other types, as they only have
	 * a header)
	 */
	memset(hdblk, 0, sizeof(hdblk));
	hd = (HD_TAR *)hdblk;
	strlcpy(hd->name, arcn->name, sizeof(hd->name));
	arcn->pad = 0;

	if (arcn->type == PAX_DIR) {
		/*
		 * directories are the same as files, except have a filename
		 * that ends with a /, we add the slash here. No data follows,
		 * dirs, so no pad.
		 */
		hd->linkflag = AREGTYPE;
		hd->name[len-1] = '/';
		if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 1))
			goto out;
	} else if (arcn->type == PAX_SLK) {
		/*
		 * no data follows this file, so no pad
		 */
		hd->linkflag = SYMTYPE;
		strlcpy(hd->linkname, arcn->ln_name, sizeof(hd->linkname));
		if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 1))
			goto out;
	} else if ((arcn->type == PAX_HLK) || (arcn->type == PAX_HRG)) {
		/*
		 * no data follows this file, so no pad
		 */
		hd->linkflag = LNKTYPE;
		strlcpy(hd->linkname, arcn->ln_name, sizeof(hd->linkname));
		if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 1))
			goto out;
	} else {
		/*
		 * data follows this file, so set the pad
		 */
		hd->linkflag = AREGTYPE;
		if (OFFT_OCT(arcn->sb.st_size, hd->size, sizeof(hd->size), 1)) {
			tty_warn(1,"File is too large for tar %s",
			    arcn->org_name);
			return(1);
		}
		arcn->pad = TAR_PAD(arcn->sb.st_size);
	}

	/*
	 * copy those fields that are independent of the type
	 */
	if (ul_oct((u_long)arcn->sb.st_mode, hd->mode, sizeof(hd->mode), 0) ||
	    ul_oct((u_long)arcn->sb.st_uid, hd->uid, sizeof(hd->uid), 0) ||
	    ul_oct((u_long)arcn->sb.st_gid, hd->gid, sizeof(hd->gid), 0) ||
	    ul_oct((u_long)arcn->sb.st_mtime, hd->mtime, sizeof(hd->mtime), 1))
		goto out;

	/*
	 * calculate and add the checksum, then write the header. A return of
	 * 0 tells the caller to now write the file data, 1 says no data needs
	 * to be written
	 */
	if (ul_oct(tar_chksm(hdblk, sizeof(HD_TAR)), hd->chksum,
	    sizeof(hd->chksum), 3))
		goto out;			/* XXX Something's wrong here
						 * because a zero-byte file can
						 * cause this to be done and
						 * yet the resulting warning
						 * seems incorrect */

	if (wr_rdbuf(hdblk, sizeof(HD_TAR)) < 0)
		return(-1);
	if (wr_skip((off_t)(BLKMULT - sizeof(HD_TAR))) < 0)
		return(-1);
	if ((arcn->type == PAX_CTG) || (arcn->type == PAX_REG))
		return(0);
	return(1);

    out:
	/*
	 * header field is out of range
	 */
	tty_warn(1, "Tar header field is too small for %s", arcn->org_name);
	return(1);
}

/*
 * Routines for POSIX ustar
 */

/*
 * ustar_strd()
 *	initialization for ustar read
 * Return:
 *	0 if ok, -1 otherwise
 */

int
ustar_strd(void)
{
	return(0);
}

/*
 * ustar_stwr()
 *	initialization for ustar write
 * Return:
 *	0 if ok, -1 otherwise
 */

int
ustar_stwr(void)
{
	return(0);
}

/*
 * ustar_id()
 *	determine if a block given to us is a valid ustar header. We have to
 *	be on the lookout for those pesky blocks of all zero's
 * Return:
 *	0 if a ustar header, -1 otherwise
 */

int
ustar_id(char *blk, int size)
{
	HD_USTAR *hd;

	if (size < BLKMULT)
		return(-1);
	hd = (HD_USTAR *)blk;

	/*
	 * check for block of zero's first, a simple and fast test then check
	 * ustar magic cookie. We should use TMAGLEN, but some USTAR archive
	 * programs are fouled up and create archives missing the \0. Last we
	 * check the checksum. If ok we have to assume it is a valid header.
	 */
	if (hd->name[0] == '\0')
		return(-1);
	if (strncmp(hd->magic, TMAGIC, TMAGLEN - 1) != 0)
		return(-1);
	/* This is GNU tar */
	if (strncmp(hd->magic, "ustar  ", 8) == 0 && !is_gnutar &&
	    !seen_gnu_warning) {
		seen_gnu_warning = 1;
		tty_warn(0,
		    "Trying to read GNU tar archive with extensions off");
	}
	return check_sum(hd->chksum, sizeof(hd->chksum), blk, BLKMULT, 0);
}

/*
 * ustar_rd()
 *	extract the values out of block already determined to be a ustar header.
 *	store the values in the ARCHD parameter.
 * Return:
 *	0
 */

int
ustar_rd(ARCHD *arcn, char *buf)
{
	HD_USTAR *hd;
	char *dest;
	int cnt;
	dev_t devmajor;
	dev_t devminor;

	/*
	 * we only get proper sized buffers
	 */
	if (ustar_id(buf, BLKMULT) < 0)
		return(-1);

	memset(arcn, 0, sizeof(*arcn));
	arcn->org_name = arcn->name;
	arcn->pat = NULL;
	arcn->sb.st_nlink = 1;
	hd = (HD_USTAR *)buf;

	/*
	 * see if the filename is split into two parts. if, so joint the parts.
	 * we copy the prefix first and add a / between the prefix and name.
	 */
	dest = arcn->name;
	if (*(hd->prefix) != '\0') {
		cnt = strlcpy(arcn->name, hd->prefix, sizeof(arcn->name));
		dest += cnt;
		*dest++ = '/';
		cnt++;
	} else {
		cnt = 0;
	}

	if (hd->typeflag != LONGLINKTYPE && hd->typeflag != LONGNAMETYPE) {
		arcn->nlen = expandname(dest, sizeof(arcn->name) - cnt,
		    &gnu_name_string, &gnu_name_length, hd->name,
		    sizeof(hd->name)) + cnt;
		arcn->ln_nlen = expandname(arcn->ln_name,
		    sizeof(arcn->ln_name), &gnu_link_string, &gnu_link_length,
		    hd->linkname, sizeof(hd->linkname));
	}

	/*
	 * follow the spec to the letter. we should only have mode bits, strip
	 * off all other crud we may be passed.
	 */
	arcn->sb.st_mode = (mode_t)(asc_ul(hd->mode, sizeof(hd->mode), OCT) &
	    0xfff);
	arcn->sb.st_size = (off_t)ASC_OFFT(hd->size, sizeof(hd->size), OCT);
	arcn->sb.st_mtime = (time_t)asc_ul(hd->mtime, sizeof(hd->mtime), OCT);
	arcn->sb.st_ctime = arcn->sb.st_atime = arcn->sb.st_mtime;

	/*
	 * If we can find the ascii names for gname and uname in the password
	 * and group files we will use the uid's and gid they bind. Otherwise
	 * we use the uid and gid values stored in the header. (This is what
	 * the posix spec wants).
	 */
	hd->gname[sizeof(hd->gname) - 1] = '\0';
	if (gid_from_group(hd->gname, &(arcn->sb.st_gid)) < 0)
		arcn->sb.st_gid = (gid_t)asc_ul(hd->gid, sizeof(hd->gid), OCT);
	hd->uname[sizeof(hd->uname) - 1] = '\0';
	if (uid_from_user(hd->uname, &(arcn->sb.st_uid)) < 0)
		arcn->sb.st_uid = (uid_t)asc_ul(hd->uid, sizeof(hd->uid), OCT);

	/*
	 * set the defaults, these may be changed depending on the file type
	 */
	arcn->pad = 0;
	arcn->skip = 0;
	arcn->sb.st_rdev = (dev_t)0;

	/*
	 * set the mode and PAX type according to the typeflag in the header
	 */
	switch(hd->typeflag) {
	case FIFOTYPE:
		arcn->type = PAX_FIF;
		arcn->sb.st_mode |= S_IFIFO;
		break;
	case DIRTYPE:
		arcn->type = PAX_DIR;
		arcn->sb.st_mode |= S_IFDIR;
		arcn->sb.st_nlink = 2;

		/*
		 * Some programs that create ustar archives append a '/'
		 * to the pathname for directories. This clearly violates
		 * ustar specs, but we will silently strip it off anyway.
		 */
		if (arcn->name[arcn->nlen - 1] == '/')
			arcn->name[--arcn->nlen] = '\0';
		break;
	case BLKTYPE:
	case CHRTYPE:
		/*
		 * this type requires the rdev field to be set.
		 */
		if (hd->typeflag == BLKTYPE) {
			arcn->type = PAX_BLK;
			arcn->sb.st_mode |= S_IFBLK;
		} else {
			arcn->type = PAX_CHR;
			arcn->sb.st_mode |= S_IFCHR;
		}
		devmajor = (dev_t)asc_ul(hd->devmajor,sizeof(hd->devmajor),OCT);
		devminor = (dev_t)asc_ul(hd->devminor,sizeof(hd->devminor),OCT);
		arcn->sb.st_rdev = TODEV(devmajor, devminor);
		break;
	case SYMTYPE:
	case LNKTYPE:
		if (hd->typeflag == SYMTYPE) {
			arcn->type = PAX_SLK;
			arcn->sb.st_mode |= S_IFLNK;
		} else {
			arcn->type = PAX_HLK;
			/*
			 * so printing looks better
			 */
			arcn->sb.st_mode |= S_IFREG;
			arcn->sb.st_nlink = 2;
		}
		break;
	case LONGLINKTYPE:
	case LONGNAMETYPE:
		if (is_gnutar) {
			/*
			 * GNU long link/file; we tag these here and let the
			 * pax internals deal with it -- too ugly otherwise.
			 */
			if (hd->typeflag != LONGLINKTYPE)
				arcn->type = PAX_GLF;
			else
				arcn->type = PAX_GLL;
			arcn->pad = TAR_PAD(arcn->sb.st_size);
			arcn->skip = arcn->sb.st_size;
		} else {
			tty_warn(1, "GNU Long %s found in posix ustar archive.",
			    hd->typeflag == LONGLINKTYPE ? "Link" : "File");
		}
		break;
	case CONTTYPE:
	case AREGTYPE:
	case REGTYPE:
	default:
		/*
		 * these types have file data that follows. Set the skip and
		 * pad fields.
		 */
		arcn->type = PAX_REG;
		arcn->pad = TAR_PAD(arcn->sb.st_size);
		arcn->skip = arcn->sb.st_size;
		arcn->sb.st_mode |= S_IFREG;
		break;
	}
	return(0);
}

static int
expandname(char *buf, size_t len, char **gnu_name, size_t *gnu_length,
    const char *name, size_t nlen)
{
	if (*gnu_name) {
		len = strlcpy(buf, *gnu_name, len);
		free(*gnu_name);
		*gnu_name = NULL;
		*gnu_length = 0;
	} else {
		if (len > ++nlen)
			len = nlen;
		len = strlcpy(buf, name, len);
	}
	return len;
}

static void
longlink(ARCHD *arcn, int type)
{
	ARCHD larc;

	(void)memset(&larc, 0, sizeof(larc));

	larc.type = type;
	larc.nlen = strlcpy(larc.name, LONG_LINK, sizeof(larc.name));

	switch (type) {
	case PAX_GLL:
		gnu_hack_string = arcn->ln_name;
		gnu_hack_len = arcn->ln_nlen + 1;
		break;
	case PAX_GLF:
		gnu_hack_string = arcn->name;
		gnu_hack_len = arcn->nlen + 1;
		break;
	default:
		errx(1, "Invalid type in GNU longlink %d\n", type);
	}

	/*
	 * We need a longlink now.
	 */
	ustar_wr(&larc);
}

/*
 * ustar_wr()
 *	write a ustar header for the file specified in the ARCHD to the archive
 *	Have to check for file types that cannot be stored and file names that
 *	are too long. Be careful of the term (last arg) to ul_oct, we only use
 *	'\0' for the termination character (this is different than picky tar)
 *	ASSUMED: space after header in header block is zero filled
 * Return:
 *	0 if file has data to be written after the header, 1 if file has NO
 *	data to write after the header, -1 if archive write failed
 */

static int
size_err(const char *what, ARCHD *arcn)
{
	/*
	 * header field is out of range
	 */
	tty_warn(1, "Ustar %s header field is too small for %s",
		what, arcn->org_name);
	return 1;
}

int
ustar_wr(ARCHD *arcn)
{
	HD_USTAR *hd;
	char *pt;
	char hdblk[sizeof(HD_USTAR)];
	const char *user, *group;

	switch (arcn->type) {
	case PAX_SCK:
		/*
		 * check for those file system types ustar cannot store
		 */
		if (!is_gnutar)
			tty_warn(1, "Ustar cannot archive a socket %s",
			    arcn->org_name);
		return(1);

	case PAX_SLK:
	case PAX_HLK:
	case PAX_HRG:
		/*
		 * check the length of the linkname
		 */
		if (arcn->ln_nlen >= sizeof(hd->linkname)) {
			if (is_gnutar) {
				longlink(arcn, PAX_GLL);
			} else {
				tty_warn(1, "Link name too long for ustar %s",
				    arcn->ln_name);
				return(1);
			}
		}
		break;
	default:
		break;
	}

	/*
	 * split the path name into prefix and name fields (if needed). if
	 * pt != arcn->name, the name has to be split
	 */
	if ((pt = name_split(arcn->name, arcn->nlen)) == NULL) {
		if (is_gnutar) {
			longlink(arcn, PAX_GLF);
			pt = arcn->name;
		} else {
			tty_warn(1, "File name too long for ustar %s",
			    arcn->name);
			return(1);
		}
	}

	/*
	 * zero out the header so we don't have to worry about zero fill below
	 */
	memset(hdblk, 0, sizeof(hdblk));
	hd = (HD_USTAR *)hdblk;
	arcn->pad = 0L;

	/*
	 * split the name, or zero out the prefix
	 */
	if (pt != arcn->name) {
		/*
		 * name was split, pt points at the / where the split is to
		 * occur, we remove the / and copy the first part to the prefix
		 */
		*pt = '\0';
		strlcpy(hd->prefix, arcn->name, sizeof(hd->prefix));
		*pt++ = '/';
	}

	/*
	 * copy the name part. this may be the whole path or the part after
	 * the prefix
	 */
	strlcpy(hd->name, pt, sizeof(hd->name));

	/*
	 * set the fields in the header that are type dependent
	 */
	switch(arcn->type) {
	case PAX_DIR:
		hd->typeflag = DIRTYPE;
		if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 3))
			return size_err("DIRTYPE", arcn);
		break;
	case PAX_CHR:
	case PAX_BLK:
		if (arcn->type == PAX_CHR)
			hd->typeflag = CHRTYPE;
		else
			hd->typeflag = BLKTYPE;
		if (ul_oct((u_long)MAJOR(arcn->sb.st_rdev), hd->devmajor,
		   sizeof(hd->devmajor), 3) ||
		   ul_oct((u_long)MINOR(arcn->sb.st_rdev), hd->devminor,
		   sizeof(hd->devminor), 3) ||
		   ul_oct((u_long)0L, hd->size, sizeof(hd->size), 3))
			return size_err("DEVTYPE", arcn);
		break;
	case PAX_FIF:
		hd->typeflag = FIFOTYPE;
		if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 3))
			return size_err("FIFOTYPE", arcn);
		break;
	case PAX_GLL:
	case PAX_SLK:
	case PAX_HLK:
	case PAX_HRG:
		if (arcn->type == PAX_SLK)
			hd->typeflag = SYMTYPE;
		else if (arcn->type == PAX_GLL)
			hd->typeflag = LONGLINKTYPE;
		else
			hd->typeflag = LNKTYPE;
		strlcpy(hd->linkname, arcn->ln_name, sizeof(hd->linkname));
		if (ul_oct((u_long)gnu_hack_len, hd->size,
		    sizeof(hd->size), 3))
			return size_err("LINKTYPE", arcn);
		break;
	case PAX_GLF:
	case PAX_REG:
	case PAX_CTG:
	default:
		/*
		 * file data with this type, set the padding
		 */
		if (arcn->type == PAX_GLF) {
			hd->typeflag = LONGNAMETYPE;
			arcn->pad = TAR_PAD(gnu_hack_len);
			if (OFFT_OCT((u_long)gnu_hack_len, hd->size,
			    sizeof(hd->size), 3)) {
				tty_warn(1,"File is too long for ustar %s",
				    arcn->org_name);
				return(1);
			}
		} else {
			if (arcn->type == PAX_CTG)
				hd->typeflag = CONTTYPE;
			else
				hd->typeflag = REGTYPE;
			arcn->pad = TAR_PAD(arcn->sb.st_size);
			if (OFFT_OCT(arcn->sb.st_size, hd->size,
			    sizeof(hd->size), 3)) {
				tty_warn(1,"File is too long for ustar %s",
				    arcn->org_name);
				return(1);
			}
		}
		break;
	}

	strncpy(hd->magic, TMAGIC, TMAGLEN);
	if (is_gnutar)
		hd->magic[TMAGLEN - 1] = hd->magic[TMAGLEN] = ' ';
	else
		strncpy(hd->version, TVERSION, TVERSLEN);

	/*
	 * set the remaining fields. Some versions want all 16 bits of mode
	 * we better humor them (they really do not meet spec though)....
	 */
	if (ul_oct((u_long)arcn->sb.st_mode, hd->mode, sizeof(hd->mode), 3))
		return size_err("MODE", arcn);
	if (ul_oct((u_long)arcn->sb.st_uid, hd->uid, sizeof(hd->uid), 3))
		return size_err("UID", arcn);
	if (ul_oct((u_long)arcn->sb.st_gid, hd->gid, sizeof(hd->gid), 3))
		return size_err("GID", arcn);
	if (ul_oct((u_long)arcn->sb.st_mtime,hd->mtime,sizeof(hd->mtime),3))
		return size_err("MTIME", arcn);
	user = user_from_uid(arcn->sb.st_uid, 1);
	group = group_from_gid(arcn->sb.st_gid, 1);
	strncpy(hd->uname, user ? user : "", sizeof(hd->uname));
	strncpy(hd->gname, group ? group : "", sizeof(hd->gname));

	/*
	 * calculate and store the checksum write the header to the archive
	 * return 0 tells the caller to now write the file data, 1 says no data
	 * needs to be written
	 */
	if (ul_oct(tar_chksm(hdblk, sizeof(HD_USTAR)), hd->chksum,
	   sizeof(hd->chksum), 3))
		return size_err("CHKSUM", arcn);
	if (wr_rdbuf(hdblk, sizeof(HD_USTAR)) < 0)
		return(-1);
	if (wr_skip((off_t)(BLKMULT - sizeof(HD_USTAR))) < 0)
		return(-1);
	if (gnu_hack_string) {
		int res = wr_rdbuf(gnu_hack_string, gnu_hack_len);
		int pad = gnu_hack_len;
		gnu_hack_string = NULL;
		gnu_hack_len = 0;
		if (res < 0)
			return(-1);
		if (wr_skip((off_t)(BLKMULT - (pad % BLKMULT))) < 0)
			return(-1);
	}
	if ((arcn->type == PAX_CTG) || (arcn->type == PAX_REG))
		return(0);
	return(1);
}

/*
 * name_split()
 *	see if the name has to be split for storage in a ustar header. We try
 *	to fit the entire name in the name field without splitting if we can.
 *	The split point is always at a /
 * Return
 *	character pointer to split point (always the / that is to be removed
 *	if the split is not needed, the points is set to the start of the file
 *	name (it would violate the spec to split there). A NULL is returned if
 *	the file name is too long
 */

static char *
name_split(char *name, int len)
{
	char *start;

	/*
	 * check to see if the file name is small enough to fit in the name
	 * field. if so just return a pointer to the name.
	 */
	if (len < TNMSZ)
		return(name);
	/*
	 * GNU tar does not honor the prefix+name mode if the magic
	 * is not "ustar\0". So in GNU tar compatibility mode, we don't
	 * split the filename into prefix+name because we are setting
	 * the magic to "ustar " as GNU tar does. This of course will
	 * end up creating a LongLink record in cases where it does not
	 * really need do, but we are behaving like GNU tar after all.
	 */
	if (is_gnutar || len > (TPFSZ + TNMSZ))
		return(NULL);

	/*
	 * we start looking at the biggest sized piece that fits in the name
	 * field. We walk forward looking for a slash to split at. The idea is
	 * to find the biggest piece to fit in the name field (or the smallest
	 * prefix we can find) (the -1 is correct the biggest piece would
	 * include the slash between the two parts that gets thrown away)
	 */
	start = name + len - TNMSZ;
	while ((*start != '\0') && (*start != '/'))
		++start;

	/*
	 * if we hit the end of the string, this name cannot be split, so we
	 * cannot store this file.
	 */
	if (*start == '\0')
		return(NULL);
	len = start - name;

	/*
	 * NOTE: /str where the length of str == TNMSZ cannot be stored under
	 * the p1003.1-1990 spec for ustar. We could force a prefix of / and
	 * the file would then expand on extract to //str. The len == 0 below
	 * makes this special case follow the spec to the letter.
	 */
	if ((len >= TPFSZ) || (len == 0))
		return(NULL);

	/*
	 * ok have a split point, return it to the caller
	 */
	return(start);
}

/*
 * convert a glob into a RE, and add it to the list.  we convert to
 * four different RE's (because we're using BRE's and can't use |
 * alternation :-() with this padding:
 *	.*\/ and $
 *	.*\/ and \/.*
 *	^ and $
 *	^ and \/.*
 */
static int
tar_gnutar_exclude_one(const char *line, size_t len)
{
	/* 2 * buffer len + nul */
	char sbuf[MAXPATHLEN * 2 + 1];
	/* + / + // + .*""/\/ + \/.* */
	char rabuf[MAXPATHLEN * 2 + 1 + 1 + 2 + 4 + 4];
	int i, j;

	if (line[len - 1] == '\n')
		len--;
	strncpy(sbuf, ".*" "\\/", j = 4);
	for (i = 0; i < len; i++) {
		/*
		 * convert glob to regexp, escaping everything
		 */
		if (line[i] == '*')
			sbuf[j++] = '.';
		else if (line[i] == '?') {
			sbuf[j++] = '.';
			continue;
		} else if (!isalnum((unsigned char)line[i]) &&
		    !isblank((unsigned char)line[i]))
			sbuf[j++] = '\\';
		sbuf[j++] = line[i];
	}
	sbuf[j] = '\0';
	/* don't need the .*\/ ones if we start with /, i guess */
	if (line[0] != '/') {
		(void)snprintf(rabuf, sizeof rabuf, "/.*\\/%s$//", sbuf);
		if (rep_add(rabuf) < 0)
			return (-1);
		(void)snprintf(rabuf, sizeof rabuf, "/.*\\/%s\\/.*//", sbuf);
		if (rep_add(rabuf) < 0)
			return (-1);
	}

	(void)snprintf(rabuf, sizeof rabuf, "/^%s$//", sbuf);
	if (rep_add(rabuf) < 0)
		return (-1);
	(void)snprintf(rabuf, sizeof rabuf, "/^%s\\/.*//", sbuf);
	if (rep_add(rabuf) < 0)
		return (-1);

	return (0);
}

/*
 * deal with GNU tar -X/--exclude-from & --exclude switchs.  basically,
 * we go through each line of the file, building a string from the "glob"
 * lines in the file into RE lines, of the form `/^RE$//', which we pass
 * to rep_add(), which will add a empty replacement (exclusion), for the
 * named files.
 */
int
tar_gnutar_minus_minus_exclude(path)
	const char *path;
{
	size_t	len = strlen(path);

	if (len > MAXPATHLEN)
		tty_warn(0, "pathname too long: %s", path);

	return (tar_gnutar_exclude_one(path, len));
}

int
tar_gnutar_X_compat(path)
	const char *path;
{
	char *line;
	FILE *fp;
	int lineno = 0;
	size_t len;

	fp = fopen(path, "r");
	if (fp == NULL) {
		tty_warn(1, "cannot open %s: %s", path,
		    strerror(errno));
		return(-1);
	}

	while ((line = fgetln(fp, &len))) {
		lineno++;
		if (len > MAXPATHLEN) {
			tty_warn(0, "pathname too long, line %d of %s",
			    lineno, path);
		}
		if (tar_gnutar_exclude_one(line, len))
			return (-1);
	}
	return (0);
}