mkfs: symlink support

[minix.git] / bin / pax / tar.c

/*      $NetBSD: tar.c,v 1.70 2012/08/09 08:09:22 christos 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 1.70 2012/08/09 08:09:22 christos 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 uint32_t tar_chksm(char *, int);
static char *name_split(char *, int);
static int u32_oct(uintmax_t, char *, int, int);
static int umax_oct(uintmax_t, char *, int, int);
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-of-volume
                                         * 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)
{
        uint32_t hdck, blck;

        hdck = asc_u32(hd, hdlen, OCT);
        blck = tar_chksm(bl, bllen);

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

/*
 * u32_oct()
 *      convert an uintmax_t 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
u32_oct(uintmax_t val, char *str, int len, int term)
{
        char *pt;
        uint64_t p;

        p = val & TOP_HALF;
        if (p && p != TOP_HALF)
                return -1;

        val &= BOTTOM_HALF;

        /*
         * 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 != 0)
                return -1;
        return 0;
}

/*
 * umax_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
umax_oct(uintmax_t 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 != 0)
                return -1;
        return 0;
}

/*
 * 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 uint32_t
tar_chksm(char *blk, int len)
{
        char *stop;
        char *pt;
        uint32_t 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 += (uint32_t)(*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 += (uint32_t)(*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;
        static int is_ustar = -1;

        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) {
                if (is_ustar == -1) {
                        is_ustar = 1;
                        return -1;
                } else
                        tty_warn(0,
                            "Busted tar archive: has both ustar and old tar "
                            "records");
        } else
                is_ustar = 0; 
        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_u32(hd->mode,sizeof(hd->mode),OCT) &
            0xfff);
        arcn->sb.st_uid = (uid_t)asc_u32(hd->uid, sizeof(hd->uid), OCT);
        arcn->sb.st_gid = (gid_t)asc_u32(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)(int32_t)asc_u32(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 u32_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 > (int)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 >= (int)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 (u32_oct((uintmax_t)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 (u32_oct((uintmax_t)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 (u32_oct((uintmax_t)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 (u32_oct((uintmax_t)arcn->sb.st_mode, hd->mode, sizeof(hd->mode), 0) ||
            u32_oct((uintmax_t)arcn->sb.st_uid, hd->uid, sizeof(hd->uid), 0) ||
            u32_oct((uintmax_t)arcn->sb.st_gid, hd->gid, sizeof(hd->gid), 0) ||
            u32_oct((uintmax_t)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 (u32_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 GNU extensions and end-of-volume checks 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_u32(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)(int32_t)asc_u32(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_u32(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_u32(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_u32(hd->devmajor,sizeof(hd->devmajor),OCT);
                devminor = (dev_t)asc_u32(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 u32_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 >= (int)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 (u32_oct((uintmax_t)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 (u32_oct((uintmax_t)MAJOR(arcn->sb.st_rdev), hd->devmajor,
                   sizeof(hd->devmajor), 3) ||
                   u32_oct((uintmax_t)MINOR(arcn->sb.st_rdev), hd->devminor,
                   sizeof(hd->devminor), 3) ||
                   u32_oct((uintmax_t)0L, hd->size, sizeof(hd->size), 3))
                        return size_err("DEVTYPE", arcn);
                break;
        case PAX_FIF:
                hd->typeflag = FIFOTYPE;
                if (u32_oct((uintmax_t)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 (u32_oct((uintmax_t)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((uint32_t)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->version[0] = ' ';
        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 (u32_oct((uintmax_t)arcn->sb.st_mode, hd->mode, sizeof(hd->mode), 3))
                return size_err("MODE", arcn);
        if (u32_oct((uintmax_t)arcn->sb.st_uid, hd->uid, sizeof(hd->uid), 3))
                return size_err("UID", arcn);
        if (u32_oct((uintmax_t)arcn->sb.st_gid, hd->gid, sizeof(hd->gid), 3))
                return size_err("GID", arcn);
        if (u32_oct((uintmax_t)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 (u32_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];
        size_t i;
        int j = 0;

        if (line[len - 1] == '\n')
                len--;
        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(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(const char *path)
{
        char *line;
        FILE *fp;
        int lineno = 0;
        size_t len;

        if (path[0] == '-' && path[1] == '\0')
                fp = stdin;
        else {
                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;
        }
        if (fp != stdin)
                fclose(fp);
        return 0;
}