busybox

/* vi: set sw=4 ts=4: */

/*

 * Licensed under GPLv2 or later, see file LICENSE in this source tree.

 *

 * FIXME:

 *    In privileged mode if uname and gname map to a uid and gid then use the

 *    mapped value instead of the uid/gid values in tar header

 *

 * References:

 *    GNU tar and star man pages,

 *    Opengroup's ustar interchange format,

 *    http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html

 */

#include "libbb.h"

#include "bb_archive.h"

​

typedef uint32_t aliased_uint32_t FIX_ALIASING;

typedef off_t    aliased_off_t    FIX_ALIASING;

​

/* NB: _DESTROYS_ str[len] character! */

static unsigned long long getOctal(char *str, int len)

{

    unsigned long long v;

    char *end;

    /* NB: leading spaces are allowed. Using strtoull to handle that.

     * The downside is that we accept e.g. "-123" too :(

     */

    str[len] = '\0';

    v = strtoull(str, &end, 8);

    /* std: "Each numeric field is terminated by one or more

     * <space> or NUL characters". We must support ' '! */

    if (*end != '\0' && *end != ' ') {

        int8_t first = str[0];

        if (!(first & 0x80))

            bb_error_msg_and_die("corrupted octal value in tar header");

        /*

         * GNU tar uses "base-256 encoding" for very large numbers.

         * Encoding is binary, with highest bit always set as a marker

         * and sign in next-highest bit:

         * 80 00 .. 00 - zero

         * bf ff .. ff - largest positive number

         * ff ff .. ff - minus 1

         * c0 00 .. 00 - smallest negative number

         *

         * Example of tar file with 8914993153 (0x213600001) byte file.

         * Field starts at offset 7c:

         * 00070  30 30 30 00 30 30 30 30  30 30 30 00 80 00 00 00  |000.0000000.....|

         * 00080  00 00 00 02 13 60 00 01  31 31 31 32 30 33 33 36  |.....`..11120336|

         *

         * NB: tarballs with NEGATIVE unix times encoded that way were seen!

         */

        /* Sign-extend 7bit 'first' to 64bit 'v' (that is, using 6th bit as sign): */

        first <<= 1;

        first >>= 1; /* now 7th bit = 6th bit */

        v = first;   /* sign-extend 8 bits to 64 */

        while (--len != 0)

            v = (v << 8) + (uint8_t) *++str;

    }

    return v;

}

#define GET_OCTAL(a) getOctal((a), sizeof(a))

​

#define TAR_EXTD (ENABLE_FEATURE_TAR_GNU_EXTENSIONS || ENABLE_FEATURE_TAR_SELINUX)