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Annotation of embedaddon/php/ext/fileinfo/libmagic/is_tar.c, revision 1.1.1.2

1.1       misho       1: /*
                      2:  * Copyright (c) Ian F. Darwin 1986-1995.
                      3:  * Software written by Ian F. Darwin and others;
                      4:  * maintained 1995-present by Christos Zoulas and others.
1.1.1.2 ! misho       5:  *
1.1       misho       6:  * Redistribution and use in source and binary forms, with or without
                      7:  * modification, are permitted provided that the following conditions
                      8:  * are met:
                      9:  * 1. Redistributions of source code must retain the above copyright
                     10:  *    notice immediately at the beginning of the file, without modification,
                     11:  *    this list of conditions, and the following disclaimer.
                     12:  * 2. Redistributions in binary form must reproduce the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer in the
                     14:  *    documentation and/or other materials provided with the distribution.
1.1.1.2 ! misho      15:  *
1.1       misho      16:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
                     17:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     18:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     19:  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
                     20:  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     21:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     22:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     23:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     24:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     25:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     26:  * SUCH DAMAGE.
                     27:  */
                     28: /*
                     29:  * is_tar() -- figure out whether file is a tar archive.
                     30:  *
                     31:  * Stolen (by the author!) from the public domain tar program:
                     32:  * Public Domain version written 26 Aug 1985 John Gilmore (ihnp4!hoptoad!gnu).
                     33:  *
                     34:  * @(#)list.c 1.18 9/23/86 Public Domain - gnu
                     35:  *
                     36:  * Comments changed and some code/comments reformatted
                     37:  * for file command by Ian Darwin.
                     38:  */
                     39: 
                     40: #include "file.h"
                     41: 
                     42: #ifndef lint
1.1.1.2 ! misho      43: FILE_RCSID("@(#)$File: is_tar.c,v 1.37 2010/11/30 14:58:53 rrt Exp $")
1.1       misho      44: #endif
                     45: 
                     46: #include "magic.h"
                     47: #include <string.h>
                     48: #include <ctype.h>
                     49: #include "tar.h"
                     50: 
                     51: #define        isodigit(c)     ( ((c) >= '0') && ((c) <= '7') )
                     52: 
                     53: private int is_tar(const unsigned char *, size_t);
                     54: private int from_oct(int, const char *);       /* Decode octal number */
                     55: 
                     56: static const char tartype[][32] = {
                     57:        "tar archive",
                     58:        "POSIX tar archive",
                     59:        "POSIX tar archive (GNU)",
                     60: };
                     61: 
                     62: protected int
                     63: file_is_tar(struct magic_set *ms, const unsigned char *buf, size_t nbytes)
                     64: {
                     65:        /*
                     66:         * Do the tar test first, because if the first file in the tar
                     67:         * archive starts with a dot, we can confuse it with an nroff file.
                     68:         */
                     69:        int tar;
                     70:        int mime = ms->flags & MAGIC_MIME;
                     71: 
                     72:        if ((ms->flags & MAGIC_APPLE) != 0)
                     73:                return 0;
                     74: 
                     75:        tar = is_tar(buf, nbytes);
                     76:        if (tar < 1 || tar > 3)
                     77:                return 0;
                     78: 
                     79:        if (file_printf(ms, "%s", mime ? "application/x-tar" :
                     80:            tartype[tar - 1]) == -1)
                     81:                return -1;
                     82:        return 1;
                     83: }
                     84: 
                     85: /*
1.1.1.2 ! misho      86:  * Return
        !            87:  *     0 if the checksum is bad (i.e., probably not a tar archive),
1.1       misho      88:  *     1 for old UNIX tar file,
                     89:  *     2 for Unix Std (POSIX) tar file,
                     90:  *     3 for GNU tar file.
                     91:  */
                     92: private int
                     93: is_tar(const unsigned char *buf, size_t nbytes)
                     94: {
                     95:        const union record *header = (const union record *)(const void *)buf;
                     96:        int     i;
                     97:        int     sum, recsum;
1.1.1.2 ! misho      98:        const unsigned char     *p;
1.1       misho      99: 
                    100:        if (nbytes < sizeof(union record))
                    101:                return 0;
                    102: 
                    103:        recsum = from_oct(8,  header->header.chksum);
                    104: 
                    105:        sum = 0;
                    106:        p = header->charptr;
1.1.1.2 ! misho     107:        for (i = sizeof(union record); --i >= 0;)
        !           108:                sum += *p++;
1.1       misho     109: 
                    110:        /* Adjust checksum to count the "chksum" field as blanks. */
                    111:        for (i = sizeof(header->header.chksum); --i >= 0;)
1.1.1.2 ! misho     112:                sum -= header->header.chksum[i];
        !           113:        sum += ' ' * sizeof header->header.chksum;
1.1       misho     114: 
                    115:        if (sum != recsum)
                    116:                return 0;       /* Not a tar archive */
1.1.1.2 ! misho     117: 
        !           118:        if (strcmp(header->header.magic, GNUTMAGIC) == 0)
1.1       misho     119:                return 3;               /* GNU Unix Standard tar archive */
1.1.1.2 ! misho     120:        if (strcmp(header->header.magic, TMAGIC) == 0)
1.1       misho     121:                return 2;               /* Unix Standard tar archive */
                    122: 
                    123:        return 1;                       /* Old fashioned tar archive */
                    124: }
                    125: 
                    126: 
                    127: /*
                    128:  * Quick and dirty octal conversion.
                    129:  *
1.1.1.2 ! misho     130:  * Result is -1 if the field is invalid (all blank, or non-octal).
1.1       misho     131:  */
                    132: private int
                    133: from_oct(int digs, const char *where)
                    134: {
                    135:        int     value;
                    136: 
                    137:        while (isspace((unsigned char)*where)) {        /* Skip spaces */
                    138:                where++;
                    139:                if (--digs <= 0)
                    140:                        return -1;              /* All blank field */
                    141:        }
                    142:        value = 0;
1.1.1.2 ! misho     143:        while (digs > 0 && isodigit(*where)) {  /* Scan til non-octal */
1.1       misho     144:                value = (value << 3) | (*where++ - '0');
                    145:                --digs;
                    146:        }
                    147: 
                    148:        if (digs > 0 && *where && !isspace((unsigned char)*where))
1.1.1.2 ! misho     149:                return -1;                      /* Ended on non-(space/NUL) */
1.1       misho     150: 
                    151:        return value;
                    152: }