external/bsd/file/dist/src/is_tar.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * Copyright (c) Ian F. Darwin 1986-1995.
   5  * Software written by Ian F. Darwin and others;
   6  * maintained 1995-present by Christos Zoulas and others.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice immediately at the beginning of the file, without modification,
  13  *    this list of conditions, and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
  22  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  */
  30 /*
  31  * is_tar() -- figure out whether file is a tar archive.
  32  *
  33  * Stolen (by the author!) from the public domain tar program:
  34  * Public Domain version written 26 Aug 1985 John Gilmore (ihnp4!hoptoad!gnu).
  35  *
  36  * @(#)list.c 1.18 9/23/86 Public Domain - gnu
  37  *
  38  * Comments changed and some code/comments reformatted
  39  * for file command by Ian Darwin.
  40  */
  41
  42 #include "file.h"
  43
  44 #ifndef lint
  45 #if 0
  46 FILE_RCSID("@(#)$File: is_tar.c,v 1.36 2009/02/03 20:27:51 christos Exp $")
  47 #else
  48 __RCSID("$NetBSD$");
  49 #endif
  50 #endif
  51
  52 #include "magic.h"
  53 #include <string.h>
  54 #include <ctype.h>
  55 #include "tar.h"
  56
  57 #define isodigit(c)     ( ((c) >= '0') && ((c) <= '7') )
  58
  59 private int is_tar(const unsigned char *, size_t);
  60 private int from_oct(int, const char *);        /* Decode octal number */
  61
  62 static const char tartype[][32] = {
  63         "tar archive",
  64         "POSIX tar archive",
  65         "POSIX tar archive (GNU)",
  66 };
  67
  68 protected int
  69 file_is_tar(struct magic_set *ms, const unsigned char *buf, size_t nbytes)
  70 {
  71         /*
  72          * Do the tar test first, because if the first file in the tar
  73          * archive starts with a dot, we can confuse it with an nroff file.
  74          */
  75         int tar;
  76         int mime = ms->flags & MAGIC_MIME;
  77
  78         if ((ms->flags & MAGIC_APPLE) != 0)
  79                 return 0;
  80
  81         tar = is_tar(buf, nbytes);
  82         if (tar < 1 || tar > 3)
  83                 return 0;
  84
  85         if (file_printf(ms, "%s", mime ? "application/x-tar" :
  86             tartype[tar - 1]) == -1)
  87                 return -1;
  88         return 1;
  89 }
  90
  91 /*
  92  * Return
  93  *      0 if the checksum is bad (i.e., probably not a tar archive),
  94  *      1 for old UNIX tar file,
  95  *      2 for Unix Std (POSIX) tar file,
  96  *      3 for GNU tar file.
  97  */
  98 private int
  99 is_tar(const unsigned char *buf, size_t nbytes)
 100 {
 101         const union record *header = (const union record *)(const void *)buf;
 102         int     i;
 103         int     sum, recsum;
 104         const char      *p;
 105
 106         if (nbytes < sizeof(union record))
 107                 return 0;
 108
 109         recsum = from_oct(8,  header->header.chksum);
 110
 111         sum = 0;
 112         p = header->charptr;
 113         for (i = sizeof(union record); --i >= 0;) {
 114                 /*
 115                  * We cannot use unsigned char here because of old compilers,
 116                  * e.g. V7.
 117                  */
 118                 sum += 0xFF & *p++;
 119         }
 120
 121         /* Adjust checksum to count the "chksum" field as blanks. */
 122         for (i = sizeof(header->header.chksum); --i >= 0;)
 123                 sum -= 0xFF & header->header.chksum[i];
 124         sum += ' '* sizeof header->header.chksum;
 125
 126         if (sum != recsum)
 127                 return 0;       /* Not a tar archive */
 128
 129         if (strcmp(header->header.magic, GNUTMAGIC) == 0)
 130                 return 3;               /* GNU Unix Standard tar archive */
 131         if (strcmp(header->header.magic, TMAGIC) == 0)
 132                 return 2;               /* Unix Standard tar archive */
 133
 134         return 1;                       /* Old fashioned tar archive */
 135 }
 136
 137
 138 /*
 139  * Quick and dirty octal conversion.
 140  *
 141  * Result is -1 if the field is invalid (all blank, or nonoctal).
 142  */
 143 private int
 144 from_oct(int digs, const char *where)
 145 {
 146         int     value;
 147
 148         while (isspace((unsigned char)*where)) {        /* Skip spaces */
 149                 where++;
 150                 if (--digs <= 0)
 151                         return -1;              /* All blank field */
 152         }
 153         value = 0;
 154         while (digs > 0 && isodigit(*where)) {  /* Scan til nonoctal */
 155                 value = (value << 3) | (*where++ - '0');
 156                 --digs;
 157         }
 158
 159         if (digs > 0 && *where && !isspace((unsigned char)*where))
 160                 return -1;                      /* Ended on non-space/nul */
 161
 162         return value;
 163 }