1 /* $NetBSD: is_tar.c,v 1.1.1.12 2026/06/10 15:59:13 christos Exp $ */ 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 file_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 1.51 2026/06/02 17:05:51 christos Exp $") 47 #else 48 __RCSID("$NetBSD: is_tar.c,v 1.1.1.12 2026/06/10 15:59:13 christos Exp $"); 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 file_private int is_tar(const unsigned char *, size_t); 60 file_private int from_oct(const char *, size_t); /* Decode octal number */ 61 62 static const char tartype[][32] = { /* should be equal to messages */ 63 "tar archive", /* found in ../magic/Magdir/archive */ 64 "POSIX tar archive", 65 "POSIX tar archive (GNU)", /* */ 66 }; 67 68 file_protected int 69 file_is_tar(struct magic_set *ms, const struct buffer *b) 70 { 71 const unsigned char *buf = CAST(const unsigned char *, b->fbuf); 72 size_t nbytes = b->flen; 73 /* 74 * Do the tar test first, because if the first file in the tar 75 * archive starts with a dot, we can confuse it with an nroff file. 76 */ 77 int tar; 78 int mime = ms->flags & MAGIC_MIME; 79 80 if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)) != 0) 81 return 0; 82 83 tar = is_tar(buf, nbytes); 84 if (tar < 1 || tar > 3) 85 return 0; 86 87 if (mime == MAGIC_MIME_ENCODING) 88 return 1; 89 90 if (file_printf(ms, "%s", mime ? "application/x-tar" : 91 tartype[tar - 1]) == -1) 92 return -1; 93 94 return 1; 95 } 96 97 /* 98 * Return 99 * 0 if the checksum is bad (i.e., probably not a tar archive), 100 * 1 for old UNIX tar file, 101 * 2 for Unix Std (POSIX) tar file, 102 * 3 for GNU tar file. 103 */ 104 file_private int 105 is_tar(const unsigned char *buf, size_t nbytes) 106 { 107 static const char gpkg_match[] = "/gpkg-1"; 108 109 const union record *header = RCAST(const union record *, 110 RCAST(const void *, buf)); 111 size_t i; 112 int sum, recsum; 113 const unsigned char *p, *ep; 114 const char *nulp; 115 116 if (nbytes < sizeof(*header)) 117 return 0; 118 119 /* If the file looks like Gentoo GLEP 78 binary package (GPKG), 120 * don't waste time on further checks and fall back to magic rules. 121 */ 122 nulp = CAST(const char *, 123 memchr(header->header.name, 0, sizeof(header->header.name))); 124 if (nulp != NULL && nulp >= header->header.name + sizeof(gpkg_match) && 125 memcmp(nulp - sizeof(gpkg_match) + 1, gpkg_match, 126 sizeof(gpkg_match)) == 0) 127 return 0; 128 129 recsum = from_oct(header->header.chksum, sizeof(header->header.chksum)); 130 131 sum = 0; 132 p = header->charptr; 133 ep = header->charptr + sizeof(*header); 134 while (p < ep) 135 sum += *p++; 136 137 /* Adjust checksum to count the "chksum" field as blanks. */ 138 for (i = 0; i < sizeof(header->header.chksum); i++) 139 sum -= header->header.chksum[i]; 140 sum += ' ' * sizeof(header->header.chksum); 141 142 if (sum != recsum) 143 return 0; /* Not a tar archive */ 144 145 if (strncmp(header->header.magic, GNUTMAGIC, 146 sizeof(header->header.magic)) == 0) 147 return 3; /* GNU Unix Standard tar archive */ 148 149 if (strncmp(header->header.magic, TMAGIC, 150 sizeof(header->header.magic)) == 0) 151 return 2; /* Unix Standard tar archive */ 152 153 return 1; /* Old fashioned tar archive */ 154 } 155 156 157 /* 158 * Quick and dirty octal conversion. 159 * 160 * Result is -1 if the field is invalid (all blank, or non-octal). 161 */ 162 file_private int 163 from_oct(const char *where, size_t digs) 164 { 165 int value; 166 167 while (digs > 0 && isspace(CAST(unsigned char, *where))) { /* Skip spaces */ 168 where++; 169 digs--; 170 } 171 if (digs == 0) 172 return -1; /* All blank field */ 173 value = 0; 174 while (digs > 0 && isodigit(*where)) { /* Scan til non-octal */ 175 value = (value << 3) | (*where++ - '0'); 176 digs--; 177 } 178 179 if (digs > 0 && *where && !isspace(CAST(unsigned char, *where))) 180 return -1; /* Ended on non-(space/NUL) */ 181 182 return value; 183 } 184
Indexes created Fri Jul 03 00:25:33 UTC 2026