| /* | |
| * Copyright (c) Ian F. Darwin 1986-1995. | |
| * Software written by Ian F. Darwin and others; | |
| * maintained 1995-present by Christos Zoulas and others. | |
| * | |
| * 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 immediately at the beginning of the file, without modification, | |
| * 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. | |
| * | |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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. | |
| */ | |
| /* | |
| * is_tar() -- figure out whether file is a tar archive. | |
| * | |
| * Stolen (by the author!) from the file_public domain tar program: | |
| * Public Domain version written 26 Aug 1985 John Gilmore (ihnp4!hoptoad!gnu). | |
| * | |
| * @(#)list.c 1.18 9/23/86 Public Domain - gnu | |
| * | |
| * Comments changed and some code/comments reformatted | |
| * for file command by Ian Darwin. | |
| */ | |
| FILE_RCSID("@(#)$File: is_tar.c,v 1.50 2022/12/26 17:31:14 christos Exp $") | |
| file_private int is_tar(const unsigned char *, size_t); | |
| file_private int from_oct(const char *, size_t); /* Decode octal number */ | |
| static const char tartype[][32] = { /* should be equal to messages */ | |
| "tar archive", /* found in ../magic/Magdir/archive */ | |
| "POSIX tar archive", | |
| "POSIX tar archive (GNU)", /* */ | |
| }; | |
| file_protected int | |
| file_is_tar(struct magic_set *ms, const struct buffer *b) | |
| { | |
| const unsigned char *buf = CAST(const unsigned char *, b->fbuf); | |
| size_t nbytes = b->flen; | |
| /* | |
| * Do the tar test first, because if the first file in the tar | |
| * archive starts with a dot, we can confuse it with an nroff file. | |
| */ | |
| int tar; | |
| int mime = ms->flags & MAGIC_MIME; | |
| if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)) != 0) | |
| return 0; | |
| tar = is_tar(buf, nbytes); | |
| if (tar < 1 || tar > 3) | |
| return 0; | |
| if (mime == MAGIC_MIME_ENCODING) | |
| return 1; | |
| if (file_printf(ms, "%s", mime ? "application/x-tar" : | |
| tartype[tar - 1]) == -1) | |
| return -1; | |
| return 1; | |
| } | |
| /* | |
| * Return | |
| * 0 if the checksum is bad (i.e., probably not a tar archive), | |
| * 1 for old UNIX tar file, | |
| * 2 for Unix Std (POSIX) tar file, | |
| * 3 for GNU tar file. | |
| */ | |
| file_private int | |
| is_tar(const unsigned char *buf, size_t nbytes) | |
| { | |
| static const char gpkg_match[] = "/gpkg-1"; | |
| const union record *header = RCAST(const union record *, | |
| RCAST(const void *, buf)); | |
| size_t i; | |
| int sum, recsum; | |
| const unsigned char *p, *ep; | |
| const char *nulp; | |
| if (nbytes < sizeof(*header)) | |
| return 0; | |
| /* If the file looks like Gentoo GLEP 78 binary package (GPKG), | |
| * don't waste time on further checks and fall back to magic rules. | |
| */ | |
| nulp = CAST(const char *, | |
| memchr(header->header.name, 0, sizeof(header->header.name))); | |
| if (nulp != NULL && nulp >= header->header.name + sizeof(gpkg_match) && | |
| memcmp(nulp - sizeof(gpkg_match) + 1, gpkg_match, | |
| sizeof(gpkg_match)) == 0) | |
| return 0; | |
| recsum = from_oct(header->header.chksum, sizeof(header->header.chksum)); | |
| sum = 0; | |
| p = header->charptr; | |
| ep = header->charptr + sizeof(*header); | |
| while (p < ep) | |
| sum += *p++; | |
| /* Adjust checksum to count the "chksum" field as blanks. */ | |
| for (i = 0; i < sizeof(header->header.chksum); i++) | |
| sum -= header->header.chksum[i]; | |
| sum += ' ' * sizeof(header->header.chksum); | |
| if (sum != recsum) | |
| return 0; /* Not a tar archive */ | |
| if (strncmp(header->header.magic, GNUTMAGIC, | |
| sizeof(header->header.magic)) == 0) | |
| return 3; /* GNU Unix Standard tar archive */ | |
| if (strncmp(header->header.magic, TMAGIC, | |
| sizeof(header->header.magic)) == 0) | |
| return 2; /* Unix Standard tar archive */ | |
| return 1; /* Old fashioned tar archive */ | |
| } | |
| /* | |
| * Quick and dirty octal conversion. | |
| * | |
| * Result is -1 if the field is invalid (all blank, or non-octal). | |
| */ | |
| file_private int | |
| from_oct(const char *where, size_t digs) | |
| { | |
| int value; | |
| if (digs == 0) | |
| return -1; | |
| while (isspace(CAST(unsigned char, *where))) { /* Skip spaces */ | |
| where++; | |
| if (digs-- == 0) | |
| return -1; /* All blank field */ | |
| } | |
| value = 0; | |
| while (digs > 0 && isodigit(*where)) { /* Scan til non-octal */ | |
| value = (value << 3) | (*where++ - '0'); | |
| digs--; | |
| } | |
| if (digs > 0 && *where && !isspace(CAST(unsigned char, *where))) | |
| return -1; /* Ended on non-(space/NUL) */ | |
| return value; | |
| } | |