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Diffstat (limited to 'src/is_tar.c')
| -rw-r--r-- | src/is_tar.c | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/src/is_tar.c b/src/is_tar.c new file mode 100644 index 0000000..fa83e1e --- /dev/null +++ b/src/is_tar.c @@ -0,0 +1,179 @@ +/* + * 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. + */ + +#include "file.h" + +#ifndef lint +FILE_RCSID("@(#)$File: is_tar.c,v 1.50 2022/12/26 17:31:14 christos Exp $") +#endif + +#include "magic.h" +#include <string.h> +#include <ctype.h> +#include "tar.h" + +#define isodigit(c) ( ((c) >= '0') && ((c) <= '7') ) + +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; +} |