/* @(#)softmagic.c 1.6 03/03/06 joerg */
#ifndef lint
static char sccsid[] =
"@(#)softmagic.c 1.6 03/03/06 joerg";
#endif
/*
** find file types by using a modified "magic" file
**
** based on file v3.22 by Ian F. Darwin (see below)
**
** Modified for mkhybrid James Pearson 19/5/98
*/
/*
* softmagic - interpret variable magic from /etc/magic
*
* Copyright (c) Ian F. Darwin, 1987.
* Written by Ian F. Darwin.
*
* This software is not subject to any license of the American Telephone
* and Telegraph Company or of the Regents of the University of California.
*
* Permission is granted to anyone to use this software for any purpose on
* any computer system, and to alter it and redistribute it freely, subject
* to the following restrictions:
*
* 1. The author is not responsible for the consequences of use of this
* software, no matter how awful, even if they arise from flaws in it.
*
* 2. The origin of this software must not be misrepresented, either by
* explicit claim or by omission. Since few users ever read sources,
* credits must appear in the documentation.
*
* 3. Altered versions must be plainly marked as such, and must not be
* misrepresented as being the original software. Since few users
* ever read sources, credits must appear in the documentation.
*
* 4. This notice may not be removed or altered.
*/
#include <mconfig.h>
#include <stdio.h>
#include <strdefs.h>
#include <stdxlib.h>
#include "file.h"
#ifndef lint
static char *moduleid =
"@(#)$Id: softmagic.c,v 1.34 1997/01/15 19:28:35 christos Exp $";
#endif /* lint */
#ifdef DEBUG
int debug = 1; /* debugging */
#else
#define debug 0 /* debugging */
#endif /* DEBUG */
/* static int match __PR((unsigned char *, int)); */
static char *match __PR((unsigned char *, int));
static int mget __PR((union VALUETYPE *,
unsigned char *, struct magic *, int));
/* QNX has a mcheck() prototyp in a public include file */
static int magcheck __PR((union VALUETYPE *, struct magic *));
#ifdef __used__
static void mdebug __PR((Int32_t, char *, int));
#endif
static int mconvert __PR((union VALUETYPE *, struct magic *));
/*
* softmagic - lookup one file in database
* (already read from /etc/magic by apprentice.c).
* Passed the name and FILE * of one file to be typed.
*/
/*ARGSUSED1*/ /* nbytes passed for regularity, maybe need later */
char *
softmagic(buf, nbytes)
unsigned char *buf;
int nbytes;
{
return (match(buf, nbytes));
}
/*
* Go through the whole list, stopping if you find a match. Process all
* the continuations of that match before returning.
*
* We support multi-level continuations:
*
* At any time when processing a successful top-level match, there is a
* current continuation level; it represents the level of the last
* successfully matched continuation.
*
* Continuations above that level are skipped as, if we see one, it
* means that the continuation that controls them - i.e, the
* lower-level continuation preceding them - failed to match.
*
* Continuations below that level are processed as, if we see one,
* it means we've finished processing or skipping higher-level
* continuations under the control of a successful or unsuccessful
* lower-level continuation, and are now seeing the next lower-level
* continuation and should process it. The current continuation
* level reverts to the level of the one we're seeing.
*
* Continuations at the current level are processed as, if we see
* one, there's no lower-level continuation that may have failed.
*
* If a continuation matches, we bump the current continuation level
* so that higher-level continuations are processed.
*/
static char *
match(s, nbytes)
unsigned char *s;
int nbytes;
{
int magindex = 0;
union VALUETYPE p;
for (magindex = 0; magindex < __f_nmagic; magindex++) {
/* if main entry matches, print it... */
if (!mget(&p, s, &__f_magic[magindex], nbytes) ||
!magcheck(&p, &__f_magic[magindex])) {
/*
* main entry didn't match,
* flush its continuations
*/
while (magindex < __f_nmagic &&
__f_magic[magindex + 1].cont_level != 0)
magindex++;
continue;
}
return (__f_magic[magindex].desc);
}
return 0; /* no match at all */
}
/*
* Convert the byte order of the data we are looking at
*/
static int
mconvert(p, m)
union VALUETYPE *p;
struct magic *m;
{
switch (m->type) {
case BYTE:
case SHORT:
case LONG:
case DATE:
return 1;
case STRING:
{
char *ptr;
/* Null terminate and eat the return */
p->s[sizeof(p->s) - 1] = '\0';
if ((ptr = strchr(p->s, '\n')) != NULL)
*ptr = '\0';
return 1;
}
case BESHORT:
p->h = (short)((p->hs[0]<<8)|(p->hs[1]));
return 1;
case BELONG:
case BEDATE:
p->l = (Int32_t)
((p->hl[0]<<24)|(p->hl[1]<<16)|(p->hl[2]<<8)|(p->hl[3]));
return 1;
case LESHORT:
p->h = (short)((p->hs[1]<<8)|(p->hs[0]));
return 1;
case LELONG:
case LEDATE:
p->l = (Int32_t)
((p->hl[3]<<24)|(p->hl[2]<<16)|(p->hl[1]<<8)|(p->hl[0]));
return 1;
default:
return 0;
}
}
#ifdef __used__
static void
mdebug(offset, str, len)
Int32_t offset;
char *str;
int len;
{
(void) fprintf(stderr, "mget @%d: ", offset);
showstr(stderr, (char *) str, len);
(void) fputc('\n', stderr);
(void) fputc('\n', stderr);
}
#endif
static int
mget(p, s, m, nbytes)
union VALUETYPE* p;
unsigned char *s;
struct magic *m;
int nbytes;
{
Int32_t offset = m->offset;
if (offset + sizeof(union VALUETYPE) <= nbytes)
memcpy(p, s + offset, sizeof(union VALUETYPE));
else {
/*
* the usefulness of padding with zeroes eludes me, it
* might even cause problems
*/
Int32_t have = nbytes - offset;
memset(p, 0, sizeof(union VALUETYPE));
if (have > 0)
memcpy(p, s + offset, have);
}
if (!mconvert(p, m))
return 0;
if (m->flag & INDIR) {
switch (m->in.type) {
case BYTE:
offset = p->b + m->in.offset;
break;
case SHORT:
offset = p->h + m->in.offset;
break;
case LONG:
offset = p->l + m->in.offset;
break;
}
if (offset + sizeof(union VALUETYPE) > nbytes)
return 0;
memcpy(p, s + offset, sizeof(union VALUETYPE));
if (!mconvert(p, m))
return 0;
}
return 1;
}
static int
magcheck(p, m)
union VALUETYPE* p;
struct magic *m;
{
register UInt32_t l = m->value.l;
register UInt32_t v;
int matched;
if ( (m->value.s[0] == 'x') && (m->value.s[1] == '\0') ) {
fprintf(stderr, "BOINK");
return 1;
}
switch (m->type) {
case BYTE:
v = p->b;
break;
case SHORT:
case BESHORT:
case LESHORT:
v = p->h;
break;
case LONG:
case BELONG:
case LELONG:
case DATE:
case BEDATE:
case LEDATE:
v = p->l;
break;
case STRING:
l = 0;
/* What we want here is:
* v = strncmp(m->value.s, p->s, m->vallen);
* but ignoring any nulls. bcmp doesn't give -/+/0
* and isn't universally available anyway.
*/
v = 0;
{
register unsigned char *a = (unsigned char*)m->value.s;
register unsigned char *b = (unsigned char*)p->s;
register int len = m->vallen;
while (--len >= 0)
if ((v = *b++ - *a++) != '\0')
break;
}
break;
default:
return 0;/*NOTREACHED*/
}
v = signextend(m, v) & m->mask;
switch (m->reln) {
case 'x':
if (debug)
(void) fprintf(stderr, "%u == *any* = 1\n", v);
matched = 1;
break;
case '!':
matched = v != l;
if (debug)
(void) fprintf(stderr, "%u != %u = %d\n",
v, l, matched);
break;
case '=':
matched = v == l;
if (debug)
(void) fprintf(stderr, "%u == %u = %d\n",
v, l, matched);
break;
case '>':
if (m->flag & UNSIGNED) {
matched = v > l;
if (debug)
(void) fprintf(stderr, "%u > %u = %d\n",
v, l, matched);
}
else {
matched = (Int32_t) v > (Int32_t) l;
if (debug)
(void) fprintf(stderr, "%d > %d = %d\n",
v, l, matched);
}
break;
case '<':
if (m->flag & UNSIGNED) {
matched = v < l;
if (debug)
(void) fprintf(stderr, "%u < %u = %d\n",
v, l, matched);
}
else {
matched = (Int32_t) v < (Int32_t) l;
if (debug)
(void) fprintf(stderr, "%d < %d = %d\n",
v, l, matched);
}
break;
case '&':
matched = (v & l) == l;
if (debug)
(void) fprintf(stderr, "((%x & %x) == %x) = %d\n",
v, l, l, matched);
break;
case '^':
matched = (v & l) != l;
if (debug)
(void) fprintf(stderr, "((%x & %x) != %x) = %d\n",
v, l, l, matched);
break;
default:
matched = 0;
break;/*NOTREACHED*/
}
return matched;
}
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