NetBSD/usr.bin/file/softmagic.c

296 lines
7.0 KiB
C

/*
* 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.
*/
#ifndef lint
static char rcsid[] = "$Id: softmagic.c,v 1.5 1993/11/03 04:04:22 mycroft Exp $";
#endif /* not lint */
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include "file.h"
static int match __P((unsigned char *));
static int mcheck __P((unsigned char *, struct magic *));
static void mprint __P((unsigned char *, struct magic *, unsigned long));
extern unsigned long signextend __P((struct magic *, unsigned long));
static int need_separator;
/*
* 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 */
int
softmagic(buf, nbytes)
unsigned char *buf;
int nbytes;
{
if (match(buf))
return 1;
return 0;
}
/*
* 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 int
match(s)
unsigned char *s;
{
int magindex = 0;
int cont_level = 0;
while (magindex < nmagic) {
/* if main entry matches, print it... */
need_separator = 0;
if (mcheck(s, &magic[magindex])) {
/* and any continuations that match */
cont_level++;
while (magic[magindex+1].cont_level != 0 &&
magindex < nmagic) {
++magindex;
if (cont_level >=
magic[magindex].cont_level) {
if (cont_level >
magic[magindex].cont_level) {
/*
* We're at the end of the
* level-"cont_level"
* continuations.
*/
cont_level =
magic[magindex].cont_level;
}
if (mcheck(s, &magic[magindex])) {
/*
* This continuation matched.
* If we see any continuations
* at a higher level,
* process them.
*/
cont_level++;
}
}
}
return 1; /* all through */
} else {
/* main entry didn't match, flush its continuation */
while (magic[magindex+1].cont_level != 0 &&
magindex < nmagic) {
++magindex;
}
}
++magindex; /* on to the next */
}
return 0; /* no match at all */
}
static void
mprint(s, m, v)
unsigned char *s;
struct magic *m;
unsigned long v;
{
register union VALUETYPE *p = (union VALUETYPE *)(s+m->offset);
char *pp, *rt;
if (m->desc[0]) {
if (need_separator && !m->nospflag)
(void) putchar(' ');
need_separator = 1;
}
switch (m->type) {
case BYTE:
case SHORT:
case BESHORT:
case LESHORT:
case LONG:
case BELONG:
case LELONG:
(void) printf(m->desc, v);
break;
case STRING:
if ((rt=strchr(p->s, '\n')) != NULL)
*rt = '\0';
(void) printf(m->desc, p->s);
if (rt)
*rt = '\n';
break;
case DATE:
case BEDATE:
case LEDATE:
pp = ctime((time_t*) &v);
if ((rt = strchr(pp, '\n')) != NULL)
*rt = '\0';
(void) printf(m->desc, pp);
if (rt)
*rt = '\n';
break;
default:
error("invalid m->type (%d) in mprint().\n", m->type);
/*NOTREACHED*/
}
}
static int
mcheck(s, m)
unsigned char *s;
struct magic *m;
{
register union VALUETYPE *p = (union VALUETYPE *)(s+m->offset);
register unsigned long l = m->value.l;
register unsigned long v;
register int matched;
if (debug) {
(void) printf("mcheck: %10.10s ", s);
mdump(m);
}
#if 0
if ( (m->value.s[0] == 'x') && (m->value.s[1] == '\0') ) {
printf("BOINK");
return 1;
}
#endif
switch (m->type) {
case BYTE:
v = p->b; break;
case SHORT:
v = p->h; break;
case LONG:
case DATE:
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;
case BESHORT:
v = (unsigned short)((p->hs[0]<<8)|(p->hs[1]));
break;
case BELONG:
case BEDATE:
v = (unsigned long)
((p->hl[0]<<24)|(p->hl[1]<<16)|(p->hl[2]<<8)|(p->hl[3]));
break;
case LESHORT:
v = (unsigned short)((p->hs[1]<<8)|(p->hs[0]));
break;
case LELONG:
case LEDATE:
v = (unsigned long)
((p->hl[3]<<24)|(p->hl[2]<<16)|(p->hl[1]<<8)|(p->hl[0]));
break;
default:
error("invalid type %d in mcheck().\n", m->type);
return -1;/*NOTREACHED*/
}
v = signextend(m, v);
if (m->flag & MASK)
v &= m->mask;
switch (m->reln) {
case 'x':
matched = 1; break;
case '!':
matched = v != l; break;
case '=':
matched = v == l; break;
case '>':
if (m->flag & UNSIGNED)
matched = v > l;
else
matched = (long)v > (long)l;
break;
case '<':
if (m->flag & UNSIGNED)
matched = v < l;
else
matched = (long)v < (long)l;
break;
case '&':
matched = (v & l) == l; break;
case '^':
matched = (v & l) != l; break;
default:
error("mcheck: can't happen: invalid relation %d.\n", m->reln);
return -1;/*NOTREACHED*/
}
if (matched)
mprint(s, m, v);
return matched;
}