464 lines
10 KiB
C
464 lines
10 KiB
C
/*
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* softmagic - interpret variable magic from /etc/magic
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*
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* Copyright (c) Ian F. Darwin, 1987.
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* Written by Ian F. Darwin.
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*
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* This software is not subject to any license of the American Telephone
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* and Telegraph Company or of the Regents of the University of California.
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*
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* Permission is granted to anyone to use this software for any purpose on
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* any computer system, and to alter it and redistribute it freely, subject
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* to the following restrictions:
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*
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* 1. The author is not responsible for the consequences of use of this
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* software, no matter how awful, even if they arise from flaws in it.
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*
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* 2. The origin of this software must not be misrepresented, either by
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* explicit claim or by omission. Since few users ever read sources,
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* credits must appear in the documentation.
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*
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* 3. Altered versions must be plainly marked as such, and must not be
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* misrepresented as being the original software. Since few users
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* ever read sources, credits must appear in the documentation.
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*
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* 4. This notice may not be removed or altered.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <time.h>
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#include <sys/types.h>
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#include "file.h"
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#ifndef lint
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static char *moduleid =
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"@(#)$Id: softmagic.c,v 1.1.1.1 1994/09/03 19:16:22 csgr Exp $";
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#endif /* lint */
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static int match __P((unsigned char *, int));
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static int mget __P((union VALUETYPE *,
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unsigned char *, struct magic *, int));
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static int mcheck __P((union VALUETYPE *, struct magic *));
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static void mprint __P((union VALUETYPE *, struct magic *));
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static void mdebug __P((long, char *, int));
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static int mconvert __P((union VALUETYPE *, struct magic *));
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/*
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* softmagic - lookup one file in database
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* (already read from /etc/magic by apprentice.c).
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* Passed the name and FILE * of one file to be typed.
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*/
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/*ARGSUSED1*/ /* nbytes passed for regularity, maybe need later */
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int
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softmagic(buf, nbytes)
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unsigned char *buf;
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int nbytes;
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{
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if (match(buf, nbytes))
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return 1;
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return 0;
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}
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/*
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* Go through the whole list, stopping if you find a match. Process all
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* the continuations of that match before returning.
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*
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* We support multi-level continuations:
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*
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* At any time when processing a successful top-level match, there is a
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* current continuation level; it represents the level of the last
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* successfully matched continuation.
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*
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* Continuations above that level are skipped as, if we see one, it
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* means that the continuation that controls them - i.e, the
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* lower-level continuation preceding them - failed to match.
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*
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* Continuations below that level are processed as, if we see one,
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* it means we've finished processing or skipping higher-level
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* continuations under the control of a successful or unsuccessful
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* lower-level continuation, and are now seeing the next lower-level
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* continuation and should process it. The current continuation
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* level reverts to the level of the one we're seeing.
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*
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* Continuations at the current level are processed as, if we see
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* one, there's no lower-level continuation that may have failed.
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*
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* If a continuation matches, we bump the current continuation level
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* so that higher-level continuations are processed.
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*/
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static int
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match(s, nbytes)
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unsigned char *s;
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int nbytes;
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{
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int magindex = 0;
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int cont_level = 0;
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int need_separator = 0;
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union VALUETYPE p;
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for (magindex = 0; magindex < nmagic; magindex++) {
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/* if main entry matches, print it... */
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if (!mget(&p, s, &magic[magindex], nbytes) ||
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!mcheck(&p, &magic[magindex])) {
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/*
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* main entry didn't match,
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* flush its continuations
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*/
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while (magindex < nmagic &&
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magic[magindex + 1].cont_level != 0)
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magindex++;
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continue;
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}
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mprint(&p, &magic[magindex]);
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/*
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* If we printed something, we'll need to print
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* a blank before we print something else.
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*/
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if (magic[magindex].desc[0])
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need_separator = 1;
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/* and any continuations that match */
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cont_level++;
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while (magic[magindex+1].cont_level != 0 &&
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++magindex < nmagic) {
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if (cont_level >= magic[magindex].cont_level) {
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if (cont_level > magic[magindex].cont_level) {
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/*
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* We're at the end of the level
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* "cont_level" continuations.
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*/
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cont_level = magic[magindex].cont_level;
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}
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if (mget(&p, s, &magic[magindex], nbytes) &&
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mcheck(&p, &magic[magindex])) {
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/*
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* This continuation matched.
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* Print its message, with
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* a blank before it if
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* the previous item printed
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* and this item isn't empty.
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*/
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/* space if previous printed */
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if (need_separator
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&& (magic[magindex].nospflag == 0)
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&& (magic[magindex].desc[0] != '\0')
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) {
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(void) putchar(' ');
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need_separator = 0;
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}
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mprint(&p, &magic[magindex]);
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if (magic[magindex].desc[0])
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need_separator = 1;
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/*
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* If we see any continuations
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* at a higher level,
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* process them.
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*/
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cont_level++;
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}
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}
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}
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return 1; /* all through */
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}
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return 0; /* no match at all */
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}
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static void
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mprint(p, m)
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union VALUETYPE *p;
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struct magic *m;
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{
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char *pp, *rt;
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unsigned long v;
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switch (m->type) {
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case BYTE:
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v = p->b;
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break;
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case SHORT:
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case BESHORT:
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case LESHORT:
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v = p->h;
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break;
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case LONG:
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case BELONG:
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case LELONG:
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v = p->l;
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break;
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case STRING:
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if (m->reln == '=') {
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(void) printf(m->desc, m->value.s);
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}
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else {
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(void) printf(m->desc, p->s);
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}
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return;
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case DATE:
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case BEDATE:
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case LEDATE:
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pp = ctime((time_t*) &p->l);
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if ((rt = strchr(pp, '\n')) != NULL)
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*rt = '\0';
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(void) printf(m->desc, pp);
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return;
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default:
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error("invalid m->type (%d) in mprint().\n", m->type);
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/*NOTREACHED*/
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}
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v = signextend(m, v) & m->mask;
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(void) printf(m->desc, v);
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}
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/*
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* Convert the byte order of the data we are looking at
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*/
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static int
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mconvert(p, m)
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union VALUETYPE *p;
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struct magic *m;
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{
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char *rt;
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switch (m->type) {
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case BYTE:
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case SHORT:
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case LONG:
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case DATE:
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return 1;
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case STRING:
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/* Null terminate and eat the return */
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p->s[sizeof(p->s) - 1] = '\0';
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if ((rt = strchr(p->s, '\n')) != NULL)
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*rt = '\0';
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return 1;
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case BESHORT:
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p->h = (short)((p->hs[0]<<8)|(p->hs[1]));
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return 1;
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case BELONG:
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case BEDATE:
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p->l = (long)
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((p->hl[0]<<24)|(p->hl[1]<<16)|(p->hl[2]<<8)|(p->hl[3]));
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return 1;
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case LESHORT:
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p->h = (short)((p->hs[1]<<8)|(p->hs[0]));
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return 1;
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case LELONG:
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case LEDATE:
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p->l = (long)
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((p->hl[3]<<24)|(p->hl[2]<<16)|(p->hl[1]<<8)|(p->hl[0]));
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return 1;
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default:
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error("invalid type %d in mconvert().\n", m->type);
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return 0;
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}
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}
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static void
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mdebug(offset, str, len)
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long offset;
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char *str;
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int len;
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{
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(void) fprintf(stderr, "mget @%d: ", offset);
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showstr(stderr, (char *) str, len);
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(void) fputc('\n', stderr);
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(void) fputc('\n', stderr);
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}
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static int
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mget(p, s, m, nbytes)
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union VALUETYPE* p;
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unsigned char *s;
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struct magic *m;
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int nbytes;
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{
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long offset = m->offset;
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if (offset + sizeof(union VALUETYPE) > nbytes)
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return 0;
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memcpy(p, s + offset, sizeof(union VALUETYPE));
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if (debug) {
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mdebug(offset, (char *) p, sizeof(union VALUETYPE));
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mdump(m);
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}
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if (!mconvert(p, m))
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return 0;
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if (m->flag & INDIR) {
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switch (m->in.type) {
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case BYTE:
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offset = p->b + m->in.offset;
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break;
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case SHORT:
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offset = p->h + m->in.offset;
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break;
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case LONG:
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offset = p->l + m->in.offset;
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break;
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}
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if (offset + sizeof(union VALUETYPE) > nbytes)
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return 0;
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memcpy(p, s + offset, sizeof(union VALUETYPE));
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if (debug) {
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mdebug(offset, (char *) p, sizeof(union VALUETYPE));
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mdump(m);
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}
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if (!mconvert(p, m))
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return 0;
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}
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return 1;
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}
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static int
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mcheck(p, m)
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union VALUETYPE* p;
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struct magic *m;
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{
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register unsigned long l = m->value.l;
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register unsigned long v;
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int matched;
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if ( (m->value.s[0] == 'x') && (m->value.s[1] == '\0') ) {
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fprintf(stderr, "BOINK");
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return 1;
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}
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switch (m->type) {
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case BYTE:
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v = p->b;
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break;
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case SHORT:
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case BESHORT:
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case LESHORT:
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v = p->h;
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break;
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case LONG:
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case BELONG:
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case LELONG:
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case DATE:
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case BEDATE:
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case LEDATE:
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v = p->l;
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break;
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case STRING:
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l = 0;
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/* What we want here is:
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* v = strncmp(m->value.s, p->s, m->vallen);
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* but ignoring any nulls. bcmp doesn't give -/+/0
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* and isn't universally available anyway.
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*/
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v = 0;
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{
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register unsigned char *a = (unsigned char*)m->value.s;
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register unsigned char *b = (unsigned char*)p->s;
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register int len = m->vallen;
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while (--len >= 0)
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if ((v = *b++ - *a++) != 0)
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break;
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}
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break;
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default:
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error("invalid type %d in mcheck().\n", m->type);
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return 0;/*NOTREACHED*/
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}
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v = signextend(m, v) & m->mask;
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switch (m->reln) {
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case 'x':
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if (debug)
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(void) fprintf(stderr, "%lu == *any* = 1\n", v);
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matched = 1;
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break;
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case '!':
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matched = v != l;
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if (debug)
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(void) fprintf(stderr, "%lu != %lu = %d\n",
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v, l, matched);
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break;
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case '=':
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matched = v == l;
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if (debug)
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(void) fprintf(stderr, "%lu == %lu = %d\n",
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v, l, matched);
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break;
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case '>':
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if (m->flag & UNSIGNED) {
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matched = v > l;
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if (debug)
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(void) fprintf(stderr, "%lu > %lu = %d\n",
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v, l, matched);
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}
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else {
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matched = (long) v > (long) l;
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if (debug)
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(void) fprintf(stderr, "%ld > %ld = %d\n",
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v, l, matched);
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}
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break;
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case '<':
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if (m->flag & UNSIGNED) {
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matched = v < l;
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if (debug)
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(void) fprintf(stderr, "%lu < %lu = %d\n",
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v, l, matched);
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}
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else {
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matched = (long) v < (long) l;
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if (debug)
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(void) fprintf(stderr, "%ld < %ld = %d\n",
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v, l, matched);
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}
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break;
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case '&':
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matched = (v & l) == l;
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if (debug)
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(void) fprintf(stderr, "((%lx & %lx) == %lx) = %d\n",
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v, l, l, matched);
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break;
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case '^':
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matched = (v & l) != l;
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if (debug)
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(void) fprintf(stderr, "((%lx & %lx) != %lx) = %d\n",
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v, l, l, matched);
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break;
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default:
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matched = 0;
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error("mcheck: can't happen: invalid relation %d.\n", m->reln);
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break;/*NOTREACHED*/
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}
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return matched;
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}
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