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warnx?/errx? paranoia (use "%s" not a bare string unless it is a
constant).  These are not security holes but it is worth fixing
them anyway both for robustness and so folks looking for examples
in the tree are not misled into doing something potentially dangerous.
Furthermore, it is a bad idea to assume that pathnames will not
include '%' in them and that error routines don't return strings
with '%' in them (especially in light of the possibility of locales).

/*	$OpenBSD: apprentice.c,v 1.10 2000/06/30 16:00:13 millert Exp $	*/

/*
 * apprentice - make one pass through /etc/magic, learning its secrets.
 *
 * 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <err.h>
#include "file.h"

#ifndef	lint
static char *moduleid = "$OpenBSD: apprentice.c,v 1.10 2000/06/30 16:00:13 millert Exp $";
#endif	/* lint */

#define	EATAB {while (isascii((unsigned char) *l) && \
		      isspace((unsigned char) *l))  ++l;}
#define LOWCASE(l) (isupper((unsigned char) (l)) ? \
			tolower((unsigned char) (l)) : (l))


static int getvalue	__P((struct magic *, char **));
static int hextoint	__P((int));
static char *getstr	__P((char *, char *, int, int *));
static int parse	__P((char *, int *, int));
static void eatsize	__P((char **));

static int maxmagic = 0;
static int alloc_incr = 256;

static int apprentice_1	__P((char *, int));

int
apprentice(fn, check)
char *fn;			/* list of magic files */
int check;			/* non-zero? checking-only run. */
{
	char *p, *mfn;
	int file_err, errs = -1;

        maxmagic = MAXMAGIS;
	magic = (struct magic *) calloc(sizeof(struct magic), maxmagic);
	mfn = malloc(strlen(fn)+1);
	if (magic == NULL || mfn == NULL) {
		warn("malloc");
		if (check)
			return -1;
		else
			exit(1);
	}
	fn = strcpy(mfn, fn);	/* ok */
  
	while (fn) {
		p = strchr(fn, ':');
		if (p)
			*p++ = '\0';
		file_err = apprentice_1(fn, check);
		if (file_err > errs)
			errs = file_err;
		fn = p;
	}
	if (errs == -1)
		warnx("couldn't find any magic files!");
	if (!check && errs)
		exit(1);

	free(mfn);
	return errs;
}

static int
apprentice_1(fn, check)
char *fn;			/* name of magic file */
int check;			/* non-zero? checking-only run. */
{
	static const char hdr[] =
		"cont\toffset\ttype\topcode\tmask\tvalue\tdesc";
	FILE *f;
	char line[BUFSIZ+1];
	int errs = 0;

	f = fopen(fn, "r");
	if (f==NULL) {
		if (errno != ENOENT)
			warn("%s", fn);
		return -1;
	}

	/* parse it */
	if (check)	/* print silly verbose header for USG compat. */
		(void) printf("%s\n", hdr);

	for (lineno = 1;fgets(line, BUFSIZ, f) != NULL; lineno++) {
		if (line[0]=='#')	/* comment, do not parse */
			continue;
		if (strlen(line) <= (unsigned)1) /* null line, garbage, etc */
			continue;
		line[strlen(line)-1] = '\0'; /* delete newline */
		if (parse(line, &nmagic, check) != 0)
			errs = 1;
	}

	(void) fclose(f);
	return errs;
}

/*
 * extend the sign bit if the comparison is to be signed
 */
uint32
signextend(m, v)
struct magic *m;
uint32 v;
{
	if (!(m->flag & UNSIGNED))
		switch(m->type) {
		/*
		 * Do not remove the casts below.  They are
		 * vital.  When later compared with the data,
		 * the sign extension must have happened.
		 */
		case BYTE:
			v = (char) v;
			break;
		case SHORT:
		case BESHORT:
		case LESHORT:
			v = (short) v;
			break;
		case DATE:
		case BEDATE:
		case LEDATE:
		case LONG:
		case BELONG:
		case LELONG:
			v = (int32) v;
			break;
		case STRING:
			break;
		default:
			warnx("can't happen: m->type=%d\n", m->type);
			return -1;
		}
	return v;
}

/*
 * parse one line from magic file, put into magic[index++] if valid
 */
static int
parse(l, ndx, check)
char *l;
int *ndx, check;
{
	int i = 0, nd = *ndx;
	struct magic *m;
	char *t, *s;

	if (nd+1 >= maxmagic){
	    struct magic *mtmp;

	    maxmagic += alloc_incr;
	    if ((mtmp = (struct magic *) realloc(magic, 
						  sizeof(struct magic) * 
						  maxmagic)) == NULL) {
		warn("malloc");
		if (check) {
			if (magic)
				free(magic);
			return -1;
		} else
			exit(1);
	    }
	    magic = mtmp;
	    memset(&magic[*ndx], 0, sizeof(struct magic) * alloc_incr);
	    alloc_incr *= 2;
	}
	m = &magic[*ndx];
	m->flag = 0;
	m->cont_level = 0;

	while (*l == '>') {
		++l;		/* step over */
		m->cont_level++; 
	}

	if (m->cont_level != 0 && *l == '(') {
		++l;		/* step over */
		m->flag |= INDIR;
	}
	if (m->cont_level != 0 && *l == '&') {
                ++l;            /* step over */
                m->flag |= ADD;
        }

	/* get offset, then skip over it */
	m->offset = (int) strtoul(l,&t,0);
        if (l == t)
		warnx("offset %s invalid", l);
        l = t;

	if (m->flag & INDIR) {
		m->in.type = LONG;
		m->in.offset = 0;
		/*
		 * read [.lbs][+-]nnnnn)
		 */
		if (*l == '.') {
			l++;
			switch (LOWCASE(*l)) {
			case 'l':
				m->in.type = LONG;
				break;
			case 'h':
			case 's':
				m->in.type = SHORT;
				break;
			case 'c':
			case 'b':
				m->in.type = BYTE;
				break;
			default:
				warnx("indirect offset type %c invalid", *l);
				break;
			}
			l++;
		}
		s = l;
		if (*l == '+' || *l == '-') l++;
		if (isdigit((unsigned char)*l)) {
			m->in.offset = strtoul(l, &t, 0);
			if (*s == '-') m->in.offset = - m->in.offset;
		}
		else
			t = l;
		if (*t++ != ')') 
			warnx("missing ')' in indirect offset");
		l = t;
	}


	while (isascii((unsigned char)*l) && isdigit((unsigned char)*l))
		++l;
	EATAB;

#define NBYTE		4
#define NSHORT		5
#define NLONG		4
#define NSTRING 	6
#define NDATE		4
#define NBESHORT	7
#define NBELONG		6
#define NBEDATE		6
#define NLESHORT	7
#define NLELONG		6
#define NLEDATE		6

	if (*l == 'u') {
		++l;
		m->flag |= UNSIGNED;
	}

	/* get type, skip it */
	if (strncmp(l, "byte", NBYTE)==0) {
		m->type = BYTE;
		l += NBYTE;
	} else if (strncmp(l, "short", NSHORT)==0) {
		m->type = SHORT;
		l += NSHORT;
	} else if (strncmp(l, "long", NLONG)==0) {
		m->type = LONG;
		l += NLONG;
	} else if (strncmp(l, "string", NSTRING)==0) {
		m->type = STRING;
		l += NSTRING;
	} else if (strncmp(l, "date", NDATE)==0) {
		m->type = DATE;
		l += NDATE;
	} else if (strncmp(l, "beshort", NBESHORT)==0) {
		m->type = BESHORT;
		l += NBESHORT;
	} else if (strncmp(l, "belong", NBELONG)==0) {
		m->type = BELONG;
		l += NBELONG;
	} else if (strncmp(l, "bedate", NBEDATE)==0) {
		m->type = BEDATE;
		l += NBEDATE;
	} else if (strncmp(l, "leshort", NLESHORT)==0) {
		m->type = LESHORT;
		l += NLESHORT;
	} else if (strncmp(l, "lelong", NLELONG)==0) {
		m->type = LELONG;
		l += NLELONG;
	} else if (strncmp(l, "ledate", NLEDATE)==0) {
		m->type = LEDATE;
		l += NLEDATE;
	} else {
		warnx("type %s invalid", l);
		return -1;
	}
	/* New-style anding: "0 byte&0x80 =0x80 dynamically linked" */
	if (*l == '&') {
		++l;
		m->mask = signextend(m, strtoul(l, &l, 0));
		eatsize(&l);
	} else
		m->mask = ~0L;
	EATAB;
  
	switch (*l) {
	case '>':
	case '<':
	/* Old-style anding: "0 byte &0x80 dynamically linked" */
	case '&':
	case '^':
	case '=':
  		m->reln = *l;
  		++l;
		break;
	case '!':
		if (m->type != STRING) {
			m->reln = *l;
			++l;
			break;
		}
		/* FALL THROUGH */
	default:
		if (*l == 'x' && isascii((unsigned char)l[1]) && 
		    isspace((unsigned char)l[1])) {
			m->reln = *l;
			++l;
			goto GetDesc;	/* Bill The Cat */
		}
  		m->reln = '=';
		break;
	}
  	EATAB;
  
	if (getvalue(m, &l))
		return -1;
	/*
	 * TODO finish this macro and start using it!
	 * #define offsetcheck {if (offset > HOWMANY-1) 
	 *	warnx("offset too big"); }
	 */

	/*
	 * now get last part - the description
	 */
GetDesc:
	EATAB;
	if (l[0] == '\b') {
		++l;
		m->nospflag = 1;
	} else if ((l[0] == '\\') && (l[1] == 'b')) {
		++l;
		++l;
		m->nospflag = 1;
	} else
		m->nospflag = 0;
	while ((m->desc[i++] = *l++) != '\0' && i<MAXDESC)
		/* NULLBODY */;

	if (check) {
		mdump(m);
	}
	++(*ndx);		/* make room for next */
	return 0;
}

/* 
 * Read a numeric value from a pointer, into the value union of a magic 
 * pointer, according to the magic type.  Update the string pointer to point 
 * just after the number read.  Return 0 for success, non-zero for failure.
 */
static int
getvalue(m, p)
struct magic *m;
char **p;
{
	int slen;

	if (m->type == STRING) {
		*p = getstr(*p, m->value.s, sizeof(m->value.s), &slen);
		m->vallen = slen;
	} else
		if (m->reln != 'x') {
			m->value.l = signextend(m, strtoul(*p, p, 0));
			eatsize(p);
		}
	return 0;
}

/*
 * Convert a string containing C character escapes.  Stop at an unescaped
 * space or tab.
 * Copy the converted version to "p", returning its length in *slen.
 * Return updated scan pointer as function result.
 */
static char *
getstr(s, p, plen, slen)
register char	*s;
register char	*p;
int	plen, *slen;
{
	char	*origs = s, *origp = p;
	char	*pmax = p + plen - 1;
	register int	c;
	register int	val;

	while ((c = *s++) != '\0') {
		if (isspace((unsigned char) c))
			break;
		if (p >= pmax) {
			fprintf(stderr, "String too long: %s\n", origs);
			break;
		}
		if(c == '\\') {
			switch(c = *s++) {

			case '\0':
				goto out;

			default:
				*p++ = (char) c;
				break;

			case 'n':
				*p++ = '\n';
				break;

			case 'r':
				*p++ = '\r';
				break;

			case 'b':
				*p++ = '\b';
				break;

			case 't':
				*p++ = '\t';
				break;

			case 'f':
				*p++ = '\f';
				break;

			case 'v':
				*p++ = '\v';
				break;

			/* \ and up to 3 octal digits */
			case '0':
			case '1':
			case '2':
			case '3':
			case '4':
			case '5':
			case '6':
			case '7':
				val = c - '0';
				c = *s++;  /* try for 2 */
				if(c >= '0' && c <= '7') {
					val = (val<<3) | (c - '0');
					c = *s++;  /* try for 3 */
					if(c >= '0' && c <= '7')
						val = (val<<3) | (c-'0');
					else
						--s;
				}
				else
					--s;
				*p++ = (char)val;
				break;

			/* \x and up to 2 hex digits */
			case 'x':
				val = 'x';	/* Default if no digits */
				c = hextoint(*s++);	/* Get next char */
				if (c >= 0) {
					val = c;
					c = hextoint(*s++);
					if (c >= 0)
						val = (val << 4) + c;
					else
						--s;
				} else
					--s;
				*p++ = (char)val;
				break;
			}
		} else
			*p++ = (char)c;
	}
out:
	*p = '\0';
	*slen = p - origp;
	return s;
}


/* Single hex char to int; -1 if not a hex char. */
static int
hextoint(c)
int c;
{
	if (!isascii((unsigned char) c))	return -1;
	if (isdigit((unsigned char) c))		return c - '0';
	if ((c>='a')&&(c<='f'))	return c + 10 - 'a';
	if ((c>='A')&&(c<='F'))	return c + 10 - 'A';
				return -1;
}


/*
 * Print a string containing C character escapes.
 */
void
showstr(fp, s, len)
FILE *fp;
const char *s;
int len;
{
	register char	c;

	for (;;) {
		c = *s++;
		if (len == -1) {
			if (c == '\0')
				break;
		}
		else  {
			if (len-- == 0)
				break;
		}
		if(c >= 040 && c <= 0176)	/* TODO isprint && !iscntrl */
			(void) fputc(c, fp);
		else {
			(void) fputc('\\', fp);
			switch (c) {
			
			case '\n':
				(void) fputc('n', fp);
				break;

			case '\r':
				(void) fputc('r', fp);
				break;

			case '\b':
				(void) fputc('b', fp);
				break;

			case '\t':
				(void) fputc('t', fp);
				break;

			case '\f':
				(void) fputc('f', fp);
				break;

			case '\v':
				(void) fputc('v', fp);
				break;

			default:
				(void) fprintf(fp, "%.3o", c & 0377);
				break;
			}
		}
	}
}

/*
 * eatsize(): Eat the size spec from a number [eg. 10UL]
 */
static void
eatsize(p)
char **p;
{
	char *l = *p;

	if (LOWCASE(*l) == 'u') 
		l++;

	switch (LOWCASE(*l)) {
	case 'l':    /* long */
	case 's':    /* short */
	case 'h':    /* short */
	case 'b':    /* char/byte */
	case 'c':    /* char/byte */
		l++;
		/*FALLTHROUGH*/
	default:
		break;
	}

	*p = l;
}