softmagic.c

sleuthit-2.09 一个磁盘的工具集

/*
 * Convert the byte order of the data we are looking at
 * While we're here, let's apply the mask operation
 * (unless you have a better idea)
 */
private int
mconvert(struct magic_set *ms, struct magic *m)
{
	union VALUETYPE *p = &ms->ms_value;

	switch (m->type) {
	case FILE_BYTE:
		cvt_8(p, m);
		return 1;
	case FILE_SHORT:
		cvt_16(p, m);
		return 1;
	case FILE_LONG:
	case FILE_DATE:
	case FILE_LDATE:
		cvt_32(p, m);
		return 1;
	case FILE_QUAD:
	case FILE_QDATE:
	case FILE_QLDATE:
		cvt_64(p, m);
		return 1;
	case FILE_STRING:
	case FILE_BESTRING16:
	case FILE_LESTRING16: {
		size_t len;
		
		/* Null terminate and eat *trailing* return */
		p->s[sizeof(p->s) - 1] = '\0';
		len = strlen(p->s);
		if (len-- && p->s[len] == '\n')
			p->s[len] = '\0';
		return 1;
	}
	case FILE_PSTRING: {
		char *ptr1 = p->s, *ptr2 = ptr1 + 1;
		size_t len = *p->s;
		if (len >= sizeof(p->s))
			len = sizeof(p->s) - 1;
		while (len--)
			*ptr1++ = *ptr2++;
		*ptr1 = '\0';
		len = strlen(p->s);
		if (len-- && p->s[len] == '\n')
			p->s[len] = '\0';
		return 1;
	}
	case FILE_BESHORT:
		p->h = (short)((p->hs[0]<<8)|(p->hs[1]));
		cvt_16(p, m);
		return 1;
	case FILE_BELONG:
	case FILE_BEDATE:
	case FILE_BELDATE:
		p->l = (int32_t)
		    ((p->hl[0]<<24)|(p->hl[1]<<16)|(p->hl[2]<<8)|(p->hl[3]));
		cvt_32(p, m);
		return 1;
	case FILE_BEQUAD:
	case FILE_BEQDATE:
	case FILE_BEQLDATE:
		p->q = (int64_t)
		    (((int64_t)p->hq[0]<<56)|((int64_t)p->hq[1]<<48)|
		     ((int64_t)p->hq[2]<<40)|((int64_t)p->hq[3]<<32)|
		     (p->hq[4]<<24)|(p->hq[5]<<16)|(p->hq[6]<<8)|(p->hq[7]));
		cvt_64(p, m);
		return 1;
	case FILE_LESHORT:
		p->h = (short)((p->hs[1]<<8)|(p->hs[0]));
		cvt_16(p, m);
		return 1;
	case FILE_LELONG:
	case FILE_LEDATE:
	case FILE_LELDATE:
		p->l = (int32_t)
		    ((p->hl[3]<<24)|(p->hl[2]<<16)|(p->hl[1]<<8)|(p->hl[0]));
		cvt_32(p, m);
		return 1;
	case FILE_LEQUAD:
	case FILE_LEQDATE:
	case FILE_LEQLDATE:
		p->q = (int64_t)
		    (((int64_t)p->hq[7]<<56)|((int64_t)p->hq[6]<<48)|
		     ((int64_t)p->hq[5]<<40)|((int64_t)p->hq[4]<<32)|
		     (p->hq[3]<<24)|(p->hq[2]<<16)|(p->hq[1]<<8)|(p->hq[0]));
		cvt_64(p, m);
		return 1;
	case FILE_MELONG:
	case FILE_MEDATE:
	case FILE_MELDATE:
		p->l = (int32_t)
		    ((p->hl[1]<<24)|(p->hl[0]<<16)|(p->hl[3]<<8)|(p->hl[2]));
		cvt_32(p, m);
		return 1;
	case FILE_REGEX:
	case FILE_SEARCH:
	case FILE_DEFAULT:
		return 1;
	default:
		file_magerror(ms, "invalid type %d in mconvert()", m->type);
		return 0;
	}
}


private void
mdebug(uint32_t offset, const char *str, size_t len)
{
	(void) fprintf(stderr, "mget @%d: ", offset);
	file_showstr(stderr, str, len);
	(void) fputc('\n', stderr);
	(void) fputc('\n', stderr);
}

private int
mcopy(struct magic_set *ms, union VALUETYPE *p, int type, int indir,
    const unsigned char *s, uint32_t offset, size_t nbytes, size_t linecnt)
{
	/*
	 * Note: FILE_SEARCH and FILE_REGEX do not actually copy
	 * anything, but setup pointers into the source
	 */
	if (indir == 0) {
		switch (type) {
		case FILE_SEARCH:
			ms->search.s = (const char *)s + offset;
			ms->search.s_len = nbytes - offset;
			return 0;

		case FILE_REGEX: {
			/*
			 * offset is interpreted as last line to search,
			 * (starting at 1), not as bytes-from start-of-file
			 */
			const char *b;
			const char *c;
			const char *last;	/* end of search region */
			const char *buf;	/* start of search region */
			size_t lines;

			if (s == NULL) {
				ms->search.s_len = 0;
				ms->search.s = NULL;
				return 0;
			}
			buf = (const char *)s + offset;
			last = (const char *)s + nbytes;
			/* mget() guarantees buf <= last */
			for (lines = linecnt, b = buf;
			     lines && ((b = strchr(c = b, '\n')) || (b = strchr(c, '\r')));
			     lines--, b++) {
				last = b;
				if (b[0] == '\r' && b[1] == '\n')
					b++;
			}
			if (lines)
				last = (const char *)s + nbytes;
			
			ms->search.s = buf;
			ms->search.s_len = last - buf;
			ms->search.offset = offset;
			ms->search.rm_len = 0;
			return 0;
		}
		case FILE_BESTRING16:
		case FILE_LESTRING16: {
			const unsigned char *src = s + offset;
			const unsigned char *esrc = s + nbytes;
			char *dst = p->s;
			char *edst = &p->s[sizeof(p->s) - 1];
			
			if (type == FILE_BESTRING16)
				src++;
			
			/* check for pointer overflow */
			if (src < s) {
				file_magerror(ms, "invalid offset %zu in mcopy()",
				    offset);
				return -1;
			}
			for (/*EMPTY*/; src < esrc; src++, dst++) {
				if (dst < edst)
					*dst = *src++;
				else
					break;
				if (*dst == '\0')
					*dst = ' ';
			}
			*edst = '\0';
			return 0;
		}
		case FILE_STRING:	/* XXX - these two should not need */
		case FILE_PSTRING:	/* to copy anything, but do anyway. */
		default:
			break;
		}
	}

	if (offset >= nbytes) {
		(void)memset(p, '\0', sizeof(*p));
		return 0;
	}
	if (nbytes - offset < sizeof(*p))
		nbytes = nbytes - offset;
	else
		nbytes = sizeof(*p);

	(void)memcpy(p, s + offset, nbytes);

	/*
	 * the usefulness of padding with zeroes eludes me, it
	 * might even cause problems
	 */
	if (nbytes < sizeof(*p))
		(void)memset(((char *)(void *)p) + nbytes, '\0',
		    sizeof(*p) - nbytes);
	return 0;
}

private int
mget(struct magic_set *ms, const unsigned char *s,
    struct magic *m, size_t nbytes, unsigned int cont_level)
{
	uint32_t offset = ms->offset;
	uint32_t count = m->str_count;
	union VALUETYPE *p = &ms->ms_value;

	if (mcopy(ms, p, m->type, m->flag & INDIR, s, offset, nbytes, count) == -1)
		return -1;

	if ((ms->flags & MAGIC_DEBUG) != 0) {
		mdebug(offset, (char *)(void *)p, sizeof(union VALUETYPE));
		file_mdump(m);
	}

	if (m->flag & INDIR) {
		int off = m->in_offset;
		if (m->in_op & FILE_OPINDIRECT) {
			const union VALUETYPE *q =
			    ((const void *)(s + offset + off));
			switch (m->in_type) {
			case FILE_BYTE:
				off = q->b;
				break;
			case FILE_SHORT:
				off = q->h;
				break;
			case FILE_BESHORT:
				off = (short)((q->hs[0]<<8)|(q->hs[1]));
				break;
			case FILE_LESHORT:
				off = (short)((q->hs[1]<<8)|(q->hs[0]));
				break;
			case FILE_LONG:
				off = q->l;
				break;
			case FILE_BELONG:
				off = (int32_t)((q->hl[0]<<24)|(q->hl[1]<<16)|
						 (q->hl[2]<<8)|(q->hl[3]));
				break;
			case FILE_LELONG:
				off = (int32_t)((q->hl[3]<<24)|(q->hl[2]<<16)|
						 (q->hl[1]<<8)|(q->hl[0]));
				break;
			case FILE_MELONG:
				off = (int32_t)((q->hl[1]<<24)|(q->hl[0]<<16)|
						 (q->hl[3]<<8)|(q->hl[2]));
				break;
			}
		}
		switch (m->in_type) {
		case FILE_BYTE:
			if (nbytes < (offset + 1))
				return 0;
			if (off) {
				switch (m->in_op & FILE_OPS_MASK) {
				case FILE_OPAND:
					offset = p->b & off;
					break;
				case FILE_OPOR:
					offset = p->b | off;
					break;
				case FILE_OPXOR:
					offset = p->b ^ off;
					break;
				case FILE_OPADD:
					offset = p->b + off;
					break;
				case FILE_OPMINUS:
					offset = p->b - off;
					break;
				case FILE_OPMULTIPLY:
					offset = p->b * off;
					break;
				case FILE_OPDIVIDE:
					offset = p->b / off;
					break;
				case FILE_OPMODULO:
					offset = p->b % off;
					break;
				}
			} else
				offset = p->b;
			if (m->in_op & FILE_OPINVERSE)
				offset = ~offset;
			break;
		case FILE_BESHORT:
			if (nbytes < (offset + 2))
				return 0;
			if (off) {
				switch (m->in_op & FILE_OPS_MASK) {
				case FILE_OPAND:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) &
						 off;
					break;
				case FILE_OPOR:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) |
						 off;
					break;
				case FILE_OPXOR:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) ^
						 off;
					break;
				case FILE_OPADD:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) +
						 off;
					break;
				case FILE_OPMINUS:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) -
						 off;
					break;
				case FILE_OPMULTIPLY:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) *
						 off;
					break;
				case FILE_OPDIVIDE:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) /
						 off;
					break;
				case FILE_OPMODULO:
					offset = (short)((p->hs[0]<<8)|
							 (p->hs[1])) %
						 off;
					break;
				}
			} else
				offset = (short)((p->hs[0]<<8)|
						 (p->hs[1]));
			if (m->in_op & FILE_OPINVERSE)
				offset = ~offset;
			break;
		case FILE_LESHORT:
			if (nbytes < (offset + 2))
				return 0;
			if (off) {
				switch (m->in_op & FILE_OPS_MASK) {
				case FILE_OPAND:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) &
						 off;
					break;
				case FILE_OPOR:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) |
						 off;
					break;
				case FILE_OPXOR:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) ^
						 off;
					break;
				case FILE_OPADD:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) +
						 off;
					break;
				case FILE_OPMINUS:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) -
						 off;
					break;
				case FILE_OPMULTIPLY:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) *
						 off;
					break;
				case FILE_OPDIVIDE:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) /
						 off;
					break;
				case FILE_OPMODULO:
					offset = (short)((p->hs[1]<<8)|
							 (p->hs[0])) %
						 off;
					break;
				}
			} else
				offset = (short)((p->hs[1]<<8)|
						 (p->hs[0]));
			if (m->in_op & FILE_OPINVERSE)
				offset = ~offset;
			break;
		case FILE_SHORT:
			if (nbytes < (offset + 2))
				return 0;
			if (off) {
				switch (m->in_op & FILE_OPS_MASK) {
				case FILE_OPAND:
					offset = p->h & off;
					break;
				case FILE_OPOR:
					offset = p->h | off;
					break;
				case FILE_OPXOR:
					offset = p->h ^ off;
					break;
				case FILE_OPADD:
					offset = p->h + off;
					break;
				case FILE_OPMINUS:
					offset = p->h - off;
					break;
				case FILE_OPMULTIPLY:
					offset = p->h * off;
					break;
				case FILE_OPDIVIDE:
					offset = p->h / off;
					break;
				case FILE_OPMODULO:
					offset = p->h % off;
					break;
				}
			}
			else
				offset = p->h;
			if (m->in_op & FILE_OPINVERSE)
				offset = ~offset;
			break;
		case FILE_BELONG:
			if (nbytes < (offset + 4))
				return 0;
			if (off) {
				switch (m->in_op & FILE_OPS_MASK) {
				case FILE_OPAND:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) &
						 off;
					break;
				case FILE_OPOR:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) |
						 off;
					break;
				case FILE_OPXOR:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) ^
						 off;
					break;
				case FILE_OPADD:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) +
						 off;
					break;
				case FILE_OPMINUS:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) -
						 off;
					break;
				case FILE_OPMULTIPLY:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) *
						 off;
					break;
				case FILE_OPDIVIDE:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) /
						 off;
					break;
				case FILE_OPMODULO:
					offset = (int32_t)((p->hl[0]<<24)|
							 (p->hl[1]<<16)|
							 (p->hl[2]<<8)|
							 (p->hl[3])) %
						 off;
					break;
				}
			} else
				offset = (int32_t)((p->hl[0]<<24)|
						 (p->hl[1]<<16)|
						 (p->hl[2]<<8)|
						 (p->hl[3]));
			if (m->in_op & FILE_OPINVERSE)
				offset = ~offset;
			break;
		case FILE_LELONG:
			if (nbytes < (offset + 4))
				return 0;
			if (off) {
				switch (m->in_op & FILE_OPS_MASK) {
				case FILE_OPAND:
					offset = (int32_t)((p->hl[3]<<24)|
							 (p->hl[2]<<16)|
							 (p->hl[1]<<8)|
							 (p->hl[0])) &
						 off;
					break;
				case FILE_OPOR:
					offset = (int32_t)((p->hl[3]<<24)|
							 (p->hl[2]<<16)|
							 (p->hl[1]<<8)|
							 (p->hl[0])) |
						 off;
					break;
				case FILE_OPXOR:
					offset = (int32_t)((p->hl[3]<<24)|
							 (p->hl[2]<<16)|
							 (p->hl[1]<<8)|
							 (p->hl[0])) ^
						 off;
					break;