Fix size_t cast in read_mac_metadata_blob

The size_t data type on 32 bit systems is smaller than int64_t. Check
the int64_t value before casting to size_t. If the value is too large
then stop operation instead of continuing operation with truncated
value.

Author: ferivoz

libarchive/archive_read_support_format_tar.c

@@ -1396,6 +1396,7 @@ read_mac_metadata_blob(struct archive_read *a, struct tar *tar,
     struct archive_entry *entry, const void *h, size_t *unconsumed)
 {
 	int64_t size;
+	size_t msize;
 	const void *data;
 	const char *p, *name;
 	const wchar_t *wp, *wname;
@@ -1434,6 +1435,11 @@ read_mac_metadata_blob(struct archive_read *a, struct tar *tar,
 
  	/* Read the body as a Mac OS metadata blob. */
 	size = archive_entry_size(entry);
+	msize = (size_t)size;
+	if (size < 0 || (uintmax_t)msize != (uintmax_t)size) {
+		*unconsumed = 0;
+		return (ARCHIVE_FATAL);
+	}
 
 	/*
 	 * TODO: Look beyond the body here to peek at the next header.
@@ -1447,13 +1453,13 @@ read_mac_metadata_blob(struct archive_read *a, struct tar *tar,
 	 * Q: Is the above idea really possible?  Even
 	 * when there are GNU or pax extension entries?
 	 */
-	data = __archive_read_ahead(a, (size_t)size, NULL);
+	data = __archive_read_ahead(a, msize, NULL);
 	if (data == NULL) {
 		*unconsumed = 0;
 		return (ARCHIVE_FATAL);
 	}
-	archive_entry_copy_mac_metadata(entry, data, (size_t)size);
-	*unconsumed = (size_t)((size + 511) & ~ 511);
+	archive_entry_copy_mac_metadata(entry, data, msize);
+	*unconsumed = (msize + 511) & ~ 511;
 	tar_flush_unconsumed(a, unconsumed);
 	return (tar_read_header(a, tar, entry, unconsumed));
 }