jffs2: ignore CRC for inaccurate node types

Ignore CRC for inaccurate node types (e.g. c001 or c002) to fix
extraction of JFFS2 from two different flash dumps of two different
vendors

Signed-off-by: Fabrice Fontaine <[email protected]>

Author: ffontaine

unblob/handlers/filesystem/jffs2.py

@@ -66,13 +66,7 @@ def guess_endian(self, file: File) -> Endian:
 
     def valid_header(self, header: Instance, node_start_offset: int, eof: int) -> bool:
         header_crc = (binascii.crc32(header.dumps()[:-4], -1) ^ -1) & 0xFFFFFFFF
-
-        if header_crc != header.hdr_crc:
-            logger.debug(
-                "node header CRC missmatch",
-                _verbosity=2,
-            )
-            return False
+        check_crc = True
 
         if header.nodetype not in JFFS2_NODETYPES:
             if header.nodetype | JFFS2_NODE_ACCURATE not in JFFS2_NODETYPES:
@@ -81,8 +75,15 @@ def valid_header(self, header: Instance, node_start_offset: int, eof: int) -> bo
                 )
                 return False
             logger.debug(
-                "Not accurate JFFS2 node type", node_type=header.nodetype, _verbosity=2
+                "Not accurate JFFS2 node type, ignore CRC",
+                node_type=header.nodetype,
+                _verbosity=2,
             )
+            check_crc = False
+
+        if check_crc and header_crc != header.hdr_crc:
+            logger.debug("node header CRC missmatch", _verbosity=2)
+            return False
 
         if node_start_offset + header.totlen > eof:
             logger.debug(