Fix inode checksum calculation (#12)

* Switch to crc32c

* Bump version

* Add missing offset, fix checksum logic

* Switch back to crcmod

* Clamp

* Remove unneeded initialization

* Add missing data

* Move to helper

* Normalize imports

Author: Eeems

ext4/extent.py

@@ -2,8 +2,8 @@
 from ctypes import c_uint16
 from ctypes import sizeof
 
-from .struct import Ext4Struct
 from .struct import crc32c
+from .struct import Ext4Struct
 
 
 class ExtentBlocks(object):

ext4/inode.py

@@ -11,8 +11,8 @@
 
 from ._compat import override
 
-from .struct import Ext4Struct
 from .struct import crc32c
+from .struct import Ext4Struct
 from .struct import MagicError
 
 from .enum import EXT4_OS
@@ -189,6 +189,16 @@ def __init__(self, volume, offset, i_no):
         super().__init__(volume, offset)
         self.tree = ExtentTree(self)
 
+    @property
+    def extra_inode_data(self) -> bytes:
+        if not self.has_hi:
+            return b""
+
+        size = sizeof(self)
+        assert size == self.EXT2_GOOD_OLD_INODE_SIZE + self.i_extra_isize
+        _ = self.volume.seek(self.offset + size)
+        return self.volume.read(self.superblock.s_inode_size - size)
+
     @property
     def superblock(self):
         return self.volume.superblock
@@ -248,7 +258,12 @@ def checksum(self):
                 csum = crc32c(b"\0" * Inode.i_checksum_hi.size, csum)
                 offset += Inode.i_checksum_hi.size
 
-            csum = crc32c(data[offset:], csum)
+            csum = crc32c(
+                data[offset:],
+                csum,
+            )
+            if self.superblock.s_inode_size - len(data) > 0:
+                csum = crc32c(self.extra_inode_data, csum)
 
         if not self.has_hi:
             csum &= 0xFFFF

ext4/xattr.py

@@ -5,12 +5,14 @@
 from ctypes import c_uint8
 from ctypes import sizeof
 
-from .struct import Ext4Struct
-from .struct import crc32c
-from .enum import EXT4_FL
-from .enum import EXT4_FEATURE_INCOMPAT
 from ._compat import override
 
+from .enum import EXT4_FEATURE_INCOMPAT
+from .enum import EXT4_FL
+
+from .struct import crc32c
+from .struct import Ext4Struct
+
 
 class ExtendedAttributeError(Exception):
     pass

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "ext4"
-version = "1.2.1"
+version = "1.2.2"
 authors = [
   { name="Eeems", email="eeems@eeems.email" },
 ]

test.py

@@ -65,6 +65,18 @@ def _assert(source: str):
 
         # Extract specific file
         volume = ext4.Volume(f, offset=offset)
+
+        try:
+            print("Validate root inode: ", end="")
+            volume.root.validate()
+            print("pass")
+
+        except ext4.struct.ChecksumError as e:
+            FAILED = True
+            print("fail")
+            print("  ", end="")
+            print(e)
+
         inode = cast(ext4.File, volume.inode_at("/test.txt"))
         _assert("isinstance(inode, ext4.File)")
         b = inode.open()