Take disklabel table offset into account (#21)

dissect/volume/disk/schemes/bsd.py

@@ -1,3 +1,6 @@
+# Reference:
+# - https://github.com/freebsd/freebsd-src/blob/main/sys/geom/part/g_part_bsd.c
+
 import io
 from typing import BinaryIO, Iterator
 from uuid import UUID
@@ -319,19 +322,36 @@ def __init__(self, fh: BinaryIO, sector_size: int = 512):
         self.partitions = list(self._partitions())
 
     def _partitions(self) -> Iterator[Partition]:
+        table_offset = 0
+        if self.type == 32:
+            # Get the table offset first
+            self.fh.seek(self._partitions_offset + (c_bsd.BSD_PART_RAW * len(c_bsd.partition)))
+            table_offset = c_bsd.partition(self.fh).p_offset
+
         self.fh.seek(self._partitions_offset)
         for i in range(self.disklabel.d_npartitions):
             if self.type == 32:
                 partition = c_bsd.partition(self.fh)
-                if partition.p_fstype == 0:
+                if i == c_bsd.BSD_PART_RAW:
+                    # Skip internal partition
+                    continue
+
+                if partition.p_size == 0 or partition.p_fstype == 0:
                     continue
 
-                offset = partition.p_offset * self.sector_size
+                if partition.p_offset < table_offset:
+                    continue
+
+                offset = (partition.p_offset - table_offset) * self.sector_size
                 size = partition.p_size * self.sector_size
                 guid = None
             elif self.type == 64:
                 partition = c_bsd.partition64(self.fh)
-                if (partition.p_boffset == 0 and partition.p_bsize) or partition.p_fstype == 0:
+                if i == c_bsd.BSD_PART_RAW:
+                    # Skip internal partition
+                    continue
+
+                if (partition.p_boffset == 0 and partition.p_bsize == 0) or partition.p_fstype == 0:
                     continue
 
                 offset = partition.p_boffset