fix(handlers): improve squashfs extraction by providing endianness explicitly.

Sasquatch does not switch to the other endianness when the current
endianness is not valid on some specific sample from Netgear such as
https://www.downloads.netgear.com/files/GDC/WNR3500Lv2/WNR3500Lv2-V1.2.0.40_40.0.80.zip

Improved by creating a custom Extractor that is just a wrapper around
Command that detects the file endianness and provides either '-le' or
'-be' endianness options to sasquatch.

Author: qkaiser

unblob/handlers/filesystem/squashfs.py

@@ -14,12 +14,43 @@
 PAD_SIZES = [4_096, 1_024]
 
 
+class SquashFSExtractor(Extractor):
+    EXECUTABLE = "sasquatch"
+
+    def __init__(self, big_endian_magic: int):
+        self.big_endian_magic = big_endian_magic
+
+    def extract(self, inpath: Path, outdir: Path):
+        with File.from_path(inpath) as file:
+            endian = get_endian(file, self.big_endian_magic)
+
+        commands_args = []
+
+        if endian == Endian.BIG:
+            commands_args.append("-be")
+        else:
+            commands_args.append("-le")
+
+        commands_args.extend(
+            [
+                "-no-exit-code",
+                "-f",
+                "-d",
+                "{outdir}",
+                "{inpath}",
+            ]
+        )
+        extractor = Command(self.EXECUTABLE, *commands_args)
+        extractor.extract(inpath, outdir)
+
+    def get_dependencies(self) -> List[str]:
+        return [self.EXECUTABLE]
+
+
 class _SquashFSBase(StructHandler):
     BIG_ENDIAN_MAGIC = 0x73_71_73_68
 
-    EXTRACTOR = Command(
-        "sasquatch", "-no-exit-code", "-f", "-d", "{outdir}", "{inpath}"
-    )
+    EXTRACTOR = SquashFSExtractor(0x73_71_73_68)
 
     def calculate_chunk(self, file: File, start_offset: int) -> Optional[ValidChunk]:
         file.seek(start_offset)
@@ -145,6 +176,8 @@ class SquashFSv3DDWRTHandler(SquashFSv3Handler):
 
     BIG_ENDIAN_MAGIC = 0x74_71_73_68
 
+    EXTRACTOR = SquashFSExtractor(0x74_71_73_68)
+
     PATTERNS = [
         HexString(
             """
@@ -170,6 +203,8 @@ class SquashFSv3BroadcomHandler(SquashFSv3Handler):
 
     BIG_ENDIAN_MAGIC = 0x71_73_68_73
 
+    EXTRACTOR = SquashFSExtractor(0x71_73_68_73)
+
     PATTERNS = [
         HexString(
             """
@@ -196,6 +231,8 @@ class SquashFSv3NSHandler(SquashFSv3Handler):
 
     BIG_ENDIAN_MAGIC = 0x73_71_6C_7A
 
+    EXTRACTOR = SquashFSExtractor(0x73_71_6C_7A)
+
     PATTERNS = [
         HexString(
             """