unpacker: add FIT image support

fact_extractor/plugins/unpacking/uboot/code/fit.py

@@ -0,0 +1,53 @@
+"""
+This plugin unpacks Flattened Image Trees.
+"""
+
+from pathlib import Path
+
+import libfdt as fdt
+from common_helper_files import write_binary_to_file
+
+NAME = 'FIT'
+MIME_PATTERNS = ['linux/device-tree']
+VERSION = '0.1'
+
+
+def unpack_function(file_path, tmp_dir):
+    """
+    file_path specifies the input file.
+    tmp_dir must be used to store the extracted files.
+    Optional: Return a dict with meta information
+    """
+
+    file = Path(file_path)
+
+    try:
+        with file.open('rb') as f:
+            fit_data = f.read()
+
+        dtb = fdt.Fdt(fit_data)
+        root_offset = dtb.path_offset('/')
+        subnode_offset = dtb.first_subnode(root_offset)
+        while True:
+            try:
+                component_offset = dtb.first_subnode(subnode_offset)
+                while True:
+                    try:
+                        outfile = Path(tmp_dir) / dtb.get_name(component_offset)
+                        write_binary_to_file(bytes(dtb.getprop(component_offset, 'data')), outfile)
+                        component_offset = dtb.next_subnode(component_offset)
+                    except fdt.FdtException:
+                        break
+                subnode_offset = dtb.next_subnode(subnode_offset)
+            except fdt.FdtException:
+                break
+    except OSError as io_error:
+        return {'output': f'failed to read file: {io_error!s}'}
+
+    return {'output': 'successfully unpacked FIT image'}
+
+
+# ----> Do not edit below this line <----
+def setup(unpack_tool):
+    for item in MIME_PATTERNS:
+        unpack_tool.register_plugin(item, (unpack_function, NAME, VERSION))

fact_extractor/plugins/unpacking/uboot/test/test_plugin_fit.py

@@ -0,0 +1,23 @@
+from pathlib import Path
+
+from test.unit.unpacker.test_unpacker import TestUnpackerBase
+
+TEST_DATA_DIR = Path(__file__).parent / 'data'
+
+EXPECTED_FILE_COUNT = 3
+
+
+class TestFITUnpacker(TestUnpackerBase):
+    def test_unpacker_selection_generic(self):
+        self.check_unpacker_selection('linux/device-tree', 'FIT')
+
+    def test_extraction(self):
+        test_file_path = Path(TEST_DATA_DIR) / 'fit.itb'
+        extracted_files, meta_data = self.unpacker.extract_files_from_file(str(test_file_path), self.tmp_dir.name)
+
+        assert meta_data['plugin_used'] == 'FIT', 'wrong plugin applied'
+
+        assert len(extracted_files) == EXPECTED_FILE_COUNT, 'not all files extracted'
+        assert all(
+            Path(element).name in ['kernel', 'fdt', 'rootfs'] for element in extracted_files
+        ), 'not all files extracted'

requirements-unpackers.txt

@@ -36,3 +36,4 @@ bincopy~=20.0.0
 extract-dtb~=1.2.3
 # uefi
 uefi-firmware~=1.11
+pylibfdt ~= 1.7.1