feat(reporting): report meta-data information about chunks.

Allow handlers to provide a dict value as part of a ValidChunk metadata
attribute. That dictionnary can contain any relevant metadata
information from the perspective of the handler, but we advise handler
writers to report parsed information such as header values.

This metadata dict is later reported as part of our ChunkReports and
available in the JSON report file if the user requested one.

The idea is to expose metadata to further analysis steps through the
unblob report. For example, a binary analysis toolkit would read the load
address and architecture from a uImage chunk to analyze the file
extracted from that chunk with the right settings.

A note on the 'as_dict' implementation.

The initial idea was to implement it in dissect.cstruct (see
fox-it/dissect.cstruct#29), but due to expected
changes in the project's API I chose to implement it in unblob so we're
not dependent on another project.

tests/test_report.py

@@ -86,6 +86,7 @@ def test_simple_conversion(self):
  end_offset=384,
  size=384,
  is_encrypted=False,
+ metadata={},
  extraction_reports=[],
  )
  )
@@ -135,6 +136,7 @@ def test_simple_conversion(self):
  "handler_name": "zip",
  "chunk_id": "test_basic_conversion:id",
  "is_encrypted": False,
+ "metadata": {},
  "size": 384,
  "start_offset": 0,
  },
@@ -180,63 +182,58 @@ def test_exotic_command_output(self):
  json_text = ProcessResult(results=[task_result]).to_json()
 
  decoded_report = json.loads(json_text)
-
  assert decoded_report == [
  {
- "__typename__": "TaskResult",
+ "task": {
+ "path": "/nonexistent",
+ "depth": 0,
+ "chunk_id": "",
+ "__typename__": "Task",
+ },
  "reports": [
  {
- "__typename__": "ChunkReport",
+ "chunk_id": "test",
+ "handler_name": "fail",
+ "start_offset": 0,
  "end_offset": 256,
+ "size": 256,
+ "is_encrypted": False,
+ "metadata": {},
  "extraction_reports": [
  {
- "__typename__": "ExtractCommandFailedReport",
- "command": "dump all bytes",
- "exit_code": 1,
  "severity": "WARNING",
+ "command": "dump all bytes",
+ "stdout": "\x00\x01\x02\x03\x04\x05\x06\x07\x08"
+ "\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15"
+ '\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$'
+ "%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQR"
+ "STUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
+ "\x7f\udc80\udc81\udc82\udc83\udc84\udc85\udc86"
+ "\udc87\udc88\udc89\udc8a\udc8b\udc8c\udc8d\udc8e"
+ "\udc8f\udc90\udc91\udc92\udc93\udc94\udc95\udc96"
+ "\udc97\udc98\udc99\udc9a\udc9b\udc9c\udc9d\udc9e"
+ "\udc9f\udca0\udca1\udca2\udca3\udca4\udca5\udca6"
+ "\udca7\udca8\udca9\udcaa\udcab\udcac\udcad\udcae"
+ "\udcaf\udcb0\udcb1\udcb2\udcb3\udcb4\udcb5\udcb6"
+ "\udcb7\udcb8\udcb9\udcba\udcbb\udcbc\udcbd\udcbe"
+ "\udcbf\udcc0\udcc1\udcc2\udcc3\udcc4\udcc5\udcc6"
+ "\udcc7\udcc8\udcc9\udcca\udccb\udccc\udccd\udcce"
+ "\udccf\udcd0\udcd1\udcd2\udcd3\udcd4\udcd5\udcd6"
+ "\udcd7\udcd8\udcd9\udcda\udcdb\udcdc\udcdd\udcde"
+ "\udcdf\udce0\udce1\udce2\udce3\udce4\udce5\udce6"
+ "\udce7\udce8\udce9\udcea\udceb\udcec\udced\udcee"
+ "\udcef\udcf0\udcf1\udcf2\udcf3\udcf4\udcf5\udcf6"
+ "\udcf7\udcf8\udcf9\udcfa\udcfb\udcfc\udcfd\udcfe\udcff",
  "stderr": "stdout is pretty strange ;)",
- "stdout": (
- "b'\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07"
- "\\x08\\t\\n\\x0b\\x0c\\r\\x0e\\x0f"
- "\\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x17"
- '\\x18\\x19\\x1a\\x1b\\x1c\\x1d\\x1e\\x1f !"#'
- "$%&\\'()*+,-./0123456789:;<=>?@AB"
- "CDEFGHIJKLMNOPQRSTUVWXYZ[\\\\]^_`a"
- "bcdefghijklmnopqrstuvwxyz{|}~\\x7f"
- "\\x80\\x81\\x82\\x83\\x84\\x85\\x86\\x87"
- "\\x88\\x89\\x8a\\x8b\\x8c\\x8d\\x8e\\x8f"
- "\\x90\\x91\\x92\\x93\\x94\\x95\\x96\\x97"
- "\\x98\\x99\\x9a\\x9b\\x9c\\x9d\\x9e\\x9f"
- "\\xa0\\xa1\\xa2\\xa3\\xa4\\xa5\\xa6\\xa7"
- "\\xa8\\xa9\\xaa\\xab\\xac\\xad\\xae\\xaf"
- "\\xb0\\xb1\\xb2\\xb3\\xb4\\xb5\\xb6\\xb7"
- "\\xb8\\xb9\\xba\\xbb\\xbc\\xbd\\xbe\\xbf"
- "\\xc0\\xc1\\xc2\\xc3\\xc4\\xc5\\xc6\\xc7"
- "\\xc8\\xc9\\xca\\xcb\\xcc\\xcd\\xce\\xcf"
- "\\xd0\\xd1\\xd2\\xd3\\xd4\\xd5\\xd6\\xd7"
- "\\xd8\\xd9\\xda\\xdb\\xdc\\xdd\\xde\\xdf"
- "\\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\xe7"
- "\\xe8\\xe9\\xea\\xeb\\xec\\xed\\xee\\xef"
- "\\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7"
- "\\xf8\\xf9\\xfa\\xfb\\xfc\\xfd\\xfe\\xff"
- "'"
- ),
+ "exit_code": 1,
+ "__typename__": "ExtractCommandFailedReport",
  }
  ],
- "handler_name": "fail",
- "chunk_id": "test",
- "is_encrypted": False,
- "size": 256,
- "start_offset": 0,
+ "__typename__": "ChunkReport",
  }
  ],
  "subtasks": [],
- "task": {
- "__typename__": "Task",
- "chunk_id": "",
- "depth": 0,
- "path": "/nonexistent",
- },
+ "__typename__": "TaskResult",
  }
  ]
 

unblob/handlers/archive/sevenzip.py

@@ -70,4 +70,6 @@ def calculate_chunk(self, file: File, start_offset: int) -> Optional[ValidChunk]
  # We read the signature header here to get the offset to the header database
  first_db_header = start_offset + len(header) + header.next_header_offset
  end_offset = first_db_header + header.next_header_size
- return ValidChunk(start_offset=start_offset, end_offset=end_offset)
+ return ValidChunk(
+ start_offset=start_offset, end_offset=end_offset, metadata=header
+ )

unblob/models.py

@@ -6,6 +6,7 @@
 from typing import List, Optional, Tuple, Type
 
 import attr
+from dissect.cstruct import Instance
 from structlog import get_logger
 
 from .file_utils import Endian, File, InvalidInputFormat, StructParser
@@ -21,6 +22,29 @@
 #
 
 
+def as_dict(obj) -> dict:
+ """Convert a Python class instance to a dictionary."""
+ if isinstance(obj, dict):
+ return obj
+ if isinstance(obj, list):
+ return [as_dict(item) for item in obj] # type: ignore
+ if isinstance(obj, Instance):
+ result = {}
+ for k, v in obj._values.items(): # noqa: SLF001
+ result[k] = v
+ return result
+
+ result = {}
+ for key, value in obj.__dict__.items():
+ if key.startswith("_"):
+ continue
+ if isinstance(value, (list, tuple)):
+ result[key] = [as_dict(item) for item in value]
+ else:
+ result[key] = as_dict(value)
+ return result
+
+
 @attr.define(frozen=True)
 class Task:
  path: Path
@@ -88,6 +112,7 @@ class ValidChunk(Chunk):
 
  handler: "Handler" = attr.ib(init=False, eq=False)
  is_encrypted: bool = attr.ib(default=False)
+ metadata: dict = attr.ib(factory=dict, converter=as_dict)
 
  def extract(self, inpath: Path, outdir: Path):
  if self.is_encrypted:
@@ -108,6 +133,7 @@ def as_report(self, extraction_reports: List[Report]) -> ChunkReport:
  size=self.size,
  handler_name=self.handler.NAME,
  is_encrypted=self.is_encrypted,
+ metadata=self.metadata,
  extraction_reports=extraction_reports,
  )
 
@@ -190,7 +216,7 @@ def default(self, obj):
  try:
  return obj.decode()
  except UnicodeDecodeError:
- return str(obj)
+ return obj.decode("utf-8", errors="surrogateescape")
 
  logger.error("JSONEncoder met a non-JSON encodable value", obj=obj)
  # the usual fail path of custom JSONEncoders is to call the parent and let it fail

unblob/report.py

@@ -181,6 +181,7 @@ class ChunkReport(Report):
  end_offset: int
  size: int
  is_encrypted: bool
+ metadata: dict = attr.ib(factory=dict)
  extraction_reports: List[Report]