adding instruction feature extractors

.github/mypy/mypy.ini

@@ -74,3 +74,6 @@ ignore_missing_imports = True
 
 [mypy-elftools.*]
 ignore_missing_imports = True
+
+[mypy-dncil.*]
+ignore_missing_imports = True

capa/features/extractors/dotnet/helpers.py

@@ -0,0 +1,71 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from dnfile.mdtable import MemberRefRow
+    from dnfile.mdtable import MethodDefRow
+    from dnfile import dnPE
+
+import dnfile
+from dnfile.enums import MetadataTables
+from dncil.cil.body import CilMethodBody
+from dncil.clr.token import Token, InvalidToken
+from dncil.cil.body.reader import CilMethodBodyReaderBase
+
+# key indexes to dotnet metadata tables
+DOTNET_META_TABLES_BY_INDEX = {table.value: table.name for table in MetadataTables}
+
+
+class DnfileMethodBodyReader(CilMethodBodyReaderBase):
+    def __init__(self, pe: dnfile.dnPE, row: MethodDefRow):
+        """ """
+        self.pe = pe
+        self.rva = self.pe.get_offset_from_rva(row.Rva)
+
+    def read(self, n):
+        """ """
+        data = self.pe.get_data(self.pe.get_rva_from_offset(self.rva), n)
+        self.rva += n
+        return data
+
+    def tell(self):
+        """ """
+        return self.rva
+
+    def seek(self, rva):
+        """ """
+        self.rva = rva
+
+    def get_token(self, value, is_str=False):
+        """ """
+        token = Token(value)
+
+        if is_str:
+            return self.pe.net.user_strings.get_us(token.rid).value
+
+        table_name = DOTNET_META_TABLES_BY_INDEX.get(token.table, "")
+        if not table_name:
+            # table_index is not valid
+            return InvalidToken(token.value)
+
+        table = getattr(self.pe.net.mdtables, table_name, None)
+        if table is None:
+            # table index is valid but table is not present
+            return InvalidToken(token.value)
+
+        try:
+            return table.rows[token.rid - 1]
+        except IndexError:
+            # table index is valid but row index is not valid
+            return InvalidToken(token.value)
+
+
+def read_dotnet_method_body(dn: dnPE, row: MethodDefRow) -> CilMethodBody:
+    """ """
+    return CilMethodBody(DnfileMethodBodyReader(dn, row))
+
+
+def get_imported_class_name(row: MemberRefRow) -> str:
+    """ """
+    return f"{row.Class.row.TypeNamespace}.{row.Class.row.TypeName}"

capa/features/extractors/dotnet/insn.py

@@ -0,0 +1,97 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Generator, Union, Tuple, List, Callable
+
+if TYPE_CHECKING:
+    from dncil.cil.instruction import Instruction
+    from dncil.cil.body import CilMethodBody
+
+import dncil
+import dnfile
+from dncil.cil.error import MethodBodyFormatError
+from dncil.cil.opcode import OpCodes
+
+import capa.features.extractors.helpers
+import capa.features.extractors.dotnet.helpers
+from capa.features.insn import API, Number
+from capa.features.common import String
+
+
+def extract_insn_api_features(f: CilMethodBody, insn: Instruction) -> Generator[Tuple[API, int], None, None]:
+    """parse instruction API features
+
+    see https://www.ntcore.com/files/dotnetformat.htm
+
+    10 - MemberRef Table
+        Each row represents an imported method.
+            Class (index into the TypeRef, ModuleRef, MethodDef, TypeSpec or TypeDef tables)
+    01 - TypeRef Table
+        Each row represents an imported class, its namespace and the assembly which contains it.
+            TypeName (index into String heap)
+            TypeNamespace (index into String heap)
+    """
+    if insn.opcode in (OpCodes.Call, OpCodes.Callvirt, OpCodes.Jmp, OpCodes.Calli):
+        if isinstance(insn.operand, dnfile.mdtable.MemberRefRow):
+            if isinstance(insn.operand.Class.row, (dnfile.mdtable.TypeRefRow,)):
+                class_name = capa.features.extractors.dotnet.helpers.get_imported_class_name(insn.operand)
+                method_name = insn.operand.Name
+                yield API(f"{class_name}::{method_name}"), insn.offset
+
+
+def extract_insn_number_features(f: CilMethodBody, insn: Instruction) -> Generator[Tuple[Number, int], None, None]:
+    """parse instruction number features"""
+    if insn.is_ldc():
+        yield Number(insn.get_ldc()), insn.offset
+
+
+def extract_insn_string_features(f: CilMethodBody, insn: Instruction) -> Generator[Tuple[String, int], None, None]:
+    """parse instruction string features"""
+    if insn.is_ldstr():
+        yield String(insn.operand), insn.offset
+
+
+def extract_features(f: CilMethodBody, insn: Instruction) -> Generator[Tuple[Union[API, String, Number], int], None, None]:
+    """extract instruction features"""
+    for inst_handler in INSTRUCTION_HANDLERS:
+        for (feature, ea) in inst_handler(f, insn):
+            yield feature, ea
+
+
+INSTRUCTION_HANDLERS = (
+    extract_insn_api_features,
+    extract_insn_number_features,
+    extract_insn_string_features,
+)
+
+
+def main(args):
+    """ """
+    dn = dnfile.dnPE(args.path)
+
+    features = []
+    for row in dn.net.mdtables.MethodDef:
+        if row.ImplFlags.miIL:
+            try:
+                body = read_dotnet_method_body(dn, row)
+            except MethodBodyFormatError as e:
+                print(e)
+                continue
+
+        for insn in body.instructions:
+            features.extend(list(extract_features(body, insn)))
+
+    import pprint
+
+    pprint.pprint(features)
+
+
+if __name__ == "__main__":
+    """ """
+    import argparse
+
+    from capa.features.extractors.dotnet.helpers import read_dotnet_method_body
+
+    parser = argparse.ArgumentParser(prog="parse instruction features from .NET PE")
+    parser.add_argument("path", type=str, help="full path to .NET PE")
+
+    main(parser.parse_args())