Replace binascii and struct with native Python methods (#2582)

* refactor: replace binascii with bytes for hex conversions

Signed-off-by: vibhatsu <maulikbarot2915@gmail.com>

* refactor: replace struct unpacking with bytes conversion

Signed-off-by: vibhatsu <maulikbarot2915@gmail.com>

* simplify byte extraction for ELF header

Signed-off-by: vibhatsu <maulikbarot2915@gmail.com>

* Revert "refactor: replace struct unpacking with bytes conversion"

This reverts commit 483f8c9a85.

* update CHANGELOG

Signed-off-by: vibhatsu <maulikbarot2915@gmail.com>

---------

Signed-off-by: vibhatsu <maulikbarot2915@gmail.com>
Co-authored-by: Willi Ballenthin <wballenthin@google.com>

CHANGELOG.md

@@ -31,6 +31,7 @@
 - strings: add type hints and fix uncovered bugs @williballenthin #2555
 - elffile: handle symbols without a name @williballenthin #2553
 - project: remove pytest-cov that wasn't used @williballenthin @2491
+- replace binascii methods with native Python methods @v1bh475u #2582
 - rules: scopes can now have subscope blocks with the same scope @williballenthin #2584
 
 ### capa Explorer Web

capa/features/extractors/cape/models.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import binascii
 from typing import Any, Union, Literal, Optional, Annotated, TypeAlias
 
 from pydantic import Field, BaseModel, ConfigDict
@@ -27,7 +26,7 @@ def validate_hex_int(value):
 
 
 def validate_hex_bytes(value):
-    return binascii.unhexlify(value) if isinstance(value, str) else value
+    return bytes.fromhex(value) if isinstance(value, str) else value
 
 
 HexInt = Annotated[int, BeforeValidator(validate_hex_int)]

capa/features/freeze/features.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import binascii
 from typing import Union, Literal, Optional, Annotated
 
 from pydantic import Field, BaseModel, ConfigDict
@@ -85,7 +84,7 @@ class FeatureModel(BaseModel):
             return capa.features.insn.Number(self.number, description=self.description)
 
         elif isinstance(self, BytesFeature):
-            return capa.features.common.Bytes(binascii.unhexlify(self.bytes), description=self.description)
+            return capa.features.common.Bytes(bytes.fromhex(self.bytes), description=self.description)
 
         elif isinstance(self, OffsetFeature):
             return capa.features.insn.Offset(self.offset, description=self.description)
@@ -191,7 +190,7 @@ def feature_from_capa(f: capa.features.common.Feature) -> "Feature":
     elif isinstance(f, capa.features.common.Bytes):
         buf = f.value
         assert isinstance(buf, bytes)
-        return BytesFeature(bytes=binascii.hexlify(buf).decode("ascii"), description=f.description)
+        return BytesFeature(bytes=bytes.hex(buf), description=f.description)
 
     elif isinstance(f, capa.features.insn.Offset):
         assert isinstance(f.value, int)

scripts/import-to-ida.py

@@ -36,7 +36,6 @@ Check the output window for any errors, and/or the summary of changes.
 """
 
 import logging
-import binascii
 from pathlib import Path
 
 import ida_nalt
@@ -85,7 +84,7 @@ def main():
     #
     # see: https://github.com/idapython/bin/issues/11
     a = meta.sample.md5.lower()
-    b = binascii.hexlify(ida_nalt.retrieve_input_file_md5()).decode("ascii").lower()
+    b = bytes.hex(ida_nalt.retrieve_input_file_md5()).lower()
     if not a.startswith(b):
         logger.error("sample mismatch")
         return -2

tests/fixtures.py

@@ -13,7 +13,6 @@
 # limitations under the License.
 
 
-import binascii
 import contextlib
 import collections
 from pathlib import Path
@@ -942,17 +941,17 @@ FEATURE_PRESENCE_TESTS = sorted(
         # insn/string, direct memory reference
         ("mimikatz", "function=0x46D6CE", capa.features.common.String("(null)"), True),
         # insn/bytes
-        ("mimikatz", "function=0x401517", capa.features.common.Bytes(binascii.unhexlify("CA3B0E000000F8AF47")), True),
+        ("mimikatz", "function=0x401517", capa.features.common.Bytes(bytes.fromhex("CA3B0E000000F8AF47")), True),
-        ("mimikatz", "function=0x404414", capa.features.common.Bytes(binascii.unhexlify("0180000040EA4700")), True),
+        ("mimikatz", "function=0x404414", capa.features.common.Bytes(bytes.fromhex("0180000040EA4700")), True),
         # don't extract byte features for obvious strings
         ("mimikatz", "function=0x40105D", capa.features.common.Bytes("SCardControl".encode("utf-16le")), False),
         ("mimikatz", "function=0x40105D", capa.features.common.Bytes("SCardTransmit".encode("utf-16le")), False),
         ("mimikatz", "function=0x40105D", capa.features.common.Bytes("ACR  > ".encode("utf-16le")), False),
         ("mimikatz", "function=0x40105D", capa.features.common.Bytes("nope".encode("ascii")), False),
         # push    offset aAcsAcr1220 ; "ACS..." -> where ACS == 41 00 43 00 == valid pointer to middle of instruction
-        ("mimikatz", "function=0x401000", capa.features.common.Bytes(binascii.unhexlify("FDFF59F647")), False),
+        ("mimikatz", "function=0x401000", capa.features.common.Bytes(bytes.fromhex("FDFF59F647")), False),
         # IDA features included byte sequences read from invalid memory, fixed in #409
-        ("mimikatz", "function=0x44570F", capa.features.common.Bytes(binascii.unhexlify("FF" * 256)), False),
+        ("mimikatz", "function=0x44570F", capa.features.common.Bytes(bytes.fromhex("FF" * 256)), False),
         # insn/bytes, pointer to string bytes
         ("mimikatz", "function=0x44EDEF", capa.features.common.Bytes("INPUTEVENT".encode("utf-16le")), False),
         # insn/characteristic(nzxor)

tests/test_binexport_features.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import binascii
 from typing import cast
 
 import pytest
@@ -302,7 +301,7 @@ FEATURE_PRESENCE_TESTS_BE2_ELF_AARCH64 = sorted(
         (
             "d1e650.ghidra.be2",
             "function=0x1165a4",
-            capa.features.common.Bytes(binascii.unhexlify("E405B89370BA6B419CD7925275BF6FCC1E8360CC")),
+            capa.features.common.Bytes(bytes.fromhex("E405B89370BA6B419CD7925275BF6FCC1E8360CC")),
             True,
         ),
         # # don't extract byte features for obvious strings

tests/test_ida_features.py

@@ -60,7 +60,6 @@ import io
 import sys
 import inspect
 import logging
-import binascii
 import traceback
 from pathlib import Path
 
@@ -86,7 +85,7 @@ def check_input_file(wanted):
     except UnicodeDecodeError:
         # in IDA 7.5 or so, GetInputFileMD5 started returning raw binary
         # rather than the hex digest
-        found = binascii.hexlify(idautils.GetInputFileMD5()[:15]).decode("ascii").lower()
+        found = bytes.hex(idautils.GetInputFileMD5()[:15]).lower()
 
     if not wanted.startswith(found):
         raise RuntimeError(f"please run the tests against sample with MD5: `{wanted}`")