#!/usr/bin/env python2 """ Copyright (C) 2020 Mandiant, Inc. All Rights Reserved. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at: [package root]/LICENSE.txt Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. show-features Show the features that capa extracts from the given sample, to assist with the development of rules. If you have a function with a capability that you'd like to detect, you can run this tool and grep for the function/basic block/instruction addresses to see what capa picks up. This way, you can verify that capa successfully notices the features you'd reference. Example:: $ python scripts/show-features.py /tmp/suspicious.dll_ ... file: 0x10004e4d: export(__entry) file: 0x10004706: export(Install) file: 0x10004c2b: export(uninstallA) file: 0x10005034: import(kernel32.GetStartupInfoA) file: 0x10005034: import(GetStartupInfoA) file: 0x10005048: import(kernel32.SetLastError) file: 0x00004e10: string(Y29ubmVjdA==) file: 0x00004e28: string(practicalmalwareanalysis.com) file: 0x00004e68: string(serve.html) file: 0x00004eb8: string(dW5zdXBwb3J0) file: 0x00004ec8: string(c2xlZXA=) func: 0x100012c2: characteristic(calls to) func: 0x10001000: characteristic(loop) bb : 0x10001000: basic block insn: 0x10001000: mnemonic(push) insn: 0x10001001: mnemonic(push) insn: 0x10001002: mnemonic(push) insn: 0x10001003: mnemonic(push) insn: 0x10001004: mnemonic(push) insn: 0x10001005: mnemonic(push) insn: 0x10001006: mnemonic(xor) insn: 0x10001008: number(0x1) insn: 0x10001008: mnemonic(mov) bb : 0x1000100a: basic block bb : 0x1000100a: characteristic(tight loop) insn: 0x1000100a: mnemonic(movzx) insn: 0x1000100d: mnemonic(mov) insn: 0x1000100f: offset(0x1000A7C8) insn: 0x1000100f: mnemonic(mov) insn: 0x10001015: offset(0x100075C8) insn: 0x10001015: mnemonic(mov) insn: 0x1000101b: mnemonic(mov) insn: 0x1000101d: number(0x80) insn: 0x1000101d: mnemonic(and) insn: 0x10001020: mnemonic(neg) insn: 0x10001022: mnemonic(sbb) insn: 0x10001024: number(0x1B) insn: 0x10001024: mnemonic(and) insn: 0x10001027: number(0x1) insn: 0x10001027: mnemonic(shl) ... """ import os import sys import logging import os.path import argparse import capa.main import capa.rules import capa.engine import capa.helpers import capa.features import capa.exceptions import capa.render.verbose as v import capa.features.common import capa.features.freeze import capa.features.address import capa.features.extractors.base_extractor from capa.helpers import log_unsupported_runtime_error logger = logging.getLogger("capa.show-features") def format_address(addr: capa.features.address.Address) -> str: return v.format_address(capa.features.freeze.Address.from_capa((addr))) def main(argv=None): if argv is None: argv = sys.argv[1:] parser = argparse.ArgumentParser(description="Show the features that capa extracts from the given sample") capa.main.install_common_args(parser, wanted={"format", "os", "sample", "signatures", "backend"}) parser.add_argument("-F", "--function", type=str, help="Show features for specific function") args = parser.parse_args(args=argv) capa.main.handle_common_args(args) try: taste = capa.helpers.get_file_taste(args.sample) except IOError as e: logger.error("%s", str(e)) return -1 try: sig_paths = capa.main.get_signatures(args.signatures) except IOError as e: logger.error("%s", str(e)) return -1 if (args.format == "freeze") or ( args.format == capa.features.common.FORMAT_AUTO and capa.features.freeze.is_freeze(taste) ): with open(args.sample, "rb") as f: extractor = capa.features.freeze.load(f.read()) else: should_save_workspace = os.environ.get("CAPA_SAVE_WORKSPACE") not in ("0", "no", "NO", "n", None) try: extractor = capa.main.get_extractor( args.sample, args.format, args.os, args.backend, sig_paths, should_save_workspace ) except capa.exceptions.UnsupportedFormatError: capa.helpers.log_unsupported_format_error() return -1 except capa.exceptions.UnsupportedRuntimeError: log_unsupported_runtime_error() return -1 for feature, addr in extractor.extract_global_features(): print(f"global: {format_address(addr)}: {feature}") if not args.function: for feature, addr in extractor.extract_file_features(): print(f"file: {format_address(addr)}: {feature}") function_handles = tuple(extractor.get_functions()) if args.function: if args.format == "freeze": # TODO fix function_handles = tuple(filter(lambda fh: fh.address == args.function, function_handles)) else: function_handles = tuple(filter(lambda fh: format_address(fh.address) == args.function, function_handles)) if args.function not in [format_address(fh.address) for fh in function_handles]: print(f"{args.function} not a function") return -1 if len(function_handles) == 0: print(f"{args.function} not a function") return -1 print_features(function_handles, extractor) return 0 def ida_main(): import idc import capa.features.extractors.ida.extractor function = idc.get_func_attr(idc.here(), idc.FUNCATTR_START) print(f"getting features for current function {hex(function)}") extractor = capa.features.extractors.ida.extractor.IdaFeatureExtractor() if not function: for feature, addr in extractor.extract_file_features(): print(f"file: {format_address(addr)}: {feature}") return function_handles = tuple(extractor.get_functions()) if function: function_handles = tuple(filter(lambda fh: fh.inner.start_ea == function, function_handles)) if len(function_handles) == 0: print(f"{hex(function)} not a function") return -1 print_features(function_handles, extractor) return 0 def print_features(functions, extractor: capa.features.extractors.base_extractor.FeatureExtractor): for f in functions: if extractor.is_library_function(f.address): function_name = extractor.get_function_name(f.address) logger.debug("skipping library function %s (%s)", format_address(f.address), function_name) continue print(f"func: {format_address(f.address)}") for feature, addr in extractor.extract_function_features(f): if capa.features.common.is_global_feature(feature): continue if f.address != addr: print(f" func: {format_address(f.address)}: {feature} -> {format_address(addr)}") else: print(f" func: {format_address(f.address)}: {feature}") for bb in extractor.get_basic_blocks(f): for feature, addr in extractor.extract_basic_block_features(f, bb): if capa.features.common.is_global_feature(feature): continue if bb.address != addr: print(f" bb: {format_address(bb.address)}: {feature} -> {format_address(addr)}") else: print(f" bb: {format_address(bb.address)}: {feature}") for insn in extractor.get_instructions(f, bb): for feature, addr in extractor.extract_insn_features(f, bb, insn): if capa.features.common.is_global_feature(feature): continue try: if insn.address != addr: print( f" insn: {format_address(f.address)}: {format_address(insn.address)}: {feature} -> {format_address(addr)}" ) else: print(f" insn: {format_address(insn.address)}: {feature}") except UnicodeEncodeError: # may be an issue while piping to less and encountering non-ascii characters continue if __name__ == "__main__": if capa.main.is_runtime_ida(): ida_main() else: sys.exit(main())