capa/scripts/show-features.py

#!/usr/bin/env python2
"""
Copyright (C) 2023 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 argparse
from typing import Tuple
from pathlib import Path

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.pefile
import capa.features.extractors.base_extractor
from capa.helpers import log_unsupported_runtime_error
from capa.features.extractors.base_extractor import FunctionHandle

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)

    if args.function and args.backend == "pefile":
        print("pefile backend does not support extracting function features")
        return -1

    try:
        taste = capa.helpers.get_file_taste(Path(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)
    ):
        extractor = capa.features.freeze.load(Path(args.sample).read_bytes())
    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[FunctionHandle, ...]
    if isinstance(extractor, capa.features.extractors.pefile.PefileFeatureExtractor):
        # pefile extractor doesn't extract function features
        function_handles = ()
    else:
        function_handles = tuple(extractor.get_functions())

    if args.function:
        if args.format == "freeze":
            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 ghidra_main():
    import capa.features.extractors.ghidra.extractor

    extractor = capa.features.extractors.ghidra.extractor.GhidraFeatureExtractor()

    for feature, addr in extractor.extract_file_features():
        print(f"file: {format_address(addr)}: {feature}")

    function_handles = tuple(extractor.get_functions())

    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.helpers.is_runtime_ida():
        ida_main()
    elif capa.helpers.is_runtime_ghidra():
        ghidra_main()
    else:
        sys.exit(main())