capa/tests/test_rules_insn_scope.py

# Copyright 2022 Google LLC
#
# 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
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# 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.


import textwrap

import pytest

import capa.rules


def test_rule_scope_instruction():
    capa.rules.Rule.from_yaml(textwrap.dedent("""
            rule:
                meta:
                    name: test rule
                    scopes:
                        static: instruction
                        dynamic: unsupported
                features:
                - and:
                    - mnemonic: mov
                    - arch: i386
                    - os: windows
            """))

    with pytest.raises(capa.rules.InvalidRule):
        capa.rules.Rule.from_yaml(textwrap.dedent("""
                rule:
                    meta:
                        name: test rule
                        scopes:
                            static: instruction
                            dynamic: unsupported
                    features:
                        - characteristic: embedded pe
                """))


def test_rule_subscope_instruction():
    rules = capa.rules.RuleSet([capa.rules.Rule.from_yaml(textwrap.dedent("""
                    rule:
                        meta:
                            name: test rule
                            scopes:
                                static: function
                                dynamic: process
                        features:
                        - and:
                            - instruction:
                                - and:
                                    - mnemonic: mov
                                    - arch: i386
                                    - os: windows
                    """))])
    # the function rule scope will have one rules:
    #  - `test rule`
    assert len(rules.function_rules) == 1

    # the insn rule scope have one rule:
    #  - the rule on which `test rule` depends
    assert len(rules.instruction_rules) == 1


def test_scope_instruction_implied_and():
    capa.rules.Rule.from_yaml(textwrap.dedent("""
            rule:
                meta:
                    name: test rule
                    scopes:
                        static: function
                        dynamic: process
                features:
                  - and:
                    - instruction:
                      - mnemonic: mov
                      - arch: i386
                      - os: windows
            """))


def test_scope_instruction_description():
    capa.rules.Rule.from_yaml(textwrap.dedent("""
            rule:
                meta:
                    name: test rule
                    scopes:
                        static: function
                        dynamic: process
                features:
                  - and:
                    - instruction:
                      - description: foo
                      - mnemonic: mov
                      - arch: i386
                      - os: windows
            """))

    capa.rules.Rule.from_yaml(textwrap.dedent("""
            rule:
                meta:
                    name: test rule
                    scopes:
                        static: function
                        dynamic: process
                features:
                  - and:
                    - instruction:
                      - description: foo
                      - mnemonic: mov
                      - arch: i386
                      - os: windows
            """))