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https://github.com/mandiant/capa.git
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64124c0b64
Get rid of `True` in characteristic (rules, output and json) as it is implicit. This way, the same syntax is used for characteristic as for the rest of the features. Co-authored-by: William Ballenthin <william.ballenthin@fireeye.com>
500 lines
15 KiB
Python
500 lines
15 KiB
Python
import textwrap
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import pytest
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import capa.rules
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from capa.features.insn import Number, Offset
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def test_rule_ctor():
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r = capa.rules.Rule('test rule', capa.rules.FUNCTION_SCOPE, Number(1), {})
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assert r.evaluate({Number(0): {1}}) == False
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assert r.evaluate({Number(1): {1}}) == True
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def test_rule_yaml():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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author: user@domain.com
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scope: function
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examples:
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- foo1234
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- bar5678
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features:
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- and:
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- number: 1
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- number: 2
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''')
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r = capa.rules.Rule.from_yaml(rule)
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assert r.evaluate({Number(0): {1}}) == False
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assert r.evaluate({Number(0): {1}, Number(1): {1}}) == False
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assert r.evaluate({Number(0): {1}, Number(1): {1}, Number(2): {1}}) == True
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assert r.evaluate({Number(0): {1}, Number(1): {1}, Number(2): {1}, Number(3): {1}}) == True
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def test_rule_yaml_complex():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- or:
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- and:
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- number: 1
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- number: 2
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- or:
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- number: 3
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- 2 or more:
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- number: 4
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- number: 5
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- number: 6
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''')
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r = capa.rules.Rule.from_yaml(rule)
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assert r.evaluate({Number(5): {1}, Number(6): {1}, Number(7): {1}, Number(8): {1}}) == True
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assert r.evaluate({Number(6): {1}, Number(7): {1}, Number(8): {1}}) == False
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def test_rule_yaml_not():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- and:
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- number: 1
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- not:
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- number: 2
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''')
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r = capa.rules.Rule.from_yaml(rule)
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assert r.evaluate({Number(1): {1}}) == True
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assert r.evaluate({Number(1): {1}, Number(2): {1}}) == False
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def test_rule_yaml_count():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- count(number(100)): 1
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''')
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r = capa.rules.Rule.from_yaml(rule)
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assert r.evaluate({Number(100): {}}) == False
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assert r.evaluate({Number(100): {1}}) == True
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assert r.evaluate({Number(100): {1, 2}}) == False
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def test_rule_yaml_count_range():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- count(number(100)): (1, 2)
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''')
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r = capa.rules.Rule.from_yaml(rule)
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assert r.evaluate({Number(100): {}}) == False
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assert r.evaluate({Number(100): {1}}) == True
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assert r.evaluate({Number(100): {1, 2}}) == True
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assert r.evaluate({Number(100): {1, 2, 3}}) == False
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def test_invalid_rule_feature():
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with pytest.raises(capa.rules.InvalidRule):
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- foo: true
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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scope: file
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features:
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- characteristic: nzxor
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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scope: function
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features:
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- characteristic: embedded pe
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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scope: basic block
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features:
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- characteristic: embedded pe
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'''))
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def test_lib_rules():
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rules = capa.rules.RuleSet([
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: a lib rule
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lib: true
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features:
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- api: CreateFileA
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: a standard rule
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lib: false
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features:
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- api: CreateFileW
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''')),
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])
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assert len(rules.function_rules) == 1
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def test_subscope_rules():
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rules = capa.rules.RuleSet([
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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scope: file
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features:
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- and:
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- characteristic: embedded pe
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- function:
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- and:
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- characteristic: nzxor
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- characteristic: switch
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'''))
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])
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# the file rule scope will have one rules:
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# - `test rule`
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assert len(rules.file_rules) == 1
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# the function rule scope have one rule:
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# - the rule on which `test rule` depends
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assert len(rules.function_rules) == 1
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def test_duplicate_rules():
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with pytest.raises(capa.rules.InvalidRule):
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rules = capa.rules.RuleSet([
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule-name
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features:
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- api: CreateFileA
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule-name
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features:
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- api: CreateFileW
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''')),
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])
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def test_missing_dependency():
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with pytest.raises(capa.rules.InvalidRule):
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rules = capa.rules.RuleSet([
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: dependent rule
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features:
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- match: missing rule
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''')),
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])
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def test_invalid_rules():
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- characteristic: number(1)
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- characteristic: count(number(100))
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'''))
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def test_number_symbol():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- and:
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- number: 1
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- number: 0xFFFFFFFF
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- number: 2 = symbol name
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- number: 3 = symbol name
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- number: 4 = symbol name = another name
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- number: 0x100 = symbol name
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- number: 0x11 = (FLAG_A | FLAG_B)
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''')
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r = capa.rules.Rule.from_yaml(rule)
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children = list(r.statement.get_children())
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assert (Number(1) in children) == True
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assert (Number(0xFFFFFFFF) in children) == True
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assert (Number(2, 'symbol name') in children) == True
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assert (Number(3, 'symbol name') in children) == True
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assert (Number(4, 'symbol name = another name') in children) == True
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assert (Number(0x100, 'symbol name') in children) == True
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def test_count_number_symbol():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- or:
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- count(number(2 = symbol name)): 1
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- count(number(0x100 = symbol name)): 2 or more
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- count(number(0x11 = (FLAG_A | FLAG_B))): 2 or more
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''')
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r = capa.rules.Rule.from_yaml(rule)
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assert r.evaluate({Number(2): {}}) == False
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assert r.evaluate({Number(2): {1}}) == True
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assert r.evaluate({Number(2): {1, 2}}) == False
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assert r.evaluate({Number(0x100, 'symbol name'): {1}}) == False
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assert r.evaluate({Number(0x100, 'symbol name'): {1, 2, 3}}) == True
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def test_invalid_number():
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- number: "this is a string"
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- number: 2=
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- number: symbol name = 2
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'''))
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def test_offset_symbol():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- and:
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- offset: 1
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- offset: 2 = symbol name
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- offset: 3 = symbol name
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- offset: 4 = symbol name = another name
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- offset: 0x100 = symbol name
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''')
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r = capa.rules.Rule.from_yaml(rule)
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children = list(r.statement.get_children())
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assert (Offset(1) in children) == True
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assert (Offset(2, 'symbol name') in children) == True
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assert (Offset(3, 'symbol name') in children) == True
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assert (Offset(4, 'symbol name = another name') in children) == True
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assert (Offset(0x100, 'symbol name') in children) == True
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def test_count_offset_symbol():
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rule = textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- or:
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- count(offset(2 = symbol name)): 1
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- count(offset(0x100 = symbol name)): 2 or more
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- count(offset(0x11 = (FLAG_A | FLAG_B))): 2 or more
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''')
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r = capa.rules.Rule.from_yaml(rule)
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assert r.evaluate({Offset(2): {}}) == False
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assert r.evaluate({Offset(2): {1}}) == True
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assert r.evaluate({Offset(2): {1, 2}}) == False
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assert r.evaluate({Offset(0x100, 'symbol name'): {1}}) == False
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assert r.evaluate({Offset(0x100, 'symbol name'): {1, 2, 3}}) == True
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def test_invalid_offset():
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- offset: "this is a string"
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- offset: 2=
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'''))
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with pytest.raises(capa.rules.InvalidRule):
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r = capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: test rule
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features:
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- offset: symbol name = 2
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'''))
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def test_filter_rules():
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rules = capa.rules.RuleSet([
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 1
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author: joe
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features:
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- api: CreateFile
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 2
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features:
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- string: joe
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''')),
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])
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rules = rules.filter_rules_by_meta('joe')
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assert len(rules) == 1
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assert ('rule 1' in rules.rules)
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def test_filter_rules_dependencies():
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rules = capa.rules.RuleSet([
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 1
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features:
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- match: rule 2
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 2
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features:
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- match: rule 3
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 3
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features:
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- api: CreateFile
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''')),
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])
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rules = rules.filter_rules_by_meta('rule 1')
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assert(len(rules.rules) == 3)
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assert('rule 1' in rules.rules)
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assert('rule 2' in rules.rules)
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assert('rule 3' in rules.rules)
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def test_filter_rules_missing_dependency():
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with pytest.raises(capa.rules.InvalidRule):
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capa.rules.RuleSet([
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 1
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author: joe
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features:
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- match: rule 2
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''')),
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])
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def test_rules_namespace_dependencies():
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rules = [
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 1
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namespace: ns1/nsA
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features:
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- api: CreateFile
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 2
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namespace: ns1/nsB
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features:
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- api: CreateFile
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 3
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features:
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- match: ns1/nsA
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''')),
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capa.rules.Rule.from_yaml(textwrap.dedent('''
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rule:
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meta:
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name: rule 4
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features:
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- match: ns1
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''')),
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]
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r3 = set(map(lambda r: r.name, capa.rules.get_rules_and_dependencies(rules, 'rule 3')))
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assert 'rule 1' in r3
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assert 'rule 2' not in r3
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assert 'rule 4' not in r3
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r4 = set(map(lambda r: r.name, capa.rules.get_rules_and_dependencies(rules, 'rule 4')))
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assert 'rule 1' in r4
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assert 'rule 2' in r4
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assert 'rule 3' not in r4
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