73 lines
2.2 KiB
Python
73 lines
2.2 KiB
Python
import stix2.pattern_visitor
|
|
from stix2.equivalence.patterns.transform import (
|
|
ChainTransformer, SettleTransformer
|
|
)
|
|
from stix2.equivalence.patterns.compare.observation import (
|
|
observation_expression_cmp
|
|
)
|
|
from stix2.equivalence.patterns.transform.observation import (
|
|
CanonicalizeComparisonExpressionsTransformer,
|
|
AbsorptionTransformer,
|
|
FlattenTransformer,
|
|
DNFTransformer,
|
|
OrderDedupeTransformer
|
|
)
|
|
|
|
|
|
# Lazy-initialize
|
|
_pattern_canonicalizer = None
|
|
|
|
|
|
def _get_pattern_canonicalizer():
|
|
"""
|
|
Get a canonicalization transformer for STIX patterns.
|
|
|
|
:return: The transformer
|
|
"""
|
|
|
|
# The transformers are either stateless or contain no state which changes
|
|
# with each use. So we can setup the transformers once and keep reusing
|
|
# them.
|
|
global _pattern_canonicalizer
|
|
|
|
if not _pattern_canonicalizer:
|
|
canonicalize_comp_expr = \
|
|
CanonicalizeComparisonExpressionsTransformer()
|
|
|
|
obs_expr_flatten = FlattenTransformer()
|
|
obs_expr_order = OrderDedupeTransformer()
|
|
obs_expr_absorb = AbsorptionTransformer()
|
|
obs_simplify = ChainTransformer(
|
|
obs_expr_flatten, obs_expr_order, obs_expr_absorb
|
|
)
|
|
obs_settle_simplify = SettleTransformer(obs_simplify)
|
|
|
|
obs_dnf = DNFTransformer()
|
|
|
|
_pattern_canonicalizer = ChainTransformer(
|
|
canonicalize_comp_expr,
|
|
obs_settle_simplify, obs_dnf, obs_settle_simplify
|
|
)
|
|
|
|
return _pattern_canonicalizer
|
|
|
|
|
|
def equivalent_patterns(pattern1, pattern2):
|
|
"""
|
|
Determine whether two STIX patterns are semantically equivalent.
|
|
|
|
:param pattern1: The first STIX pattern
|
|
:param pattern2: The second STIX pattern
|
|
:return: True if the patterns are semantically equivalent; False if not
|
|
"""
|
|
patt_ast1 = stix2.pattern_visitor.create_pattern_object(pattern1)
|
|
patt_ast2 = stix2.pattern_visitor.create_pattern_object(pattern2)
|
|
|
|
pattern_canonicalizer = _get_pattern_canonicalizer()
|
|
canon_patt1, _ = pattern_canonicalizer.transform(patt_ast1)
|
|
canon_patt2, _ = pattern_canonicalizer.transform(patt_ast2)
|
|
|
|
result = observation_expression_cmp(canon_patt1, canon_patt2)
|
|
|
|
return result == 0
|