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https://github.com/valitydev/SigmaHQ.git
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Split config - code removal from exceptions
This commit is contained in:
Thomas Patzke
parent
405bc4a0d1
commit
50a6a92d20
@ -19,415 +19,8 @@ import re
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import logging
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from sigma.parser.condition import ConditionAND, ConditionOR
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# Field Mapping Definitions
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def FieldMapping(source, target=None):
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"""Determines target type and instantiate appropriate mapping type"""
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if target == None:
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return SimpleFieldMapping(source, source)
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elif type(target) == str:
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return SimpleFieldMapping(source, target)
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elif type(target) == list:
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return MultiFieldMapping(source, target)
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elif type(target) == dict:
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return ConditionalFieldMapping(source, target)
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class SimpleFieldMapping:
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"""1:1 field mapping"""
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target_type = str
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def __init__(self, source, target):
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"""Initialization with generic target type check"""
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if type(target) != self.target_type:
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raise TypeError("Target type mismatch: wrong mapping type for this target")
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self.source = source
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self.target = target
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def resolve(self, key, value, sigmaparser):
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"""Return mapped field name"""
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return (self.target, value)
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def resolve_fieldname(self, fieldname):
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return self.target
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class MultiFieldMapping(SimpleFieldMapping):
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"""1:n field mapping that expands target field names into OR conditions"""
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target_type = list
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def resolve(self, key, value, sigmaparser):
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"""Returns multiple target field names as OR condition"""
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cond = ConditionOR()
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for fieldname in self.target:
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cond.add((fieldname, value))
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return cond
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def resolve_fieldname(self, fieldname):
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return self.target
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class ConditionalFieldMapping(SimpleFieldMapping):
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"""
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Conditional field mapping:
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* key contains field=value condition, value target mapping
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* key "default" maps when no condition matches
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* if no condition matches and there is no default, don't perform mapping
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"""
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target_type = dict
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def __init__(self, source, target):
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"""Init table between condition field names and values"""
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super().__init__(source, target)
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self.conditions = dict() # condition field -> condition value -> target fields
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self.default = None
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for condition, target in self.target.items():
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try: # key contains condition (field=value)
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field, value = condition.split("=")
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self.add_condition(field, value, target)
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except ValueError as e: # no, condition - "default" expected
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if condition == "default":
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if self.default == None:
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if type(target) == str:
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self.default = [ target ]
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elif type(target) == list:
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self.default = target
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else:
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raise SigmaConfigParseError("Default mapping must be single value or list")
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else:
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raise SigmaConfigParseError("Conditional field mapping can have only one default value, use list for multiple target mappings")
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else:
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raise SigmaConfigParseError("Expected condition or default") from e
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def add_condition(self, field, value, target):
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if field not in self.conditions:
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self.conditions[field] = dict()
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if value not in self.conditions[field]:
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self.conditions[field][value] = list()
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if type(target) == str:
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self.conditions[field][value].append(target)
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elif type(target) == list:
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self.conditions[field][value].extend(target)
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def resolve(self, key, value, sigmaparser):
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# build list of matching target mappings
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targets = set()
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for condfield in self.conditions:
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if condfield in sigmaparser.values:
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rulefieldvalues = sigmaparser.values[condfield]
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for condvalue in self.conditions[condfield]:
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if condvalue in rulefieldvalues:
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targets.update(self.conditions[condfield][condvalue])
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if len(targets) == 0: # no matching condition, try with default mapping
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if self.default != None:
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targets = self.default
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if len(targets) == 1: # result set contains only one target, return mapped item (like SimpleFieldMapping)
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return (targets.pop(), value)
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elif len(targets) > 1: # result set contains multiple targets, return all linked as OR condition (like MultiFieldMapping)
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cond = ConditionOR()
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for target in targets:
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cond.add((target, value))
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return cond
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else: # no mapping found
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return (key, value)
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def resolve_fieldname(self, fieldname):
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if self.default != None:
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return self.default
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else:
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return fieldname
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# Configuration
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class SigmaConfiguration:
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"""Sigma converter configuration. Contains field mappings and logsource descriptions"""
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def __init__(self, configyaml=None):
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if configyaml == None:
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self.config = None
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self.fieldmappings = dict()
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self.logsources = dict()
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self.logsourcemerging = SigmaLogsourceConfiguration.MM_AND
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self.defaultindex = None
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self.backend = None
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else:
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config = yaml.safe_load(configyaml)
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self.config = config
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self.fieldmappings = dict()
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try:
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for source, target in config['fieldmappings'].items():
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self.fieldmappings[source] = FieldMapping(source, target)
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except KeyError:
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pass
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if type(self.fieldmappings) != dict:
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raise SigmaConfigParseError("Fieldmappings must be a map")
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try:
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self.logsourcemerging = config['logsourcemerging']
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except KeyError:
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self.logsourcemerging = SigmaLogsourceConfiguration.MM_AND
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try:
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self.defaultindex = config['defaultindex']
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except KeyError:
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self.defaultindex = None
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self.logsources = list()
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self.backend = None
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def get_fieldmapping(self, fieldname):
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"""Return mapped fieldname if mapping defined or field name given in parameter value"""
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try:
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return self.fieldmappings[fieldname]
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except KeyError:
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return FieldMapping(fieldname)
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def get_logsource(self, category, product, service):
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"""Return merged log source definition of all logosurces that match criteria"""
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matching = [logsource for logsource in self.logsources if logsource.matches(category, product, service)]
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return SigmaLogsourceConfiguration(matching, self.defaultindex)
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def set_backend(self, backend):
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"""Set backend. This is used by other code to determine target properties for index addressing"""
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self.backend = backend
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if self.config != None:
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if 'logsources' in self.config:
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logsources = self.config['logsources']
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if type(logsources) != dict:
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raise SigmaConfigParseError("Logsources must be a map")
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for name, logsource in logsources.items():
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self.logsources.append(SigmaLogsourceConfiguration(logsource, self.defaultindex, name, self.logsourcemerging, self.get_indexfield()))
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def get_indexfield(self):
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"""Get index condition if index field name is configured"""
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if self.backend != None:
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return self.backend.index_field
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class SigmaLogsourceConfiguration:
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"""Contains the definition of a log source"""
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MM_AND = "and" # Merge all conditions with AND
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MM_OR = "or" # Merge all conditions with OR
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def __init__(self, logsource=None, defaultindex=None, name=None, mergemethod=MM_AND, indexfield=None):
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self.name = name
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self.indexfield = indexfield
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if logsource == None: # create empty object
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self.category = None
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self.product = None
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self.service = None
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self.index = list()
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self.conditions = None
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elif type(logsource) == list and all([isinstance(o, SigmaLogsourceConfiguration) for o in logsource]): # list of SigmaLogsourceConfigurations: merge according to mergemethod
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# Merge category, product and service
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categories = set([ ls.category for ls in logsource if ls.category != None ])
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products = set([ ls.product for ls in logsource if ls.product != None ])
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services = set([ ls.service for ls in logsource if ls.service != None])
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if len(categories) > 1 or len(products) > 1 or len(services) > 1:
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raise ValueError("Merged SigmaLogsourceConfigurations must have disjunct categories (%s), products (%s) and services (%s)" % (str(categories), str(products), str(services)))
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try:
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self.category = categories.pop()
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except KeyError:
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self.category = None
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try:
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self.product = products.pop()
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except KeyError:
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self.product = None
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try:
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self.service = services.pop()
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except KeyError:
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self.service = None
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# Merge all index patterns
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self.index = list(set([index for ls in logsource for index in ls.index])) # unique(flat(logsources.index))
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if len(self.index) == 0 and defaultindex is not None: # if no index pattern matched and default index is present: use default index
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if type(defaultindex) == str:
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self.index = [defaultindex]
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elif type(defaultindex) == list and all([type(i) == str for i in defaultindex]):
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self.index = defaultindex
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else:
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raise TypeError("Default index must be string or list of strings")
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# "merge" index field (should never differ between instances because it is provided by backend class
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indexfields = [ ls.indexfield for ls in logsource if ls.indexfield != None ]
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try:
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self.indexfield = indexfields[0]
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except IndexError:
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self.indexfield = None
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# Merge conditions according to mergemethod
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if mergemethod == self.MM_AND:
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cond = ConditionAND()
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elif mergemethod == self.MM_OR:
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cond = ConditionOR()
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else:
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raise ValueError("Mergemethod must be '%s' or '%s'" % (self.MM_AND, self.MM_OR))
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for ls in logsource:
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if ls.conditions != None:
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cond.add(ls.conditions)
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if len(cond) > 0:
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self.conditions = cond
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else:
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self.conditions = None
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elif type(logsource) == dict: # create logsource configuration from parsed yaml
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if 'category' in logsource and type(logsource['category']) != str \
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or 'product' in logsource and type(logsource['product']) != str \
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or 'service' in logsource and type(logsource['service']) != str:
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raise SigmaConfigParseError("Logsource category, product or service must be a string")
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try:
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self.category = logsource['category']
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except KeyError:
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self.category = None
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try:
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self.product = logsource['product']
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except KeyError:
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self.product = None
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try:
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self.service = logsource['service']
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except KeyError:
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self.service = None
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if self.category == None and self.product == None and self.service == None:
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raise SigmaConfigParseError("Log source definition will not match")
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if 'index' in logsource:
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index = logsource['index']
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if type(index) not in (str, list):
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raise SigmaConfigParseError("Logsource index must be string or list of strings")
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if type(index) == list and not all([type(index) == str for index in logsource['index']]):
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raise SigmaConfigParseError("Logsource index patterns must be strings")
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if type(index) == list:
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self.index = index
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else:
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self.index = [ index ]
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else:
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# no default index handling here - this branch is executed if log source definitions are parsed from
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# config and these must not necessarily contain an index definition. A valid index may later be result
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# from a merge, where default index handling applies.
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self.index = []
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if 'conditions' in logsource:
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if type(logsource['conditions']) != dict:
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raise SigmaConfigParseError("Logsource conditions must be a map")
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cond = ConditionAND()
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for key, value in logsource['conditions'].items():
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cond.add((key, value))
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self.conditions = cond
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else:
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self.conditions = None
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else:
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raise SigmaConfigParseError("Logsource definitions must be maps")
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def matches(self, category, product, service):
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"""Match log source definition against given criteria, None = ignore"""
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searched = 0
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for searchval, selfval in zip((category, product, service), (self.category, self.product, self.service)):
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if searchval == None and selfval != None:
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return False
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if selfval != None:
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searched += 1
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if searchval != selfval:
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return False
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if searched:
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return True
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def get_indexcond(self):
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"""Get index condition if index field name is configured"""
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cond = ConditionOR()
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if self.indexfield:
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for index in self.index:
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cond.add((self.indexfield, index))
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return cond
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else:
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return None
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def __str__(self):
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return "[ LogSourceConfiguration: %s %s %s indices: %s ]" % (self.category, self.product, self.service, str(self.index))
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class SigmaConfigParseError(Exception):
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pass
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# Rule Filtering
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class SigmaRuleFilter:
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"""Filter for Sigma rules with conditions"""
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LEVELS = {
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"low" : 0,
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"medium" : 1,
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"high" : 2,
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"critical" : 3
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}
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STATES = ["experimental", "testing", "stable"]
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def __init__(self, expr):
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self.minlevel = None
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self.maxlevel = None
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self.status = None
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self.logsources = list()
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for cond in [c.replace(" ", "") for c in expr.split(",")]:
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if cond.startswith("level<="):
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try:
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level = cond[cond.index("=") + 1:]
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self.maxlevel = self.LEVELS[level]
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except KeyError as e:
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raise SigmaRuleFilterParseException("Unknown level '%s' in condition '%s'" % (level, cond)) from e
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elif cond.startswith("level>="):
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try:
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level = cond[cond.index("=") + 1:]
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self.minlevel = self.LEVELS[level]
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except KeyError as e:
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raise SigmaRuleFilterParseException("Unknown level '%s' in condition '%s'" % (level, cond)) from e
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elif cond.startswith("level="):
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try:
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level = cond[cond.index("=") + 1:]
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self.minlevel = self.LEVELS[level]
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self.maxlevel = self.minlevel
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except KeyError as e:
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raise SigmaRuleFilterParseException("Unknown level '%s' in condition '%s'" % (level, cond)) from e
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elif cond.startswith("status="):
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self.status = cond[cond.index("=") + 1:]
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if self.status not in self.STATES:
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raise SigmaRuleFilterParseException("Unknown status '%s' in condition '%s'" % (self.status, cond))
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elif cond.startswith("logsource="):
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self.logsources.append(cond[cond.index("=") + 1:])
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else:
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raise SigmaRuleFilterParseException("Unknown condition '%s'" % cond)
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def match(self, yamldoc):
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"""Match filter conditions against rule"""
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# Levels
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if self.minlevel is not None or self.maxlevel is not None:
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try:
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level = self.LEVELS[yamldoc['level']]
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except KeyError: # missing or invalid level
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return False # User wants level restriction, but it's not possible here
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# Minimum level
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if self.minlevel is not None:
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if level < self.minlevel:
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return False
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# Maximum level
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if self.maxlevel is not None:
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if level > self.maxlevel:
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return False
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# Status
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if self.status is not None:
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try:
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status = yamldoc['status']
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except KeyError: # missing status
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return False # User wants status restriction, but it's not possible here
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if status != self.status:
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return False
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# Log Sources
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if len(self.logsources) > 0:
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try:
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logsources = { value for key, value in yamldoc['logsource'].items() }
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except (KeyError, AttributeError): # no log source set
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return False # User wants status restriction, but it's not possible here
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for logsrc in self.logsources:
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if logsrc not in logsources:
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return False
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# all tests passed
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return True
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class SigmaRuleFilterParseException(Exception):
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pass
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