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Rule Config

Rule Config

Allows to overwrite the default behaviour of the rule, such as changing the rule mode and risk value.

class RuleConfig(BaseModel):
    rule_mode: Optional[RuleMode] = None
    risk_value: Optional[RuleRisk] = None


Accepts a more granular configuration of the rule. When adding a failure or warning it will check if there is a filter that matches the current context and set the new risk or mode. Context depends on each rule and is available inside each rule's documentation. The object accepts a reason parameter to say why that filter exists.

class Filter(BaseModel):
    debug: bool = False
    reason: str = ""
    eval: Union[Dict, Callable]
    rule_mode: Optional[RuleMode] = None
    risk_value: Optional[RuleRisk] = None
    rules: Set[str] = None

    @validator("eval", pre=True)
    def set_eval(cls, eval, values):
        return build_evaluator(eval, values["debug"])

    def __call__(self, **kwargs):
        if self.debug:
            logger.debug(f"Filter: {self.reason}")
        result = self.eval(kwargs)
        if self.debug:
            logger.debug(f"Filter result: {result}")
        return result

Filter preference

Following the cascade style, takes preference always the last value set following this structure:

Rule Standard -> Filter #1 -> ... -> Filter #N

When loading filters from a folder the order is alphabetical.

Implemented filter functions

Function Description Example
eq Same as a == b {"eq": ["string", "string"]}
ne Same as a != b {"ne": ["string", "not_that_string"]}
lt Same as a < b {"lt": [0, 1]}
gt Same as a > b {"gt": [1, 0]}
le Same as a <= b {"le": [1, 1]}
ge Same as a >= b {"ge": [1, 1]}
not Same as not a {"not": True}
or True if any arg is True {"or": [False, True]}
and True if all args are True {"and": [True, True]}
in Same as a in b {"in": ["b", ["a", "b"]]}
regex True if b match pattern a (case sensitive) {"regex": [r"^\d+$", "5"]}
regex:ignorecase True if b match pattern a (case insensitive) {"regex:ignorecase": [r"^AA$", "aa"]}
exists True if a is not None {"exists": None}
empty True if len(a) equals 0 {"empty": []}
ref Get the value at any depth of the context based on the path described by a. {"ref": "param_a.param_b"}


Disable the rule TestRule if the role name is prefixed with sandbox- and the principal equals arn:aws:iam::123456789012:role/test-role.

        "and": [
            {"regex": ["^sandbox-.*$", {"ref": "resource.Properties.RoleName"}]},
            {"eq": [{"ref": "principal"}, "arn:aws:iam::123456789012:role/test-role"]},

A filter accepts multiple rules. Additionally the Filter class accepts an optiona debug flag parameter. If enabled, it will log every iteration of the filter evaluation, except for or and and operations.