Ash.Policy.Check behaviour (ash v3.7.6)

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A behaviour for declaring checks, which can be used to easily construct authorization rules.

If a check can be expressed simply, i.e as a function of the actor, or the context of the request, see Ash.Policy.SimpleCheck for an easy way to write that check. If a check can be expressed with a filter statement, see Ash.Policy.FilterCheck for an easy way to write that check.

Summary

Types

actor()
authorizer()
check_type()
context()
options()
ref()
t()

Callbacks

auto_filter(actor, authorizer, options)

An optional callback, that allows the check to work with policies set to access_type :filter

check(actor, list, map, options)

An optional callback, that allows the check to work with policies set to access_type :runtime

conflicts?(ref, ref, context)

Determine if two check references are mutually exclusive (conflicting).

describe(options)

Describe the check in human readable format, given the options

eager_evaluate?()
expand_description(actor, authorizer, options)

Expands the description of the check, given the actor and subject

implies?(ref, ref, context)

Determine if the first check reference implies the second check reference.

prefer_expanded_description?()

Whether or not the expanded description should replace the basic description in breakdowns

requires_original_data?(authorizer, options)

Whether or not your check requires the original data of a changeset (if applicable)

simplify(ref, context)

Simplify a check reference into a SAT expression of simpler check references.

strict_check(actor, authorizer, options)

Strict checks should be cheap, and should never result in external calls (like database or domain)

type()

The type of the check

Functions

defines_auto_filter?(module)
defines_check?(module)

Types

actor()

@type actor() :: any()

authorizer()

@type authorizer() :: Ash.Policy.Authorizer.t()

check_type()

@type check_type() :: :simple | :filter | :manual

context()

@type context() :: %{resource: Ash.Resource.t()}

options()

@type options() :: Keyword.t()

ref()

@type ref() :: {module(), Keyword.t()} | module()

t()

@type t() :: %Ash.Policy.Check{
  __spark_metadata__: Spark.Dsl.Entity.spark_meta(),
  check: ref(),
  check_module: module(),
  check_opts: options(),
  type: check_type()
}

Callbacks

auto_filter(actor, authorizer, options)

(optional) 
@callback auto_filter(actor(), authorizer(), options()) :: Keyword.t() | Ash.Expr.t()

An optional callback, that allows the check to work with policies set to access_type :filter

Return a keyword list filter that will be applied to the query being made, and will scope the results to match the rule

check(actor, list, map, options)

(optional) 
@callback check(actor(), [Ash.Resource.record()], map(), options()) :: [
  Ash.Resource.record()
]

An optional callback, that allows the check to work with policies set to access_type :runtime

Takes a list of records, and returns the subset of authorized records.

conflicts?(ref, ref, context)

(optional) 
@callback conflicts?(ref(), ref(), context()) :: boolean()

Determine if two check references are mutually exclusive (conflicting).

This is used by the SAT solver to optimize policy evaluation by understanding when two checks cannot both be true at the same time.

describe(options)

@callback describe(options()) :: String.t()

Describe the check in human readable format, given the options

eager_evaluate?()

@callback eager_evaluate?() :: boolean()

expand_description(actor, authorizer, options)

(optional) 
@callback expand_description(
  actor(),
  authorizer(),
  options()
) :: {:ok, String.t()} | :none

Expands the description of the check, given the actor and subject

implies?(ref, ref, context)

(optional) 
@callback implies?(ref(), ref(), context()) :: boolean()

Determine if the first check reference implies the second check reference.

This is used by the SAT solver to optimize policy evaluation by understanding when one check being true guarantees another check is also true.

prefer_expanded_description?()

@callback prefer_expanded_description?() :: boolean()

Whether or not the expanded description should replace the basic description in breakdowns

requires_original_data?(authorizer, options)

@callback requires_original_data?(authorizer(), options()) :: boolean()

Whether or not your check requires the original data of a changeset (if applicable)

simplify(ref, context)

(optional) 
@callback simplify(ref(), context()) :: Crux.Expression.t(ref())

Simplify a check reference into a SAT expression of simpler check references.

This is used by the SAT solver to break down complex checks into simpler components for more efficient policy evaluation. For example, a check that matches multiple action types could be simplified into an OR expression of separate checks for each action type. Or ActorAbsent could simplify into not(ActorPresent).

strict_check(actor, authorizer, options)

@callback strict_check(actor(), authorizer(), options()) ::
  {:ok, boolean() | :unknown} | {:error, term()}

Strict checks should be cheap, and should never result in external calls (like database or domain)

It should return {:ok, true} if it can tell that the request is authorized, and {:ok, false} if it can tell that it is not. If unsure, it should return {:ok, :unknown}

type()

@callback type() :: check_type()

The type of the check

:manual checks must be written by hand as standard check modules :filter checks can use Ash.Policy.FilterCheck for simplicity :simple checks can use Ash.Policy.SimpleCheck for simplicity

Functions

defines_auto_filter?(module)

defines_check?(module)