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Project-declaredLean 4.31.0 · null

Partial evaluate policy is sound

Cedar.Thm.partial_evaluate_policy_is_sound

Plain-language statement

Policy evaluation soundness for TPE: Evaluating a result residual is equivalent to evaluating the input policy, given valid and consistent requests and entities. The equivalence is w.r.t authorization results. That is, the evaluation results are strictly equal when they are .ok or both errors (captured by Except.toOption). We do not care if the error...

Exact Lean statement

theorem partial_evaluate_policy_is_sound
  {schema : Schema}
  {residual : Residual}
  {policy : Policy}
  {req : Request}
  {es : Entities}
  {preq : PartialRequest}
  {pes : PartialEntities}
  {env : TypeEnv} :
  evaluatePolicy schema policy preq pes = .ok residual →
  schema.environment? preq.principal.ty preq.resource.ty preq.action = .some env →
  InstanceOfWellFormedEnvironment req es env →
  RequestAndEntitiesRefine req es preq pes →
  (Spec.evaluate policy.toExpr req es).toOption = (Residual.evaluate residual req es).toOption

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
theorem partial_evaluate_policy_is_sound  {schema : Schema}  {residual : Residual}  {policy : Policy}  {req : Request}  {es : Entities}  {preq : PartialRequest}  {pes : PartialEntities}  {env : TypeEnv} :  evaluatePolicy schema policy preq pes = .ok residual   schema.environment? preq.principal.ty preq.resource.ty preq.action = .some env   InstanceOfWellFormedEnvironment req es env   RequestAndEntitiesRefine req es preq pes   (Spec.evaluate policy.toExpr req es).toOption = (Residual.evaluate residual req es).toOption:= by  intro h₁ h_schema_env h₄ h₃  simp [evaluatePolicy, h_schema_env] at h₁  split at h₁ <;> try cases h₁  cases hcheck : Except.mapError Error.invalidPolicy (checkEntities schema policy.toExpr) <;>    simp only [hcheck, Except.bind_err, reduceCtorEq] at h₁  simp [do_ok_eq_ok] at h₁  rcases h₁ with _, _, h₁₁, h₁₂  simp [Except.mapError] at h₁₁  split at h₁₁ <;> try cases h₁₁  rename_i ty _ _ heq₂  have h₅ := typechecked_is_well_typed_after_lifting heq₂  have h₉ : Residual.WellTyped env (TypedExpr.toResidual ty.liftBoolTypes) :=    conversion_preserves_typedness h₅  have h₆ := partial_evaluate_is_sound h₉ h₄ h₃  subst h₁₂  have h₇ := type_of_preserves_evaluation_results (empty_capabilities_invariant req es) h₄ heq₂  have h₈ : Spec.evaluate (substituteAction env.reqty.action policy.toExpr) req es = Spec.evaluate policy.toExpr req es := by    simp [InstanceOfWellFormedEnvironment] at h₄    rcases h₄ with _, h₄, _    simp [InstanceOfRequestType] at h₄    rcases h₄ with _, h₄, _    rw [h₄]    exact substitute_action_preserves_evaluation policy.toExpr req es  simp [h₈] at h₇  rw [h₇, type_lifting_preserves_expr,  h₆]  congr  apply conversion_preserves_evaluation
Project
Cedar Specification
License
Apache-2.0
Commit
3f093947b8ae
Source
cedar-lean/Cedar/Thm/TPE/Policy.lean:46-87

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