GHSA-pcxq-fjp3-r752

Summary

Bypass policies incorrectly authorize requests when their condition evaluates to true but their authorization checks fail and no other policies apply.

Impact

Resources with bypass policies can be accessed without proper authorization when:

• Bypass condition evaluates to true
• Bypass authorization checks fail
• Other policies exist but their conditions don't match

Details

Vulnerable code in: lib/ash/policy/policy.ex:69

{%{bypass?: true}, cond_expr, complete_expr}, {one_condition_matches, all_policies_match} ->
  {
    b(cond_expr or one_condition_matches),  # <- Bug: uses condition only
    b(complete_expr or all_policies_match)
  }

The final authorization decision is: one_condition_matches AND all_policies_match

When a bypass condition is true but bypass policies fail, and subsequent policies have non-matching conditions:

1. one_condition_matches = cond_expr (bypass condition) = true (bug - should check if bypass actually authorizes)
2. all_policies_match = (complete_expr OR NOT cond_expr) for each policy
   • For non-matching policies: (false OR NOT false) = true (policies don't apply)
3. Final: true AND true = true (incorrectly authorized)

The bypass condition alone satisfies "at least one policy applies" even though the bypass fails to authorize.

Fix

Replace cond_expr with complete_expr on line 69:

{%{bypass?: true}, _cond_expr, complete_expr}, {one_condition_matches, all_policies_match} ->
  {
    b(complete_expr or one_condition_matches),  # <- Fixed
    b(complete_expr or all_policies_match)
  }

Line 52 should also be updated for consistency (though it's only triggered when bypass is the last policy, making it coincidentally safe in practice):

{%{bypass?: true}, _cond_expr, complete_expr}, {one_condition_matches, true} ->
  {
    b(complete_expr or...