Описание
Ash has authorization bypass when bypass policy condition evaluates to true
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
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:
- one_condition_matches =
cond_expr(bypass condition) = true (bug - should check if bypass actually authorizes) - 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)
- For non-matching policies:
- 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:
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):
PoC
Non-admin user can perform create actions (should be denied).
Test demonstrating the bug:
Пакеты
ash
>= 3.6.3, <= 3.7.0
3.7.1
Связанные уязвимости
Incorrect Authorization vulnerability in ash-project ash allows Authentication Bypass. This vulnerability is associated with program files lib/ash/policy/policy.ex and program routines 'Elixir.Ash.Policy.Policy':expression/2. This issue affects ash: from pkg:hex/ash@3.6.3 before pkg:hex/ash@3.7.1, from 3.6.3 before 3.7.1, from 79749c2685ea031ebb2de8cf60cc5edced6a8dd0 before 8b83efa225f657bfc3656ad8ee8485f9b2de923d.