[Moderate] Insecure randomness algorithm usage

[sebastianmontero]

[Moderate] Insecure randomness algorithm usage

Summary

The source of randomness configured in the runtime for the society pallet is set to pallet_insecure_randomness_collective_flip, which is implemented in Substrate.
The output of collective flip is highly predictable as it is based on the last 81 blocks and should not be used as a true source of randomness.

Issue details

The RandomnessCollectiveFlip definition for Hashed's parachain runtime is set to pallet_insecure_randomness_collective_flip:

// Create the runtime by composing the FRAME pallets that were previously configured.
construct_runtime!(
	pub enum Runtime
	{
			...
		RandomnessCollectiveFlip: pallet_insecure_randomness_collective_flip::{Pallet, Storage}  = 82,
		Society: pallet_society::{Pallet, Call, Storage, Event<T>}  = 83,
			...
	}
};

The runtime config for pallet-society makes use of the RandomnessCollectiveFlip pallet defined in the above construct_runtime!:

impl pallet_society::Config for Runtime {
	type RuntimeEvent = RuntimeEvent;
	type PalletId = SocietyPalletId;
	type Currency = Balances;
	type Randomness = RandomnessCollectiveFlip;

Risk

A malicious collator could influence the randomness, which is being used by the society pallet.

Mitigation

Use a secure randomness, either with the usage of an oracle of a project like drand or a secure library.
You can also consider using the BABE pallet, as described in the Substrate documentation. Check out Kusama's runtime configuration for an example.

[sebastianmontero]

This is low priority, as at the moment we are not using the society pallet, and there is not a straight forward solution.