Bridge Security audit

[svyatonik]

Pending audit:

• Bridge Parachains Finality Pallet;
• Bridge Messages Palet;
• Bridge GRANDPA Pallet;
• Bridge Relayers Pallet;
• Signed Extension to Refund relayers.

Future audit:

• Bridge Hub runtimes. Now they live in a separate branch: https://github.com/paritytech/cumulus/tree/bridge-hub-rococo-wococo/parachains/runtimes/bridge-hubs/bridge-hub-rococo. Will probably be merged before audit;
• [ ] pallet-bridge-transfer pallet. Now it also lives in a separate branch here: https://github.com/paritytech/cumulus/tree/bko-transfer-asset-via-bridge/parachains/pallets/bridge-transfer. Will probably be merged before audit;
• Glue code to link runtime and bridge pallets together. It'll be in the same branch as (1). Now it is here: https://github.com/paritytech/cumulus/tree/bridge-hub-rococo-wococo/bridges/bin/runtime-common;
• Refund messages confirmation tx #1904
• Added receive_single_message_proof_with_dispatch benchmark #1990
• (very maybe - PRs are trivial imo) weight v2 optimization PRs (MaxValues limit for storage maps in the pallet-bridge-grandpa #1861, "refund" proof size in GRANDPa pallet #1863, MaxValues for maps in parachain maps #1868, Max values for outbound lanes map #1871, Refund extra proof bytes in message delivery transaction #1864).

[EmmanuellNorbertTulbure]

@EmmanuellNorbertTulbure to update with everything in Sec Audit

[svyatonik]

Unaudited stuff in the polkadot-staging branch:

• Dynamic fees for bridges-v1 #2294
• Backport: GRANDPA: optimize votes_ancestries when needed  #2264