AggLayer: Add token remapping and migration support #2704
Description
Description
The Solidity sovereign chain bridge (BridgeL2SovereignChain.sol) supports updating token-to-wrapped-token mappings. The bridge manager can remap a (originNetwork, originToken) pair to a new sovereign token via setMultipleSovereignTokenAddress(), allowing token contract upgrades and migration of user balances from legacy to updated tokens via migrateLegacyToken(). Legacy mappings can be cleaned up with removeLegacySovereignTokenAddress(). Token remapping is something sovereign chains can opt into, not a hard requirement from the base bridge protocol.
The Miden bridge's register_faucet procedure writes to faucet_registry_map and token_registry_map but provides no explicit update or overwrite mechanism. If a faucet is registered with incorrect parameters (wrong scale, wrong metadata hash), or if the faucet contract needs to be upgraded, there is no way to update the mapping without deploying an entirely new bridge. The current register_faucet does silently overwrite existing entries (since set_map_item overwrites), but this behavior is not intentional and has no validation or event tracking.
Impact
Token contract upgrades or parameter corrections are impossible post-registration through an intentional mechanism. Users holding bridged tokens on a deprecated faucet have no migration path.
Recommended Action
Add an update_faucet_mapping procedure gated by the bridge admin that remaps a token from an old faucet to a new one, updating both the faucet and token registries. Also modify register_faucet to reject duplicate registrations, making the distinction between initial registration and updates explicit. Consider adding a user-facing token migration mechanism (burn old, mint new) as a follow-up.
References
bridge_config.masm(register_faucet)config_note.rsBridgeL2SovereignChain.sol
Classification
This feature is part of the sovereign chain extension (BridgeL2SovereignChain), not the base bridge contract. Token remapping is something sovereign chains can opt into, not a hard requirement from the base bridge protocol.