Audit fixes

synd-contracts/src/staking/GasAggregator.sol

@@ -146,6 +146,11 @@ contract GasAggregator is Ownable(msg.sender), Pausable, EpochTracker {
     /// @param maxAppchainsToQuery The new maximum number of appchains to query
     event UpdateMaxAppchainsToQuery(uint256 indexed epoch, uint256 maxAppchainsToQuery);
 
+    /// @notice Emitted when the factory address and bytecode is set
+    /// @param factoryAddress The address of the factory contract
+    /// @param bytecodeHash The bytecode hash of the proxy that the factory deploys
+    event FactorySet(address indexed factoryAddress, bytes32 bytecodeHash);
+
     /*//////////////////////////////////////////////////////////////
                             CONSTRUCTOR
     //////////////////////////////////////////////////////////////*/
@@ -384,6 +389,7 @@ contract GasAggregator is Ownable(msg.sender), Pausable, EpochTracker {
         require(bytecodeHash != 0, InvalidDataHash());
         factory = newFactory;
         syndicateProxyBytecodeHash = bytecodeHash;
+        emit FactorySet(newFactory, bytecodeHash);
     }
 
     /**

synd-contracts/src/staking/GasArchive.sol

@@ -291,18 +291,18 @@ contract GasArchive is Initializable, OwnableUpgradeable, IGasDataProvider, UUPS
     /// @dev Verifies the proof data of the sequencing chain's proof against the confirmed seq chain block hash
     /// @param seqChainID The sequencing chain ID
     /// @param sendRoot The send root stored in the the Arbitrum Outbox contract that the eth proof was generated for, unused if seqChainID == settlementChainID
-    /// @param ethBlockHeader RLP-encoded Ethereum block header, unused if seqChainID == settlementChainID
-    /// @param ethAccountProof Merkle proof of the bridge contract account, unused if seqChainID == settlementChainID
-    /// @param ethStorageProof Merkle proof of the storage slot containing the block hash, unused if seqChainID == settlementChainID
+    /// @param seqParentBlockHeader RLP-encoded block header of the parent chain of the sequencing chain, unused if seqChainID == settlementChainID
+    /// @param seqParentAccountProof Merkle proof of the bridge contract account, unused if seqChainID == settlementChainID
+    /// @param seqParentStorageProof Merkle proof of the storage slot containing the block hash, unused if seqChainID == settlementChainID
     /// @param seqBlockHeader RLP-encoded sequencing chain block header
     /// @param seqAccountProof Merkle proof of the GasAggregator account
     /// @param seqStorageProof Merkle proof of the epoch data storage slot
     function confirmEpochDataHash(
         uint256 seqChainID,
         bytes32 sendRoot,
-        bytes calldata ethBlockHeader,
-        bytes[] calldata ethAccountProof,
-        bytes[] calldata ethStorageProof,
+        bytes calldata seqParentBlockHeader,
+        bytes[] calldata seqParentAccountProof,
+        bytes[] calldata seqParentStorageProof,
         bytes calldata seqBlockHeader,
         bytes[] calldata seqAccountProof,
         bytes[] calldata seqStorageProof
@@ -315,15 +315,15 @@ contract GasArchive is Initializable, OwnableUpgradeable, IGasDataProvider, UUPS
         }
 
         if ($.seqChainSettlesToBase[seqChainID]) {
-            require($.setBlockHashes[keccak256(ethBlockHeader)], InvalidSetBlockHeader());
+            require($.setBlockHashes[keccak256(seqParentBlockHeader)], InvalidSetBlockHeader());
         } else {
-            require($.ethBlockHashes[keccak256(ethBlockHeader)], InvalidEthBlockHeader());
+            require($.ethBlockHashes[keccak256(seqParentBlockHeader)], InvalidEthBlockHeader());
         }
 
         bytes32 verifiedSeqChainBlockHash = _getSlotValueFromProof({
-            blockHeader: ethBlockHeader,
-            accountProof: ethAccountProof,
-            storageProof: ethStorageProof,
+            blockHeader: seqParentBlockHeader,
+            accountProof: seqParentAccountProof,
+            storageProof: seqParentStorageProof,
             account: $.seqChainOutbox[seqChainID],
             storageSlot: keccak256(abi.encode(sendRoot, SEND_ROOT_STORAGE_SLOT))
         });
@@ -427,7 +427,7 @@ contract GasArchive is Initializable, OwnableUpgradeable, IGasDataProvider, UUPS
                 stack: _RLPItemsFromProofBytes(accountProof)
             }).toRlpItem();
 
-        // If the account does not exist, return the hash of an empty trie.
+        // If the account does not exist in the proof, revert with AccountDoesNotExistInProof error.
         require(accountRlp.len > 0, AccountDoesNotExistInProof());
 
         RLPReader.RLPItem memory slotContents = MerklePatriciaProofVerifier.extractProofValue({

synd-contracts/src/staking/STAKING_EMISSIONS_AUDIT_GUIDE.md

@@ -190,10 +190,10 @@ bytes32 public syndicateProxyBytecodeHash;
 
 #### Key Functions:
 
-##### `addChain(uint256 chainId, uint256 addChainFee)`
+##### `addChain(uint256 chainId) external payable`
 - Registers an appchain for gas tracking
-- Requires fee payment in SYND tokens
-- Only called by authorized appchain contracts
+- Permissionless: anyone can call by paying the required fee (owner pays no fee)
+- Chain must exist at deterministic CREATE2 address (verified via factory + bytecode hash)
 
 ##### `aggregateTokensUsed(uint256 epochIndex, uint256[] calldata chainIds, uint256[] calldata tokensUsed)`
 - Aggregates gas usage for completed epochs
@@ -634,8 +634,8 @@ deposit(epochIndex) with 1001 ETH:
 - **Anyone**: Can submit proofs and epoch data (permissionless validation)
 
 #### GasAggregator:
-- **Owner**: Can pause, set factory, manage parameters
-- **Appchains**: Can add themselves (with fee payment)
+- **Owner**: Can pause, set factory, manage parameters, add/remove chains without fee
+- **Anyone**: Can register chains by paying the `addChainFee` (chain must exist at deterministic address)
 - **Anyone**: Can aggregate completed epoch data
 
 #### Reward Pools: