diff --git a/docs/architecture/README.md b/docs/architecture/README.md index f12322b321..eb8004837a 100644 --- a/docs/architecture/README.md +++ b/docs/architecture/README.md @@ -25,14 +25,15 @@ To suggest an ADR, please make use of the [ADR template](./adr-template.md) prov ## Table of Contents -| ADR \# | Description | Status | -|---------------------|----------------------------------------------------------------------------|----------| -| [001](./adr-001.md) | Disable Gravity Bridge at Genesis | Accepted | -| [002](./adr-002.md) | Use a custom fork of ibc-go | Accepted | -| [003](./adr-003.md) | Add Fee Market Module | Accepted | -| [004](./adr-004.md) | Tokens conversion in Cronos | Accepted | -| [005](./adr-005.md) | Cross-chain Validation for Gravity Bridge | Rejected | -| [006](./adr-006.md) | Migrating CRC20 contract to CRC21 standard | Rejected | -| [007](./adr-007.md) | Generic event format for evm-hook actions | Accepted | -| [008](./adr-008.md) | Denom and Contract Mapping Enhancement for Bi-Directional Token Conversion | Accepted | -| [009](./adr-009.md) | Permissioned addresses in Cronos | Accepted | +| ADR \# | Description | Status | +|----------------------|----------------------------------------------------------------------------|----------| +| [001](./adr-001.md) | Disable Gravity Bridge at Genesis | Accepted | +| [002](./adr-002.md) | Use a custom fork of ibc-go | Accepted | +| [003](./adr-003.md) | Add Fee Market Module | Accepted | +| [004](./adr-004.md) | Tokens conversion in Cronos | Accepted | +| [005](./adr-005.md) | Cross-chain Validation for Gravity Bridge | Rejected | +| [006](./adr-006.md) | Migrating CRC20 contract to CRC21 standard | Rejected | +| [007](./adr-007.md) | Generic event format for evm-hook actions | Accepted | +| [008](./adr-008.md) | Denom and Contract Mapping Enhancement for Bi-Directional Token Conversion | Accepted | +| [009](./adr-009.md) | Permissioned addresses in Cronos | Accepted | +| [0010](./adr-010.md) | Custom precompiled for app-chain | Accepted | diff --git a/docs/architecture/adr-008.md b/docs/architecture/adr-008.md index 73bd1a78a6..05b4b11e22 100644 --- a/docs/architecture/adr-008.md +++ b/docs/architecture/adr-008.md @@ -169,6 +169,3 @@ Accepted - Multi-sourced token is not supported. This is a deliberate design decision to avoid complicated supply management logic. ## References - -### x/erc20 module -- https://github.com/evmos/evmos/tree/main/x/erc20/spec diff --git a/docs/architecture/adr-010.md b/docs/architecture/adr-010.md new file mode 100644 index 0000000000..678d3d01e8 --- /dev/null +++ b/docs/architecture/adr-010.md @@ -0,0 +1,155 @@ +# ADR 010: Custom precompiled for app-chain + +## Changelog +* 2023-10-02: first draft + +## Context + +Cronos is an EVM-compatible built on Cosmos SDK. The "ethermint" module allows a full compatibility and interoperability with Ethereum. However, it comes with the sacrifice of cosmos native features or cosmos interchain features (IBC) +as end-users are not able to access them through an ethereum transaction. The solution is to provide precompile, allowing users to access to cosmos features through smart contracts. +A precompiled behave like a smart contract, it is designed by an address and can be invoked by other smart contracts. The difference is that its execution is not inside a smart contract. +App-chain specific logics can be embedded to the pre-compiled so that it could be used to expose cosmos native features at the EVM layer. + + +## Decision + +### Fork go-ethereum for stateful precompiled support + +One of the major difficulties in supporting pre-compiled is the lack of flexibility in geth for defining custom precompiled and its non-ability to modify the state. +We made the choice of forking geth and implement additional interfaces so that app-chain can define its own precompiled. + +The PR [#7](https://github.com/evmos/go-ethereum/pull/7) implements the ability to set custom precompiled to the EVM. +while this PR [#10](https://github.com/evmos/go-ethereum/pull/10) allows the precompiled to modify the state (for stateful precompiled) + +In the future, we are planning to maintain the following fork permanently +`github.com/evmos/go-ethereum` + +### Implement pre-compiled for cosmos native module + +We provide pre-compiles for cosmos native module such as bank module. + +```solidity + +interface IBankModule { + function mint(address,uint256) external payable returns (bool); + function balanceOf(address,address) external view returns (uint256); + function burn(address,uint256) external payable returns (bool); + function transfer(address,address,uint256) external payable returns (bool); +} + + +``` +The input and output of methods are mapped with those defined cosmos native transactions. +Because the precompiled is called at the evm layer, it uses the evm authentication instead of the cosmos authentication for transactions. +It is important to define for each precompiled module the range of action "authorized" for each request. +For the bank module, the precompiled is authenticated with `msg.sender` address. The smart contracts or users can only mint/burn cosmos coins denoted by the denom `evm/0x{msg.sender}` or transfer coins from the `0x{msg.sender}` account. + + +To call a precompiled from a smart contract, create an instance of the module interface with the precompiled address. +The methods are ABI encoded, and can be called directly as calling the function through the interface: + +```solidity + +address constant bankContract = 0x0000000000000000000000000000000000000064; +IBankModule bank = IBankModule(bankContract); +bank.transfer(msg.sender, recipient, amount); + +``` + + +### Implement pre-compiled for cosmos interchain communication + +#### Relayer +One of the benefits of supporting precompiled for IBC is that it would be possible to track the change of state triggered by the ibc transaction with ethereum receipts. + +For that reason we are exposing all relayer related actions to the evm layer. An action is defined by a 4 bytes prefix. + +```go + +const ( + prefixSize4Bytes = 4 + // Client + prefixCreateClient = iota + 1 + prefixUpdateClient + prefixUpgradeClient + prefixSubmitMisbehaviour + // Connection + prefixConnectionOpenInit + prefixConnectionOpenTry + prefixConnectionOpenAck + prefixConnectionOpenConfirm + // Channel + prefixChannelOpenInit + prefixChannelOpenTry + prefixChannelOpenAck + prefixChannelOpenConfirm + prefixChannelCloseInit + prefixChannelCloseConfirm + prefixRecvPacket + prefixAcknowledgement + prefixTimeout + prefixTimeoutOnClose +) + +``` + +-> TODO describe the change in go-relayer + +#### ICA + +The ICA precompiled interface is defined by : + +```solidity +interface IICAModule { + event SubmitMsgsResult(uint64 seq); + + function registerAccount(string calldata connectionID, string calldata version) external payable returns (bool); + function queryAccount(string calldata connectionID, address addr) external view returns (string memory); + function submitMsgs(string calldata connectionID, bytes calldata data, uint256 timeout) external payable returns (uint64); +} +``` +The request is authenticated by `msg.sender` and it can only send request on behalf of this account. + +The calldata in `submitMsgs` represents the cosmos proto-encoded message to be sent to the destination app-chain. Only one message can be sent at the moment. + +For example to call a bank transaction to another app-chain : + +```solidity + + function ICACallBank(string memory connectionID, uint256 timeout, params.....) public returns (uint64) { + msg = bankMsgSendProto.encode(params) + lastSeq = ica.submitMsgs(connectionID, msg, timeout); + return lastSeq; + } + +``` + +In case of ICA, it is also important to be able to track the result of the transaction `submitMsgs` so that the user or the smart contract can respond accordingly. +The function `submitMsgs` returns a sequence number that can be used by the user or smart contract to track the state of the msg using the precompiled `ICACallback`. + + +```solidity +interface IICACallback { + function onPacketResultCallback(uint64 seq, bool ack) external payable returns (bool); +} + +``` + + +### Precompiled gas cost + +A precompiled is basically an op-code at the evm layer thus, it has a constant cost. Because a stateful precompiled can change the state, it is much harder to define a specific cost. +To be fair, we are evaluating the cost of a pre-compile based on the average cost of the cosmos transaction in the past history. +Future work aim to provide a more accurate cost on the pre-compiled + +## Further discussions + +- Disabling cosmos native modules in cronos +- Establishing a standard for ibc for evm based chain (relayer) +- Extending the usage of pre-compile for broader use cases + +## References + +* https://github.com/crypto-org-chain/cronos/pull/837 +* https://github.com/crypto-org-chain/cronos/pull/1163 +* https://github.com/crypto-org-chain/cronos/pull/1014 \ No newline at end of file