Kroma Smart Contracts
This package contains the smart contracts that compose the on-chain component of Kroma. You can find detailed specifications for the contracts contained within this package here.
Contracts Overview
Contracts deployed to L1
Name | Proxy Type | Description |
---|---|---|
L1CrossDomainMessenger |
Proxy |
|
High-level interface for sending messages to and receiving messages from Kroma | ||
L1StandardBridge |
Proxy |
|
Standardized system for transfering ERC20 tokens to/from Kroma | ||
L2OutputOracle |
Proxy |
|
Stores commitments to the state of Kroma which can be used by contracts on L1 to access L2 state | ||
KromaPortal |
Proxy |
|
Low-level message passing interface | ||
KromaMintableERC20Factory |
Proxy |
|
Deploys standard KromaMintableERC20 tokens that are compatible with either StandardBridge
|
||
ProxyAdmin |
- | |
Contract that can upgrade L1 contracts |
Contracts deployed to L2
Name | Proxy Type | Description |
---|---|---|
GasPriceOracle |
Proxy |
Stores L2 gas price configuration values |
L1Block |
Proxy |
Stores L1 block context information (e.g., latest known L1 block hash) |
L2CrossDomainMessenger |
Proxy |
High-level interface for sending messages to and receiving messages from L1 |
L2StandardBridge |
Proxy |
Standardized system for transferring ERC20 tokens to/from L1 |
L2ToL1MessagePasser |
Proxy |
Low-level message passing interface |
ValidatorRewardVault |
Proxy |
Vault for L2 transaction fees |
KromaMintableERC20Factory |
Proxy |
Deploys standard KromaMintableERC20 tokens that are compatible with either StandardBridge
|
L2ProxyAdmin |
- | Contract that can upgrade L2 contracts when sent a transaction from L1 |
Installation
We export contract ABIs, contract source code, and contract deployment information for this package via npm
:
> npm install @kroma2/contracts
Development
Dependencies
We work on this repository with a combination of Hardhat and Foundry.
-
Install Foundry by following the instructions located here. A specific version must be used.
> foundryup --version nightly-d369d2486f85576eec4ca41d277391dfdae21ba7
-
Install node modules with yarn (v1) and Node.js (16+):
> yarn install
Build
> yarn build
Tests
> yarn test
Running Echidna tests
You must have Echidna installed.
Contracts targeted for Echidna testing are located in ./contracts/echidna
Each target contract is tested with a separate yarn command, for example:
> yarn echidna:aliasing
Deployment
Configuration
- Create or modify a file
<network-name>.ts
inside of thedeploy-config
folder. - Fill out this file according to the
deployConfigSpec
located inside of thehardhat.config.ts
. - Optionally: Run
npx hardhat generate-deploy-config --network <network-name>
to generate the associated JSON file. This is required if usingutils/chain-ops
.
Execution
- Copy
.env.example
into.env
- Fill out the
L1_RPC
andPRIVATE_KEY_DEPLOYER
environment variables in.env
- Run
npx hardhat deploy --network <network-name>
to deploy the L1 contracts - Run
npx hardhat etherscan-verify --network <network-name> --sleep
to verify contracts on Etherscan
Tools
Layout Locking
We use a system called "layout locking" as a safety mechanism to prevent certain contract variables from being moved to
different storage slots accidentally.
To lock a contract variable, add it to the layout-lock.json
file which has the following format:
{
"MyContractName": {
"myVariableName": {
"slot": 1,
"offset": 0,
"length": 32
}
}
}
With the above config, the validate-spacers
hardhat task will check that we have a contract called MyContractName
,
that the contract has a variable named myVariableName
, and that the variable is in the correct position
as defined in the lock file.
You should add things to the layout-lock.json
file when you want those variables to never change.
Layout locking should be used in combination with diffing the .storage-layout
file in CI.
Standards and Conventions
Style
Comments
We use Seaport-style comments with some minor modifications. Some basic rules:
- Always use
@notice
since it has the same general effect as@dev
but avoids confusion about when to use one over the other. - Include a newline between
@notice
and the first@param
. - Include a newline between
@param
and the first@return
. - Use a line-length of 100 characters.
We also have the following custom tags:
-
@custom:proxied
: Add to a contract whenever it's meant to live behind a proxy. -
@custom:upgradeable
: Add to a contract whenever it's meant to be used in an upgradeable contract. -
@custom:semver
: Add to a constructor to indicate the version of a contract.
Errors
- Use
require
statements when making simple assertions. - Use
revert
if throwing an error where an assertion is not being made (no custom errors). - Error strings MUST have the format
"{ContractName}: {message}"
wheremessage
is a lower case string.
Function Parameters
- Function parameters should be prefixed with an underscore.
Event Parameters
- Event parameters should NOT be prefixed with an underscore.
Spacers
We use spacer variables to account for old storage slots that are no longer being used.
The name of a spacer variable MUST be in the format spacer_<slot>_<offset>_<length>
where <slot>
is the original
storage slot number, <offset>
is the original offset position within the storage slot,
and <length>
is the original size of the variable.
Spacers MUST be private
.
Proxy by Default
All contracts should be assumed to live behind proxies (except in certain special circumstances).
This means that new contracts MUST be built under the assumption of upgradeability.
We use a minimal Proxy
contract designed to be owned
by a corresponding ProxyAdmin
which follow the interfaces of OpenZeppelin's Proxy
and ProxyAdmin
contracts, respectively.
Unless explicitly discussed otherwise, you MUST include the following basic upgradeability pattern for each new implementation contract:
- Extend OpenZeppelin's
Initializable
base contract. - Include a
uint8 public constant VERSION = X
at the TOP of your contract. - Include a function
initialize
with the modifierreinitializer(VERSION)
. - In the
constructor
, set anyimmutable
variables and call theinitialize
function for setting mutables.
Versioning
All (non-library and non-abstract) contracts MUST extend the Semver
base contract which exposes a version()
function
that returns a semver-compliant version string.
Before mainnet release, the development process the Semver
value for all contracts SHOULD return 0.1.0
After the mainnet release, contracts MUST use the following versioning scheme:
-
patch
releases are to be used only for changes that do NOT modify contract bytecode (such as updating comments). -
minor
releases are to be used for changes that modify bytecode OR changes that expand the contract ABI provided that these changes do NOT break the existing interface. -
major
releases are to be used for changes that break the existing contract interface OR changes that modify the security model of a contract.
Exceptions
We have made an exception to the Semver
rule for the WETH
contract to avoid making changes to a well-known, simple,
and recognizable contract.
Tests
Tests are written using Foundry.
All test contracts and functions should be organized and named according to the following guidelines.
These guidelines are also encoded in a script which can be run with:
> ts-node scripts/forge-test-names.ts
Note: This is a work in progress, not all test files are compliant with these guidelines.
Organizing Principles
- Solidity
contract
s are used to organize the test suite similar to how mocha uses describe. - Every non-trivial state changing function should have a separate contract for happy and sad path tests. This helps to make it very obvious where there are not yet sad path tests.
- Simpler functions like getters and setters are grouped together into test contracts.
Test function naming convention
Test function names are split by underscores, into 3 or 4 parts.
An example function name is test_onlyOwner_callerIsNotOwner_reverts()
.
The parts are: [method]_[FunctionName]_[reason]_[success]
, where:
-
[method]
is eithertest
,testFuzz
, ortestDiff
-
[FunctionName]
is the name of the function or higher level behavior being tested. -
[reason]
is an optional description for the behavior being tested. -
[status]
must be one of:-
succeeds
: used for most happy path cases -
reverts
: used for most sad path cases -
works
: used for tests which include a mix of happy and sad assertions (these should be broken up if possible) -
fails
: used for tests which 'fail' in some way other than reverting -
benchmark
: used for tests intended to establish gas costs
-
Contract Naming Conventions
Test contracts should be named one of the following according to their use:
-
TargetContract_Init
for contracts that perform basic setup to be reused in other test contracts. -
TargetContract_Function_Test
for contracts containing happy path tests for a given function. -
TargetContract_Function_TestFail
for contracts containing sad path tests for a given function.
Withdrawing From Fee Vaults
See the file scripts/FeeVaultWithdrawal.s.sol
to withdraw from the L2 fee vaults. It includes
instructions on how to run it. foundry
is required.