Avalanche Interchain Token Transfer (ICTT) is an application that allows users to transfer tokens between Subnets. The implementation is a set of smart contracts that are deployed across multiple Subnets, and leverages Teleporter for cross-chain communication.
Each token transferrer instance consists of one "home" contract and at least one but possibly many "remote" contracts. Each home contract instance manages one asset to be transferred out to TokenRemote instances. The home contract lives on the Subnet where the asset to be transferred exists. A transfer consists of locking the asset as collateral on the home Subnet and minting a representation of the asset on the remote Subnet. The remote contracts, each of which has a single specified home contract, live on other Subnets that want to import the asset transferred by their specified home. The token transferrers are designed to be permissionless: anyone can register compatible TokenRemote instances to allow for transferring tokens from the TokenHome instance to that new TokenRemote instance. The home contract keeps track of token balances transferred to each TokenRemote instance, and handles returning the original tokens back to the user when assets are transferred back to the TokenHome instance. TokenRemote instances are registered with their home contract via a Teleporter message upon creation.
Home contract instances specify the asset to be transferred as either an ERC20 token or the native token, and they allow for transferring the token to any registered TokenRemote instances. The token representation on the remote chain can also either be an ERC20 or native token, allowing users to have any combination of ERC20 and native tokens between home and remote chains:
ERC20->ERC20ERC20->NativeNative->ERC20Native->Native
The remote tokens are designed to have compatibility with the token transferrer on the home chain by default, and they allow custom logic to be implemented in addition. For example, developers can inherit and extend the ERC20TokenRemote contract to add additional functionality, such as a custom minting, burning, or transfer logic.
The token transferrer also supports "multi-hop" transfers, where tokens can be transferred between remote chains. To illustrate, consider two remotes Ra and Rb that are both connected to the same home H. A multi-hop transfer from Ra to Rb first gets routed from Ra to H, where remote balances are updated, and then H automatically routes the transfer on to Rb.
In addition to supporting basic token transfers, the token transferrer contracts offer a sendAndCall interface for transferring tokens and using them in a smart contract interaction all within a single Teleporter message. If the call to the recipient smart contract fails, the transferred tokens are sent to a fallback recipient address on the destination chain of the transfer. The sendAndCall interface enables the direct use of transferred tokens in dApps on other chains, such as performing swaps, using the tokens to pay for fees when invoking services, etc.
A breakdown of the structure of the contracts that implement this function can be found under ./contracts here.
Some contracts in this repository have been audited. The main branch may contain unaudited code. Please check here for which versions of each contract have been audited.
DO NOT USE UN-AUDITED CODE IN PRODUCTION!
The avalanche-interchain-token-transfer contracts are non-upgradeable and cannot be changed once it is deployed. This provides immutability to the contracts, and ensures that the contract's behavior at each address is unchanging.
- Get all submodules:
git submodule update --init --recursive
contracts/is a Foundry project that includes the implementation of the token transferrer contracts and Solidity unit testsscripts/includes various bash utility scriptstests/includes integration tests for the contracts incontracts/, written using the Ginkgo testing framework.
Unit tests are written under contracts/test/ and can be run with forge:
cd contracts
forge test -vvv
Unit test coverage of the contracts can be viewed using forge coverage:
$ forge coverage
[⠢] Compiling...
[⠒] Compiling 78 files with 0.8.25
[⠆] Solc 0.8.25 finished in 3.92s
Compiler run successful!
Analysing contracts...
Running tests...
| File | % Lines | % Statements | % Branches | % Funcs |
|--------------------------------------------------|-------------------|-------------------|-----------------|-------------------|
| src/TokenHome/ERC20TokenHome.sol | 100.00% (1/1) | 100.00% (1/1) | 100.00% (0/0) | 100.00% (1/1) |
| src/TokenHome/ERC20TokenHomeUpgradeable.sol | 100.00% (27/27) | 100.00% (33/33) | 100.00% (6/6) | 100.00% (11/11) |
| src/TokenHome/NativeTokenHome.sol | 100.00% (1/1) | 100.00% (1/1) | 100.00% (0/0) | 100.00% (1/1) |
| src/TokenHome/NativeTokenHomeUpgradeable.sol | 100.00% (24/24) | 100.00% (29/29) | 100.00% (4/4) | 100.00% (11/11) |
| src/TokenHome/TokenHome.sol | 100.00% (158/158) | 100.00% (198/198) | 100.00% (26/26) | 100.00% (22/22) |
| src/TokenRemote/ERC20TokenRemote.sol | 100.00% (1/1) | 100.00% (1/1) | 100.00% (0/0) | 100.00% (1/1) |
| src/TokenRemote/ERC20TokenRemoteUpgradeable.sol | 100.00% (36/36) | 100.00% (40/40) | 100.00% (10/10) | 100.00% (12/12) |
| src/TokenRemote/NativeTokenRemote.sol | 100.00% (1/1) | 100.00% (1/1) | 100.00% (0/0) | 100.00% (1/1) |
| src/TokenRemote/NativeTokenRemoteUpgradeable.sol | 100.00% (60/60) | 100.00% (74/74) | 100.00% (10/10) | 100.00% (19/19) |
| src/TokenRemote/TokenRemote.sol | 100.00% (118/118) | 100.00% (155/155) | 100.00% (12/12) | 100.00% (24/24) |
| src/WrappedNativeToken.sol | 100.00% (6/6) | 100.00% (6/6) | 100.00% (0/0) | 100.00% (4/4) |
| src/mocks/ExampleERC20Decimals.sol | 100.00% (2/2) | 100.00% (2/2) | 100.00% (0/0) | 100.00% (2/2) |
| src/mocks/MockERC20SendAndCallReceiver.sol | 100.00% (5/5) | 100.00% (5/5) | 100.00% (0/0) | 100.00% (2/2) |
| src/mocks/MockNativeSendAndCallReceiver.sol | 100.00% (4/4) | 100.00% (4/4) | 100.00% (0/0) | 100.00% (2/2) |
| src/utils/CallUtils.sol | 100.00% (8/8) | 100.00% (9/9) | 100.00% (2/2) | 100.00% (2/2) |
| src/utils/SafeERC20TransferFrom.sol | 100.00% (5/5) | 100.00% (8/8) | 100.00% (0/0) | 100.00% (1/1) |
| src/utils/SafeWrappedNativeTokenDeposit.sol | 100.00% (5/5) | 100.00% (8/8) | 100.00% (0/0) | 100.00% (1/1) |
| src/utils/SendReentrancyGuard.sol | 100.00% (8/8) | 100.00% (10/10) | 100.00% (0/0) | 100.00% (4/4) |
| src/utils/TokenScalingUtils.sol | 100.00% (8/8) | 100.00% (14/14) | 100.00% (2/2) | 100.00% (4/4) |
| Total | 100.00% (478/478) | 100.00% (599/599) | 100.00% (72/72) | 100.00% (125/125) |
End-to-end integration tests written using Ginkgo are provided in the tests/ directory. E2E tests are run as part of CI, but can also be run locally. Any new features or cross-chain example applications checked into the repository should be accompanied by an end-to-end tests.
To run the E2E tests locally, you'll need to install Gingko following the instructions here.
Then run the following command from the root of the repository:
./scripts/e2e_test.shTo run a specific E2E test, specify the environment variable GINKGO_FOCUS, which will then look for test descriptions that match the provided input. For example, to run the Transfer an ERC20 token between two Subnets test:
GINKGO_FOCUS="Transfer an ERC20 token between two Subnets" ./scripts/e2e_test.shA substring of the full test description can be used as well:
GINKGO_FOCUS="Transfer an ERC20 token" ./scripts/e2e_test.shThe E2E tests also supports GINKGO_LABEL_FILTER, making it easy to group test cases and run them together. For example, to run all ERC20TokenHome E2E tests:
ginkgo.It("Transfer an ERC20 token between two Subnets",
ginkgo.Label(erc20TokenHomeLabel, erc20TokenRemoteLabel),
func() {
flows.ERC20TokenHomeERC20TokenRemote(LocalNetworkInstance)
})GINKGO_LABEL_FILTER="ERC20TokenHome" ./scripts/e2e_test.sh