Permit2 introduces a low-overhead, next-generation token approval/meta-tx system to make token approvals easier, more secure, and more consistent across applications.

• Signature Based Approvals: Any ERC20 token, even those that do not support EIP-2612, can now use permit style approvals. This allows applications to have a single transaction flow by sending a permit signature along with the transaction data when using Permit2 integrated contracts.
• Batched Token Approvals: Set permissions on different tokens to different spenders with one signature.
• Signature Based Token Transfers: Owners can sign messages to transfer tokens directly to signed spenders, bypassing setting any allowance. This means that approvals aren't necessary for applications to receive tokens and that there will never be hanging approvals when using this method. The signature is valid only for the duration of the transaction in which it is spent.
• Batched Token Transfers: Transfer different tokens to different recipients with one signature.
• Safe Arbitrary Data Verification: Verify any extra data by passing through a witness hash and witness type. The type string must follow the EIP-712 standard.
• Signature Verification for Contracts: All signature verification supports EIP-1271 so contracts can approve tokens and transfer tokens through signatures.
• Non-monotonic Replay Protection: Signature based transfers use unordered, non-monotonic nonces so that signed permits do not need to be transacted in any particular order.
• Expiring Approvals: Approvals can be time-bound, removing security concerns around hanging approvals on a wallet’s entire token balance. This also means that revoking approvals do not necessarily have to be a new transaction since an approval that expires will no longer be valid.
• Batch Revoke Allowances: Remove allowances on any number of tokens and spenders in one transaction.

Permit2 is the union of two contracts: AllowanceTransfer and SignatureTransfer.

The SignatureTransfer contract handles all signature-based transfers, meaning that an allowance on the token is bypassed and permissions to the spender only last for the duration of the transaction that the one-time signature is spent.

The AllowanceTransfer contract handles setting allowances on tokens, giving permissions to spenders on a specified amount for a specified duration of time. Any transfers that then happen through the AllowanceTransfer contract will only succeed if the proper permissions have been set.

Before integrating, contracts can request users’ tokens through Permit2, users must approve the Permit2 contract through the specific token contract. To see a detailed technical reference, visit the Uniswap documentation site.

Permit2 uses viaIR compilation, so importing and deploying it in an integration for tests will require the integrating repository to also use viaIR compilation. This is often quite slow, so can be avoided using the precompiled DeployPermit2 utility:

import {DeployPermit2} from "permit2/test/utils/DeployPermit2.sol";

contract MyTest is DeployPermit2 {
    address permit2;

    function setUp() public {
        permit2 = deployPermit2();
    }
}

This repository is subject to the Uniswap Labs Bug Bounty program, per the terms defined here.

You will need a copy of Foundry installed before proceeding. See the installation guide for details.

git clone https://github.com/Uniswap/permit2.git
cd permit2
forge install

forge fmt [--check]

# unit
forge test

# integration
source .env
FOUNDRY_PROFILE=integration forge test

forge snapshot

Run the command below. Remove --broadcast, ---rpc-url, --private-key and --verify options to test locally

forge script --broadcast --rpc-url <RPC-URL> --private-key <PRIVATE_KEY> --verify script/DeployPermit2.s.sol:DeployPermit2

Inspired by merklejerk's permit-everywhere contracts which introduce permit based approvals for all tokens regardless of EIP2612 support.

This is an implementation of the Uniswap Permit2 on the Kaia mainnet aimed at increasing adoption and user experience on the Kaia chain.

paulelisha@Macbook-M3-Pro permit2 % forge create --rpc-url https://public-en.node.kaia.io --private-key 3a5a4358e80d31101bb7705c84a9f0f85ced7aed9dd9b5c3f5eff6afad87b385 src/Permit2.sol:Permit2 --broadcast
[⠊] Compiling...
No files changed, compilation skipped
Deployer: 0x1bAB6c36d216F27730519DFa284A4587B26182CB
Deployed to: 0x8432A544B7669409aE6dBb10b63611A1fbD49a6B
Transaction hash: 0xc5e939a0d0251d3bbbe5c8af026a481509279b75e4f7766bba3a47fa3314a04c
paulelisha@Macbook-M3-Pro permit2 % forge verify-contract 0x8432A544B7669409aE6dBb10b63611A1fbD49a6B src/Permit2.sol:Permit2 --chain-id 8217 --verifier sourcify  --verifier-url https://sourcify.dev/server/  
Start verifying contract `0x8432A544B7669409aE6dBb10b63611A1fbD49a6B` deployed on 8217

Submitting verification for [Permit2] "0x8432A544B7669409aE6dBb10b63611A1fbD49a6B".
The recompiled contract partially matches the deployed version
paulelisha@Macbook-M3-Pro permit2 % 

Contract Name:
Permit2
Compilation Target:
src/Permit2.sol:Permit2
Language:
Solidity
Compiler:
solc 0.8.17+commit.8df45f5f
EVM Version:
london