Permit2
Permit2 handles signature-based transfers in SignatureTransfer and allowance-based transfers in AllowanceTransfer.
Users must approve Permit2 before calling any of the transfer functions.
State Variables
allowance
Maps users to tokens to spender addresses and information about the approval on the token
Indexed in the order of token owner address, token address, spender address
The stored word saves the allowed amount, expiration on the allowance, and nonce
mapping(address => mapping(address => mapping(address => PackedAllowance))) public allowance;nonceBitmap
A map from token owner address and a caller specified word index to a bitmap. Used to set bits in the bitmap to prevent against signature replay protection
Uses unordered nonces so that permit messages do not need to be spent in a certain order
mapping(address => mapping(uint256 => uint256)) public nonceBitmap;Functions
permitTransferFrom
Transfers a token using a signed permit message
Reverts if the requested amount is greater than the permitted signed amount
function permitTransferFrom(
PermitTransferFrom memory permit,
SignatureTransferDetails calldata transferDetails,
address owner,
bytes calldata signature
) external;Parameters
| Name | Type | Description |
|---|---|---|
permit | PermitTransferFrom | The permit data signed over by the owner |
transferDetails | SignatureTransferDetails | The spender's requested transfer details for the permitted token |
owner | address | The owner of the tokens to transfer |
signature | bytes | The signature to verify |
permitWitnessTransferFrom
Transfers a token using a signed permit message
The witness type string must follow EIP712 ordering of nested structs and must include the TokenPermissions type definition
function permitWitnessTransferFrom(
PermitTransferFrom memory permit,
SignatureTransferDetails calldata transferDetails,
address owner,
bytes32 witness,
string calldata witnessTypeString,
bytes calldata signature
) external;Parameters
| Name | Type | Description |
|---|---|---|
permit | PermitTransferFrom | The permit data signed over by the owner |
transferDetails | SignatureTransferDetails | The spender's requested transfer details for the permitted token |
owner | address | The owner of the tokens to transfer |
witness | bytes32 | Extra data to include when checking the user signature |
witnessTypeString | string | The EIP-712 type definition for remaining string stub of the typehash |
signature | bytes | The signature to verify |
_permitTransferFrom
Transfers a token using a signed permit message.
function _permitTransferFrom(
PermitTransferFrom memory permit,
SignatureTransferDetails calldata transferDetails,
address owner,
bytes32 dataHash,
bytes calldata signature
) private;Parameters
| Name | Type | Description |
|---|---|---|
permit | PermitTransferFrom | The permit data signed over by the owner |
transferDetails | SignatureTransferDetails | The spender's requested transfer details for the permitted token |
owner | address | The owner of the tokens to transfer |
dataHash | bytes32 | The EIP-712 hash of permit data to include when checking signature |
signature | bytes | The signature to verify |
permitTransferFrom
Transfers a token using a signed permit message
Reverts if the requested amount is greater than the permitted signed amount
function permitTransferFrom(
PermitBatchTransferFrom memory permit,
SignatureTransferDetails[] calldata transferDetails,
address owner,
bytes calldata signature
) external;Parameters
| Name | Type | Description |
|---|---|---|
permit | PermitBatchTransferFrom | The permit data signed over by the owner |
transferDetails | SignatureTransferDetails[] | The spender's requested transfer details for the permitted token |
owner | address | The owner of the tokens to transfer |
signature | bytes | The signature to verify |
permitWitnessTransferFrom
Transfers a token using a signed permit message
The witness type string must follow EIP712 ordering of nested structs and must include the TokenPermissions type definition
function permitWitnessTransferFrom(
PermitBatchTransferFrom memory permit,
SignatureTransferDetails[] calldata transferDetails,
address owner,
bytes32 witness,
string calldata witnessTypeString,
bytes calldata signature
) external;Parameters
| Name | Type | Description |
|---|---|---|
permit | PermitBatchTransferFrom | The permit data signed over by the owner |
transferDetails | SignatureTransferDetails[] | The spender's requested transfer details for the permitted token |
owner | address | The owner of the tokens to transfer |
witness | bytes32 | Extra data to include when checking the user signature |
witnessTypeString | string | The EIP-712 type definition for remaining string stub of the typehash |
signature | bytes | The signature to verify |
_permitTransferFrom
Transfers tokens using a signed permit messages
function _permitTransferFrom(
PermitBatchTransferFrom memory permit,
SignatureTransferDetails[] calldata transferDetails,
address owner,
bytes32 dataHash,
bytes calldata signature
) private;Parameters
| Name | Type | Description |
|---|---|---|
permit | PermitBatchTransferFrom | The permit data signed over by the owner |
transferDetails | SignatureTransferDetails[] | |
owner | address | The owner of the tokens to transfer |
dataHash | bytes32 | The EIP-712 hash of permit data to include when checking signature |
signature | bytes | The signature to verify |
invalidateUnorderedNonces
Invalidates the bits specified in mask for the bitmap at the word position
The wordPos is maxed at type(uint248).max
function invalidateUnorderedNonces(uint256 wordPos, uint256 mask) external;Parameters
| Name | Type | Description |
|---|---|---|
wordPos | uint256 | A number to index the nonceBitmap at |
mask | uint256 | A bitmap masked against msg.sender's current bitmap at the word position |
bitmapPositions
Returns the index of the bitmap and the bit position within the bitmap. Used for unordered nonces
The first 248 bits of the nonce value is the index of the desired bitmap
The last 8 bits of the nonce value is the position of the bit in the bitmap
function bitmapPositions(uint256 nonce) private pure returns (uint256 wordPos, uint256 bitPos);Parameters
| Name | Type | Description |
|---|---|---|
nonce | uint256 | The nonce to get the associated word and bit positions |
Returns
| Name | Type | Description |
|---|---|---|
wordPos | uint256 | The word position or index into the nonceBitmap |
bitPos | uint256 | The bit position |
_useUnorderedNonce
Checks whether a nonce is taken and sets the bit at the bit position in the bitmap at the word position
function _useUnorderedNonce(address from, uint256 nonce) internal;Parameters
| Name | Type | Description |
|---|---|---|
from | address | The address to use the nonce at |
nonce | uint256 | The nonce to spend |
approve
Approves the spender to use up to amount of the specified token up until the expiration
The packed allowance also holds a nonce, which will stay unchanged in approve
function approve(address token, address spender, uint160 amount, uint48 expiration) external;Parameters
| Name | Type | Description |
|---|---|---|
token | address | The token to approve |
spender | address | The spender address to approve |
amount | uint160 | The approved amount of the token |
expiration | uint48 | The timestamp at which the approval is no longer valid |
permit
Permit a spender to a given amount of the owners token via the owner's EIP-712 signature
May fail if the owner's nonce was invalidated in-flight by invalidateNonce
function permit(address owner, PermitSingle memory permitSingle, bytes calldata signature)
external;Parameters
| Name | Type | Description |
|---|---|---|
owner | address | The owner of the tokens being approved |
permitSingle | PermitSingle | Data signed over by the owner specifying the terms of approval |
signature | bytes | The owner's signature over the permit data |
permit
Permit a spender to a given amount of the owners token via the owner's EIP-712 signature
May fail if the owner's nonce was invalidated in-flight by invalidateNonce
function permit(address owner, PermitBatch memory permitBatch, bytes calldata signature) external;Parameters
| Name | Type | Description |
|---|---|---|
owner | address | The owner of the tokens being approved |
permitBatch | PermitBatch | |
signature | bytes | The owner's signature over the permit data |
transferFrom
Transfer approved tokens from one address to another
Requires the from address to have approved at least the desired amount of tokens to msg.sender.
function transferFrom(address from, address to, uint160 amount, address token) external;Parameters
| Name | Type | Description |
|---|---|---|
from | address | The address to transfer from |
to | address | The address of the recipient |
amount | uint160 | The amount of the token to transfer |
token | address | The token address to transfer |
transferFrom
Transfer approved tokens from one address to another
Requires the from address to have approved at least the desired amount of tokens to msg.sender.
function transferFrom(AllowanceTransferDetails[] calldata transferDetails) external;Parameters
| Name | Type | Description |
|---|---|---|
transferDetails | AllowanceTransferDetails[] |
_transfer
Internal function for transferring tokens using stored allowances
Will fail if the allowed timeframe has passed
function _transfer(address from, address to, uint160 amount, address token) private;lockdown
Enables performing a "lockdown" of the sender's Permit2 identity by batch revoking approvals
function lockdown(TokenSpenderPair[] calldata approvals) external;Parameters
| Name | Type | Description |
|---|---|---|
approvals | TokenSpenderPair[] | Array of approvals to revoke. |
invalidateNonces
Invalidate nonces for a given (token, spender) pair
Can't invalidate more than 2**16 nonces per transaction.
function invalidateNonces(address token, address spender, uint48 newNonce) external;Parameters
| Name | Type | Description |
|---|---|---|
token | address | The token to invalidate nonces for |
spender | address | The spender to invalidate nonces for |
newNonce | uint48 | The new nonce to set. Invalidates all nonces less than it. |
_updateApproval
Sets the new values for amount, expiration, and nonce.
Will check that the signed nonce is equal to the current nonce and then incrememnt the nonce value by 1.
Emits a Permit event.
function _updateApproval(PermitDetails memory details, address owner, address spender) private;