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keccak256,
toHex,
encodePacked,
decodeAbiParameters,
parseAbiParameters,
} from 'viem';
import { DELEGATION_TYPES, ROOT_AUTHORITY } from '../constants.ts';
import type {
Action,
Address,
Caveat,
Delegation,
DelegationMatchResult,
Eip712TypedData,
Hex,
} from '../types.ts';
const harden = globalThis.harden ?? (<T>(value: T): T => value);
/**
* Generate a deterministic delegation ID from its components.
*
* @param delegation - The delegation to compute the ID for.
* @param delegation.delegator - The delegator address.
* @param delegation.delegate - The delegate address.
* @param delegation.authority - The parent delegation hash.
* @param delegation.salt - The delegation salt.
* @returns The delegation ID as a hex hash.
*/
export function computeDelegationId(delegation: {
delegator: Address;
delegate: Address;
authority: Hex;
salt: Hex;
}): string {
return keccak256(
encodePacked(
['address', 'address', 'bytes32', 'uint256'],
[
delegation.delegator,
delegation.delegate,
delegation.authority,
BigInt(delegation.salt),
],
),
);
}
/**
* A function that generates a unique delegation salt on each call.
*/
export type SaltGenerator = () => Hex;
/**
* Create a salt generator for delegation uniqueness.
*
* Prefers crypto.getRandomValues when available. In SES compartments
* where crypto is not endowed, falls back to a closure-local counter
* hashed with optional caller-supplied entropy. Each call to
* makeSaltGenerator produces an independent counter, so two vat instances
* each get their own sequence rather than sharing module-level state.
*
* @param entropy - Optional caller-supplied entropy hex string. When provided
* and crypto is unavailable, mixed into the counter hash so that separate
* vat instances produce distinct salts even though both start at counter 1.
* @returns A salt generator function.
*/
export function makeSaltGenerator(entropy?: Hex): SaltGenerator {
// eslint-disable-next-line n/no-unsupported-features/node-builtins
Eif (globalThis.crypto?.getRandomValues) {
return () => {
const bytes = new Uint8Array(32);
// eslint-disable-next-line n/no-unsupported-features/node-builtins
globalThis.crypto.getRandomValues(bytes);
return toHex(bytes);
};
}
// SES fallback: unique per generator lifetime but not cryptographically random.
// The salt only needs uniqueness, not unpredictability.
let counter = 0;
if (entropy !== undefined) {
return () => {
counter += 1;
return keccak256(
encodePacked(['bytes', 'uint256'], [entropy, BigInt(counter)]),
);
};
}
return () => {
counter += 1;
return keccak256(encodePacked(['uint256'], [BigInt(counter)]));
};
}
/**
* Generate a random salt for delegation uniqueness.
*
* Uses a module-level counter as the SES fallback. Prefer
* {@link makeSaltGenerator} when creating delegations in a vat, since it
* gives each vat instance an independent counter.
*
* @returns A hex-encoded random salt.
*/
export const generateSalt: SaltGenerator = makeSaltGenerator();
/**
* Create a new unsigned delegation struct.
*
* @param options - Creation options.
* @param options.delegator - The account granting the delegation.
* @param options.delegate - The account receiving the delegation.
* @param options.caveats - The caveats restricting the delegation.
* @param options.chainId - The chain ID.
* @param options.salt - Optional salt (generated if omitted).
* @param options.saltGenerator - Optional salt generator to use when no
* explicit salt is provided. Defaults to {@link generateSalt}.
* @param options.authority - Optional parent delegation hash (root if omitted).
* @returns The unsigned Delegation struct.
*/
export function makeDelegation(options: {
delegator: Address;
delegate: Address;
caveats: Caveat[];
chainId: number;
salt?: Hex;
saltGenerator?: SaltGenerator;
authority?: Hex;
}): Delegation {
const salt = options.salt ?? (options.saltGenerator ?? generateSalt)();
const authority = options.authority ?? ROOT_AUTHORITY;
const id = computeDelegationId({
delegator: options.delegator,
delegate: options.delegate,
authority,
salt,
});
return harden({
id,
delegator: options.delegator,
delegate: options.delegate,
authority,
caveats: options.caveats,
salt,
chainId: options.chainId,
status: 'pending',
});
}
/**
* Prepare the EIP-712 typed data payload for signing a delegation.
*
* @param options - Options.
* @param options.delegation - The delegation to prepare for signing.
* @param options.verifyingContract - The DelegationManager contract address.
* @returns The EIP-712 typed data payload.
*/
export function prepareDelegationTypedData(options: {
delegation: Delegation;
verifyingContract: Address;
}): Eip712TypedData {
const { delegation, verifyingContract } = options;
return {
domain: {
name: 'DelegationManager',
version: '1',
chainId: delegation.chainId,
verifyingContract,
},
types: {
...DELEGATION_TYPES,
},
primaryType: 'Delegation',
message: {
delegate: delegation.delegate,
delegator: delegation.delegator,
authority: delegation.authority,
caveats: delegation.caveats.map((caveat) => ({
enforcer: caveat.enforcer,
terms: caveat.terms,
})),
salt: BigInt(delegation.salt),
},
};
}
/**
* Explain whether a signed delegation potentially covers an action.
*
* Returns a detailed result indicating whether the delegation matches,
* and if not, which caveat failed and why.
*
* This performs a client-side check based on the caveat types:
* - allowedTargets: checks if action.to is in the allowed list
* - allowedMethods: checks if action.data starts with an allowed selector
* - valueLte: checks if action.value is within the limit
* - timestamp: checks if current time is within the window
* - erc20TransferAmount: checks token, selector, and amount
* - nativeTokenTransferAmount: cannot be enforced client-side (requires on-chain accounting)
*
* This is a best-effort match. On-chain enforcement is authoritative.
*
* @param delegation - The delegation to check.
* @param action - The action to match against.
* @param currentTime - Optional current time in milliseconds (defaults to Date.now()).
* @returns A result object with match status and failure details.
*/
export function explainDelegationMatch(
delegation: Delegation,
action: Action,
currentTime?: number,
): DelegationMatchResult {
if (delegation.status !== 'signed') {
return { matches: false, reason: 'Delegation is not signed' };
}
// Check each caveat - all must pass for the delegation to match
for (const caveat of delegation.caveats) {
if (caveat.type === 'allowedTargets') {
// Packed 20-byte addresses (40 hex chars each, after '0x' prefix).
const termsBody = caveat.terms.slice(2);
const targets: string[] = [];
for (let i = 0; i < termsBody.length; i += 40) {
targets.push(`0x${termsBody.slice(i, i + 40)}`);
}
const match = targets.some(
(target) => target.toLowerCase() === action.to.toLowerCase(),
);
if (!match) {
return {
matches: false,
failedCaveat: 'allowedTargets',
reason: `Target ${action.to} is not in the allowed targets list`,
};
}
}
if (caveat.type === 'allowedMethods' && action.data) {
const selector = action.data.slice(0, 10).toLowerCase() as Hex;
// Packed 4-byte selectors (8 hex chars each, after '0x' prefix).
const termsBody = caveat.terms.slice(2);
const methods: string[] = [];
for (let i = 0; i < termsBody.length; i += 8) {
methods.push(`0x${termsBody.slice(i, i + 8)}`);
}
const match = methods.some((method) => method.toLowerCase() === selector);
if (!match) {
return {
matches: false,
failedCaveat: 'allowedMethods',
reason: `Method selector ${selector} is not in the allowed methods list`,
};
}
}
if (caveat.type === 'valueLte') {
const [maxValue] = decodeAbiParameters(
parseAbiParameters('uint256'),
caveat.terms,
);
const actionValue = action.value ? BigInt(action.value) : 0n;
if (actionValue > maxValue) {
return {
matches: false,
failedCaveat: 'valueLte',
reason: `Value ${actionValue} exceeds maximum ${maxValue}`,
};
}
}
if (caveat.type === 'timestamp') {
const [after, before] = decodeAbiParameters(
parseAbiParameters('uint128, uint128'),
caveat.terms,
);
Iif (
currentTime === undefined &&
typeof globalThis.Date?.now !== 'function'
) {
return {
matches: false,
failedCaveat: 'timestamp',
reason:
'Cannot evaluate timestamp caveat: Date.now() is not available (SES compartment) and no currentTime was provided',
};
}
const now = BigInt(Math.floor((currentTime ?? Date.now()) / 1000));
if (now < after) {
return {
matches: false,
failedCaveat: 'timestamp',
reason: `Current time ${now} is before the allowed window (starts at ${after})`,
};
}
if (now > before) {
return {
matches: false,
failedCaveat: 'timestamp',
reason: `Current time ${now} is after the allowed window (ended at ${before})`,
};
}
}
if (caveat.type === 'erc20TransferAmount') {
// Packed: 20-byte address (40 hex chars) + 32-byte uint256 (64 hex chars).
const erc20Hex = caveat.terms.slice(2);
const token = `0x${erc20Hex.slice(0, 40)}`;
const maxAmount = BigInt(`0x${erc20Hex.slice(40, 104)}`);
if (action.to.toLowerCase() !== token.toLowerCase()) {
return {
matches: false,
failedCaveat: 'erc20TransferAmount',
reason: `Target ${action.to} does not match token contract ${token}`,
};
}
if (!action.data || action.data.length < 138) {
return {
matches: false,
failedCaveat: 'erc20TransferAmount',
reason: 'Missing or incomplete ERC-20 transfer calldata',
};
}
const selector = action.data.slice(0, 10).toLowerCase();
Iif (selector !== '0xa9059cbb') {
return {
matches: false,
failedCaveat: 'erc20TransferAmount',
reason: `Selector ${selector} is not transfer(address,uint256)`,
};
}
const amountHex = `0x${action.data.slice(74, 138)}`;
const transferAmount = BigInt(amountHex);
if (transferAmount > maxAmount) {
return {
matches: false,
failedCaveat: 'erc20TransferAmount',
reason: `Transfer amount ${transferAmount} exceeds maximum ${maxAmount}`,
};
}
}
// limitedCalls: Cannot enforce client-side (requires on-chain call counter).
// nativeTokenTransferAmount: Cannot enforce client-side (requires on-chain accounting).
// The on-chain enforcers are authoritative — pass through.
}
return { matches: true };
}
/**
* Check whether a signed delegation potentially covers an action.
*
* This is a convenience wrapper around {@link explainDelegationMatch}
* that returns a simple boolean.
*
* @param delegation - The delegation to check.
* @param action - The action to match against.
* @param currentTime - Optional current time in milliseconds (defaults to Date.now()).
* @returns True if the delegation might cover the action.
*/
export function delegationMatchesAction(
delegation: Delegation,
action: Action,
currentTime?: number,
): boolean {
return explainDelegationMatch(delegation, action, currentTime).matches;
}
/**
* Mark a delegation as signed with the given signature.
*
* @param delegation - The delegation to finalize.
* @param signature - The EIP-712 signature.
* @returns The signed delegation.
*/
export function finalizeDelegation(
delegation: Delegation,
signature: Hex,
): Delegation {
return harden({
...delegation,
signature,
status: 'signed',
});
}
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