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Merge pull request #2 from d3or/d3or/add-cache
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feat: add cache & cache clearing job
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@d3or
d3or authored Jul 12, 2024
2 parents b93282d + dc6941a commit 4e1cc8a
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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,7 @@ yarn add @d3or/slotseek

## TODO

- [ ] Add caching options to reduce the number of RPC calls and reduce the time it takes to find the same slot again
- [X] Add caching options to reduce the number of RPC calls and reduce the time it takes to find the same slot again

## Example of overriding a users balance via eth_call

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194 changes: 111 additions & 83 deletions src/approval.ts
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import { ethers } from "ethers";
import { approvalCache } from "./cache";

/**
* Generate mock approval data for a given ERC20 token
Expand Down Expand Up @@ -114,6 +115,27 @@ export const getErc20ApprovalStorageSlot = async (
slotHash: string;
isVyper: boolean;
}> => {
// check the cache
const cachedValue = approvalCache.get(erc20Address.toLowerCase());
if (cachedValue) {
if (cachedValue.isVyper) {
const { vyperSlotHash } = calculateApprovalVyperStorageSlot(ownerAddress, spenderAddress, cachedValue.slot)
return {
slot: ethers.BigNumber.from(cachedValue.slot).toHexString(),
slotHash: vyperSlotHash,
isVyper: true,
};

} else {
const { slotHash } = calculateApprovalSolidityStorageSlot(ownerAddress, spenderAddress, cachedValue.slot)
return {
slot: ethers.BigNumber.from(cachedValue.slot).toHexString(),
slotHash: slotHash,
isVyper: false,
}
}
}

// Get the approval for the spender, that we can use to find the slot
let approval = await getErc20Approval(
provider,
Expand All @@ -124,50 +146,36 @@ export const getErc20ApprovalStorageSlot = async (

if (approval.gt(0)) {
for (let i = 0; i < maxSlots; i++) {
// Calculate the slot hash, using the owner address and the slot index
const slot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["address", "uint256"],
[ownerAddress, i]
)
);
// Calculate the storage slot, using the spender address and the slot hash
const storageSlot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["address", "bytes32"],
[spenderAddress, slot]
)
);
const { storageSlot, slotHash } = calculateApprovalSolidityStorageSlot(ownerAddress, spenderAddress, i)
// Get the value at the storage slot
const storageValue = await provider.getStorageAt(erc20Address, storageSlot);
// If the value at the storage slot is equal to the approval, return the slot as we have found the correct slot for approvals
if (ethers.BigNumber.from(storageValue).eq(approval)) {
approvalCache.set(erc20Address.toLowerCase(), {
slot: i,
isVyper: false,
ts: Date.now()
});
return {
slot: ethers.BigNumber.from(i).toHexString(),
slotHash: slot,
slotHash: slotHash,
isVyper: false,
};
}

// check via vyper storage layout, which uses keccak256(abi.encode(slot, address(this))) instead of keccak256(abi.encode(address(this), slot))
const vyperSlotHash = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["uint256", "address"],
[i, ownerAddress]
)
);

const vyperStorageSlot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["bytes32", "address"],
[vyperSlotHash, spenderAddress]
)
);
const { vyperStorageSlot, vyperSlotHash } = calculateApprovalVyperStorageSlot(ownerAddress, spenderAddress, i)
const vyperStorageValue = await provider.getStorageAt(
erc20Address,
vyperStorageSlot
);

if (ethers.BigNumber.from(vyperStorageValue).eq(approval)) {
approvalCache.set(erc20Address.toLowerCase(), {
slot: i,
isVyper: false,
ts: Date.now()
});

return {
slot: ethers.BigNumber.from(i).toHexString(),
slotHash: vyperSlotHash,
Expand All @@ -179,73 +187,93 @@ export const getErc20ApprovalStorageSlot = async (
throw new Error("Approval does not exist");
}


if (useFallbackSlot) {
// if useFallBackSlot = true, then we are just going to assume the slot is at the slot which is most common for erc20 tokens. for approvals, this is slot #10

const fallbackSlot = 10;
// check if contract is solidity/vyper, so we know which storage slot generation method to use
// TODO: add this above check, currently not sure of how to programatically check if a contract is a vyper contract.
const isVyper = false;
if (isVyper) {
const vyperSlotHash = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["uint256", "address"],
[fallbackSlot, ownerAddress]
)
);
// check solidity, then check vyper.
// (dont have an easy way to check if a contract is solidity/vyper)
const { storageSlot, slotHash } = calculateApprovalSolidityStorageSlot(ownerAddress, spenderAddress, fallbackSlot)
// Get the value at the storage slot
const storageValue = await provider.getStorageAt(erc20Address, storageSlot);
// If the value at the storage slot is equal to the approval, return the slot as we have found the correct slot for approvals
if (ethers.BigNumber.from(storageValue).eq(approval)) {
approvalCache.set(erc20Address.toLowerCase(), {
slot: fallbackSlot,
isVyper: false,
ts: Date.now()
});

const vyperStorageSlot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["bytes32", "address"],
[vyperSlotHash, spenderAddress]
)
);
const vyperStorageValue = await provider.getStorageAt(
erc20Address,
vyperStorageSlot
);
if (ethers.BigNumber.from(vyperStorageValue).eq(approval)) {
return {
slot: ethers.BigNumber.from(fallbackSlot).toHexString(),
slotHash: vyperSlotHash,
isVyper: true,
};
}
} else {

const slot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["address", "uint256"],
[ownerAddress, fallbackSlot]
)
);
// Calculate the storage slot, using the spender address and the slot hash
const storageSlot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["address", "bytes32"],
[spenderAddress, slot]
)
);
// Get the value at the storage slot
const storageValue = await provider.getStorageAt(erc20Address, storageSlot);
// If the value at the storage slot is equal to the approval, return the slot as we have found the correct slot for approvals
if (ethers.BigNumber.from(storageValue).eq(approval)) {
return {
slot: ethers.BigNumber.from(fallbackSlot).toHexString(),
slotHash: slot,
isVyper: false,
};
return {
slot: ethers.BigNumber.from(fallbackSlot).toHexString(),
slotHash: slotHash,
isVyper: false,
};
}

}
// check vyper
const { vyperStorageSlot, vyperSlotHash } = calculateApprovalVyperStorageSlot(ownerAddress, spenderAddress, fallbackSlot)
const vyperStorageValue = await provider.getStorageAt(
erc20Address,
vyperStorageSlot
);
if (ethers.BigNumber.from(vyperStorageValue).eq(approval)) {
approvalCache.set(erc20Address.toLowerCase(), {
slot: fallbackSlot,
isVyper: true,
ts: Date.now()
});

return {
slot: ethers.BigNumber.from(fallbackSlot).toHexString(),
slotHash: vyperSlotHash,
isVyper: true,
};
}

}

throw new Error("Unable to find approval slot");
};

// Generates approval solidity storage slot data
const calculateApprovalSolidityStorageSlot = (ownerAddress: string, spenderAddress: string, slotNumber: number) => {

// Calculate the slot hash, using the owner address and the slot index
const slotHash = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["address", "uint256"],
[ownerAddress, slotNumber]
)
);
// Calculate the storage slot, using the spender address and the slot hash
const storageSlot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["address", "bytes32"],
[spenderAddress, slotHash]
)
);
return { storageSlot, slotHash }
}

// Generates approval vyper storage slot data
const calculateApprovalVyperStorageSlot = (ownerAddress: string, spenderAddress: string, slotNumber: number) => {
// create via vyper storage layout, which uses keccak256(abi.encode(slot, address(this))) instead of keccak256(abi.encode(address(this), slot))
const vyperSlotHash = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["uint256", "address"],
[slotNumber, ownerAddress]
)
);

const vyperStorageSlot = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["bytes32", "address"],
[vyperSlotHash, spenderAddress]
)
);

return { vyperStorageSlot, vyperSlotHash }
}
/**
* Get the approval for a given ERC20 token
* @param provider - The JsonRpcProvider instance
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77 changes: 64 additions & 13 deletions src/balance.ts
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import { ethers } from "ethers";
import { balanceCache } from "./cache";

/**
* Generate mock data for a given ERC20 token balance
Expand Down Expand Up @@ -87,12 +88,37 @@ export const getErc20BalanceStorageSlot = async (
provider: ethers.providers.JsonRpcProvider,
erc20Address: string,
holderAddress: string,
maxSlots = 100
maxSlots = 30
): Promise<{
slot: string;
balance: ethers.BigNumber;
isVyper: boolean;
}> => {
// check the cache
const cachedValue = balanceCache.get(erc20Address.toLowerCase());
if (cachedValue) {
if (cachedValue.isVyper) {
const { vyperSlotHash } = calculateBalanceVyperStorageSlot(holderAddress, cachedValue.slot)
const vyperBalance = await provider.getStorageAt(
erc20Address,
vyperSlotHash
);
return {
slot: ethers.BigNumber.from(cachedValue.slot).toHexString(),
balance: ethers.BigNumber.from(vyperBalance),
isVyper: true,
};
} else {
const { slotHash } = calculateBalanceSolidityStorageSlot(holderAddress, cachedValue.slot);
const balance = await provider.getStorageAt(erc20Address, slotHash);
return {
slot: ethers.BigNumber.from(cachedValue.slot).toHexString(),
balance: ethers.BigNumber.from(balance),
isVyper: false,
}
}
}

// Get the balance of the holder, that we can use to find the slot
const userBalance = await getErc20Balance(
provider,
Expand All @@ -107,31 +133,36 @@ export const getErc20BalanceStorageSlot = async (
// For each slot, we compute the storage slot key [holderAddress, slot index] and get the value at that storage slot
// If the value at the storage slot is equal to the balance, return the slot as we have found the correct slot for balances
for (let i = 0; i < maxSlots; i++) {
const slot = ethers.utils.solidityKeccak256(
["uint256", "uint256"],
[holderAddress, i]
);
const balance = await provider.getStorageAt(erc20Address, slot);
const { slotHash } = calculateBalanceSolidityStorageSlot(holderAddress, i);
const balance = await provider.getStorageAt(erc20Address, slotHash);

if (ethers.BigNumber.from(balance).eq(userBalance)) {
balanceCache.set(erc20Address.toLowerCase(), {
slot: i,
isVyper: false,
ts: Date.now()
})

return {
slot: ethers.BigNumber.from(i).toHexString(),
balance: ethers.BigNumber.from(balance),
isVyper: false,
};
}

// check via vyper storage layout, which uses keccak256(abi.encode(slot, address(this))) instead of keccak256(abi.encode(address(this), slot))
const vyperSlotHash = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["uint256", "address"],
[i, holderAddress]
)
);
const { vyperSlotHash } = calculateBalanceVyperStorageSlot(holderAddress, i)
const vyperBalance = await provider.getStorageAt(
erc20Address,
vyperSlotHash
);

if (ethers.BigNumber.from(vyperBalance).eq(userBalance)) {
balanceCache.set(erc20Address.toLowerCase(), {
slot: i,
isVyper: true,
ts: Date.now()
})

return {
slot: ethers.BigNumber.from(i).toHexString(),
balance: ethers.BigNumber.from(vyperBalance),
Expand All @@ -142,6 +173,26 @@ export const getErc20BalanceStorageSlot = async (
throw new Error("Unable to find balance slot");
};


const calculateBalanceSolidityStorageSlot = (holderAddress: string, slotNumber: number) => {
const slotHash = ethers.utils.solidityKeccak256(
["uint256", "uint256"],
[holderAddress, slotNumber]
);
return { slotHash }
}

const calculateBalanceVyperStorageSlot = (holderAddress: string, slotNumber: number) => {
// create hash via vyper storage layout, which uses keccak256(abi.encode(slot, address(this))) instead of keccak256(abi.encode(address(this), slot))
const vyperSlotHash = ethers.utils.keccak256(
ethers.utils.defaultAbiCoder.encode(
["uint256", "address"],
[slotNumber, holderAddress]
)
);
return { vyperSlotHash }
}

/**
* Get the balance of a given address for a given ERC20 token
* @param provider - The JsonRpcProvider instance
Expand Down
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