Improve token detection

[medvedev1088]

Below are existing issues with detecting ERC20/ERC721 tokens:

1. Contracts where function 4byte hashes are not in init block: ex. 0x6b175474e89094c44da98b954eedeac495271d0f (Likely due to LibNote).
   • https://etherscan.io/address/0x7d1afa7b718fb893db30a3abc0cfc608aacfebb0#code
2. Contracts where one of methods is not implemented. ex. 0xaa7427d8f17d87a28f5e1ba3adbb270badbe1011 doesn't implement approve() method.
3. Proxy contracts, ex. 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 (proxy contract checker https://etherscan.io/proxyContractChecker?a=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48)

How does Etherscan detect ERC20's?

1. Allows users to manually mark contract as token if you can prove you're owner.
2. Uses their own heuristics to detect tokens (can call name(), symbol(), decimals(), totalSupply(), balance(), has emitted Transfer() events).

[alexon1234]

Hey again,

I saw that we have an error for the token https://etherscan.io/address/0xd1e5b0ff1287aa9f9a268759062e4ab08b9dacbe On the BigQuery we have it mark as not an ERC721, but in reality it is

[
  {
    "address": "0xd1e5b0ff1287aa9f9a268759062e4ab08b9dacbe",
    "bytecode": "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    "function_sighashes": [],
    "is_erc20": false,
    "is_erc721": false,
    "block_timestamp": "2019-12-10 08:54:12 UTC",
    "block_number": "9082251",
    "block_hash": "0x583cbe0424bd7cf19ccf920b6617ae121b1b34181fc7e27903c8331417d12527"
  }
]

The code for checking if is an ERC20 or an ERC721 is using the function_sighashes field, but in this case is empty

def is_erc721_contract(self, function_sighashes):
        c = ContractWrapper(function_sighashes)
        return c.implements('balanceOf(address)') and \
               c.implements('ownerOf(uint256)') and \
               c.implements_any_of('transfer(address,uint256)', 'transferFrom(address,address,uint256)') and \
               c.implements('approve(address,uint256)')

Seems we have 27985829 contracts without function_sighashes field

SELECT COUNT(*)
FROM `bigquery-public-data.crypto_ethereum.contracts` 
WHERE ARRAY_LENGTH(function_sighashes) = 0

I was thinking if maybe we could improve the detection rate by searching in the bytecode for the ERC721 methods, but I don't know if it will be robust enough

• bytes4(keccak256('balanceOf(address)')) == 0x70a08231
• bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e
• bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3
• bytes4(keccak256('getApproved(uint256)')) == 0x081812fc
• bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
• bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c
• bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
• bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e
• bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde

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Also, I maybe we could look for events like the following to improve the detection rate

• Transfer(address indexed, address indexed, uint256) (for ERC-20)
• Transfer(address indexed, address indexed, uint256 indexed) (for ERC-721)

Thanks for all :D

[sourdzl]

hey any updates on this? am happy to take a look in a few weeks, but wondering if there have been other approaches discussed elsewhere

[leechenghan]

I'm encountering problems with the is_erc721_contract function as well, outlined in this issue. This contract is ERC721 but for some reason, the function sighashes returned from parsing the bytecode are different from the sighashes of the ERC721 functions.

contract function sighashes from bytecode
['0x70a08231', '0xa035b1fe', '0xd26ea6c0', '0xe985e9c5', '0xeb8d2444', '0xf2fde38b']
is erc721 False

implements balanceOf(address) True
implements ownerOf(uint256) False
implements transfer(address,uint256) or transferFrom(address,address,uint256) False
implements approve(address,uint256) False

sighash of balanceOf(address) 0x70a08231
sighash of ownerOf(uint256) 0x6352211e
sighash of transfer(address,uint256) 0xa9059cbb
sighash of transferFrom(address,address,uint256) 0x23b872dd
sighash of approve(address,uint256) 0x095ea7b3

I also noticed that if I simply search for the function signatures in the bytecode, I can actually find them.