OKO TOKEN Honeypot

Reported loss $34K
Ethereum
Honeypot

What happened

OKO TOKEN (OKO) is an ERC-20 token deployed on Ethereum on 7 December 2020 at 0x03f3Acb1…67499c, with its 30,000-token supply minted to the deployer 0x279DE1d6…6672da. The source header advertises no minting and liquidity locked for 24 hours, but the contract has no lock, and the deployer can switch on a transfer filter through a function named ints. Once it is on, a transfer succeeds only if the deployer is a party or the sender is a chosen address, the Uniswap V2 router, or a whitelisted wallet, so ordinary holders cannot sell into the pool.

About 3 hours 20 minutes after deployment, the deployer removed the pool's liquidity in transaction 0x62cfe192…dd63a7, receiving about 158.12 ETH and 13,775 OKO. De.Fi's REKT database lists OKO as a honeypot with a $34,283 loss.

How it happened

  1. The constructor stores the owner argument in both _address0 and _address1 and mints the supply to it; the constructor arguments show this is the deployer 0x279DE1d6…6672da. While the two are equal, the transfer filter is off and the token trades normally.
  2. ints(address addressn) lets only _address0 set _address1 to any address. Once _address1 differs from _address0, the filter is on.
  3. Every transfer calls _ints. When neither sender nor recipient is _address0, it requires sender == _address1 || sender==_router || _Addressint[sender] and otherwise reverts with a misleading ERC20: transfer from the zero address message. A holder selling on Uniswap V2 is the sender of the transfer into the pair, so the sale reverts unless that holder is whitelisted. If _address1 is set to the pair, transfers out of the pair (buys) still pass.
  4. multiaddress lets _address0 send tokens to a list of wallets and add the first AllowN of them to _Addressint, exempting those wallets from the filter.
  5. In transaction 0x62cfe192…dd63a7 (block 11403320, 03:52:34 UTC) the deployer called removeLiquidityETHWithPermit on the Uniswap V2 router and received 158.12 ETH and 13,774.9998 OKO from the pair.

Protocol details

Classification Token
Protocol Type Exit Scam/Honeypot
Affected asset / contract OKO

Evidence

Same attack technique

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