Safe Jail Honeypot

Reported loss Not disclosed
BNB Chain
Honeypot

What happened

Safe Jail (JAIL) is a BNB Chain token deployed on 5 April 2021 (UTC) at 0xc51c7950…2d1d72. Its internal _approve function stores the requested allowance only when the token owner is the hard-coded deployer address 0x96DA64B8…a7E66D; for every other holder it writes an allowance of zero. A PancakeSwap sale needs the router to move the holder's tokens with transferFrom, which subtracts the amount from that zero allowance and reverts, so ordinary holders cannot sell through the router while buys from the pair still work.

Unlike other copies of this template, the mint function is disabled by setting the amount to zero. De.Fi's REKT database lists JAIL as an exit scam/honeypot, stating that holders were restricted from selling their tokens.

How it happened

  1. The constructor mints the full supply of 500,000,000,000 JAIL (500000000000000 with 3 decimals) to the deployer, who also becomes the Ownable owner.
  2. When any holder calls approve or increaseAllowance, _approve checks owner == address(0x96DA64B8B3068445636087B1d8C7B051AEa7E66D); for everyone else it sets the allowance to 0 and emits Approval(owner, spender, 0). A comment above the check reads "What did you expect? It's a SafeJail after all!".
  3. A router sale calls transferFrom(holder, pair, amount). The function moves the tokens, then computes _allowances[sender][_msgSender()].sub(amount, ...) on a zero allowance, which reverts the whole transaction.
  4. Buys use the pair's plain transfer to the buyer, which has no allowance step, so purchases go through and the hard-coded deployer address can still approve the router and sell.
  5. The owner-only mint calls _mint, which sets amount = 0 before updating balances, so it cannot create new tokens.

Protocol details

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

Evidence

Same attack technique

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