The One With OTP but fake

Chapter 1 : Real Eyes

😈

So the first step is to thoroughly examine the contract, just as you would explore your girl.

We Used 👇

byt3code decoder

💡

byt3code uses the eth_getCode method of the RPC API to fetch the ByteCode of the ContractAddress. It then decodes the bytecode into a readable format using https://library.dedaub.com. You can explore byt3code source code at our GH page 😇

Chapter 2 : Realize

We read whole contract from here and differentiate the functions.

List of Basic Functions :

name()

approve(address,uint256)

totalSupply()

transferFrom(address,address,uint256) & transfer(address,uint256)

decimals()

balanceOf(address)

renounceOwnership()

owner()

burn(uint256) & burnFrom(address,uint256)

increaseAllowance(address,uint256) & decreaseAllowance(address,uint256) & allowance(address,address)

transferOwnership(address) & renounceOwnership()

We notice 3 Abnormal Functions

0xb5095168

0xd760dc8b

0x3148f14f


function 0xb5095168() public payable { 
    return stor_9;
}

//  0xb5095168 is returning stor_9 value.


function 0x3148f14f(uint256 varg0, uint256 varg1, uint256 varg2) public payable { 
    require(4 + (msg.data.length - 4) - 4 >= 96);
    require(varg0 == varg0);
    require(varg1 == varg1);
    require(varg2 == varg2);
    MEM[MEM[64] + 96] = varg0;
    v0 = bigModExp(32, 32, v1, v1, varg1, varg2);
    require(v0);
    return MEM[MEM[192]];
}

// the function 0x3148f14f is returning the result stored in MEM[MEM[192]]


function 0xd760dc8b(uint256 varg0) public payable { 
    require(4 + (msg.data.length - 4) - 4 >= 32);
    require(varg0 == varg0);
    MEM[MEM[64] + 96] = stor_6;
    v0 = bigModExp(32, 32, v1, v1, stor_9, stor_8);
    require(v0);
    if (!(MEM[MEM[192]] - varg0)) {
        require(stor_7, Panic(18)); // division by zero
        stor_9 = keccak256(block.difficulty, block.timestamp) % stor_7;
        v2 = _SafeExp(10, uint8(18), uint256.max);
        require(!0x1 | (v2 == v2), Panic(17)); // arithmetic overflow or underflow
        require(msg.sender - address(0x0), Error('ERC20: mint to the zero address'));
        v3 = _SafeAdd(_totalSupply, v2);
        _totalSupply = v3;
        v4 = _SafeAdd(_balanceOf[msg.sender], v2);
        _balanceOf[msg.sender] = v4;
        emit Transfer(address(0x0), msg.sender, v2);
    }
}

// this function requires one uint256 valid OTP. it will mint one OTPF token. 
// we can see in function 0x3148f14f MEM[MEM[64] + 96] = varg0; and it is retrning  MEM[MEM[64] + 96] 
// so we have to generate otp by providing three values to function 0x3148f14f
// Namely : stor_6, stor_9, stor_8
// by looking at this function we can say stor_9 value is dynamic and changes after one time mint.

We can see below line from function 0x3148f14f.


v0 = bigModExp(32, 32, v1, v1, stor_9, stor_8);

😶

Now, we know varg1 and varg2 are stor_9and stor_8 in function 0x3148f14f

📢

By looking at code, Function 0xd760dc8b MEM[MEM[64] + 96] = stor_6 & Function 0x3148f14f MEM[MEM[64] + 96] = varg0 So by comparing both line we can say varg0 = stor_6

Chapter 3 : Real Lies

By looking at code, we can see


uint256 stor_6; // STORAGE[0x6]
uint256 stor_8; // STORAGE[0x8]
uint256 stor_9; // STORAGE[0x9]

Step 1 : Get stor_6, stor_9 and stor_8 value using eth_getStorageAt RPC Method.

Step 2: Call 0x3148f14f(stor_6, stor_9, stor_8) to generate OTP.

Step 3: Call 0xd760dc8b(OTP) to create Mint Transaction !

Step 1 : Getting Values


from web3 import Web3
from web3.middleware import construct_sign_and_send_raw_middleware
from eth_account import Account
RPC = "https://rpc.pulsechain.com"
TARGET = "0x3815D67214216EC3683652c6f1DA4fD99F677d0b"
w3 = Web3(Web3.HTTPProvider(RPC))
six = w3.eth.get_storage_at(TARGET, 0x6)
eight = w3.eth.get_storage_at(TARGET, 0x8)
nine = w3.eth.get_storage_at(TARGET, 0x9)
call_data = six.hex()[2:] + nine.hex()[2:] + eight.hex()[2:]

Note: [2:} removes ‘0x’ from starting of each result.

Step 2 : Getting OTP


# continuation for step 1.
call_data = six.hex()[2:] + nine.hex()[2:] + eight.hex()[2:]
otp = w3.eth.call({"value": 0, "to": TARGET, "data": "0x3148f14f" + call_data})

Step 3 : Creating Mint


private_key = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" # replace me
account = Account.from_key(private_key)
w3.middleware_onion.add(construct_sign_and_send_raw_middleware(account))
mint_call_data = "0xd760dc8b" + otp.hex()[2:]
txn = w3.eth.send_transaction({"from": account.address, "value": 0, "to": TARGET, "data": mint_call_data})
print(f"created transaction : txn.hex()")

Hope we atleast pointed you to right direction.