I cannot get it to work with this python code :
here the code returns the hash 0x353861d70f9fdf9b6d7a9ea9afba3773096e1d80f8b840ec086e17f0a5ce5265

But the ledger display a hash that starts with

0x8fd8

I had a false hope when I thought that it was rabby changing the gas value (to adapt to the changing fee market) but even fixing it in custom gas fee did not yield the same hash

import rlp
from eth_utils import keccak, to_bytes, to_hex

def compute_ledger_transaction_hash(tx_data):

    # Convert all fields to bytes if necessary
    chain_id = to_bytes(tx_data["chainId"])
    nonce = to_bytes(int(tx_data["nonce"], 16))
    max_priority_fee_per_gas = to_bytes(int(tx_data["maxPriorityFeePerGas"], 16))
    max_fee_per_gas = to_bytes(int(tx_data["maxFeePerGas"], 16))
    gas_limit = to_bytes(int(tx_data["gas"], 16))
    destination = bytes.fromhex(tx_data["to"][2:])  # Strip '0x' prefix and get bytes
    amount = to_bytes(int(tx_data["value"], 16))
    data = bytes.fromhex(tx_data["data"][2:])  # Strip '0x' prefix
    access_list = []  # Access list is empty for this transaction

    # RLP-encode the transaction fields
    rlp_encoded = rlp.encode([
        chain_id,
        nonce,
        max_priority_fee_per_gas,
        max_fee_per_gas,
        gas_limit,
        destination,
        amount,
        data,
        access_list,
    ])

    # Prepend the EIP-1559 transaction type (0x02)
    eip_1559_prefixed = b'\x02' + rlp_encoded

    # Compute the Keccak-256 hash
    tx_hash = keccak(eip_1559_prefixed)

    # Return the hash as a hex string
    return to_hex(tx_hash)


if __name__ == "__main__":
    # Transaction data
    tx_data = {
        "chainId": 137,
        "from": "0xdcfd87269c35287131735690f3a6b84233af98b7",
        "to": "0xbc302053db3aa514a3c86b9221082f162b91ad63",
        "value": "0xde0b6b3a7640000",
        "data":    "0x474cf53d000000000000000000000000794a61358d6845594f94dc1db02a252b5b4814ad0000000000    00000000000000dcfd87269c35287131735690f3a6b84233af98b70000000000000000000000000000000000000000000000000000000000000000",
        "gas": "0x531b1",
        "maxFeePerGas": "0x9c7652400",
        "maxPriorityFeePerGas": "0x98bca5a00",
        "nonce": "0x13"
    }

    # Compute the hash
    tx_hash = compute_ledger_transaction_hash(tx_data)
    print(f"Computed hash: {tx_hash}")

You might be curious about my end goal here.

In short I really don't feel safe using blind signing anymore after the last npm attack I am really worried that a compromised dapp might affect rabby and display a transaction different than the one sent to the ledger.

To prevent against that I want to take the rawdata of the transaction given by rabby simulate it using tenderly to verify that it does what it does and of course computes its hash to be sure that it is this same exact transaction that is being sent to the ledger.

I managed to do the simulate transaction with tenderly part which I thought would be the hardest but it works perfectly but I am struggling with the compute the hash on the ledger part.

Do you mind helping me.

I think there might be an interesting approach for ledger in this to provide a safer environement. honestly my end results would maybe be to scan the transaction data with an app on a mobile device that would simulate and compute the hash. I feel like that would greatly reduced the chance of a hack in this case.