How to verify Safe{Wallet} transactions on a hardware wallet

You are a Safe Wallet user.

You created your transaction via Safe{Wallet}.

You are about to hit “sign” and confirm on your hardware wallet.

This is a guide on how to perform a check of the transaction on your hardware wallet with a 3rd party command line tool.

For a basic guide on how to verify transaction data on e.g. Metamask or Rabby, refer to this guide.

If you can’t verify it, don’t sign it.

Step 1: Verify transaction data in Safe{Wallet}

Before you hit sign, from the Safe{Wallet} interface, get the following and verify that this is what you expect:

to - set to the recipient for Ether transfers, the ERC20 token contract for token transfers, or the smart contract to interact with for contract interactions.
value - usually 0 for contract interactions and > 0 for Ether transfers.
data (“Raw data”) - Use a call data decoder such as this one from Etherscan, this one from @rimeissner, or this one from @dethtools to actually check the entire call data.
call_type - Usually you should see a simple “call”. You should only see something else such as “create”, or “delegate_call” if you actually know what you are doing.
nonce - index of the next transaction you want to execute

Now you hit “sign” which sends the transaction data to your hardware wallet. (Depending on how you are connected, you first confirm via Rabby, Metamask, or the wallet you connected via WalletConnect.)

Step 2a: Verify hashed transaction data on hardware wallet

If your hardware wallet supports signing typed data via EIP712, skip to step 2b below.

Get the safe-tx-hashes-util command line tool made by @pcaversaccio.
- Note that it requires a few prerequisites to be installed on your computer.
- Also please familiarize yourself with the trust assumptions of the script.
Use the tool to fetch the transaction data from the Safe API and calculate
- Safe transaction hash
- Domain hash
- Message hash
Double check the fetched transaction data
- Multisig address - your Safe address
- Ensure that to, value, data, call_type match the respective parameters of step 1 above.
Double check the calculated hashes
- Ensure that the Safe transaction hash is exactly the same like safeTxHash from step 1 above.
- Verify Domain and Message hash on your hardware wallet.
ONLY when ALL of the above checks out, confirm on your hardware wallet.

In case the Safe API is currently unavailable, consider using one of the the following options to pass all transaction data manually instead of fetching them from the API:

Interactive mode of the safe-tx-hash-util tool above.
Offline mode of the safe-tx-hashes fork by Patrick Collins.

Step 2b: Verify typed data on hardware wallet

Some of the newer hardware wallets from Trezor, Ledger, GridPlus, and others display typed structured data via EIP712, or support some form of clear signing. In that case you can directly verify the transaction data on your hardware wallet:

to
- Does this match to from step 1?
- Is it set to an address you recognize?
value
- Does this match value from step 1?
- Is it 0 for contract interactions and the correct amount for Ether transfers?
data (“Raw data”)
- Does this match data from step 1?
operation
- Is this set to 0? This means a simple call
- 1 would mean delegatecall which is dangerous and you should check with a technical person.
nonce
- Does this match nonce from step 1?
- Is this the index of the next transaction you want to execute?
safeTxGas, baseGas
- Are both 0 for your Safe with version 1.3.0 or higher? Otherwise this can be higher.
baseGas, gasPrice
- Are both 0?
gasToken, refundReceiver
- Are both 0x0000000000000000000000000000000000000000?
ONLY when ALL of the above checks out, confirm on your wallet.

1 ledger.pdf

2 ledger.pdf

Why can't I transfer ETH from a contract into a Safe?

What is the Safe transaction hash (safeTxHash)?

Reject and Delete Transactions

Verify Safe creation

How to perform basic transactions checks on Safe{Wallet}