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I'm trying to replay transactions that exist in one chain on another.

I can replicate all transaction arguments that are available through eth_getTransactionByHash, but now need to sign the transaction. How do I extract the signing information from the committed transaction so that I'm able to resubmit with eth_sendRawTransaction.

Also welcome responses in web3.py, web3.js, ethers.js or any other preferred json-rpc SDK.

Existing code using web3.py that doesn't work:

tx = fallback_web3.eth.getTransaction(individual_tx_hash)
transaction = {
  "from": tx["from"],
  "to": tx["to"],
  "gas": tx["gas"],
  "gasPrice": tx["gasPrice"],
  "value": tx["value"],
  "nonce": tx["nonce"],
}
if "data" in tx:
  transaction["data"] = tx["data"]
w3.eth.sendTransaction(transaction)
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    Function eth_sendRawTransaction doesn't require you to pass the from value, as it is already embedded in the raw transaction itself (which you need to pass to this function).
    – goodvibration
    Commented Sep 8, 2020 at 10:55
  • @goodvibration exactly - and the question is how am I able to build up this raw transaction signature. I'm just using the RPC-API because it's most familiar across both JS/Python users.
    – Peteris
    Commented Sep 8, 2020 at 10:56
  • 1
    Just take the raw transaction as is.
    – goodvibration
    Commented Sep 8, 2020 at 11:00
  • 1
    Note that the signature of the transaction differs from one chain to another since the EIP-155 (eips.ethereum.org/EIPS/eip-155) to protect against replay attacks.
    – clement
    Commented Sep 8, 2020 at 11:07
  • 1
    You're right, if your two chains have the same chainId, then just sending the raw transaction should work.
    – clement
    Commented Sep 8, 2020 at 11:19

1 Answer 1

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There is an undocumented eth_getRawTransactionByHash method now in geth nodes.

Get raw transaction from hash

After getting the raw transaction, it can be directly replayed using eth_sendRawTransaction as long as all the parameters are the same according to EIP-155 (https://eips.ethereum.org/EIPS/eip-155) (nonce, gasprice, startgas, to, value, data, chainid, 0, 0).

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