Recover sender from signedTxHash

[bh2smith]

When working with the gas relayer, we receive a signed transaction hash that was signed by the "unknown" paymaster. In my case, this paymaster was not funded. I needed to extract the sender to fund the account. This utility method might be useful in the future.

Problems

Although this unit test demonstrates the viem implementation agrees with ethers. It doesn't agree with what someone else got (in CA Telegram). In fact, trying to relay this transaction with eth_sendRawTransaction resulted in an "INSUFFICIENT_FUNDS" error -- even after the public key of this was extracted.

Note that, from the

signedTxHash:
0x02f872611c847735940085174876e800825208940c0a71335cc50b821570f6f8b302b248d0e56ed4870eebe0b40e800080c080a0d490e3ce4e974cae1f89c4b328bf4dc7ecba7b1cef9838be6282ca92fd5a8127a01c032f8bfa93bd48fb5215813e4f3a21f8e5da015ebd52b4daa945bcc2d4749e

we recover

Incorrect Sender: 0x909BaB1A50EBd17c0E771b8B0BF2A95fEB34B205

While someone else got

Correct Sender: 0x993944ce7ed881a353b7e34f63a37242041629fb.

The "correctness" is concluded by the following observation: Funding the 0x909... account still resulted in INSUFFICIENT_FUNDS, while funding 0x993 resulted in a successful tx with:

txHash: 0x2da68d8765521fdbb331d2696cf51e4bab0ca37e21161350f7f03ec35eb8a540.

Unfortunately

1. This transaction is still not visible in the block explorer (after more than an hour).
2. Neither accounts funds have changed.
3. The very same node that the tx was sent to returns null when requesting eth_getTransactionReceipt, but says Already Exists when trying to resubmit the transaction.

Relevant RPC Requests

Send Signed Transaction

curl https://bsc-testnet.public.blastapi.io \
  -X POST \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_sendRawTransaction","params":["0x02f872611c847735940085174876e800825208940c0a71335cc50b821570f6f8b302b248d0e56ed4870eebe0b40e800080c080a0d490e3ce4e974cae1f89c4b328bf4dc7ecba7b1cef9838be6282ca92fd5a8127a01c032f8bfa93bd48fb5215813e4f3a21f8e5da015ebd52b4daa945bcc2d4749e"],"id":1}'

Get Transaction Receipt

curl https://bsc-testnet.public.blastapi.io \
  -X POST \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_getTransactionReceipt","params":["0x2da68d8765521fdbb331d2696cf51e4bab0ca37e21161350f7f03ec35eb8a540"],"id":1}'

According to this online tool:
https://rawtxdecode.in/ the sender is different.

and this rust implementation: https://github.com/near/multichain-gas-station-contract/blob/master/gas_station/tests/tests.rs#L515

[bh2smith]

No longer necessary since #23