Monero: unsigned_monero_tx and submit_transfer using RPC

[zkaf]

I'm trying to generate unsigned_monero_tx in view-only wallet, sign it in full wallet, then go back to view-only one and submit the signed_monero_tx using RPC.
I'm wondering how to generate unsigned_monero_tx and signed_monero_tx, and whether or not there is an equivalent of GUI's "_submit_transfer_" using RPC.
I don't find it in the guide https://getmonero.org/resources/developer-guides/wallet-rpc.html.
It is my understanding that it could be done using "_sendrawtransaction_", but in that case, how can I obtain the signed tx_hex to be sent?
(the original tx_hex is generated using "transfer" in view-only wallet with "do_not_relay" and "get_tx_metadata" set as true, which, however, is without a valid signature, thus cannot be sent. I can get the signature using "sign" in the full wallet, but not the signed tx_hex)

Thank you very much for your time and help.

[johnconger]

I have been trying to accomplish exactly what you are describing for the past few weeks and I have come to the conclusion that this is not possible via RPC. You can only do this via the CLI. I am in the process of writing a RPC wrapper around the CLI so that I can make programmatic RPC calls that issue the proper CLI commands. A step-by-step guide around the CLI process can be found here: https://monero.stackexchange.com/questions/2160/how-do-i-use-cold-transaction-signing/ but you've probably seen this already. I am using this as a guide for the RPC wrapper.

[zkaf]

Thanks @johnconger for your answer and explanations. Yeah I have been trying all the ways I can think of, and searching online for solutions, only to find https://monero.stackexchange.com/questions/7239/is-there-a-way-to-make-unsigned-transaction-sign-and-submit-manually-using-wall unanswered.
(I see you also replied to that post which was not submitted by me)
CLI is pretty easy to understand and use, just RPC is not as friendly. I just don't get it if the command "sign" in RPC is not for unsigned_monero_tx, then how do we use it?

[zkaf]

Just figured out another way is to forget about the RPC of the view-only wallet (on hot PC). Simply make a transaction and output it's tx_blob from the cold (full) wallet, then copy it to hot PC and use monerod's "sendrawtransaction". The problem of this is you have to copy sync-ed blockchain from hot PC to cold PC everytime you make a transaction. Otherwise it's possible that you would get error messages like "not enough money" cuz the DB on your cold PC is not sync-ed.
One solution is to use export/import key images but I got an error message "Failed" (RPC's error messages are basically useless). Maybe I was not doing it correctly.
Another is to add an option "-f" to skip certain errors like "not enough money" (currently not permitted) and force to generate a transaction offline (of course such a tx would fail to be broadcast). I know Factom's wallet has that implemented in its factom-cli.

[zhongqiuwood]

@johnconger @zkaf
According to wallet2::sign_tx method, the command [sign_transfer] only produces file that is encrypted by secret_view_key.
However the command [sign_transfer export] produces both that is NOT encrypted and as well.

The RPC '/sendrawtransaction' seems asks for a raw transacation as the input, right?
So can you try RPC /sendrawtransaction + to make it happen?

[stoffu]

Yes, /sendrawtransaction accepts unencrypted tx blobs (which is why it’s called ‘raw’).

The support for cold signing with wallet RPC has been proposed a few weeks ago in #3780.

[zkaf]

@zhongqiuwood
Thanks for your reply. Just checked your solution; it seems to work. Didn't notice the export option of sign_transfer in v0.12.

[zhongqiuwood]

@stoffu. Thank you for your clarification!

The command [sign_transfer export] really confuses people.
Neither [-help] really helps. :(
I never know what the [sign_transfer export] does until read the code.
Can we enhance the usage and use [sign_transfer export_raw_tx] instead?

[stoffu]

3896

[moneromooo-monero]

The missing parts seem to be merged now.

+resolved