Feature request: lighthouse account validator withdraw

[galets]

Objective

Validators of type 0x02 allow partial withdrawals. The only process of doing so is via launchpad, and it requires bringing online unnecessary assets (namely: metamask with access to private key of withdrawal address), which is a security issue.

There is already a Voluntary Exits (Full Withdrawals) feature implemented in lighthouse. I propose to implement alongside of it a feature that allows partial withdrawals

Proposed Interface

Use lighthouse account validator withdraw command to initiate partial withdrawal. Same parameters as lighthouse account validator exit with additional --amount flag to specify desired withdrawal amount in wei.

[michaelsproul]

The withdrawal address private key is not unnecessary. For an 0x02 validator, the withdrawal request must be signed by the withdrawal address key, not by the validator signing key that Lighthouse possesses.

For this reason I don't think this feature makes much sense inside Lighthouse. Doing a partial withdrawal is fundamentally about interacting with a contract on the execution layer, which requires code and keys that Lighthouse does not usually have access to. It wouldn't be impossible to add to Lighthouse, but IMO Lighthouse is not the most natural place for this kind of feature as it wouldn't benefit from any code reuse.

More info here: https://docs.ethstaker.org/upgrades/pectra-features/?h=#user-triggered-exit-and-withdrawals

I did a bit of digging for a CLI tool supporting partial withdrawals, but didn't find anything. Maybe you would be interested in contributing this feature to one of the toolkits like:

• ethdo: https://github.com/wealdtech/ethdo
• ethstaker-deposit-cli: https://github.com/ethstaker/ethstaker-deposit-cli