tools: Add `generatehsm` method to hsmtool to derivate BIP32 seeds from a
mnemonic using the BIP39 standard.
The new method uses libwally for the BIP39 to BIP32 derivation. It also
fails if an hsm_secret file already exists, so we do not overwrite
someone else's wallet without noticing.
It allows the use of passphrases, the ECHO mode in the terminal is
disable for higher security.
It currently supports "en", "es", "fr", "it", "jp", "zhs", "zht".
Changelog-Added: hsmtool: `hsm_secret` generation from a seed-phrase following BIP39.
This should be more robust in future: we SHA256 all of the deps.
For wiregen we prefix with EXPERIMENTAL_FEATURES, since it can effect them.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: We now install `lightning-hsmtool` for your `hsm_secret` needs.
See: https://github.com/ElementsProject/lightning/issues/3717#issuecomment-644844594
It seems reasonable to add this to the standard install, and to document it properly as well, hopefully we can fill in the documentation better later on.