cmd/lnwallet: add new wallet utility

[guggero]

In this PR we add a new command line utility program that allows us to inspect/dump a wallet.db file.

Without this tool, there is currently no way to dump the private keys generated by lnd or even find out how many on-chain addresses have been generated (which is important to know when restoring a wallet from a seed).

There are two sub-commands available:

• dumpwallet prints a bitcoind compatible dump wallet file to standard out (including all used addresses and their private keys).
  • Example: lnwallet --testnet dumpwallet --wallet_file example.db
  • Output:

# Wallet dump created by lnwallet 0.5.1-beta commit=v0.5.1-beta-253-g1838b64c6d0104a0e3eafd5607bfd368ced46de5-dirty
# * Created on 2018-12-25 17:30:57.063592003 +0000 UTC
# * Best block at time of backup was 395537 (00000000d6d7a72d0bb864ef8a76400944ab8a4dd7bd5618298ec4040e7e4160),
#   mined on 2042-07-14 01:04:00 +0000 UTC# * Total balance: 0.00000000

cNftcFWKK7XS9EYnC1rhwo9sG8gY1fSuFFYzEdPH72ArysSm8EMF 1970-01-01T00:00:01Z label= # addr=tb1q85u3d2ajetr5u9hslypelpz8y3c3nc87l3vptc
cVW9Qtximxk9fx5V53N4Bc4yt3R1HUVY3neLDTa6Uavg8xK3WtNu 1970-01-01T00:00:01Z label= # addr=tb1qfwfhfvrw6npxs6e82sdmwzj2dftyptqnlg07jl
...

• walletinfo prints the node's identity pubkey, the number of addresses used and, if requested, the BIP32 extended root key to standard out.
  • Example: lnwallet --testnet walletinfo --wallet_file example.db --with_root_key
  • Output:

Identity Pubkey: 0322...
Scope: m/49'/0'
  Number of internal (change) np2wkh addresses: 0
  Number of external np2wkh addresses: 0
Scope: m/84'/0'
  Number of internal (change) p2wkh addresses: 0
  Number of external p2wkh addresses: 166
Scope: m/1017'/1'
  Number of internal (change) p2wkh addresses: 0
  Number of external p2wkh addresses: 82
BIP32 extended root key: tprv8ZgxMBicQK...

[Sowiedu]

Can you extend it to also dump a mnemonic phrase?

[guggero]

That's not possible. The mnemonic phrase/seed is hashed to create the extended root key. The process cannot be reversed and only the BIP32 extended root key is stored in the wallet.db file.

[slush0]

@guggero Please add possibility to export also extended root key (xpriv). It is major piece of information for many tools for handling with wallets.

[guggero]

@slush0 That's what you do with --with_root_key:

...
BIP32 extended root key: tprv8ZgxMBicQK...

It just says tprv because the example is from testnet.

[Kukks]

You need to add COPY --from=builder /go/bin/lnwallet /bin/ to the Dockerfile

[guggero]

@Kukks you're right, thanks. At the time I probably thought that it wasn't really needed in the docker image but for consistency it's probably best to add it anyway.

[guggero]

Closing this in favor of https://github.com/guggero/chantools which now contains both functionalities of this PR (and more).