signmessage: add signmessage cmd

README.md

@@ -429,6 +429,7 @@ Available Commands:
   rescuefunding       Rescue funds locked in a funding multisig output that never resulted in a proper channel; this is the command the initiator of the channel needs to run
   rescuetweakedkey    Attempt to rescue funds locked in an address with a key that was affected by a specific bug in lnd
   showrootkey         Extract and show the BIP32 HD root key from the 24 word lnd aezeed
+  signmessage         Sign a message with the nodes identity pubkey.
   signrescuefunding   Rescue funds locked in a funding multisig output that never resulted in a proper channel; this is the command the remote node (the non-initiator) of the channel needs to run
   summary             Compile a summary about the current state of channels
   sweeptimelock       Sweep the force-closed state after the time lock has expired
@@ -488,6 +489,7 @@ Legend:
 | [rescueclosed](doc/chantools_rescueclosed.md)               | :pencil: (:pushpin:) Rescue funds in a legacy (pre `STATIC_REMOTE_KEY`) channel output                                                   |
 | [rescuefunding](doc/chantools_rescuefunding.md)             | :pencil: (:pushpin:) Rescue funds from a funding transaction. Deprecated, use [zombierecovery](doc/chantools_zombierecovery.md) instead  |
 | [showrootkey](doc/chantools_showrootkey.md)                 | :pencil: Display the master root key (`xprv`) from your seed (DO NOT SHARE WITH ANYONE)                                                  |
+| [signmessage](doc/chantools_signmessage.md)                 | :pencil: Sign a message with the nodes identity pubkey.                                                                                  |
 | [signrescuefunding](doc/chantools_signrescuefunding.md)     | :pencil: (:pushpin:) Sign to funds from a funding transaction. Deprecated, use [zombierecovery](doc/chantools_zombierecovery.md) instead |
 | [summary](doc/chantools_summary.md)                         | Create a summary of channel funds from a `channel.db` file                                                                               |
 | [sweepremoteclosed](doc/chantools_sweepremoteclosed.md)     | :pencil: Find channel funds from remotely force closed channels and sweep them                                                           |

cmd/chantools/root.go

@@ -123,6 +123,7 @@ func main() {
 		newRescueFundingCommand(),
 		newRescueTweakedKeyCommand(),
 		newShowRootKeyCommand(),
+		newSignMessageCommand(),
 		newSignRescueFundingCommand(),
 		newSummaryCommand(),
 		newSweepTimeLockCommand(),

cmd/chantools/signmessage.go

@@ -0,0 +1,90 @@
+package main
+
+import (
+	"fmt"
+
+	chantools_lnd "github.com/lightninglabs/chantools/lnd"
+	"github.com/lightningnetwork/lnd/keychain"
+	"github.com/spf13/cobra"
+	"github.com/tv42/zbase32"
+)
+
+var (
+	signedMsgPrefix = []byte("Lightning Signed Message:")
+)
+
+type signMessageCommand struct {
+	Msg string
+
+	rootKey *rootKey
+	cmd     *cobra.Command
+}
+
+func newSignMessageCommand() *cobra.Command {
+	cc := &signMessageCommand{}
+	cc.cmd = &cobra.Command{
+		Use:   "signmessage",
+		Short: "Sign a message with the node's private key.",
+		Long: `Sign msg with the resident node's private key.
+		Returns the signature as a zbase32 string.`,
+		Example: `chantools signmessage --msg=foobar`,
+		RunE:    cc.Execute,
+	}
+	cc.cmd.Flags().StringVar(
+		&cc.Msg, "msg", "", "the message to sign",
+	)
+
+	cc.rootKey = newRootKey(cc.cmd, "decrypting the backup")
+
+	return cc.cmd
+}
+
+func (c *signMessageCommand) Execute(_ *cobra.Command, _ []string) error {
+	if c.Msg == "" {
+		return fmt.Errorf("please enter a valid msg")
+	}
+
+	extendedKey, err := c.rootKey.read()
+	if err != nil {
+		return fmt.Errorf("error reading root key: %w", err)
+	}
+
+	signer := &chantools_lnd.Signer{
+		ExtendedKey: extendedKey,
+		ChainParams: chainParams,
+	}
+
+	// Create the key locator for the node key.
+	keyLocator := keychain.KeyLocator{
+		Family: keychain.KeyFamilyNodeKey,
+		Index:  0,
+	}
+
+	// Fetch the private key for node key.
+	privKey, err := signer.FetchPrivKey(&keychain.KeyDescriptor{
+		KeyLocator: keyLocator,
+	})
+	if err != nil {
+		return err
+	}
+
+	// Create a new signer.
+	privKeyMsgSigner := keychain.NewPrivKeyMessageSigner(
+		privKey, keyLocator,
+	)
+
+	// Prepend the special lnd prefix.
+	// See: https://github.com/lightningnetwork/lnd/blob/63e698ec4990e678089533561fd95cfd684b67db/rpcserver.go#L1576 .
+	msg := []byte(c.Msg)
+	msg = append(signedMsgPrefix, msg...)
+	sigBytes, err := privKeyMsgSigner.SignMessageCompact(msg, true)
+	if err != nil {
+		return err
+	}
+
+	// Encode the signature.
+	sig := zbase32.EncodeToString(sigBytes)
+	fmt.Println(sig)
+
+	return nil
+}

doc/chantools_signmessage.md

@@ -0,0 +1,26 @@
+## chantools signmessage
+
+Signs a message with the nodes key, results in the same signature as
+`lncli signmessage`
+
+### Synopsis
+
+```
+chantools signmessage [flags]
+```
+
+### Examples
+
+```
+chantools signmessage --msg=foobar
+```
+
+### Options
+
+```
+      --bip39            read a classic BIP39 seed and passphrase from the terminal instead of asking for lnd seed format or providing the --rootkey flag
+  -h, --help             help for signmessage
+      --msg string       the message to sign
+      --rootkey string   BIP32 HD root key of the wallet to use for decrypting the backup; leave empty to prompt for lnd 24 word aezeed
+      --single_hash      single hash the msg instead of double hash (lnd default is false)
+```

go.mod

@@ -126,6 +126,7 @@ require (
 	github.com/stretchr/objx v0.5.0 // indirect
 	github.com/syndtr/goleveldb v1.0.1-0.20210819022825-2ae1ddf74ef7 // indirect
 	github.com/tmc/grpc-websocket-proxy v0.0.0-20201229170055-e5319fda7802 // indirect
+	github.com/tv42/zbase32 v0.0.0-20220222190657-f76a9fc892fa // indirect
 	github.com/ulikunitz/xz v0.5.11 // indirect
 	github.com/xi2/xz v0.0.0-20171230120015-48954b6210f8 // indirect
 	github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2 // indirect

go.sum

@@ -686,6 +686,8 @@ github.com/syndtr/goleveldb v1.0.1-0.20210819022825-2ae1ddf74ef7/go.mod h1:q4W45
 github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20201229170055-e5319fda7802 h1:uruHq4dN7GR16kFc5fp3d1RIYzJW5onx8Ybykw2YQFA=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20201229170055-e5319fda7802/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
+github.com/tv42/zbase32 v0.0.0-20220222190657-f76a9fc892fa h1:2EwhXkNkeMjX9iFYGWLPQLPhw9O58BhnYgtYKeqybcY=
+github.com/tv42/zbase32 v0.0.0-20220222190657-f76a9fc892fa/go.mod h1:is48sjgBanWcA5CQrPBu9Y5yABY/T2awj/zI65bq704=
 github.com/ugorji/go v1.1.7 h1:/68gy2h+1mWMrwZFeD1kQialdSzAb432dtpeJ42ovdo=
 github.com/ugorji/go v1.1.7/go.mod h1:kZn38zHttfInRq0xu/PH0az30d+z6vm202qpg1oXVMw=
 github.com/ugorji/go/codec v1.1.7 h1:2SvQaVZ1ouYrrKKwoSk2pzd4A9evlKJb9oTL+OaLUSs=