derivekey: add new --identity flag for lnd identity_pubkey

cmd/chantools/derivekey.go

@@ -21,8 +21,9 @@ Extended private key (xprv):	%s
 `
 
 type deriveKeyCommand struct {
-	Path   string
-	Neuter bool
+	Path     string
+	Neuter   bool
+	Identity bool
 
 	rootKey *rootKey
 	cmd     *cobra.Command
@@ -36,7 +37,9 @@ func newDeriveKeyCommand() *cobra.Command {
 		Long: `This command derives a single key with the given BIP32
 derivation path from the root key and prints it to the console.`,
 		Example: `chantools derivekey --path "m/1017'/0'/5'/0/0'" \
-	--neuter`,
+	--neuter
+
+chantools derivekey --identity`,
 		RunE: cc.Execute,
 	}
 	cc.cmd.Flags().StringVar(
@@ -47,6 +50,10 @@ derivation path from the root key and prints it to the console.`,
 		&cc.Neuter, "neuter", false, "don't output private key(s), "+
 			"only public key(s)",
 	)
+	cc.cmd.Flags().BoolVar(
+		&cc.Identity, "identity", false, "derive the lnd "+
+			"identity_pubkey",
+	)
 
 	cc.rootKey = newRootKey(cc.cmd, "decrypting the backup")
 
@@ -59,6 +66,11 @@ func (c *deriveKeyCommand) Execute(_ *cobra.Command, _ []string) error {
 		return fmt.Errorf("error reading root key: %v", err)
 	}
 
+	if c.Identity {
+		c.Path = lnd.IdentityPath(chainParams)
+		c.Neuter = true
+	}
+
 	return deriveKey(extendedKey, c.Path, c.Neuter)
 }
 

doc/chantools_derivekey.md

@@ -15,7 +15,9 @@ chantools derivekey [flags]
 
 ```
 chantools derivekey --path "m/1017'/0'/5'/0/0'" \
-	--neuter
+    --neuter
+
+chantools derivekey --identity
 ```
 
 ### Options
@@ -23,6 +25,7 @@ chantools derivekey --path "m/1017'/0'/5'/0/0'" \
 ```
       --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 derivekey
+      --identity         derive the lnd identity_pubkey
       --neuter           don't output private key(s), only public key(s)
       --path string      BIP32 derivation path to derive; must start with "m/"
       --rootkey string   BIP32 HD root key of the wallet to use for decrypting the backup; leave empty to prompt for lnd 24 word aezeed

lnd/hdkeychain.go

@@ -133,6 +133,13 @@ func ShaChainFromPath(extendedKey *hdkeychain.ExtendedKey,
 	return shachain.NewRevocationProducer(*revRoot), nil
 }
 
+func IdentityPath(params *chaincfg.Params) string {
+	return fmt.Sprintf(
+		LndDerivationPath+"/0/0", params.HDCoinType,
+		keychain.KeyFamilyNodeKey,
+	)
+}
+
 func AllDerivationPaths(params *chaincfg.Params) ([]string, [][]uint32, error) {
 	mkPath := func(f keychain.KeyFamily) string {
 		return fmt.Sprintf(