accounts, eth, clique, signer: support for external signer API (#18079)

* accounts, eth, clique: implement external backend + move sighash calc to backend

* signer: implement account_Version on external API

* accounts/external: enable ipc, add copyright

* accounts, internal, signer: formatting

* node: go fmt

* flags: disallow --dev in combo with --externalsigner

* accounts: remove clique-specific signing method, replace with more generic

* accounts, consensus: formatting + fix error in tests

* signer/core: remove (test-) import cycle

* clique: remove unused import

* accounts: remove CliqueHash and avoid dependency on package crypto

* consensus/clique: unduplicate header encoding

cmd/geth/main.go

@@ -62,6 +62,7 @@ var (
 		utils.BootnodesV5Flag,
 		utils.DataDirFlag,
 		utils.KeyStoreDirFlag,
+		utils.ExternalSignerFlag,
 		utils.NoUSBFlag,
 		utils.DashboardEnabledFlag,
 		utils.DashboardAddrFlag,
@@ -293,13 +294,14 @@ func startNode(ctx *cli.Context, stack *node.Node) {
 	utils.StartNode(stack)
 
 	// Unlock any account specifically requested
-	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
-
-	passwords := utils.MakePasswordList(ctx)
-	unlocks := strings.Split(ctx.GlobalString(utils.UnlockedAccountFlag.Name), ",")
-	for i, account := range unlocks {
-		if trimmed := strings.TrimSpace(account); trimmed != "" {
-			unlockAccount(ctx, ks, trimmed, i, passwords)
+	if keystores := stack.AccountManager().Backends(keystore.KeyStoreType); len(keystores) > 0 {
+		ks := keystores[0].(*keystore.KeyStore)
+		passwords := utils.MakePasswordList(ctx)
+		unlocks := strings.Split(ctx.GlobalString(utils.UnlockedAccountFlag.Name), ",")
+		for i, account := range unlocks {
+			if trimmed := strings.TrimSpace(account); trimmed != "" {
+				unlockAccount(ctx, ks, trimmed, i, passwords)
+			}
 		}
 	}
 	// Register wallet event handlers to open and auto-derive wallets

cmd/geth/usage.go

@@ -145,6 +145,7 @@ var AppHelpFlagGroups = []flagGroup{
 		Flags: []cli.Flag{
 			utils.UnlockedAccountFlag,
 			utils.PasswordFileFlag,
+			utils.ExternalSignerFlag,
 		},
 	},
 	{