cmd/ethkey: new command line tool for keys (#15438)

ethkey is a new tool that serves as a command line interface to
the basic key management functionalities of geth. It currently
supports:
 
 - generating keyfiles
 - inspecting keyfiles (print public and private key)
 - signing messages
 - verifying signed messages

cmd/ethkey/utils.go

@@ -0,0 +1,83 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"strings"
+
+	"github.com/ethereum/go-ethereum/cmd/utils"
+	"github.com/ethereum/go-ethereum/console"
+	"github.com/ethereum/go-ethereum/crypto"
+	"gopkg.in/urfave/cli.v1"
+)
+
+// getPassPhrase obtains a passphrase given by the user.  It first checks the
+// --passphrase command line flag and ultimately prompts the user for a
+// passphrase.
+func getPassPhrase(ctx *cli.Context, confirmation bool) string {
+	// Look for the --passphrase flag.
+	passphraseFile := ctx.String(passphraseFlag.Name)
+	if passphraseFile != "" {
+		content, err := ioutil.ReadFile(passphraseFile)
+		if err != nil {
+			utils.Fatalf("Failed to read passphrase file '%s': %v",
+				passphraseFile, err)
+		}
+		return strings.TrimRight(string(content), "\r\n")
+	}
+
+	// Otherwise prompt the user for the passphrase.
+	passphrase, err := console.Stdin.PromptPassword("Passphrase: ")
+	if err != nil {
+		utils.Fatalf("Failed to read passphrase: %v", err)
+	}
+	if confirmation {
+		confirm, err := console.Stdin.PromptPassword("Repeat passphrase: ")
+		if err != nil {
+			utils.Fatalf("Failed to read passphrase confirmation: %v", err)
+		}
+		if passphrase != confirm {
+			utils.Fatalf("Passphrases do not match")
+		}
+	}
+	return passphrase
+}
+
+// signHash is a helper function that calculates a hash for the given message
+// that can be safely used to calculate a signature from.
+//
+// The hash is calulcated as
+//   keccak256("\x19Ethereum Signed Message:\n"${message length}${message}).
+//
+// This gives context to the signed message and prevents signing of transactions.
+func signHash(data []byte) []byte {
+	msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(data), data)
+	return crypto.Keccak256([]byte(msg))
+}
+
+// mustPrintJSON prints the JSON encoding of the given object and
+// exits the program with an error message when the marshaling fails.
+func mustPrintJSON(jsonObject interface{}) {
+	str, err := json.MarshalIndent(jsonObject, "", "  ")
+	if err != nil {
+		utils.Fatalf("Failed to marshal JSON object: %v", err)
+	}
+	fmt.Println(string(str))
+}