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/message.go

@@ -0,0 +1,148 @@
+package main
+
+import (
+	"encoding/hex"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/ethereum/go-ethereum/accounts/keystore"
+	"github.com/ethereum/go-ethereum/cmd/utils"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"gopkg.in/urfave/cli.v1"
+)
+
+type outputSign struct {
+	Signature string
+}
+
+var commandSignMessage = cli.Command{
+	Name:      "signmessage",
+	Usage:     "sign a message",
+	ArgsUsage: "<keyfile> <message/file>",
+	Description: `
+Sign the message with a keyfile.
+It is possible to refer to a file containing the message.`,
+	Flags: []cli.Flag{
+		passphraseFlag,
+		jsonFlag,
+	},
+	Action: func(ctx *cli.Context) error {
+		keyfilepath := ctx.Args().First()
+		message := []byte(ctx.Args().Get(1))
+
+		// Load the keyfile.
+		keyjson, err := ioutil.ReadFile(keyfilepath)
+		if err != nil {
+			utils.Fatalf("Failed to read the keyfile at '%s': %v",
+				keyfilepath, err)
+		}
+
+		// Decrypt key with passphrase.
+		passphrase := getPassPhrase(ctx, false)
+		key, err := keystore.DecryptKey(keyjson, passphrase)
+		if err != nil {
+			utils.Fatalf("Error decrypting key: %v", err)
+		}
+
+		if len(message) == 0 {
+			utils.Fatalf("A message must be provided")
+		}
+		// Read message if file.
+		if _, err := os.Stat(string(message)); err == nil {
+			message, err = ioutil.ReadFile(string(message))
+			if err != nil {
+				utils.Fatalf("Failed to read the message file: %v", err)
+			}
+		}
+
+		signature, err := crypto.Sign(signHash(message), key.PrivateKey)
+		if err != nil {
+			utils.Fatalf("Failed to sign message: %v", err)
+		}
+
+		out := outputSign{
+			Signature: hex.EncodeToString(signature),
+		}
+		if ctx.Bool(jsonFlag.Name) {
+			mustPrintJSON(out)
+		} else {
+			fmt.Println("Signature: ", out.Signature)
+		}
+		return nil
+	},
+}
+
+type outputVerify struct {
+	Success            bool
+	RecoveredAddress   string
+	RecoveredPublicKey string
+}
+
+var commandVerifyMessage = cli.Command{
+	Name:      "verifymessage",
+	Usage:     "verify the signature of a signed message",
+	ArgsUsage: "<address> <signature> <message/file>",
+	Description: `
+Verify the signature of the message.
+It is possible to refer to a file containing the message.`,
+	Flags: []cli.Flag{
+		jsonFlag,
+	},
+	Action: func(ctx *cli.Context) error {
+		addressStr := ctx.Args().First()
+		signatureHex := ctx.Args().Get(1)
+		message := []byte(ctx.Args().Get(2))
+
+		// Determine whether it is a keyfile, public key or address.
+		if !common.IsHexAddress(addressStr) {
+			utils.Fatalf("Invalid address: %s", addressStr)
+		}
+		address := common.HexToAddress(addressStr)
+
+		signature, err := hex.DecodeString(signatureHex)
+		if err != nil {
+			utils.Fatalf("Signature encoding is not hexadecimal: %v", err)
+		}
+
+		if len(message) == 0 {
+			utils.Fatalf("A message must be provided")
+		}
+		// Read message if file.
+		if _, err := os.Stat(string(message)); err == nil {
+			message, err = ioutil.ReadFile(string(message))
+			if err != nil {
+				utils.Fatalf("Failed to read the message file: %v", err)
+			}
+		}
+
+		recoveredPubkey, err := crypto.SigToPub(signHash(message), signature)
+		if err != nil || recoveredPubkey == nil {
+			utils.Fatalf("Signature verification failed: %v", err)
+		}
+		recoveredPubkeyBytes := crypto.FromECDSAPub(recoveredPubkey)
+		recoveredAddress := crypto.PubkeyToAddress(*recoveredPubkey)
+
+		success := address == recoveredAddress
+
+		out := outputVerify{
+			Success:            success,
+			RecoveredPublicKey: hex.EncodeToString(recoveredPubkeyBytes),
+			RecoveredAddress:   strings.ToLower(recoveredAddress.Hex()),
+		}
+		if ctx.Bool(jsonFlag.Name) {
+			mustPrintJSON(out)
+		} else {
+			if out.Success {
+				fmt.Println("Signature verification successful!")
+			} else {
+				fmt.Println("Signature verification failed!")
+			}
+			fmt.Println("Recovered public key: ", out.RecoveredPublicKey)
+			fmt.Println("Recovered address: ", out.RecoveredAddress)
+		}
+		return nil
+	},
+}