Merge pull request #137 from ubclaunchpad/133-secure-private-key-storage

133 secure private key storage

app/console.go

@@ -72,6 +72,13 @@ func RunConsole(a *App) *ishell.Shell {
 			editUser(ctx, a)
 		},
 	})
+	shell.AddCmd(&ishell.Cmd{
+		Name: "cryptowallet",
+		Help: "enable or disable password protection for private key storage",
+		Func: func(ctx *ishell.Context) {
+			cryptoWallet(ctx, a)
+		},
+	})
 
 	// Set interrupt handler
 	shell.Interrupt(func(ctx *ishell.Context, count int, input string) {
@@ -83,6 +90,96 @@ func RunConsole(a *App) *ishell.Shell {
 	return shell
 }
 
+func encryptUser(ctx *ishell.Context, app *App, password string) error {
+	err := app.CurrentUser.EncryptPrivateKey(password)
+	if err != nil {
+		return err
+	}
+
+	if err := app.CurrentUser.Save(userFileName); err != nil {
+		app.CurrentUser.DecryptPrivateKey(password)
+		ctx.Print(err)
+		return err
+	}
+
+	return nil
+}
+
+func decryptUser(ctx *ishell.Context, app *App, password string) error {
+	err := app.CurrentUser.DecryptPrivateKey(password)
+	if err != nil {
+		return err
+	}
+
+	if err := app.CurrentUser.Save(userFileName); err != nil {
+		app.CurrentUser.EncryptPrivateKey(password)
+		ctx.Print(err)
+		return err
+	}
+
+	return nil
+}
+
+func cryptoWallet(ctx *ishell.Context, app *App) {
+	if len(ctx.Args) < 1 {
+		ctx.Println("\nUsage: cryptowallet [command]")
+		ctx.Println("\nCOMMANDS:")
+		ctx.Println("\t enable \t Enable cryptowallet")
+		ctx.Println("\t disable \t Disable cryptowallet")
+		return
+	}
+
+	switch ctx.Args[0] {
+	case "enable":
+		if app.CurrentUser.CryptoWallet {
+			ctx.Print("CryptoWallet is already enabled")
+		} else {
+			ctx.Print("Please enter password: ")
+			password := ctx.ReadPassword()
+			err := encryptUser(ctx, app, password)
+			if err != nil {
+				ctx.Print("Unable to decrypt private key")
+			} else {
+				ctx.Print("Successfully enabled cryptowallet")
+			}
+		}
+	case "disable":
+		if !app.CurrentUser.CryptoWallet {
+			ctx.Print("CryptoWallet is already disabled")
+			return
+		}
+		ctx.Print("Please enter password: ")
+		password := ctx.ReadPassword()
+		err := decryptUser(ctx, app, password)
+
+		// Invalid password, try again
+		if InvalidPassword(err) {
+			ctx.Print("Inavalid password, please try again: ")
+			password = ctx.ReadPassword()
+			err = decryptUser(ctx, app, password)
+		}
+		if err != nil {
+			ctx.Println("Unable to decrypt private key")
+			return
+		}
+		ctx.Print("Successfully disabled cryptowallet")
+		return
+	case "status":
+		var s string
+		if app.CurrentUser.CryptoWallet {
+			s = "enabled"
+		} else {
+			s = "disabled"
+		}
+		ctx.Printf("cryptowallet status: %s", s)
+	default:
+		ctx.Println("\nUsage: cryptowallet [command]")
+		ctx.Println("\nCOMMANDS:")
+		ctx.Println("\t enable \t Enable cryptowallet")
+		ctx.Println("\t disable \t Disable cryptowallet")
+	}
+}
+
 func send(ctx *ishell.Context, app *App) {
 	if len(ctx.Args) < 2 {
 		ctx.Println("Usage: send [amount] [public address]")
@@ -100,9 +197,39 @@ func send(ctx *ishell.Context, app *App) {
 	amount *= float64(blockchain.CoinValue)
 	addr := ctx.Args[1]
 
+	cryptoWallet := false
+	password := ""
+	if app.CurrentUser.CryptoWallet {
+		ctx.Print("Please enter cryptowallet password: ")
+		password = ctx.ReadPassword()
+		err = app.CurrentUser.DecryptPrivateKey(password)
+
+		// Invalid password, try again
+		if InvalidPassword(err) {
+			ctx.Print("Inavalid password, please try again: ")
+			password = ctx.ReadPassword()
+			err = app.CurrentUser.DecryptPrivateKey(password)
+		}
+		if err != nil {
+			ctx.Println("Cannot proceed with transaction, unable to decrypt private key")
+			return
+		}
+		cryptoWallet = true
+	}
+
 	// Try to make a payment.
 	ctx.Println("Sending amount", coinValue(uint64(amount)), "to", addr)
 	err = app.Pay(addr, uint64(amount))
+
+	// Re-enable crypto wallet
+	if cryptoWallet {
+		err := app.CurrentUser.EncryptPrivateKey(password)
+		if err != nil {
+			ctx.Println("Error re-encrypting private key locally")
+			panic(err)
+		}
+	}
+
 	if err != nil {
 		emoji.Println(":disappointed: ", err)
 	} else {

app/console_test.go

@@ -14,6 +14,7 @@ func TestRunConsoleHasCommands(t *testing.T) {
 		"address",
 		"clear",
 		"connect",
+		"cryptowallet",
 		"exit",
 		"help",
 		"miner",

app/crypto.go

@@ -0,0 +1,99 @@
+package app
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha512"
+	"strings"
+
+	"golang.org/x/crypto/pbkdf2"
+)
+
+/*
+https://golang.org/src/crypto/cipher/example_test.go
+*/
+
+const (
+	nonceSize = 12
+	saltSize  = 16
+)
+
+// Encrypt encrypts cipherText with a given password
+func Encrypt(plainText []byte, password string) ([]byte, error) {
+
+	passwordBytes := []byte(password)
+
+	salt := make([]byte, saltSize)
+	_, err := rand.Read(salt)
+	if err != nil {
+		return nil, err
+	}
+
+	key := pbkdf2.Key(passwordBytes, salt, 4096, 32, sha512.New)
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	aesgcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, nonceSize)
+	_, err = rand.Read(nonce)
+	if err != nil {
+		return nil, err
+	}
+
+	cipherText := aesgcm.Seal(nil, nonce, plainText, nil)
+	cipherText = append(cipherText, salt...)
+	cipherText = append(cipherText, nonce...)
+
+	return cipherText, nil
+}
+
+// Decrypt decrypts cipherText with a given password
+func Decrypt(cipherText []byte, password string) ([]byte, error) {
+
+	passwordBytes := []byte(password)
+
+	ctLen := len(cipherText)
+	nonce := cipherText[ctLen-nonceSize:]
+	salt := cipherText[ctLen-nonceSize-saltSize : ctLen-nonceSize]
+
+	key := pbkdf2.Key(passwordBytes, salt, 4096, 32, sha512.New)
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	aesgcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	plainText, err := aesgcm.Open(
+		nil,
+		nonce,
+		cipherText[:ctLen-saltSize-nonceSize],
+		nil,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return plainText, nil
+}
+
+// InvalidPassword is returned from Decrypt if an invalid password is used to
+// decrypt the ciphertext
+func InvalidPassword(err error) bool {
+	if err == nil {
+		return false
+	}
+	return strings.Compare(err.Error(), "cipher: message authentication failed") == 0
+}

app/crypto_test.go

@@ -0,0 +1,29 @@
+package app_test
+
+import (
+	"testing"
+
+	"github.com/ubclaunchpad/cumulus/app"
+)
+
+func TestInvalidPassword(t *testing.T) {
+	plainText := "Hello, world!"
+	plainTextBytes := []byte(plainText)
+
+	cipherText, _ := app.Encrypt(plainTextBytes, "correctPassword")
+	plainTextNew, err := app.Decrypt(cipherText, "incorrectPassword")
+
+	if !app.InvalidPassword(err) {
+		t.Fail()
+	}
+
+	if plainTextNew != nil {
+		t.Fail()
+	}
+
+	plainTextNew, err = app.Decrypt(cipherText, "correctPassword")
+
+	if string(plainTextNew[:]) != plainText {
+		t.Fail()
+	}
+}

app/user.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"math/big"
 	"os"
 
 	crand "crypto/rand"
@@ -16,17 +17,19 @@ import (
 
 // User holds basic user information.
 type User struct {
-	Wallet    *blockchain.Wallet
-	Name      string
-	BlockSize uint32
+	Wallet       *blockchain.Wallet
+	Name         string
+	BlockSize    uint32
+	CryptoWallet bool
 }
 
 // NewUser creates a new user
 func NewUser() *User {
 	return &User{
-		Wallet:    blockchain.NewWallet(),
-		BlockSize: blockchain.DefaultBlockSize,
-		Name:      "Default User",
+		Wallet:       blockchain.NewWallet(),
+		BlockSize:    blockchain.DefaultBlockSize,
+		Name:         "Default User",
+		CryptoWallet: false,
 	}
 }
 
@@ -35,10 +38,44 @@ func (u *User) Public() blockchain.Address {
 	return u.Wallet.Public()
 }
 
+// EncryptPrivateKey encrypts the user's private key
+func (u *User) EncryptPrivateKey(password string) error {
+	if !u.CryptoWallet {
+		pk := u.Wallet.PrivateKey.D.Bytes()
+		pk, err := Encrypt(pk, password)
+		if err != nil {
+			return err
+		}
+
+		u.Wallet.PrivateKey.D = new(big.Int).SetBytes(pk)
+		u.CryptoWallet = true
+	}
+	return nil
+}
+
+// DecryptPrivateKey decrypts the user's private key
+func (u *User) DecryptPrivateKey(password string) error {
+	if u.CryptoWallet {
+		pk := u.Wallet.PrivateKey.D.Bytes()
+		pk, err := Decrypt(pk, password)
+		if err != nil {
+			return err
+		}
+
+		u.Wallet.PrivateKey.D = new(big.Int).SetBytes(pk)
+		u.CryptoWallet = false
+	}
+	return nil
+}
+
 // Save writes the user to a file of the given name in the current working
 // directory in JSON format. It returns an error if one occurred, or a pointer
 // to the file that was written to on success.
 func (u *User) Save(fileName string) error {
+	if _, err := os.Stat(fileName); !os.IsNotExist(err) {
+		os.Remove(fileName)
+	}
+
 	userFile, err := os.OpenFile(fileName, os.O_WRONLY|os.O_CREATE, 0644)
 	if err != nil {
 		return err
@@ -74,6 +111,7 @@ func LoadUser(fileName string) (*User, error) {
 	if err := dec.Decode(&u); err != nil {
 		return nil, err
 	}
+
 	return &u, nil
 }
 

app/user_test.go

@@ -24,3 +24,23 @@ func TestSaveAndLoad(t *testing.T) {
 	assert.Equal(t, user1, user2)
 	assert.Nil(t, os.Remove("userTestFile.json"))
 }
+
+func TestSave(t *testing.T) {
+	user1 := NewUser()
+
+	assert.Nil(t, user1.Save("userTestFile.json"))
+	user2, err := LoadUser("userTestFile.json")
+	assert.Nil(t, err)
+
+	assert.Nil(t, user1.EncryptPrivateKey("password"))
+	assert.Nil(t, user1.Save("userTestFile.json"))
+
+	assert.Nil(t, user1.DecryptPrivateKey("password"))
+	assert.Nil(t, user1.Save("userTestFile.json"))
+
+	user1, err = LoadUser("userTestFile.json")
+	assert.Nil(t, err)
+
+	assert.Equal(t, user1, user2)
+	assert.Nil(t, os.Remove("userTestFile.json"))
+}