Refuse weak passphrases without explicit flag.

README.md

@@ -125,6 +125,12 @@ If set, the `--debug` argument will output additional information about the oper
 
 Commands will have an exit status of 0 on success and 1 on failure.  The specific definition of success is specified in the help for each command.
 
+## Passphrase strength
+
+`ethdo` will by default not allow creation or export of accounts or wallets with weak passphrases.  If a weak pasphrase is used then `ethdo` will refuse to continue.
+
+If a weak passphrase is required, `ethdo` can be supplied with the `--allow-weak-passphrases` option which will force it to accept any passphrase, even if it is considered weak.
+
 ## Rules for account passphrases
 
 Account passphrases are used in various places in `ethdo`.  Where they are used, the following rules apply:

cmd/accountcreate.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
+	"github.com/wealdtech/ethdo/util"
 	e2wallet "github.com/wealdtech/go-eth2-wallet"
 	e2wtypes "github.com/wealdtech/go-eth2-wallet-types/v2"
 )
@@ -61,8 +62,12 @@ In quiet mode this will return 0 if the account is created successfully, otherwi
 			outputIf(debug, fmt.Sprintf("Distributed account has %d/%d threshold", viper.GetUint32("signing-threshold"), viper.GetUint32("participants")))
 			ctx, cancel := context.WithTimeout(context.Background(), viper.GetDuration("timeout"))
 			defer cancel()
+			if getOptionalPassphrase() != "" {
+				assert(util.AcceptablePassphrase(getPassphrase()), "supplied passphrase is weak; use a stronger one or run with the --allow-weak-passphrases flag")
+			}
 			account, err = distributedCreator.CreateDistributedAccount(ctx, accountName, viper.GetUint32("participants"), viper.GetUint32("signing-threshold"), []byte(getOptionalPassphrase()))
 		} else {
+			assert(util.AcceptablePassphrase(getPassphrase()), "supplied passphrase is weak; use a stronger one or run with the --allow-weak-passphrases flag")
 			if viper.GetString("path") != "" {
 				// Want a pathed account
 				creator, isCreator := wallet.(e2wtypes.WalletPathedAccountCreator)

cmd/accountimport.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
+	"github.com/wealdtech/ethdo/util"
 	"github.com/wealdtech/go-bytesutil"
 	e2wallet "github.com/wealdtech/go-eth2-wallet"
 	e2wtypes "github.com/wealdtech/go-eth2-wallet-types/v2"
@@ -38,8 +39,8 @@ In quiet mode this will return 0 if the account is imported successfully, otherw
 	Run: func(cmd *cobra.Command, args []string) {
 		assert(!remote, "account import not available with remote wallets")
 		assert(viper.GetString("account") != "", "--account is required")
-		passphrase := getPassphrase()
 		assert(accountImportKey != "", "--key is required")
+		assert(util.AcceptablePassphrase(getPassphrase()), "supplied passphrase is weak; use a stronger one or run with the --allow-weak-passphrases flag")
 
 		ctx, cancel := context.WithTimeout(context.Background(), viper.GetDuration("timeout"))
 		defer cancel()
@@ -64,7 +65,7 @@ In quiet mode this will return 0 if the account is imported successfully, otherw
 		_, accountName, err := e2wallet.WalletAndAccountNames(viper.GetString("account"))
 		errCheck(err, "Failed to obtain account name")
 
-		account, err := w.(e2wtypes.WalletAccountImporter).ImportAccount(ctx, accountName, key, []byte(passphrase))
+		account, err := w.(e2wtypes.WalletAccountImporter).ImportAccount(ctx, accountName, key, []byte(getPassphrase()))
 		errCheck(err, "Failed to create account")
 
 		pubKey, err := bestPublicKey(account)

cmd/passphrases.go

@@ -13,7 +13,9 @@
 
 package cmd
 
-import "github.com/spf13/viper"
+import (
+	"github.com/spf13/viper"
+)
 
 // getStorePassphrases() fetches the store passphrase supplied by the user.
 func getStorePassphrase() string {

cmd/root.go

@@ -206,6 +206,10 @@ func init() {
 	if err := viper.BindPFlag("server-ca-cert", RootCmd.PersistentFlags().Lookup("server-ca-cert")); err != nil {
 		panic(err)
 	}
+	RootCmd.PersistentFlags().Bool("allow-weak-passphrases", false, "allow passphrases that use common words, are short, or generally considered weak")
+	if err := viper.BindPFlag("allow-weak-passphrases", RootCmd.PersistentFlags().Lookup("allow-weak-passphrases")); err != nil {
+		panic(err)
+	}
 }
 
 // initConfig reads in config file and ENV variables if set.

cmd/walletcreate.go

@@ -24,6 +24,7 @@ import (
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 	bip39 "github.com/tyler-smith/go-bip39"
+	"github.com/wealdtech/ethdo/util"
 	distributed "github.com/wealdtech/go-eth2-wallet-distributed"
 	keystorev4 "github.com/wealdtech/go-eth2-wallet-encryptor-keystorev4"
 	hd "github.com/wealdtech/go-eth2-wallet-hd/v2"
@@ -58,6 +59,7 @@ In quiet mode this will return 0 if the wallet is created successfully, otherwis
 				os.Exit(_exitFailure)
 			}
 			assert(getWalletPassphrase() != "", "--walletpassphrase is required for hierarchical deterministic wallets")
+			assert(util.AcceptablePassphrase(getWalletPassphrase()), "supplied passphrase is weak; use a stronger one or run with the --allow-weak-passphrases flag")
 			err = walletCreateHD(ctx, viper.GetString("wallet"), getWalletPassphrase(), viper.GetString("mnemonic"))
 		case "distributed":
 			assert(viper.GetString("mnemonic") == "", "--mnemonic is not allowed with distributed wallets")

cmd/walletexport.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
+	"github.com/wealdtech/ethdo/util"
 	types "github.com/wealdtech/go-eth2-wallet-types/v2"
 )
 
@@ -40,6 +41,7 @@ In quiet mode this will return 0 if the wallet is able to be exported, otherwise
 		assert(viper.GetString("remote") == "", "wallet export not available with remote wallets")
 		assert(viper.GetString("wallet") != "", "--wallet is required")
 		assert(walletExportPassphrase != "", "--exportpassphrase is required")
+		assert(util.AcceptablePassphrase(walletExportPassphrase), "supplied passphrase is weak; use a stronger one or run with the --allow-weak-passphrases flag")
 
 		wallet, err := walletFromPath(ctx, viper.GetString("wallet"))
 		errCheck(err, "Failed to access wallet")

go.mod

@@ -12,6 +12,7 @@ require (
 	github.com/magiconair/properties v1.8.4 // indirect
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/mitchellh/mapstructure v1.3.3 // indirect
+	github.com/nbutton23/zxcvbn-go v0.0.0-20180912185939-ae427f1e4c1d
 	github.com/pelletier/go-toml v1.8.1 // indirect
 	github.com/pkg/errors v0.9.1
 	github.com/prysmaticlabs/ethereumapis v0.0.0-20201003171600-a72e5f77d233
@@ -24,6 +25,7 @@ require (
 	github.com/spf13/jwalterweatherman v1.1.0 // indirect
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.7.1
+	github.com/stretchr/testify v1.6.1
 	github.com/tyler-smith/go-bip39 v1.0.2
 	github.com/wealdtech/eth2-signer-api v1.6.0
 	github.com/wealdtech/go-bytesutil v1.1.1

go.sum

@@ -241,6 +241,8 @@ github.com/mitchellh/mapstructure v1.3.3/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RR
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
+github.com/nbutton23/zxcvbn-go v0.0.0-20180912185939-ae427f1e4c1d h1:AREM5mwr4u1ORQBMvzfzBgpsctsbQikCVpvC+tX285E=
+github.com/nbutton23/zxcvbn-go v0.0.0-20180912185939-ae427f1e4c1d/go.mod h1:o96djdrsSGy3AWPyBgZMAGfxZNfgntdJG+11KU4QvbU=
 github.com/oklog/ulid v1.3.1/go.mod h1:CirwcVhetQ6Lv90oh/F+FBtV6XMibvdAFo93nm5qn4U=
 github.com/pascaldekloe/goe v0.0.0-20180627143212-57f6aae5913c/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=

util/passphrase.go

@@ -0,0 +1,31 @@
+// Copyright © 2020 Weald Technology Trading
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	zxcvbn "github.com/nbutton23/zxcvbn-go"
+	"github.com/spf13/viper"
+)
+
+// minPassphraseScore is the minimum acceptable passphrase score.
+const minPassphraseScore = 2
+
+// AcceptablePassphrase returns true if the passphrase is acceptable.
+func AcceptablePassphrase(passphrase string) bool {
+	if viper.GetBool("allow-weak-passphrases") {
+		return true
+	}
+	res := zxcvbn.PasswordStrength(passphrase, nil)
+	return res.Score >= minPassphraseScore
+}

util/passphrase_test.go

@@ -0,0 +1,60 @@
+// Copyright © 2020 Weald Technology Trading
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util_test
+
+import (
+	"testing"
+
+	"github.com/spf13/viper"
+	"github.com/stretchr/testify/require"
+	"github.com/wealdtech/ethdo/util"
+)
+
+func TestAcceptablePassphrase(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		allowWeak bool
+		expected  bool
+	}{
+		{
+			name:     "Empty",
+			input:    ``,
+			expected: false,
+		},
+		{
+			name:     "Simple",
+			input:    `password`,
+			expected: false,
+		},
+		{
+			name:      "AllowedWeak",
+			input:     `password`,
+			allowWeak: true,
+			expected:  true,
+		},
+		{
+			name:     "Complex",
+			input:    `Hu[J"yKH{z&-;[]'7T*Dm1:t`,
+			expected: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			viper.Set("allow-weak-passphrases", test.allowWeak)
+			require.Equal(t, test.expected, util.AcceptablePassphrase(test.input))
+		})
+	}
+}