client/keys: support export of unarmored private key

client/keys/export.go

@@ -2,23 +2,45 @@ package keys
 
 import (
 	"bufio"
+	"fmt"
 
 	"github.com/spf13/cobra"
 
 	"github.com/cosmos/cosmos-sdk/client"
 	"github.com/cosmos/cosmos-sdk/client/input"
+	"github.com/cosmos/cosmos-sdk/crypto/keyring"
+)
+
+const (
+	flagUnarmoredHex = "unarmored-hex"
+	flagUnsafe       = "unsafe"
 )
 
 // ExportKeyCommand exports private keys from the key store.
 func ExportKeyCommand() *cobra.Command {
-	return &cobra.Command{
+	cmd := &cobra.Command{
 		Use:   "export <name>",
 		Short: "Export private keys",
-		Long:  `Export a private key from the local keybase in ASCII-armored encrypted format.`,
-		Args:  cobra.ExactArgs(1),
+		Long: `Export a private key from the local keyring in ASCII-armored encrypted format.
+
+When both the --unarmored-hex and --unsafe flags are selected, cryptographic
+private key material is exported in an INSECURE fashion that is designed to
+allow users to import their keys in hot wallets. This feature is for advanced
+users only that are confident about how to handle private keys work and are
+FULLY AWARE OF THE RISKS. If you are unsure, you may want to do some research
+and export your keys in ASCII-armored encrypted format.`,
+		Args: cobra.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			buf := bufio.NewReader(cmd.InOrStdin())
 			clientCtx := client.GetClientContextFromCmd(cmd)
+			unarmored, _ := cmd.Flags().GetBool(flagUnarmoredHex)
+			unsafe, _ := cmd.Flags().GetBool(flagUnsafe)
+
+			if unarmored && unsafe {
+				return exportUnsafeUnarmored(cmd, args[0], buf, clientCtx.Keyring)
+			} else if unarmored || unsafe {
+				return fmt.Errorf("the flags %s and %s must be used together", flagUnsafe, flagUnarmoredHex)
+			}
 
 			encryptPassword, err := input.GetPassword("Enter passphrase to encrypt the exported key:", buf)
 			if err != nil {
@@ -31,7 +53,31 @@ func ExportKeyCommand() *cobra.Command {
 			}
 
 			cmd.Println(armored)
+
 			return nil
 		},
 	}
+
+	cmd.Flags().Bool(flagUnarmoredHex, false, "Export unarmored hex privkey. Requires --unsafe.")
+	cmd.Flags().Bool(flagUnsafe, false, "Enable unsafe operations. This flag must be switched on along with all unsafe operation-specific options.")
+
+	return cmd
+}
+
+func exportUnsafeUnarmored(cmd *cobra.Command, uid string, buf *bufio.Reader, kr keyring.Keyring) error {
+	// confirm deletion, unless -y is passed
+	if yes, err := input.GetConfirmation("WARNING: The private key will be exported as an unarmored hexadecimal string. USE AT YOUR OWN RISK. Continue?", buf, cmd.ErrOrStderr()); err != nil {
+		return err
+	} else if !yes {
+		return nil
+	}
+
+	hexPrivKey, err := keyring.NewUnsafe(kr).UnsafeExportPrivKeyHex(uid)
+	if err != nil {
+		return err
+	}
+
+	cmd.Println(hexPrivKey)
+
+	return nil
 }

client/keys/export_test.go

@@ -36,15 +36,34 @@ func Test_runExportCmd(t *testing.T) {
 	require.NoError(t, err)
 
 	// Now enter password
-	mockIn.Reset("123456789\n123456789\n")
-	cmd.SetArgs([]string{
+	args := []string{
 		"keyname1",
 		fmt.Sprintf("--%s=%s", flags.FlagHome, kbHome),
 		fmt.Sprintf("--%s=%s", flags.FlagKeyringBackend, keyring.BackendTest),
-	})
+	}
+
+	mockIn.Reset("123456789\n123456789\n")
+	cmd.SetArgs(args)
 
 	clientCtx := client.Context{}.WithKeyring(kb)
 	ctx := context.WithValue(context.Background(), client.ClientContextKey, &clientCtx)
 
 	require.NoError(t, cmd.ExecuteContext(ctx))
+
+	argsUnsafeOnly := append(args, "--unsafe")
+	cmd.SetArgs(argsUnsafeOnly)
+	require.Error(t, cmd.ExecuteContext(ctx))
+
+	argsUnarmoredHexOnly := append(args, "--unarmored-hex")
+	cmd.SetArgs(argsUnarmoredHexOnly)
+	require.Error(t, cmd.ExecuteContext(ctx))
+
+	argsUnsafeUnarmoredHex := append(args, "--unsafe", "--unarmored-hex")
+	cmd.SetArgs(argsUnsafeUnarmoredHex)
+	require.Error(t, cmd.ExecuteContext(ctx))
+
+	mockIn, mockOut := testutil.ApplyMockIO(cmd)
+	mockIn.Reset("y\n")
+	require.NoError(t, cmd.ExecuteContext(ctx))
+	require.Equal(t, "2485e33678db4175dc0ecef2d6e1fc493d4a0d7f7ce83324b6ed70afe77f3485\n", mockOut.String())
 }

crypto/keyring/keyring.go

@@ -88,6 +88,13 @@ type Keyring interface {
 	Exporter
 }
 
+// UnsafeKeyring exposes unsafe operations such as unsafe unarmored export in
+// addition to those that are made available by the Keyring interface.
+type UnsafeKeyring interface {
+	Keyring
+	UnsafeExporter
+}
+
 // Signer is implemented by key stores that want to provide signing capabilities.
 type Signer interface {
 	// Sign sign byte messages with a user key.
@@ -110,12 +117,20 @@ type Exporter interface {
 	// Export public key
 	ExportPubKeyArmor(uid string) (string, error)
 	ExportPubKeyArmorByAddress(address sdk.Address) (string, error)
+
 	// ExportPrivKey returns a private key in ASCII armored format.
 	// It returns an error if the key does not exist or a wrong encryption passphrase is supplied.
 	ExportPrivKeyArmor(uid, encryptPassphrase string) (armor string, err error)
 	ExportPrivKeyArmorByAddress(address sdk.Address, encryptPassphrase string) (armor string, err error)
 }
 
+// UnsafeExporter is implemented by key stores that support unsafe export
+// of private keys' material.
+type UnsafeExporter interface {
+	// UnsafeExportPrivKeyHex returns a private key in unarmored hex format
+	UnsafeExportPrivKeyHex(uid string) (string, error)
+}
+
 // Option overrides keyring configuration options.
 type Option func(options *Options)
 
@@ -774,6 +789,29 @@ func (ks keystore) writeMultisigKey(name string, pub types.PubKey) (Info, error)
 	return info, nil
 }
 
+type unsafeKeystore struct {
+	keystore
+}
+
+// NewUnsafe returns a new keyring that provides support for unsafe operations.
+func NewUnsafe(kr Keyring) UnsafeKeyring {
+	// The type assertion is against the only keystore
+	// implementation that is currently provided.
+	ks := kr.(keystore)
+
+	return unsafeKeystore{ks}
+}
+
+// UnsafeExportPrivKeyHex exports private keys in unarmored hexadecimal format.
+func (ks unsafeKeystore) UnsafeExportPrivKeyHex(uid string) (privkey string, err error) {
+	priv, err := ks.ExportPrivateKeyObject(uid)
+	if err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(priv.Bytes()), nil
+}
+
 func addrHexKeyAsString(address sdk.Address) string {
 	return fmt.Sprintf("%s.%s", hex.EncodeToString(address.Bytes()), addressSuffix)
 }

crypto/keyring/keyring_test.go

@@ -1,6 +1,7 @@
 package keyring
 
 import (
+	"encoding/hex"
 	"fmt"
 	"strings"
 	"testing"
@@ -1092,6 +1093,29 @@ func TestAltKeyring_ImportExportPubKey_ByAddress(t *testing.T) {
 	require.EqualError(t, err, fmt.Sprintf("cannot overwrite key: %s", newUID))
 }
 
+func TestAltKeyring_UnsafeExportPrivKeyHex(t *testing.T) {
+	keyring, err := New(t.Name(), BackendTest, t.TempDir(), nil)
+	require.NoError(t, err)
+
+	uid := theID
+
+	_, _, err = keyring.NewMnemonic(uid, English, sdk.FullFundraiserPath, hd.Secp256k1)
+	require.NoError(t, err)
+
+	unsafeKeyring := NewUnsafe(keyring)
+	privKey, err := unsafeKeyring.UnsafeExportPrivKeyHex(uid)
+
+	require.NoError(t, err)
+	require.Equal(t, 64, len(privKey))
+
+	_, err = hex.DecodeString(privKey)
+	require.NoError(t, err)
+
+	// test error on non existing key
+	_, err = unsafeKeyring.UnsafeExportPrivKeyHex("non-existing")
+	require.Error(t, err)
+}
+
 func TestAltKeyring_ConstructorSupportedAlgos(t *testing.T) {
 	keyring, err := New(t.Name(), BackendTest, t.TempDir(), nil)
 	require.NoError(t, err)