feat: melt from pipe and to STDOUT (#18)

* feat: melt from pipe

Signed-off-by: Carlos A Becker <caarlos0@gmail.com>

* Revert "feat: melt from pipe"

This reverts commit 20bef57.

* fix: better impl

Signed-off-by: Carlos A Becker <caarlos0@gmail.com>

* feat: backup from pipe

Signed-off-by: Carlos A Becker <caarlos0@gmail.com>

* feat: restore to stdout

Signed-off-by: Carlos A Becker <caarlos0@gmail.com>

* chore: lint

Signed-off-by: Carlos A Becker <caarlos0@gmail.com>

* chore: lint

Signed-off-by: Carlos A Becker <caarlos0@gmail.com>

cmd/melt/main.go

@@ -57,14 +57,19 @@ var (
 		Short: "Generate a seed phrase from an SSH key",
 		Long: `melt generates a seed phrase from an SSH key. That phrase can
 be used to rebuild your public and private keys.`,
-		Args:         cobra.ExactArgs(1),
+		Args:         cobra.MaximumNArgs(1),
 		SilenceUsage: true,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if err := setLanguage(language); err != nil {
 				return err
 			}
 
-			mnemonic, err := backup(args[0], nil)
+			var keyPath string
+			if len(args) > 0 {
+				keyPath = args[0]
+			}
+
+			mnemonic, err := backup(keyPath, nil)
 			if err != nil {
 				return err
 			}
@@ -120,13 +125,18 @@ be used to rebuild your public and private keys.`,
 				return err
 			}
 
-			if err := restore(maybeFile(mnemonic), args[0], askNewPassphrase); err != nil {
-				return err
-			}
+			switch args[0] {
+			case "-":
+				return restore(maybeFile(mnemonic), askNewPassphrase, restoreToWriter(cmd.OutOrStdout()))
+			default:
+				if err := restore(maybeFile(mnemonic), askNewPassphrase, restoreToFiles(args[0])); err != nil {
+					return err
+				}
 
-			pub := keyPathStyle.Render(args[0])
-			priv := keyPathStyle.Render(args[0] + ".pub")
-			fmt.Println(baseStyle.Render(fmt.Sprintf("\nSuccessfully restored keys to %s and %s", pub, priv)))
+				pub := keyPathStyle.Render(args[0])
+				priv := keyPathStyle.Render(args[0] + ".pub")
+				fmt.Println(baseStyle.Render(fmt.Sprintf("\nSuccessfully restored keys to %s and %s", pub, priv)))
+			}
 			return nil
 		},
 	}
@@ -166,19 +176,34 @@ func main() {
 }
 
 func maybeFile(s string) string {
-	if s == "-" {
-		bts, err := io.ReadAll(os.Stdin)
-		if err == nil {
-			return string(bts)
-		}
+	f, err := openFileOrStdin(s)
+	if err != nil {
+		return s
 	}
-	bts, err := os.ReadFile(s)
+	defer f.Close() //nolint:errcheck
+	bts, err := io.ReadAll(f)
 	if err != nil {
 		return s
 	}
 	return string(bts)
 }
 
+func openFileOrStdin(path string) (*os.File, error) {
+	if path == "-" {
+		return os.Stdin, nil
+	}
+
+	if fi, _ := os.Stdin.Stat(); (fi.Mode() & os.ModeNamedPipe) != 0 {
+		return os.Stdin, nil
+	}
+
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, fmt.Errorf("could not open %s: %w", path, err)
+	}
+	return f, nil
+}
+
 func parsePrivateKey(bts, pass []byte) (interface{}, error) {
 	if len(pass) == 0 {
 		// nolint: wrapcheck
@@ -189,7 +214,12 @@ func parsePrivateKey(bts, pass []byte) (interface{}, error) {
 }
 
 func backup(path string, pass []byte) (string, error) {
-	bts, err := os.ReadFile(path)
+	f, err := openFileOrStdin(path)
+	if err != nil {
+		return "", fmt.Errorf("could not read key: %w", err)
+	}
+	defer f.Close() //nolint:errcheck
+	bts, err := io.ReadAll(f)
 	if err != nil {
 		return "", fmt.Errorf("could not read key: %w", err)
 	}
@@ -224,7 +254,7 @@ func marshallPrivateKey(key ed25519.PrivateKey, pass []byte) (*pem.Block, error)
 	return sshmarshal.MarshalPrivateKeyWithPassphrase(key, "", pass)
 }
 
-func restore(mnemonic, path string, passFn func() ([]byte, error)) error {
+func restore(mnemonic string, passFn func() ([]byte, error), outFn func(pem, pub []byte) error) error {
 	pvtKey, err := melt.FromMnemonic(mnemonic)
 	if err != nil {
 		// nolint: wrapcheck
@@ -246,14 +276,29 @@ func restore(mnemonic, path string, passFn func() ([]byte, error)) error {
 		return fmt.Errorf("could not prepare public key: %w", err)
 	}
 
-	if err := os.WriteFile(path, pem.EncodeToMemory(block), 0o600); err != nil { // nolint: gomnd
-		return fmt.Errorf("failed to write private key: %w", err)
+	return outFn(pem.EncodeToMemory(block), ssh.MarshalAuthorizedKey(pubkey))
+}
+
+func restoreToWriter(w io.Writer) func(pem, _ []byte) error {
+	return func(pem, _ []byte) error {
+		if _, err := fmt.Fprint(w, string(pem)); err != nil {
+			return fmt.Errorf("could not write private key: %w", err)
+		}
+		return nil
 	}
+}
+
+func restoreToFiles(path string) func(pem, pub []byte) error {
+	return func(pem, pub []byte) error {
+		if err := os.WriteFile(path, pem, 0o600); err != nil { // nolint: gomnd
+			return fmt.Errorf("failed to write private key: %w", err)
+		}
 
-	if err := os.WriteFile(path+".pub", ssh.MarshalAuthorizedKey(pubkey), 0o600); err != nil { // nolint: gomnd
-		return fmt.Errorf("failed to write public key: %w", err)
+		if err := os.WriteFile(path+".pub", pub, 0o600); err != nil { // nolint: gomnd
+			return fmt.Errorf("failed to write public key: %w", err)
+		}
+		return nil
 	}
-	return nil
 }
 
 func getWidth(max int) int {

cmd/melt/main_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"crypto/sha256"
 	"encoding/hex"
 	"os"
@@ -68,7 +69,7 @@ func TestBackupRestoreKnownKey(t *testing.T) {
 	t.Run("restore", func(t *testing.T) {
 		is := is.New(t)
 		path := filepath.Join(t.TempDir(), "key")
-		is.NoErr(restore(expectedMnemonic, path, staticPass(nil)))
+		is.NoErr(restore(expectedMnemonic, staticPass(nil), restoreToFiles(path)))
 		is.Equal(expectedSum, sha256sum(t, path+".pub"))
 
 		bts, err := os.ReadFile(path)
@@ -80,11 +81,23 @@ func TestBackupRestoreKnownKey(t *testing.T) {
 		is.Equal(expectedFingerprint, ssh.FingerprintSHA256(k.PublicKey()))
 	})
 
+	t.Run("restore to writer", func(t *testing.T) {
+		is := is.New(t)
+
+		var b bytes.Buffer
+		is.NoErr(restore(expectedMnemonic, staticPass(nil), restoreToWriter(&b)))
+
+		k, err := ssh.ParsePrivateKey([]byte(b.String()))
+		is.NoErr(err)
+
+		is.Equal(expectedFingerprint, ssh.FingerprintSHA256(k.PublicKey()))
+	})
+
 	t.Run("restore key with password", func(t *testing.T) {
 		path := filepath.Join(t.TempDir(), "key")
 		is := is.New(t)
 		pass := staticPass([]byte("asd"))
-		is.NoErr(restore(expectedMnemonic, path, pass))
+		is.NoErr(restore(expectedMnemonic, pass, restoreToFiles(path)))
 
 		bts, err := os.ReadFile(path)
 		is.NoErr(err)
@@ -162,7 +175,7 @@ func TestBackupRestoreKnownKeyInJapanse(t *testing.T) {
 	t.Run("restore", func(t *testing.T) {
 		is := is.New(t)
 		path := filepath.Join(t.TempDir(), "key")
-		is.NoErr(restore(expectedMnemonic, path, staticPass(nil)))
+		is.NoErr(restore(expectedMnemonic, staticPass(nil), restoreToFiles(path)))
 		is.Equal(expectedSum, sha256sum(t, path+".pub"))
 
 		bts, err := os.ReadFile(path)