feat: add age plugin support

Signed-off-by: Brian McGee <[email protected]>
Co-authored-by: Maximilian Bosch <[email protected]>

Author: brianmcgee

age/encrypted_keys.go

@@ -104,7 +104,7 @@ func (i *LazyScryptIdentity) Unwrap(stanzas []*age.Stanza) (fileKey []byte, err
 	return fileKey, err
 }
 
-func unwrapIdentities(key string, reader io.Reader) (ParsedIdentities, error){
+func unwrapIdentities(key string, reader io.Reader) (ParsedIdentities, error) {
 	b := bufio.NewReader(reader)
 	p, _ := b.Peek(14) // length of "age-encryption" and "-----BEGIN AGE"
 	peeked := string(p)
@@ -181,10 +181,10 @@ func unwrapIdentities(key string, reader io.Reader) (ParsedIdentities, error){
 		return ids, nil
 	// An unencrypted age identity file.
 	default:
-		ids, err := age.ParseIdentities(b)
+		ids, err := parseIdentities(b)
 		if err != nil {
 			return nil, fmt.Errorf("failed to parse '%s' age identities: %w", key, err)
 		}
 		return ids, nil
 	}
-}
+}

age/keysource.go

@@ -1,8 +1,10 @@
 package age
 
 import (
+	"bufio"
 	"bytes"
 	"errors"
+	"filippo.io/age/plugin"
 	"fmt"
 	"io"
 	"os"
@@ -115,7 +117,10 @@ type ParsedIdentities []age.Identity
 // parsing (using age.ParseIdentities) and appending to the slice yourself, in
 // combination with e.g. a sync.Mutex.
 func (i *ParsedIdentities) Import(identity ...string) error {
-	identities, err := parseIdentities(identity...)
+	// one identity per line
+	r := strings.NewReader(strings.Join(identity, "\n"))
+
+	identities, err := parseIdentities(r)
 	if err != nil {
 		return fmt.Errorf("failed to parse and add to age identities: %w", err)
 	}
@@ -339,6 +344,12 @@ func (key *MasterKey) loadIdentities() (ParsedIdentities, error) {
 // key or a public ssh key.
 func parseRecipient(recipient string) (age.Recipient, error) {
 	switch {
+	case strings.HasPrefix(recipient, "age1") && strings.Count(recipient, "1") > 1:
+		parsedRecipient, err := plugin.NewRecipient(recipient, PluginTerminalUI)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse input as age key from age plugin: %w", err)
+		}
+		return parsedRecipient, nil
 	case strings.HasPrefix(recipient, "age1"):
 		parsedRecipient, err := age.ParseX25519Recipient(recipient)
 		if err != nil {
@@ -357,17 +368,39 @@ func parseRecipient(recipient string) (age.Recipient, error) {
 	return nil, fmt.Errorf("failed to parse input, unknown recipient type: %q", recipient)
 }
 
-// parseIdentities attempts to parse the string set of encoded age identities.
-// A single identity argument is allowed to be a multiline string containing
-// multiple identities. Empty lines and lines starting with "#" are ignored.
-func parseIdentities(identity ...string) (ParsedIdentities, error) {
-	var identities []age.Identity
-	for _, i := range identity {
-		parsed, err := age.ParseIdentities(strings.NewReader(i))
+// parseIdentities attempts to parse one or more age identities from the provided reader.
+// One identity per line.
+// Empty lines and lines starting with "#" are ignored.
+func parseIdentities(r io.Reader) (ParsedIdentities, error) {
+	var identities ParsedIdentities
+
+	scanner := bufio.NewScanner(r)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		parsed, err := parseIdentity(line)
 		if err != nil {
 			return nil, err
 		}
-		identities = append(identities, parsed...)
+
+		identities = append(identities, parsed)
 	}
+
 	return identities, nil
 }
+
+func parseIdentity(s string) (age.Identity, error) {
+	switch {
+	case strings.HasPrefix(s, "AGE-PLUGIN-"):
+		return plugin.NewIdentity(s, PluginTerminalUI)
+	case strings.HasPrefix(s, "AGE-SECRET-KEY-1"):
+		return age.ParseX25519Identity(s)
+	default:
+		return nil, fmt.Errorf("unknown identity type")
+	}
+}

age/tui.go

@@ -1,5 +1,6 @@
 // These functions have been copied from the age project
 // https://github.com/FiloSottile/age/blob/v1.0.0/cmd/age/encrypted_keys.go
+// https://github.com/FiloSottile/age/blob/266c0940916da6bfa310fdd23156fbd70f9d90a0/tui/tui.go
 //
 // Copyright 2021 The age Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -11,7 +12,10 @@
 package age
 
 import (
+	"errors"
+	"filippo.io/age/plugin"
 	"fmt"
+	"io"
 	"os"
 	"runtime"
 	"testing"
@@ -67,3 +71,149 @@ func readPassphrase(prompt string) ([]byte, error) {
 	defer fmt.Fprintf(out, "\r\n")
 	return term.ReadPassword(int(in.Fd()))
 }
+
+func Printf(format string, v ...interface{}) {
+	log.Printf("age: "+format, v...)
+}
+
+func Warningf(format string, v ...interface{}) {
+	log.Printf("age: warning: "+format, v...)
+}
+
+// ClearLine clears the current line on the terminal, or opens a new line if
+// terminal escape codes don't work.
+func ClearLine(out io.Writer) {
+	const (
+		CUI = "\033["   // Control Sequence Introducer
+		CPL = CUI + "F" // Cursor Previous Line
+		EL  = CUI + "K" // Erase in Line
+	)
+
+	// First, open a new line, which is guaranteed to work everywhere. Then, try
+	// to erase the line above with escape codes.
+	//
+	// (We use CRLF instead of LF to work around an apparent bug in WSL2's
+	// handling of CONOUT$. Only when running a Windows binary from WSL2, the
+	// cursor would not go back to the start of the line with a simple LF.
+	// Honestly, it's impressive CONIN$ and CONOUT$ work at all inside WSL2.)
+	fmt.Fprintf(out, "\r\n"+CPL+EL)
+}
+
+// WithTerminal runs f with the terminal input and output files, if available.
+// WithTerminal does not open a non-terminal stdin, so the caller does not need
+// to check stdinInUse.
+func WithTerminal(f func(in, out *os.File) error) error {
+	if runtime.GOOS == "windows" {
+		in, err := os.OpenFile("CONIN$", os.O_RDWR, 0)
+		if err != nil {
+			return err
+		}
+		defer in.Close()
+		out, err := os.OpenFile("CONOUT$", os.O_WRONLY, 0)
+		if err != nil {
+			return err
+		}
+		defer out.Close()
+		return f(in, out)
+	} else if tty, err := os.OpenFile("/dev/tty", os.O_RDWR, 0); err == nil {
+		defer tty.Close()
+		return f(tty, tty)
+	} else if term.IsTerminal(int(os.Stdin.Fd())) {
+		return f(os.Stdin, os.Stdin)
+	} else {
+		return fmt.Errorf("standard input is not a terminal, and /dev/tty is not available: %v", err)
+	}
+}
+
+// ReadSecret reads a value from the terminal with no echo. The prompt is ephemeral.
+func ReadSecret(prompt string) (s []byte, err error) {
+	err = WithTerminal(func(in, out *os.File) error {
+		fmt.Fprintf(out, "%s ", prompt)
+		defer ClearLine(out)
+		s, err = term.ReadPassword(int(in.Fd()))
+		return err
+	})
+	return
+}
+
+// readCharacter reads a single character from the terminal with no echo. The
+// prompt is ephemeral.
+func readCharacter(prompt string) (c byte, err error) {
+	err = WithTerminal(func(in, out *os.File) error {
+		fmt.Fprintf(out, "%s ", prompt)
+		defer ClearLine(out)
+
+		oldState, err := term.MakeRaw(int(in.Fd()))
+		if err != nil {
+			return err
+		}
+		defer term.Restore(int(in.Fd()), oldState)
+
+		b := make([]byte, 1)
+		if _, err := in.Read(b); err != nil {
+			return err
+		}
+
+		c = b[0]
+		return nil
+	})
+	return
+}
+
+var PluginTerminalUI = &plugin.ClientUI{
+	DisplayMessage: func(name, message string) error {
+		Printf("%s plugin: %s", name, message)
+		return nil
+	},
+	RequestValue: func(name, message string, _ bool) (s string, err error) {
+		defer func() {
+			if err != nil {
+				Warningf("could not read value for age-plugin-%s: %v", name, err)
+			}
+		}()
+		secret, err := ReadSecret(message)
+		if err != nil {
+			return "", err
+		}
+		return string(secret), nil
+	},
+	Confirm: func(name, message, yes, no string) (choseYes bool, err error) {
+		defer func() {
+			if err != nil {
+				Warningf("could not read value for age-plugin-%s: %v", name, err)
+			}
+		}()
+		if no == "" {
+			message += fmt.Sprintf(" (press enter for %q)", yes)
+			_, err := ReadSecret(message)
+			if err != nil {
+				return false, err
+			}
+			return true, nil
+		}
+		message += fmt.Sprintf(" (press [1] for %q or [2] for %q)", yes, no)
+		for {
+			selection, err := readCharacter(message)
+			if err != nil {
+				return false, err
+			}
+			switch selection {
+			case '1':
+				return true, nil
+			case '2':
+				return false, nil
+			case '\x03': // CTRL-C
+				return false, errors.New("user cancelled prompt")
+			default:
+				Warningf("reading value for age-plugin-%s: invalid selection %q", name, selection)
+			}
+		}
+	},
+	WaitTimer: func(name string) {
+		Printf("waiting on %s plugin...", name)
+	},
+}
+
+type ReaderFunc func(p []byte) (n int, err error)
+
+func (f ReaderFunc) Read(p []byte) (n int, err error) { return f(p) }