2 files changed, 98 insertions, 0 deletions
diff --git a/pkg/onionkey/key.go b/pkg/onionkey/key.go
new file mode 100644
index 0000000..895edae
--- /dev/null
+++ b/pkg/onionkey/key.go
@@ -0,0 +1,22 @@
+package onionkey
+
+import (
+	"github.com/wybiral/torgo"
+)
+
+// Key is generic interface type for Tor onion keys.
+type Key interface {
+	WriteFile(path string) error
+	Onion() (*torgo.Onion, error)
+	ServiceID() string
+}
+
+// GenerateKey generates a Tor onion key.
+func GenerateKey() (Key, error) {
+	return generateV3()
+}
+
+// ReadFile reads a Tor onion key from file path.
+func ReadFile(path string) (Key, error) {
+	return readV3(path)
+}
diff --git a/pkg/onionkey/v3.go b/pkg/onionkey/v3.go
new file mode 100644
index 0000000..155c6b1
--- /dev/null
+++ b/pkg/onionkey/v3.go
@@ -0,0 +1,76 @@
+package onionkey
+
+import (
+	"crypto/rand"
+	"encoding/base32"
+	"encoding/base64"
+	"errors"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/wybiral/torgo"
+	"golang.org/x/crypto/ed25519"
+	"golang.org/x/crypto/sha3"
+)
+
+type v3Key ed25519.PrivateKey
+
+func generateV3() (v3Key, error) {
+	_, key, err := ed25519.GenerateKey(rand.Reader)
+	return v3Key(key), err
+}
+
+func readV3(path string) (v3Key, error) {
+	raw, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	pk := strings.TrimSpace(string(raw))
+	parts := strings.SplitN(pk, ":", 2)
+	if parts[0] != "v3" {
+		return nil, errors.New("Invalid key type")
+	}
+	seed, err := base64.StdEncoding.DecodeString(parts[1])
+	if err != nil {
+		return nil, err
+	}
+	key := ed25519.NewKeyFromSeed(seed)
+	return v3Key(key), nil
+}
+
+func (k v3Key) Onion() (*torgo.Onion, error) {
+	return torgo.OnionFromEd25519(ed25519.PrivateKey(k))
+}
+
+func (k v3Key) WriteFile(path string) error {
+	seed := ed25519.PrivateKey(k).Seed()
+	b64 := base64.StdEncoding.EncodeToString(seed)
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = f.WriteString("v3:" + b64)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (k v3Key) ServiceID() string {
+	// Get ed25519 public key
+	pub := ed25519.PrivateKey(k).Public().(ed25519.PublicKey)
+	// Calculate check digits
+	checkstr := []byte(".onion checksum")
+	checkstr = append(checkstr, pub...)
+	checkstr = append(checkstr, 0x03)
+	checksum := sha3.Sum256(checkstr)
+	checkdigits := checksum[:2]
+	// Calculate service ID
+	combined := pub[:]
+	combined = append(combined, checkdigits...)
+	combined = append(combined, 0x03)
+	serviceID := base32.StdEncoding.EncodeToString(combined)
+	return strings.ToLower(serviceID)
+}