Add hs_ed25519_secret_key_parsing

5 files changed, 81 insertions, 0 deletions

diff --git a/pkg/okey/okey.go b/pkg/okey/okey.go
new file mode 100644
index 0000000..aba4f3e
--- /dev/null
+++ b/pkg/okey/okey.go
@@ -0,0 +1,29 @@
+// Package okey provides access to onion service private keys
+package okey
+
+import (
+	"crypto"
+	"fmt"
+	"os"
+
+	bed25519 "github.com/cretz/bine/torutil/ed25519"
+)
+
+// New parses the content of Tor's hs_ed25519_secret_key file by interpretting
+// bytes 32..96 as the 64-byte expanded seed.  For reference, see:
+// https://gitlab.torproject.org/tpo/core/tor/-/blob/main/src/feature/keymgt/loadkey.c#L379
+func New(b []byte) (crypto.Signer, error) {
+	if len(b) != 96 {
+		return nil, fmt.Errorf("invalid key file size: %d", len(b))
+	}
+	return bed25519.PrivateKey(b[32:96]), nil
+}
+
+// NewFromHSDir reads and parses the hs_ed25519_secret_key file in a given directory
+func NewFromHSDir(dir string) (crypto.Signer, error) {
+	b, err := os.ReadFile(dir + "/hs_ed25519_secret_key")
+	if err != nil {
+		return nil, err
+	}
+	return New(b)
+}
diff --git a/pkg/okey/okey_test.go b/pkg/okey/okey_test.go
new file mode 100644
index 0000000..2636bb4
--- /dev/null
+++ b/pkg/okey/okey_test.go
@@ -0,0 +1,51 @@
+package okey
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	bed25519 "github.com/cretz/bine/torutil/ed25519"
+)
+
+func TestNewFromHSDir(t *testing.T) {
+	if _, err := NewFromHSDir("no-such-directory"); err == nil {
+		t.Errorf("succeeded to read non-existing directory")
+	}
+
+	want := bed25519.PublicKey(hsPubFromFile(t, "testonly"))
+	if s, err := NewFromHSDir("testonly"); err != nil {
+		t.Errorf("failed reading valid directory: %v", err)
+	} else if got, ok := s.Public().(bed25519.PublicKey); !ok {
+		t.Errorf("wrong key type: %T", s.Public())
+	} else if !bytes.Equal(got, want) {
+		t.Errorf("got public key\n%x\nbut wanted\n%x", got, want)
+	}
+}
+
+func TestNew(t *testing.T) {
+	for _, table := range []struct {
+		desc string
+		priv []byte
+		want bed25519.PublicKey
+	}{
+		{"invalid: key size", make([]byte, 95), nil},
+	} {
+		_, err := New(table.priv)
+		if got, want := err != nil, table.desc != "valid"; got != want {
+			t.Errorf("%s: got error %v but wanted %v: %v", table.desc, got, want, err)
+		}
+	}
+}
+
+func hsPubFromFile(t *testing.T, dir string) []byte {
+	t.Helper()
+	b, err := os.ReadFile(dir + "/hs_ed25519_public_key")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(b) != 64 {
+		t.Fatalf("invalid public key file size: %d", len(b))
+	}
+	return b[32:64]
+}
diff --git a/pkg/okey/testonly/hostname b/pkg/okey/testonly/hostname
new file mode 100644
index 0000000..ed58ba6
--- /dev/null
+++ b/pkg/okey/testonly/hostname
@@ -0,0 +1 @@
+a3xo2fquvmhntjo663f4255bpskuuop4qru66xuzcmwfdl4fgiwt3uid.onion
diff --git a/pkg/okey/testonly/hs_ed25519_public_key b/pkg/okey/testonly/hs_ed25519_public_key
new file mode 100644
index 0000000..0a7493d
--- /dev/null
+++ b/pkg/okey/testonly/hs_ed25519_public_key
diff --git a/pkg/okey/testonly/hs_ed25519_secret_key b/pkg/okey/testonly/hs_ed25519_secret_key
new file mode 100644
index 0000000..9ba4008
--- /dev/null
+++ b/pkg/okey/testonly/hs_ed25519_secret_key