feat: signed expiring console session tokens

server/internal/services/console.go

@@ -0,0 +1,69 @@
+package services
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func sessionHMACKey() ([]byte, error) {
+	// Reuse the AES key material as the HMAC secret. Distinct domain via prefix.
+	k, err := encryptionKey()
+	if err != nil {
+		return nil, err
+	}
+	mac := hmac.New(sha256.New, k)
+	mac.Write([]byte("vantage-console-session-v1"))
+	return mac.Sum(nil), nil
+}
+
+func b64(b []byte) string  { return base64.RawURLEncoding.EncodeToString(b) }
+
+// SignSessionToken returns a signed, expiring token binding a session id.
+func SignSessionToken(sessionID string, ttl time.Duration) (string, error) {
+	key, err := sessionHMACKey()
+	if err != nil {
+		return "", err
+	}
+	exp := time.Now().Add(ttl).Unix()
+	payload := fmt.Sprintf("%s.%d", b64([]byte(sessionID)), exp)
+	mac := hmac.New(sha256.New, key)
+	mac.Write([]byte(payload))
+	return payload + "." + b64(mac.Sum(nil)), nil
+}
+
+// VerifySessionToken checks signature + expiry and returns the session id.
+func VerifySessionToken(token string) (string, error) {
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return "", fmt.Errorf("malformed token")
+	}
+	payload := parts[0] + "." + parts[1]
+	key, err := sessionHMACKey()
+	if err != nil {
+		return "", err
+	}
+	mac := hmac.New(sha256.New, key)
+	mac.Write([]byte(payload))
+	want := mac.Sum(nil)
+	got, err := base64.RawURLEncoding.DecodeString(parts[2])
+	if err != nil || !hmac.Equal(want, got) {
+		return "", fmt.Errorf("invalid signature")
+	}
+	exp, err := strconv.ParseInt(parts[1], 10, 64)
+	if err != nil {
+		return "", fmt.Errorf("invalid expiry")
+	}
+	if time.Now().Unix() > exp {
+		return "", fmt.Errorf("token expired")
+	}
+	sid, err := base64.RawURLEncoding.DecodeString(parts[0])
+	if err != nil {
+		return "", fmt.Errorf("invalid session id")
+	}
+	return string(sid), nil
+}

server/internal/services/console_test.go

@@ -0,0 +1,43 @@
+package services
+
+import (
+	"testing"
+	"time"
+)
+
+func TestSessionTokenRoundTrip(t *testing.T) {
+	t.Setenv("KEY_ENCRYPTION_KEY", "00112233445566778899aabbccddeeff00112233445566778899aabbccddeeff")
+
+	tok, err := SignSessionToken("sess-123", time.Minute)
+	if err != nil {
+		t.Fatalf("sign: %v", err)
+	}
+	got, err := VerifySessionToken(tok)
+	if err != nil {
+		t.Fatalf("verify: %v", err)
+	}
+	if got != "sess-123" {
+		t.Fatalf("got %q want sess-123", got)
+	}
+}
+
+func TestSessionTokenExpired(t *testing.T) {
+	t.Setenv("KEY_ENCRYPTION_KEY", "00112233445566778899aabbccddeeff00112233445566778899aabbccddeeff")
+
+	tok, err := SignSessionToken("sess-123", -time.Second)
+	if err != nil {
+		t.Fatalf("sign: %v", err)
+	}
+	if _, err := VerifySessionToken(tok); err == nil {
+		t.Fatalf("expected expiry error, got nil")
+	}
+}
+
+func TestSessionTokenTampered(t *testing.T) {
+	t.Setenv("KEY_ENCRYPTION_KEY", "00112233445566778899aabbccddeeff00112233445566778899aabbccddeeff")
+
+	tok, _ := SignSessionToken("sess-123", time.Minute)
+	if _, err := VerifySessionToken(tok + "x"); err == nil {
+		t.Fatalf("expected signature error, got nil")
+	}
+}