[management, reverse proxy] Add reverse proxy feature (#5291)

* implement reverse proxy


---------

Co-authored-by: Alisdair MacLeod <git@alisdairmacleod.co.uk>
Co-authored-by: mlsmaycon <mlsmaycon@gmail.com>
Co-authored-by: Eduard Gert <kontakt@eduardgert.de>
Co-authored-by: Viktor Liu <viktor@netbird.io>
Co-authored-by: Diego Noguês <diego.sure@gmail.com>
Co-authored-by: Diego Noguês <49420+diegocn@users.noreply.github.com>
Co-authored-by: Bethuel Mmbaga <bethuelmbaga12@gmail.com>
Co-authored-by: Zoltan Papp <zoltan.pmail@gmail.com>
Co-authored-by: Ashley Mensah <ashleyamo982@gmail.com>

management/internals/shared/grpc/onetime_token.go

@@ -0,0 +1,167 @@
+package grpc
+
+import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/base64"
+	"fmt"
+	"sync"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// OneTimeTokenStore manages short-lived, single-use authentication tokens
+// for proxy-to-management RPC authentication. Tokens are generated when
+// a service is created and must be used exactly once by the proxy
+// to authenticate a subsequent RPC call.
+type OneTimeTokenStore struct {
+	tokens      map[string]*tokenMetadata
+	mu          sync.RWMutex
+	cleanup     *time.Ticker
+	cleanupDone chan struct{}
+}
+
+// tokenMetadata stores information about a one-time token
+type tokenMetadata struct {
+	ServiceID string
+	AccountID string
+	ExpiresAt time.Time
+	CreatedAt time.Time
+}
+
+// NewOneTimeTokenStore creates a new token store with automatic cleanup
+// of expired tokens. The cleanupInterval determines how often expired
+// tokens are removed from memory.
+func NewOneTimeTokenStore(cleanupInterval time.Duration) *OneTimeTokenStore {
+	store := &OneTimeTokenStore{
+		tokens:      make(map[string]*tokenMetadata),
+		cleanup:     time.NewTicker(cleanupInterval),
+		cleanupDone: make(chan struct{}),
+	}
+
+	// Start background cleanup goroutine
+	go store.cleanupExpired()
+
+	return store
+}
+
+// GenerateToken creates a new cryptographically secure one-time token
+// with the specified TTL. The token is associated with a specific
+// accountID and serviceID for validation purposes.
+//
+// Returns the generated token string or an error if random generation fails.
+func (s *OneTimeTokenStore) GenerateToken(accountID, serviceID string, ttl time.Duration) (string, error) {
+	// Generate 32 bytes (256 bits) of cryptographically secure random data
+	randomBytes := make([]byte, 32)
+	if _, err := rand.Read(randomBytes); err != nil {
+		return "", fmt.Errorf("failed to generate random token: %w", err)
+	}
+
+	// Encode as URL-safe base64 for easy transmission in gRPC
+	token := base64.URLEncoding.EncodeToString(randomBytes)
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.tokens[token] = &tokenMetadata{
+		ServiceID: serviceID,
+		AccountID: accountID,
+		ExpiresAt: time.Now().Add(ttl),
+		CreatedAt: time.Now(),
+	}
+
+	log.Debugf("Generated one-time token for proxy %s in account %s (expires in %s)",
+		serviceID, accountID, ttl)
+
+	return token, nil
+}
+
+// ValidateAndConsume verifies the token against the provided accountID and
+// serviceID, checks expiration, and then deletes it to enforce single-use.
+//
+// This method uses constant-time comparison to prevent timing attacks.
+//
+// Returns nil on success, or an error if:
+// - Token doesn't exist
+// - Token has expired
+// - Account ID doesn't match
+// - Reverse proxy ID doesn't match
+func (s *OneTimeTokenStore) ValidateAndConsume(token, accountID, serviceID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	metadata, exists := s.tokens[token]
+	if !exists {
+		log.Warnf("Token validation failed: token not found (proxy: %s, account: %s)",
+			serviceID, accountID)
+		return fmt.Errorf("invalid token")
+	}
+
+	// Check expiration
+	if time.Now().After(metadata.ExpiresAt) {
+		delete(s.tokens, token)
+		log.Warnf("Token validation failed: token expired (proxy: %s, account: %s)",
+			serviceID, accountID)
+		return fmt.Errorf("token expired")
+	}
+
+	// Validate account ID using constant-time comparison (prevents timing attacks)
+	if subtle.ConstantTimeCompare([]byte(metadata.AccountID), []byte(accountID)) != 1 {
+		log.Warnf("Token validation failed: account ID mismatch (expected: %s, got: %s)",
+			metadata.AccountID, accountID)
+		return fmt.Errorf("account ID mismatch")
+	}
+
+	// Validate service ID using constant-time comparison
+	if subtle.ConstantTimeCompare([]byte(metadata.ServiceID), []byte(serviceID)) != 1 {
+		log.Warnf("Token validation failed: service ID mismatch (expected: %s, got: %s)",
+			metadata.ServiceID, serviceID)
+		return fmt.Errorf("service ID mismatch")
+	}
+
+	// Delete token immediately to enforce single-use
+	delete(s.tokens, token)
+
+	log.Infof("Token validated and consumed for proxy %s in account %s",
+		serviceID, accountID)
+
+	return nil
+}
+
+// cleanupExpired removes expired tokens in the background to prevent memory leaks
+func (s *OneTimeTokenStore) cleanupExpired() {
+	for {
+		select {
+		case <-s.cleanup.C:
+			s.mu.Lock()
+			now := time.Now()
+			removed := 0
+			for token, metadata := range s.tokens {
+				if now.After(metadata.ExpiresAt) {
+					delete(s.tokens, token)
+					removed++
+				}
+			}
+			if removed > 0 {
+				log.Debugf("Cleaned up %d expired one-time tokens", removed)
+			}
+			s.mu.Unlock()
+		case <-s.cleanupDone:
+			return
+		}
+	}
+}
+
+// Close stops the cleanup goroutine and releases resources
+func (s *OneTimeTokenStore) Close() {
+	s.cleanup.Stop()
+	close(s.cleanupDone)
+}
+
+// GetTokenCount returns the current number of tokens in the store (for debugging/metrics)
+func (s *OneTimeTokenStore) GetTokenCount() int {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return len(s.tokens)
+}