auth/cluster.go

@@ -0,0 +1,77 @@
+package auth
+
+import (
+	"net/http"
+
+	"github.com/sirupsen/logrus"
+)
+
+// ClusterAuthService handles authentication for inter-cluster communication
+type ClusterAuthService struct {
+	clusterSecret string
+	logger        *logrus.Logger
+}
+
+// NewClusterAuthService creates a new cluster authentication service
+func NewClusterAuthService(clusterSecret string, logger *logrus.Logger) *ClusterAuthService {
+	return &ClusterAuthService{
+		clusterSecret: clusterSecret,
+		logger:        logger,
+	}
+}
+
+// Middleware validates cluster authentication headers
+func (s *ClusterAuthService) Middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Extract authentication headers
+		clusterSecret := r.Header.Get("X-Cluster-Secret")
+		nodeID := r.Header.Get("X-Node-ID")
+
+		// Log authentication attempt
+		s.logger.WithFields(logrus.Fields{
+			"node_id":     nodeID,
+			"remote_addr": r.RemoteAddr,
+			"path":        r.URL.Path,
+			"method":      r.Method,
+		}).Debug("Cluster authentication attempt")
+
+		// Validate cluster secret
+		if clusterSecret == "" {
+			s.logger.WithFields(logrus.Fields{
+				"node_id":     nodeID,
+				"remote_addr": r.RemoteAddr,
+				"path":        r.URL.Path,
+			}).Warn("Missing X-Cluster-Secret header")
+			http.Error(w, "Unauthorized: Missing cluster secret", http.StatusUnauthorized)
+			return
+		}
+
+		if clusterSecret != s.clusterSecret {
+			s.logger.WithFields(logrus.Fields{
+				"node_id":     nodeID,
+				"remote_addr": r.RemoteAddr,
+				"path":        r.URL.Path,
+			}).Warn("Invalid cluster secret")
+			http.Error(w, "Unauthorized: Invalid cluster secret", http.StatusUnauthorized)
+			return
+		}
+
+		// Validate node ID is present
+		if nodeID == "" {
+			s.logger.WithFields(logrus.Fields{
+				"remote_addr": r.RemoteAddr,
+				"path":        r.URL.Path,
+			}).Warn("Missing X-Node-ID header")
+			http.Error(w, "Unauthorized: Missing node ID", http.StatusUnauthorized)
+			return
+		}
+
+		// Authentication successful
+		s.logger.WithFields(logrus.Fields{
+			"node_id": nodeID,
+			"path":    r.URL.Path,
+		}).Debug("Cluster authentication successful")
+
+		next.ServeHTTP(w, r)
+	})
+}

cluster/bootstrap.go

@@ -82,10 +82,19 @@ func (s *BootstrapService) attemptJoin(seedAddr string) bool {
 		return false
 	}
 
-	client := &http.Client{Timeout: 10 * time.Second}
+	client := NewAuthenticatedHTTPClient(s.config, 10*time.Second)
-	url := fmt.Sprintf("http://%s/members/join", seedAddr)
+	protocol := GetProtocol(s.config)
+	url := fmt.Sprintf("%s://%s/members/join", protocol, seedAddr)
 
-	resp, err := client.Post(url, "application/json", bytes.NewBuffer(jsonData))
+	req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
+	if err != nil {
+		s.logger.WithError(err).Error("Failed to create join request")
+		return false
+	}
+	req.Header.Set("Content-Type", "application/json")
+	AddClusterAuthHeaders(req, s.config)
+
+	resp, err := client.Do(req)
 	if err != nil {
 		s.logger.WithFields(logrus.Fields{
 			"seed":  seedAddr,

cluster/gossip.go

@@ -181,11 +181,20 @@ func (s *GossipService) gossipWithPeer(peer *types.Member) error {
 		return err
 	}
 
-	// Send HTTP request to peer
+	// Send HTTP request to peer with cluster authentication
-	client := &http.Client{Timeout: 5 * time.Second}
+	client := NewAuthenticatedHTTPClient(s.config, 5*time.Second)
-	url := fmt.Sprintf("http://%s/members/gossip", peer.Address)
+	protocol := GetProtocol(s.config)
+	url := fmt.Sprintf("%s://%s/members/gossip", protocol, peer.Address)
 
-	resp, err := client.Post(url, "application/json", bytes.NewBuffer(jsonData))
+	req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
+	if err != nil {
+		s.logger.WithError(err).Error("Failed to create gossip request")
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	AddClusterAuthHeaders(req, s.config)
+
+	resp, err := client.Do(req)
 	if err != nil {
 		s.logger.WithFields(logrus.Fields{
 			"peer":  peer.Address,

cluster/http_client.go

@@ -0,0 +1,43 @@
+package cluster
+
+import (
+	"crypto/tls"
+	"net/http"
+	"time"
+
+	"kvs/types"
+)
+
+// NewAuthenticatedHTTPClient creates an HTTP client configured for cluster authentication
+func NewAuthenticatedHTTPClient(config *types.Config, timeout time.Duration) *http.Client {
+	client := &http.Client{
+		Timeout: timeout,
+	}
+
+	// Configure TLS if enabled
+	if config.ClusterTLSEnabled {
+		tlsConfig := &tls.Config{
+			InsecureSkipVerify: config.ClusterTLSSkipVerify,
+		}
+
+		client.Transport = &http.Transport{
+			TLSClientConfig: tlsConfig,
+		}
+	}
+
+	return client
+}
+
+// AddClusterAuthHeaders adds authentication headers to an HTTP request
+func AddClusterAuthHeaders(req *http.Request, config *types.Config) {
+	req.Header.Set("X-Cluster-Secret", config.ClusterSecret)
+	req.Header.Set("X-Node-ID", config.NodeID)
+}
+
+// GetProtocol returns the appropriate protocol (http or https) based on TLS configuration
+func GetProtocol(config *types.Config) string {
+	if config.ClusterTLSEnabled {
+		return "https"
+	}
+	return "http"
+}

cluster/sync.go

@@ -186,10 +186,17 @@ func (s *SyncService) performMerkleSync() {
 
 // requestMerkleRoot requests the Merkle root from a peer
 func (s *SyncService) requestMerkleRoot(peerAddress string) (*types.MerkleRootResponse, error) {
-	client := &http.Client{Timeout: 10 * time.Second}
+	client := NewAuthenticatedHTTPClient(s.config, 10*time.Second)
-	url := fmt.Sprintf("http://%s/merkle_tree/root", peerAddress)
+	protocol := GetProtocol(s.config)
+	url := fmt.Sprintf("%s://%s/merkle_tree/root", protocol, peerAddress)
 
-	resp, err := client.Get(url)
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	AddClusterAuthHeaders(req, s.config)
+
+	resp, err := client.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -294,10 +301,17 @@ func (s *SyncService) handleLeafLevelDiff(peerAddress string, keys []string, loc
 
 // fetchSingleKVFromPeer fetches a single KV pair from a peer
 func (s *SyncService) fetchSingleKVFromPeer(peerAddress, path string) (*types.StoredValue, error) {
-	client := &http.Client{Timeout: 5 * time.Second}
+	client := NewAuthenticatedHTTPClient(s.config, 5*time.Second)
-	url := fmt.Sprintf("http://%s/kv/%s", peerAddress, path)
+	protocol := GetProtocol(s.config)
+	url := fmt.Sprintf("%s://%s/kv/%s", protocol, peerAddress, path)
 
-	resp, err := client.Get(url)
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	AddClusterAuthHeaders(req, s.config)
+
+	resp, err := client.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -461,16 +475,24 @@ func (s *SyncService) resolveConflict(key string, local, remote *types.StoredVal
 }
 
 // requestMerkleDiff requests children hashes or keys for a given node/range from a peer
-func (s *SyncService) requestMerkleDiff(peerAddress string, req types.MerkleTreeDiffRequest) (*types.MerkleTreeDiffResponse, error) {
+func (s *SyncService) requestMerkleDiff(peerAddress string, reqData types.MerkleTreeDiffRequest) (*types.MerkleTreeDiffResponse, error) {
-	jsonData, err := json.Marshal(req)
+	jsonData, err := json.Marshal(reqData)
 	if err != nil {
 		return nil, err
 	}
 
-	client := &http.Client{Timeout: 10 * time.Second}
+	client := NewAuthenticatedHTTPClient(s.config, 10*time.Second)
-	url := fmt.Sprintf("http://%s/merkle_tree/diff", peerAddress)
+	protocol := GetProtocol(s.config)
+	url := fmt.Sprintf("%s://%s/merkle_tree/diff", protocol, peerAddress)
 
-	resp, err := client.Post(url, "application/json", bytes.NewBuffer(jsonData))
+	req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	AddClusterAuthHeaders(req, s.config)
+
+	resp, err := client.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -525,20 +547,28 @@ func (s *SyncService) handleChildrenDiff(peerAddress string, children []types.Me
 
 // fetchAndStoreRange fetches a range of KV pairs from a peer and stores them locally
 func (s *SyncService) fetchAndStoreRange(peerAddress string, startKey, endKey string) error {
-	req := types.KVRangeRequest{
+	reqData := types.KVRangeRequest{
 		StartKey: startKey,
 		EndKey:   endKey,
 		Limit:    0, // No limit
 	}
-	jsonData, err := json.Marshal(req)
+	jsonData, err := json.Marshal(reqData)
 	if err != nil {
 		return err
 	}
 
-	client := &http.Client{Timeout: 30 * time.Second} // Longer timeout for range fetches
+	client := NewAuthenticatedHTTPClient(s.config, 30*time.Second) // Longer timeout for range fetches
-	url := fmt.Sprintf("http://%s/kv_range", peerAddress)
+	protocol := GetProtocol(s.config)
+	url := fmt.Sprintf("%s://%s/kv_range", protocol, peerAddress)
 
-	resp, err := client.Post(url, "application/json", bytes.NewBuffer(jsonData))
+	req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	AddClusterAuthHeaders(req, s.config)
+
+	resp, err := client.Do(req)
 	if err != nil {
 		return err
 	}

config/config.go

@@ -1,12 +1,14 @@
 package config
 
 import (
+	"crypto/rand"
+	"encoding/base64"
 	"fmt"
 	"os"
 	"path/filepath"
 
-	"kvs/types"
 	"gopkg.in/yaml.v3"
+	"kvs/types"
 )
 
 // Default configuration
@@ -59,9 +61,29 @@ func Default() *types.Config {
 		// Default anonymous access settings (both disabled by default for security)
 		AllowAnonymousRead:  false,
 		AllowAnonymousWrite: false,
+
+		// Default cluster authentication settings (Issue #13)
+		ClusterSecret:        generateClusterSecret(),
+		ClusterTLSEnabled:    false,
+		ClusterTLSCertFile:   "",
+		ClusterTLSKeyFile:    "",
+		ClusterTLSSkipVerify: false,
 	}
 }
 
+// generateClusterSecret generates a cryptographically secure random cluster secret
+func generateClusterSecret() string {
+	// Generate 32 bytes (256 bits) of random data
+	randomBytes := make([]byte, 32)
+	if _, err := rand.Read(randomBytes); err != nil {
+		// Fallback to a warning - this should never happen in practice
+		fmt.Fprintf(os.Stderr, "Warning: Failed to generate secure cluster secret: %v\n", err)
+		return ""
+	}
+	// Encode as base64 for easy configuration file storage
+	return base64.StdEncoding.EncodeToString(randomBytes)
+}
+
 // Load configuration from file or create default
 func Load(configPath string) (*types.Config, error) {
 	config := Default()
@@ -94,5 +116,13 @@ func Load(configPath string) (*types.Config, error) {
 		return nil, fmt.Errorf("failed to parse config file: %v", err)
 	}
 
+	// Generate cluster secret if not provided and clustering is enabled (Issue #13)
+	if config.ClusteringEnabled && config.ClusterSecret == "" {
+		config.ClusterSecret = generateClusterSecret()
+		fmt.Printf("Warning: No cluster_secret configured. Generated a random secret.\n")
+		fmt.Printf("         To share this secret with other nodes, add it to your config:\n")
+		fmt.Printf("         cluster_secret: %s\n", config.ClusterSecret)
+	}
+
 	return config, nil
 }

integration_test.sh

@@ -125,6 +125,9 @@ EOF
 test_cluster_formation() {
     test_start "2-node cluster formation and Merkle Tree replication"
 
+    # Shared cluster secret for authentication (Issue #13)
+    local CLUSTER_SECRET="test-cluster-secret-12345678901234567890"
+
     # Node 1 config
     cat > cluster1.yaml <<EOF
 node_id: "cluster-1"
@@ -138,6 +141,7 @@ gossip_interval_max: 10
 sync_interval: 10
 allow_anonymous_read: true
 allow_anonymous_write: true
+cluster_secret: "$CLUSTER_SECRET"
 EOF
 
     # Node 2 config
@@ -153,6 +157,7 @@ gossip_interval_max: 10
 sync_interval: 10
 allow_anonymous_read: true
 allow_anonymous_write: true
+cluster_secret: "$CLUSTER_SECRET"
 EOF
     
     # Start nodes
@@ -239,6 +244,9 @@ test_conflict_resolution() {
     if go run test_conflict.go "$TEST_DIR/conflict1_data" "$TEST_DIR/conflict2_data"; then
         cd "$TEST_DIR"
 
+        # Shared cluster secret for authentication (Issue #13)
+        local CLUSTER_SECRET="conflict-cluster-secret-1234567890123"
+
         # Create configs
         cat > conflict1.yaml <<EOF
 node_id: "conflict-1"
@@ -250,6 +258,7 @@ log_level: "info"
 sync_interval: 3
 allow_anonymous_read: true
 allow_anonymous_write: true
+cluster_secret: "$CLUSTER_SECRET"
 EOF
 
         cat > conflict2.yaml <<EOF
@@ -262,6 +271,7 @@ log_level: "info"
 sync_interval: 3
 allow_anonymous_read: true
 allow_anonymous_write: true
+cluster_secret: "$CLUSTER_SECRET"
 EOF
         
         # Start nodes

main.go

@@ -11,7 +11,6 @@ import (
 	"kvs/server"
 )
 
-
 func main() {
 	configPath := "./config.yaml"
 

server/handlers.go

@@ -22,8 +22,6 @@ import (
 	"kvs/utils"
 )
 
-
-
 // healthHandler returns server health status
 func (s *Server) healthHandler(w http.ResponseWriter, r *http.Request) {
 	mode := s.getMode()
@@ -1271,3 +1269,29 @@ func (s *Server) getRevisionHistory(key string) ([]map[string]interface{}, error
 func (s *Server) getSpecificRevision(key string, revision int) (*types.StoredValue, error) {
 	return s.revisionService.GetSpecificRevision(key, revision)
 }
+
+// clusterBootstrapHandler provides the cluster secret to authenticated administrators (Issue #13)
+func (s *Server) clusterBootstrapHandler(w http.ResponseWriter, r *http.Request) {
+	// Ensure clustering is enabled
+	if !s.config.ClusteringEnabled {
+		http.Error(w, "Clustering is disabled", http.StatusServiceUnavailable)
+		return
+	}
+
+	// Ensure cluster secret is configured
+	if s.config.ClusterSecret == "" {
+		s.logger.Error("Cluster secret is not configured")
+		http.Error(w, "Cluster secret is not configured", http.StatusInternalServerError)
+		return
+	}
+
+	// Return the cluster secret for secure bootstrap
+	response := map[string]string{
+		"cluster_secret": s.config.ClusterSecret,
+	}
+
+	s.logger.WithField("remote_addr", r.RemoteAddr).Info("Cluster secret retrieved for bootstrap")
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(response)
+}

server/routes.go

@@ -1,6 +1,8 @@
 package server
 
 import (
+	"net/http"
+
 	"github.com/gorilla/mux"
 )
 
@@ -41,7 +43,22 @@ func (s *Server) setupRoutes() *mux.Router {
 
 	// Member endpoints (available when clustering is enabled)
 	if s.config.ClusteringEnabled {
+		// GET /members/ is unprotected for monitoring/inspection
 		router.HandleFunc("/members/", s.getMembersHandler).Methods("GET")
+
+		// Apply cluster authentication middleware to all cluster communication endpoints
+		if s.clusterAuthService != nil {
+			router.Handle("/members/join", s.clusterAuthService.Middleware(http.HandlerFunc(s.joinMemberHandler))).Methods("POST")
+			router.Handle("/members/leave", s.clusterAuthService.Middleware(http.HandlerFunc(s.leaveMemberHandler))).Methods("DELETE")
+			router.Handle("/members/gossip", s.clusterAuthService.Middleware(http.HandlerFunc(s.gossipHandler))).Methods("POST")
+			router.Handle("/members/pairs_by_time", s.clusterAuthService.Middleware(http.HandlerFunc(s.pairsByTimeHandler))).Methods("POST")
+
+			// Merkle Tree endpoints (clustering feature)
+			router.Handle("/merkle_tree/root", s.clusterAuthService.Middleware(http.HandlerFunc(s.getMerkleRootHandler))).Methods("GET")
+			router.Handle("/merkle_tree/diff", s.clusterAuthService.Middleware(http.HandlerFunc(s.getMerkleDiffHandler))).Methods("POST")
+			router.Handle("/kv_range", s.clusterAuthService.Middleware(http.HandlerFunc(s.getKVRangeHandler))).Methods("POST")
+		} else {
+			// Fallback to unprotected endpoints (for backwards compatibility)
 			router.HandleFunc("/members/join", s.joinMemberHandler).Methods("POST")
 			router.HandleFunc("/members/leave", s.leaveMemberHandler).Methods("DELETE")
 			router.HandleFunc("/members/gossip", s.gossipHandler).Methods("POST")
@@ -52,6 +69,7 @@ func (s *Server) setupRoutes() *mux.Router {
 			router.HandleFunc("/merkle_tree/diff", s.getMerkleDiffHandler).Methods("POST")
 			router.HandleFunc("/kv_range", s.getKVRangeHandler).Methods("POST")
 		}
+	}
 
 	// Authentication and user management endpoints (available when auth is enabled)
 	if s.config.AuthEnabled {
@@ -93,6 +111,12 @@ func (s *Server) setupRoutes() *mux.Router {
 		router.Handle("/api/tokens", s.authService.Middleware(
 			[]string{"admin:tokens:create"}, nil, "",
 		)(s.createTokenHandler)).Methods("POST")
+
+		// Cluster Bootstrap endpoint (Issue #13) - Protected by JWT authentication
+		// Allows authenticated administrators to retrieve the cluster secret for new nodes
+		router.Handle("/auth/cluster-bootstrap", s.authService.Middleware(
+			[]string{"admin:tokens:create"}, nil, "",
+		)(s.clusterBootstrapHandler)).Methods("GET")
 	}
 
 	// Revision History endpoints (available when revision history is enabled)

server/server.go

@@ -51,6 +51,7 @@ type Server struct {
 
 	// Authentication service
 	authService        *auth.AuthService
+	clusterAuthService *auth.ClusterAuthService
 }
 
 // NewServer initializes and returns a new Server instance
@@ -120,6 +121,11 @@ func NewServer(config *types.Config) (*Server, error) {
 	// Initialize authentication service
 	server.authService = auth.NewAuthService(db, logger, config)
 
+	// Initialize cluster authentication service (Issue #13)
+	if config.ClusteringEnabled {
+		server.clusterAuthService = auth.NewClusterAuthService(config.ClusterSecret, logger)
+	}
+
 	// Setup initial root account if needed (Issue #3)
 	if config.AuthEnabled {
 		if err := server.setupRootAccount(); err != nil {
@@ -327,4 +333,3 @@ func (s *Server) storeUserAndGroup(user *types.User, group *types.Group) error {
 		return nil
 	})
 }
-

types/types.go

@@ -277,4 +277,11 @@ type Config struct {
 	// Anonymous access control (Issue #5)
 	AllowAnonymousRead  bool `yaml:"allow_anonymous_read"`  // Allow unauthenticated read access to KV endpoints
 	AllowAnonymousWrite bool `yaml:"allow_anonymous_write"` // Allow unauthenticated write access to KV endpoints
+
+	// Cluster authentication (Issue #13)
+	ClusterSecret        string `yaml:"cluster_secret"`          // Shared secret for cluster authentication (auto-generated if empty)
+	ClusterTLSEnabled    bool   `yaml:"cluster_tls_enabled"`     // Require TLS for inter-node communication
+	ClusterTLSCertFile   string `yaml:"cluster_tls_cert_file"`   // Path to TLS certificate file
+	ClusterTLSKeyFile    string `yaml:"cluster_tls_key_file"`    // Path to TLS private key file
+	ClusterTLSSkipVerify bool   `yaml:"cluster_tls_skip_verify"` // Skip TLS verification (insecure, for testing only)
 }