fix: security and correctness hardening across API, tools, MCP, persistence, and gateways

internal/api/server.go

@@ -5,11 +5,13 @@ import (
 	"context"
 	"crypto/subtle"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net"
 	"net/http"
 	"strings"
 	"sync"
+	"time"
 )
 
 const maxRequestBodyBytes = 1 << 20
@@ -74,9 +76,19 @@ func NewWithAPIKey(addr, apiKey string) *Server {
 
 // registerRoutes sets up the HTTP endpoints.
 func (s *Server) registerRoutes() {
-	s.mux.HandleFunc("GET /health", s.handleHealth)
-	s.mux.HandleFunc("GET /version", s.handleVersion)
-	s.mux.HandleFunc("POST /chat", s.auth(s.handleChat))
+	s.mux.HandleFunc("GET /health", securityHeaders(s.handleHealth))
+	s.mux.HandleFunc("GET /version", securityHeaders(s.handleVersion))
+	s.mux.HandleFunc("POST /chat", securityHeaders(s.auth(s.handleChat)))
+}
+
+// securityHeaders sets standard HTTP security headers on every response.
+func securityHeaders(next http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("X-Content-Type-Options", "nosniff")
+		w.Header().Set("X-Frame-Options", "DENY")
+		w.Header().Set("Cache-Control", "no-store")
+		next(w, r)
+	}
 }
 
 func (s *Server) auth(next http.HandlerFunc) http.HandlerFunc {
@@ -110,6 +122,35 @@ func constantTimeEqual(a, b string) bool {
 	return subtle.ConstantTimeCompare([]byte(a), []byte(b)) == 1
 }
 
+// validateAuthConfig refuses to start the server with no API key on a
+// non-loopback bind. The auth middleware silently allows every request when
+// the API key is empty, so a misconfigured server would be wide open. The
+// only safe no-key mode is loopback bind.
+func (s *Server) validateAuthConfig() error {
+	if s.apiKey != "" {
+		return nil
+	}
+	host, _, err := net.SplitHostPort(s.addr)
+	if err != nil {
+		return fmt.Errorf("api: invalid bind address %q: %w", s.addr, err)
+	}
+	if !isLoopbackHost(host) {
+		return fmt.Errorf("api: apiKey is empty and bind address %q is not loopback; refusing to start. Set apiKey or bind to 127.0.0.1", s.addr)
+	}
+	return nil
+}
+
+// isLoopbackHost reports whether host is a loopback address.
+func isLoopbackHost(host string) bool {
+	if host == "" || host == "localhost" {
+		return host == "localhost" // "" is unsafe; "localhost" is loopback
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		return ip.IsLoopback()
+	}
+	return false
+}
+
 func decodeJSONBody(w http.ResponseWriter, r *http.Request, dst any) bool {
 	r.Body = http.MaxBytesReader(w, r.Body, maxRequestBodyBytes)
 	dec := json.NewDecoder(r.Body)
@@ -127,10 +168,17 @@ func decodeJSONBody(w http.ResponseWriter, r *http.Request, dst any) bool {
 
 // Start starts the HTTP server. It blocks until the context is cancelled or an error occurs.
 func (s *Server) Start(ctx context.Context) error {
+	if err := s.validateAuthConfig(); err != nil {
+		return err
+	}
 	s.mu.Lock()
 	s.server = &http.Server{
-		Addr:    s.addr,
-		Handler: s.mux,
+		Addr:              s.addr,
+		Handler:           s.mux,
+		ReadHeaderTimeout: 10 * time.Second,
+		ReadTimeout:       30 * time.Second,
+		WriteTimeout:      30 * time.Second,
+		IdleTimeout:       120 * time.Second,
 	}
 	s.mu.Unlock()
 
@@ -151,7 +199,7 @@ func (s *Server) Start(ctx context.Context) error {
 	return err
 }
 
-// Stop gracefully shuts down the HTTP server.
+// Stop gracefully shuts down the HTTP server with a 15-second timeout.
 func (s *Server) Stop(ctx context.Context) error {
 	s.mu.Lock()
 	srv := s.server
@@ -160,7 +208,12 @@ func (s *Server) Stop(ctx context.Context) error {
 	if srv == nil {
 		return nil
 	}
-	return srv.Shutdown(ctx)
+	// Use a bounded timeout so Stop cannot hang indefinitely if a
+	// client keeps a connection open. The caller's ctx is respected
+	// if it has a shorter deadline.
+	shutdownCtx, cancel := context.WithTimeout(ctx, 15*time.Second)
+	defer cancel()
+	return srv.Shutdown(shutdownCtx)
 }
 
 // Handler returns the underlying http.Handler for testing purposes.

internal/daemon/discord.go

@@ -201,7 +201,7 @@ func (g *DiscordGateway) fetchMessagesREST(ctx context.Context, channelID, after
 	}
 	defer func() { _ = resp.Body.Close() }()
 	if resp.StatusCode != http.StatusOK {
-		data, _ := io.ReadAll(resp.Body)
+		data, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
 		return nil, fmt.Errorf("discord messages: HTTP %d: %s", resp.StatusCode, string(data))
 	}
 	var msgs []discordMessage

internal/daemon/gateway.go

@@ -29,7 +29,7 @@ func forwardToHawk(ctx context.Context, client *http.Client, daemonAddr, apiKey,
 		return "", err
 	}
 	defer func() { _ = resp.Body.Close() }()
-	body, _ := io.ReadAll(resp.Body)
+	body, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	var chatResp struct {
 		Response string `json:"response"`
 	}

internal/daemon/telegram.go

@@ -152,17 +152,23 @@ func (tg *TelegramGateway) handleMessage(ctx context.Context, msg *TelegramMessa
 		response = fmt.Sprintf("Error: %v", err)
 	}
 
-	// Format for Telegram (truncate if too long)
-	if len(response) > 4000 {
-		response = response[:4000] + "\n\n... (truncated)"
+	// Format for Telegram (truncate if too long, at rune boundary)
+	if len([]rune(response)) > 4000 {
+		response = string([]rune(response)[:4000]) + "\n\n... (truncated)"
 	}
 
 	_ = tg.sendMessage(ctx, msg.Chat.ID, response)
 }
 
 func (tg *TelegramGateway) forwardToHawk(ctx context.Context, prompt string) (string, error) {
-	payload := fmt.Sprintf(`{"prompt":%q}`, prompt)
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tg.DaemonAddr+"/v1/chat", strings.NewReader(payload))
+	// Use json.Marshal for safe JSON encoding instead of fmt.Sprintf
+	// with %q, which does not handle all JSON edge cases (e.g., control
+	// characters, surrogate pairs).
+	payload, err := json.Marshal(map[string]string{"prompt": prompt})
+	if err != nil {
+		return "", fmt.Errorf("encode prompt: %w", err)
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tg.DaemonAddr+"/v1/chat", strings.NewReader(string(payload)))
 	if err != nil {
 		return "", err
 	}
@@ -177,7 +183,8 @@ func (tg *TelegramGateway) forwardToHawk(ctx context.Context, prompt string) (st
 	}
 	defer func() { _ = resp.Body.Close() }()
 
-	body, _ := io.ReadAll(resp.Body)
+	// Limit response body to 1 MiB to prevent memory exhaustion.
+	body, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	var chatResp struct {
 		Response string `json:"response"`
 	}

internal/engine/session.go

@@ -35,6 +35,7 @@ type MemoryRecaller interface {
 // SnapshotTracker abstracts the snapshot system so engine doesn't import snapshot directly.
 type SnapshotTracker interface {
 	Track(message string) (string, error)
+	TrackCtx(ctx context.Context, message string) (string, error)
 }
 
 // Session manages a conversation with an LLM via eyrie.

internal/engine/stream.go

@@ -460,9 +460,11 @@ func (s *Session) agentLoop(ctx context.Context, ch chan<- StreamEvent) {
 				"reason":  retryReason,
 				"error":   streamErr.Error(),
 			})
+			retryTimer := time.NewTimer(time.Duration(streamAttempt+1) * time.Second)
 			select {
-			case <-time.After(time.Duration(streamAttempt+1) * time.Second):
+			case <-retryTimer.C:
 			case <-ctx.Done():
+				retryTimer.Stop()
 				ch <- StreamEvent{Type: "error", Content: "stream retry cancelled: " + ctx.Err().Error()}
 				result.Close()
 				return
@@ -730,7 +732,13 @@ func (s *Session) agentLoop(ctx context.Context, ch chan<- StreamEvent) {
 				}
 			}
 			if len(writeNames) > 0 {
-				go func() { _, _ = s.Snapshots.Track(strings.Join(writeNames, ", ")) }()
+				go func() {
+					// Bound the snapshot so a slow filesystem doesn't
+					// leak a goroutine after the session ends.
+					snapCtx, snapCancel := context.WithTimeout(context.Background(), 30*time.Second)
+					defer snapCancel()
+					_, _ = s.Snapshots.TrackCtx(snapCtx, strings.Join(writeNames, ", "))
+				}()
 			}
 		}
 

internal/mcp/mcp.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"log/slog"
 	"os/exec"
 	"strings"
 	"sync"
@@ -24,17 +25,18 @@ func SetClientVersion(v string) { clientVersion = v }
 
 // Server represents a connected MCP server.
 type Server struct {
-	Name    string
-	Command string
-	Args    []string
-	cmd     *exec.Cmd
-	stdin   io.WriteCloser
-	stdout  io.ReadCloser
-	mu      sync.Mutex
-	nextID  int
-	reader  *bufio.Scanner
-	pending map[int]chan json.RawMessage // response channels keyed by request ID
-	pendMu  sync.Mutex
+	Name       string
+	Command    string
+	Args       []string
+	cmd        *exec.Cmd
+	stdin      io.WriteCloser
+	stdout     io.ReadCloser
+	mu         sync.Mutex
+	nextID     int
+	reader     *bufio.Scanner
+	pending    map[int]chan json.RawMessage // response channels keyed by request ID
+	pendErrors map[int]string               // error details keyed by request ID
+	pendMu     sync.Mutex
 }
 
 // Tool is a tool exposed by an MCP server.
@@ -91,14 +93,15 @@ func Connect(ctx context.Context, name, command string, args ...string) (*Server
 	scanner.Buffer(make([]byte, 0, 1024*1024), 1024*1024) // 1MB buffer
 
 	s := &Server{
-		Name:    name,
-		Command: command,
-		Args:    args,
-		cmd:     cmd,
-		stdin:   stdin,
-		stdout:  stdout,
-		reader:  scanner,
-		pending: make(map[int]chan json.RawMessage),
+		Name:       name,
+		Command:    command,
+		Args:       args,
+		cmd:        cmd,
+		stdin:      stdin,
+		stdout:     stdout,
+		reader:     scanner,
+		pending:    make(map[int]chan json.RawMessage),
+		pendErrors: make(map[int]string),
 	}
 
 	// Start background reader to dispatch responses and notifications
@@ -142,6 +145,11 @@ func (s *Server) readLoop() {
 			s.pendMu.Unlock()
 			if ok {
 				if msg.Error != nil {
+					// Store error details so the caller can include them
+					// in the returned error instead of a generic message.
+					s.pendMu.Lock()
+					s.pendErrors[msg.ID] = fmt.Sprintf("code %d: %s", msg.Error.Code, msg.Error.Message)
+					s.pendMu.Unlock()
 					ch <- nil // signal error via nil
 				} else {
 					ch <- msg.Result
@@ -152,11 +160,19 @@ func (s *Server) readLoop() {
 		}
 		// Otherwise it's a notification — ignore for now
 	}
-	// Scanner done — close all pending channels
+	// Scanner done — log the cause if it was an error (e.g., oversized
+	// response exceeding the 1MB buffer), then close all pending channels.
+	if err := s.reader.Err(); err != nil {
+		slog.Warn("mcp: stdout reader stopped", "server", s.Name, "error", err)
+	}
 	s.pendMu.Lock()
 	for id, ch := range s.pending {
 		close(ch)
 		delete(s.pending, id)
+		// Clean up pendErrors only for requests that will never be
+		// answered. Entries for already-signaled requests (no longer in
+		// s.pending) are left for the caller to reap.
+		delete(s.pendErrors, id)
 	}
 	s.pendMu.Unlock()
 }
@@ -309,6 +325,7 @@ func (s *Server) callWithTimeout(ctx context.Context, method string, params inte
 	if err != nil {
 		s.pendMu.Lock()
 		delete(s.pending, id)
+		delete(s.pendErrors, id)
 		s.pendMu.Unlock()
 		return nil, fmt.Errorf("write: %w", err)
 	}
@@ -319,23 +336,40 @@ func (s *Server) callWithTimeout(ctx context.Context, method string, params inte
 		timeout = time.Until(deadline)
 	}
 
+	// Use time.NewTimer + Stop instead of time.After to avoid leaking
+	// the timer in the runtime when the response arrives or ctx is
+	// cancelled before the timeout fires.
+	timer := time.NewTimer(timeout)
 	select {
 	case result, ok := <-ch:
+		timer.Stop()
 		if !ok {
 			return nil, fmt.Errorf("mcp: connection closed")
 		}
 		if result == nil {
+			// Include the server's error code and message if available,
+			// instead of a generic "server returned error" with no detail.
+			s.pendMu.Lock()
+			errMsg := s.pendErrors[id]
+			delete(s.pendErrors, id)
+			s.pendMu.Unlock()
+			if errMsg != "" {
+				return nil, fmt.Errorf("mcp: server error: %s", errMsg)
+			}
 			return nil, fmt.Errorf("mcp: server returned error")
 		}
 		return result, nil
-	case <-time.After(timeout):
+	case <-timer.C:
 		s.pendMu.Lock()
 		delete(s.pending, id)
+		delete(s.pendErrors, id)
 		s.pendMu.Unlock()
 		return nil, fmt.Errorf("mcp: call %s timed out after %s", method, timeout)
 	case <-ctx.Done():
+		timer.Stop()
 		s.pendMu.Lock()
 		delete(s.pending, id)
+		delete(s.pendErrors, id)
 		s.pendMu.Unlock()
 		return nil, ctx.Err()
 	}

internal/permissions/guardian.go

@@ -256,9 +256,12 @@ func isBase64Injection(s string) bool {
 	if len(s) < minBase64Len {
 		return false
 	}
-	// Check if the line is mostly base64 characters (letters, digits, +, /, =)
+	// Count base64-legal bytes (all ASCII). Using byte iteration instead
+	// of rune iteration keeps the count consistent with len(s) (which is
+	// a byte count), so the ratio is correct for multi-byte UTF-8 input.
 	b64Chars := 0
-	for _, c := range s {
+	for i := 0; i < len(s); i++ {
+		c := s[i]
 		if (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '+' || c == '/' || c == '=' {
 			b64Chars++
 		}

internal/resilience/ratelimit/ratelimit.go

@@ -70,10 +70,12 @@ func (l *Limiter) Wait(ctx context.Context) error {
 		}
 		l.mu.Unlock()
 
+		timer := time.NewTimer(waitTime)
 		select {
 		case <-ctx.Done():
+			timer.Stop()
 			return ctx.Err()
-		case <-time.After(waitTime):
+		case <-timer.C:
 			// Try again
 		}
 	}