clavitor/clavis/clavis-vault/api/middleware.go

package api

import (
	"context"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/johanj/clavitor/edition"
	"github.com/johanj/clavitor/lib"
)

// base64Decode handles both standard and url-safe base64 (with or without padding).
func base64Decode(s string) ([]byte, error) {
	s = strings.TrimRight(s, "=")
	b, err := base64.RawURLEncoding.DecodeString(s)
	if err != nil {
		b, err = base64.RawStdEncoding.DecodeString(s)
	}
	return b, err
}

func base64UrlEncode(b []byte) string {
	return base64.RawURLEncoding.EncodeToString(b)
}

type contextKey string

const (
	ctxActor    contextKey = "actor"
	ctxAgent    contextKey = "agent"
	ctxDB       contextKey = "db"
	ctxVaultKey contextKey = "vault_key"
)

func ActorFromContext(ctx context.Context) string {
	v, ok := ctx.Value(ctxActor).(string)
	if !ok {
		return lib.ActorWeb
	}
	return v
}

func AgentFromContext(ctx context.Context) *lib.AgentData {
	v, _ := ctx.Value(ctxAgent).(*lib.AgentData)
	return v
}

func DBFromContext(ctx context.Context) *lib.DB {
	v, _ := ctx.Value(ctxDB).(*lib.DB)
	return v
}

func VaultKeyFromContext(ctx context.Context) []byte {
	v, _ := ctx.Value(ctxVaultKey).([]byte)
	return v
}

// IsAgentRequest returns true if the request was made with a cvt_ agent token.
func IsAgentRequest(r *http.Request) bool {
	return AgentFromContext(r.Context()) != nil
}

// L1Middleware extracts L1 from Bearer token and opens the vault DB.
// Supports two token formats:
//   - cvt_ prefix: CVT wire token (type 0x00) — extract L0 for routing, L1 for encryption, agent_id for scope lookup
//   - raw base64: legacy L1 bearer (8 bytes) — vault owner, full access
func L1Middleware(dataDir string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			auth := r.Header.Get("Authorization")

			// No auth = unauthenticated request (registration, login, etc.)
			if auth == "" || !strings.HasPrefix(auth, "Bearer ") {
				matches, _ := filepath.Glob(filepath.Join(dataDir, "clavitor-*"))
				if len(matches) > 0 {
					db, err := lib.OpenDB(matches[0])
					if err == nil {
						defer db.Close()
						ctx := context.WithValue(r.Context(), ctxDB, db)
						next.ServeHTTP(w, r.WithContext(ctx))
						return
					}
				}
				next.ServeHTTP(w, r)
				return
			}

			bearerVal := strings.TrimPrefix(auth, "Bearer ")

			if strings.HasPrefix(bearerVal, "cvt_") {
				// --- CVT wire token ---
				l0, l1Raw, agentID, err := lib.ParseWireToken(bearerVal)
				if err != nil {
					ErrorResponse(w, http.StatusUnauthorized, "invalid_token", "Invalid CVT token")
					return
				}

				l1Key := lib.NormalizeKey(l1Raw)
				vaultPrefix := base64UrlEncode(l0)
				dbPath := filepath.Join(dataDir, "clavitor-"+vaultPrefix)

				db, err := lib.OpenDB(dbPath)
				if err != nil {
					ErrorResponse(w, http.StatusNotFound, "vault_not_found", "Vault not found")
					return
				}
				defer db.Close()

				// Look up agent by agent_id via blind index
				agentIDHex := hex.EncodeToString(agentID)
				agent, err := lib.AgentLookup(db, l1Key, agentIDHex)
				if err != nil {
					// Community: Log to stderr. Commercial: Also POSTs to telemetry endpoint.
					// This indicates DB corruption, decryption failure, or disk issues.
					edition.Current.AlertOperator(r.Context(), "auth_system_error",
						"Agent lookup failed (DB/decryption error)", map[string]any{"error": err.Error()})
					ErrorResponse(w, http.StatusInternalServerError, "system_error", "Authentication system error - contact support")
					return
				}
				if agent == nil {
					ErrorResponse(w, http.StatusUnauthorized, "unknown_agent", "Invalid or revoked token")
					return
				}

				clientIP := realIP(r)

				// IP whitelist: first contact fills it, subsequent requests checked
				if agent.AllowedIPs == "" {
					// First contact — record the IP
					//
					// SECURITY NOTE: There is a theoretical race condition here.
					// If two parallel requests from different IPs arrive simultaneously
					// for the same agent's first contact, both could pass the empty check
					// before either writes to the database.
					//
					// This was reviewed and accepted because:
					// 1. Requires a stolen agent token (already a compromise scenario)
					// 2. Requires two agents with the same token racing first contact
					// 3. The "loser" simply won't be auto-whitelisted (one IP wins)
					// 4. Cannot be reproduced in testing; practically impossible to trigger
					// 5. Per-vault SQLite isolation limits blast radius
					//
					// The fix would require plaintext allowed_ips column + atomic conditional
					// update. Not worth the complexity for this edge case.
					agent.AllowedIPs = clientIP
					if err := lib.AgentUpdateAllowedIPs(db, l1Key, agent); err != nil {
						log.Printf("agent %s: failed to record first-contact IP: %v", agent.Name, err)
						ErrorResponse(w, http.StatusInternalServerError, "ip_record_failed", "Failed to record agent IP")
						return
					}
					log.Printf("agent %s: first contact from %s, IP recorded", agent.Name, clientIP)
				} else if !lib.AgentIPAllowed(agent, clientIP) {
					log.Printf("agent %s: blocked IP %s (allowed: %s)", agent.Name, clientIP, agent.AllowedIPs)
					ErrorResponse(w, http.StatusForbidden, "ip_blocked", "IP not allowed for this agent")
					return
				}

				// Per-agent rate limiting
				if agent.RateLimit > 0 {
					if !agentRateLimiter.allow(agent.AgentID, agent.RateLimit) {
						ErrorResponse(w, http.StatusTooManyRequests, "rate_limited", "Agent rate limit exceeded")
						return
					}
				}

				ctx := context.WithValue(r.Context(), ctxDB, db)
				ctx = context.WithValue(ctx, ctxVaultKey, l1Key)
				ctx = context.WithValue(ctx, ctxActor, lib.ActorAgent)
				ctx = context.WithValue(ctx, ctxAgent, agent)
				next.ServeHTTP(w, r.WithContext(ctx))

			} else {
				// --- Legacy L1 bearer (web UI / extension) ---
				l1Raw, err := base64Decode(bearerVal)
				if err != nil || len(l1Raw) != 8 {
					ErrorResponse(w, http.StatusUnauthorized, "invalid_l1", "Invalid L1 key in Bearer")
					return
				}

				l1Key := lib.NormalizeKey(l1Raw)
				vaultPrefix := base64UrlEncode(l1Raw[:4])
				dbPath := filepath.Join(dataDir, "clavitor-"+vaultPrefix)

				var db *lib.DB
				if _, err := os.Stat(dbPath); err == nil {
					db, err = lib.OpenDB(dbPath)
					if err != nil {
						ErrorResponse(w, http.StatusInternalServerError, "db_error", "Failed to open vault")
						return
					}
				}
				if db == nil {
					ErrorResponse(w, http.StatusNotFound, "vault_not_found", "Vault not found")
					return
				}
				defer db.Close()

				ctx := context.WithValue(r.Context(), ctxDB, db)
				ctx = context.WithValue(ctx, ctxVaultKey, l1Key)
				ctx = context.WithValue(ctx, ctxActor, lib.ActorWeb)
				next.ServeHTTP(w, r.WithContext(ctx))
			}
		})
	}
}

// LoggingMiddleware logs HTTP requests.
func LoggingMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		wrapped := &statusWriter{ResponseWriter: w, status: 200}
		next.ServeHTTP(wrapped, r)
		log.Printf("%s %s %d %s", r.Method, r.URL.Path, wrapped.status, time.Since(start))
	})
}

type statusWriter struct {
	http.ResponseWriter
	status int
}

func (w *statusWriter) WriteHeader(code int) {
	w.status = code
	w.ResponseWriter.WriteHeader(code)
}

// RateLimitMiddleware implements per-IP rate limiting.
func RateLimitMiddleware(requestsPerMinute int) func(http.Handler) http.Handler {
	var mu sync.Mutex
	clients := make(map[string]*rateLimitEntry)

	go func() {
		for {
			time.Sleep(time.Minute)
			mu.Lock()
			now := time.Now()
			for ip, entry := range clients {
				if now.Sub(entry.windowStart) > time.Minute {
					delete(clients, ip)
				}
			}
			mu.Unlock()
		}
	}()

	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ip := realIP(r)
			mu.Lock()
			entry, exists := clients[ip]
			now := time.Now()
			if !exists || now.Sub(entry.windowStart) > time.Minute {
				entry = &rateLimitEntry{windowStart: now, count: 0}
				clients[ip] = entry
			}
			entry.count++
			count := entry.count
			mu.Unlock()

			if count > requestsPerMinute {
				ErrorResponse(w, http.StatusTooManyRequests, "rate_limited", "Too many requests")
				return
			}
			next.ServeHTTP(w, r)
		})
	}
}

type rateLimitEntry struct {
	windowStart time.Time
	count       int
}

// Per-agent rate limiter (keyed by agent ID, not IP).
var agentRateLimiter = newAgentLimiter()

type agentLimiter struct {
	mu     sync.Mutex
	agents map[string]*rateLimitEntry
}

func newAgentLimiter() *agentLimiter {
	al := &agentLimiter{agents: make(map[string]*rateLimitEntry)}
	go func() {
		for {
			time.Sleep(time.Minute)
			al.mu.Lock()
			now := time.Now()
			for id, e := range al.agents {
				if now.Sub(e.windowStart) > time.Minute {
					delete(al.agents, id)
				}
			}
			al.mu.Unlock()
		}
	}()
	return al
}

func (al *agentLimiter) allow(agentID string, maxPerMinute int) bool {
	al.mu.Lock()
	defer al.mu.Unlock()
	now := time.Now()
	e, exists := al.agents[agentID]
	if !exists || now.Sub(e.windowStart) > time.Minute {
		e = &rateLimitEntry{windowStart: now, count: 0}
		al.agents[agentID] = e
	}
	e.count++
	return e.count <= maxPerMinute
}

// CORSMiddleware handles CORS headers.
func CORSMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		origin := r.Header.Get("Origin")
		if origin != "" && (strings.Contains(origin, "localhost") || strings.Contains(origin, "127.0.0.1")) {
			w.Header().Set("Access-Control-Allow-Origin", origin)
			w.Header().Set("Vary", "Origin")
		}
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type")
		w.Header().Set("Access-Control-Max-Age", "86400")
		if r.Method == "OPTIONS" {
			w.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(w, r)
	})
}

// SecurityHeadersMiddleware adds security headers.
func SecurityHeadersMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-XSS-Protection", "1; mode=block")
		w.Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")
		// CSP: removed unused tailwindcss, tightened img-src to self+data only
		w.Header().Set("Content-Security-Policy", "default-src 'self'; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src 'self' data: https://fonts.gstatic.com; img-src 'self' data:; connect-src 'self' localhost 127.0.0.1 https://clavitor.ai")
		next.ServeHTTP(w, r)
	})
}

// MaxBodySizeMiddleware limits request body size and rejects binary content.
// Allows 64KB max for markdown notes. Rejects binary data (images, executables, etc).
func MaxBodySizeMiddleware(maxBytes int64) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			// Security: Reject binary content types
			contentType := r.Header.Get("Content-Type")
			if isBinaryContentType(contentType) {
				ErrorResponse(w, http.StatusUnsupportedMediaType, "binary_not_allowed",
					"Binary content not allowed. Only text/markdown data accepted.")
				return
			}
			r.Body = http.MaxBytesReader(w, r.Body, maxBytes)
			next.ServeHTTP(w, r)
		})
	}
}

// isBinaryContentType detects common binary content types.
func isBinaryContentType(ct string) bool {
	ct = strings.ToLower(ct)
	binaryTypes := []string{
		"image/", "audio/", "video/", "application/pdf",
		"application/zip", "application/gzip", "application/octet-stream",
		"application/x-executable", "application/x-dosexec",
		"multipart/form-data", // usually file uploads
	}
	for _, bt := range binaryTypes {
		if strings.Contains(ct, bt) {
			return true
		}
	}
	return false
}

// ErrorResponse sends a JSON error response.
func ErrorResponse(w http.ResponseWriter, status int, code, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(map[string]string{"error": message, "code": code})
}

// JSONResponse sends a JSON success response.
func JSONResponse(w http.ResponseWriter, status int, data any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(data)
}

// tarpitHandler wastes scanner resources.
var tarpitSem = make(chan struct{}, 1000)

func tarpitHandler(w http.ResponseWriter, r *http.Request) {
	select {
	case tarpitSem <- struct{}{}:
		defer func() { <-tarpitSem }()
	default:
		if hj, ok := w.(http.Hijacker); ok {
			conn, _, err := hj.Hijack()
			if err == nil {
				conn.Close()
			}
		}
		return
	}
	log.Printf("tarpit: %s %s from %s", r.Method, r.URL.Path, realIP(r))
	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(200)
	flusher, canFlush := w.(http.Flusher)
	for i := 0; i < 30; i++ {
		_, err := w.Write([]byte(" "))
		if err != nil {
			return
		}
		if canFlush {
			flusher.Flush()
		}
		time.Sleep(time.Second)
	}
}

func realIP(r *http.Request) string {
	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
		parts := strings.SplitN(xff, ",", 2)
		return strings.TrimSpace(parts[0])
	}
	if xri := r.Header.Get("X-Real-IP"); xri != "" {
		return xri
	}
	addr := r.RemoteAddr
	if idx := strings.LastIndex(addr, ":"); idx != -1 {
		return addr[:idx]
	}
	return addr
}