1 files changed, 224 insertions, 0 deletions
diff --git a/lib/agent/session.go b/lib/agent/session.go
new file mode 100644
index 0000000..e50abe1
--- /dev/null
+++ b/lib/agent/session.go
@@ -0,0 +1,224 @@
+package agent
+
+import (
+	"encoding/base64"
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/googollee/go-socket.io"
+	uuid "github.com/satori/go.uuid"
+	"github.com/syncthing/syncthing/lib/sync"
+)
+
+const sessionCookieName = "xds-agent-sid"
+const sessionHeaderName = "XDS-AGENT-SID"
+
+const sessionMonitorTime = 10 // Time (in seconds) to schedule monitoring session tasks
+
+const initSessionMaxAge = 10 // Initial session max age in seconds
+const maxSessions = 100000   // Maximum number of sessions in sessMap map
+
+const secureCookie = false // TODO: see https://github.com/astaxie/beego/blob/master/session/session.go#L218
+
+// ClientSession contains the info of a user/client session
+type ClientSession struct {
+	ID       string
+	WSID     string // only one WebSocket per client/session
+	MaxAge   int64
+	IOSocket *socketio.Socket
+
+	// private
+	expireAt time.Time
+	useCount int64
+}
+
+// Sessions holds client sessions
+type Sessions struct {
+	*Context
+	cookieMaxAge int64
+	sessMap      map[string]ClientSession
+	mutex        sync.Mutex
+	stop         chan struct{} // signals intentional stop
+}
+
+// NewClientSessions .
+func NewClientSessions(ctx *Context, cookieMaxAge string) *Sessions {
+	ckMaxAge, err := strconv.ParseInt(cookieMaxAge, 10, 0)
+	if err != nil {
+		ckMaxAge = 0
+	}
+	s := Sessions{
+		Context:      ctx,
+		cookieMaxAge: ckMaxAge,
+		sessMap:      make(map[string]ClientSession),
+		mutex:        sync.NewMutex(),
+		stop:         make(chan struct{}),
+	}
+	s.webServer.router.Use(s.Middleware())
+
+	// Start monitoring of sessions Map (use to manage expiration and cleanup)
+	go s.monitorSessMap()
+
+	return &s
+}
+
+// Stop sessions management
+func (s *Sessions) Stop() {
+	close(s.stop)
+}
+
+// Middleware is used to managed session
+func (s *Sessions) Middleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// FIXME Add CSRF management
+
+		// Get session
+		sess := s.Get(c)
+		if sess == nil {
+			// Allocate a new session key and put in cookie
+			sess = s.newSession("")
+		} else {
+			s.refresh(sess.ID)
+		}
+
+		// Set session in cookie and in header
+		// Do not set Domain to localhost (http://stackoverflow.com/questions/1134290/cookies-on-localhost-with-explicit-domain)
+		c.SetCookie(sessionCookieName, sess.ID, int(sess.MaxAge), "/", "",
+			secureCookie, false)
+		c.Header(sessionHeaderName, sess.ID)
+
+		// Save session id in gin metadata
+		c.Set(sessionCookieName, sess.ID)
+
+		c.Next()
+	}
+}
+
+// Get returns the client session for a specific ID
+func (s *Sessions) Get(c *gin.Context) *ClientSession {
+	var sid string
+
+	// First get from gin metadata
+	v, exist := c.Get(sessionCookieName)
+	if v != nil {
+		sid = v.(string)
+	}
+
+	// Then look in cookie
+	if !exist || sid == "" {
+		sid, _ = c.Cookie(sessionCookieName)
+	}
+
+	// Then look in Header
+	if sid == "" {
+		sid = c.Request.Header.Get(sessionCookieName)
+	}
+	if sid != "" {
+		s.mutex.Lock()
+		defer s.mutex.Unlock()
+		if key, ok := s.sessMap[sid]; ok {
+			// TODO: return a copy ???
+			return &key
+		}
+	}
+	return nil
+}
+
+// IOSocketGet Get socketio definition from sid
+func (s *Sessions) IOSocketGet(sid string) *socketio.Socket {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	sess, ok := s.sessMap[sid]
+	if ok {
+		return sess.IOSocket
+	}
+	return nil
+}
+
+// UpdateIOSocket updates the IO Socket definition for of a session
+func (s *Sessions) UpdateIOSocket(sid string, so *socketio.Socket) error {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	if _, ok := s.sessMap[sid]; ok {
+		sess := s.sessMap[sid]
+		if so == nil {
+			// Could be the case when socketio is closed/disconnected
+			sess.WSID = ""
+		} else {
+			sess.WSID = (*so).Id()
+		}
+		sess.IOSocket = so
+		s.sessMap[sid] = sess
+	}
+	return nil
+}
+
+// nesSession Allocate a new client session
+func (s *Sessions) newSession(prefix string) *ClientSession {
+	uuid := prefix + uuid.NewV4().String()
+	id := base64.URLEncoding.EncodeToString([]byte(uuid))
+	se := ClientSession{
+		ID:       id,
+		WSID:     "",
+		MaxAge:   initSessionMaxAge,
+		IOSocket: nil,
+		expireAt: time.Now().Add(time.Duration(initSessionMaxAge) * time.Second),
+		useCount: 0,
+	}
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	s.sessMap[se.ID] = se
+
+	s.Log.Debugf("NEW session (%d): %s", len(s.sessMap), id)
+	return &se
+}
+
+// refresh Move this session ID to the head of the list
+func (s *Sessions) refresh(sid string) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	sess := s.sessMap[sid]
+	sess.useCount++
+	if sess.MaxAge < s.cookieMaxAge && sess.useCount > 1 {
+		sess.MaxAge = s.cookieMaxAge
+		sess.expireAt = time.Now().Add(time.Duration(sess.MaxAge) * time.Second)
+	}
+
+	// TODO - Add flood detection (like limit_req of nginx)
+	// (delayed request when to much requests in a short period of time)
+
+	s.sessMap[sid] = sess
+}
+
+func (s *Sessions) monitorSessMap() {
+	const dbgFullTrace = false // for debugging
+
+	for {
+		select {
+		case <-s.stop:
+			s.Log.Debugln("Stop monitorSessMap")
+			return
+		case <-time.After(sessionMonitorTime * time.Second):
+			if dbgFullTrace {
+				s.Log.Debugf("Sessions Map size: %d", len(s.sessMap))
+				s.Log.Debugf("Sessions Map : %v", s.sessMap)
+			}
+
+			if len(s.sessMap) > maxSessions {
+				s.Log.Errorln("TOO MUCH sessions, cleanup old ones !")
+			}
+
+			s.mutex.Lock()
+			for _, ss := range s.sessMap {
+				if ss.expireAt.Sub(time.Now()) < 0 {
+					//SEB DEBUG s.Log.Debugf("Delete expired session id: %s", ss.ID)
+					delete(s.sessMap, ss.ID)
+				}
+			}
+			s.mutex.Unlock()
+		}
+	}
+}