package yggdrasil // This is the session manager // It's responsible for keeping track of open sessions to other nodes // The session information consists of crypto keys and coords import ( "bytes" "errors" "sync" "time" "github.com/yggdrasil-network/yggdrasil-go/src/address" "github.com/yggdrasil-network/yggdrasil-go/src/crypto" "github.com/yggdrasil-network/yggdrasil-go/src/util" ) // All the information we know about an active session. // This includes coords, permanent and ephemeral keys, handles and nonces, various sorts of timing information for timeout and maintenance, and some metadata for the admin API. type sessionInfo struct { mutex sync.Mutex // Protects all of the below, use it any time you read/chance the contents of a session core *Core // reconfigure chan chan error // theirAddr address.Address // theirSubnet address.Subnet // theirPermPub crypto.BoxPubKey // theirSesPub crypto.BoxPubKey // mySesPub crypto.BoxPubKey // mySesPriv crypto.BoxPrivKey // sharedSesKey crypto.BoxSharedKey // derived from session keys theirHandle crypto.Handle // myHandle crypto.Handle // theirNonce crypto.BoxNonce // theirNonceMask uint64 // myNonce crypto.BoxNonce // theirMTU uint16 // myMTU uint16 // wasMTUFixed bool // Was the MTU fixed by a receive error? timeOpened time.Time // Time the sessino was opened time time.Time // Time we last received a packet mtuTime time.Time // time myMTU was last changed pingTime time.Time // time the first ping was sent since the last received packet pingSend time.Time // time the last ping was sent coords []byte // coords of destination reset bool // reset if coords change tstamp int64 // ATOMIC - tstamp from their last session ping, replay attack mitigation bytesSent uint64 // Bytes of real traffic sent in this session bytesRecvd uint64 // Bytes of real traffic received in this session init chan struct{} // Closed when the first session pong arrives, used to signal that the session is ready for initial use cancel util.Cancellation // Used to terminate workers fromRouter chan wire_trafficPacket // Received packets go here, to be decrypted by the session recv chan []byte // Decrypted packets go here, picked up by the associated Conn send chan FlowKeyMessage // Packets with optional flow key go here, to be encrypted and sent } func (sinfo *sessionInfo) doFunc(f func()) { sinfo.mutex.Lock() defer sinfo.mutex.Unlock() f() } // Represents a session ping/pong packet, andincludes information like public keys, a session handle, coords, a timestamp to prevent replays, and the tun/tap MTU. type sessionPing struct { SendPermPub crypto.BoxPubKey // Sender's permanent key Handle crypto.Handle // Random number to ID session SendSesPub crypto.BoxPubKey // Session key to use Coords []byte // Tstamp int64 // unix time, but the only real requirement is that it increases IsPong bool // MTU uint16 // } // Updates session info in response to a ping, after checking that the ping is OK. // Returns true if the session was updated, or false otherwise. func (s *sessionInfo) update(p *sessionPing) bool { if !(p.Tstamp > s.tstamp) { // To protect against replay attacks return false } if p.SendPermPub != s.theirPermPub { // Should only happen if two sessions got the same handle // That shouldn't be allowed anyway, but if it happens then let one time out return false } if p.SendSesPub != s.theirSesPub { s.theirSesPub = p.SendSesPub s.theirHandle = p.Handle s.sharedSesKey = *crypto.GetSharedKey(&s.mySesPriv, &s.theirSesPub) s.theirNonce = crypto.BoxNonce{} s.theirNonceMask = 0 } if p.MTU >= 1280 || p.MTU == 0 { s.theirMTU = p.MTU } if !bytes.Equal(s.coords, p.Coords) { // allocate enough space for additional coords s.coords = append(make([]byte, 0, len(p.Coords)+11), p.Coords...) } s.time = time.Now() s.tstamp = p.Tstamp s.reset = false defer func() { recover() }() // Recover if the below panics select { case <-s.init: default: // Unblock anything waiting for the session to initialize close(s.init) } return true } // Struct of all active sessions. // Sessions are indexed by handle. // Additionally, stores maps of address/subnet onto keys, and keys onto handles. type sessions struct { core *Core listener *Listener listenerMutex sync.Mutex reconfigure chan chan error lastCleanup time.Time isAllowedHandler func(pubkey *crypto.BoxPubKey, initiator bool) bool // Returns true or false if session setup is allowed isAllowedMutex sync.RWMutex // Protects the above permShared map[crypto.BoxPubKey]*crypto.BoxSharedKey // Maps known permanent keys to their shared key, used by DHT a lot sinfos map[crypto.Handle]*sessionInfo // Maps handle onto session info byTheirPerm map[crypto.BoxPubKey]*crypto.Handle // Maps theirPermPub onto handle } // Initializes the session struct. func (ss *sessions) init(core *Core) { ss.core = core ss.reconfigure = make(chan chan error, 1) go func() { for { e := <-ss.reconfigure responses := make(map[crypto.Handle]chan error) for index, session := range ss.sinfos { responses[index] = make(chan error) session.reconfigure <- responses[index] } for _, response := range responses { if err := <-response; err != nil { e <- err continue } } e <- nil } }() ss.permShared = make(map[crypto.BoxPubKey]*crypto.BoxSharedKey) ss.sinfos = make(map[crypto.Handle]*sessionInfo) ss.byTheirPerm = make(map[crypto.BoxPubKey]*crypto.Handle) ss.lastCleanup = time.Now() } // Determines whether the session with a given publickey is allowed based on // session firewall rules. func (ss *sessions) isSessionAllowed(pubkey *crypto.BoxPubKey, initiator bool) bool { ss.isAllowedMutex.RLock() defer ss.isAllowedMutex.RUnlock() if ss.isAllowedHandler == nil { return true } return ss.isAllowedHandler(pubkey, initiator) } // Gets the session corresponding to a given handle. func (ss *sessions) getSessionForHandle(handle *crypto.Handle) (*sessionInfo, bool) { sinfo, isIn := ss.sinfos[*handle] return sinfo, isIn } // Gets a session corresponding to a permanent key used by the remote node. func (ss *sessions) getByTheirPerm(key *crypto.BoxPubKey) (*sessionInfo, bool) { h, isIn := ss.byTheirPerm[*key] if !isIn { return nil, false } sinfo, isIn := ss.getSessionForHandle(h) return sinfo, isIn } // Creates a new session and lazily cleans up old existing sessions. This // includse initializing session info to sane defaults (e.g. lowest supported // MTU). func (ss *sessions) createSession(theirPermKey *crypto.BoxPubKey) *sessionInfo { // TODO: this check definitely needs to be moved if !ss.isSessionAllowed(theirPermKey, true) { return nil } sinfo := sessionInfo{} sinfo.core = ss.core sinfo.reconfigure = make(chan chan error, 1) sinfo.theirPermPub = *theirPermKey pub, priv := crypto.NewBoxKeys() sinfo.mySesPub = *pub sinfo.mySesPriv = *priv sinfo.myNonce = *crypto.NewBoxNonce() sinfo.theirMTU = 1280 ss.core.config.Mutex.RLock() sinfo.myMTU = uint16(ss.core.config.Current.IfMTU) ss.core.config.Mutex.RUnlock() now := time.Now() sinfo.timeOpened = now sinfo.time = now sinfo.mtuTime = now sinfo.pingTime = now sinfo.pingSend = now sinfo.init = make(chan struct{}) sinfo.cancel = util.NewCancellation() higher := false for idx := range ss.core.boxPub { if ss.core.boxPub[idx] > sinfo.theirPermPub[idx] { higher = true break } else if ss.core.boxPub[idx] < sinfo.theirPermPub[idx] { break } } if higher { // higher => odd nonce sinfo.myNonce[len(sinfo.myNonce)-1] |= 0x01 } else { // lower => even nonce sinfo.myNonce[len(sinfo.myNonce)-1] &= 0xfe } sinfo.myHandle = *crypto.NewHandle() sinfo.theirAddr = *address.AddrForNodeID(crypto.GetNodeID(&sinfo.theirPermPub)) sinfo.theirSubnet = *address.SubnetForNodeID(crypto.GetNodeID(&sinfo.theirPermPub)) sinfo.fromRouter = make(chan wire_trafficPacket, 1) sinfo.recv = make(chan []byte, 32) sinfo.send = make(chan FlowKeyMessage, 32) ss.sinfos[sinfo.myHandle] = &sinfo ss.byTheirPerm[sinfo.theirPermPub] = &sinfo.myHandle go func() { // Run cleanup when the session is canceled <-sinfo.cancel.Finished() sinfo.core.router.doAdmin(sinfo.close) }() return &sinfo } func (ss *sessions) cleanup() { // Time thresholds almost certainly could use some adjusting for k := range ss.permShared { // Delete a key, to make sure this eventually shrinks to 0 delete(ss.permShared, k) break } if time.Since(ss.lastCleanup) < time.Minute { return } permShared := make(map[crypto.BoxPubKey]*crypto.BoxSharedKey, len(ss.permShared)) for k, v := range ss.permShared { permShared[k] = v } ss.permShared = permShared sinfos := make(map[crypto.Handle]*sessionInfo, len(ss.sinfos)) for k, v := range ss.sinfos { sinfos[k] = v } ss.sinfos = sinfos byTheirPerm := make(map[crypto.BoxPubKey]*crypto.Handle, len(ss.byTheirPerm)) for k, v := range ss.byTheirPerm { byTheirPerm[k] = v } ss.byTheirPerm = byTheirPerm ss.lastCleanup = time.Now() } // Closes a session, removing it from sessions maps. func (sinfo *sessionInfo) close() { if s := sinfo.core.sessions.sinfos[sinfo.myHandle]; s == sinfo { delete(sinfo.core.sessions.sinfos, sinfo.myHandle) delete(sinfo.core.sessions.byTheirPerm, sinfo.theirPermPub) } } // Returns a session ping appropriate for the given session info. func (ss *sessions) getPing(sinfo *sessionInfo) sessionPing { loc := ss.core.switchTable.getLocator() coords := loc.getCoords() ref := sessionPing{ SendPermPub: ss.core.boxPub, Handle: sinfo.myHandle, SendSesPub: sinfo.mySesPub, Tstamp: time.Now().Unix(), Coords: coords, MTU: sinfo.myMTU, } sinfo.myNonce.Increment() return ref } // Gets the shared key for a pair of box keys. // Used to cache recently used shared keys for protocol traffic. // This comes up with dht req/res and session ping/pong traffic. func (ss *sessions) getSharedKey(myPriv *crypto.BoxPrivKey, theirPub *crypto.BoxPubKey) *crypto.BoxSharedKey { return crypto.GetSharedKey(myPriv, theirPub) // FIXME concurrency issues with the below, so for now we just burn the CPU every time if skey, isIn := ss.permShared[*theirPub]; isIn { return skey } // First do some cleanup const maxKeys = 1024 for key := range ss.permShared { // Remove a random key until the store is small enough if len(ss.permShared) < maxKeys { break } delete(ss.permShared, key) } ss.permShared[*theirPub] = crypto.GetSharedKey(myPriv, theirPub) return ss.permShared[*theirPub] } // Sends a session ping by calling sendPingPong in ping mode. func (ss *sessions) ping(sinfo *sessionInfo) { ss.sendPingPong(sinfo, false) } // Calls getPing, sets the appropriate ping/pong flag, encodes to wire format, and send it. // Updates the time the last ping was sent in the session info. func (ss *sessions) sendPingPong(sinfo *sessionInfo, isPong bool) { ping := ss.getPing(sinfo) ping.IsPong = isPong bs := ping.encode() shared := ss.getSharedKey(&ss.core.boxPriv, &sinfo.theirPermPub) payload, nonce := crypto.BoxSeal(shared, bs, nil) p := wire_protoTrafficPacket{ Coords: sinfo.coords, ToKey: sinfo.theirPermPub, FromKey: ss.core.boxPub, Nonce: *nonce, Payload: payload, } packet := p.encode() ss.core.router.out(packet) if sinfo.pingTime.Before(sinfo.time) { sinfo.pingTime = time.Now() } } // Handles a session ping, creating a session if needed and calling update, then possibly responding with a pong if the ping was in ping mode and the update was successful. // If the session has a packet cached (common when first setting up a session), it will be sent. func (ss *sessions) handlePing(ping *sessionPing) { // Get the corresponding session (or create a new session) sinfo, isIn := ss.getByTheirPerm(&ping.SendPermPub) // Check if the session is allowed // TODO: this check may need to be moved if !isIn && !ss.isSessionAllowed(&ping.SendPermPub, false) { return } // Create the session if it doesn't already exist if !isIn { ss.createSession(&ping.SendPermPub) sinfo, isIn = ss.getByTheirPerm(&ping.SendPermPub) if !isIn { panic("This should not happen") } ss.listenerMutex.Lock() // Check and see if there's a Listener waiting to accept connections // TODO: this should not block if nothing is accepting if !ping.IsPong && ss.listener != nil { conn := newConn(ss.core, crypto.GetNodeID(&sinfo.theirPermPub), &crypto.NodeID{}, sinfo) for i := range conn.nodeMask { conn.nodeMask[i] = 0xFF } conn.session.startWorkers() ss.listener.conn <- conn } ss.listenerMutex.Unlock() } sinfo.doFunc(func() { // Update the session if !sinfo.update(ping) { /*panic("Should not happen in testing")*/ return } if !ping.IsPong { ss.sendPingPong(sinfo, true) } }) } // Get the MTU of the session. // Will be equal to the smaller of this node's MTU or the remote node's MTU. // If sending over links with a maximum message size (this was a thing with the old UDP code), it could be further lowered, to a minimum of 1280. func (sinfo *sessionInfo) getMTU() uint16 { if sinfo.theirMTU == 0 || sinfo.myMTU == 0 { return 0 } if sinfo.theirMTU < sinfo.myMTU { return sinfo.theirMTU } return sinfo.myMTU } // Checks if a packet's nonce is recent enough to fall within the window of allowed packets, and not already received. func (sinfo *sessionInfo) nonceIsOK(theirNonce *crypto.BoxNonce) bool { // The bitmask is to allow for some non-duplicate out-of-order packets diff := theirNonce.Minus(&sinfo.theirNonce) if diff > 0 { return true } return ^sinfo.theirNonceMask&(0x01< 0 { // This nonce is newer, so shift the window before setting the bit, and update theirNonce in the session info. sinfo.theirNonceMask <<= uint64(diff) sinfo.theirNonceMask &= 0x01 sinfo.theirNonce = *theirNonce } else { // This nonce is older, so set the bit but do not shift the window. sinfo.theirNonceMask &= 0x01 << uint64(-diff) } } // Resets all sessions to an uninitialized state. // Called after coord changes, so attemtps to use a session will trigger a new ping and notify the remote end of the coord change. func (ss *sessions) reset() { for _, sinfo := range ss.sinfos { sinfo.doFunc(func() { sinfo.reset = true }) } } //////////////////////////////////////////////////////////////////////////////// //////////////////////////// Worker Functions Below //////////////////////////// //////////////////////////////////////////////////////////////////////////////// func (sinfo *sessionInfo) startWorkers() { go sinfo.recvWorker() go sinfo.sendWorker() } type FlowKeyMessage struct { FlowKey uint64 Message []byte } func (sinfo *sessionInfo) recvWorker() { // TODO move theirNonce etc into a struct that gets stored here, passed in over a channel // Since there's no reason for anywhere else in the session code to need to *read* it... // Only needs to be updated from the outside if a ping resets it... // That would get rid of the need to take a mutex for the sessionFunc var callbacks []chan func() doRecv := func(p wire_trafficPacket) { var bs []byte var err error var k crypto.BoxSharedKey sessionFunc := func() { if !sinfo.nonceIsOK(&p.Nonce) { err = ConnError{errors.New("packet dropped due to invalid nonce"), false, true, false, 0} return } k = sinfo.sharedSesKey } sinfo.doFunc(sessionFunc) if err != nil { util.PutBytes(p.Payload) return } var isOK bool ch := make(chan func(), 1) poolFunc := func() { bs, isOK = crypto.BoxOpen(&k, p.Payload, &p.Nonce) callback := func() { util.PutBytes(p.Payload) if !isOK { util.PutBytes(bs) return } sessionFunc = func() { if k != sinfo.sharedSesKey || !sinfo.nonceIsOK(&p.Nonce) { // The session updated in the mean time, so return an error err = ConnError{errors.New("session updated during crypto operation"), false, true, false, 0} return } sinfo.updateNonce(&p.Nonce) sinfo.time = time.Now() sinfo.bytesRecvd += uint64(len(bs)) } sinfo.doFunc(sessionFunc) if err != nil { // Not sure what else to do with this packet, I guess just drop it util.PutBytes(bs) } else { // Pass the packet to the buffer for Conn.Read select { case <-sinfo.cancel.Finished(): util.PutBytes(bs) case sinfo.recv <- bs: } } } ch <- callback } // Send to the worker and wait for it to finish util.WorkerGo(poolFunc) callbacks = append(callbacks, ch) } fromHelper := make(chan wire_trafficPacket, 1) go func() { var buf []wire_trafficPacket for { for len(buf) > 0 { select { case <-sinfo.cancel.Finished(): return case p := <-sinfo.fromRouter: buf = append(buf, p) for len(buf) > 64 { // Based on nonce window size util.PutBytes(buf[0].Payload) buf = buf[1:] } case fromHelper <- buf[0]: buf = buf[1:] } } select { case <-sinfo.cancel.Finished(): return case p := <-sinfo.fromRouter: buf = append(buf, p) } } }() for { for len(callbacks) > 0 { select { case f := <-callbacks[0]: callbacks = callbacks[1:] f() case <-sinfo.cancel.Finished(): return case p := <-fromHelper: doRecv(p) } } select { case <-sinfo.cancel.Finished(): return case p := <-fromHelper: doRecv(p) } } } func (sinfo *sessionInfo) sendWorker() { // TODO move info that this worker needs here, send updates via a channel // Otherwise we need to take a mutex to avoid races with update() var callbacks []chan func() doSend := func(msg FlowKeyMessage) { var p wire_trafficPacket var k crypto.BoxSharedKey sessionFunc := func() { sinfo.bytesSent += uint64(len(msg.Message)) p = wire_trafficPacket{ Coords: append([]byte(nil), sinfo.coords...), Handle: sinfo.theirHandle, Nonce: sinfo.myNonce, } if msg.FlowKey != 0 { // Helps ensure that traffic from this flow ends up in a separate queue from other flows // The zero padding relies on the fact that the self-peer is always on port 0 p.Coords = append(p.Coords, 0) p.Coords = wire_put_uint64(msg.FlowKey, p.Coords) } sinfo.myNonce.Increment() k = sinfo.sharedSesKey } // Get the mutex-protected info needed to encrypt the packet sinfo.doFunc(sessionFunc) ch := make(chan func(), 1) poolFunc := func() { // Encrypt the packet p.Payload, _ = crypto.BoxSeal(&k, msg.Message, &p.Nonce) // The callback will send the packet callback := func() { // Encoding may block on a util.GetBytes(), so kept out of the worker pool packet := p.encode() // Cleanup util.PutBytes(msg.Message) util.PutBytes(p.Payload) // Send the packet sinfo.core.router.out(packet) } ch <- callback } // Send to the worker and wait for it to finish util.WorkerGo(poolFunc) callbacks = append(callbacks, ch) } for { for len(callbacks) > 0 { select { case f := <-callbacks[0]: callbacks = callbacks[1:] f() case <-sinfo.cancel.Finished(): return case msg := <-sinfo.send: doSend(msg) } } select { case <-sinfo.cancel.Finished(): return case bs := <-sinfo.send: doSend(bs) } } }