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 "time" // 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 { core *Core theirAddr address theirSubnet subnet theirPermPub boxPubKey theirSesPub boxPubKey mySesPub boxPubKey mySesPriv boxPrivKey sharedSesKey boxSharedKey // derived from session keys theirHandle handle myHandle handle theirNonce boxNonce myNonce boxNonce theirMTU uint16 myMTU uint16 wasMTUFixed bool // Was the MTU fixed by a receive error? time time.Time // Time we last received a packet coords []byte // coords of destination packet []byte // a buffered packet, sent immediately on ping/pong init bool // Reset if coords change send chan []byte recv chan *wire_trafficPacket nonceMask uint64 tstamp int64 // tstamp from their last session ping, replay attack mitigation 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 bytesSent uint64 // Bytes of real traffic sent in this session bytesRecvd uint64 // Bytes of real traffic received in this session } // 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 boxPubKey // Sender's permanent key Handle handle // Random number to ID session SendSesPub 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 = *getSharedKey(&s.mySesPriv, &s.theirSesPub) s.theirNonce = boxNonce{} s.nonceMask = 0 } if p.MTU >= 1280 || p.MTU == 0 { s.theirMTU = p.MTU } s.coords = append([]byte{}, p.Coords...) now := time.Now() s.time = now s.tstamp = p.Tstamp s.init = true return true } // Returns true if the session has been idle for longer than the allowed timeout. func (s *sessionInfo) timedout() bool { return time.Since(s.time) > time.Minute } // 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 // Maps known permanent keys to their shared key, used by DHT a lot permShared map[boxPubKey]*boxSharedKey // Maps (secret) handle onto session info sinfos map[handle]*sessionInfo // Maps mySesPub onto handle byMySes map[boxPubKey]*handle // Maps theirPermPub onto handle byTheirPerm map[boxPubKey]*handle addrToPerm map[address]*boxPubKey subnetToPerm map[subnet]*boxPubKey } // Initializes the session struct. func (ss *sessions) init(core *Core) { ss.core = core ss.permShared = make(map[boxPubKey]*boxSharedKey) ss.sinfos = make(map[handle]*sessionInfo) ss.byMySes = make(map[boxPubKey]*handle) ss.byTheirPerm = make(map[boxPubKey]*handle) ss.addrToPerm = make(map[address]*boxPubKey) ss.subnetToPerm = make(map[subnet]*boxPubKey) } // Gets the session corresponding to a given handle. func (ss *sessions) getSessionForHandle(handle *handle) (*sessionInfo, bool) { sinfo, isIn := ss.sinfos[*handle] if isIn && sinfo.timedout() { // We have a session, but it has timed out return nil, false } return sinfo, isIn } // Gets a session corresponding to an ephemeral session key used by this node. func (ss *sessions) getByMySes(key *boxPubKey) (*sessionInfo, bool) { h, isIn := ss.byMySes[*key] if !isIn { return nil, false } sinfo, isIn := ss.getSessionForHandle(h) return sinfo, isIn } // Gets a session corresponding to a permanent key used by the remote node. func (ss *sessions) getByTheirPerm(key *boxPubKey) (*sessionInfo, bool) { h, isIn := ss.byTheirPerm[*key] if !isIn { return nil, false } sinfo, isIn := ss.getSessionForHandle(h) return sinfo, isIn } // Gets a session corresponding to an IPv6 address used by the remote node. func (ss *sessions) getByTheirAddr(addr *address) (*sessionInfo, bool) { p, isIn := ss.addrToPerm[*addr] if !isIn { return nil, false } sinfo, isIn := ss.getByTheirPerm(p) return sinfo, isIn } // Gets a session corresponding to an IPv6 /64 subnet used by the remote node/network. func (ss *sessions) getByTheirSubnet(snet *subnet) (*sessionInfo, bool) { p, isIn := ss.subnetToPerm[*snet] if !isIn { return nil, false } sinfo, isIn := ss.getByTheirPerm(p) return sinfo, isIn } // Creates a new session and lazily cleans up old/timedout existing sessions. // This includse initializing session info to sane defaults (e.g. lowest supported MTU). func (ss *sessions) createSession(theirPermKey *boxPubKey) *sessionInfo { sinfo := sessionInfo{} sinfo.core = ss.core sinfo.theirPermPub = *theirPermKey pub, priv := newBoxKeys() sinfo.mySesPub = *pub sinfo.mySesPriv = *priv sinfo.myNonce = *newBoxNonce() sinfo.theirMTU = 1280 sinfo.myMTU = uint16(ss.core.tun.mtu) now := time.Now() sinfo.time = now sinfo.mtuTime = now sinfo.pingTime = now sinfo.pingSend = now 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 = *newHandle() sinfo.theirAddr = *address_addrForNodeID(getNodeID(&sinfo.theirPermPub)) sinfo.theirSubnet = *address_subnetForNodeID(getNodeID(&sinfo.theirPermPub)) sinfo.send = make(chan []byte, 32) sinfo.recv = make(chan *wire_trafficPacket, 32) go sinfo.doWorker() // Do some cleanup // Time thresholds almost certainly could use some adjusting for _, s := range ss.sinfos { if s.timedout() { s.close() } } ss.sinfos[sinfo.myHandle] = &sinfo ss.byMySes[sinfo.mySesPub] = &sinfo.myHandle ss.byTheirPerm[sinfo.theirPermPub] = &sinfo.myHandle ss.addrToPerm[sinfo.theirAddr] = &sinfo.theirPermPub ss.subnetToPerm[sinfo.theirSubnet] = &sinfo.theirPermPub return &sinfo } // Closes a session, removing it from sessions maps and killing the worker goroutine. func (sinfo *sessionInfo) close() { delete(sinfo.core.sessions.sinfos, sinfo.myHandle) delete(sinfo.core.sessions.byMySes, sinfo.mySesPub) delete(sinfo.core.sessions.byTheirPerm, sinfo.theirPermPub) delete(sinfo.core.sessions.addrToPerm, sinfo.theirAddr) delete(sinfo.core.sessions.subnetToPerm, sinfo.theirSubnet) close(sinfo.send) close(sinfo.recv) } // 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.update() 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 *boxPrivKey, theirPub *boxPubKey) *boxSharedKey { if skey, isIn := ss.permShared[*theirPub]; isIn { return skey } // First do some cleanup const maxKeys = dht_bucket_number * dht_bucket_size 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] = 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 := 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 !isPong { sinfo.pingSend = 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) if !isIn || sinfo.timedout() { if isIn { sinfo.close() } ss.createSession(&ping.SendPermPub) sinfo, isIn = ss.getByTheirPerm(&ping.SendPermPub) if !isIn { panic("This should not happen") } } // Update the session if !sinfo.update(ping) { /*panic("Should not happen in testing")*/ return } if !ping.IsPong { ss.sendPingPong(sinfo, true) } if sinfo.packet != nil { // send var bs []byte bs, sinfo.packet = sinfo.packet, nil ss.core.router.sendPacket(bs) } } // Used to subtract one nonce from another, staying in the range +- 64. // This is used by the nonce progression machinery to advance the bitmask of recently received packets (indexed by nonce), or to check the appropriate bit of the bitmask. // It's basically part of the machinery that prevents replays and duplicate packets. func (n *boxNonce) minus(m *boxNonce) int64 { diff := int64(0) for idx := range n { diff *= 256 diff += int64(n[idx]) - int64(m[idx]) if diff > 64 { diff = 64 } if diff < -64 { diff = -64 } } return diff } // 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 *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.nonceMask&(0x01< 0 { // This nonce is newer, so shift the window before setting the bit, and update theirNonce in the session info. sinfo.nonceMask <<= uint64(diff) sinfo.nonceMask &= 0x01 sinfo.theirNonce = *theirNonce } else { // This nonce is older, so set the bit but do not shift the window. sinfo.nonceMask &= 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) resetInits() { for _, sinfo := range ss.sinfos { sinfo.init = false } } //////////////////////////////////////////////////////////////////////////////// // This is for a per-session worker. // It handles calling the relatively expensive crypto operations. // It's also responsible for checking nonces and dropping out-of-date/duplicate packets, or else calling the function to update nonces if the packet is OK. func (sinfo *sessionInfo) doWorker() { for { select { case p, ok := <-sinfo.recv: if ok { sinfo.doRecv(p) } else { return } case bs, ok := <-sinfo.send: if ok { sinfo.doSend(bs) } else { return } } } } // This encrypts a packet, creates a trafficPacket struct, encodes it, and sends it to router.out to pass it to the switch layer. func (sinfo *sessionInfo) doSend(bs []byte) { defer util_putBytes(bs) if !sinfo.init { return } // To prevent using empty session keys payload, nonce := boxSeal(&sinfo.sharedSesKey, bs, &sinfo.myNonce) defer util_putBytes(payload) p := wire_trafficPacket{ Coords: sinfo.coords, Handle: sinfo.theirHandle, Nonce: *nonce, Payload: payload, } packet := p.encode() sinfo.bytesSent += uint64(len(bs)) sinfo.core.router.out(packet) } // This takes a trafficPacket and checks the nonce. // If the nonce is OK, it decrypts the packet. // If the decrypted packet is OK, it calls router.recvPacket to pass the packet to the tun/tap. // If a packet does not decrypt successfully, it assumes the packet was truncated, and updates the MTU accordingly. // TODO? remove the MTU updating part? That should never happen with TCP peers, and the old UDP code that caused it was removed (and if replaced, should be replaced with something that can reliably send messages with an arbitrary size). func (sinfo *sessionInfo) doRecv(p *wire_trafficPacket) { defer util_putBytes(p.Payload) payloadSize := uint16(len(p.Payload)) if !sinfo.nonceIsOK(&p.Nonce) { return } bs, isOK := boxOpen(&sinfo.sharedSesKey, p.Payload, &p.Nonce) if !isOK { // We're going to guess that the session MTU is too large // Set myMTU to the largest value we think we can receive fixSessionMTU := func() { // This clamps down to 1280 almost immediately over ipv4 // Over link-local ipv6, it seems to approach link MTU // So maybe it's doing the right thing?... //sinfo.core.log.Println("DEBUG got bad packet:", payloadSize) newMTU := payloadSize - boxOverhead if newMTU < 1280 { newMTU = 1280 } if newMTU < sinfo.myMTU { sinfo.myMTU = newMTU //sinfo.core.log.Println("DEBUG set MTU to:", sinfo.myMTU) sinfo.core.sessions.sendPingPong(sinfo, false) sinfo.mtuTime = time.Now() sinfo.wasMTUFixed = true } } go func() { sinfo.core.router.admin <- fixSessionMTU }() util_putBytes(bs) return } fixSessionMTU := func() { if time.Since(sinfo.mtuTime) > time.Minute { sinfo.myMTU = uint16(sinfo.core.tun.mtu) sinfo.mtuTime = time.Now() //sinfo.core.log.Println("DEBUG: Reset MTU to:", sinfo.myMTU) } } go func() { sinfo.core.router.admin <- fixSessionMTU }() sinfo.updateNonce(&p.Nonce) sinfo.time = time.Now() sinfo.bytesRecvd += uint64(len(bs)) sinfo.core.router.recvPacket(bs, &sinfo.theirAddr, &sinfo.theirSubnet) }