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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
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import (
"bytes"
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"encoding/hex"
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"time"
)
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// 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.
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type sessionInfo struct {
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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
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theirMTU uint16
myMTU uint16
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wasMTUFixed bool // Was the MTU fixed by a receive error?
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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
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tstamp int64 // tstamp from their last session ping, replay attack mitigation
mtuTime time . Time // time myMTU was last changed
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pingTime time . Time // time the first ping was sent since the last received packet
pingSend time . Time // time the last ping was sent
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bytesSent uint64 // Bytes of real traffic sent in this session
bytesRecvd uint64 // Bytes of real traffic received in this session
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}
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// 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.
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type sessionPing struct {
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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
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}
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// 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.
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func ( s * sessionInfo ) update ( p * sessionPing ) bool {
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if ! ( p . Tstamp > s . tstamp ) {
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// To protect against replay attacks
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return false
}
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if p . SendPermPub != s . theirPermPub {
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// 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
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return false
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}
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if p . SendSesPub != s . theirSesPub {
s . theirSesPub = p . SendSesPub
s . theirHandle = p . Handle
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s . sharedSesKey = * getSharedKey ( & s . mySesPriv , & s . theirSesPub )
s . theirNonce = boxNonce { }
s . nonceMask = 0
}
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if p . MTU >= 1280 || p . MTU == 0 {
s . theirMTU = p . MTU
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}
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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 ... )
}
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now := time . Now ( )
s . time = now
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s . tstamp = p . Tstamp
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s . init = true
return true
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}
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// Returns true if the session has been idle for longer than the allowed timeout.
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func ( s * sessionInfo ) timedout ( ) bool {
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return time . Since ( s . time ) > time . Minute
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}
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// Struct of all active sessions.
// Sessions are indexed by handle.
// Additionally, stores maps of address/subnet onto keys, and keys onto handles.
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type sessions struct {
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core * Core
lastCleanup time . Time
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// 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
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// Options from the session firewall
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sessionFirewallEnabled bool
sessionFirewallAllowsDirect bool
sessionFirewallAllowsRemote bool
sessionFirewallAlwaysAllowsOutbound bool
sessionFirewallWhitelist [ ] string
sessionFirewallBlacklist [ ] string
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}
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// Initializes the session struct.
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func ( ss * sessions ) init ( core * Core ) {
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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 )
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ss . lastCleanup = time . Now ( )
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}
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// Enable or disable the session firewall
func ( ss * sessions ) setSessionFirewallState ( enabled bool ) {
ss . sessionFirewallEnabled = enabled
}
// Set the session firewall defaults (first parameter is whether to allow
// sessions from direct peers, second is whether to allow from remote nodes).
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func ( ss * sessions ) setSessionFirewallDefaults ( allowsDirect bool , allowsRemote bool , alwaysAllowsOutbound bool ) {
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ss . sessionFirewallAllowsDirect = allowsDirect
ss . sessionFirewallAllowsRemote = allowsRemote
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ss . sessionFirewallAlwaysAllowsOutbound = alwaysAllowsOutbound
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}
// Set the session firewall whitelist - nodes always allowed to open sessions.
func ( ss * sessions ) setSessionFirewallWhitelist ( whitelist [ ] string ) {
ss . sessionFirewallWhitelist = whitelist
}
// Set the session firewall blacklist - nodes never allowed to open sessions.
func ( ss * sessions ) setSessionFirewallBlacklist ( blacklist [ ] string ) {
ss . sessionFirewallBlacklist = blacklist
}
// Determines whether the session with a given publickey is allowed based on
// session firewall rules.
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func ( ss * sessions ) isSessionAllowed ( pubkey * boxPubKey , initiator bool ) bool {
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// Allow by default if the session firewall is disabled
if ! ss . sessionFirewallEnabled {
return true
}
// Prepare for checking whitelist/blacklist
var box boxPubKey
// Reject blacklisted nodes
for _ , b := range ss . sessionFirewallBlacklist {
key , err := hex . DecodeString ( b )
if err == nil {
copy ( box [ : boxPubKeyLen ] , key )
if box == * pubkey {
return false
}
}
}
// Allow whitelisted nodes
for _ , b := range ss . sessionFirewallWhitelist {
key , err := hex . DecodeString ( b )
if err == nil {
copy ( box [ : boxPubKeyLen ] , key )
if box == * pubkey {
return true
}
}
}
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// Allow outbound sessions if appropriate
if ss . sessionFirewallAlwaysAllowsOutbound {
if initiator {
return true
}
}
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// Look and see if the pubkey is that of a direct peer
var isDirectPeer bool
for _ , peer := range ss . core . peers . ports . Load ( ) . ( map [ switchPort ] * peer ) {
if peer . box == * pubkey {
isDirectPeer = true
break
}
}
// Allow direct peers if appropriate
if ss . sessionFirewallAllowsDirect && isDirectPeer {
return true
}
// Allow remote nodes if appropriate
if ss . sessionFirewallAllowsRemote && ! isDirectPeer {
return true
}
// Finally, default-deny if not matching any of the above rules
return false
}
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// Gets the session corresponding to a given handle.
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func ( ss * sessions ) getSessionForHandle ( handle * handle ) ( * sessionInfo , bool ) {
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sinfo , isIn := ss . sinfos [ * handle ]
if isIn && sinfo . timedout ( ) {
// We have a session, but it has timed out
return nil , false
}
return sinfo , isIn
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}
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// Gets a session corresponding to an ephemeral session key used by this node.
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func ( ss * sessions ) getByMySes ( key * boxPubKey ) ( * sessionInfo , bool ) {
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h , isIn := ss . byMySes [ * key ]
if ! isIn {
return nil , false
}
sinfo , isIn := ss . getSessionForHandle ( h )
return sinfo , isIn
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}
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// Gets a session corresponding to a permanent key used by the remote node.
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func ( ss * sessions ) getByTheirPerm ( key * boxPubKey ) ( * sessionInfo , bool ) {
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h , isIn := ss . byTheirPerm [ * key ]
if ! isIn {
return nil , false
}
sinfo , isIn := ss . getSessionForHandle ( h )
return sinfo , isIn
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}
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// Gets a session corresponding to an IPv6 address used by the remote node.
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func ( ss * sessions ) getByTheirAddr ( addr * address ) ( * sessionInfo , bool ) {
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p , isIn := ss . addrToPerm [ * addr ]
if ! isIn {
return nil , false
}
sinfo , isIn := ss . getByTheirPerm ( p )
return sinfo , isIn
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}
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// Gets a session corresponding to an IPv6 /64 subnet used by the remote node/network.
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func ( ss * sessions ) getByTheirSubnet ( snet * subnet ) ( * sessionInfo , bool ) {
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p , isIn := ss . subnetToPerm [ * snet ]
if ! isIn {
return nil , false
}
sinfo , isIn := ss . getByTheirPerm ( p )
return sinfo , isIn
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}
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// 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).
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func ( ss * sessions ) createSession ( theirPermKey * boxPubKey ) * sessionInfo {
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if ss . sessionFirewallEnabled {
if ! ss . isSessionAllowed ( theirPermKey , true ) {
return nil
}
}
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sinfo := sessionInfo { }
sinfo . core = ss . core
sinfo . theirPermPub = * theirPermKey
pub , priv := newBoxKeys ( )
sinfo . mySesPub = * pub
sinfo . mySesPriv = * priv
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sinfo . myNonce = * newBoxNonce ( )
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sinfo . theirMTU = 1280
sinfo . myMTU = uint16 ( ss . core . tun . mtu )
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now := time . Now ( )
sinfo . time = now
sinfo . mtuTime = now
sinfo . pingTime = now
sinfo . pingSend = now
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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 ) )
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sinfo . send = make ( chan [ ] byte , 32 )
sinfo . recv = make ( chan * wire_trafficPacket , 32 )
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go sinfo . doWorker ( )
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
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}
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func ( ss * sessions ) cleanup ( ) {
// Time thresholds almost certainly could use some adjusting
if time . Since ( ss . lastCleanup ) < time . Minute {
return
}
for _ , s := range ss . sinfos {
if s . timedout ( ) {
s . close ( )
}
}
ss . lastCleanup = time . Now ( )
}
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// Closes a session, removing it from sessions maps and killing the worker goroutine.
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func ( sinfo * sessionInfo ) close ( ) {
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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 )
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}
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// Returns a session ping appropriate for the given session info.
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func ( ss * sessions ) getPing ( sinfo * sessionInfo ) sessionPing {
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loc := ss . core . switchTable . getLocator ( )
coords := loc . getCoords ( )
ref := sessionPing {
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SendPermPub : ss . core . boxPub ,
Handle : sinfo . myHandle ,
SendSesPub : sinfo . mySesPub ,
Tstamp : time . Now ( ) . Unix ( ) ,
Coords : coords ,
MTU : sinfo . myMTU ,
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}
sinfo . myNonce . update ( )
return ref
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}
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// 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.
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func ( ss * sessions ) getSharedKey ( myPriv * boxPrivKey ,
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theirPub * boxPubKey ) * boxSharedKey {
if skey , isIn := ss . permShared [ * theirPub ] ; isIn {
return skey
}
// First do some cleanup
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const maxKeys = 1024
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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 ]
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}
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// Sends a session ping by calling sendPingPong in ping mode.
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func ( ss * sessions ) ping ( sinfo * sessionInfo ) {
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ss . sendPingPong ( sinfo , false )
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}
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// 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.
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func ( ss * sessions ) sendPingPong ( sinfo * sessionInfo , isPong bool ) {
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ping := ss . getPing ( sinfo )
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ping . IsPong = isPong
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bs := ping . encode ( )
shared := ss . getSharedKey ( & ss . core . boxPriv , & sinfo . theirPermPub )
payload , nonce := boxSeal ( shared , bs , nil )
p := wire_protoTrafficPacket {
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Coords : sinfo . coords ,
ToKey : sinfo . theirPermPub ,
FromKey : ss . core . boxPub ,
Nonce : * nonce ,
Payload : payload ,
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}
packet := p . encode ( )
ss . core . router . out ( packet )
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if ! isPong {
sinfo . pingSend = time . Now ( )
}
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}
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// 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.
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func ( ss * sessions ) handlePing ( ping * sessionPing ) {
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// Get the corresponding session (or create a new session)
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sinfo , isIn := ss . getByTheirPerm ( & ping . SendPermPub )
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// Check the session firewall
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if ! isIn && ss . sessionFirewallEnabled {
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if ! ss . isSessionAllowed ( & ping . SendPermPub , false ) {
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return
}
}
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if ! isIn || sinfo . timedout ( ) {
if isIn {
sinfo . close ( )
}
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ss . createSession ( & ping . SendPermPub )
sinfo , isIn = ss . getByTheirPerm ( & ping . SendPermPub )
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if ! isIn {
panic ( "This should not happen" )
}
}
// Update the session
if ! sinfo . update ( ping ) { /*panic("Should not happen in testing")*/
return
}
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if ! ping . IsPong {
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ss . sendPingPong ( sinfo , true )
}
if sinfo . packet != nil {
// send
var bs [ ] byte
bs , sinfo . packet = sinfo . packet , nil
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ss . core . router . sendPacket ( bs )
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}
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}
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// 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.
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func ( n * boxNonce ) minus ( m * boxNonce ) int64 {
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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
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}
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// 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.
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func ( sinfo * sessionInfo ) getMTU ( ) uint16 {
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if sinfo . theirMTU == 0 || sinfo . myMTU == 0 {
return 0
}
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if sinfo . theirMTU < sinfo . myMTU {
return sinfo . theirMTU
}
return sinfo . myMTU
}
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// Checks if a packet's nonce is recent enough to fall within the window of allowed packets, and not already received.
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func ( sinfo * sessionInfo ) nonceIsOK ( theirNonce * boxNonce ) bool {
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// 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 << uint64 ( - diff ) ) != 0
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}
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// Updates the nonce mask by (possibly) shifting the bitmask and setting the bit corresponding to this nonce to 1, and then updating the most recent nonce
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func ( sinfo * sessionInfo ) updateNonce ( theirNonce * boxNonce ) {
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// Shift nonce mask if needed
// Set bit
diff := theirNonce . minus ( & sinfo . theirNonce )
if diff > 0 {
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// This nonce is newer, so shift the window before setting the bit, and update theirNonce in the session info.
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sinfo . nonceMask <<= uint64 ( diff )
sinfo . nonceMask &= 0x01
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sinfo . theirNonce = * theirNonce
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} else {
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// This nonce is older, so set the bit but do not shift the window.
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sinfo . nonceMask &= 0x01 << uint64 ( - diff )
}
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}
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// 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.
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func ( ss * sessions ) resetInits ( ) {
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for _ , sinfo := range ss . sinfos {
sinfo . init = false
}
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}
////////////////////////////////////////////////////////////////////////////////
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// 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.
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func ( sinfo * sessionInfo ) doWorker ( ) {
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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
}
}
}
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}
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// This encrypts a packet, creates a trafficPacket struct, encodes it, and sends it to router.out to pass it to the switch layer.
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func ( sinfo * sessionInfo ) doSend ( bs [ ] byte ) {
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defer util_putBytes ( bs )
if ! sinfo . init {
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// To prevent using empty session keys
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return
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}
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// code isn't multithreaded so appending to this is safe
coords := sinfo . coords
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// Read IPv6 flowlabel field (20 bits).
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// Assumes packet at least contains IPv6 header.
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flowkey := uint64 ( bs [ 1 ] & 0x0f ) << 16 | uint64 ( bs [ 2 ] ) << 8 | uint64 ( bs [ 3 ] )
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// Check if the flowlabel was specified
if flowkey == 0 {
// Does the packet meet the minimum UDP packet size? (others are bigger)
if len ( bs ) >= 48 {
// Is the protocol TCP, UDP, SCTP?
if bs [ 6 ] == 0x06 || bs [ 6 ] == 0x11 || bs [ 6 ] == 0x84 {
// if flowlabel was unspecified (0), try to use known protocols' ports
// protokey: proto | sport | dport
flowkey = uint64 ( bs [ 6 ] ) << 32 /* proto */ |
uint64 ( bs [ 40 ] ) << 24 | uint64 ( bs [ 41 ] ) << 16 /* sport */ |
uint64 ( bs [ 42 ] ) << 8 | uint64 ( bs [ 43 ] ) /* dport */
}
}
}
// If we have a flowkey, either through the IPv6 flowlabel field or through
// known TCP/UDP/SCTP proto-sport-dport triplet, then append it to the coords.
// Appending extra coords after a 0 ensures that we still target the local router
// but lets us send extra data (which is otherwise ignored) to help separate
// traffic streams into independent queues
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if flowkey != 0 {
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coords = append ( coords , 0 ) // First target the local switchport
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coords = wire_put_uint64 ( flowkey , coords ) // Then variable-length encoded flowkey
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}
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// Prepare the payload
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payload , nonce := boxSeal ( & sinfo . sharedSesKey , bs , & sinfo . myNonce )
defer util_putBytes ( payload )
p := wire_trafficPacket {
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Coords : coords ,
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Handle : sinfo . theirHandle ,
Nonce : * nonce ,
Payload : payload ,
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}
packet := p . encode ( )
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sinfo . bytesSent += uint64 ( len ( bs ) )
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sinfo . core . router . out ( packet )
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}
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// 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).
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func ( sinfo * sessionInfo ) doRecv ( p * wire_trafficPacket ) {
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defer util_putBytes ( p . Payload )
if ! sinfo . nonceIsOK ( & p . Nonce ) {
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return
}
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bs , isOK := boxOpen ( & sinfo . sharedSesKey , p . Payload , & p . Nonce )
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if ! isOK {
util_putBytes ( bs )
return
}
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sinfo . updateNonce ( & p . Nonce )
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sinfo . time = time . Now ( )
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sinfo . bytesRecvd += uint64 ( len ( bs ) )
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sinfo . core . router . toRecv <- router_recvPacket { bs , sinfo }
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}