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Dont apply race avoidance to existing handshakes, use the handshake time to determine who wins (#451) 

Co-authored-by: Wade Simmons <wadey@slack-corp.com>
This commit is contained in:
Nathan Brown 2021-04-27 21:15:34 -05:00 committed by GitHub
parent df7c7eec4a
commit db23fdf9bc
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 23 additions and 17 deletions
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26
handshake_ix.go
View File

@ -119,11 +119,12 @@ func ixHandshakeStage1(f *Interface, addr *udpAddr, packet []byte, h *Header) {
}
hostinfo := &HostInfo{
ConnectionState: ci,
localIndexId: myIndex,
remoteIndexId: hs.Details.InitiatorIndex,
hostId: vpnIP,
HandshakePacket: make(map[uint8][]byte, 0),
ConnectionState: ci,
localIndexId: myIndex,
remoteIndexId: hs.Details.InitiatorIndex,
hostId: vpnIP,
HandshakePacket: make(map[uint8][]byte, 0),
lastHandshakeTime: hs.Details.Time,
}
hostinfo.Lock()
@ -138,6 +139,8 @@ func ixHandshakeStage1(f *Interface, addr *udpAddr, packet []byte, h *Header) {
hs.Details.ResponderIndex = myIndex
hs.Details.Cert = ci.certState.rawCertificateNoKey
// Update the time in case their clock is way off from ours
hs.Details.Time = uint64(time.Now().Unix())
hsBytes, err := proto.Marshal(hs)
if err != nil {
@ -204,18 +207,15 @@ func ixHandshakeStage1(f *Interface, addr *udpAddr, packet []byte, h *Header) {
}
return
case ErrExistingHostInfo:
// This means there was an existing tunnel and we didn't win
// handshake avoidance
//TODO: sprinkle the new protobuf stuff in here, send a reply to get the recv_errors flowing
//TODO: if not new send a test packet like old
// This means there was an existing tunnel and this handshake was older than the one we are currently based on
f.l.WithField("vpnIp", IntIp(vpnIP)).WithField("udpAddr", addr).
WithField("certName", certName).
WithField("oldHandshakeTime", existing.lastHandshakeTime).
WithField("newHandshakeTime", hostinfo.lastHandshakeTime).
WithField("fingerprint", fingerprint).
WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
Info("Prevented a handshake race")
Info("Handshake too old")
// Send a test packet to trigger an authenticated tunnel test, this should suss out any lingering tunnel issues
f.SendMessageToVpnIp(test, testRequest, vpnIP, []byte(""), make([]byte, 12, 12), make([]byte, mtu))
@ -394,7 +394,7 @@ func ixHandshakeStage2(f *Interface, addr *udpAddr, hostinfo *HostInfo, packet [
Info("Handshake message received")
hostinfo.remoteIndexId = hs.Details.ResponderIndex
hs.Details.Cert = ci.certState.rawCertificateNoKey
hostinfo.lastHandshakeTime = hs.Details.Time
// Store their cert and our symmetric keys
ci.peerCert = remoteCert

9
handshake_manager.go
View File

@ -199,7 +199,7 @@ var (
// exact same handshake packet
//
// ErrExistingHostInfo if we already have an entry in the hostmap for this
// VpnIP and overwrite was false.
// VpnIP and the new handshake was older than the one we currently have
//
// ErrLocalIndexCollision if we already have an entry in the main or pending
// hostmap for the hostinfo.localIndexId.
@ -217,10 +217,12 @@ func (c *HandshakeManager) CheckAndComplete(hostinfo *HostInfo, handshakePacket
return existingHostInfo, ErrAlreadySeen
}
if !overwrite {
// It's a new handshake and we lost the race
// Is this a newer handshake?
if existingHostInfo.lastHandshakeTime >= hostinfo.lastHandshakeTime {
return existingHostInfo, ErrExistingHostInfo
}
existingHostInfo.logger(c.l).Info("Taking new handshake")
}
existingIndex, found := c.mainHostMap.Indexes[hostinfo.localIndexId]
@ -261,7 +263,6 @@ func (c *HandshakeManager) CheckAndComplete(hostinfo *HostInfo, handshakePacket
}
if existingHostInfo != nil {
hostinfo.logger(c.l).Info("Race lost, taking new handshake")
// We are going to overwrite this entry, so remove the old references
delete(c.mainHostMap.Hosts, existingHostInfo.hostId)
delete(c.mainHostMap.Indexes, existingHostInfo.localIndexId)

5
hostmap.go
View File

@ -59,6 +59,11 @@ type HostInfo struct {
// with a handshake
lastRebindCount int8
// lastHandshakeTime records the time the remote side told us about at the stage when the handshake was completed locally
// Stage 1 packet will contain it if I am a responder, stage 2 packet if I am an initiator
// This is used to avoid an attack where a handshake packet is replayed after some time
lastHandshakeTime uint64
lastRoam time.Time
lastRoamRemote *udpAddr
}