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tstest/natlab: support different firewall selectivities.

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Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2020-07-12 05:33:16 +00:00 committed by Dave Anderson
parent c1d9e41bef
commit 39ecb37fd6
2 changed files with 147 additions and 40 deletions
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91
tstest/natlab/firewall.go
View File

@ -5,35 +5,93 @@
package natlab
import (
"fmt"
"sync"
"time"
"inet.af/netaddr"
)
type session struct {
// FirewallType is the type of filtering a stateful firewall
// does. Values express different modes defined by RFC 4787.
type FirewallType int
const (
// AddressAndPortDependentFirewall specifies a destination
// address-and-port dependent firewall. Outbound traffic to an
// ip:port authorizes traffic from that ip:port exactly, and
// nothing else.
AddressAndPortDependentFirewall FirewallType = iota
// AddressDependentFirewall specifies a destination address
// dependent firewall. Once outbound traffic has been seen to an
// IP address, that IP address can talk back from any port.
AddressDependentFirewall
// EndpointIndependentFirewall specifies a destination endpoint
// independent firewall. Once outbound traffic has been seen from
// a source, anyone can talk back to that source.
EndpointIndependentFirewall
)
// fwKey is the lookup key for a firewall session. While it contains a
// 4-tuple ({src,dst} {ip,port}), some FirewallTypes will zero out
// some fields, so in practice the key is either a 2-tuple (src only),
// 3-tuple (src ip+port and dst ip) or 4-tuple (src+dst ip+port).
type fwKey struct {
src netaddr.IPPort
dst netaddr.IPPort
}
// key returns an fwKey for the given src and dst, trimmed according
// to the FirewallType. fwKeys are always constructed from the
// "outbound" point of view (i.e. src is the "trusted" side of the
// world), it's the caller's responsibility to swap src and dst in the
// call to key when processing packets inbound from the "untrusted"
// world.
func (s FirewallType) key(src, dst netaddr.IPPort) fwKey {
k := fwKey{src: src}
switch s {
case EndpointIndependentFirewall:
case AddressDependentFirewall:
k.dst.IP = dst.IP
case AddressAndPortDependentFirewall:
k.dst = dst
default:
panic(fmt.Sprintf("unknown firewall selectivity %v", s))
}
return k
}
// DefaultSessionTimeout is the default timeout for a firewall
// session.
const DefaultSessionTimeout = 30 * time.Second
// Firewall is a simple stateful firewall that allows all outbound
// traffic and filters inbound traffic based on recently seen outbound
// traffic. Its HandlePacket method should be attached to a Machine to
// give it a stateful firewall.
type Firewall struct {
// TrustedInterface is the interface that's allowed to send
// anywhere. All other interfaces can only respond to traffic from
// TrustedInterface.
TrustedInterface *Interface
// SessionTimeout is the lifetime of idle sessions in the firewall
// state. Packets transiting from the TrustedInterface reset the
// session lifetime to SessionTimeout.
// session lifetime to SessionTimeout. If zero,
// DefaultSessionTimeout is used.
SessionTimeout time.Duration
// Type specifies how precisely return traffic must match
// previously seen outbound traffic to be allowed. Defaults to
// AddressAndPortDependentFirewall.
Type FirewallType
// TrustedInterface is an optional interface that is considered
// trusted in addition to PacketConns local to the Machine. All
// other interfaces can only respond to traffic from
// TrustedInterface or the local host.
TrustedInterface *Interface
// TimeNow is a function returning the current time. If nil,
// time.Now is used.
TimeNow func() time.Time
// TODO: tuple-ness pickiness: EIF, ADF, APDF
// TODO: refresh directionality: outbound-only, both
mu sync.Mutex
seen map[session]time.Time // session -> deadline
seen map[fwKey]time.Time // session -> deadline
}
func (f *Firewall) timeNow() time.Time {
@ -43,33 +101,28 @@ func (f *Firewall) timeNow() time.Time {
return time.Now()
}
// HandlePacket implements the PacketHandler type.
func (f *Firewall) HandlePacket(p *Packet, inIf *Interface) PacketVerdict {
f.mu.Lock()
defer f.mu.Unlock()
if f.seen == nil {
f.seen = map[session]time.Time{}
f.seen = map[fwKey]time.Time{}
}
if f.SessionTimeout == 0 {
f.SessionTimeout = 30 * time.Second
}
if inIf == f.TrustedInterface || inIf == nil {
sess := session{
src: p.Src,
dst: p.Dst,
}
f.seen[sess] = f.timeNow().Add(f.SessionTimeout)
k := f.Type.key(p.Src, p.Dst)
f.seen[k] = f.timeNow().Add(f.SessionTimeout)
p.Trace("firewall out ok")
return Continue
} else {
// reverse src and dst because the session table is from the
// POV of outbound packets.
sess := session{
src: p.Dst,
dst: p.Src,
}
k := f.Type.key(p.Dst, p.Src)
now := f.timeNow()
if now.After(f.seen[sess]) {
if now.After(f.seen[k]) {
p.Trace("firewall drop")
return Drop
}

96
tstest/natlab/natlab_test.go
View File

@ -224,8 +224,6 @@ func TestPacketHandler(t *testing.T) {
}
func TestFirewall(t *testing.T) {
clock := &tstest.Clock{}
wan := NewInternet()
lan := &Network{
Name: "lan",
@ -235,28 +233,84 @@ func TestFirewall(t *testing.T) {
trust := m.Attach("trust", lan)
untrust := m.Attach("untrust", wan)
f := &Firewall{
TrustedInterface: trust,
SessionTimeout: 30 * time.Second,
TimeNow: clock.Now,
}
client := ipp("192.168.0.2:1234")
serverA := ipp("2.2.2.2:5678")
serverB := ipp("7.7.7.7:9012")
tests := []struct {
iface *Interface
src, dst netaddr.IPPort
want PacketVerdict
}{
{trust, client, serverA, Continue},
{untrust, serverA, client, Continue},
{untrust, serverA, client, Continue},
{untrust, serverB, client, Drop},
{trust, client, serverB, Continue},
{untrust, serverB, client, Continue},
}
serverB1 := ipp("7.7.7.7:9012")
serverB2 := ipp("7.7.7.7:3456")
t.Run("ip_port_dependent", func(t *testing.T) {
f := &Firewall{
TrustedInterface: trust,
SessionTimeout: 30 * time.Second,
Type: AddressAndPortDependentFirewall,
}
testFirewall(t, f, []fwTest{
// client -> A authorizes A -> client
{trust, client, serverA, Continue},
{untrust, serverA, client, Continue},
{untrust, serverA, client, Continue},
// B1 -> client fails until client -> B1
{untrust, serverB1, client, Drop},
{trust, client, serverB1, Continue},
{untrust, serverB1, client, Continue},
// B2 -> client still fails
{untrust, serverB2, client, Drop},
})
})
t.Run("ip_dependent", func(t *testing.T) {
f := &Firewall{
TrustedInterface: trust,
SessionTimeout: 30 * time.Second,
Type: AddressDependentFirewall,
}
testFirewall(t, f, []fwTest{
// client -> A authorizes A -> client
{trust, client, serverA, Continue},
{untrust, serverA, client, Continue},
{untrust, serverA, client, Continue},
// B1 -> client fails until client -> B1
{untrust, serverB1, client, Drop},
{trust, client, serverB1, Continue},
{untrust, serverB1, client, Continue},
// B2 -> client also works now
{untrust, serverB2, client, Continue},
})
})
t.Run("endpoint_independent", func(t *testing.T) {
f := &Firewall{
TrustedInterface: trust,
SessionTimeout: 30 * time.Second,
Type: EndpointIndependentFirewall,
}
testFirewall(t, f, []fwTest{
// client -> A authorizes A -> client
{trust, client, serverA, Continue},
{untrust, serverA, client, Continue},
{untrust, serverA, client, Continue},
// B1 -> client also works
{untrust, serverB1, client, Continue},
// B2 -> client also works
{untrust, serverB2, client, Continue},
})
})
}
type fwTest struct {
iface *Interface
src, dst netaddr.IPPort
want PacketVerdict
}
func testFirewall(t *testing.T, f *Firewall, tests []fwTest) {
t.Helper()
clock := &tstest.Clock{}
f.TimeNow = clock.Now
for _, test := range tests {
clock.Advance(time.Second)
p := &Packet{