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Discard multicast UDP source address. 

RFC-1122 (and others) specify that UDP should not receive
datagrams that have a source address that is a multicast address.
Packets should never be received FROM a multicast address.
See also, RFC 768:  'User Datagram Protocol'
J. Postel, ISI, 28 August 1980
  A UDP datagram received with an invalid IP source address
    (e.g., a broadcast or multicast address) must be discarded
    by UDP or by the IP layer (see rfc 1122 Section 3.2.1.3).
This CL does not address TCP or broadcast which is more complicated.

Also adds a test for both ipv6 and ipv4 UDP.

Fixes #3154

PiperOrigin-RevId: 320547674
This commit is contained in:
gVisor bot 2020-07-09 22:33:53 -07:00
parent 5946f11182
commit 5df3a8fede
4 changed files with 103 additions and 18 deletions
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1
pkg/sentry/socket/netstack/netstack.go
View File

@ -192,6 +192,7 @@ var Metrics = tcpip.Stats{
PacketsSent: mustCreateMetric("/netstack/udp/packets_sent", "Number of UDP datagrams sent."),
PacketSendErrors: mustCreateMetric("/netstack/udp/packet_send_errors", "Number of UDP datagrams failed to be sent."),
ChecksumErrors: mustCreateMetric("/netstack/udp/checksum_errors", "Number of UDP datagrams dropped due to bad checksums."),
InvalidSourceAddress: mustCreateMetric("/netstack/udp/invalid_source", "Number of UDP datagrams dropped due to invalid source address."),
},
}

5
pkg/tcpip/tcpip.go
View File

@ -782,7 +782,7 @@ type CongestionControlOption string
// control algorithms.
type AvailableCongestionControlOption string
// buffer moderation.
// ModerateReceiveBufferOption is used by buffer moderation.
type ModerateReceiveBufferOption bool
// TCPLingerTimeoutOption is used by SetSockOpt/GetSockOpt to set/get the
@ -1244,6 +1244,9 @@ type UDPStats struct {
// ChecksumErrors is the number of datagrams dropped due to bad checksums.
ChecksumErrors *StatCounter
// InvalidSourceAddress is the number of invalid sourced datagrams dropped.
InvalidSourceAddress *StatCounter
}
// Stats holds statistics about the networking stack.

11
pkg/tcpip/transport/udp/endpoint.go
View File

@ -1377,6 +1377,15 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
return
}
// Never receive from a multicast address.
if header.IsV4MulticastAddress(id.RemoteAddress) ||
header.IsV6MulticastAddress(id.RemoteAddress) {
e.stack.Stats().UDP.InvalidSourceAddress.Increment()
e.stack.Stats().IP.InvalidSourceAddressesReceived.Increment()
e.stats.ReceiveErrors.MalformedPacketsReceived.Increment()
return
}
// Verify checksum unless RX checksum offload is enabled.
// On IPv4, UDP checksum is optional, and a zero value means
// the transmitter omitted the checksum generation (RFC768).
@ -1395,10 +1404,10 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
}
}
e.rcvMu.Lock()
e.stack.Stats().UDP.PacketsReceived.Increment()
e.stats.PacketsReceived.Increment()
e.rcvMu.Lock()
// Drop the packet if our buffer is currently full.
if !e.rcvReady || e.rcvClosed {
e.rcvMu.Unlock()

84
pkg/tcpip/transport/udp/udp_test.go
View File

@ -93,6 +93,8 @@ const (
multicastV6Only // V6 multicast on a V6-only socket
broadcast // V4 broadcast on a V4 socket
broadcastIn6 // V4-mapped broadcast on a V6-dual socket
reverseMulticast4 // V4 multicast src. Must fail.
reverseMulticast6 // V6 multicast src. Must fail.
)
func (flow testFlow) String() string {
@ -117,6 +119,10 @@ func (flow testFlow) String() string {
return "broadcast"
case broadcastIn6:
return "broadcastIn6"
case reverseMulticast4:
return "reverseMulticast4"
case reverseMulticast6:
return "reverseMulticast6"
default:
return "unknown"
}
@ -168,6 +174,9 @@ func (flow testFlow) header4Tuple(d packetDirection) header4Tuple {
h.dstAddr.Addr = multicastV6Addr
}
}
if flow.isReverseMulticast() {
h.srcAddr.Addr = flow.getMcastAddr()
}
return h
}
@ -199,9 +208,9 @@ func (flow testFlow) netProto() tcpip.NetworkProtocolNumber {
// endpoint for this flow.
func (flow testFlow) sockProto() tcpip.NetworkProtocolNumber {
switch flow {
case unicastV4in6, unicastV6, unicastV6Only, multicastV4in6, multicastV6, multicastV6Only, broadcastIn6:
case unicastV4in6, unicastV6, unicastV6Only, multicastV4in6, multicastV6, multicastV6Only, broadcastIn6, reverseMulticast6:
return ipv6.ProtocolNumber
case unicastV4, multicastV4, broadcast:
case unicastV4, multicastV4, broadcast, reverseMulticast4:
return ipv4.ProtocolNumber
default:
panic(fmt.Sprintf("invalid testFlow given: %d", flow))
@ -224,7 +233,7 @@ func (flow testFlow) isV6Only() bool {
switch flow {
case unicastV6Only, multicastV6Only:
return true
case unicastV4, unicastV4in6, unicastV6, multicastV4, multicastV4in6, multicastV6, broadcast, broadcastIn6:
case unicastV4, unicastV4in6, unicastV6, multicastV4, multicastV4in6, multicastV6, broadcast, broadcastIn6, reverseMulticast4, reverseMulticast6:
return false
default:
panic(fmt.Sprintf("invalid testFlow given: %d", flow))
@ -235,7 +244,7 @@ func (flow testFlow) isMulticast() bool {
switch flow {
case multicastV4, multicastV4in6, multicastV6, multicastV6Only:
return true
case unicastV4, unicastV4in6, unicastV6, unicastV6Only, broadcast, broadcastIn6:
case unicastV4, unicastV4in6, unicastV6, unicastV6Only, broadcast, broadcastIn6, reverseMulticast4, reverseMulticast6:
return false
default:
panic(fmt.Sprintf("invalid testFlow given: %d", flow))
@ -246,7 +255,7 @@ func (flow testFlow) isBroadcast() bool {
switch flow {
case broadcast, broadcastIn6:
return true
case unicastV4, unicastV4in6, unicastV6, unicastV6Only, multicastV4, multicastV4in6, multicastV6, multicastV6Only:
case unicastV4, unicastV4in6, unicastV6, unicastV6Only, multicastV4, multicastV4in6, multicastV6, multicastV6Only, reverseMulticast4, reverseMulticast6:
return false
default:
panic(fmt.Sprintf("invalid testFlow given: %d", flow))
@ -257,13 +266,22 @@ func (flow testFlow) isMapped() bool {
switch flow {
case unicastV4in6, multicastV4in6, broadcastIn6:
return true
case unicastV4, unicastV6, unicastV6Only, multicastV4, multicastV6, multicastV6Only, broadcast:
case unicastV4, unicastV6, unicastV6Only, multicastV4, multicastV6, multicastV6Only, broadcast, reverseMulticast4, reverseMulticast6:
return false
default:
panic(fmt.Sprintf("invalid testFlow given: %d", flow))
}
}
func (flow testFlow) isReverseMulticast() bool {
switch flow {
case reverseMulticast4, reverseMulticast6:
return true
default:
return false
}
}
type testContext struct {
t *testing.T
linkEP *channel.Endpoint
@ -872,6 +890,60 @@ func TestV4ReadOnBoundToBroadcast(t *testing.T) {
}
}
// TestReadFromMulticast checks that an endpoint will NOT receive a packet
// that was sent with multicast SOURCE address.
func TestReadFromMulticast(t *testing.T) {
for _, flow := range []testFlow{reverseMulticast4, reverseMulticast6} {
t.Run(fmt.Sprintf("flow:%s", flow), func(t *testing.T) {
c := newDualTestContext(t, defaultMTU)
defer c.cleanup()
c.createEndpointForFlow(flow)
if err := c.ep.Bind(tcpip.FullAddress{Port: stackPort}); err != nil {
t.Fatalf("Bind failed: %s", err)
}
testFailingRead(c, flow, false /* expectReadError */)
})
}
}
// TestReadFromMulticaststats checks that a discarded packet
// that that was sent with multicast SOURCE address increments
// the correct counters and that a regular packet does not.
func TestReadFromMulticastStats(t *testing.T) {
t.Helper()
for _, flow := range []testFlow{reverseMulticast4, reverseMulticast6, unicastV4} {
t.Run(fmt.Sprintf("flow:%s", flow), func(t *testing.T) {
c := newDualTestContext(t, defaultMTU)
defer c.cleanup()
c.createEndpointForFlow(flow)
if err := c.ep.Bind(tcpip.FullAddress{Port: stackPort}); err != nil {
t.Fatalf("Bind failed: %s", err)
}
payload := newPayload()
c.injectPacket(flow, payload)
var want uint64 = 0
if flow.isReverseMulticast() {
want = 1
}
if got := c.s.Stats().IP.InvalidSourceAddressesReceived.Value(); got != want {
t.Errorf("got stats.IP.InvalidSourceAddressesReceived.Value() = %d, want = %d", got, want)
}
if got := c.s.Stats().UDP.InvalidSourceAddress.Value(); got != want {
t.Errorf("got stats.UDP.InvalidSourceAddress.Value() = %d, want = %d", got, want)
}
if got := c.ep.Stats().(*tcpip.TransportEndpointStats).ReceiveErrors.MalformedPacketsReceived.Value(); got != want {
t.Errorf("got EP Stats.ReceiveErrors.MalformedPacketsReceived stats = %d, want = %d", got, want)
}
})
}
}
// TestV4ReadBroadcastOnBoundToWildcard checks that an endpoint can bind to ANY
// and receive broadcast and unicast data.
func TestV4ReadBroadcastOnBoundToWildcard(t *testing.T) {