Add UDP matchers.

5 files changed, 271 insertions, 0 deletions

diff --git a/pkg/tcpip/iptables/BUILD b/pkg/tcpip/iptables/BUILD
index 297eaccaf..ff4e3c932 100644
--- a/pkg/tcpip/iptables/BUILD
+++ b/pkg/tcpip/iptables/BUILD
@@ -7,7 +7,9 @@ go_library(
     srcs = [
         "iptables.go",
         "targets.go",
+        "tcp_matcher.go",
         "types.go",
+        "udp_matcher.go",
     ],
     importpath = "gvisor.dev/gvisor/pkg/tcpip/iptables",
     visibility = ["//visibility:public"],
diff --git a/pkg/tcpip/iptables/iptables.go b/pkg/tcpip/iptables/iptables.go
index fc06b5b87..accedba1e 100644
--- a/pkg/tcpip/iptables/iptables.go
+++ b/pkg/tcpip/iptables/iptables.go
@@ -138,6 +138,8 @@ func EmptyFilterTable() Table {
 // Check runs pkt through the rules for hook. It returns true when the packet
 // should continue traversing the network stack and false when it should be
 // dropped.
+//
+// Precondition: pkt.NetworkHeader is set.
 func (it *IPTables) Check(hook Hook, pkt tcpip.PacketBuffer) bool {
 	// TODO(gvisor.dev/issue/170): A lot of this is uncomplicated because
 	// we're missing features. Jumps, the call stack, etc. aren't checked
@@ -163,6 +165,7 @@ func (it *IPTables) Check(hook Hook, pkt tcpip.PacketBuffer) bool {
 	return true
 }
 
+// Precondition: pkt.NetworkHeader is set.
 func (it *IPTables) checkTable(hook Hook, pkt tcpip.PacketBuffer, tablename string) Verdict {
 	// Start from ruleIdx and walk the list of rules until a rule gives us
 	// a verdict.
diff --git a/pkg/tcpip/iptables/tcp_matcher.go b/pkg/tcpip/iptables/tcp_matcher.go
new file mode 100644
index 000000000..6acbd6eb9
--- /dev/null
+++ b/pkg/tcpip/iptables/tcp_matcher.go
@@ -0,0 +1,122 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iptables
+
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+)
+
+type TCPMatcher struct {
+	data TCPMatcherData
+
+	// tablename string
+	// unsigned int matchsize;
+	// unsigned int usersize;
+	// #ifdef CONFIG_COMPAT
+	// unsigned int compatsize;
+	// #endif
+	// unsigned int hooks;
+	// unsigned short proto;
+	// unsigned short family;
+}
+
+// TODO: Delete?
+// MatchCheckEntryParams
+
+type TCPMatcherData struct {
+	// Filter IPHeaderFilter
+
+	SourcePortStart      uint16
+	SourcePortEnd        uint16
+	DestinationPortStart uint16
+	DestinationPortEnd   uint16
+	Option               uint8
+	FlagMask             uint8
+	FlagCompare          uint8
+	InverseFlags         uint8
+}
+
+func NewTCPMatcher(filter IPHeaderFilter, data TCPMatcherData) (Matcher, error) {
+	// TODO: We currently only support source port and destination port.
+	log.Infof("Adding rule with TCPMatcherData: %+v", data)
+
+	if data.Option != 0 ||
+		data.FlagMask != 0 ||
+		data.FlagCompare != 0 ||
+		data.InverseFlags != 0 {
+		return nil, fmt.Errorf("unsupported TCP matcher flags set")
+	}
+
+	if filter.Protocol != header.TCPProtocolNumber {
+		log.Warningf("TCP matching is only valid for protocol %d.", header.TCPProtocolNumber)
+	}
+
+	return &TCPMatcher{data: data}, nil
+}
+
+// TODO: Check xt_tcpudp.c. Need to check for same things (e.g. fragments).
+func (tm *TCPMatcher) Match(hook Hook, pkt tcpip.PacketBuffer, interfaceName string) (bool, bool) {
+	netHeader := header.IPv4(pkt.NetworkHeader)
+
+	// TODO: Do we check proto here or elsewhere? I think elsewhere (check
+	// codesearch).
+	if netHeader.TransportProtocol() != header.TCPProtocolNumber {
+		return false, false
+	}
+
+	// We dont't match fragments.
+	if frag := netHeader.FragmentOffset(); frag != 0 {
+		if frag == 1 {
+			log.Warningf("Dropping TCP packet: malicious packet with fragment with fragment offest of 1.")
+			return false, true
+		}
+		return false, false
+	}
+
+	// Now we need the transport header. However, this may not have been set
+	// yet.
+	// TODO
+	var tcpHeader header.TCP
+	if pkt.TransportHeader != nil {
+		tcpHeader = header.TCP(pkt.TransportHeader)
+	} else {
+		// The TCP header hasn't been parsed yet. We have to do it here.
+		if len(pkt.Data.First()) < header.TCPMinimumSize {
+			// There's no valid TCP header here, so we hotdrop the
+			// packet.
+			// TODO: Stats.
+			log.Warningf("Dropping TCP packet: size to small.")
+			return false, true
+		}
+		tcpHeader = header.TCP(pkt.Data.First())
+	}
+
+	// Check whether the source and destination ports are within the
+	// matching range.
+	sourcePort := tcpHeader.SourcePort()
+	destinationPort := tcpHeader.DestinationPort()
+	if sourcePort < tm.data.SourcePortStart || tm.data.SourcePortEnd < sourcePort {
+		return false, false
+	}
+	if destinationPort < tm.data.DestinationPortStart || tm.data.DestinationPortEnd < destinationPort {
+		return false, false
+	}
+
+	return true, false
+}
diff --git a/pkg/tcpip/iptables/types.go b/pkg/tcpip/iptables/types.go
index a0bfc8b41..54e66f09a 100644
--- a/pkg/tcpip/iptables/types.go
+++ b/pkg/tcpip/iptables/types.go
@@ -169,12 +169,29 @@ type IPHeaderFilter struct {
 	Protocol tcpip.TransportProtocolNumber
 }
 
+// TODO: Should these be able to marshal/unmarshal themselves?
+// TODO: Something has to map the name to the matcher.
 // A Matcher is the interface for matching packets.
 type Matcher interface {
 	// Match returns whether the packet matches and whether the packet
 	// should be "hotdropped", i.e. dropped immediately. This is usually
 	// used for suspicious packets.
+	//
+	// Precondition: packet.NetworkHeader is set.
 	Match(hook Hook, packet tcpip.PacketBuffer, interfaceName string) (matches bool, hotdrop bool)
+
+	// TODO: Make this typesafe by having each Matcher have their own, typed CheckEntry?
+	// CheckEntry(params MatchCheckEntryParams) bool
+}
+
+// TODO: Unused?
+type MatchCheckEntryParams struct {
+	Table  string // TODO: Tables should be an enum...
+	Filter IPHeaderFilter
+	Info   interface{} // TODO: Type unsafe.
+	// HookMask       uint8
+	// Family         uint8
+	// NFTCompat      bool
 }
 
 // A Target is the interface for taking an action for a packet.
diff --git a/pkg/tcpip/iptables/udp_matcher.go b/pkg/tcpip/iptables/udp_matcher.go
new file mode 100644
index 000000000..ce4368a3d
--- /dev/null
+++ b/pkg/tcpip/iptables/udp_matcher.go
@@ -0,0 +1,127 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iptables
+
+import (
+	"fmt"
+	"runtime/debug"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+)
+
+type UDPMatcher struct {
+	data UDPMatcherData
+
+	// tablename string
+	// unsigned int matchsize;
+	// unsigned int usersize;
+	// #ifdef CONFIG_COMPAT
+	// unsigned int compatsize;
+	// #endif
+	// unsigned int hooks;
+	// unsigned short proto;
+	// unsigned short family;
+}
+
+// TODO: Delete?
+// MatchCheckEntryParams
+
+type UDPMatcherData struct {
+	// Filter IPHeaderFilter
+
+	SourcePortStart      uint16
+	SourcePortEnd        uint16
+	DestinationPortStart uint16
+	DestinationPortEnd   uint16
+	InverseFlags         uint8
+}
+
+func NewUDPMatcher(filter IPHeaderFilter, data UDPMatcherData) (Matcher, error) {
+	// TODO: We currently only support source port and destination port.
+	log.Infof("Adding rule with UDPMatcherData: %+v", data)
+
+	if data.InverseFlags != 0 {
+		return nil, fmt.Errorf("unsupported UDP matcher flags set")
+	}
+
+	if filter.Protocol != header.UDPProtocolNumber {
+		log.Warningf("UDP matching is only valid for protocol %d.", header.UDPProtocolNumber)
+	}
+
+	return &UDPMatcher{data: data}, nil
+}
+
+// TODO: Check xt_tcpudp.c. Need to check for same things (e.g. fragments).
+func (tm *UDPMatcher) Match(hook Hook, pkt tcpip.PacketBuffer, interfaceName string) (bool, bool) {
+	log.Infof("UDPMatcher called from: %s", string(debug.Stack()))
+	netHeader := header.IPv4(pkt.NetworkHeader)
+
+	// TODO: Do we check proto here or elsewhere? I think elsewhere (check
+	// codesearch).
+	if netHeader.TransportProtocol() != header.UDPProtocolNumber {
+		log.Infof("UDPMatcher: wrong protocol number")
+		return false, false
+	}
+
+	// We dont't match fragments.
+	if frag := netHeader.FragmentOffset(); frag != 0 {
+		log.Infof("UDPMatcher: it's a fragment")
+		if frag == 1 {
+			return false, true
+		}
+		log.Warningf("Dropping UDP packet: malicious fragmented packet.")
+		return false, false
+	}
+
+	// Now we need the transport header. However, this may not have been set
+	// yet.
+	// TODO
+	var udpHeader header.UDP
+	if pkt.TransportHeader != nil {
+		log.Infof("UDPMatcher: transport header is not nil")
+		udpHeader = header.UDP(pkt.TransportHeader)
+	} else {
+		log.Infof("UDPMatcher: transport header is nil")
+		log.Infof("UDPMatcher: is network header nil: %t", pkt.NetworkHeader == nil)
+		// The UDP header hasn't been parsed yet. We have to do it here.
+		if len(pkt.Data.First()) < header.UDPMinimumSize {
+			// There's no valid UDP header here, so we hotdrop the
+			// packet.
+			// TODO: Stats.
+			log.Warningf("Dropping UDP packet: size to small.")
+			return false, true
+		}
+		udpHeader = header.UDP(pkt.Data.First())
+	}
+
+	// Check whether the source and destination ports are within the
+	// matching range.
+	sourcePort := udpHeader.SourcePort()
+	destinationPort := udpHeader.DestinationPort()
+	log.Infof("UDPMatcher: sport and dport are %d and %d. sports and dport start and end are (%d, %d) and (%d, %d)",
+		udpHeader.SourcePort(), udpHeader.DestinationPort(),
+		tm.data.SourcePortStart, tm.data.SourcePortEnd,
+		tm.data.DestinationPortStart, tm.data.DestinationPortEnd)
+	if sourcePort < tm.data.SourcePortStart || tm.data.SourcePortEnd < sourcePort {
+		return false, false
+	}
+	if destinationPort < tm.data.DestinationPortStart || tm.data.DestinationPortEnd < destinationPort {
+		return false, false
+	}
+
+	return true, false
+}