diff options
author | Kevin Krakauer <krakauer@google.com> | 2020-01-21 14:47:17 -0800 |
---|---|---|
committer | Kevin Krakauer <krakauer@google.com> | 2020-01-21 14:47:17 -0800 |
commit | 9143fcd7fd38243dd40f927dafaeb75f6ef8ef49 (patch) | |
tree | db8e6b1a6ef8916d9e0010805ce148c7a7ae09c7 /pkg/tcpip | |
parent | 9f736ac6a7747917f690596ac9b072c108b5670c (diff) |
Add UDP matchers.
Diffstat (limited to 'pkg/tcpip')
-rw-r--r-- | pkg/tcpip/iptables/BUILD | 2 | ||||
-rw-r--r-- | pkg/tcpip/iptables/iptables.go | 3 | ||||
-rw-r--r-- | pkg/tcpip/iptables/tcp_matcher.go | 122 | ||||
-rw-r--r-- | pkg/tcpip/iptables/types.go | 17 | ||||
-rw-r--r-- | pkg/tcpip/iptables/udp_matcher.go | 127 | ||||
-rw-r--r-- | pkg/tcpip/network/ipv4/ipv4.go | 10 |
6 files changed, 276 insertions, 5 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 +} diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go index 85512f9b2..6597e6781 100644 --- a/pkg/tcpip/network/ipv4/ipv4.go +++ b/pkg/tcpip/network/ipv4/ipv4.go @@ -353,6 +353,11 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt tcpip.PacketBuffer) { } pkt.NetworkHeader = headerView[:h.HeaderLength()] + hlen := int(h.HeaderLength()) + tlen := int(h.TotalLength()) + pkt.Data.TrimFront(hlen) + pkt.Data.CapLength(tlen - hlen) + // iptables filtering. All packets that reach here are intended for // this machine and will not be forwarded. ipt := e.stack.IPTables() @@ -361,11 +366,6 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt tcpip.PacketBuffer) { return } - hlen := int(h.HeaderLength()) - tlen := int(h.TotalLength()) - pkt.Data.TrimFront(hlen) - pkt.Data.CapLength(tlen - hlen) - more := (h.Flags() & header.IPv4FlagMoreFragments) != 0 if more || h.FragmentOffset() != 0 { if pkt.Data.Size() == 0 { |