432 lines
10 KiB
Go
432 lines
10 KiB
Go
package io
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import (
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"context"
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"encoding/binary"
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"errors"
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"fmt"
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"net"
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"os/exec"
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"strconv"
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"strings"
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"syscall"
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"github.com/coreos/go-iptables/iptables"
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"github.com/florianl/go-nfqueue"
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"github.com/mdlayher/netlink"
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"golang.org/x/sys/unix"
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)
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const (
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nfqueueNum = 100
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nfqueueMaxPacketLen = 0xFFFF
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nfqueueDefaultQueueSize = 128
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nfqueueConnMarkAccept = 1001
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nfqueueConnMarkDrop = 1002
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nftFamily = "inet"
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nftTable = "opengfw"
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)
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func generateNftRules(local, rst bool) (*nftTableSpec, error) {
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if local && rst {
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return nil, errors.New("tcp rst is not supported in local mode")
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}
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table := &nftTableSpec{
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Family: nftFamily,
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Table: nftTable,
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}
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table.Defines = append(table.Defines, fmt.Sprintf("define ACCEPT_CTMARK=%d", nfqueueConnMarkAccept))
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table.Defines = append(table.Defines, fmt.Sprintf("define DROP_CTMARK=%d", nfqueueConnMarkDrop))
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table.Defines = append(table.Defines, fmt.Sprintf("define QUEUE_NUM=%d", nfqueueNum))
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if local {
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table.Chains = []nftChainSpec{
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{Chain: "INPUT", Header: "type filter hook input priority filter; policy accept;"},
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{Chain: "OUTPUT", Header: "type filter hook output priority filter; policy accept;"},
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}
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} else {
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table.Chains = []nftChainSpec{
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{Chain: "FORWARD", Header: "type filter hook forward priority filter; policy accept;"},
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}
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}
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for i := range table.Chains {
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c := &table.Chains[i]
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c.Rules = append(c.Rules, "meta mark $ACCEPT_CTMARK ct mark set $ACCEPT_CTMARK") // Bypass protected connections
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c.Rules = append(c.Rules, "ct mark $ACCEPT_CTMARK counter accept")
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if rst {
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c.Rules = append(c.Rules, "ip protocol tcp ct mark $DROP_CTMARK counter reject with tcp reset")
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}
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c.Rules = append(c.Rules, "ct mark $DROP_CTMARK counter drop")
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c.Rules = append(c.Rules, "counter queue num $QUEUE_NUM bypass")
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}
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return table, nil
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}
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func generateIptRules(local, rst bool) ([]iptRule, error) {
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if local && rst {
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return nil, errors.New("tcp rst is not supported in local mode")
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}
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var chains []string
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if local {
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chains = []string{"INPUT", "OUTPUT"}
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} else {
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chains = []string{"FORWARD"}
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}
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rules := make([]iptRule, 0, 4*len(chains))
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for _, chain := range chains {
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// Bypass protected connections
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rules = append(rules, iptRule{"filter", chain, []string{"-m", "mark", "--mark", strconv.Itoa(nfqueueConnMarkAccept), "-j", "CONNMARK", "--set-mark", strconv.Itoa(nfqueueConnMarkAccept)}})
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rules = append(rules, iptRule{"filter", chain, []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkAccept), "-j", "ACCEPT"}})
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if rst {
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rules = append(rules, iptRule{"filter", chain, []string{"-p", "tcp", "-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkDrop), "-j", "REJECT", "--reject-with", "tcp-reset"}})
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}
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rules = append(rules, iptRule{"filter", chain, []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkDrop), "-j", "DROP"}})
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rules = append(rules, iptRule{"filter", chain, []string{"-j", "NFQUEUE", "--queue-num", strconv.Itoa(nfqueueNum), "--queue-bypass"}})
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}
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return rules, nil
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}
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var _ PacketIO = (*nfqueuePacketIO)(nil)
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var errNotNFQueuePacket = errors.New("not an NFQueue packet")
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type nfqueuePacketIO struct {
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n *nfqueue.Nfqueue
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local bool
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rst bool
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rSet bool // whether the nftables/iptables rules have been set
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// iptables not nil = use iptables instead of nftables
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ipt4 *iptables.IPTables
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ipt6 *iptables.IPTables
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protectedDialer *net.Dialer
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}
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type NFQueuePacketIOConfig struct {
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QueueSize uint32
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ReadBuffer int
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WriteBuffer int
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Local bool
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RST bool
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}
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func NewNFQueuePacketIO(config NFQueuePacketIOConfig) (PacketIO, error) {
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if config.QueueSize == 0 {
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config.QueueSize = nfqueueDefaultQueueSize
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}
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var ipt4, ipt6 *iptables.IPTables
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var err error
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if nftCheck() != nil {
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// We prefer nftables, but if it's not available, fall back to iptables
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ipt4, err = iptables.NewWithProtocol(iptables.ProtocolIPv4)
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if err != nil {
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return nil, err
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}
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ipt6, err = iptables.NewWithProtocol(iptables.ProtocolIPv6)
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if err != nil {
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return nil, err
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}
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}
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n, err := nfqueue.Open(&nfqueue.Config{
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NfQueue: nfqueueNum,
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MaxPacketLen: nfqueueMaxPacketLen,
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MaxQueueLen: config.QueueSize,
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Copymode: nfqueue.NfQnlCopyPacket,
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Flags: nfqueue.NfQaCfgFlagConntrack,
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})
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if err != nil {
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return nil, err
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}
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if config.ReadBuffer > 0 {
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err = n.Con.SetReadBuffer(config.ReadBuffer)
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if err != nil {
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_ = n.Close()
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return nil, err
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}
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}
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if config.WriteBuffer > 0 {
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err = n.Con.SetWriteBuffer(config.WriteBuffer)
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if err != nil {
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_ = n.Close()
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return nil, err
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}
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}
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return &nfqueuePacketIO{
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n: n,
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local: config.Local,
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rst: config.RST,
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ipt4: ipt4,
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ipt6: ipt6,
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protectedDialer: &net.Dialer{
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Control: func(network, address string, c syscall.RawConn) error {
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var err error
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cErr := c.Control(func(fd uintptr) {
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err = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_MARK, nfqueueConnMarkAccept)
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})
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if cErr != nil {
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return cErr
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}
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return err
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},
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},
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}, nil
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}
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func (n *nfqueuePacketIO) Register(ctx context.Context, cb PacketCallback) error {
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err := n.n.RegisterWithErrorFunc(ctx,
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func(a nfqueue.Attribute) int {
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if ok, verdict := n.packetAttributeSanityCheck(a); !ok {
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if a.PacketID != nil {
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_ = n.n.SetVerdict(*a.PacketID, verdict)
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}
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return 0
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}
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p := &nfqueuePacket{
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id: *a.PacketID,
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streamID: ctIDFromCtBytes(*a.Ct),
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data: *a.Payload,
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}
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return okBoolToInt(cb(p, nil))
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},
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func(e error) int {
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if opErr := (*netlink.OpError)(nil); errors.As(e, &opErr) {
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if errors.Is(opErr.Err, unix.ENOBUFS) {
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// Kernel buffer temporarily full, ignore
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return 0
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}
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}
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return okBoolToInt(cb(nil, e))
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})
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if err != nil {
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return err
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}
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if !n.rSet {
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if n.ipt4 != nil {
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err = n.setupIpt(n.local, n.rst, false)
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} else {
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err = n.setupNft(n.local, n.rst, false)
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}
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if err != nil {
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return err
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}
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n.rSet = true
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}
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return nil
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}
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func (n *nfqueuePacketIO) packetAttributeSanityCheck(a nfqueue.Attribute) (ok bool, verdict int) {
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if a.PacketID == nil {
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// Re-inject to NFQUEUE is actually not possible in this condition
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return false, -1
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}
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if a.Payload == nil || len(*a.Payload) < 20 {
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// 20 is the minimum possible size of an IP packet
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return false, nfqueue.NfDrop
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}
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if a.Ct == nil {
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// Multicast packets may not have a conntrack, but only appear in local mode
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if n.local {
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return false, nfqueue.NfAccept
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}
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return false, nfqueue.NfDrop
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}
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return true, -1
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}
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func (n *nfqueuePacketIO) SetVerdict(p Packet, v Verdict, newPacket []byte) error {
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nP, ok := p.(*nfqueuePacket)
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if !ok {
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return &ErrInvalidPacket{Err: errNotNFQueuePacket}
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}
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switch v {
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case VerdictAccept:
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return n.n.SetVerdict(nP.id, nfqueue.NfAccept)
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case VerdictAcceptModify:
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return n.n.SetVerdictModPacket(nP.id, nfqueue.NfAccept, newPacket)
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case VerdictAcceptStream:
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return n.n.SetVerdictWithConnMark(nP.id, nfqueue.NfAccept, nfqueueConnMarkAccept)
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case VerdictDrop:
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return n.n.SetVerdict(nP.id, nfqueue.NfDrop)
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case VerdictDropStream:
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return n.n.SetVerdictWithConnMark(nP.id, nfqueue.NfDrop, nfqueueConnMarkDrop)
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default:
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// Invalid verdict, ignore for now
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return nil
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}
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}
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func (n *nfqueuePacketIO) ProtectedDialContext(ctx context.Context, network, address string) (net.Conn, error) {
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return n.protectedDialer.DialContext(ctx, network, address)
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}
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func (n *nfqueuePacketIO) Close() error {
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if n.rSet {
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if n.ipt4 != nil {
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_ = n.setupIpt(n.local, n.rst, true)
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} else {
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_ = n.setupNft(n.local, n.rst, true)
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}
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n.rSet = false
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}
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return n.n.Close()
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}
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func (n *nfqueuePacketIO) setupNft(local, rst, remove bool) error {
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rules, err := generateNftRules(local, rst)
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if err != nil {
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return err
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}
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rulesText := rules.String()
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if remove {
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err = nftDelete(nftFamily, nftTable)
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} else {
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// Delete first to make sure no leftover rules
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_ = nftDelete(nftFamily, nftTable)
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err = nftAdd(rulesText)
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}
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if err != nil {
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return err
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}
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return nil
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}
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func (n *nfqueuePacketIO) setupIpt(local, rst, remove bool) error {
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rules, err := generateIptRules(local, rst)
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if err != nil {
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return err
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}
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if remove {
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err = iptsBatchDeleteIfExists([]*iptables.IPTables{n.ipt4, n.ipt6}, rules)
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} else {
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err = iptsBatchAppendUnique([]*iptables.IPTables{n.ipt4, n.ipt6}, rules)
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}
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if err != nil {
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return err
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}
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return nil
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}
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var _ Packet = (*nfqueuePacket)(nil)
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type nfqueuePacket struct {
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id uint32
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streamID uint32
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data []byte
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}
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func (p *nfqueuePacket) StreamID() uint32 {
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return p.streamID
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}
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func (p *nfqueuePacket) Data() []byte {
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return p.data
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}
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func okBoolToInt(ok bool) int {
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if ok {
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return 0
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} else {
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return 1
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}
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}
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func nftCheck() error {
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_, err := exec.LookPath("nft")
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if err != nil {
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return err
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}
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return nil
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}
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func nftAdd(input string) error {
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cmd := exec.Command("nft", "-f", "-")
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cmd.Stdin = strings.NewReader(input)
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return cmd.Run()
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}
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func nftDelete(family, table string) error {
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cmd := exec.Command("nft", "delete", "table", family, table)
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return cmd.Run()
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}
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type nftTableSpec struct {
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Defines []string
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Family, Table string
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Chains []nftChainSpec
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}
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func (t *nftTableSpec) String() string {
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chains := make([]string, 0, len(t.Chains))
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for _, c := range t.Chains {
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chains = append(chains, c.String())
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}
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return fmt.Sprintf(`
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%s
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table %s %s {
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%s
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}
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`, strings.Join(t.Defines, "\n"), t.Family, t.Table, strings.Join(chains, ""))
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}
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type nftChainSpec struct {
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Chain string
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Header string
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Rules []string
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}
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func (c *nftChainSpec) String() string {
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return fmt.Sprintf(`
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chain %s {
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%s
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%s
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}
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`, c.Chain, c.Header, strings.Join(c.Rules, "\n\x20\x20\x20\x20"))
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}
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type iptRule struct {
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Table, Chain string
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RuleSpec []string
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}
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func iptsBatchAppendUnique(ipts []*iptables.IPTables, rules []iptRule) error {
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for _, r := range rules {
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for _, ipt := range ipts {
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err := ipt.AppendUnique(r.Table, r.Chain, r.RuleSpec...)
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if err != nil {
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return err
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}
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}
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}
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return nil
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}
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func iptsBatchDeleteIfExists(ipts []*iptables.IPTables, rules []iptRule) error {
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for _, r := range rules {
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for _, ipt := range ipts {
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err := ipt.DeleteIfExists(r.Table, r.Chain, r.RuleSpec...)
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if err != nil {
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return err
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}
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}
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}
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return nil
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}
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func ctIDFromCtBytes(ct []byte) uint32 {
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ctAttrs, err := netlink.UnmarshalAttributes(ct)
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if err != nil {
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return 0
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}
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for _, attr := range ctAttrs {
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if attr.Type == 12 { // CTA_ID
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return binary.BigEndian.Uint32(attr.Data)
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}
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}
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return 0
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}
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