314 lines
8.0 KiB
Go
314 lines
8.0 KiB
Go
package iptables
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import (
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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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"regexp"
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"strconv"
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"strings"
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"sync"
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"github.com/Sirupsen/logrus"
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)
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type Action string
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type Table string
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const (
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Append Action = "-A"
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Delete Action = "-D"
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Insert Action = "-I"
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Nat Table = "nat"
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Filter Table = "filter"
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Mangle Table = "mangle"
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)
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var (
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iptablesPath string
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supportsXlock = false
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// used to lock iptables commands if xtables lock is not supported
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bestEffortLock sync.Mutex
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ErrIptablesNotFound = errors.New("Iptables not found")
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)
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type Chain struct {
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Name string
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Bridge string
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Table Table
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}
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type ChainError struct {
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Chain string
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Output []byte
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}
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func (e ChainError) Error() string {
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return fmt.Sprintf("Error iptables %s: %s", e.Chain, string(e.Output))
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}
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func initCheck() error {
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if iptablesPath == "" {
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path, err := exec.LookPath("iptables")
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if err != nil {
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return ErrIptablesNotFound
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}
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iptablesPath = path
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supportsXlock = exec.Command(iptablesPath, "--wait", "-L", "-n").Run() == nil
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}
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return nil
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}
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func NewChain(name, bridge string, table Table, hairpinMode bool) (*Chain, error) {
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c := &Chain{
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Name: name,
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Bridge: bridge,
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Table: table,
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}
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if string(c.Table) == "" {
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c.Table = Filter
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}
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// Add chain if it doesn't exist
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if _, err := Raw("-t", string(c.Table), "-n", "-L", c.Name); err != nil {
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if output, err := Raw("-t", string(c.Table), "-N", c.Name); err != nil {
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return nil, err
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} else if len(output) != 0 {
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return nil, fmt.Errorf("Could not create %s/%s chain: %s", c.Table, c.Name, output)
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}
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}
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switch table {
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case Nat:
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preroute := []string{
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"-m", "addrtype",
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"--dst-type", "LOCAL"}
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if !Exists(Nat, "PREROUTING", preroute...) {
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if err := c.Prerouting(Append, preroute...); err != nil {
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return nil, fmt.Errorf("Failed to inject docker in PREROUTING chain: %s", err)
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}
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}
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output := []string{
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"-m", "addrtype",
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"--dst-type", "LOCAL"}
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if !hairpinMode {
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output = append(output, "!", "--dst", "127.0.0.0/8")
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}
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if !Exists(Nat, "OUTPUT", output...) {
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if err := c.Output(Append, output...); err != nil {
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return nil, fmt.Errorf("Failed to inject docker in OUTPUT chain: %s", err)
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}
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}
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case Filter:
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link := []string{
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"-o", c.Bridge,
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"-j", c.Name}
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if !Exists(Filter, "FORWARD", link...) {
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insert := append([]string{string(Insert), "FORWARD"}, link...)
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if output, err := Raw(insert...); err != nil {
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return nil, err
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} else if len(output) != 0 {
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return nil, fmt.Errorf("Could not create linking rule to %s/%s: %s", c.Table, c.Name, output)
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}
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}
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}
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return c, nil
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}
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func RemoveExistingChain(name string, table Table) error {
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c := &Chain{
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Name: name,
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Table: table,
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}
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if string(c.Table) == "" {
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c.Table = Filter
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}
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return c.Remove()
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}
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// Add forwarding rule to 'filter' table and corresponding nat rule to 'nat' table
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func (c *Chain) Forward(action Action, ip net.IP, port int, proto, destAddr string, destPort int) error {
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daddr := ip.String()
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if ip.IsUnspecified() {
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// iptables interprets "0.0.0.0" as "0.0.0.0/32", whereas we
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// want "0.0.0.0/0". "0/0" is correctly interpreted as "any
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// value" by both iptables and ip6tables.
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daddr = "0/0"
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}
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if output, err := Raw("-t", string(Nat), string(action), c.Name,
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"-p", proto,
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"-d", daddr,
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"--dport", strconv.Itoa(port),
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"-j", "DNAT",
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"--to-destination", net.JoinHostPort(destAddr, strconv.Itoa(destPort))); err != nil {
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return err
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} else if len(output) != 0 {
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return ChainError{Chain: "FORWARD", Output: output}
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}
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if output, err := Raw("-t", string(Filter), string(action), c.Name,
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"!", "-i", c.Bridge,
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"-o", c.Bridge,
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"-p", proto,
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"-d", destAddr,
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"--dport", strconv.Itoa(destPort),
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"-j", "ACCEPT"); err != nil {
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return err
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} else if len(output) != 0 {
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return ChainError{Chain: "FORWARD", Output: output}
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}
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if output, err := Raw("-t", string(Nat), string(action), "POSTROUTING",
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"-p", proto,
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"-s", destAddr,
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"-d", destAddr,
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"--dport", strconv.Itoa(destPort),
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"-j", "MASQUERADE"); err != nil {
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return err
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} else if len(output) != 0 {
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return ChainError{Chain: "FORWARD", Output: output}
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}
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return nil
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}
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// Add reciprocal ACCEPT rule for two supplied IP addresses.
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// Traffic is allowed from ip1 to ip2 and vice-versa
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func (c *Chain) Link(action Action, ip1, ip2 net.IP, port int, proto string) error {
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if output, err := Raw("-t", string(Filter), string(action), c.Name,
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"-i", c.Bridge, "-o", c.Bridge,
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"-p", proto,
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"-s", ip1.String(),
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"-d", ip2.String(),
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"--dport", strconv.Itoa(port),
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"-j", "ACCEPT"); err != nil {
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return err
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} else if len(output) != 0 {
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return fmt.Errorf("Error iptables forward: %s", output)
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}
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if output, err := Raw("-t", string(Filter), string(action), c.Name,
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"-i", c.Bridge, "-o", c.Bridge,
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"-p", proto,
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"-s", ip2.String(),
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"-d", ip1.String(),
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"--sport", strconv.Itoa(port),
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"-j", "ACCEPT"); err != nil {
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return err
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} else if len(output) != 0 {
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return fmt.Errorf("Error iptables forward: %s", output)
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}
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return nil
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}
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// Add linking rule to nat/PREROUTING chain.
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func (c *Chain) Prerouting(action Action, args ...string) error {
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a := []string{"-t", string(Nat), string(action), "PREROUTING"}
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if len(args) > 0 {
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a = append(a, args...)
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}
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if output, err := Raw(append(a, "-j", c.Name)...); err != nil {
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return err
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} else if len(output) != 0 {
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return ChainError{Chain: "PREROUTING", Output: output}
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}
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return nil
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}
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// Add linking rule to an OUTPUT chain
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func (c *Chain) Output(action Action, args ...string) error {
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a := []string{"-t", string(c.Table), string(action), "OUTPUT"}
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if len(args) > 0 {
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a = append(a, args...)
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}
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if output, err := Raw(append(a, "-j", c.Name)...); err != nil {
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return err
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} else if len(output) != 0 {
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return ChainError{Chain: "OUTPUT", Output: output}
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}
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return nil
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}
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func (c *Chain) Remove() error {
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// Ignore errors - This could mean the chains were never set up
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if c.Table == Nat {
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c.Prerouting(Delete, "-m", "addrtype", "--dst-type", "LOCAL")
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c.Output(Delete, "-m", "addrtype", "--dst-type", "LOCAL", "!", "--dst", "127.0.0.0/8")
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c.Output(Delete, "-m", "addrtype", "--dst-type", "LOCAL") // Created in versions <= 0.1.6
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c.Prerouting(Delete)
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c.Output(Delete)
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}
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Raw("-t", string(c.Table), "-F", c.Name)
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Raw("-t", string(c.Table), "-X", c.Name)
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return nil
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}
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// Check if a rule exists
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func Exists(table Table, chain string, rule ...string) bool {
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if string(table) == "" {
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table = Filter
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}
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// iptables -C, --check option was added in v.1.4.11
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// http://ftp.netfilter.org/pub/iptables/changes-iptables-1.4.11.txt
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// try -C
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// if exit status is 0 then return true, the rule exists
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if _, err := Raw(append([]string{
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"-t", string(table), "-C", chain}, rule...)...); err == nil {
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return true
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}
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// parse "iptables -S" for the rule (this checks rules in a specific chain
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// in a specific table)
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ruleString := strings.Join(rule, " ")
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existingRules, _ := exec.Command(iptablesPath, "-t", string(table), "-S", chain).Output()
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// regex to replace ips in rule
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// because MASQUERADE rule will not be exactly what was passed
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re := regexp.MustCompile(`[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\/[0-9]{1,2}`)
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return strings.Contains(
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re.ReplaceAllString(string(existingRules), "?"),
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re.ReplaceAllString(ruleString, "?"),
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)
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}
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// Call 'iptables' system command, passing supplied arguments
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func Raw(args ...string) ([]byte, error) {
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if firewalldRunning {
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output, err := Passthrough(Iptables, args...)
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if err == nil || !strings.Contains(err.Error(), "was not provided by any .service files") {
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return output, err
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}
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}
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if err := initCheck(); err != nil {
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return nil, err
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}
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if supportsXlock {
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args = append([]string{"--wait"}, args...)
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} else {
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bestEffortLock.Lock()
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defer bestEffortLock.Unlock()
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}
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logrus.Debugf("%s, %v", iptablesPath, args)
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output, err := exec.Command(iptablesPath, args...).CombinedOutput()
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if err != nil {
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return nil, fmt.Errorf("iptables failed: iptables %v: %s (%s)", strings.Join(args, " "), output, err)
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}
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// ignore iptables' message about xtables lock
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if strings.Contains(string(output), "waiting for it to exit") {
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output = []byte("")
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}
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return output, err
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}
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