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Feature/Bugfix: IPv6 blocking (#428)

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- Feature/Bugfix: Block all IPv6 traffic with `ip6tables` by default
- Feature: Adapt existing firewall code to handle IPv4 and IPv6, depending on user inputs and environment
- Maintenance: improve error wrapping in the firewall package
This commit is contained in:
Quentin McGaw
2021-04-19 09:24:46 -04:00
committed by GitHub
parent d3df5aaa52
commit 7ba98af1cc
5 changed files with 171 additions and 37 deletions
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32
internal/firewall/enable.go
View File

@@ -2,11 +2,18 @@ package firewall
import (
"context"
"errors"
"fmt"
"github.com/qdm12/gluetun/internal/constants"
)
var (
ErrEnable = errors.New("failed enabling firewall")
ErrDisable = errors.New("failed disabling firewall")
ErrUserPostRules = errors.New("cannot run user post firewall rules")
)
func (c *configurator) SetEnabled(ctx context.Context, enabled bool) (err error) {
c.stateMutex.Lock()
defer c.stateMutex.Unlock()
@@ -23,7 +30,7 @@ func (c *configurator) SetEnabled(ctx context.Context, enabled bool) (err error)
if !enabled {
c.logger.Info("disabling...")
if err = c.disable(ctx); err != nil {
return err
return fmt.Errorf("%w: %s", ErrDisable, err)
}
c.enabled = false
c.logger.Info("disabled successfully")
@@ -33,7 +40,7 @@ func (c *configurator) SetEnabled(ctx context.Context, enabled bool) (err error)
c.logger.Info("enabling...")
if err := c.enable(ctx); err != nil {
return err
return fmt.Errorf("%w: %s", ErrEnable, err)
}
c.enabled = true
c.logger.Info("enabled successfully")
@@ -45,7 +52,10 @@ func (c *configurator) disable(ctx context.Context) (err error) {
if err = c.clearAllRules(ctx); err != nil {
return fmt.Errorf("cannot disable firewall: %w", err)
}
if err = c.setAllPolicies(ctx, "ACCEPT"); err != nil {
if err = c.setIPv4AllPolicies(ctx, "ACCEPT"); err != nil {
return fmt.Errorf("cannot disable firewall: %w", err)
}
if err = c.setIPv6AllPolicies(ctx, "ACCEPT"); err != nil {
return fmt.Errorf("cannot disable firewall: %w", err)
}
return nil
@@ -56,20 +66,26 @@ func (c *configurator) fallbackToDisabled(ctx context.Context) {
if ctx.Err() != nil {
return
}
if err := c.SetEnabled(ctx, false); err != nil {
c.logger.Error(err)
if err := c.disable(ctx); err != nil {
c.logger.Error("failed reversing firewall changes: " + err.Error())
}
}
func (c *configurator) enable(ctx context.Context) (err error) {
if err = c.setAllPolicies(ctx, "DROP"); err != nil {
touched := false
if err = c.setIPv4AllPolicies(ctx, "DROP"); err != nil {
return fmt.Errorf("cannot enable firewall: %w", err)
}
touched = true
if err = c.setIPv6AllPolicies(ctx, "DROP"); err != nil {
return fmt.Errorf("cannot enable firewall: %w", err)
}
const remove = false
defer func() {
if err != nil {
if touched && err != nil {
c.fallbackToDisabled(ctx)
}
}()
@@ -121,7 +137,7 @@ func (c *configurator) enable(ctx context.Context) (err error) {
}
if err := c.runUserPostRules(ctx, "/iptables/post-rules.txt", remove); err != nil {
return fmt.Errorf("cannot enable firewall: %w", err)
return fmt.Errorf("%w: %s", ErrUserPostRules, err)
}
return nil

1
internal/firewall/firewall.go
View File

@@ -34,6 +34,7 @@ type configurator struct { //nolint:maligned
routing routing.Routing
openFile os.OpenFileFunc // for custom iptables rules
iptablesMutex sync.Mutex
ip6tablesMutex sync.Mutex
debug bool
defaultInterface string
defaultGateway net.IP

47
internal/firewall/ip6tables.go Normal file
View File

@@ -0,0 +1,47 @@
package firewall
import (
"context"
"errors"
"fmt"
"strings"
)
var (
ErrIP6Tables = errors.New("failed ip6tables command")
)
func (c *configurator) runIP6tablesInstructions(ctx context.Context, instructions []string) error {
for _, instruction := range instructions {
if err := c.runIP6tablesInstruction(ctx, instruction); err != nil {
return err
}
}
return nil
}
func (c *configurator) runIP6tablesInstruction(ctx context.Context, instruction string) error {
c.ip6tablesMutex.Lock() // only one ip6tables command at once
defer c.ip6tablesMutex.Unlock()
if c.debug {
fmt.Println("ip6tables " + instruction)
}
flags := strings.Fields(instruction)
if output, err := c.commander.Run(ctx, "ip6tables", flags...); err != nil {
return fmt.Errorf("%w \"ip6tables %s\": %s: %s", ErrIP6Tables, instruction, output, err)
}
return nil
}
func (c *configurator) setIPv6AllPolicies(ctx context.Context, policy string) error {
switch policy {
case "ACCEPT", "DROP":
default:
return fmt.Errorf("policy %q not recognized", policy)
}
return c.runIP6tablesInstructions(ctx, []string{
"--policy INPUT " + policy,
"--policy OUTPUT " + policy,
"--policy FORWARD " + policy,
})
}

107
internal/firewall/iptables.go
View File

@@ -2,6 +2,7 @@ package firewall
import (
"context"
"errors"
"fmt"
"io/ioutil"
"net"
@@ -11,6 +12,14 @@ import (
"github.com/qdm12/gluetun/internal/models"
)
var (
ErrIPTablesVersionTooShort = errors.New("iptables version string is too short")
ErrIPTables = errors.New("failed iptables command")
ErrPolicyUnknown = errors.New("unknown policy")
ErrClearRules = errors.New("cannot clear all rules")
ErrSetIPtablesPolicies = errors.New("cannot set iptables policies")
)
func appendOrDelete(remove bool) string {
if remove {
return "--delete"
@@ -43,7 +52,7 @@ func (c *configurator) Version(ctx context.Context) (string, error) {
words := strings.Fields(output)
const minWords = 2
if len(words) < minWords {
return "", fmt.Errorf("iptables --version: output is too short: %q", output)
return "", fmt.Errorf("%w: %s", ErrIPTablesVersionTooShort, output)
}
return words[1], nil
}
@@ -65,55 +74,68 @@ func (c *configurator) runIptablesInstruction(ctx context.Context, instruction s
}
flags := strings.Fields(instruction)
if output, err := c.commander.Run(ctx, "iptables", flags...); err != nil {
return fmt.Errorf("failed executing \"iptables %s\": %s: %w", instruction, output, err)
return fmt.Errorf("%w \"iptables %s\": %s: %s", ErrIPTables, instruction, output, err)
}
return nil
}
func (c *configurator) clearAllRules(ctx context.Context) error {
return c.runIptablesInstructions(ctx, []string{
if err := c.runMixedIptablesInstructions(ctx, []string{
"--flush", // flush all chains
"--delete-chain", // delete all chains
})
}); err != nil {
return fmt.Errorf("%w: %s", ErrClearRules, err.Error())
}
return nil
}
func (c *configurator) setAllPolicies(ctx context.Context, policy string) error {
func (c *configurator) setIPv4AllPolicies(ctx context.Context, policy string) error {
switch policy {
case "ACCEPT", "DROP":
default:
return fmt.Errorf("policy %q not recognized", policy)
return fmt.Errorf("%w: %s: %s", ErrSetIPtablesPolicies, ErrPolicyUnknown, policy)
}
return c.runIptablesInstructions(ctx, []string{
fmt.Sprintf("--policy INPUT %s", policy),
fmt.Sprintf("--policy OUTPUT %s", policy),
fmt.Sprintf("--policy FORWARD %s", policy),
})
if err := c.runIptablesInstructions(ctx, []string{
"--policy INPUT " + policy,
"--policy OUTPUT " + policy,
"--policy FORWARD " + policy,
}); err != nil {
return fmt.Errorf("%w: %s", ErrSetIPtablesPolicies, err)
}
return nil
}
func (c *configurator) acceptInputThroughInterface(ctx context.Context, intf string, remove bool) error {
return c.runIptablesInstruction(ctx, fmt.Sprintf(
return c.runMixedIptablesInstruction(ctx, fmt.Sprintf(
"%s INPUT -i %s -j ACCEPT", appendOrDelete(remove), intf,
))
}
func (c *configurator) acceptInputToSubnet(ctx context.Context, intf string, destination net.IPNet, remove bool) error {
isIP4Subnet := destination.IP.To4() != nil
interfaceFlag := "-i " + intf
if intf == "*" { // all interfaces
interfaceFlag = ""
}
return c.runIptablesInstruction(ctx, fmt.Sprintf(
"%s INPUT %s -d %s -j ACCEPT", appendOrDelete(remove), interfaceFlag, destination.String(),
))
instruction := fmt.Sprintf("%s INPUT %s -d %s -j ACCEPT",
appendOrDelete(remove), interfaceFlag, destination.String())
if isIP4Subnet {
return c.runIptablesInstruction(ctx, instruction)
}
return c.runIP6tablesInstruction(ctx, instruction)
}
func (c *configurator) acceptOutputThroughInterface(ctx context.Context, intf string, remove bool) error {
return c.runIptablesInstruction(ctx, fmt.Sprintf(
return c.runMixedIptablesInstruction(ctx, fmt.Sprintf(
"%s OUTPUT -o %s -j ACCEPT", appendOrDelete(remove), intf,
))
}
func (c *configurator) acceptEstablishedRelatedTraffic(ctx context.Context, remove bool) error {
return c.runIptablesInstructions(ctx, []string{
return c.runMixedIptablesInstructions(ctx, []string{
fmt.Sprintf("%s OUTPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT", appendOrDelete(remove)),
fmt.Sprintf("%s INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT", appendOrDelete(remove)),
})
@@ -121,22 +143,33 @@ func (c *configurator) acceptEstablishedRelatedTraffic(ctx context.Context, remo
func (c *configurator) acceptOutputTrafficToVPN(ctx context.Context,
defaultInterface string, connection models.OpenVPNConnection, remove bool) error {
return c.runIptablesInstruction(ctx,
fmt.Sprintf("%s OUTPUT -d %s -o %s -p %s -m %s --dport %d -j ACCEPT",
appendOrDelete(remove), connection.IP, defaultInterface, connection.Protocol, connection.Protocol, connection.Port))
instruction := fmt.Sprintf("%s OUTPUT -d %s -o %s -p %s -m %s --dport %d -j ACCEPT",
appendOrDelete(remove), connection.IP, defaultInterface, connection.Protocol,
connection.Protocol, connection.Port)
isIPv4 := connection.IP.To4() != nil
if isIPv4 {
return c.runIptablesInstruction(ctx, instruction)
}
return c.runIP6tablesInstruction(ctx, instruction)
}
// Thanks to @npawelek.
func (c *configurator) acceptOutputFromIPToSubnet(ctx context.Context,
intf string, sourceIP net.IP, destinationSubnet net.IPNet, remove bool) error {
doIPv4 := sourceIP.To4() != nil && destinationSubnet.IP.To4() != nil
interfaceFlag := "-o " + intf
if intf == "*" { // all interfaces
interfaceFlag = ""
}
return c.runIptablesInstruction(ctx, fmt.Sprintf(
"%s OUTPUT %s -s %s -d %s -j ACCEPT",
appendOrDelete(remove), interfaceFlag, sourceIP.String(), destinationSubnet.String(),
))
instruction := fmt.Sprintf("%s OUTPUT %s -s %s -d %s -j ACCEPT",
appendOrDelete(remove), interfaceFlag, sourceIP.String(), destinationSubnet.String())
if doIPv4 {
return c.runIptablesInstruction(ctx, instruction)
}
return c.runIP6tablesInstruction(ctx, instruction)
}
// Used for port forwarding, with intf set to tun.
@@ -145,7 +178,7 @@ func (c *configurator) acceptInputToPort(ctx context.Context, intf string, port
if intf == "*" { // all interfaces
interfaceFlag = ""
}
return c.runIptablesInstructions(ctx, []string{
return c.runMixedIptablesInstructions(ctx, []string{
fmt.Sprintf("%s INPUT %s -p tcp --dport %d -j ACCEPT", appendOrDelete(remove), interfaceFlag, port),
fmt.Sprintf("%s INPUT %s -p udp --dport %d -j ACCEPT", appendOrDelete(remove), interfaceFlag, port),
})
@@ -178,16 +211,32 @@ func (c *configurator) runUserPostRules(ctx context.Context, filepath string, re
}
}()
for _, line := range lines {
if !strings.HasPrefix(line, "iptables ") {
var ipv4 bool
var rule string
switch {
case strings.HasPrefix(line, "iptables "):
ipv4 = true
rule = strings.TrimPrefix(line, "iptables ")
case strings.HasPrefix(line, "ip6tables "):
ipv4 = false
rule = strings.TrimPrefix(line, "ip6tables ")
default:
continue
}
rule := strings.TrimPrefix(line, "iptables ")
if remove {
rule = flipRule(rule)
}
if err = c.runIptablesInstruction(ctx, rule); err != nil {
return fmt.Errorf("cannot run custom rule: %w", err)
if ipv4 {
err = c.runIptablesInstruction(ctx, rule)
} else {
err = c.runIP6tablesInstruction(ctx, rule)
}
if err != nil {
return err
}
successfulRules = append(successfulRules, rule)
}
return nil

21
internal/firewall/iptablesmix.go Normal file
View File

@@ -0,0 +1,21 @@
package firewall
import (
"context"
)
func (c *configurator) runMixedIptablesInstructions(ctx context.Context, instructions []string) error {
for _, instruction := range instructions {
if err := c.runMixedIptablesInstruction(ctx, instruction); err != nil {
return err
}
}
return nil
}
func (c *configurator) runMixedIptablesInstruction(ctx context.Context, instruction string) error {
if err := c.runIptablesInstruction(ctx, instruction); err != nil {
return err
}
return c.runIP6tablesInstruction(ctx, instruction)
}