From 2716ac85a2b50e1fbaa48c443addde4d923e920d Mon Sep 17 00:00:00 2001
From: Louis Royer <infos.louis.royer@gmail.com>
Date: Thu, 18 Jul 2024 09:54:46 +0200
Subject: [PATCH] Drop icmp redirect on tun interfaces

close #69
---
 internal/iproute2/tun-iface.go | 42 ++++++++++++++++++++++++++++++----
 internal/iproute2/utils.go     | 28 +++++++++++++++++++++++
 2 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/internal/iproute2/tun-iface.go b/internal/iproute2/tun-iface.go
index 39b2f82..4ea6495 100644
--- a/internal/iproute2/tun-iface.go
+++ b/internal/iproute2/tun-iface.go
@@ -38,12 +38,29 @@ func (t *TunIface) CreateAndUp() error {
 		return fmt.Errorf("Unable to allocate TUN interface: %s", err)
 	}
 	t.iface = iface
+	if err := t.DropIcmpRedirect(); err != nil {
+		return err
+	}
 	if err := runIP("link", "set", "dev", t.iface.Name(), "up"); err != nil {
 		return err
 	}
 	return nil
 }
 
+// Stop TunIface related goroutines and delete the interface
+func (t *TunIface) Delete() error {
+	if t.iface == nil {
+		return nil
+	}
+	if err := runIP("link", "del", t.iface.Name()); err != nil {
+		return fmt.Errorf("Unable to delete interface %s: %s", t.iface.Name(), err)
+	}
+	if err := t.CancelDropIcmpRedirect(); err != nil {
+		return err
+	}
+	return nil
+}
+
 // MTU of the TunIface
 func (t *TunIface) MTU() (int64, error) {
 	if strings.Contains(t.iface.Name(), "/") || strings.Contains(t.iface.Name(), ".") {
@@ -88,13 +105,30 @@ func (t *TunIface) IPv4TTL() (uint8, error) {
 	return uint8(ret), nil
 }
 
-// Stop TunIface related goroutines and delete the interface
-func (t *TunIface) Delete() error {
+// Drop ICMP/ICMPv6 redirects on the interface
+func (t *TunIface) DropIcmpRedirect() error {
 	if t.iface == nil {
 		return nil
 	}
-	if err := runIP("link", "del", t.iface.Name()); err != nil {
-		return fmt.Errorf("Unable to delete interface %s: %s", t.iface.Name(), err)
+	if err := runIPTables("-A", "OUTPUT", "-o", t.iface.Name(), "-p", "icmp", "--icmp-type", "redirect", "-j", "DROP"); err != nil {
+		return fmt.Errorf("Unable to drop icmp redirect on interface %s: %s", t.iface.Name(), err)
+	}
+	if err := runIP6Tables("-A", "OUTPUT", "-o", t.iface.Name(), "-p", "icmpv6", "--icmpv6-type", "redirect", "-j", "DROP"); err != nil {
+		return fmt.Errorf("Unable to drop icmpv6 redirect on interface %s: %s", t.iface.Name(), err)
+	}
+	return nil
+}
+
+// Cancel Drop ICMP/ICMPv6 redirects on the interface
+func (t *TunIface) CancelDropIcmpRedirect() error {
+	if t.iface == nil {
+		return nil
+	}
+	if err := runIP6Tables("-D", "OUTPUT", "-o", t.iface.Name(), "-p", "icmpv6", "--icmpv6-type", "redirect", "-j", "DROP"); err != nil {
+		return fmt.Errorf("Unable to drop icmpv6 redirect on interface %s: %s", t.iface.Name(), err)
+	}
+	if err := runIPTables("-D", "OUTPUT", "-o", t.iface.Name(), "-p", "icmp", "--icmp-type", "redirect", "-j", "DROP"); err != nil {
+		return fmt.Errorf("Unable to drop icmp redirect on interface %s: %s", t.iface.Name(), err)
 	}
 	return nil
 }
diff --git a/internal/iproute2/utils.go b/internal/iproute2/utils.go
index 28a5afc..4d26d68 100644
--- a/internal/iproute2/utils.go
+++ b/internal/iproute2/utils.go
@@ -25,6 +25,34 @@ func runIP(args ...string) error {
 	return nil
 }
 
+// Run iptables command
+func runIPTables(args ...string) error {
+	cmd := exec.Command("iptables", args...)
+	cmd.Stderr = os.Stderr
+	cmd.Stdout = os.Stdout
+	cmd.Stdin = os.Stdin
+	if err := cmd.Run(); err != nil {
+		errLog := fmt.Sprintf("Error running %s: %s", cmd.Args, err)
+		log.Println(errLog)
+		return err
+	}
+	return nil
+}
+
+// Run ip6tables command
+func runIP6Tables(args ...string) error {
+	cmd := exec.Command("ip6tables", args...)
+	cmd.Stderr = os.Stderr
+	cmd.Stdout = os.Stdout
+	cmd.Stdin = os.Stdin
+	if err := cmd.Run(); err != nil {
+		errLog := fmt.Sprintf("Error running %s: %s", cmd.Args, err)
+		log.Println(errLog)
+		return err
+	}
+	return nil
+}
+
 func IPSrSetSourceAddress(address string) error {
 	return runIP("sr", "tunsrc", "set", address)
 }