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Add tunnel helper to ipv6rwc
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@neilalexander
neilalexander committed Nov 14, 2024
1 parent 75d2080 commit bec40ed
Showing 1 changed file with 91 additions and 91 deletions.
182 changes: 91 additions & 91 deletions src/ipv6rwc/ipv6rwc.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,7 @@ package ipv6rwc

import (
"crypto/ed25519"
"errors"
"fmt"
"net"
"net/netip"
"sync"
"time"

Expand All @@ -19,15 +17,6 @@ import (

const keyStoreTimeout = 2 * time.Minute

/*
// Out-of-band packet types
const (
typeKeyDummy = iota // nolint:deadcode,varcheck
typeKeyLookup
typeKeyResponse
)
*/

type keyArray [ed25519.PublicKeySize]byte

type keyStore struct {
Expand All @@ -40,6 +29,7 @@ type keyStore struct {
addrBuffer map[address.Address]*buffer
subnetToInfo map[address.Subnet]*keyInfo
subnetBuffer map[address.Subnet]*buffer
tunnelHelper TunnelHelper
mtu uint64
}

Expand All @@ -59,10 +49,6 @@ func (k *keyStore) init(c *core.Core) {
k.core = c
k.address = *address.AddrForKey(k.core.PublicKey())
k.subnet = *address.SubnetForKey(k.core.PublicKey())
/*if err := k.core.SetOutOfBandHandler(k.oobHandler); err != nil {
err = fmt.Errorf("tun.core.SetOutOfBandHander: %w", err)
panic(err)
}*/
k.core.SetPathNotify(func(key ed25519.PublicKey) {
k.update(key)
})
Expand Down Expand Up @@ -182,49 +168,10 @@ func (k *keyStore) resetTimeout(info *keyInfo) {
})
}

/*
func (k *keyStore) oobHandler(fromKey, toKey ed25519.PublicKey, data []byte) { // nolint:unused
if len(data) != 1+ed25519.SignatureSize {
return
}
sig := data[1:]
switch data[0] {
case typeKeyLookup:
snet := *address.SubnetForKey(toKey)
if snet == k.subnet && ed25519.Verify(fromKey, toKey[:], sig) {
// This is looking for at least our subnet (possibly our address)
// Send a response
k.sendKeyResponse(fromKey)
}
case typeKeyResponse:
// TODO keep a list of something to match against...
// Ignore the response if it doesn't match anything of interest...
if ed25519.Verify(fromKey, toKey[:], sig) {
k.update(fromKey)
}
}
}
*/

func (k *keyStore) sendKeyLookup(partial ed25519.PublicKey) {
/*
sig := ed25519.Sign(k.core.PrivateKey(), partial[:])
bs := append([]byte{typeKeyLookup}, sig...)
//_ = k.core.SendOutOfBand(partial, bs)
_ = bs
*/
k.core.SendLookup(partial)
}

/*
func (k *keyStore) sendKeyResponse(dest ed25519.PublicKey) { // nolint:unused
sig := ed25519.Sign(k.core.PrivateKey(), dest[:])
bs := append([]byte{typeKeyResponse}, sig...)
//_ = k.core.SendOutOfBand(dest, bs)
_ = bs
}
*/

func (k *keyStore) readPC(p []byte) (int, error) {
buf := make([]byte, k.core.MTU(), 65535)
for {
Expand All @@ -240,16 +187,22 @@ func (k *keyStore) readPC(p []byte) (int, error) {
if len(bs) == 0 {
continue
}
if bs[0]&0xf0 != 0x60 {
continue // not IPv6
}
if len(bs) < 40 {
ip4 := bs[0]&0xf0 == 0x40
ip6 := bs[0]&0xf0 == 0x60
switch {
case !ip4 && !ip6:
continue
case ip6 && len(bs) < 40:
continue
case ip4 && len(bs) < 20:
continue
}
k.mutex.Lock()
mtu := int(k.mtu)
th := k.tunnelHelper
k.mutex.Unlock()
if len(bs) > mtu {
switch {
case ip6 && len(bs) > mtu:
// Using bs would make it leak off the stack, so copy to buf
buf := make([]byte, 512)
cn := copy(buf, bs)
Expand All @@ -261,51 +214,87 @@ func (k *keyStore) readPC(p []byte) (int, error) {
_, _ = k.writePC(packet)
}
continue
case len(bs) > mtu:
continue
}
var srcAddr, dstAddr address.Address
var srcSubnet, dstSubnet address.Subnet
copy(srcAddr[:], bs[8:])
copy(dstAddr[:], bs[24:])
copy(srcSubnet[:], bs[8:])
copy(dstSubnet[:], bs[24:])
if dstAddr != k.address && dstSubnet != k.subnet {
continue // bad local address/subnet
var addrlen int
switch {
case ip4:
copy(srcAddr[:], bs[12:16])
addrlen = 4
case ip6:
copy(srcAddr[:], bs[8:])
copy(srcSubnet[:], bs[8:])
copy(dstAddr[:], bs[24:])
copy(dstSubnet[:], bs[24:])
addrlen = 16
}
info := k.update(ed25519.PublicKey(from.(iwt.Addr)))
if srcAddr != info.address && srcSubnet != info.subnet {
continue // bad remote address/subnet
srcKey := ed25519.PublicKey(from.(iwt.Addr))
info := k.update(srcKey)
switch {
case ip6 && (srcAddr == info.address || srcSubnet == info.subnet):
return copy(p, bs), nil
case ip4, ip6:
if th == nil {
continue
}
addr, ok := netip.AddrFromSlice(srcAddr[:addrlen])
if !ok || !th.InboundAllowed(addr, srcKey) {
continue
}
}
n = copy(p, bs)
return n, nil
return copy(p, bs), nil
}
}

func (k *keyStore) writePC(bs []byte) (int, error) {
if bs[0]&0xf0 != 0x60 {
return 0, errors.New("not an IPv6 packet") // not IPv6
if len(bs) == 0 {
return 0, nil
}
if len(bs) < 40 {
strErr := fmt.Sprint("undersized IPv6 packet, length: ", len(bs))
return 0, errors.New(strErr)
ip4 := bs[0]&0xf0 == 0x40
ip6 := bs[0]&0xf0 == 0x60
switch {
case !ip4 && !ip6:
return len(bs), nil
case ip6 && len(bs) < 40:
return len(bs), nil
case ip4 && len(bs) < 20:
return len(bs), nil
}
var srcAddr, dstAddr address.Address
var srcSubnet, dstSubnet address.Subnet
copy(srcAddr[:], bs[8:])
copy(dstAddr[:], bs[24:])
copy(srcSubnet[:], bs[8:])
copy(dstSubnet[:], bs[24:])
if srcAddr != k.address && srcSubnet != k.subnet {
// This happens all the time due to link-local traffic
// Don't send back an error, just drop it
strErr := fmt.Sprint("incorrect source address: ", net.IP(srcAddr[:]).String())
return 0, errors.New(strErr)
var dstAddr address.Address
var dstSubnet address.Subnet
var addrlen int
switch {
case ip4:
copy(dstAddr[:], bs[16:20])
addrlen = 4
case ip6:
copy(dstAddr[:], bs[24:40])
copy(dstSubnet[:], bs[24:40])
addrlen = 16
}
if dstAddr.IsValid() {
switch {
case dstAddr.IsValid():
k.sendToAddress(dstAddr, bs)
} else if dstSubnet.IsValid() {
case dstSubnet.IsValid():
k.sendToSubnet(dstSubnet, bs)
} else {
return 0, errors.New("invalid destination address")
default:
k.mutex.Lock()
th := k.tunnelHelper
k.mutex.Unlock()
if th == nil {
return len(bs), nil
}
addr, ok := netip.AddrFromSlice(dstAddr[:addrlen])
if !ok {
return len(bs), nil
}
if key := th.OutboundAllowed(addr); key != nil && len(key) == ed25519.PublicKeySize {
return k.core.WriteTo(bs, iwt.Addr(key))
}
return len(bs), nil
}
return len(bs), nil
}
Expand Down Expand Up @@ -366,3 +355,14 @@ func (rwc *ReadWriteCloser) Close() error {
rwc.core.Stop()
return err
}

func (rwc *ReadWriteCloser) SetTunnelHelper(h TunnelHelper) {
rwc.mutex.Lock()
defer rwc.mutex.Unlock()
rwc.tunnelHelper = h
}

type TunnelHelper interface {
InboundAllowed(srcip netip.Addr, src ed25519.PublicKey) bool
OutboundAllowed(dstip netip.Addr) ed25519.PublicKey
}

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