/
ipsec.go
565 lines (471 loc) · 15.1 KB
/
ipsec.go
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// package IPsec provides primitives for establishing IPsec in the fastdp mode.
package ipsec
import (
"crypto/rand"
"crypto/sha256"
"encoding/binary"
"fmt"
"io"
"net"
"strconv"
"sync"
"syscall"
"github.com/coreos/go-iptables/iptables"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"github.com/vishvananda/netlink"
"golang.org/x/crypto/hkdf"
"github.com/weaveworks/mesh"
)
const (
keySize = 36 // AES-GCM key 32 bytes + 4 bytes salt
nonceSize = 32 // HKDF nonce size
mark = uint32(0x1) << 17 // iptables marks
markStr = "0x20000/0x20000" // update if the above mark changes
tableMangle = "mangle"
tableFilter = "filter"
chainIn = "WEAVE-IPSEC-IN"
chainInMark = "WEAVE-IPSEC-IN-MARK"
chainOut = "WEAVE-IPSEC-OUT"
chainOutMark = "WEAVE-IPSEC-OUT-MARK"
)
type SPI uint32
// Used to identify:
// - directional SPIs,
// - ipsec establishments.
type spiID [24]byte
func getSPIId(srcPeer, dstPeer mesh.PeerName, connUID uint64) (id spiID) {
binary.BigEndian.PutUint64(id[:], uint64(srcPeer))
binary.BigEndian.PutUint64(id[8:], uint64(dstPeer))
binary.BigEndian.PutUint64(id[16:], connUID)
return
}
type spiInfo struct {
spi SPI
isDirOut bool
}
// IPSec
type IPSec struct {
sync.RWMutex
ipt *iptables.IPTables
log *logrus.Logger
spiInfo map[spiID]spiInfo
// A reference to spiInfo; spiInfo might be of an expired SPI.
spis map[SPI]*spiInfo
}
func New(log *logrus.Logger) (*IPSec, error) {
ipt, err := iptables.New()
if err != nil {
return nil, errors.Wrap(err, "iptables new")
}
ipsec := &IPSec{
ipt: ipt,
log: log,
spiInfo: make(map[spiID]spiInfo),
spis: make(map[SPI]*spiInfo),
}
return ipsec, nil
}
// InitSALocal initializes inbound ipsec from remotePeer and triggers
// the initialization on remotePeer.
func (ipsec *IPSec) InitSALocal(localPeer, remotePeer mesh.PeerName, connUID uint64, localIP, remoteIP net.IP, udpPort int, sessionKey *[32]byte) ([]byte, error) {
// ID of inbound SPI
spiID := getSPIId(remotePeer, localPeer, connUID)
ipsec.Lock()
defer ipsec.Unlock()
// Derive SA key
nonce, err := genNonce()
if err != nil {
return nil, errors.Wrap(err, "generate nonce")
}
key, err := deriveKey(sessionKey[:], nonce, localPeer)
if err != nil {
return nil, errors.Wrap(err, "derive key")
}
// Allocate SA
sa, err := netlink.XfrmStateAllocSpi(xfrmAllocSpiState(remoteIP, localIP))
if err != nil {
return nil, errors.Wrap(err, fmt.Sprintf("ip xfrm state allocspi (in, %s, %s)", remoteIP, localIP))
}
// Use SPI generated by the kernel. The kernel ensures {dstIP, spi} to
// be unique.
spi := SPI(sa.Spi)
ipsec.log.Infof("ipsec: InitSALocal: %s -> %s :%d 0x%x", remoteIP, localIP, udpPort, spi)
// Create SA
if sa, err := xfrmState(remoteIP, localIP, spi, false, key); err == nil {
if err := netlink.XfrmStateUpdate(sa); err != nil {
return nil, errors.Wrap(err, fmt.Sprintf("xfrm state update (in, %s, %s, 0x%x)", sa.Src, sa.Dst, sa.Spi))
}
} else {
return nil, errors.Wrap(err, "new xfrm state (in)")
}
// Install iptables rules
if err := ipsec.installDropNonEncrypted(localIP, remoteIP, udpPort, spi); err != nil {
return nil, errors.Wrap(err, fmt.Sprintf("install protecting rules (%s, %s, %d, 0x%x)", localIP, remoteIP, udpPort, spi))
}
si := spiInfo{spi: spi, isDirOut: false}
ipsec.spiInfo[spiID] = si
ipsec.spis[spi] = &si
// Generate the message to trigger initialization on the remote peer
msg := &msgInitSARemote{nonce, spi}
return msg.serialize(), nil
}
// InitSARemote initializes outbound ipsec to remotePeer.
// Triggered by remotePeer.
func (ipsec *IPSec) InitSARemote(msgInitSARemote []byte, localPeer, remotePeer mesh.PeerName, connUID uint64, localIP, remoteIP net.IP, udpPort int, sessionKey *[32]byte) error {
// ID of outbound SPI
spiID := getSPIId(localPeer, remotePeer, connUID)
msg, err := deserializeMsgInitSARemote(msgInitSARemote)
if err != nil {
return errors.Wrap(err, "deserialize InitSARemote")
}
spi := msg.spi
ipsec.Lock()
defer ipsec.Unlock()
ipsec.log.Infof("ipsec: InitSARemote: %s -> %s :%d 0x%x", localIP, remoteIP, udpPort, spi)
// Derive SA key by using the received nonce
key, err := deriveKey(sessionKey[:], msg.nonce, remotePeer)
if err != nil {
return errors.Wrap(err, "derive key")
}
// Create SA
if sa, err := xfrmState(localIP, remoteIP, spi, true, key); err == nil {
if err := netlink.XfrmStateAdd(sa); err != nil {
return errors.Wrap(err, fmt.Sprintf("xfrm state update (out, %s, %s, 0x%x)", sa.Src, sa.Dst, sa.Spi))
}
} else {
return errors.Wrap(err, "new xfrm state (out)")
}
// Create or update SP
sp := xfrmPolicy(localIP, remoteIP, spi)
if err := netlink.XfrmPolicyUpdate(sp); err != nil {
return errors.Wrap(err, fmt.Sprintf("xfrm policy update (%s, %s, 0x%x)", localIP, remoteIP, spi))
}
si := spiInfo{spi: spi, isDirOut: true}
ipsec.spiInfo[spiID] = si
ipsec.spis[spi] = &si
return nil
}
// Destroy destroys any (inbound / outbound) ipsec establishment between the peers.
func (ipsec *IPSec) Destroy(localPeer, remotePeer mesh.PeerName, connUID uint64, localIP, remoteIP net.IP, udpPort int) error {
outSPIID := getSPIId(localPeer, remotePeer, connUID)
inSPIID := getSPIId(remotePeer, localPeer, connUID)
ipsec.Lock()
defer ipsec.Unlock()
// Destroy inbound
if inSPIInfo, ok := ipsec.spiInfo[inSPIID]; ok {
ipsec.log.Infof("ipsec: destroy: in %s -> %s 0x%x", remoteIP, localIP, inSPIInfo.spi)
inSPI := inSPIInfo.spi
inSA := &netlink.XfrmState{
Src: remoteIP,
Dst: localIP,
Proto: netlink.XFRM_PROTO_ESP,
Spi: int(inSPI),
}
if err := netlink.XfrmStateDel(inSA); err != nil {
ipsec.log.Warnf("ipsec: xfrm state del (in, %s, %s, 0x%x) failed: %s", inSA.Src, inSA.Dst, inSA.Spi, err)
}
if err := ipsec.removeDropNonEncrypted(localIP, remoteIP, udpPort, inSPI); err != nil {
ipsec.log.Warnf("ipsec: remove protecting rules (%s, %s, %d, 0x%x) failed: %s", localIP, remoteIP, udpPort, inSPI, err)
}
delete(ipsec.spiInfo, inSPIID)
delete(ipsec.spis, inSPI)
}
// Destroy outbound
if outSPIInfo, ok := ipsec.spiInfo[outSPIID]; ok {
ipsec.log.Infof("ipsec: destroy: out %s -> %s 0x%x", localIP, remoteIP, outSPIInfo.spi)
policy, err := netlink.XfrmPolicyGet(xfrmPolicy(localIP, remoteIP, outSPIInfo.spi))
if err != nil {
ipsec.log.Warnf("ipsec: xfrm policy get (%s, %s, 0x%x) failed: %s", localIP, remoteIP, outSPIInfo.spi, err)
} else {
if len(policy.Tmpls) == 1 {
if policy.Tmpls[0].Spi == int(outSPIInfo.spi) {
if err := netlink.XfrmPolicyDel(xfrmPolicy(localIP, remoteIP, outSPIInfo.spi)); err != nil {
ipsec.log.Warnf("ipsec: xfrm policy del (%s, %s, 0x%x) failed: %s", localIP, remoteIP, outSPIInfo.spi, err)
}
} else {
ipsec.log.Debugf("ipsec: xfrm not my policy (%s, %s, 0x%x) got 0x%x ", localIP, remoteIP, outSPIInfo.spi, policy.Tmpls[0].Spi)
}
}
}
outSA := &netlink.XfrmState{
Src: localIP,
Dst: remoteIP,
Proto: netlink.XFRM_PROTO_ESP,
Spi: int(outSPIInfo.spi),
}
if err := netlink.XfrmStateDel(outSA); err != nil {
ipsec.log.Warnf("ipsec: xfrm state del (out, %s, %s, 0x%x) failed: %s", outSA.Src, outSA.Dst, outSA.Spi, err)
}
delete(ipsec.spiInfo, outSPIID)
delete(ipsec.spis, outSPIInfo.spi)
}
return nil
}
// Flush removes all policies/SAs established by us. Also, it removes chains and
// rules of iptables.
//
// If destroy is true, the chains and the rules won't be re-created.
func (ipsec *IPSec) Flush(destroy bool) error {
ipsec.Lock()
defer ipsec.Unlock()
policies, err := netlink.XfrmPolicyList(syscall.AF_INET)
if err != nil {
return errors.Wrap(err, "xfrm policy list")
}
for _, p := range policies {
if p.Mark != nil && p.Mark.Value == mark && len(p.Tmpls) != 0 {
spi := SPI(p.Tmpls[0].Spi)
if err := netlink.XfrmPolicyDel(&p); err != nil {
return errors.Wrap(err, fmt.Sprintf("xfrm policy del (%s, %s, 0x%x)", p.Src, p.Dst, spi))
}
}
}
states, err := netlink.XfrmStateList(syscall.AF_INET)
if err != nil {
return errors.Wrap(err, "xfrm state list")
}
for _, s := range states {
if _, ok := ipsec.spis[SPI(s.Spi)]; ok {
if err := netlink.XfrmStateDel(&s); err != nil {
return errors.Wrap(err, fmt.Sprintf("xfrm state list (%s, %s, 0x%x)", s.Src, s.Dst, s.Spi))
}
}
}
if err := ipsec.resetIPTables(destroy); err != nil {
return errors.Wrap(err, "reset ip tables")
}
return nil
}
// iptables
type chain struct {
table string
chain string
}
type rule struct {
table string
chain string
rulespec []string
unique bool
}
func (ipsec *IPSec) clearChains(chains []chain) error {
for _, c := range chains {
if err := ipsec.ipt.ClearChain(c.table, c.chain); err != nil {
return errors.Wrap(err, fmt.Sprintf("iptables clear chain (%s, %s)", c.table, c.chain))
}
}
return nil
}
func (ipsec *IPSec) deleteChains(chains []chain) error {
for _, c := range chains {
if err := ipsec.ipt.DeleteChain(c.table, c.chain); err != nil {
return errors.Wrap(err, fmt.Sprintf("iptables delete chain (%s, %s)", c.table, c.chain))
}
}
return nil
}
func (ipsec *IPSec) resetRules(rules []rule, destroy bool) error {
for _, r := range rules {
ok, err := ipsec.ipt.Exists(r.table, r.chain, r.rulespec...)
if err != nil {
return errors.Wrap(err, fmt.Sprintf("iptables exists rule (%s, %s, %s)", r.table, r.chain, r.rulespec))
}
switch {
case !destroy && !ok:
if err := ipsec.ipt.Append(r.table, r.chain, r.rulespec...); err != nil {
return errors.Wrap(err, fmt.Sprintf("iptables append rule (%s, %s, %s)", r.table, r.chain, r.rulespec))
}
case destroy && ok:
if err := ipsec.ipt.Delete(r.table, r.chain, r.rulespec...); err != nil {
return errors.Wrap(err, fmt.Sprintf("iptables delete rule (%s, %s, %s)", r.table, r.chain, r.rulespec))
}
}
}
return nil
}
func (ipsec *IPSec) resetIPTables(destroy bool) error {
chains := []chain{
{tableMangle, chainIn},
{tableMangle, chainInMark},
{tableFilter, chainIn},
{tableMangle, chainOut},
{tableMangle, chainOutMark},
}
rules := []rule{
{tableMangle, "INPUT", []string{"-j", chainIn}, true},
{tableMangle, chainInMark, []string{"-j", "MARK", "--set-xmark", markStr}, true},
{tableFilter, "INPUT", []string{"-j", chainIn}, true},
{tableMangle, "OUTPUT", []string{"-j", chainOut}, true},
{tableMangle, chainOutMark, []string{"-j", "MARK", "--set-xmark", markStr}, true},
{tableFilter, "OUTPUT",
[]string{
"!", "-p", "esp",
"-m", "policy", "--dir", "out", "--pol", "none",
"-m", "mark", "--mark", markStr,
"-j", "DROP"}, true},
}
if err := ipsec.clearChains(chains); err != nil {
return err
}
if err := ipsec.resetRules(rules, destroy); err != nil {
return err
}
if destroy {
if err := ipsec.deleteChains(chains); err != nil {
return err
}
}
return nil
}
func ruleMarkInboundESP(srcIP, dstIP net.IP, inSPI SPI) rule {
return rule{tableMangle, chainIn,
[]string{
"-s", dstIP.String(), "-d", srcIP.String(),
"-p", "esp",
"-m", "esp", "--espspi", "0x" + strconv.FormatUint(uint64(inSPI), 16),
"-j", chainInMark,
}, true}
}
func rulesDropNonEncrypted(srcIP, dstIP net.IP, udpPort int, inSPI SPI) []rule {
udpPortStr := strconv.FormatUint(uint64(udpPort), 10)
return []rule{
ruleMarkInboundESP(srcIP, dstIP, inSPI),
{tableFilter, chainIn,
[]string{
"-s", dstIP.String(), "-d", srcIP.String(),
"-p", "udp", "--dport", udpPortStr,
"-m", "mark", "!", "--mark", markStr,
"-j", "DROP",
}, false},
{tableMangle, chainOut,
[]string{
"-s", srcIP.String(), "-d", dstIP.String(),
"-p", "udp", "--dport", udpPortStr,
"-j", chainOutMark,
}, false},
}
}
func (ipsec *IPSec) installDropNonEncrypted(srcIP, dstIP net.IP, udpPort int, inSPI SPI) error {
rules := rulesDropNonEncrypted(srcIP, dstIP, udpPort, inSPI)
for _, r := range rules {
appendFunc := ipsec.ipt.Append
if r.unique {
appendFunc = ipsec.ipt.AppendUnique
}
if err := appendFunc(r.table, r.chain, r.rulespec...); err != nil {
return errors.Wrap(err, fmt.Sprintf("iptables append (%s, %s, %s)", r.table, r.chain, r.rulespec))
}
}
return nil
}
func (ipsec *IPSec) removeDropNonEncrypted(srcIP, dstIP net.IP, udpPort int, inSPI SPI) error {
rules := rulesDropNonEncrypted(srcIP, dstIP, udpPort, inSPI)
return ipsec.resetRules(rules, true)
}
func (ipsec *IPSec) removeDropNonEncryptedInbound(srcIP, dstIP net.IP, inSPI SPI) error {
r := ruleMarkInboundESP(srcIP, dstIP, inSPI)
if err := ipsec.ipt.Delete(r.table, r.chain, r.rulespec...); err != nil {
return errors.Wrap(err, fmt.Sprintf("iptables delete unique (%s, %s, %s)", r.table, r.chain, r.rulespec))
}
return nil
}
// xfrm
func xfrmAllocSpiState(srcIP, dstIP net.IP) *netlink.XfrmState {
return &netlink.XfrmState{
Src: srcIP,
Dst: dstIP,
Proto: netlink.XFRM_PROTO_ESP,
Mode: netlink.XFRM_MODE_TRANSPORT,
ReplayWindow: 256,
ESN: true,
}
}
func xfrmState(srcIP, dstIP net.IP, spi SPI, isDirOut bool, key []byte) (*netlink.XfrmState, error) {
if len(key) != keySize {
return nil, fmt.Errorf("key should be %d bytes long", keySize)
}
state := xfrmAllocSpiState(srcIP, dstIP)
state.Spi = int(spi)
state.Aead = &netlink.XfrmStateAlgo{
Name: "rfc4106(gcm(aes))",
Key: key,
ICVLen: 128,
}
return state, nil
}
func xfrmPolicy(srcIP, dstIP net.IP, spi SPI) *netlink.XfrmPolicy {
ipMask := []byte{0xff, 0xff, 0xff, 0xff} // /32
return &netlink.XfrmPolicy{
Src: &net.IPNet{IP: srcIP, Mask: ipMask},
Dst: &net.IPNet{IP: dstIP, Mask: ipMask},
Proto: syscall.IPPROTO_UDP,
Dir: netlink.XFRM_DIR_OUT,
Mark: &netlink.XfrmMark{
Value: mark,
Mask: mark,
},
Tmpls: []netlink.XfrmPolicyTmpl{
{
Src: srcIP,
Dst: dstIP,
Proto: netlink.XFRM_PROTO_ESP,
Mode: netlink.XFRM_MODE_TRANSPORT,
Spi: int(spi),
},
},
}
}
// Key derivation
func genNonce() ([]byte, error) {
buf := make([]byte, nonceSize)
n, err := rand.Read(buf)
if err != nil {
return nil, fmt.Errorf("crypto rand failed: %s", err)
}
if n != nonceSize {
return nil, fmt.Errorf("not enough of random data: %d", n)
}
return buf, nil
}
func deriveKey(sessionKey []byte, nonce []byte, peerName mesh.PeerName) ([]byte, error) {
key := make([]byte, keySize)
info := make([]byte, 8)
binary.BigEndian.PutUint64(info, uint64(peerName))
hkdf := hkdf.New(sha256.New, sessionKey, nonce, info)
n, err := io.ReadFull(hkdf, key)
if err != nil {
return nil, err
}
if n != keySize {
return nil, fmt.Errorf("derived too short key: %d", n)
}
return key, nil
}
// Protocol Messages
type msgInitSARemote struct {
nonce []byte
spi SPI
}
func deserializeMsgInitSARemote(b []byte) (*msgInitSARemote, error) {
if len(b) == 0 {
return nil, fmt.Errorf("empty msg")
}
msg := &msgInitSARemote{}
if len(b) != msg.size() {
return nil, fmt.Errorf("invalid payload size: %d", len(b))
}
msg.nonce = make([]byte, nonceSize)
copy(msg.nonce, b[:nonceSize])
b = b[nonceSize:]
msg.spi = SPI(binary.BigEndian.Uint32(b))
return msg, nil
}
func (msg *msgInitSARemote) size() int {
return nonceSize + 32 // SPI
}
func (msg *msgInitSARemote) serialize() []byte {
b := make([]byte, msg.size())
copy(b[:nonceSize], msg.nonce)
binary.BigEndian.PutUint32(b[nonceSize:], uint32(msg.spi))
return b
}