cloudflared-mirror/ingress/icmp_windows.go

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//go:build windows
package ingress
/*
#include <iphlpapi.h>
#include <icmpapi.h>
*/
import "C"
import (
"context"
"encoding/binary"
"fmt"
"net/netip"
"runtime/debug"
"sync"
"syscall"
"unsafe"
"github.com/google/gopacket/layers"
"github.com/pkg/errors"
"github.com/rs/zerolog"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"github.com/cloudflare/cloudflared/packet"
)
const (
icmpEchoReplyCode = 0
)
var (
Iphlpapi = syscall.NewLazyDLL("Iphlpapi.dll")
IcmpCreateFile_proc = Iphlpapi.NewProc("IcmpCreateFile")
IcmpSendEcho_proc = Iphlpapi.NewProc("IcmpSendEcho")
echoReplySize = unsafe.Sizeof(echoReply{})
endian = binary.LittleEndian
)
// IP_STATUS code, see https://docs.microsoft.com/en-us/windows/win32/api/ipexport/ns-ipexport-icmp_echo_reply32#members
// for possible values
type ipStatus uint32
const (
success ipStatus = 0
bufTooSmall = iota + 11000
destNetUnreachable
destHostUnreachable
destProtocolUnreachable
destPortUnreachable
noResources
badOption
hwError
packetTooBig
reqTimedOut
badReq
badRoute
ttlExpiredTransit
ttlExpiredReassembly
paramProblem
sourceQuench
optionTooBig
badDestination
// Can be returned for malformed ICMP packets
generalFailure = 11050
)
func (is ipStatus) String() string {
switch is {
case success:
return "Success"
case bufTooSmall:
return "The reply buffer too small"
case destNetUnreachable:
return "The destination network was unreachable"
case destHostUnreachable:
return "The destination host was unreachable"
case destProtocolUnreachable:
return "The destination protocol was unreachable"
case destPortUnreachable:
return "The destination port was unreachable"
case noResources:
return "Insufficient IP resources were available"
case badOption:
return "A bad IP option was specified"
case hwError:
return "A hardware error occurred"
case packetTooBig:
return "The packet was too big"
case reqTimedOut:
return "The request timed out"
case badReq:
return "Bad request"
case badRoute:
return "Bad route"
case ttlExpiredTransit:
return "The TTL expired in transit"
case ttlExpiredReassembly:
return "The TTL expired during fragment reassembly"
case paramProblem:
return "A parameter problem"
case sourceQuench:
return "Datagrams are arriving too fast to be processed and datagrams may have been discarded"
case optionTooBig:
return "The IP option was too big"
case badDestination:
return "Bad destination"
case generalFailure:
return "The ICMP packet might be malformed"
default:
return fmt.Sprintf("Unknown ip status %d", is)
}
}
// https://docs.microsoft.com/en-us/windows/win32/api/ipexport/ns-ipexport-ip_option_information
type ipOption struct {
TTL uint8
Tos uint8
Flags uint8
OptionsSize uint8
OptionsData uintptr
}
// https://docs.microsoft.com/en-us/windows/win32/api/ipexport/ns-ipexport-icmp_echo_reply
type echoReply struct {
Address uint32
Status ipStatus
RoundTripTime uint32
DataSize uint16
Reserved uint16
// The pointer size defers between 32-bit and 64-bit platforms
DataPointer *byte
Options ipOption
}
type icmpProxy struct {
// An open handle that can send ICMP requests https://docs.microsoft.com/en-us/windows/win32/api/icmpapi/nf-icmpapi-icmpcreatefile
handle uintptr
logger *zerolog.Logger
// A pool of reusable *packet.Encoder
encoderPool sync.Pool
}
func newICMPProxy(listenIP netip.Addr, logger *zerolog.Logger) (ICMPProxy, error) {
handle, _, err := IcmpCreateFile_proc.Call()
// Windows procedure calls always return non-nil error constructed from the result of GetLastError.
// Caller need to inspect the primary returned value
if syscall.Handle(handle) == syscall.InvalidHandle {
return nil, errors.Wrap(err, "invalid ICMP handle")
}
return &icmpProxy{
handle: handle,
logger: logger,
encoderPool: sync.Pool{
New: func() any {
return packet.NewEncoder()
},
},
}, nil
}
func (ip *icmpProxy) Serve(ctx context.Context) error {
<-ctx.Done()
syscall.CloseHandle(syscall.Handle(ip.handle))
return ctx.Err()
}
func (ip *icmpProxy) Request(pk *packet.ICMP, responder packet.FlowResponder) error {
if pk == nil {
return errPacketNil
}
defer func() {
if r := recover(); r != nil {
ip.logger.Error().Interface("error", r).Msgf("Recover panic from sending icmp request/response, error %s", debug.Stack())
}
}()
echo, err := getICMPEcho(pk)
if err != nil {
return err
}
resp, err := ip.icmpSendEcho(pk.Dst, echo)
if err != nil {
return errors.Wrap(err, "failed to send/receive ICMP echo")
}
err = ip.handleEchoResponse(pk, echo, resp, responder)
if err != nil {
return errors.Wrap(err, "failed to handle ICMP echo reply")
}
return nil
}
func (ip *icmpProxy) handleEchoResponse(request *packet.ICMP, echoReq *icmp.Echo, resp *echoResp, responder packet.FlowResponder) error {
var replyType icmp.Type
if request.Dst.Is4() {
replyType = ipv4.ICMPTypeEchoReply
} else {
replyType = ipv6.ICMPTypeEchoReply
}
pk := packet.ICMP{
IP: &packet.IP{
Src: request.Dst,
Dst: request.Src,
Protocol: layers.IPProtocol(request.Type.Protocol()),
},
Message: &icmp.Message{
Type: replyType,
Code: icmpEchoReplyCode,
Body: &icmp.Echo{
ID: echoReq.ID,
Seq: echoReq.Seq,
Data: resp.data,
},
},
}
serializedPacket, err := ip.encodeICMPReply(&pk)
if err != nil {
return err
}
return responder.SendPacket(serializedPacket)
}
func (ip *icmpProxy) encodeICMPReply(pk *packet.ICMP) (packet.RawPacket, error) {
cachedEncoder := ip.encoderPool.Get()
defer ip.encoderPool.Put(cachedEncoder)
encoder, ok := cachedEncoder.(*packet.Encoder)
if !ok {
return packet.RawPacket{}, fmt.Errorf("encoderPool returned %T, expect *packet.Encoder", cachedEncoder)
}
return encoder.Encode(pk)
}
/*
Wrapper to call https://docs.microsoft.com/en-us/windows/win32/api/icmpapi/nf-icmpapi-icmpsendecho
Parameters:
- IcmpHandle:
- DestinationAddress: IPv4 in the form of https://docs.microsoft.com/en-us/windows/win32/api/inaddr/ns-inaddr-in_addr#syntax
- RequestData: A pointer to echo data
- RequestSize: Number of bytes in buffer pointed by echo data
- RequestOptions: IP header options
- ReplyBuffer: A pointer to the buffer for echoReply, options and data
- ReplySize: Number of bytes allocated for ReplyBuffer
- Timeout: Timeout in milliseconds to wait for a reply
Returns:
- the number of replies in uint32 https://docs.microsoft.com/en-us/windows/win32/api/icmpapi/nf-icmpapi-icmpsendecho#return-value
To retain the reference allocated objects, conversion from pointer to uintptr must happen as arguments to the
syscall function
*/
func (ip *icmpProxy) icmpSendEcho(dst netip.Addr, echo *icmp.Echo) (*echoResp, error) {
dataSize := len(echo.Data)
replySize := echoReplySize + uintptr(dataSize)
replyBuf := make([]byte, replySize)
noIPHeaderOption := uintptr(0)
inAddr, err := inAddrV4(dst)
if err != nil {
return nil, err
}
replyCount, _, err := IcmpSendEcho_proc.Call(ip.handle, uintptr(inAddr), uintptr(unsafe.Pointer(&echo.Data[0])),
uintptr(dataSize), noIPHeaderOption, uintptr(unsafe.Pointer(&replyBuf[0])),
replySize, icmpTimeoutMs)
if replyCount == 0 {
// status is returned in 5th to 8th byte of reply buffer
if status, err := unmarshalIPStatus(replyBuf[4:8]); err == nil {
return nil, fmt.Errorf("received ip status: %s", status)
}
return nil, errors.Wrap(err, "did not receive ICMP echo reply")
} else if replyCount > 1 {
ip.logger.Warn().Msgf("Received %d ICMP echo replies, only sending 1 back", replyCount)
}
return newEchoResp(replyBuf)
}
type echoResp struct {
reply *echoReply
data []byte
}
func newEchoResp(replyBuf []byte) (*echoResp, error) {
if len(replyBuf) == 0 {
return nil, fmt.Errorf("reply buffer is empty")
}
// This is pattern 1 of https://pkg.go.dev/unsafe@master#Pointer, conversion of *replyBuf to *echoReply
// replyBuf size is larger than echoReply
reply := *(*echoReply)(unsafe.Pointer(&replyBuf[0]))
if reply.Status != success {
return nil, fmt.Errorf("status %d", reply.Status)
}
dataBufStart := len(replyBuf) - int(reply.DataSize)
if dataBufStart < int(echoReplySize) {
return nil, fmt.Errorf("reply buffer size %d is too small to hold data of size %d", len(replyBuf), int(reply.DataSize))
}
return &echoResp{
reply: &reply,
data: replyBuf[dataBufStart:],
}, nil
}
// Third definition of https://docs.microsoft.com/en-us/windows/win32/api/inaddr/ns-inaddr-in_addr#syntax is address in uint32
func inAddrV4(ip netip.Addr) (uint32, error) {
if !ip.Is4() {
return 0, fmt.Errorf("%s is not IPv4", ip)
}
v4 := ip.As4()
return endian.Uint32(v4[:]), nil
}
func unmarshalIPStatus(replyBuf []byte) (ipStatus, error) {
if len(replyBuf) != 4 {
return 0, fmt.Errorf("ipStatus needs to be 4 bytes, got %d", len(replyBuf))
}
return ipStatus(endian.Uint32(replyBuf)), nil
}