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qilib.go
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qilib.go
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// Package qilib contains the necessary structs and funcs to create sniffing sessions detecting
// quantum injection attacks.
package qilib
import (
"bytes"
"fmt"
"io/ioutil"
"math"
"net"
"os"
"time"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"github.com/zond/qisniff/blocks"
)
const (
cleanInterval = time.Minute * 10
)
// A difference detected.
type Diff struct {
A []byte
B []byte
Seq uint32
ID StreamID
}
// The public representation of a stream.
type StreamID struct {
SrcIP net.IP
DstIP net.IP
SrcPort layers.TCPPort
DstPort layers.TCPPort
}
func (i StreamID) String() string {
return fmt.Sprintf("%v:%v->%v:%v", i.SrcIP, i.SrcPort, i.DstIP, i.DstPort)
}
// The internal representation of a stream - uses strings addresses to be hashable.
// Only contains the parts of the 5-tuple that are relevant (we only look at TCP anyway).
type streamID struct {
srcIP string
dstIP string
srcPort layers.TCPPort
dstPort layers.TCPPort
}
func (i streamID) String() string {
return i.toStreamID().String()
}
func (i streamID) toStreamID() StreamID {
return StreamID{
SrcIP: net.IP(i.srcIP),
DstIP: net.IP(i.dstIP),
SrcPort: i.srcPort,
DstPort: i.dstPort,
}
}
// The actual stream.
type stream struct {
session *Session
id *streamID
f *os.File
// What to add to the sequence number to get the byte range this packet affects.
offset int64
// The last sequence number, to know when they wrap.
lastSeq uint32
// The data we have received so far.
done blocks.Blocks
lastAccess time.Time
}
func newStream(sess *Session, id *streamID, seq uint32) (*stream, error) {
f, err := ioutil.TempFile(os.TempDir(), "qisniff")
if err != nil {
return nil, err
}
return &stream{
session: sess,
id: id,
f: f,
offset: -int64(seq),
lastSeq: seq,
}, nil
}
func (s *stream) clean() error {
if err := s.f.Close(); err != nil {
return err
}
if err := os.Remove(s.f.Name()); err != nil {
return err
}
return nil
}
func (s *stream) write(pkt gopacket.Packet, tcp *layers.TCP) error {
// Empty SYN and FIN packets will increment the sequence number without incrementing
// the data pointer, so lets decrement the data pointer ourselves.
if (tcp.SYN || tcp.FIN) && len(tcp.Payload) == 0 {
s.offset--
}
// If the last sequence number is in the upper quarter of the name space, and the current
// on in the lower, add the name space size to the offset because now we have wrapped.
if s.lastSeq > (math.MaxUint32-math.MaxUint32/4) && tcp.Seq < math.MaxUint32/4 {
s.offset += math.MaxUint32
}
// The range this packet writes is defined by its secquence number and length.
a := s.offset + int64(tcp.Seq)
b := a + int64(len(tcp.Payload))
// If it has length, and the packet isn't a one-zero-byte-keepalive packet (length 1, ACK, payload == [0]).
if b > a && (b-a != 1 || !tcp.ACK || tcp.Payload[0] != 0) {
// Check if this range is something we have seen before.
for _, overlap := range s.done.Overlaps(a, b) {
// Allocate, seek and load the data from our file.
previous := make([]byte, overlap.B-overlap.A)
if _, err := s.f.Seek(overlap.A, 0); err != nil {
return err
}
if _, err := s.f.Read(previous); err != nil {
return err
}
// Find the relative indices in this packet to compare this data with.
relStart := int64(0)
relEnd := int64(len(tcp.Payload))
if overlap.A > a {
relStart += overlap.A - a
}
if overlap.B-overlap.A < int64(len(tcp.Payload)) {
relEnd = relStart + (overlap.B - overlap.A)
}
relPayload := tcp.Payload[relStart:relEnd]
// If they aren't equal, add it to the diffs.
if bytes.Compare(previous, relPayload) != 0 {
if s.session.Warning != nil {
s.session.Warning(pkt, Diff{
A: previous,
B: relPayload,
Seq: tcp.Seq,
ID: s.id.toStreamID(),
})
}
}
}
// Seek and write the data.
if _, err := s.f.Seek(a, 0); err != nil {
return fmt.Errorf("Seek(%v, 0): %v", a, err)
}
if _, err := s.f.Write(tcp.Payload); err != nil {
return fmt.Errorf("Write(%v): %v", tcp.Payload, err)
}
s.done = s.done.Add(a, b)
}
return nil
}
// The parameters to create a new Session.
type Config struct {
// The source of packets.
Handle *pcap.Handle
// Progress indicator.
Progress func(pkt gopacket.Packet)
// Warning indicator.
Warning func(pkt gopacket.Packet, diff Diff)
// Unparseable packet indicator.
Unparseable func(pkt gopacket.Packet)
}
// Session encapsulates a sniffing session.
type Session struct {
Config
srcIP net.IP
dstIP net.IP
eth layers.Ethernet
ip4 layers.IPv4
ip6 layers.IPv6
tcp layers.TCP
payload gopacket.Payload
decoded []gopacket.LayerType
isTCP bool
err error
pkt gopacket.Packet
source *gopacket.PacketSource
parser *gopacket.DecodingLayerParser
sID *streamID
strm *stream
found bool
streams map[streamID]*stream
nextCleaning time.Time
}
func NewSession(c Config) *Session {
s := &Session{
Config: c,
streams: map[streamID]*stream{},
nextCleaning: time.Now().Add(cleanInterval),
}
s.source = gopacket.NewPacketSource(s.Handle, s.Handle.LinkType())
s.parser = gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet, &s.eth, &s.ip4, &s.ip6, &s.tcp, &s.payload)
return s
}
// Clean will remove all created tempfiles.
func (s *Session) Clean() error {
for id, strm := range s.streams {
if s.err = strm.clean(); s.err != nil {
return s.err
}
delete(s.streams, id)
}
return nil
}
// Run goes through all packets in the source.
func (s *Session) Run() error {
for packet := range s.source.Packets() {
s.pkt = packet
if s.err = s.handle(); s.err != nil {
return s.err
}
}
return nil
}
// Next looks at the next packet in the source.
func (s *Session) Next() error {
if s.pkt, s.err = s.source.NextPacket(); s.err != nil {
return s.err
}
return s.handle()
}
func (s *Session) handle() error {
if s.Progress != nil {
s.Progress(s.pkt)
}
if s.err = s.parser.DecodeLayers(s.pkt.Data(), &s.decoded); s.err != nil {
if s.Unparseable != nil {
s.Unparseable(s.pkt)
}
return nil
}
s.isTCP = false
for _, typ := range s.decoded {
switch typ {
case layers.LayerTypeIPv4:
s.srcIP = s.ip4.SrcIP
s.dstIP = s.ip4.DstIP
case layers.LayerTypeIPv6:
s.srcIP = s.ip6.SrcIP
s.dstIP = s.ip6.DstIP
case layers.LayerTypeTCP:
s.isTCP = true
}
}
if s.isTCP {
s.sID = &streamID{
srcIP: string(s.srcIP),
dstIP: string(s.dstIP),
srcPort: s.tcp.SrcPort,
dstPort: s.tcp.DstPort,
}
s.strm, s.found = s.streams[*s.sID]
if s.found || s.tcp.SYN {
if s.tcp.SYN {
if s.found {
// Clean the old stream, this is a new one.
if s.err = s.strm.clean(); s.err != nil {
return s.err
}
}
if s.strm, s.err = newStream(s, s.sID, s.tcp.Seq); s.err != nil {
return s.err
}
s.streams[*s.sID] = s.strm
}
if s.err = s.strm.write(s.pkt, &s.tcp); s.err != nil {
return s.err
}
s.strm.lastAccess = time.Now()
}
}
if time.Now().After(s.nextCleaning) {
s.nextCleaning = time.Now().Add(cleanInterval)
for id, strm := range s.streams {
if strm.lastAccess.Add(cleanInterval).Before(time.Now()) {
if s.err = strm.clean(); s.err != nil {
return s.err
}
delete(s.streams, id)
}
}
}
return nil
}