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package main
import (
"bytes"
"github.com/flier/gohs/hyperscan"
"github.com/google/gopacket/tcpassembly"
log "github.com/sirupsen/logrus"
"time"
)
const MaxDocumentSize = 1024 * 1024
const InitialBlockCount = 1024
const InitialPatternSliceSize = 8
// IMPORTANT: If you use a StreamHandler, you MUST read ALL BYTES from it,
// quickly. Not reading available bytes will block TCP stream reassembly. It's
// a common pattern to do this by starting a goroutine in the factory's New
// method:
type StreamHandler struct {
connection ConnectionHandler
streamFlow StreamFlow
buffer *bytes.Buffer
indexes []int
timestamps []time.Time
lossBlocks []bool
currentIndex int
firstPacketSeen time.Time
lastPacketSeen time.Time
documentsIDs []RowID
streamLength int
packetsCount int
patternStream hyperscan.Stream
patternMatches map[uint][]PatternSlice
scanner Scanner
}
// NewReaderStream returns a new StreamHandler object.
func NewStreamHandler(connection ConnectionHandler, streamFlow StreamFlow, scanner Scanner) StreamHandler {
handler := StreamHandler{
connection: connection,
streamFlow: streamFlow,
buffer: new(bytes.Buffer),
indexes: make([]int, 0, InitialBlockCount),
timestamps: make([]time.Time, 0, InitialBlockCount),
lossBlocks: make([]bool, 0, InitialBlockCount),
documentsIDs: make([]RowID, 0, 1), // most of the time the stream fit in one document
patternMatches: make(map[uint][]PatternSlice, connection.PatternsDatabaseSize()),
scanner: scanner,
}
stream, err := connection.PatternsDatabase().Open(0, scanner.scratch, handler.onMatch, nil)
if err != nil {
log.WithField("streamFlow", streamFlow).WithError(err).Error("failed to create a stream")
}
handler.patternStream = stream
return handler
}
// Reassembled implements tcpassembly.Stream's Reassembled function.
func (sh *StreamHandler) Reassembled(reassembly []tcpassembly.Reassembly) {
for _, r := range reassembly {
sh.packetsCount++
skip := r.Skip
if r.Start {
skip = 0
sh.firstPacketSeen = r.Seen
}
if r.End {
sh.lastPacketSeen = r.Seen
}
reassemblyLen := len(r.Bytes)
if reassemblyLen == 0 {
continue
}
if sh.buffer.Len()+len(r.Bytes)-skip > MaxDocumentSize {
sh.storageCurrentDocument()
sh.resetCurrentDocument()
}
n, err := sh.buffer.Write(r.Bytes[skip:])
if err != nil {
log.WithError(err).Error("failed to copy bytes from a Reassemble")
continue
}
sh.indexes = append(sh.indexes, sh.currentIndex)
sh.timestamps = append(sh.timestamps, r.Seen)
sh.lossBlocks = append(sh.lossBlocks, skip != 0)
sh.currentIndex += n
sh.streamLength += n
if sh.patternStream != nil {
err = sh.patternStream.Scan(r.Bytes)
if err != nil {
log.WithError(err).Error("failed to scan packet buffer")
}
}
}
}
// ReassemblyComplete implements tcpassembly.Stream's ReassemblyComplete function.
func (sh *StreamHandler) ReassemblyComplete() {
if sh.patternStream != nil {
err := sh.patternStream.Close()
if err != nil {
log.WithError(err).Error("failed to close pattern stream")
}
}
if sh.currentIndex > 0 {
sh.storageCurrentDocument()
}
sh.connection.Complete(sh)
}
func (sh *StreamHandler) resetCurrentDocument() {
sh.buffer.Reset()
sh.indexes = sh.indexes[:0]
sh.timestamps = sh.timestamps[:0]
sh.lossBlocks = sh.lossBlocks[:0]
sh.currentIndex = 0
for _, val := range sh.patternMatches {
val = val[:0]
}
}
func (sh *StreamHandler) onMatch(id uint, from uint64, to uint64, _ uint, _ interface{}) error {
patternSlices, isPresent := sh.patternMatches[id]
if isPresent {
if len(patternSlices) > 0 {
lastElement := &patternSlices[len(patternSlices)-1]
if lastElement[0] == from { // make the regex greedy to match the maximum number of chars
lastElement[1] = to
return nil
}
}
// new from == new match
sh.patternMatches[id] = append(patternSlices, PatternSlice{from, to})
} else {
patternSlices = make([]PatternSlice, 1, InitialPatternSliceSize)
patternSlices[0] = PatternSlice{from, to}
sh.patternMatches[id] = patternSlices
}
return nil
}
func (sh *StreamHandler) storageCurrentDocument() {
payload := sh.streamFlow.Hash()&uint64(0xffffffffffffff00) | uint64(len(sh.documentsIDs)) // LOL
streamID := sh.connection.Storage().NewCustomRowID(payload, sh.firstPacketSeen)
_, err := sh.connection.Storage().Insert(ConnectionStreams).
One(ConnectionStream{
ID: streamID,
ConnectionID: ZeroRowID,
DocumentIndex: len(sh.documentsIDs),
Payload: sh.buffer.Bytes(),
BlocksIndexes: sh.indexes,
BlocksTimestamps: sh.timestamps,
BlocksLoss: sh.lossBlocks,
PatternMatches: sh.patternMatches,
})
if err != nil {
log.WithError(err).Error("failed to insert connection stream")
} else {
sh.documentsIDs = append(sh.documentsIDs, streamID)
}
}
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