Permessage-deflate issue with Go's deflate

permessage_deflate_issue_poc

package main

import (
	"compress/flate"
	"encoding/hex"
	"fmt"
	"io"
	"io/ioutil"
	//	"bufio"
	"bytes"
	"os"
	"time"
)

func main() {
	gonuts_permessage_poc() //   <--- doesn't work
	//gonuts_readall_poc()   //   <--- works
}

var magic_seperator = []byte{'\r', '\n', '\r', '\n'}

func gonuts_readall_poc() {
	f, err := os.Open("flate_log.d")

	if err != nil {
		panic(err)
	}

	buf := bytes.NewBuffer(nil)

	_, err = buf.ReadFrom(f)

	if err != nil {
		panic(err)
	}

	messages := bytes.Split(buf.Bytes(), magic_seperator)

	fmt.Printf("Messages: %d\n", len(messages))

	compData := bytes.NewBuffer(nil)
	deflater := flate.NewReader(compData)

	// Unsplit into a single contiguous stream
	for _, msg := range messages {
		// msg is a single websockets message
		compData.Write(msg)
	}

	decompressed, err := ioutil.ReadAll(deflater)
	fmt.Printf("Err: %v. Decompressed:\n%s\n\n", err, hex.Dump(decompressed[0:len(decompressed)]))
}

func gonuts_permessage_poc() {
	f, err := os.Open("flate_log.d")

	if err != nil {
		panic(err)
	}

	buf := bytes.NewBuffer(nil)

	_, err = buf.ReadFrom(f)

	if err != nil {
		panic(err)
	}

	messages := bytes.Split(buf.Bytes(), magic_seperator)

	fmt.Printf("Messages: %d\n", len(messages))

	compData := bytes.NewBuffer(nil)
	deflater := flate.NewReader(compData)

	for _, msg := range messages {
		// msg is a single websockets message

		compData.Write(msg)
		decompressed, err := ioutil.ReadAll(deflater)

		fmt.Printf("Err: %v. Decompressed:\n%s\n\n", err, hex.Dump(decompressed[0:len(decompressed)]))

		if err == io.ErrUnexpectedEOF {
			// Interestingly, ignoring an unexpected EOF allows more messages to be decompressed
			// provided we use Reset here:
			deflater.(flate.Resetter).Reset(compData, nil)
			continue
		}

		if err != nil {
			break
		}

		compData.Reset()

		time.Sleep(1 * time.Second)
	}
}

Sample data: https://dl.dropboxusercontent.com/u/15643648/flate_log.d

Data was collected by dumping the payload from a series of compressed websockets messages (after appending 0x00 0x00 0xff 0xff) to a file and adding an arbitrary separater (CRLFCRLF). The traffic used permessage-deflate. The separater is used to split out the individual messages in the proof of concept code above to simulate the scenario.