Bren2010/HearSay.md

## hearsay.coffee
fs           = require 'fs'
net          = require 'net'
path         = require 'path'
async        = require 'async'
crypto       = require 'crypto'
readline     = require 'readline'
msgpack      = require 'msgpack'
secure       = require './secure'
{BigInteger} = require 'bigdecimal'

# Network state
# Server information
[peers, pendingHookups, pendingDownloads, chunks] = [{}, {}, {}, {}]
[peersLength, chunksLength, serverPort] = [0, 0, 0]
routingKey = secure.randomHex()

console.log 'Hearsay File Sharer v0.0.1'
console.log 'Starting up...'

# Start the server.  Handles inter-cluster requests.  (Insecure)
server = net.createServer (conn) ->
    conn.once 'data', (data) =>
        data = data.toString().split ' '
        switch data[0]
            when 'hookup'
                address = conn.remoteAddress + ':' + data[1]
                conn.end()

                # 1.  Check that given port is valid.
                # 2.  Decide if we want this connection for ourselves.
                # 3.  Make sure we don't know this peer.
                # 4.  Make sure this isn't one of ours.
                port = parseInt data[1]
                want = secure.want peersLength
                know = peers[address]?
                ours = pendingHookups[data[2]]?

                if not isNaN(port) and want and not know and not ours
                    # Connect and befriend.
                    conn = net.connect data[1], conn.remoteAddress, ->
                        conn.write 'mate ' + serverPort + ' ' + data[2]

                    conn.once 'data', (res) ->
                        if res.toString() is 'ok' then peer conn, data[1], true

                    conn.on 'error', ->

                else if not isNaN port and not ours
                    # Pass on.
                    drain.push cmd: 'hookup', address: address, tracker: data[2]

            when 'mate'
                # If ours, acknowledge.  If not, throw away.
                if pendingHookups[data[2]]?
                    delete pendingHookups[data[2]]
                    conn.write 'ok'
                    peer conn, data[1], false
                else
                    conn.end 'no'

    # So there's never an 'unhandeled' error.
    conn.on 'error', ->

server.listen ->
    serverPort = server.address().port

    console.log 'Server port:', serverPort
    frontend()


# Peers
drainer = (task, done) ->
    if peersLength is 0 then return
    cb = task.cb
    delete task.cb

    if (task.cmd is 'req' or task.cmd is 'res') and task.from?
        # Hash tracker
        c = crypto.createCipher 'aes-256-ctr', routingKey
        c.end task.tracker, 'hex'
        tracker = c.read().toString 'hex'

        # Generate lists of peers to reference.
        first = (addr for addr of peers).sort()
        second = (addr for addr of peers).sort (a, b) ->
            c = crypto.createCipher 'aes-256-ctr', routingKey
            c.write tracker, 'hex'
            c.end a
            a = c.read().toString 'hex'

            c = crypto.createCipher 'aes-256-ctr', routingKey
            c.write tracker, 'hex'
            c.end b
            b = c.read().toString 'hex'

            a > b

        if task.cmd is 'res' then [first, second] = [second, first]

        # Choose next.
        n = first.indexOf task.from
        delete task.from
        addr = second[n]
    else
        # Randomly choose peer.
        [n, m] = [secure.random(peersLength), 0]
        for addr of peers
            if n is m then break else m++

    # Encrypt.
    peers[addr].writeCipher.write msgpack.pack task
    ct = peers[addr].writeCipher.read().toString 'base64'

    # MAC.
    mac = crypto.createHmac 'sha256', peers[addr].writeMACKey
    mac.end ct, 'base64'
    tag = mac.read().toString 'base64'

    peers[addr].conn.write ct + tag + '\n', 'utf8', (err) ->
        if cb? then cb err
        done err

drain = async.queue drainer, 1

peer = (conn, port, init) ->
    # Secure the connection.
    secure.remote conn, init
    address = conn.remoteAddress + ':' + port

    conn.on 'secure', (writeCipher, writeMKey) ->
        peersLength++
        peers[address] =
            conn: conn
            writeCipher: writeCipher
            writeMACKey: writeMKey

    conn.on 'end', ->
        peersLength--
        delete peers[address]

    conn.on 'line', (data) ->
        if data.cmd is 'hookup' and data.address? and data.tracker?
            want = secure.want peersLength
            know = peers[data.address]?
            ours = pendingHookups[data.tracker]?
            [host, port] = data.address.split ':'

            if want and not know and not ours
                # Connect and befriend.
                conn = net.connect port, host, ->
                    conn.write 'mate ' + serverPort + ' ' + data.tracker

                conn.once 'data', (res) ->
                    if res.toString() is 'ok' then peer conn, port, true

                conn.on 'error', ->

            else if not ours and not secure.drop()
                drain.push data

        else if data.cmd is 'distr' and data.tag? and data.chunk?
            know = chunks[data.tag]?

            if secure.want() and not know
                chunks[data.tag] = data: data.chunk, own: false
                chunksLength++

            if not secure.drop() then drain.push data

        else if data.cmd is 'req' and data.tracker? and data.tag?
            if chunks[data.tag]?
                drain.push {
                    cmd: 'res',
                    tracker: data.tracker,
                    chunk: chunks[data.tag].data
                }

            else if not secure.drop()
                drain.push data

        else if data.cmd is 'res' and data.tracker? and data.chunk?
            if pendingDownloads[data.tracker]?
                pendingDownloads[data.tracker](data.chunk)
            else if not secure.drop()
                drain.push data

# General maintenance.
maintenance = ->
    # Clean up old hookups.
    d = (new Date()).getTime()

    clean = (tracker) ->
        if d - pendingHookups[tracker] >= 5000
            delete pendingHookups[tracker]

    clean tracker for tracker of pendingHookups

    # Clean out unwanted chunks.
    clean = (tag) ->
        if chunks[tag].own is false and secure.drop()
            delete chunks[tag]

    clean tag for tag of chunks

    # Play matchmaker.
    if peersLength is 0 or peersLength >= 5 then return
    [n, m] = [secure.random(peersLength), 0]
    for addr of peers
        if n is m then break
        m++

    [host, port] = addr.split ':'
    conn = net.connect port, host, ->
        d = new Date()
        tracker = secure.randomHex()
        pendingHookups[tracker] = d.getTime()
        conn.end 'hookup ' + serverPort + ' ' + tracker

    conn.on 'error', ->

setInterval maintenance, 5000

publish = () ->
    if peersLength is 0 then return setTimeout publish, 10000

    # Publish chunks.
    args = ({tag: tag, chunk: chunk} for tag, chunk of chunks)
    pub = (item, done) ->
        drain.push cmd: 'distr', tag: item.tag, chunk: item.chunk.data, cb: ->
            setTimeout done, Math.random() * 50000

    async.mapSeries args, pub, -> setTimeout publish, 10000

publish()

# Command Line Interface
frontend = ->
    # Completion service.
    completer = (line) ->
        [completions, hits] = [[], []]

        line = path.normalize line
        [p, n] = [path.dirname(line), path.basename(line)]
        exists = fs.existsSync p

        completions = if exists then fs.readdirSync p else []

        hits = completions.filter (c) -> c.indexOf(n) is 0

        if hits.length is 1
            h = hits[0]
            hits[0] = p
            hits[0] += if p[p.length - 1] is path.sep then '' else path.sep
            hits[0] += h

            stats = fs.statSync hits[0]
            if stats.isDirectory() then hits[0] += path.sep

        rec = if hits.length > 0 then hits else completions
        return [rec, line]

    # Create interface.
    rl = readline.createInterface {
        input: process.stdin
        output: process.stdout
        completer: completer
    }

    # Parses and handles lines entered by the user.
    rl.on 'line', (line) ->
        line = line.trim().split ' '

        switch line[0]
            when "" then console.log ""
            when "chunks"
                console.log tag for tag of chunks

            when "peers"
                console.log addr for addr, _ of peers
                if peersLength is 0 then console.log 'No peers.'

            when "enter"
                if line.length isnt 3 then return rl.prompt true
                conn = net.connect line[2], line[1], ->
                    d = new Date()
                    tracker = secure.randomHex()
                    pendingHookups[tracker] = d.getTime()
                    conn.end 'hookup ' + serverPort + ' ' + tracker

                end = (error) =>
                    if error? then console.log error
                    rl.prompt true

                conn.on 'error', end
                conn.on 'end', end

            when "upload"
                if line.length isnt 1 then return rl.prompt true
                readChunk = (inFd, outFd, cipher) ->
                    buff = new Buffer 262144
                    fs.read inFd, buff, 0, 262144, null, (err, n, buff) ->
                        if err isnt null or n is 0
                            return rl.prompt true

                        # Encrypt chunk.
                        cipher.write buff.slice(0, n)
                        chunk = cipher.read()

                        # Hash encrypted chunk.
                        h = crypto.createHash 'sha256'
                        h.end chunk
                        tag = h.read().toString 'base64'

                        # Publish
                        chunks[tag] = data: chunk.toJSON(), ours: true
                        chunksLength++

                        tb = new Buffer tag
                        fs.write outFd, tb, 0, tb.length, null, ->
                            readChunk inFd, outFd, cipher

                # Get files needed, open them, and prepare for uploading.
                questions = [
                    {ask: 'Input file? ', mode: 'r'},
                    {ask: 'Output file? ', mode: 'w'},
                ]

                openFile = (task, done) ->
                    rl.question task.ask, (file) ->
                        fs.open file, task.mode, null, done

                async.mapSeries questions, openFile, (err, fds) ->
                    if err?
                        console.log err
                        rl.prompt true
                    else
                        key = secure.randomBase64()
                        kb = new Buffer key
                        fs.write fds[1], kb, 0, kb.length, null, ->
                            c = crypto.createCipher 'aes-256-ctr', key
                            readChunk fds[0], fds[1], c

                return

            when "download"
                if line.length isnt 1 then return rl.prompt true

                nextLine = (fd, cb) ->
                    buff = new Buffer 44
                    fs.read fd, buff, 0, 44, null, (err, n, buff) ->
                        if err is null and n is 44
                            cb buff.toString()
                        else
                            cb()

                timeout = (tracker) ->
                    if not pendingDownloads[tracker]? then return
                    pendingDownloads[tracker]('timeout')

                fetchChunk = (inFd, outFd, cipher, tag) ->
                    if not tag? then return rl.prompt true

                    # Choose a random tracker, put it as pending, and send a
                    # request with it.
                    tracker = secure.randomHex()
                    pendingDownloads[tracker] = (chunk) ->
                        if chunk is 'timeout'
                            # Timed out waiting for this chunk.
                            # Add limiters here later.
                            delete pendingDownloads[tracker]
                            fetchChunk inFd, outFd, cipher, tag
                        else
                            chunk = new Buffer chunk

                            # Hash encrypted chunk to check integrity.
                            h = crypto.createHash 'sha256'
                            h.end chunk
                            candidateTag = h.read().toString 'base64'

                            if tag isnt candidateTag then return
                            delete pendingDownloads[tracker]

                            # Decrypt chunk.
                            cipher.write chunk
                            chunk = cipher.read()

                            # Output, and get next chunk.
                            fs.write outFd, chunk, 0, chunk.length, null, ->
                                nextLine inFd, (tag) ->
                                    fetchChunk inFd, outFd, cipher, tag

                    drain.push cmd: 'req', tracker: tracker, tag: tag
                    setTimeout timeout, 5000, tracker

                # Get files needed, open them, and prepare for downloading.
                questions = [
                    {ask: 'Input file? ', mode: 'r'},
                    {ask: 'Output file? ', mode: 'w'},
                ]

                openFile = (task, done) ->
                    rl.question task.ask, (file) ->
                        fs.open file, task.mode, null, done

                async.mapSeries questions, openFile, (err, fds) ->
                    if err?
                        console.log err
                        rl.prompt true
                    else
                        nextLine fds[0], (key) ->
                            c = crypto.createCipher 'aes-256-ctr', key
                            nextLine fds[0], (tag) ->
                                fetchChunk fds[0], fds[1], c, tag

                return

            else console.log 'Command not known.'

        rl.prompt true

    rl.on 'close', ->
        console.log '\nGoodbye'
        process.exit 0

    rl.prompt true

## HearSay.md

      
    Raw
  

              HearSay.md
            
          
    HearSay

The HearSay P2P File Sharer; a response to The Copyright Alert System, as well
as several other internet regulation attempts.  The goal of this project is to
prove the viability of semi-anonymous and confidential file sharing.  Consists
of several proofs of concepts such as the formation of ad-hoc mix networks and
routing throughout them while maintaining anonymity and semantic security.
However, lets be honest with ourselves for a second.  Don't use this to fight an
oppressive regime.  I can not (and will not try) to 'prove' its security, and I
have no idea how this system will perform under high stress or in large
clusters.  All of this code is simply the product of basic cryptographic research
and application.

Beware of bugs in the [below] code; I have only proved it correct, not tried it.  ~ Donald Knuth

Setup


Dependencies:  Node.js, npm
Installation:  npm install  (May require sudo.)
Start:  coffee hearsay  (Never run with sudo.)

Usage


chunks - Lists the hashes of all the chunks you are currently hosting.  These consist of the chunks you've uploaded as well as the chunks that you're co-hosting.
peers - Lists all of the peers on a network that you're currently connected to.
enter {host} {port} - Attempts to enter a cluster through the given node.  This requires that your server be publicly available as well.  (Through the use of port forwarding, or a DMZ.)
upload - Will then prompt you for an input file (the file to be uploaded) and an output file (where the torrent data will be written), and upload the input file to the cluster.
download - Will then prompt you for an input file (the file with the torrent data) and an output file (where the file contents will be written), and attempt to download the file.

To Do


Allow a public organization to sponsor uploads to a network without being legally responsible for them.
Re-uploads
Limiting number of failed requests before giving up.
Requesting a specific port for the server to listen on.
Cleaning, perhaps?


## package.json
{
  "name": "HearSay",
  "version": "0.0.1",
  "private": true,
  "dependencies": {
    "coffee-script": "*",
    "bigdecimal": "*",
    "async": "*",
    "msgpack": "*",
    "event-stream": "*"
  }
}

## secure.coffee
es           = require 'event-stream'
crypto       = require 'crypto'
msgpack      = require 'msgpack'
{BigInteger} = require 'bigdecimal'
salt = 'vpfSIDPgJ5tBt7gZgnGQeG8G6r0q4fDkDWWtZD7zqAsYWw2Ep81vIjqC3gJM'

exports.remote = (conn, init) ->
    dh = crypto.getDiffieHellman 'modp14'
    dh.generateKeys()

    conn.write dh.getPublicKey 'hex'
    conn.once 'data', (data) ->
        # Generate keys.
        secret = dh.computeSecret data.toString(), 'hex', 'hex'
        key = crypto.pbkdf2Sync secret, salt, 2048, 128

        [readCKey, readMKey] = [key.slice(0, 32), key.slice(32, 64)]
        [writeCKey, writeMKey] = [key.slice(64, 96), key.slice(96, 128)]

        if init
            [readCKey, writeCKey] = [writeCKey, readCKey]
            [readMKey, writeMKey] = [writeMKey, readMKey]

        readCipher  = crypto.createDecipher 'aes-256-ctr', readCKey
        writeCipher = crypto.createCipher 'aes-256-ctr', writeCKey

        # Begin handling input.
        handle = (line, cb) ->
            # Decrypt and validate.
            ct = line.slice 0, line.length - 44
            tag = line.slice line.length - 44

            readCipher.write ct, 'base64'
            pt = msgpack.unpack readCipher.read()

            readMAC = crypto.createHmac 'sha256', readMKey
            readMAC.end ct, 'base64'
            candidateTag = readMAC.read().toString 'base64'
            if candidateTag != tag then return conn.end()

            # Handle data.
            conn.emit 'line', pt
            cb null, null

        p = es.pipeline conn, es.split(), es.map handle
        p.on 'error', ->
        conn.emit 'secure', writeCipher, writeMKey

# Probabilistically decides if we 'want' something.
exports.want = (n) ->
    a = BigInteger('3', 10).pow(n)
    b = BigInteger('4', 10).pow(n)
    r = crypto.randomBytes(2).toString('hex')
    x = BigInteger(r, 16).remainder(b)

    if x.compareTo(a) is 1 then false else true

# Probablistically decides if we should drop a packet.
exports.drop = ->
    x = exports.random 10
    if x is 2 then true else false

# Choose a random number in the range [0, max)
exports.random = (max) ->
    max = BigInteger max.toString(), 10
    n = Math.ceil(((Math.log(max) / Math.log(2)) + 1) / 8)
    r = crypto.randomBytes(n).toString('hex')
    x = BigInteger(r, 16).remainder(max)

    (Number) x

# Returns a string of random hex.
exports.randomHex = (n = 32) -> crypto.randomBytes(n).toString 'hex'
exports.randomBase64 = (n = 32) -> crypto.randomBytes(n).toString 'base64'
	fs = require 'fs'
	net = require 'net'
	path = require 'path'
	async = require 'async'
	crypto = require 'crypto'
	readline = require 'readline'
	msgpack = require 'msgpack'
	secure = require './secure'
	{BigInteger} = require 'bigdecimal'

	# Network state
	# Server information
	[peers, pendingHookups, pendingDownloads, chunks] = [{}, {}, {}, {}]
	[peersLength, chunksLength, serverPort] = [0, 0, 0]
	routingKey = secure.randomHex()

	console.log 'Hearsay File Sharer v0.0.1'
	console.log 'Starting up...'

	# Start the server. Handles inter-cluster requests. (Insecure)
	server = net.createServer (conn) ->
	conn.once 'data', (data) =>
	data = data.toString().split ' '
	switch data[0]
	when 'hookup'
	address = conn.remoteAddress + ':' + data[1]
	conn.end()

	# 1. Check that given port is valid.
	# 2. Decide if we want this connection for ourselves.
	# 3. Make sure we don't know this peer.
	# 4. Make sure this isn't one of ours.
	port = parseInt data[1]
	want = secure.want peersLength
	know = peers[address]?
	ours = pendingHookups[data[2]]?

	if not isNaN(port) and want and not know and not ours
	# Connect and befriend.
	conn = net.connect data[1], conn.remoteAddress, ->
	conn.write 'mate ' + serverPort + ' ' + data[2]

	conn.once 'data', (res) ->
	if res.toString() is 'ok' then peer conn, data[1], true

	conn.on 'error', ->

	else if not isNaN port and not ours
	# Pass on.
	drain.push cmd: 'hookup', address: address, tracker: data[2]

	when 'mate'
	# If ours, acknowledge. If not, throw away.
	if pendingHookups[data[2]]?
	delete pendingHookups[data[2]]
	conn.write 'ok'
	peer conn, data[1], false
	else
	conn.end 'no'

	# So there's never an 'unhandeled' error.
	conn.on 'error', ->

	server.listen ->
	serverPort = server.address().port

	console.log 'Server port:', serverPort
	frontend()


	# Peers
	drainer = (task, done) ->
	if peersLength is 0 then return
	cb = task.cb
	delete task.cb

	if (task.cmd is 'req' or task.cmd is 'res') and task.from?
	# Hash tracker
	c = crypto.createCipher 'aes-256-ctr', routingKey
	c.end task.tracker, 'hex'
	tracker = c.read().toString 'hex'

	# Generate lists of peers to reference.
	first = (addr for addr of peers).sort()
	second = (addr for addr of peers).sort (a, b) ->
	c = crypto.createCipher 'aes-256-ctr', routingKey
	c.write tracker, 'hex'
	c.end a
	a = c.read().toString 'hex'

	c = crypto.createCipher 'aes-256-ctr', routingKey
	c.write tracker, 'hex'
	c.end b
	b = c.read().toString 'hex'

	a > b

	if task.cmd is 'res' then [first, second] = [second, first]

	# Choose next.
	n = first.indexOf task.from
	delete task.from
	addr = second[n]
	else
	# Randomly choose peer.
	[n, m] = [secure.random(peersLength), 0]
	for addr of peers
	if n is m then break else m++

	# Encrypt.
	peers[addr].writeCipher.write msgpack.pack task
	ct = peers[addr].writeCipher.read().toString 'base64'

	# MAC.
	mac = crypto.createHmac 'sha256', peers[addr].writeMACKey
	mac.end ct, 'base64'
	tag = mac.read().toString 'base64'

	peers[addr].conn.write ct + tag + '\n', 'utf8', (err) ->
	if cb? then cb err
	done err

	drain = async.queue drainer, 1

	peer = (conn, port, init) ->
	# Secure the connection.
	secure.remote conn, init
	address = conn.remoteAddress + ':' + port

	conn.on 'secure', (writeCipher, writeMKey) ->
	peersLength++
	peers[address] =
	conn: conn
	writeCipher: writeCipher
	writeMACKey: writeMKey

	conn.on 'end', ->
	peersLength--
	delete peers[address]

	conn.on 'line', (data) ->
	if data.cmd is 'hookup' and data.address? and data.tracker?
	want = secure.want peersLength
	know = peers[data.address]?
	ours = pendingHookups[data.tracker]?
	[host, port] = data.address.split ':'

	if want and not know and not ours
	# Connect and befriend.
	conn = net.connect port, host, ->
	conn.write 'mate ' + serverPort + ' ' + data.tracker

	conn.once 'data', (res) ->
	if res.toString() is 'ok' then peer conn, port, true

	conn.on 'error', ->

	else if not ours and not secure.drop()
	drain.push data

	else if data.cmd is 'distr' and data.tag? and data.chunk?
	know = chunks[data.tag]?

	if secure.want() and not know
	chunks[data.tag] = data: data.chunk, own: false
	chunksLength++

	if not secure.drop() then drain.push data

	else if data.cmd is 'req' and data.tracker? and data.tag?
	if chunks[data.tag]?
	drain.push {
	cmd: 'res',
	tracker: data.tracker,
	chunk: chunks[data.tag].data
	}

	else if not secure.drop()
	drain.push data

	else if data.cmd is 'res' and data.tracker? and data.chunk?
	if pendingDownloads[data.tracker]?
	pendingDownloads[data.tracker](data.chunk)
	else if not secure.drop()
	drain.push data

	# General maintenance.
	maintenance = ->
	# Clean up old hookups.
	d = (new Date()).getTime()

	clean = (tracker) ->
	if d - pendingHookups[tracker] >= 5000
	delete pendingHookups[tracker]

	clean tracker for tracker of pendingHookups

	# Clean out unwanted chunks.
	clean = (tag) ->
	if chunks[tag].own is false and secure.drop()
	delete chunks[tag]

	clean tag for tag of chunks

	# Play matchmaker.
	if peersLength is 0 or peersLength >= 5 then return
	[n, m] = [secure.random(peersLength), 0]
	for addr of peers
	if n is m then break
	m++

	[host, port] = addr.split ':'
	conn = net.connect port, host, ->
	d = new Date()
	tracker = secure.randomHex()
	pendingHookups[tracker] = d.getTime()
	conn.end 'hookup ' + serverPort + ' ' + tracker

	conn.on 'error', ->

	setInterval maintenance, 5000

	publish = () ->
	if peersLength is 0 then return setTimeout publish, 10000

	# Publish chunks.
	args = ({tag: tag, chunk: chunk} for tag, chunk of chunks)
	pub = (item, done) ->
	drain.push cmd: 'distr', tag: item.tag, chunk: item.chunk.data, cb: ->
	setTimeout done, Math.random() * 50000

	async.mapSeries args, pub, -> setTimeout publish, 10000

	publish()

	# Command Line Interface
	frontend = ->
	# Completion service.
	completer = (line) ->
	[completions, hits] = [[], []]

	line = path.normalize line
	[p, n] = [path.dirname(line), path.basename(line)]
	exists = fs.existsSync p

	completions = if exists then fs.readdirSync p else []

	hits = completions.filter (c) -> c.indexOf(n) is 0

	if hits.length is 1
	h = hits[0]
	hits[0] = p
	hits[0] += if p[p.length - 1] is path.sep then '' else path.sep
	hits[0] += h

	stats = fs.statSync hits[0]
	if stats.isDirectory() then hits[0] += path.sep

	rec = if hits.length > 0 then hits else completions
	return [rec, line]

	# Create interface.
	rl = readline.createInterface {
	input: process.stdin
	output: process.stdout
	completer: completer
	}

	# Parses and handles lines entered by the user.
	rl.on 'line', (line) ->
	line = line.trim().split ' '

	switch line[0]
	when "" then console.log ""
	when "chunks"
	console.log tag for tag of chunks

	when "peers"
	console.log addr for addr, _ of peers
	if peersLength is 0 then console.log 'No peers.'

	when "enter"
	if line.length isnt 3 then return rl.prompt true
	conn = net.connect line[2], line[1], ->
	d = new Date()
	tracker = secure.randomHex()
	pendingHookups[tracker] = d.getTime()
	conn.end 'hookup ' + serverPort + ' ' + tracker

	end = (error) =>
	if error? then console.log error
	rl.prompt true

	conn.on 'error', end
	conn.on 'end', end

	when "upload"
	if line.length isnt 1 then return rl.prompt true
	readChunk = (inFd, outFd, cipher) ->
	buff = new Buffer 262144
	fs.read inFd, buff, 0, 262144, null, (err, n, buff) ->
	if err isnt null or n is 0
	return rl.prompt true

	# Encrypt chunk.
	cipher.write buff.slice(0, n)
	chunk = cipher.read()

	# Hash encrypted chunk.
	h = crypto.createHash 'sha256'
	h.end chunk
	tag = h.read().toString 'base64'

	# Publish
	chunks[tag] = data: chunk.toJSON(), ours: true
	chunksLength++

	tb = new Buffer tag
	fs.write outFd, tb, 0, tb.length, null, ->
	readChunk inFd, outFd, cipher

	# Get files needed, open them, and prepare for uploading.
	questions = [
	{ask: 'Input file? ', mode: 'r'},
	{ask: 'Output file? ', mode: 'w'},
	]

	openFile = (task, done) ->
	rl.question task.ask, (file) ->
	fs.open file, task.mode, null, done

	async.mapSeries questions, openFile, (err, fds) ->
	if err?
	console.log err
	rl.prompt true
	else
	key = secure.randomBase64()
	kb = new Buffer key
	fs.write fds[1], kb, 0, kb.length, null, ->
	c = crypto.createCipher 'aes-256-ctr', key
	readChunk fds[0], fds[1], c

	return

	when "download"
	if line.length isnt 1 then return rl.prompt true

	nextLine = (fd, cb) ->
	buff = new Buffer 44
	fs.read fd, buff, 0, 44, null, (err, n, buff) ->
	if err is null and n is 44
	cb buff.toString()
	else
	cb()

	timeout = (tracker) ->
	if not pendingDownloads[tracker]? then return
	pendingDownloads[tracker]('timeout')

	fetchChunk = (inFd, outFd, cipher, tag) ->
	if not tag? then return rl.prompt true

	# Choose a random tracker, put it as pending, and send a
	# request with it.
	tracker = secure.randomHex()
	pendingDownloads[tracker] = (chunk) ->
	if chunk is 'timeout'
	# Timed out waiting for this chunk.
	# Add limiters here later.
	delete pendingDownloads[tracker]
	fetchChunk inFd, outFd, cipher, tag
	else
	chunk = new Buffer chunk

	# Hash encrypted chunk to check integrity.
	h = crypto.createHash 'sha256'
	h.end chunk
	candidateTag = h.read().toString 'base64'

	if tag isnt candidateTag then return
	delete pendingDownloads[tracker]

	# Decrypt chunk.
	cipher.write chunk
	chunk = cipher.read()

	# Output, and get next chunk.
	fs.write outFd, chunk, 0, chunk.length, null, ->
	nextLine inFd, (tag) ->
	fetchChunk inFd, outFd, cipher, tag

	drain.push cmd: 'req', tracker: tracker, tag: tag
	setTimeout timeout, 5000, tracker

	# Get files needed, open them, and prepare for downloading.
	questions = [
	{ask: 'Input file? ', mode: 'r'},
	{ask: 'Output file? ', mode: 'w'},
	]

	openFile = (task, done) ->
	rl.question task.ask, (file) ->
	fs.open file, task.mode, null, done

	async.mapSeries questions, openFile, (err, fds) ->
	if err?
	console.log err
	rl.prompt true
	else
	nextLine fds[0], (key) ->
	c = crypto.createCipher 'aes-256-ctr', key
	nextLine fds[0], (tag) ->
	fetchChunk fds[0], fds[1], c, tag

	return

	else console.log 'Command not known.'

	rl.prompt true

	rl.on 'close', ->
	console.log '\nGoodbye'
	process.exit 0

	rl.prompt true
	{
	"name": "HearSay",
	"version": "0.0.1",
	"private": true,
	"dependencies": {
	"coffee-script": "*",
	"bigdecimal": "*",
	"async": "*",
	"msgpack": "*",
	"event-stream": "*"
	}
	}
	es = require 'event-stream'
	crypto = require 'crypto'
	msgpack = require 'msgpack'
	{BigInteger} = require 'bigdecimal'
	salt = 'vpfSIDPgJ5tBt7gZgnGQeG8G6r0q4fDkDWWtZD7zqAsYWw2Ep81vIjqC3gJM'

	exports.remote = (conn, init) ->
	dh = crypto.getDiffieHellman 'modp14'
	dh.generateKeys()

	conn.write dh.getPublicKey 'hex'
	conn.once 'data', (data) ->
	# Generate keys.
	secret = dh.computeSecret data.toString(), 'hex', 'hex'
	key = crypto.pbkdf2Sync secret, salt, 2048, 128

	[readCKey, readMKey] = [key.slice(0, 32), key.slice(32, 64)]
	[writeCKey, writeMKey] = [key.slice(64, 96), key.slice(96, 128)]

	if init
	[readCKey, writeCKey] = [writeCKey, readCKey]
	[readMKey, writeMKey] = [writeMKey, readMKey]

	readCipher = crypto.createDecipher 'aes-256-ctr', readCKey
	writeCipher = crypto.createCipher 'aes-256-ctr', writeCKey

	# Begin handling input.
	handle = (line, cb) ->
	# Decrypt and validate.
	ct = line.slice 0, line.length - 44
	tag = line.slice line.length - 44

	readCipher.write ct, 'base64'
	pt = msgpack.unpack readCipher.read()

	readMAC = crypto.createHmac 'sha256', readMKey
	readMAC.end ct, 'base64'
	candidateTag = readMAC.read().toString 'base64'
	if candidateTag != tag then return conn.end()

	# Handle data.
	conn.emit 'line', pt
	cb null, null

	p = es.pipeline conn, es.split(), es.map handle
	p.on 'error', ->
	conn.emit 'secure', writeCipher, writeMKey

	# Probabilistically decides if we 'want' something.
	exports.want = (n) ->
	a = BigInteger('3', 10).pow(n)
	b = BigInteger('4', 10).pow(n)
	r = crypto.randomBytes(2).toString('hex')
	x = BigInteger(r, 16).remainder(b)

	if x.compareTo(a) is 1 then false else true

	# Probablistically decides if we should drop a packet.
	exports.drop = ->
	x = exports.random 10
	if x is 2 then true else false

	# Choose a random number in the range [0, max)
	exports.random = (max) ->
	max = BigInteger max.toString(), 10
	n = Math.ceil(((Math.log(max) / Math.log(2)) + 1) / 8)
	r = crypto.randomBytes(n).toString('hex')
	x = BigInteger(r, 16).remainder(max)

	(Number) x

	# Returns a string of random hex.
	exports.randomHex = (n = 32) -> crypto.randomBytes(n).toString 'hex'
	exports.randomBase64 = (n = 32) -> crypto.randomBytes(n).toString 'base64'