telehash/lib/util/handshake.js

A telehash library for node and browserify

var crypto = require('crypto');
var lob = require('lob-enc')
var hashname = require('hashname');
var log = require("./log")("Handshake")

module.exports = {
  bootstrap : handshake_bootstrap,
  validate  : handshake_validate,
  from      : handshake_from,
  types     : handshake_types,
  collect   : handshake_collect
};

var hcache = {}
setInterval(function(){hcache = {}}, 60 * 1000)



/**
 * collect incoming handshakes to accept them
 * @param {object} id
 * @param {handshake} handshake
 * @param {pipe} pipe
 * @param {Buffer} message
 */
function handshake_collect(mesh, id, handshake, pipe, message)
{
  handshake = handshake_bootstrap(handshake);
  if (!handshake)
    return false;

  var valid = handshake_validate(id,handshake, message, mesh);
  if (!valid)
    return false;

  // get all from cache w/ matching at, by type
  var types = handshake_types(handshake, id);

  // bail unless we have a link
  if(!types.link)
  {
    log.debug('handshakes w/ no link yet',id,types);
    return false;
  }

  // build a from json container
  var from = handshake_from(handshake, pipe, types.link)

  // if we already linked this hashname, just update w/ the new info
  if(mesh.index[from.hashname])
  {
    log.debug('refresh link handshake')
    from.sync = false; // tell .link to not auto-sync!
    return mesh.link(from);
  } else {
    
  }

  log.debug('untrusted hashname',from);
  from.received = {packet:types.link._message, pipe:pipe} // optimization hints as link args
  from.handshake = types; // include all handshakes
  if(mesh.accept)
    mesh.accept(from);
  return false;
}

function handshake_bootstrap(handshake){
  // default an at for bare key handshakes if not given
  if(typeof handshake.json.at === 'undefined')
    handshake.json.at = Date.now();

  // verify at
  if(typeof handshake.json.at != 'number' || handshake.json.at <= 0)
  {
    log.debug('invalid handshake at',handshake.json);
    return false;
  }

  // default the handshake type
  if(typeof handshake.json.type != 'string')
    handshake.json.type = 'link';

  // upvert deprecated key to link type
  if(handshake.json.type == 'key')
  {
    // map only csid keys into attachment header
    var json = {};
    hashname.ids(handshake.json).forEach(function(csid){
      if(handshake.json[csid] === true)
        handshake.json.csid = csid; // cruft
      json[csid] = handshake.json[csid];
    });

    if(message)
      json[message.head.toString('hex')] = true;

    var attach = lob.encode(json, handshake.body);
    handshake.json.type = 'link';
    handshake.body = attach;
  }

  return handshake
}

function handshake_validate(id,handshake, message, mesh){
  if(handshake.json.type == 'link')
  {
    // if it came from an encrypted message
    if(message)
    {
      // make sure the link csid matches the message csid
      handshake.json.csid = message.head.toString('hex');
      // stash inside the handshake, can be used later to create the exchange immediately
      handshake._message = message;
    }

    var attach = lob.decode(handshake.body);
    if(!attach)
    {
      log.debug('invalid link handshake attachment',handshake.body);
      return false;
    }

    // make sure key info is at least correct
    var keys = {};
    keys[handshake.json.csid] = attach.body;
    var csid = hashname.match(mesh.keys, keys, null, attach.json);
    if(handshake.json.csid != csid)
    {
      log.debug('invalid key handshake, unsupported csid',attach.json, keys);
      return false;
    }
    handshake.json.hashname = hashname.fromKeys(keys, attach.json);
    if(!handshake.json.hashname)
    {
      log.debug('invalid key handshake, no hashname',attach.json, keys);
      return false;
    }

    // hashname is valid now, so stash key bytes in handshake
    handshake.body = attach.body;
  }

  // add it to the cache

  hcache[id] = (hcache[id] || [] ).concat([handshake]);

  return true;

}

function handshake_types (handshake, id){
  var types = {}
  hcache[id].forEach(function(hs){
    if(hs.json.at === handshake.json.at)
      types[hs.json.type] = hs;
  });
  return types;
}

function handshake_from (handshake, pipe, link){
  return {
    paths    : (pipe.path) ? [pipe.path] : [],
    hashname : link.json.hashname,
    csid     : link.json.csid,
    key      : link.body
  };
}