tor/doc/TODO.future

$Id: TODO 16258 2008-07-30 13:04:38Z nickm $
Legend:
SPEC!!  - Not specified
SPEC    - Spec not finalized
N       - nick claims
R       - arma claims
P       - phobos claims
S       - Steven claims
E       - Matt claims
M       - Mike claims
J       - Jeff claims
I       - ioerror claims
W       - weasel claims
K       - Karsten claims
        - Not done
        * Top priority
        . Partially done
        o Done
        d Deferrable
        D Deferred
        X Abandoned

=======================================================================

Later, unless people want to implement them now:
  - Actually use SSL_shutdown to close our TLS connections.
  - Include "v" line in networkstatus getinfo values.
    [Nick: bridge authorities output a networkstatus that is missing
     version numbers. This is inconvenient if we want to make sure
     bridgedb gives out bridges with certain characteristics. -RD]
    [Okay. Is this a separate item, or is it the same issue as the lack of
     a "v" line in response to the controller GETINFO command? -NM]
  - Let tor dir mirrors proxy connections to the tor download site, so
    if you know a bridge you can fetch the tor software.
  - when somebody uses the controlport as an http proxy, give them
    a "tor isn't an http proxy" error too like we do for the socks port.
  - MAYBE kill stalled circuits rather than stalled connections.  This is
    possible thanks to cell queues, but we need to consider the anonymity
    implications.
  - Make resolves no longer use edge_connection_t unless they are actually
    _on_ a socks connection: have edge_connection_t and (say)
    dns_request_t both extend an edge_stream_t, and have p_streams and
    n_streams both be linked lists of edge_stream_t.
  - Generate torrc.{complete|sample}.in, tor.1.in, the HTML manual, and the
    online config documentation from a single source.
  - It would be potentially helpful to respond to https requests on
    the OR port by acting like an HTTPS server.
  - Make the timestamp granularity on logs configurable, with default
    of "1 second".  This might make some kinds of after-the-fact attack harder.

Can anybody remember why we wanted to do this and/or what it means?
  - config option __ControllerLimit that hangs up if there are a limit
    of controller connections already.
    [This was mwenge's idea. The idea is that a Tor controller can
     "fill" Tor's controller slot quota, so jerks can't do cross-protocol
     attacks like the http form attack. -RD]
  - Bridge issues
    . Ask all directory questions to bridge via BEGIN_DIR.
    - use the bridges for dir fetches even when our dirport is open.
    - drop 'authority' queries if they're to our own identity key; accept
      them otherwise.
      - give extend_info_t a router_purpose again



If somebody wants to do this in some version, they should:
  - Create packages for Nokia 800, requested by Chris Soghoian
  - More work on AvoidDiskWrites
  - Make DNSPort support TCP DNS.


* * * * Roger, please sort these: * * * *

  - bridge communities with local bridge authorities:
    - clients who have a password configured decide to ask their bridge
      authority for a networkstatus
    - be able to have bridges that aren't in your torrc. save them in
      state file, etc.
  - Consider if we can solve: the Tor client doesn't know what flags
    its bridge has (since it only gets the descriptor), so it can't
    make decisions based on Fast or Stable.
  - Some mechanism for specifying that we want to stop using a cached
    bridge.

=======================================================================

Future versions:

  - Protocol
    - Our current approach to block attempts to use Tor as a single-hop proxy
      is pretty lame; we should get a better one.
    - Allow small cells and large cells on the same network?
    - Cell buffering and resending. This will allow us to handle broken
      circuits as long as the endpoints don't break, plus will allow
      connection (tls session key) rotation.
    - Implement Morphmix, so we can compare its behavior, complexity,
      etc.  But see paper breaking morphmix.
    - Other transport. HTTP, udp, rdp, airhook, etc. May have to do our own
      link crypto, unless we can bully DTLS into it.
    - Need a relay teardown cell, separate from one-way ends.
      (Pending a user who needs this)
    - Handle half-open connections: right now we don't support all TCP
      streams, at least according to the protocol. But we handle all that
      we've seen in the wild.
      (Pending a user who needs this)

  - Directory system
    - BEGIN_DIR items
      - handle connect-dir streams that don't have a chosen_exit_name set.
    - Have a "Faster" status flag that means it. Fast2, Fast4, Fast8?
    - Add an option (related to AvoidDiskWrites) to disable directory
      caching.  (Is this actually a good idea??)
    X Add d64 and fp64 along-side d and fp so people can paste status
      entries into a url. since + is a valid base64 char, only allow one
      at a time. Consider adding to controller as well.
      [abandoned for lack of demand]
    - Some back-out mechanism for auto-approval on authorities
      - a way of rolling back approvals to before a timestamp
        - Consider minion-like fingerprint file/log combination.
    X Have new people be in limbo and need to demonstrate usefulness
      before we approve them.

  - Hidden services:
    d Standby/hotswap/redundant hidden services: needs a proposal.
    - you can insert a hidserv descriptor via the controller.
    - auth mechanisms to let hidden service midpoint and responder filter
      connection requests: proposal 121.
    - Let each hidden service (or other thing) specify its own
      OutboundBindAddress?

  - Server operation
    - If the server is spewing complaints about raising your ulimit -n,
      we should add a note about this to the server descriptor so other
      people can notice too.
    - When we hit a funny error from a dir request (eg 403 forbidden),
      but tor is working and happy otherwise, and we haven't seen many
      such errors recently, then don't warn about it.

  - Controller
    - Implement missing status events and accompanying getinfos
      - DIR_REACHABLE
      - BAD_DIR_RESPONSE (Unexpected directory response; maybe we're behind
        a firewall.)
      - BAD_PROXY (Bad http or https proxy)
      - UNRECOGNIZED_ROUTER (a nickname we asked for is unavailable)
      - Status events related to hibernation
      - something about failing to parse our address?
        from resolve_my_address() in config.c
      - sketchy OS, sketchy threading
      - too many onions queued: threading problems or slow CPU?
    - Implement missing status event fields:
      - TIMEOUT on CHECKING_REACHABILITY
    - GETINFO status/client, status/server, status/general: There should be
      some way to learn which status events are currently "in effect."
      We should specify which these are, what format they appear in, and so
      on.
    - More information in events:
      - Include bandwidth breakdown by conn->type in BW events.
      - Change circuit status events to give more details, like purpose,
        whether they're internal, when they become dirty, when they become
        too dirty for further circuits, etc.
      - Change stream status events analogously.
    - Expose more information via getinfo:
      - import and export rendezvous descriptors
      - Review all static fields for additional candidates
    - Allow EXTENDCIRCUIT to unknown server.
      - We need some way to adjust server status, and to tell tor not to
        download directories/network-status, and a way to force a download.
      - Make everything work with hidden services

  - Performance/resources
    - per-conn write buckets
    - separate config options for read vs write limiting
      (It's hard to support read > write, since we need better
       congestion control to avoid overfull buffers there.  So,
       defer the whole thing.)
    - Rate limit exit connections to a given destination -- this helps
      us play nice with websites when Tor users want to crawl them; it
      also introduces DoS opportunities.
    - Consider truncating rather than destroying failed circuits,
      in order to save the effort of restarting.  There are security
      issues here that need thinking, though.
    - Handle full buffers without totally borking
    - Rate-limit OR and directory connections overall and per-IP and
      maybe per subnet.

  - Misc
    - Hold-open-until-flushed now works by accident; it should work by
      design.
    - Display the reasons in 'destroy' and 'truncated' cells under
      some circumstances?
    - Make router_is_general_exit() a bit smarter once we're sure what
      it's for.
    - Automatically determine what ports are reachable and start using
      those, if circuits aren't working and it's a pattern we
      recognize ("port 443 worked once and port 9001 keeps not
      working").

  - Security
    - some better fix for bug #516?
    - Directory guards
    - Mini-SoaT:
      - Servers might check certs for known-good ssl websites, and if
        they come back self-signed, declare themselves to be
        non-exits.  Similar to how we test for broken/evil dns now.
      - Authorities should try using exits for http to connect to some
        URLS (specified in a configuration file, so as not to make the
        List Of Things Not To Censor completely obvious) and ask them
        for results.  Exits that don't give good answers should have
        the BadExit flag set.
      - Alternatively, authorities should be able to import opinions
        from Snakes on a Tor.
    - Bind to random port when making outgoing connections to Tor servers,
      to reduce remote sniping attacks.
    - Audit everything to make sure rend and intro points are just as
      likely to be us as not.
    - Do something to prevent spurious EXTEND cells from making
      middleman nodes connect all over.  Rate-limit failed
      connections, perhaps?
    - DoS protection: TLS puzzles, public key ops, bandwidth exhaustion.

  - Needs thinking
    - Now that we're avoiding exits when picking non-exit positions,
      we need to consider how to pick nodes for internal circuits. If
      we avoid exits for all positions, we skew the load balancing. If
      we accept exits for all positions, we leak whether it's an
      internal circuit at every step. If we accept exits only at the
      last hop, we reintroduce Lasse's attacks from the Oakland paper.

  - Windows server usability
    - Solve the ENOBUFS problem.
      - make tor's use of openssl operate on buffers rather than sockets,
        so we can make use of libevent's buffer paradigm once it has one.
      - make tor's use of libevent tolerate either the socket or the
        buffer paradigm; includes unifying the functions in connect.c.
    - We need a getrlimit equivalent on Windows so we can reserve some
      file descriptors for saving files, etc. Otherwise we'll trigger
      asserts when we're out of file descriptors and crash.

  - Documentation
    - a way to generate the website diagrams from source, so we can
      translate them as utf-8 text rather than with gimp. (svg? or
      imagemagick?)
    . Flesh out options_description array in src/or/config.c
    . multiple sample torrc files
    - Refactor tor man page to divide generally useful options from
      less useful ones?
    - Add a doxygen style checker to make check-spaces so nick doesn't drift
       too far from arma's undocumented styleguide.  Also, document that
       styleguide in HACKING.  (See r9634 for example.)
       - exactly one space at beginning and at end of comments, except i
         guess when there's line-length pressure.
       - if we refer to a function name, put a () after it.
       - only write <b>foo</b> when foo is an argument to this function.
       - doxygen comments must always end in some form of punctuation.
       - capitalize the first sentence in the doxygen comment, except
         when you shouldn't.
       - avoid spelling errors and incorrect comments. ;)

  - Packaging
    - The Debian package now uses --verify-config when (re)starting,
      to distinguish configuration errors from other errors. Perhaps
      the RPM and other startup scripts should too?
    - add a "default.action" file to the tor/vidalia bundle so we can
      fix the https thing in the default configuration:
      http://wiki.noreply.org/noreply/TheOnionRouter/TorFAQ#PrivoxyWeirdSSLPort


=======================================================================

Documentation, non-version-specific.
  - Specs
    - Mark up spec; note unclear points about servers
NR  - write a spec appendix for 'being nice with tor'
    - Specify the keys and key rotation schedules and stuff
    . Finish path-spec.txt
  - Mention controller libs someplace.
  - Remove need for HACKING file.
  - document http://wiki.noreply.org/noreply/TheOnionRouter/TransparentProxy on freebsd and osx
P - figure out why x86_64 won't build rpms from tor.spec
P - figure out rpm spec files for bundles of vidalia-tor-polipo
P - figure out polipo install scripts for bundles of vidalia-tor-polipo on osx, win32
  - figure out selinux policy for tor
P - change packaging system to more automated and specific for each
     platform, suggested by Paul Wouter
P - Setup repos for redhat and suse rpms & start signing the rpms the
    way package management apps prefer

Website:
J . tor-in-the-media page
P  - Figure out licenses for website material.
    (Phobos reccomends the Open Publication License with Option A at
    http://opencontent.org/openpub/)
P  - put the logo on the website, in source form, so people can put it on
    stickers directly, etc.
P  - put the source image for the stickers on the website, so people can
    print their own
P - figure out a license for the logos and docs we publish (trademark
figures into this)
    (Phobos reccomends the Open Publication License with Option A at
    http://opencontent.org/openpub/)
P  - ask Jan/Jens to be the translation coordinator? add to volunteer page.
I - add a page for localizing all tor's components.
  - It would be neat if we had a single place that described _all_ the
    tor-related tools you can use, and what they give you, and how well they
    work.  Right now, we don't give a lot of guidance wrt
    torbutton/foxproxy/privoxy/polipo in any consistent place.
P - create a 'blog badge' for tor fans to link to and feature on their
    blogs. A sample is at http://interloper.org/tmp/tor/tor-button.png
  - More prominently, we should have a recommended apps list.
    - recommend pidgin (gaim is renamed)
    - unrecommend IE because of ftp:// bug.
  - Addenda to tor-design
    - we should add a preamble to tor-design saying it's out of date.
    - we should add an appendix or errata on what's changed.

  - Tor mirrors
    - make a mailing list with the mirror operators
    o make an automated tool to check /project/trace/ at mirrors to
      learn which ones are lagging behind.
    - auto (or manually) cull the mirrors that are broken; and
      contact their operator?
    - a set of instructions for mirror operators to make their apaches
      serve our charsets correctly, and bonus points for language
      negotiation.
    - figure out how to load-balance the downloads across mirrors?
    - ponder how to get users to learn that they should google for
      "tor mirrors" if the main site is blocked.
    - find a mirror volunteer to coordinate all of this