tor/doc/TODO

$Id$
Legend:
SPEC!!  - Not specified
SPEC    - Spec not finalized
N       - nick claims
R       - arma claims
P       - phobos claims
        - Not done
        * Top priority
        . Partially done
        o Done
        D Deferred
        X Abandoned

Non-Coding:
  - Mark up spec; note unclear points about servers
  - Mention controller libs someplace.
P - flesh out the rest of the section 6 of the faq
  . more pictures from ren. he wants to describe the tor handshake
R - make a page with the hidden service diagrams.
NR- write a spec appendix for 'being nice with tor'
  - tor-in-the-media page
  - Remove need for HACKING file.
  - Figure out licenses for website material.

Website:
  - and remove home and make the "Tor" picture be the link to home.
  - put the logo on the website, in source form, so people can put it on
    stickers directly, etc.

R - track down the patch for cross-compiling.
    . <nickm> "Let's try to find a way to make it run and make the version
       match, but if not, let's just make it run."
    - <arma> should we detect if we have a --with-ssl-dir and try the -R
      by default, if it works?

  - support dir 503s better
    o clients don't log as loudly when they receive them
    - they don't count toward the 3-strikes rule
      - should there be some threshold of 503's after which we give up?
    - think about how to split "router is down" from "dirport shouldn't
      be tried for a while"?
    - authorities should *never* 503 a cache, but *should* 503 clients
      when they feel like it.
    - update dir-spec with what we decided for each of these

  - are there other options that we haven't documented so far?
  . look at the proposed os x uninstaller:
    http://archives.seul.org/or/talk/Jan-2006/msg00038.html

- Interim things:
  - provide no-cache no-index headers from the dirport?
  - exitlist should avoid outputting the same IP address twice.

Must-have items for 0.1.2.x:

  - If we fail to connect via an exit enclave, (warn and) try again
    without demanding that exit node.
  - If we have no predicted ports, don't fetch router descriptors.
    This way we are more dormant.
  - Directory guards
R - Server usability
    - look into "uncounting" bytes spent on local connections. so
      we can bandwidthrate but still have fast downloads.
    - Write limiting; separate token bucket for write
    - dir answers include a your-ip-address-is header, so we can
      break our dependency on dyndns.
N - Better hidden service performance, with possible redesign.
  - Asynchronous DNS
    - What to use? C-ares? Libdns? AGL's patch?
  - Better estimates in the directory of whether servers have good uptime
    (high expected time to failure) or good guard qualities (high
    fractional uptime).
    - AKA Track uptime as %-of-time-up, as well as time-since-last-down.
N . memory usage on dir servers. copy less!
    o Remember offset and location of each descriptor in the cache/journal
    - When sending a big pile of descs to a client, don't shove them all on
      the buffer at once.
      X This may require routerinfo_t or signed_descriptor_t to get slightly
        refcounted.  (Only slightly; we'd only need to know whether it's on
        the routerlist->routers or routerlist->old_routers, and how many
        directory conns are returning it.)
      - Possibly, we could just keep a list of the descriptor digests for
        the descriptors we still want to send.  We might end up truncating
        some replies by returning fewer descriptors than were requested (if
        somebody requests a desc that we throw away before we deliver it),
        but this happens only when somebody wants an obsolete desc, and
        clients can already handle truncated replies.
      - But what do we do about compression? That's the part that makes
        stuff hard.

    - Make sure offset is correct in the presence of windows FS insanity.
    - Consider whether it's smart to mmap cache files where possible.
    - Consider whether it's smart to lazy-load routerdescs on non-directories.
N - oprofile including kernel time on multiple platforms

Items for 0.1.2:
  - We need a separate list of "hidserv authorities" if we want to
    retire moria1 from the main list.
  - Improve controller
      - 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.
        - What do we want here, exactly?
        - Specify and implement it.
      - Change stream status events analogously.
        - What do we want here, exactly?
        - Specify and implement it.
      - Make other events "better".
      - Change stream status events analogously.
        - What do we want here, exactly?
        - Specify and implement it.
      - Make other events "better" analogously
        - What do we want here, exactly?
        - Specify and implement it.
      . 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.
      - It would be nice to request address lookups from the controller
        without using SOCKS.
      - Make everything work with hidden services

  - Clients should prefer to avoid exit nodes for non-exit path positions.
    (bug 200)
  - Make "setconf" and "hup" behavior cleaner for LINELIST config
    options (e.g. Log). Bug 238.

  - We need a way for the authorities to declare that nodes are
    in a family.  Also, it kinda sucks that family declarations use O(N^2)
    space in the descriptors.
    - Design
    - Implement

  - Have a "Faster" status flag that means it. Fast2, Fast4, Fast8?

  - When we connect to a Tor server, it sends back a cell listing
    the IP it believes it is using. Use this to block dvorak's attack.
    Also, this is a fine time to say what time you think it is.
    o Verify that a new cell type is okay with deployed codebase
    - Specify
    - Implement

R - Failed rend desc fetches sometimes don't get retried.

  - Directory system improvements
    - config option to publish what ports you listen on, beyond
      ORPort/DirPort.  It should support ranges and bit prefixes (?) too.
      - Parse this.
      - Relay this in networkstatus.

    - Non-directories don't need to keep descriptors in memory.
      - Remember file and offset.
      - Keep a journal FD for appending router descriptors

  - Make reverse DNS work.

Topics to think about during 0.1.2.x development:
  - Figure out non-clique.
  - Figure out partial network knowledge.
  - Figure out incentives.
  - Figure out hidden services.

Minor items for 0.1.2.x as time permits.
  - The bw_accounting file should get merged into the state file.
  - Streamline how we define a guard node as 'up'. document it somewhere.
  - Better installers and build processes.
    - Commit edmanm's win32 makefile to tor cvs contrib, or write a new one.
    - Can we cross-compile?
R - Christian Grothoff's attack of infinite-length circuit.
    the solution is to have a separate 'extend-data' cell type
    which is used for the first N data cells, and only
    extend-data cells can be extend requests.
    - Specify, including thought about anonymity implications.
    - Implement
N - Display the reasons in 'destroy' and 'truncated' cells under some
    circumstances?
  - 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.
  - 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.
  X the tor client can do the "automatic proxy config url" thing?
    (no, let's leave this for applications like torbutton)
  - 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").
N - Should router info have a pointer to routerstatus?
    - We should at least do something about the duplicated fields.

  X switch accountingmax to count total in+out, not either in or
    out. it's easy to move in this direction (not risky), but hard to
    back out if we decide we prefer it the way it already is. hm.

  - cpu fixes:
    - see if we should make use of truncate to retry
R   - kill dns workers more slowly

  . Directory changes
    . Some back-out mechanism for auto-approval
      - a way of rolling back approvals to before a timestamp
        - Consider minion-like fingerprint file/log combination.

  - packaging and ui stuff:
    . multiple sample torrc files
    - uninstallers
      . for os x
    . figure out how to make nt service stuff work?
      . Document it.
    o Add version number to directory.
N   - Vet all pending installer patches
      - Win32 installer plus privoxy, sockscap/freecap, etc.
      - Vet win32 systray helper code

  - document:
    - recommend gaim.
    - unrecommend IE because of ftp:// bug.
    - torrc.complete.in needs attention?

  - Bind to random port when making outgoing connections to Tor servers,
    to reduce remote sniping attacks.
  - Have new people be in limbo and need to demonstrate usefulness
    before we approve them.
  - Clients should estimate their skew as median of skew from servers
    over last N seconds.
  - Security
    - Alices avoid duplicate /24 servers.
    - Analyze how bad the partitioning is or isn't.

  . Update the hidden service stuff for the new dir approach.
    - switch to an ascii format, maybe sexpr?
    - authdirservers publish blobs of them.
    - other authdirservers fetch these blobs.
    - hidserv people have the option of not uploading their blobs.
    - you can insert a blob via the controller.
    - and there's some amount of backwards compatibility.
    - teach clients, intro points, and hidservs about auth mechanisms.
    - come up with a few more auth mechanisms.
  - auth mechanisms to let hidden service midpoint and responder filter
    connection requests.

  . Come up with a coherent strategy for bandwidth buckets and TLS. (The
    logic for reading from TLS sockets is likely to overrun the bandwidth
    buckets under heavy load.  (Really, the logic was never right in the
    first place.)  Also, we should audit all users of get_pending_bytes().)
      - Make it harder to circumvent bandwidth caps: look at number of bytes
        sent across sockets, not number sent inside TLS stream.

  - Make router_is_general_exit() a bit smarter once we're sure what it's for.

  - rewrite how libevent does select() on win32 so it's not so very slow.
  - 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?

Future version:
  - Limit to 2 dir, 2 OR, N SOCKS connections per IP.
  - Handle full buffers without totally borking
  - Rate-limit OR and directory connections overall and per-IP and
    maybe per subnet.
  - Hold-open-until-flushed now works by accident; it should work by
    design.
  - DoS protection: TLS puzzles, public key ops, bandwidth exhaustion.
    - Specify?
  - tor-resolve script should use socks5 to get better error messages.
  - hidserv offerers shouldn't need to define a SocksPort
    * figure out what breaks for this, and do it.
  - Relax clique assumptions.
  X start handling server descriptors without a socksport?
  - tor should be able to have a pool of outgoing IP addresses
    that it is able to rotate through. (maybe)
  - let each hidden service (or other thing) specify its own
    OutboundBindAddress?

Blue-sky:
  - Patch privoxy and socks protocol to pass strings to the browser.
  - Standby/hotswap/redundant hidden services.
  - Robust decentralized storage for hidden service descriptors.
  - The "China problem"
  - 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.
  - Other transport. HTTP, udp, rdp, airhook, etc. May have to do our own
    link crypto, unless we can bully openssl 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)