[or-cvs] r15572: first draft of the Tor 0.2.0.x Release Notes. (tor/trunk)

arma at seul.org arma at seul.org
Mon Jun 30 22:01:18 UTC 2008


Author: arma
Date: 2008-06-30 18:01:17 -0400 (Mon, 30 Jun 2008)
New Revision: 15572

Modified:
   tor/trunk/ReleaseNotes
Log:
first draft of the Tor 0.2.0.x Release Notes.


Modified: tor/trunk/ReleaseNotes
===================================================================
--- tor/trunk/ReleaseNotes	2008-06-30 21:52:39 UTC (rev 15571)
+++ tor/trunk/ReleaseNotes	2008-06-30 22:01:17 UTC (rev 15572)
@@ -3,6 +3,767 @@
 of Tor. If you want to see more detailed descriptions of the changes in
 each development snapshot, see the ChangeLog file.
 
+Changes in version 0.2.0.30 - 2008-07-xx
+  This new stable release switches to a more efficient directory
+  distribution design, adds features to make Tor harder to block,
+  allows Tor to act as a DNS proxy,
+
+  o New v3 directory design:
+    - Tor now uses a new way to learn about and distribute information
+      about the network: the directory authorities vote on a common
+      network status document rather than each publishing their own
+      opinion. Now clients and caches download only one networkstatus
+      document to bootstrap, rather than downloading one for each
+      authority. Clients only download router descriptors listed in
+      the consensus. Implements proposal 101; see doc/spec/dir-spec.txt
+      for details.
+    - Set up moria1, tor26, and dizum as v3 directory authorities
+      in addition to being v2 authorities. Also add three new ones:
+      ides (run by Mike Perry), gabelmoo (run by Karsten Loesing), and
+      dannenberg (run by CCC).
+    - Switch to multi-level keys for directory authorities: now their
+      long-term identity key can be kept offline, and they periodically
+      generate a new signing key. Clients fetch the "key certificates"
+      to keep up to date on the right keys. Add a standalone tool
+      "tor-gencert" to generate key certificates. Implements proposal 103.
+    - Add a new V3AuthUseLegacyKey config option to make it easier for
+      v3 authorities to change their identity keys if another bug like
+      Debian's OpenSSL RNG flaw appears.
+    - Authorities and caches fetch the v2 networkstatus documents
+      less often, now that v3 is recommended.
+
+  o Make Tor connections stand out less on the wire:
+    - Use an improved TLS handshake designed by Steven Murdoch in proposal
+      124, as revised in proposal 130. The new handshake is meant to
+      be harder for censors to fingerprint, and it adds the ability
+      to detect certain kinds of man-in-the-middle traffic analysis
+      attacks. The new handshake format includes version negotiation for
+      OR connections as described in proposal 105, which will allow us
+      to improve Tor's link protocol more safely in the future.
+    - Enable encrypted directory connections by default for non-relays,
+      so censor tools that block Tor directory connections based on their
+      plaintext patterns will no longer work. This means Tor works in
+      certain censored countries by default again.
+    - Stop including recognizeable strings in the commonname part of
+      Tor's x509 certificates.
+
+  o Implement bridge relays:
+    - Bridge relays (or "bridges" for short) are Tor relays that aren't
+      listed in the main Tor directory. Since there is no complete public
+      list of them, even an ISP that is filtering connections to all the
+      known Tor relays probably won't be able to block all the bridges.
+      See doc/design-paper/blocking.pdf and proposal 125 for details.
+    - New config option BridgeRelay that specifies you want to be a
+      bridge relay rather than a normal relay. When BridgeRelay is set
+      to 1, then a) you cache dir info even if your DirPort ins't on,
+      and b) the default for PublishServerDescriptor is now "bridge"
+      rather than "v2,v3".
+    - New config option "UseBridges 1" for clients that want to use bridge
+      relays instead of ordinary entry guards. Clients then specify
+      bridge relays by adding "Bridge" lines to their config file. Users
+      can learn about a bridge relay either manually through word of
+      mouth, or by one of our rate-limited mechanisms for giving out
+      bridge addresses without letting an attacker easily enumerate them
+      all. See https://www.torproject.org/bridges for details.
+    - Bridge relays behave like clients with respect to time intervals
+      for downloading new v3 consensus documents -- otherwise they
+      stand out. Bridge users now wait until the end of the interval,
+      so their bridge relay will be sure to have a new consensus document.
+
+  o Implement bridge directory authorities:
+    - Bridge authorities are like normal directory authorities, except
+      they don't serve a list of known bridges. Therefore users that know
+      a bridge's fingerprint can fetch a relay descriptor for that bridge,
+      including fetching updates e.g. if the bridge changes IP address,
+      yet an attacker can't just fetch a list of all the bridges.
+    - Set up Tonga as the default bridge directory authority.
+    - Bridge authorities refuse to serve bridge descriptors or other
+      bridge information over unencrypted connections (that is, when
+      responding to direct DirPort requests rather than begin_dir cells.)
+    - Bridge directory authorities do reachability testing on the
+      bridges they know. They provide router status summaries to the
+      controller via "getinfo ns/purpose/bridge", and also dump summaries
+      to a file periodically, so we can keep internal stats about which
+      bridges are functioning.
+    - If bridge users set the UpdateBridgesFromAuthority config option,
+      but the digest they ask for is a 404 on the bridge authority,
+      they fall back to contacting the bridge directly.
+    - Bridges always use begin_dir to publish their server descriptor to
+      the bridge authority using an anonymous encrypted tunnel.
+    - Early work on a "bridge community" design: if bridge authorities set
+      the BridgePassword config option, they will serve a snapshot of
+      known bridge routerstatuses from their DirPort to anybody who
+      knows that password. Unset by default.
+    - Tor now includes an IP-to-country GeoIP file, so bridge relays can
+      report sanitized aggregated summaries in their extra-info documents
+      privately to the bridge authority, listing which countries are
+      able to reach them. We hope this mechanism will let us learn when
+      certain countries start trying to block bridges.
+    - Bridge authorities write bridge descriptors to disk, so they can
+      reload them after a reboot. They can also export the descriptors
+      to other programs, so we can distribute them to blocked users via
+      the BridgeDB interface, e.g. via https://bridges.torproject.org/
+      and bridges at torproject.org.
+
+  o Tor can be a DNS proxy:
+    - The new client-side DNS proxy feature replaces the need for
+      dns-proxy-tor: Just set "DNSPort 9999", and Tor will now listen
+      for DNS requests on port 9999, use the Tor network to resolve them
+      anonymously, and send the reply back like a regular DNS server.
+      The code still only implements a subset of DNS.
+    - Add a new AutomapHostsOnResolve option: when it is enabled, any
+      resolve request for hosts matching a given pattern causes Tor to
+      generate an internal virtual address mapping for that host. This
+      allows DNSPort to work sensibly with hidden service users. By
+      default, .exit and .onion addresses are remapped; the list of
+      patterns can be reconfigured with AutomapHostsSuffixes.
+    - Add an "-F" option to tor-resolve to force a resolve for a .onion
+      address. Thanks to the AutomapHostsOnResolve option, this is no
+      longer a completely silly thing to do.
+
+  o Major features (relay usability):
+    - New config options RelayBandwidthRate and RelayBandwidthBurst:
+      a separate set of token buckets for relayed traffic. Right now
+      relayed traffic is defined as answers to directory requests, and
+      OR connections that don't have any local circuits on them. See
+      proposal 111 for details.
+    - Create listener connections before we setuid to the configured
+      User and Group. Now non-Windows users can choose port values
+      under 1024, start Tor as root, and have Tor bind those ports
+      before it changes to another UID. (Windows users could already
+      pick these ports.)
+    - Added a new ConstrainedSockets config option to set SO_SNDBUF and
+      SO_RCVBUF on TCP sockets. Hopefully useful for Tor servers running
+      on "vserver" accounts. Patch from coderman.
+
+  o Major features (directory authorities):
+    - Directory authorities track weighted fractional uptime and weighted
+      mean-time-between failures for relays. WFU is suitable for deciding
+      whether a node is "usually up", while MTBF is suitable for deciding
+      whether a node is "likely to stay up." We need both, because
+      "usually up" is a good requirement for guards, while "likely to
+      stay up" is a good requirement for long-lived connections.
+    - Directory authorities use a new formula for selecting which relays
+      to advertise as Guards: they must be in the top 7/8 in terms of
+      how long we have known about them, and above the median of those
+      nodes in terms of weighted fractional uptime.
+    - Directory authorities use a new formula for selecting which relays
+      to advertise as Stable: when we have 4 or more days of data, use
+      median measured MTBF rather than median declared uptime. Implements
+      proposal 108.
+    - Directory authorities accept and serve "extra info" documents for
+      routers. Routers now publish their bandwidth-history lines in the
+      extra-info docs rather than the main descriptor. This step saves
+      60% (!) on compressed router descriptor downloads. Servers upload
+      extra-info docs to any authority that accepts them; directory
+      authorities now allow multiple router descriptors and/or extra
+      info documents to be uploaded in a single go. Authorities, and
+      caches that have been configured to download extra-info documents,
+      download them as needed. Implements proposal 104.
+    - Authorities now list relays who have the same nickname as
+      a different named relay, but list them with a new flag:
+      "Unnamed". Now we can make use of relays that happen to pick the
+      same nickname as a server that registered two years ago and then
+      disappeared. Implements proposal 122.
+    - Store routers in a file called cached-descriptors instead of in
+      cached-routers. Initialize cached-descriptors from cached-routers
+      if the old format is around. The new format allows us to store
+      annotations along with descriptors, to record the time we received
+      each descriptor, its source, and its purpose: currently one of
+      general, controller, or bridge.
+
+  o Major features (other):
+    - New config options WarnPlaintextPorts and RejectPlaintextPorts so
+      Tor can warn and/or refuse connections to ports commonly used with
+      vulnerable-plaintext protocols. Currently we warn on ports 23,
+      109, 110, and 143, but we don't reject any. Based on proposal 129
+      by Kevin Bauer and Damon McCoy.
+    - Integrate Karsten Loesing's Google Summer of Code project to publish
+      hidden service descriptors on a set of redundant relays that are a
+      function of the hidden service address. Now we don't have to rely
+      on three central hidden service authorities for publishing and
+      fetching every hidden service descriptor. Implements proposal 114.
+    - Allow tunnelled directory connections to ask for an encrypted
+      "begin_dir" connection or an anonymized "uses a full Tor circuit"
+      connection independently. Now we can make anonymized begin_dir
+      connections for (e.g.) more secure hidden service posting and
+      fetching.
+
+  o Major bugfixes (crashes and assert failures):
+    - Stop imposing an arbitrary maximum on the number of file descriptors
+      used for busy servers. Bug reported by Olaf Selke; patch from
+      Sebastian Hahn.
+    - Avoid possible failures when generating a directory with routers
+      with over-long versions strings, or too many flags set.
+    - Fix a rare assert error when we're closing one of our threads:
+      use a mutex to protect the list of logs, so we never write to the
+      list as it's being freed. Fixes the very rare bug 575, which is
+      kind of the revenge of bug 222.
+    - Avoid segfault in the case where a badly behaved v2 versioning
+      directory sends a signed networkstatus with missing client-versions.
+    - When we hit an EOF on a log (probably because we're shutting down),
+      don't try to remove the log from the list: just mark it as
+      unusable. (Bulletproofs against bug 222.)
+
+  o Major bugfixes (code security fixes):
+    - Detect size overflow in zlib code. Reported by Justin Ferguson and
+      Dan Kaminsky.
+    - Rewrite directory tokenization code to never run off the end of
+      a string. Fixes bug 455. Patch from croup.
+    - Be more paranoid about overwriting sensitive memory on free(),
+      as a defensive programming tactic to ensure forward secrecy.
+
+  o Major bugfixes (anonymity fixes):
+    - Reject requests for reverse-dns lookup of names that are in
+      a private address space. Patch from lodger.
+    - Never report that we've used more bandwidth than we're willing to
+      relay: it leaks how much non-relay traffic we're using. Resolves
+      bug 516.
+    - As a client, do not believe any server that tells us that an
+      address maps to an internal address space.
+    - Warn about unsafe ControlPort configurations.
+    - Directory authorities now call routers Fast if their bandwidth is
+      at least 100KB/s, and consider their bandwidth adequate to be a
+      Guard if it is at least 250KB/s, no matter the medians. This fix
+      complements proposal 107.
+    - Directory authorities now never mark more than 3 servers per IP as
+      Valid and Running. Implements proposal 109, by Kevin Bauer and
+      Damon McCoy.
+    - If we're a relay, avoid picking ourselves as an introduction point,
+      a rendezvous point, or as the final hop for internal circuits. Bug
+      reported by taranis and lodger.
+    - Exit relays that are used as a client can now reach themselves
+      using the .exit notation, rather than just launching an infinite
+      pile of circuits. Fixes bug 641. Reported by Sebastian Hahn.
+    - Fix a bug where, when we were choosing the 'end stream reason' to
+      put in our relay end cell that we send to the exit relay, Tor
+      clients on Windows were sometimes sending the wrong 'reason'. The
+      anonymity problem is that exit relays may be able to guess whether
+      the client is running Windows, thus helping partition the anonymity
+      set. Down the road we should stop sending reasons to exit relays,
+      or otherwise prevent future versions of this bug.
+    - Only update guard status (usable / not usable) once we have
+      enough directory information. This was causing us to discard all our
+      guards on startup if we hadn't been running for a few weeks. Fixes
+      bug 448.
+    - When our directory information has been expired for a while, stop
+      being willing to build circuits using it. Fixes bug 401.
+
+  o Major bugfixes (peace of mind for relay operators)
+    - Non-exit relays no longer answer "resolve" relay cells, so they
+      can't be induced to do arbitrary DNS requests. (Tor clients already
+      avoid using non-exit relays for resolve cells, but now servers
+      enforce this too.) Fixes bug 619. Patch from lodger.
+    - When we setconf ClientOnly to 1, close any current OR and Dir
+      listeners. Reported by mwenge.
+
+  o Major bugfixes (other):
+    - If we only ever used Tor for hidden service lookups or posts, we
+      would stop building circuits and start refusing connections after
+      24 hours, since we falsely believed that Tor was dormant. Reported
+      by nwf.
+    - Add a new __HashedControlSessionPassword option for controllers
+      to use for one-off session password hashes that shouldn't get
+      saved to disk by SAVECONF --- Vidalia users were accumulating a
+      pile of HashedControlPassword lines in their torrc files, one for
+      each time they had restarted Tor and then clicked Save. Make Tor
+      automatically convert "HashedControlPassword" to this new option but
+      only when it's given on the command line. Partial fix for bug 586.
+    - Patch from "Andrew S. Lists" to catch when we contact a directory
+      mirror at IP address X and he says we look like we're coming from
+      IP address X. Otherwise this would screw up our address detection.
+    - Reject uploaded descriptors and extrainfo documents if they're
+      huge. Otherwise we'll cache them all over the network and it'll
+      clog everything up. Suggested by Aljosha Judmayer.
+
+  o Rate limiting and load balancing improvements:
+    - When we add data to a write buffer in response to the data on that
+      write buffer getting low because of a flush, do not consider the
+      newly added data as a candidate for immediate flushing, but rather
+      make it wait until the next round of writing. Otherwise, we flush
+      and refill recursively, and a single greedy TLS connection can
+      eat all of our bandwidth.
+    - When counting the number of bytes written on a TLS connection,
+      look at the BIO actually used for writing to the network, not
+      at the BIO used (sometimes) to buffer data for the network.
+      Looking at different BIOs could result in write counts on the
+      order of ULONG_MAX. Fixes bug 614.
+    - If we change our MaxAdvertisedBandwidth and then reload torrc,
+      Tor won't realize it should publish a new relay descriptor. Fixes
+      bug 688, reported by mfr.
+    - Avoid using too little bandwidth when our clock skips a few seconds.
+    - Choose which bridge to use proportional to its advertised bandwidth,
+      rather than uniformly at random. This should speed up Tor for
+      bridge users. Also do this for people who set StrictEntryNodes.
+
+  o Bootstrapping faster and building circuits more intelligently:
+    - Fix bug 660 that was preventing us from knowing that we should
+      preemptively build circuits to handle expected directory requests.
+    - When we're checking if we have enough dir info for each relay
+      to begin establishing circuits, make sure that we actually have
+      the descriptor listed in the consensus, not just any descriptor.
+    - Correctly notify one-hop connections when a circuit build has
+      failed. Possible fix for bug 669. Found by lodger.
+    - Clients now hold circuitless TLS connections open for 1.5 times
+      MaxCircuitDirtiness (15 minutes), since it is likely that they'll
+      rebuild a new circuit over them within that timeframe. Previously,
+      they held them open only for KeepalivePeriod (5 minutes).
+
+  o Performance improvements (memory):
+    - Add OpenBSD malloc code from "phk" as an optional malloc
+      replacement on Linux: some glibc libraries do very poorly with
+      Tor's memory allocation patterns. Pass --enable-openbsd-malloc to
+      ./configure to get the replacement malloc code.
+    - Switch our old ring buffer implementation for one more like that
+      used by free Unix kernels. The wasted space in a buffer with 1mb
+      of data will now be more like 8k than 1mb. The new implementation
+      also avoids realloc();realloc(); patterns that can contribute to
+      memory fragmentation.
+    - Change the way that Tor buffers data that it is waiting to write.
+      Instead of queueing data cells in an enormous ring buffer for each
+      client->OR or OR->OR connection, we now queue cells on a separate
+      queue for each circuit. This lets us use less slack memory, and
+      will eventually let us be smarter about prioritizing different kinds
+      of traffic.
+    - Reference-count and share copies of address policy entries; only 5%
+      of them were actually distinct.
+    - Tune parameters for cell pool allocation to minimize amount of
+      RAM overhead used.
+    - Keep unused 4k and 16k buffers on free lists, rather than wasting 8k
+      for every single inactive connection_t. Free items from the
+      4k/16k-buffer free lists when they haven't been used for a while.
+    - Make memory debugging information describe more about history
+      of cell allocation, so we can help reduce our memory use.
+    - Be even more aggressive about releasing RAM from small
+      empty buffers. Thanks to our free-list code, this shouldn't be too
+      performance-intensive.
+    - Log malloc statistics from mallinfo() on platforms where it exists.
+    - Use memory pools to allocate cells with better speed and memory
+      efficiency, especially on platforms where malloc() is inefficient.
+    - Add a --with-tcmalloc option to the configure script to link
+      against tcmalloc (if present). Does not yet search for non-system
+      include paths.
+
+  o Performance improvements (socket management):
+    - Count the number of open sockets separately from the number of
+      active connection_t objects. This will let us avoid underusing
+      our allocated connection limit.
+    - We no longer use socket pairs to link an edge connection to an
+      anonymous directory connection or a DirPort test connection.
+      Instead, we track the link internally and transfer the data
+      in-process. This saves two sockets per "linked" connection (at the
+      client and at the server), and avoids the nasty Windows socketpair()
+      workaround.
+    - We were leaking a file descriptor if Tor started with a zero-length
+      cached-descriptors file. Patch by "freddy77".
+
+  o Performance improvements (CPU use):
+    - Never walk through the list of logs if we know that no log target
+      is interested in a given message.
+    - Call routerlist_remove_old_routers() much less often. This should
+      speed startup, especially on directory caches.
+    - Base64 decoding was actually showing up on our profile when parsing
+      the initial descriptor file; switch to an in-process all-at-once
+      implementation that's about 3.5x times faster than calling out to
+      OpenSSL.
+    - Use a slightly simpler string hashing algorithm (copying Python's
+      instead of Java's) and optimize our digest hashing algorithm to take
+      advantage of 64-bit platforms and to remove some possibly-costly
+      voodoo.
+    - When implementing AES counter mode, update only the portions of the
+      counter buffer that need to change, and don't keep separate
+      network-order and host-order counters on big-endian hosts (where
+      they are the same).
+    - Add an in-place version of aes_crypt() so that we can avoid doing a
+      needless memcpy() call on each cell payload.
+    - Use Critical Sections rather than Mutexes for synchronizing threads
+      on win32; Mutexes are heavier-weight, and designed for synchronizing
+      between processes.
+
+  o Performance improvements (bandwidth use):
+    - Don't try to launch new descriptor downloads quite so often when we
+      already have enough directory information to build circuits.
+    - Version 1 directories are no longer generated in full. Instead,
+      authorities generate and serve "stub" v1 directories that list
+      no servers. This will stop Tor versions 0.1.0.x and earlier from
+      working, but (for security reasons) nobody should be running those
+      versions anyway.
+    - Avoid going directly to the directory authorities even if you're a
+      relay, if you haven't found yourself reachable yet or if you've
+      decided not to advertise your dirport yet. Addresses bug 556.
+    - If we've gone 12 hours since our last bandwidth check, and we
+      estimate we have less than 50KB bandwidth capacity but we could
+      handle more, do another bandwidth test.
+    - Support "If-Modified-Since" when answering HTTP requests for
+      directories, running-routers documents, and v2 and v3 networkstatus
+      documents. (There's no need to support it for router descriptors,
+      since those are downloaded by descriptor digest.)
+    - Stop fetching directory info so aggressively if your DirPort is
+      on but your ORPort is off; stop fetching v2 dir info entirely.
+      You can override these choices with the new FetchDirInfoEarly
+      config option.
+
+  o Changed config option behavior (features):
+    - Configuration files now accept C-style strings as values. This
+      helps encode characters not allowed in the current configuration
+      file format, such as newline or #. Addresses bug 557.
+    - Add hidden services and DNSPorts to the list of things that make
+      Tor accept that it has running ports. Change starting Tor with no
+      ports from a fatal error to a warning; we might change it back if
+      this turns out to confuse anybody. Fixes bug 579.
+    - Make PublishServerDescriptor default to 1, so the default doesn't
+      have to change as we invent new directory protocol versions.
+    - Allow people to say PreferTunnelledDirConns rather than
+      PreferTunneledDirConns, for those alternate-spellers out there.
+    - Raise the default BandwidthRate/BandwidthBurst to 5MB/10MB, to
+      accommodate the growing number of servers that use the default
+      and are reaching it.
+    - Make it possible to enable HashedControlPassword and
+      CookieAuthentication at the same time.
+    - When a TrackHostExits-chosen exit fails too many times in a row,
+      stop using it. Fixes bug 437.
+
+  o Changed config option behavior (bugfixes):
+    - Do not read the configuration file when we've only been told to
+      generate a password hash. Fixes bug 643. Bugfix on 0.0.9pre5. Fix
+      based on patch from Sebastian Hahn.
+    - Actually validate the options passed to AuthDirReject,
+      AuthDirInvalid, AuthDirBadDir, and AuthDirBadExit.
+    - Make "ClientOnly 1" config option disable directory ports too.
+    - Don't stop fetching descriptors when FetchUselessDescriptors is
+      set, even if we stop asking for circuits. Bug reported by tup
+      and ioerror.
+    - Servers used to decline to publish their DirPort if their
+      BandwidthRate or MaxAdvertisedBandwidth were below a threshold. Now
+      they look only at BandwidthRate and RelayBandwidthRate.
+    - Treat "2gb" when given in torrc for a bandwidth as meaning 2gb,
+      minus 1 byte: the actual maximum declared bandwidth.
+    - Make "TrackHostExits ." actually work. Bugfix on 0.1.0.x.
+    - Make the NodeFamilies config option work. (Reported by
+      lodger -- it has never actually worked, even though we added it
+      in Oct 2004.)
+    - If Tor is invoked from something that isn't a shell (e.g. Vidalia),
+      now we expand "-f ~/.tor/torrc" correctly. Suggested by Matt Edman.
+
+  o New config options:
+    - New configuration options to override default maximum number of
+      servers allowed on a single IP address. This is important for
+      running a test network on a single host. XXX
+    - Three new config options (AlternateDirAuthority,
+      AlternateBridgeAuthority, and AlternateHSAuthority) that let the
+      user selectively replace the default directory authorities by type,
+      rather than the all-or-nothing replacement that DirServer offers.
+    - New config options AuthDirBadDir and AuthDirListBadDirs for
+      authorities to mark certain relays as "bad directories" in the
+      networkstatus documents. Also supports the "!baddir" directive in
+      the approved-routers file.
+    - New config option V2AuthoritativeDirectory that all v2 directory
+      authorities must set. This lets v3 authorities choose not to serve
+      v2 directory information.
+
+  o Minor features (other):
+    - When we're not serving v2 directory information, there is no reason
+      to actually keep any around. Remove the obsolete files and directory
+      on startup if they are very old and we aren't going to serve them.
+    - When we negotiate a v2 link-layer connection (not yet implemented),
+      accept RELAY_EARLY cells and turn them into RELAY cells if we've
+      negotiated a v1 connection for their next step. Initial steps for
+      proposal 110.
+    - When we have no consensus, check FallbackNetworkstatusFile (defaults
+      to $PREFIX/share/tor/fallback-consensus) for a consensus. This way
+      we can start out knowing some directory caches. We don't ship with
+      a fallback consensus by default though, because it wasn't making
+      bootstrapping take too long while we tried many down relays.
+    - Authorities send back an X-Descriptor-Not-New header in response to
+      an accepted-but-discarded descriptor upload. Partially implements
+      fix for bug 535.
+    - If we find a cached-routers file that's been sitting around for more
+      than 28 days unmodified, then most likely it's a leftover from
+      when we upgraded to 0.2.0.8-alpha. Remove it. It has no good
+      routers anyway.
+    - When we (as a cache) download a descriptor because it was listed
+      in a consensus, remember when the consensus was supposed to expire,
+      and don't expire the descriptor until then.
+    - Optionally (if built with -DEXPORTMALLINFO) export the output
+      of mallinfo via http, as tor/mallinfo.txt. Only accessible
+      from localhost.
+    - Tag every guard node in our state file with the version that
+      we believe added it, or with our own version if we add it. This way,
+      if a user temporarily runs an old version of Tor and then switches
+      back to a new one, she doesn't automatically lose her guards.
+    - When somebody requests a list of statuses or servers, and we have
+      none of those, return a 404 rather than an empty 200.
+    - Merge in some (as-yet-unused) IPv6 address manipulation code. (Patch
+      from croup.)
+    - Add an HSAuthorityRecordStats option that hidden service authorities
+      can use to track statistics of overall hidden service usage without
+      logging information that would be as useful to an attacker.
+    - Allow multiple HiddenServicePort directives with the same virtual
+      port; when they occur, the user is sent round-robin to one
+      of the target ports chosen at random.  Partially fixes bug 393 by
+      adding limited ad-hoc round-robining.
+    - Revamp file-writing logic so we don't need to have the entire
+      contents of a file in memory at once before we write to disk. Tor,
+      meet stdio.
+
+  o Minor bugfixes (other):
+    - Alter the code that tries to recover from unhandled write
+      errors, to not try to flush onto a socket that's given us
+      unhandled errors.
+    - Directory mirrors no longer include a guess at the client's IP
+      address if the connection appears to be coming from the same /24
+      network; it was producing too many wrong guesses.
+    - If we're trying to flush the last bytes on a connection (for
+      example, when answering a directory request), reset the
+      time-to-give-up timeout every time we manage to write something
+      on the socket.
+    - Reject router descriptors with out-of-range bandwidthcapacity or
+      bandwidthburst values.
+    - If we can't expand our list of entry guards (e.g. because we're
+      using bridges or we have StrictEntryNodes set), don't mark relays
+      down when they fail a directory request. Otherwise we're too quick
+      to mark all our entry points down.
+    - Authorities no longer send back "400 you're unreachable please fix
+      it" errors to Tor servers that aren't online all the time. We're
+      supposed to tolerate these servers now.
+    - Let directory authorities startup even when they can't generate
+      a descriptor immediately, e.g. because they don't know their
+      address.
+    - Correctly enforce that elements of directory objects do not appear
+      more often than they are allowed to appear.
+    - Stop allowing hibernating servers to be "stable" or "fast".
+    - On Windows, we were preventing other processes from reading
+      cached-routers while Tor was running. (Reported by janbar)
+    - Check return values from pthread_mutex functions.
+
+  o Controller features:
+    - The GETCONF command now escapes and quotes configuration values
+      that don't otherwise fit into the torrc file.
+    - The SETCONF command now handles quoted values correctly.
+    - Add "GETINFO/desc-annotations/id/<OR digest>" so controllers can
+      ask about source, timestamp of arrival, purpose, etc. We need
+      something like this to help Vidalia not do GeoIP lookups on bridge
+      addresses.
+    - Allow multiple HashedControlPassword config lines, to support
+      multiple controller passwords.
+    - Accept LF instead of CRLF on controller, since some software has a
+      hard time generating real Internet newlines.
+    - Add GETINFO values for the server status events
+      "REACHABILITY_SUCCEEDED" and "GOOD_SERVER_DESCRIPTOR". Patch from
+      Robert Hogan.
+    - There is now an ugly, temporary "desc/all-recent-extrainfo-hack"
+      GETINFO for Torstat to use until it can switch to using extrainfos.
+    - New config option CookieAuthFile to choose a new location for the
+      cookie authentication file, and config option
+      CookieAuthFileGroupReadable to make it group-readable.
+    - Add a SOURCE_ADDR field to STREAM NEW events so that controllers can
+      match requests to applications. Patch from Robert Hogan.
+    - Add a RESOLVE command to launch hostname lookups. Original patch
+      from Robert Hogan.
+    - Add GETINFO status/enough-dir-info to let controllers tell whether
+      Tor has downloaded sufficient directory information. Patch from Tup.
+    - You can now use the ControlSocket option to tell Tor to listen for
+      controller connections on Unix domain sockets on systems that
+      support them. Patch from Peter Palfrader.
+    - New "GETINFO address-mappings/*" command to get address mappings
+      with expiry information. "addr-mappings/*" is now deprecated.
+      Patch from Tup.
+    - Add a new config option __DisablePredictedCircuits designed for
+      use by the controller, when we don't want Tor to build any circuits
+      preemptively.
+    - Let the controller specify HOP=%d as an argument to ATTACHSTREAM,
+      so we can exit from the middle of the circuit.
+    - Implement "getinfo status/circuit-established".
+    - Implement "getinfo status/version/..." so a controller can tell
+      whether the current version is recommended, and whether any versions
+      are good, and how many authorities agree. Patch from "shibz".
+    - Controllers should now specify cache=no or cache=yes when using
+      the +POSTDESCRIPTOR command.
+    - Add a "PURPOSE=" argument to "STREAM NEW" events, as suggested by
+      Robert Hogan. Fixes the first part of bug 681.
+    - When reporting clock skew, and we know that the clock is _at least
+      as skewed_ as some value, but we don't know the actual value,
+      report the value as a "minimum skew."
+
+  o Controller bugfixes:
+    - Generate "STATUS_SERVER" events rather than misspelled
+      "STATUS_SEVER" events. Caught by mwenge.
+    - Reject controller commands over 1MB in length, so rogue
+      processes can't run us out of memory.
+    - Change the behavior of "getinfo status/good-server-descriptor"
+      so it doesn't return failure when any authority disappears.
+    - Send NAMESERVER_STATUS messages for a single failed nameserver
+      correctly.
+    - When the DANGEROUS_VERSION controller status event told us we're
+      running an obsolete version, it used the string "OLD" to describe
+      it. Yet the "getinfo" interface used the string "OBSOLETE". Now use
+      "OBSOLETE" in both cases.
+    - Respond to INT and TERM SIGNAL commands before we execute the
+      signal, in case the signal shuts us down. We had a patch in
+      0.1.2.1-alpha that tried to do this by queueing the response on
+      the connection's buffer before shutting down, but that really
+      isn't the same thing at all. Bug located by Matt Edman.
+    - Provide DNS expiry times in GMT, not in local time. For backward
+      compatibility, ADDRMAP events only provide GMT expiry in an extended
+      field. "GETINFO address-mappings" always does the right thing.
+    - Use CRLF line endings properly in NS events.
+    - Make 'getinfo fingerprint' return a 551 error if we're not a
+      server, so we match what the control spec claims we do. Reported
+      by daejees.
+    - Fix a typo in an error message when extendcircuit fails that
+      caused us to not follow the \r\n-based delimiter protocol. Reported
+      by daejees.
+    - When tunneling an encrypted directory connection, and its first
+      circuit fails, do not leave it unattached and ask the controller
+      to deal. Fixes the second part of bug 681.
+    - Treat some 403 responses from directory servers as INFO rather than
+      WARN-severity events.
+
+  o Portability / building / compiling:
+    - When building with --enable-gcc-warnings, check for whether Apple's
+      warning "-Wshorten-64-to-32" is available.
+    - Support compilation to target iPhone; patch from cjacker huang.
+      To build for iPhone, pass the --enable-iphone option to configure.
+    - Detect non-ASCII platforms (if any still exist) and refuse to
+      build there: some of our code assumes that 'A' is 65 and so on.
+    - Clear up some MIPSPro compiler warnings.
+    - Make autoconf search for libevent, openssl, and zlib consistently.
+    - Update deprecated macros in configure.in.
+    - When warning about missing headers, tell the user to let us
+      know if the compile succeeds anyway, so we can downgrade the
+      warning.
+    - Include the current subversion revision as part of the version
+      string: either fetch it directly if we're in an SVN checkout, do
+      some magic to guess it if we're in an SVK checkout, or use
+      the last-detected version if we're building from a .tar.gz.
+      Use this version consistently in log messages.
+    - Correctly report platform name on Windows 95 OSR2 and Windows 98 SE.
+    - Read resolv.conf files correctly on platforms where read() returns
+      partial results on small file reads.
+    - Build without verbose warnings even on gcc 4.2 and 4.3.
+    - On Windows, correctly detect errors when listing the contents of
+      a directory. Fix from lodger.
+    - Run 'make test' as part of 'make dist', so we stop releasing so
+      many development snapshots that fail their unit tests.
+    - Add support to detect Libevent versions in the 1.4.x series
+      on mingw.
+    - Add command-line arguments to unit-test executable so that we can
+      invoke any chosen test from the command line rather than having
+      to run the whole test suite at once; and so that we can turn on
+      logging for the unit tests.
+    - Do not automatically run configure from autogen.sh. This
+      non-standard behavior tended to annoy people who have built other
+      programs.
+
+  o Logging improvements:
+    - When we haven't had any application requests lately, don't bother
+      logging that we have expired a bunch of descriptors.
+    - When attempting to open a logfile fails, tell us why.
+    - Only log guard node status when guard node status has changed.
+    - Downgrade the 3 most common "INFO" messages to "DEBUG". This will
+      make "INFO" 75% less verbose.
+    - When SafeLogging is disabled, log addresses along with all TLS
+      errors.
+    - Report TLS "zero return" case as a "clean close" and "IO error"
+      as a "close". Stop calling closes "unexpected closes": existing
+      Tors don't use SSL_close(), so having a connection close without
+      the TLS shutdown handshake is hardly unexpected.
+    - When we receive a consensus from the future, warn about skew.
+    - Make "not enough dir info yet" warnings describe *why* Tor feels
+      it doesn't have enough directory info yet.
+    - On the USR1 signal, when dmalloc is in use, log the top 10 memory
+      consumers. (We already do this on HUP.)
+    - Give more descriptive well-formedness errors for out-of-range
+      hidden service descriptor/protocol versions.
+    - Stop recommending that every server operator send mail to tor-ops.
+      Resolves bug 597. Bugfix on 0.1.2.x.
+    - Improve skew reporting: try to give the user a better log message
+      about how skewed they are, and how much this matters.
+    - New --quiet command-line option to suppress the default console log.
+      Good in combination with --hash-password.
+    - Don't complain that "your server has not managed to confirm that its
+      ports are reachable" if we haven't been able to build any circuits
+      yet.
+    - Detect the reason for failing to mmap a descriptor file we just
+      wrote, and give a more useful log message.  Fixes bug 533.
+    - Always prepend "Bug: " to any log message about a bug.
+    - When dumping memory usage, list bytes used in buffer memory
+      free-lists.
+    - When running with dmalloc, dump more stats on hup and on exit.
+    - Put a platform string (e.g. "Linux i686") in the startup log
+      message, so when people paste just their logs, we know if it's
+      OpenBSD or Windows or what.
+    - When logging memory usage, break down memory used in buffers by
+      buffer type.
+    - When we are reporting the DirServer line we just parsed, we were
+      logging the second stanza of the key fingerprint, not the first.
+    - Even though Windows is equally happy with / and \ as path separators,
+      try to use \ consistently on Windows and / consistently on Unix: it
+      makes the log messages nicer.
+     - On OSX, stop warning the user that kqueue support in libevent is
+      "experimental", since it seems to have worked fine for ages.
+
+  o Contributed scripts and tools:
+    - Update linux-tor-prio.sh script to allow QoS based on the uid of
+      the Tor process. Patch from Marco Bonetti with tweaks from Mike
+      Perry.
+    - Include the "tor-ctrl.sh" bash script by Stefan Behte to provide
+      Unix users an easy way to script their Tor process (e.g. by
+      adjusting bandwidth based on the time of the day).
+    - In the exitlist script, only consider the most recently published
+      server descriptor for each server. Also, when the user requests
+      a list of servers that _reject_ connections to a given address,
+      explicitly exclude the IPs that also have servers that accept
+      connections to that address. Resolves bug 405.
+    - Include a new contrib/tor-exit-notice.html file that exit relay
+      operators can put on their website to help reduce abuse queries.
+
+  o Newly deprecated features:
+    - The status/version/num-versioning and status/version/num-concurring
+      GETINFO controller options are no longer useful in the v3 directory
+      protocol: treat them as deprecated, and warn when they're used.
+    - The RedirectExits config option is now deprecated.
+
+  o Removed features:
+    - Drop the old code to choke directory connections when the
+      corresponding OR connections got full: thanks to the cell queue
+      feature, OR conns don't get full any more.
+    - Remove the old "dns worker" server DNS code: it hasn't been default
+      since 0.1.2.2-alpha, and all the servers are using the new
+      eventdns code.
+    - Remove the code to generate the oldest (v1) directory format.
+    - Remove support for the old bw_accounting file: we've been storing
+      bandwidth accounting information in the state file since
+      0.1.2.5-alpha. This may result in bandwidth accounting errors
+      if you try to upgrade from 0.1.1.x or earlier, or if you try to
+      downgrade to 0.1.1.x or earlier.
+    - Drop support for OpenSSL version 0.9.6. Just about nobody was using
+      it, it had no AES, and it hasn't seen any security patches since
+      2004.
+    - Stop overloading the circuit_t.onionskin field for both "onionskin
+      from a CREATE cell that we are waiting for a cpuworker to be
+      assigned" and "onionskin from an EXTEND cell that we are going to
+      send to an OR as soon as we are connected". Might help with bug 600.
+    - Remove the tor_strpartition() function: its logic was confused,
+      and it was only used for one thing that could be implemented far
+      more easily.
+    - Remove the contrib scripts ExerciseServer.py, PathDemo.py,
+      and TorControl.py, as they use the old v0 controller protocol,
+      and are obsoleted by TorFlow anyway.
+    - Drop support for v1 rendezvous descriptors, since we never used
+      them anyway, and the code has probably rotted by now. Based on
+      patch from Karsten Loesing.
+    - Stop allowing address masks that do not correspond to bit prefixes.
+      We have warned about these for a really long time; now it's time
+      to reject them. (Patch from croup.)
+    - Remove an optimization in the AES counter-mode code that assumed
+      that the counter never exceeded 2^68. When the counter can be set
+      arbitrarily as an IV (as it is by Karsten's new hidden services
+      code), this assumption no longer holds.
+    - Disable the SETROUTERPURPOSE controller command: it is now
+      obsolete.
+
+
 Changes in version 0.1.2.19 - 2008-01-17
   Tor 0.1.2.19 fixes a huge memory leak on exit relays, makes the default
   exit policy a little bit more conservative so it's safer to run an



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