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[tor-talk] Tor is released

Hi, all!

There's a new alpha Tor release! Because it's an alpha, you should
only run it if you're ready to find more bugs than usual, and report
them on trac.torproject.org.

The source code is available from the usual place at
https://www.torproject.org/download/tor/; if you build Tor from
source, why not give it a try? And if you don't build Tor from source,
packages should be ready over the coming days, with a Tor Browser
alpha release likely in the next couple of weeks.

Here's what's new:

Changes in version - 2019-05-22
  This is the first alpha in the 0.4.1.x series. It introduces
  lightweight circuit padding to make some onion-service circuits harder
  to distinguish, includes a new "authenticated SENDME" feature to make
  certain denial-of-service attacks more difficult, and improves
  performance in several areas.

  o Major features (circuit padding):
    - Onion service clients now add padding cells at the start of their
      INTRODUCE and RENDEZVOUS circuits, to make those circuits' traffic
      look more like general purpose Exit traffic. The overhead for this
      is 2 extra cells in each direction for RENDEZVOUS circuits, and 1
      extra upstream cell and 10 downstream cells for INTRODUCE
      circuits. This feature is only enabled when also supported by the
      circuit's middle node. (Clients may specify fixed middle nodes
      with the MiddleNodes option, and may force-disable this feature
      with the CircuitPadding torrc.) Closes ticket 28634.

  o Major features (code organization):
    - Tor now includes a generic publish-subscribe message-passing
      subsystem that we can use to organize intermodule dependencies. We
      hope to use this to reduce dependencies between modules that don't
      need to be related, and to generally simplify our codebase. Closes
      ticket 28226.

  o Major features (controller protocol):
    - Controller commands are now parsed using a generalized parsing
      subsystem. Previously, each controller command was responsible for
      parsing its own input, which led to strange inconsistencies.
      Closes ticket 30091.

  o Major features (flow control):
    - Implement authenticated SENDMEs as detailed in proposal 289. A
      SENDME cell now includes the digest of the traffic that it
      acknowledges, so that once an end point receives the SENDME, it
      can confirm the other side's knowledge of the previous cells that
      were sent, and prevent certain types of denial-of-service attacks.
      This behavior is controlled by two new consensus parameters: see
      the proposal for more details. Fixes ticket 26288.

  o Major features (performance):
    - Our node selection algorithm now excludes nodes in linear time.
      Previously, the algorithm was quadratic, which could slow down
      heavily used onion services. Closes ticket 30307.

  o Major features (performance, RNG):
    - Tor now constructs a fast secure pseudorandom number generator for
      each thread, to use when performance is critical. This PRNG is
      based on AES-CTR, using a buffering construction similar to
      libottery and the (newer) OpenBSD arc4random() code. It
      outperforms OpenSSL 1.1.1a's CSPRNG by roughly a factor of 100 for
      small outputs. Although we believe it to be cryptographically
      strong, we are only using it when necessary for performance.
      Implements tickets 29023 and 29536.

  o Major bugfixes (onion service v3):
    - Fix an unreachable bug in which an introduction point could try to
      send an INTRODUCE_ACK with a status code that Trunnel would refuse
      to encode, leading the relay to assert(). We've consolidated the
      ABI values into Trunnel now. Fixes bug 30454; bugfix
    - Clients can now handle unknown status codes from INTRODUCE_ACK
      cells. (The NACK behavior will stay the same.) This will allow us
      to extend status codes in the future without breaking the normal
      client behavior. Fixes another part of bug 30454; bugfix

  o Minor features (circuit padding):
    - We now use a fast PRNG when scheduling circuit padding. Part of
      ticket 28636.
    - Allow the padding machine designer to pick the edges of their
      histogram instead of trying to compute them automatically using an
      exponential formula. Resolves some undefined behavior in the case
      of small histograms and allows greater flexibility on machine
      design. Closes ticket 29298; bugfix on
    - Allow circuit padding machines to hold a circuit open until they
      are done padding it. Closes ticket 28780.

  o Minor features (compile-time modules):
    - Add a "--list-modules" command to print a list of which compile-
      time modules are enabled. Closes ticket 30452.

  o Minor features (continuous integration):
    - Remove sudo configuration lines from .travis.yml as they are no
      longer needed with current Travis build environment. Resolves
      issue 30213.
    - In Travis, show stem's tor log after failure. Closes ticket 30234.

  o Minor features (controller):
    - Add onion service version 3 support to the HSFETCH command.
      Previously, only version 2 onion services were supported. Closes
      ticket 25417. Patch by Neel Chauhan.

  o Minor features (debugging):
    - Introduce tor_assertf() and tor_assertf_nonfatal() to enable
      logging of additional information during assert failure. Now we
      can use format strings to include information for trouble
      shooting. Resolves ticket 29662.

  o Minor features (defense in depth):
    - In smartlist_remove_keeporder(), set unused pointers to NULL, in
      case a bug causes them to be used later. Closes ticket 30176.
      Patch from Tobias Stoeckmann.
    - Tor now uses a cryptographically strong PRNG even for decisions
      that we do not believe are security-sensitive. Previously, for
      performance reasons, we had used a trivially predictable linear
      congruential generator algorithm for certain load-balancing and
      statistical sampling decisions. Now we use our fast RNG in those
      cases. Closes ticket 29542.

  o Minor features (developer tools):
    - Tor's "practracker" test script now checks for files and functions
      that seem too long and complicated. Existing overlong functions
      and files are accepted for now, but should eventually be
      refactored. Closes ticket 29221.
    - Add some scripts used for git maintenance to scripts/git. Closes
      ticket 29391.
    - Call practracker from pre-push and pre-commit git hooks to let
      developers know if they made any code style violations. Closes
      ticket 30051.
    - Add a script to check that each header has a well-formed and
      unique guard macro. Closes ticket 29756.

  o Minor features (geoip):
    - Update geoip and geoip6 to the May 13 2019 Maxmind GeoLite2
      Country database. Closes ticket 30522.

  o Minor features (HTTP tunnel):
    - Return an informative web page when the HTTPTunnelPort is used as
      an HTTP proxy. Closes ticket 27821, patch by "eighthave".

  o Minor features (IPv6, v3 onion services):
    - Make v3 onion services put IPv6 addresses in service descriptors.
      Before this change, service descriptors only contained IPv4
      addresses. Implements 26992.

  o Minor features (modularity):
    - The "--disable-module-dirauth" compile-time option now disables
      even more dirauth-only code. Closes ticket 30345.

  o Minor features (performance):
    - Use OpenSSL's implementations of SHA3 when available (in OpenSSL
      1.1.1 and later), since they tend to be faster than tiny-keccak.
      Closes ticket 28837.

  o Minor features (testing):
    - Tor's unit test code now contains helper functions to replace the
      PRNG with a deterministic or reproducible version for testing.
      Previously, various tests implemented this in various ways.
      Implements ticket 29732.
    - We now have a script, cov-test-determinism.sh, to identify places
      where our unit test coverage has become nondeterministic. Closes
      ticket 29436.
    - Check that representative subsets of values of `int` and `unsigned
      int` can be represented by `void *`. Resolves issue 29537.

  o Minor bugfixes (bridge authority):
    - Bridge authorities now set bridges as running or non-running when
      about to dump their status to a file. Previously, they set bridges
      as running in response to a GETINFO command, but those shouldn't
      modify data structures. Fixes bug 24490; bugfix on
      Patch by Neel Chauhan.

  o Minor bugfixes (channel padding statistics):
    - Channel padding write totals and padding-enabled totals are now
      counted properly in relay extrainfo descriptors. Fixes bug 29231;
      bugfix on

  o Minor bugfixes (circuit padding):
    - Add a "CircuitPadding" torrc option to disable circuit padding.
      Fixes bug 28693; bugfix on
    - Allow circuit padding machines to specify that they do not
      contribute much overhead, and provide consensus flags and torrc
      options to force clients to only use these low overhead machines.
      Fixes bug 29203; bugfix on
    - Provide a consensus parameter to fully disable circuit padding, to
      be used in emergency network overload situations. Fixes bug 30173;
      bugfix on
    - The circuit padding subsystem will no longer schedule padding if
      dormant mode is enabled. Fixes bug 28636; bugfix on
    - Inspect a circuit-level cell queue before sending padding, to
      avoid sending padding while too much data is already queued. Fixes
      bug 29204; bugfix on
    - Avoid calling monotime_absolute_usec() in circuit padding machines
      that do not use token removal or circuit RTT estimation. Fixes bug
      29085; bugfix on

  o Minor bugfixes (compilation, unusual configurations):
    - Avoid failures when building with the ALL_BUGS_ARE_FATAL option
      due to missing declarations of abort(), and prevent other such
      failures in the future. Fixes bug 30189; bugfix on

  o Minor bugfixes (controller protocol):
    - Teach the controller parser to distinguish an object preceded by
      an argument list from one without. Previously, it couldn't
      distinguish an argument list from the first line of a multiline
      object. Fixes bug 29984; bugfix on

  o Minor bugfixes (directory authority, ipv6):
    - Directory authorities with IPv6 support now always mark themselves
      as reachable via IPv6. Fixes bug 24338; bugfix on
      Patch by Neel Chauhan.

  o Minor bugfixes (documentation):
    - Improve the documentation for using MapAddress with ".exit". Fixes
      bug 30109; bugfix on
    - Improve the monotonic time module and function documentation to
      explain what "monotonic" actually means, and document some results
      that have surprised people. Fixes bug 29640; bugfix
    - Use proper formatting when providing an example on quoting options
      that contain whitespace. Fixes bug 29635; bugfix on

  o Minor bugfixes (logging):
    - Do not log a warning when running with an OpenSSL version other
      than the one Tor was compiled with, if the two versions should be
      compatible. Previously, we would warn whenever the version was
      different. Fixes bug 30190; bugfix on
    - Warn operators when the MyFamily option is set but ContactInfo is
      missing, as the latter should be set too. Fixes bug 25110; bugfix

  o Minor bugfixes (memory leak):
    - Avoid a minor memory leak that could occur on relays when failing
      to create a "keys" directory. Fixes bug 30148; bugfix

  o Minor bugfixes (onion services):
    - Avoid a GCC 9.1.1 warning (and possible crash depending on libc
      implemenation) when failing to load an onion service client
      authorization file. Fixes bug 30475; bugfix on
    - When refusing to launch a controller's HSFETCH request because of
      rate-limiting, respond to the controller with a new response,
      "QUERY_RATE_LIMITED". Previously, we would log QUERY_NO_HSDIR for
      this case. Fixes bug 28269; bugfix on Patch by
      Neel Chauhan.
    - When relaunching a circuit to a rendezvous service, mark the
      circuit as needing high-uptime routers as appropriate. Fixes bug
      17357; bugfix on Patch by Neel Chauhan.
    - Stop ignoring IPv6 link specifiers sent to v3 onion services.
      (IPv6 support for v3 onion services is still incomplete: see
      ticket 23493 for details.) Fixes bug 23588; bugfix on Patch by Neel Chauhan.

  o Minor bugfixes (onion services, performance):
    - When building circuits to onion services, call tor_addr_parse()
      less often. Previously, we called tor_addr_parse() in
      circuit_is_acceptable() even if its output wasn't used. This
      change should improve performance when building circuits. Fixes
      bug 22210; bugfix on Patch by Neel Chauhan.

  o Minor bugfixes (performance):
    - When checking whether a node is a bridge, use a fast check to make
      sure that its identity is set. Previously, we used a constant-time
      check, which is not necessary in this case. Fixes bug 30308;
      bugfix on

  o Minor bugfixes (pluggable transports):
    - Tor now sets TOR_PT_EXIT_ON_STDIN_CLOSE=1 for client transports as
      well as servers. Fixes bug 25614; bugfix on

  o Minor bugfixes (probability distributions):
    - Refactor and improve parts of the probability distribution code
      that made Coverity complain. Fixes bug 29805; bugfix

  o Minor bugfixes (python):
    - Stop assuming that /usr/bin/python3 exists. For scripts that work
      with python2, use /usr/bin/python. Otherwise, use /usr/bin/env
      python3. Fixes bug 29913; bugfix on

  o Minor bugfixes (relay):
    - When running as a relay, if IPv6Exit is set to 1 while ExitRelay
      is auto, act as if ExitRelay is 1. Previously, we would ignore
      IPv6Exit if ExitRelay was 0 or auto. Fixes bug 29613; bugfix on Patch by Neel Chauhan.

  o Minor bugfixes (stats):
    - When ExtraInfoStatistics is 0, stop including bandwidth usage
      statistics, GeoIPFile hashes, ServerTransportPlugin lines, and
      bridge statistics by country in extra-info documents. Fixes bug
      29018; bugfix on

  o Minor bugfixes (testing):
    - Call setrlimit() to disable core dumps in test_bt_cl.c. Previously
      we used `ulimit -c` in test_bt.sh, which violates POSIX shell
      compatibility. Fixes bug 29061; bugfix on
    - Fix some incorrect code in the v3 onion service unit tests. Fixes
      bug 29243; bugfix on
    - In the "routerkeys/*" tests, check the return values of mkdir()
      for possible failures. Fixes bug 29939; bugfix on
      Found by Coverity as CID 1444254.
    - Split test_utils_general() into several smaller test functions.
      This makes it easier to perform resource deallocation on assert
      failure, and fixes Coverity warnings CID 1444117 and CID 1444118.
      Fixes bug 29823; bugfix on

  o Minor bugfixes (tor-resolve):
    - Fix a memory leak in tor-resolve that could happen if Tor gave it
      a malformed SOCKS response. (Memory leaks in tor-resolve don't
      actually matter, but it's good to fix them anyway.) Fixes bug
      30151; bugfix on

  o Code simplification and refactoring:
    - Abstract out the low-level formatting of replies on the control
      port. Implements ticket 30007.
    - Add several assertions in an attempt to fix some Coverity
      warnings. Closes ticket 30149.
    - Introduce a connection_dir_buf_add() helper function that checks
      for compress_state of dir_connection_t and automatically writes a
      string to directory connection with or without compression.
      Resolves issue 28816.
    - Make the base32_decode() API return the number of bytes written,
      for consistency with base64_decode(). Closes ticket 28913.
    - Move most relay-only periodic events out of mainloop.c into the
      relay subsystem. Closes ticket 30414.
    - Refactor and encapsulate parts of the codebase that manipulate
      crypt_path_t objects. Resolves issue 30236.
    - Refactor several places in our code that Coverity incorrectly
      believed might have memory leaks. Closes ticket 30147.
    - Remove redundant return values in crypto_format, and the
      associated return value checks elsewhere in the code. Make the
      implementations in crypto_format consistent, and remove redundant
      code. Resolves ticket 29660.
    - Rename tor_mem_is_zero() to fast_mem_is_zero(), to emphasize that
      it is not a constant-time function. Closes ticket 30309.
    - Replace hs_desc_link_specifier_t with link_specifier_t, and remove
      all hs_desc_link_specifier_t-specific code. Fixes bug 22781;
      bugfix on
    - Simplify v3 onion service link specifier handling code. Fixes bug
      23576; bugfix on
    - Split crypto_digest.c into NSS code, OpenSSL code, and shared
      code. Resolves ticket 29108.
    - Split control.c into several submodules, in preparation for
      distributing its current responsibilities throughout the codebase.
      Closes ticket 29894.
    - Start to move responsibility for knowing about periodic events to
      the appropriate subsystems, so that the mainloop doesn't need to
      know all the periodic events in the rest of the codebase.
      Implements tickets 30293 and 30294.

  o Documentation:
    - Document how to find git commits and tags for bug fixes in
      CodingStandards.md. Update some file documentation. Closes
      ticket 30261.

  o Removed features:
    - Remove the linux-tor-prio.sh script from contrib/operator-tools
      directory. Resolves issue 29434.
    - Remove the obsolete OpenSUSE initscript. Resolves issue 30076.
    - Remove the obsolete script at contrib/dist/tor.sh.in. Resolves
      issue 30075.

  o Code simplification and refactoring (shell scripts):
    - Clean up many of our shell scripts to fix shellcheck warnings.
      These include autogen.sh (ticket 26069), test_keygen.sh (ticket
      29062), test_switch_id.sh (ticket 29065), test_rebind.sh (ticket
      29063), src/test/fuzz/minimize.sh (ticket 30079), test_rust.sh
      (ticket 29064), torify (ticket 29070), asciidoc-helper.sh (29926),
      fuzz_multi.sh (30077), fuzz_static_testcases.sh (ticket 29059),
      nagios-check-tor-authority-cert (ticket 29071),
      src/test/fuzz/fixup_filenames.sh (ticket 30078), test-network.sh
      (ticket 29060), test_key_expiration.sh (ticket 30002),
      zero_length_keys.sh (ticket 29068), and test_workqueue_*.sh
      (ticket 29067).

  o Testing (chutney):
    - In "make test-network-all", test IPv6-only v3 single onion
      services, using the chutney network single-onion-v23-ipv6-md.
      Closes ticket 27251.
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