Full round of edits on ChangeLog

  improves support for IPv6, address discovery and self-testing, code

  metrics and tracing.

  This release also fixes TROVE-2020-005, a security issue that could be

  used, under certain cases, by an adversary to observe traffic patterns

  on a limited number of circuits intended for a different relay. To

  mount this attack, the adversary would need to actively extend

  circuits to an incorrect address, as well as compromise a relay's

  legacy RSA-1024 key. We'll be backporting this fix to other release

  series soon, after it has had some testing.

  Here are the changes since 0.4.4.5.

  o Major features (build):

    - When building Tor, first link all object files into a single

      static library. This may help with embedding Tor in other

      programs. Note that most Tor functions do not constitute a part of

      a stable or supported API: Only those functions in tor_api.h

      should be used if embedding Tor. Closes ticket 40127.

  o Major features (metrics):

    - Introduce a new MetricsPort which exposes, through an HTTP GET

      /metrics request, a series of metrics that tor collects at

      runtime. At the moment, the only supported output format is

      Prometheus data model. Closes ticket 40063. See the manual page

      for more information.

    - Introduce a new MetricsPort which exposes, through an HTTP

      interface, a series of metrics that tor collects at runtime. At

      the moment, the only supported output format is Prometheus data

      model. Closes ticket 40063. See the manual page for more

      information and security considerations.

  o Major features (relay, IPv6):

    - The torrc option Address now supports IPv6. By doing so, we've

      also unified the interface to find our address to support IPv4,

      IPv6 and hostname. Closes ticket 33233.

    - The torrc option Address now supports IPv6. This unifies our

      address discovery interface to support IPv4, IPv6, and hostnames.

      Closes ticket 33233.

    - Launch IPv4 and IPv6 ORPort self-test circuits on relays and

      bridges. Closes ticket 33222.

    - Relays now automatically bind on IPv6 for their ORPort unless

    - Relays now automatically bind on IPv6 for their ORPort, unless

      specified otherwise with the IPv4Only flag. Closes ticket 33246.

    - When a relay with IPv6 support opens a connection to another

      relay, and the extend cell lists both IPv4 and IPv6 addresses, the

      first relay now picks randomly which address to use. Closes

      ticket 33220.

    - Relays now track their IPv6 ORPort separately from the reachability

      of their IPv4 ORPort. They will not publish a descriptor unless

      _both_ ports appear to be externally reachable. Closes

      ticket 34067.

    - When a relay with IPv6 support is told to open a connection to

      another relay, and the extend cell lists both IPv4 and IPv6

      addresses, the first relay now picks randomly which address to

      use. Closes ticket 33220.

    - Relays now track their IPv6 ORPort reachability separately from

      the reachability of their IPv4 ORPort. They will not publish a

      descriptor unless _both_ ports appear to be externally reachable.

      Closes ticket 34067.

  o Major features (tracing):

    - Add a tracing library with USDT and LTTng-UST support. Few

      tracepoints were added in the circuit subsystem. More will come

      incrementally. This feature is compiled out by default. It needs

    - Add event-tracing library support for USDT and LTTng-UST, and a

      few tracepoints in the circuit subsystem. More will come

      incrementally. This feature is compiled out by default: it needs

      to be enabled at configure time. See documentation in

      doc/HACKING/Tracing.md. Closes ticket 32910.

  o Major bugfix (TLS, buffer):

  o Major bugfixes (security):

    - When completing a channel, relays now check more thoroughly to

      make sure that it matches any pending circuits before attaching

      those circuits. Previously, address correctness and Ed25519

      identities were not checked in this case, but only when extending

      circuits on an existing channel. Fixes bug 40080; bugfix on

      0.2.7.2-alpha. Resolves TROVE-2020-005.

  o Major bugfixes (TLS, buffer):

    - When attempting to read N bytes on a TLS connection, really try to

      read those N bytes. Before that, Tor would stop reading after the

      first TLS record which can be smaller than N bytes even though

      more data was waiting on the TLS connection socket. The remaining

      data would have been read at the next mainloop event. Fixes bug

      40006; bugfix on 0.1.0.5-rc.

      read all N bytes. Previously, Tor would stop reading after the

      first TLS record, which can be smaller than the N bytes requested,

      and not check for more data until the next mainloop event. Fixes

      bug 40006; bugfix on 0.1.0.5-rc.

  o Minor features (address discovery):

    - If no Address statements are found, relays now prioritize guessing

      hostname is used. Closes ticket 33238.

  o Minor features (admin tools):

    - Add new --format argument to -key-expiration option to allow

      specifying the time format of expiration date. Adds Unix timestamp

      format support. Patch by Daniel Pinto. Closes ticket 30045.

    - Add a new --format argument to -key-expiration option to allow

      specifying the time format of the expiration date. Adds Unix

      timestamp format support. Patch by Daniel Pinto. Closes

      ticket 30045.

  o Minor features (bootstrap reporting):

    - When reporting bootstrapping status on a relay, do not consider

      connections that have never been the target of an origin circuit.

      Previously, all connection failures were treated as potential

      bootstrapping failures, including those that had been opened

      bootstrapping failures, including connections had been opened

      because of client requests. Closes ticket 25061.

  o Minor features (build):

    - If the configure script has given any warnings, remind the user

      about them at the end of the script. Related to 40138.

    - When running the configure script, try to detect version

      mismatches between the openssl headers and libraries, and suggest

      mismatches between the OpenSSL headers and libraries, and suggest

      that the user should try "--with-openssl-dir". Closes 40138.

    - When building Tor, first link all object files into a single

      static library. This may help with embedding Tor in other

      programs. Note that most Tor functions do not constitute a part of

      a stable or supported API: Only those functions in tor_api.h

      should be used if embedding Tor. Closes ticket 40127.

    - If the configure script has given any warnings, remind the user

      about them at the end of the script. Related to 40138.

  o Minor features (configuration):

    - Allow the using wildcards (* and ?) with the %include option on

      configuration files. Closes ticket 25140. Patch by Daniel Pinto.

    - Allows configuration options EntryNodes, ExcludeNodes,

    - Allow the configuration options EntryNodes, ExcludeNodes,

      ExcludeExitNodes, ExitNodes, MiddleNodes, HSLayer2Nodes and

      HSLayer3Nodes to be specified multiple times. Closes ticket 28361.

      Patch by Daniel Pinto.

  o Minor features (control port):

    - Add a DROPTIMEOUTS control port command to drop circuit build

      timeout history and reset the timeout. Closes ticket 40002.

    - Add a DROPTIMEOUTS command to drop circuit build timeout history

      and reset the current timeout. Closes ticket 40002.

    - When a stream enters the AP_CONN_STATE_CONTROLLER_WAIT status,

      send a control port event CONTROLLER_WAIT. Closes ticket 32190.

      Patch by Neel Chauhan.

    - Introduce "GETINFO address/v4" and "GETINFO address/v6" in the

      control port to fetch the Tor host's respective IPv4 or IPv6

      address. We keep "GETINFO address" for backwords-compatibility

      which retains the current behavior. Closes ticket 40039. Patch by

      send a control port event. Closes ticket 32190. Patch by

      Neel Chauhan.

    - Introduce GETINFO "stats/ntor/{assigned/requested}" and

      "stats/tap/{assigned/requested}" to get the NTor and TAP circuit

      onion handshake rephist values respectively. Closes ticket 28279.

      Patch by Neel Chauhan.

      onion handshake counts respectively. Closes ticket 28279. Patch by

      Neel Chauhan.

  o Minor features (controller, IPv6):

  o Minor features (control port, IPv6):

    - Tor relays now try to report to the controller when they are

      launching an IPv6 self-test. Closes ticket 34068.

    - Introduce "GETINFO address/v4" and "GETINFO address/v6" in the

      control port to fetch the Tor host's respective IPv4 or IPv6

      address. We keep "GETINFO address" for backwards-compatibility.

      Closes ticket 40039. Patch by Neel Chauhan.

  o Minor features (directory authorities):

    - Authorities now list a different set of protocols as required and

      recommended. These lists are chosen so that only truly recommended

      and/or required protocols are included, and so that clients using

      0.2.9 or later will continue to work (even though they are not

      supported), whereas only relays running 0.3.5 or later will meet

      the requirements. Closes ticket 40162.

    - Add a new consensus method that removes the unecessary = padding

      from ntor-onion-key. Closes ticket 7869. Patch by Daniel Pinto.

      recommended. These lists have been chosen so that only truly

      recommended and/or required protocols are included, and so that

      clients using 0.2.9 or later will continue to work (even though

      they are not supported), whereas only relays running 0.3.5 or

      later will meet the requirements. Closes ticket 40162.

    - Add a new consensus method 30 that removes the unnecessary "="

      padding from ntor-onion-key. Closes ticket 7869. Patch by

      Daniel Pinto.

    - Directory authorities now reject descriptors from relays running

      Tor versions from the 0.4.1 series, but still allow the 0.3.5

      series. Resolves ticket 34357. Patch by Neel Chauhan.

      Tor versions from the obsolete 0.4.1 series. Resolves ticket

      34357. Patch by Neel Chauhan.

    - Make it possible to specify multiple ConsensusParams torrc lines.

      Now directory authority operators can for example put the main

      ConsensusParams config in one torrc file and then add to it from a

      from checking whether other relays are running. A new

      AuthDirTestReachability option can be used to disable these

      checks. Closes ticket 34445.

    - When looking for possible sybil attacks, also consider IPv6

    - When looking for possible Sybil attacks, also consider IPv6

      addresses. Two routers are considered to have "the same" address

      by this metric if they are in the same /64 network. Patch from

      Maurice Pibouin. Closes ticket 7193.

  o Minor features (directory authorities, IPv6):

    - Make authorities add their IPv6 ORPort (if any) to the trusted dir

      servers list. Authorities currently add themselves to the trusted

      dir servers list, but they only add their IPv4 address and ports

      to the list. Closes ticket 32822.

    - Make authorities add their IPv6 ORPort (if any) to the trusted

      servers list. Authorities previously added only their IPv4

      addresses. Closes ticket 32822.

  o Minor features (ed25519, relay):

    - Save a relay's base64-encoded ed25519 identity key to the data

      connections in the heartbeat message. Closes ticket 29113.

  o Minor features (IPv6, ExcludeNodes):

    - Make routerset_contains_router() capable of handling IPv6

      addresses. This makes ExcludeNodes capable of excluding an IPv6

      adddress. Previously, ExcludeNodes ignored IPv6 addresses. Closes

      ticket 34065. Patch by Neel Chauhan.

    - Handle IPv6 addresses in ExcludeNodes; previously they were

      ignored. Closes ticket 34065. Patch by Neel Chauhan.

  o Minor features (logging):

    - Adds the running glibc version to the log. Also adds the running

      and compiled glibc version to the library list returned when using

      the flag --library-versions. Patch from Daniel Pinto. Closes

      ticket 40047; bugfix on 0.4.5.0-alpha-dev.

    - Consider an HTTP 301 response as an error (like a 404) when

      processing the response to a request for a group of server

      descriptors or an extrainfo documents. Closes ticket 40053.

    - Print directory fetch information a single line. Closes

      ticket 40159.

    - Add the running glibc version to the log, and the compiled glibc

      version to the library list returned when using --library-versions.

      Patch from Daniel Pinto. Closes ticket 40047.

    - Consider an HTTP 301 response to be an error (like a 404) when

      processing a directory response. Closes ticket 40053.

    - Log directory fetch statistics a single line. Closes ticket 40159.

    - Provide more complete descriptions of our connections when logging

      about them. Closes ticket 40041.

    - When describing a relay in the logs, we now include its ed25519

      identity. Closes ticket 22668.

  o Minor features (onion services):

    - When writing an onion service hostname file, first read it to make

      sure it contains what we want before attempting to write it. Now

      onion services can set their existing onion service directories to

      read-only and Tor will still work. Resolves ticket 40062. Patch by

      Neel Chauhan.

    - Only overwrite an onion service's existing hostname file if its

      contents are wrong. This enables read-only onion-service

      directories. Resolves ticket 40062. Patch by Neel Chauhan.

  o Minor features (pluggable transports):

    - Added option OutboundBindAddressPT to torrc. This option allows

      users to specify which IPv4 and IPv6 address they want pluggable

      transports to use for outgoing IP packets. Tor does not have a way

      to enforce that the pluggable transport honors this option so each

      pluggable transport will have to implement support for this

      feature. Closes ticket 5304.

  o Minor features (protocol simplification):

    - Tor no longer allows subprotocol versions larger than 63.

      Previously versions up to UINT32_MAX were allowed, which

      significantly complicated our code. Implements proposal 318;

      closes ticket 40133.

    - Add an OutboundBindAddressPT option to allow users to specify

      which IPv4 and IPv6 address pluggable transports should use for

      outgoing IP packets. Tor does not have a way to enforce that the

      pluggable transport honors this option, so each pluggable transport

      needs to implement support on its own. Closes ticket 5304.

  o Minor features (relay address tracking):

    - We store relay addresses for OR connections in a more logical way.

      Previously we would sometimes overwrite the actual address of a

      connection with a "canonical address", and then store the "real

    - We now store relay addresses for OR connections in a more logical

      way. Previously we would sometimes overwrite the actual address of

      a connection with a "canonical address", and then store the "real

      address" elsewhere to remember it. We now track the "canonical

      address" elsewhere for the cases where we need it, and leave the

      connection's address alone. Closes ticket 33898.

      Closes ticket 34137.

  o Minor features (relay, address discovery):

    - If Address is not found in torrc, attempt to learn our address

      with the configured ORPort address if any. Closes ticket 33236.

    - If Address option is not found in torrc, attempt to learn our

      address with the configured ORPort address if any. Closes

      ticket 33236.

  o Minor features (relay, IPv6):

    - Add an AssumeReachableIPv6 option to disable self-checking IPv6

      reachability. Closes part of ticket 33224.

    - Add new "assume-reachable" and "assume-reachable-ipv6" parameters

      to be used in an emergency to tell relays that they should publish

      even if they cannot complete their ORPort self-checks. Closes

      ticket 34064 and part of 33224.

    - Add new "assume-reachable" and "assume-reachable-ipv6" consensus

      parameters to be used in an emergency to tell relays that they

      should publish even if they cannot complete their ORPort self-

      checks. Closes ticket 34064 and part of 33224.

    - Allow relays to send IPv6-only extend cells. Closes ticket 33222.

    - Declare support for the Relay=3 subprotocol version. Closes

      ticket 33226.

    - When loading the state file, remove entries from the statefile

      that have been obsolete for a long time. Ordinarily Tor preserves

      unrecognized entries in order to keep forward-compatibility, but

      these statefile entries have not actually been used in any release

      since before the 0.3.5.x. Closes ticket 40137.

      these entries have not actually been used in any release since

      before the 0.3.5.x. Closes ticket 40137.

  o Minor features (statistics, ipv6):

    - Relays now publish IPv6-specific counts of single-direction versus

      if statistics are enabled. Closes ticket 33263.

  o Minor features (subprotocol versions):

    - Tor no longer allows subprotocol versions larger than 63.

      Previously version numbers up to UINT32_MAX were allowed, which

      significantly complicated our code. Implements proposal 318;

      closes ticket 40133.

    - Use the new limitations on subprotocol versions due to proposal

      318 to simplify our implementation. Part of ticket 40133.

  o Minor features (testing configuration):

    - The TestingTorNetwork no longer implicitly sets AssumeReachable to

      1. This change will allow us to test relays' self-testing

      mechanisms, and eventually to test authorities' relay-testing

    - The TestingTorNetwork option no longer implicitly sets

      AssumeReachable to 1. This change allows us to test relays' self-

      testing mechanisms, and to test authorities' relay-testing

      functionality. Closes ticket 34446.

  o Minor features (testing):

    - Added unit tests for channel_matches_target_addr_for_extend().

      Closes Ticket 33919. Patch by MrSquanchee.

  o Minor bugfixes (security):

    - When completing a channel, relays now check more thoroughly to

      make sure that it matches any pending circuits before attaching

      those circuits. Previously, address correctness and Ed25519

      identities were not checked in this case, but only when extending

      circuits on an existing channel. Fixes bug 40080; bugfix

      on 0.2.7.2-alpha.

  o Minor features (tests, v2 onion services):

    - Fix a rendezvous cache unit test that was triggering an underflow

      on the global rend cache allocation. Fixes bug 40125; bugfix

      on 0.2.8.1-alpha.

    - Fix another rendezvous cache unit test that was triggering an

      underflow on the global rend cache allocation. Fixes bug 40126;

      bugfix on 0.2.8.1-alpha.

  o Minor bugfixes (circuit padding):

    - When circpad_send_padding_cell_for_callback is called,

    - Add a per-circuit padding machine instance counter, so we can

      differentiate between shutdown requests for old machines on a

      circuit; Fixes bug 30992; bugfix on 0.4.1.1-alpha.

    - Add the abilility to keep circuit padding machines if they match a

    - Add the ability to keep circuit padding machines if they match a

      set of circuit state or purposes. This allows us to have machines

      that start up under some conditions but don't shut down under

      others. We now use this mask to avoid starting up introduction

      2.19. Fixes bug 40141; bugfix on 0.4.5.0-alpha-dev. Patch by

      Daniel Pinto.

  o Minor bugfixes (control port):

    - Make sure we send the SOCKS request address in relay begin cells

      when a stream is attached with the purpose

      CIRCUIT_PURPOSE_CONTROLLER. Fixes bug 33124; bugfix on 0.0.5.

      Patch by Neel Chauhan.

  o Minor bugfixes (logging):

    - Remove a debug logging statement that uselessly spam the logs.

      Fixes bug 40135; bugfix on 0.3.5.0-alpha.

      messages started to occur. Fixes bug 19431; bugfix

      on 0.2.2.16-alpha.

  o Minor bugfixes (protover):

    - Consistently reject extra commas, instead of only rejecting

      leading commas. Fixes bug 27194; bugfix on 0.2.9.4-alpha.

  o Minor bugfixes (relay configuration, crash):

    - Avoid a fatal assert() when failing to create a listener

      connection for an address that was in use. Fixes bug 40073; bugfix

  o Minor bugfixes (rust, protocol versions):

    - Declare support for the onion service introduction point denial of

      service extensions, when building tor with Rust. Fixes bug 34248;

      service extensions when building with Rust. Fixes bug 34248;

      bugfix on 0.4.2.1-alpha.

    - Make Rust protocol version support checks consistent with the

      undocumented error behaviour of the corresponding C code. Fixes

      bug 34251; bugfix on 0.3.3.5-rc.

      undocumented error behavior of the corresponding C code. Fixes bug

      34251; bugfix on 0.3.3.5-rc.

  o Minor bugfixes (self-testing):

    - When receiving an incoming circuit, only accept it as evidence

      evidence that we're reachable on some other address. Fixes bug

      20165; bugfix on 0.1.0.1-rc.

  o Minor bugfixes (SOCKS, onion services):

    - Make sure we send the SOCKS request address in relay begin cells

      when a stream is attached with the purpose

      CIRCUIT_PURPOSE_CONTROLLER. Fixes bug 33124; bugfix on 0.0.5.

      Patch by Neel Chauhan.

  o Minor bugfixes (spec conformance):

    - Use the correct key type when generating signing->link

      certificates. Fixes bug 40124; bugfix on 0.2.7.2-alpha.

  o Minor bugfixes (string handling):

  o Minor bugfixes (subprotocol versions):

    - Consistently reject extra commas, instead of only rejecting

      leading commas. Fixes bug 27194; bugfix on 0.2.9.4-alpha.

    - In summarize_protover_flags(), treat empty strings the same as

      NULL. This prevents protocols_known from being set. Previously, we

      treated empty strings as normal strings, which led to

  o Minor bugfixes (v2 onion services):

    - For HSFETCH commands on v2 onion services addresses, check the

      length of bytes decoded, not the base32 length. This takes the

      behavior introduced in commit

      a517daa56f5848d25ba79617a1a7b82ed2b0a7c0 into consideration. Fixes

      bug 34400; bugfix on 0.4.1.1-alpha. Patch by Neel Chauhan.

      length of bytes decoded, not the base32 length. Fixes bug 34400;

      bugfix on 0.4.1.1-alpha. Patch by Neel Chauhan.

  o Code simplification and refactoring:

    - Add and use a set of functions to perform downcasts on constant

    - Add and use a set of functions to perform down-casts on constant

      connection and channel pointers. Closes ticket 40046.

    - Refactor our code that logs a descriptions of connections,

      channels, and the peers on them, to use a single call path. This

      so we can properly integrate IPv6 along IPv4 with common

      interfaces. Closes ticket 40043.

  o Documentation (manpages):

    - Move them from doc/ to doc/man/. Closes ticket 40044.

  o Documentation (manual page):

    - Move them from doc/ to doc/man/. Closes ticket 40044.

    - Describe the status of the "Sandbox" option more accurately. It is

      no longer "experimental", but it _is_ dependent on kernel and libc

      versions. Closes ticket 23378.

    - Document in depth the circuit subsystem trace events in the new

      doc/tracing/EventsCircuit.md. Closes ticket 40036.

  o Testing (CI):

    - Build tracing configure option into our CI. Closes ticket 40038.

  o Testing (onion service v2):

    - Fix a rendezvous cache unit test that was triggering an underflow

      on the global rend cache allocation. Fixes bug 40125; bugfix

      on 0.2.8.1-alpha.

    - Fix another rendezvous cache unit test that was triggering an

      underflow on the global rend cache allocation. Fixes bug 40126;

      bugfix on 0.2.8.1-alpha.

Changes in version 0.4.4.5 - 2020-09-15

  Tor 0.4.4.5 is the first stable release in the 0.4.4.x series. This