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[tor-announce] [Security] New Tor releases today: 0.2.9.15, 0.3.1.10, 0.3.2.10, 0.3.3.3-alpha
Hello! I am sending this email a little early (before the website has
had a chance to update) because today's releases are security
relevant.
If you build Tor from source, the source code is available at
https://dist.torproject.org/ . Packages should be available over the
coming days.
Before I post the changelogs below, I'll give an overview of the
security issues and the more important security fixes.
In brief:
* Directory authorities should upgrade.
* Relays running 0.3.2.1-alpha through 0.3.2.9 should upgrade.
* Relays running 0.3.3.1-alpha should upgrade.
* All other relays may wish to upgrade in order to improve their
resistance to denial-of-service attacks.
TROVE-2018-001 only affects directory authorities. It is a bug that
an attacker can use to cause a remote directory authority to crash.
All directory authorities should upgrade to one of the versions
released today. It does not affect relays or clients.
TROVE-2018-002 affects relays running all 0.3.2.x, versions, as well
as 0.3.3.1-alpha. (Because we have found that it can be remotely
triggered, we are backporting it and upgrading its severity.) It is a
use-after-free bug in the KIST scheduler code, which an attacker can
use to cause a relay to crash. Use-after-free bugs can sometimes be
turned into worse attacks: we strongly recommend that all relays
running 0.3.2.x (or 0.3.3.1-alpha) should upgrade to one of the
versions released today. This issue does not affect other versions,
and does not affect clients.
TROVE-2018-003 and TROVE-2018-004 are low-severity; see the changelogs
for more information.
These releases also backport our denial-of-service mitigation code,
tracked with ticket #24902. If you are running a relay, you might
want to backport in order to get those fixes, especially if your relay
is overloaded.
Here are the changes in today's releases:
Changes in version 0.3.3.3-alpha - 2018-03-03
Tor 0.3.3.3-alpha is the third alpha release for the 0.3.3.x series.
It includes an important security fix for a remote crash attack
against directory authorities tracked as TROVE-2018-001.
Additionally, with this release, we are upgrading the severity of a
bug fixed in 0.3.3.2-alpha. Bug 24700, which was fixed in
0.3.3.2-alpha, can be remotely triggered in order to crash relays with
a use-after-free pattern. As such, we are now tracking that bug as
TROVE-2018-002 and CVE-2018-0491. This bug affected versions
0.3.2.1-alpha through 0.3.2.9, as well as 0.3.3.1-alpha.
This release also fixes several minor bugs and annoyances from
earlier releases.
Relays running 0.3.2.x should upgrade to one of the versions released
today, for the fix to TROVE-2018-002. Directory authorities should
also upgrade. (Relays on earlier versions might want to update too for
the DoS mitigations.)
o Major bugfixes (denial-of-service, directory authority):
- Fix a protocol-list handling bug that could be used to remotely crash
directory authorities with a null-pointer exception. Fixes bug 25074;
bugfix on 0.2.9.4-alpha. Also tracked as TROVE-2018-001 and
CVE-2018-0490.
o Minor features (compatibility, OpenSSL):
- Tor will now support TLS1.3 once OpenSSL 1.1.1 is released.
Previous versions of Tor would not have worked with OpenSSL 1.1.1,
since they neither disabled TLS 1.3 nor enabled any of the
ciphersuites it requires. Now we enable the TLS 1.3 ciphersuites.
Closes ticket 24978.
o Minor features (logging):
- Clarify the log messages produced when getrandom() or a related
entropy-generation mechanism gives an error. Closes ticket 25120.
o Minor features (testing):
- Add a "make test-rust" target to run the rust tests only. Closes
ticket 25071.
o Minor bugfixes (denial-of-service):
- Fix a possible crash on malformed consensus. If a consensus had
contained an unparseable protocol line, it could have made clients
and relays crash with a null-pointer exception. To exploit this
issue, however, an attacker would need to be able to subvert the
directory authority system. Fixes bug 25251; bugfix on
0.2.9.4-alpha. Also tracked as TROVE-2018-004.
o Minor bugfixes (DoS mitigation):
- Add extra safety checks when refilling the circuit creation bucket
to ensure we never set a value above the allowed maximum burst.
Fixes bug 25202; bugfix on 0.3.3.2-alpha.
- When a new consensus arrives, don't update our DoS-mitigation
parameters if we aren't a public relay. Fixes bug 25223; bugfix
on 0.3.3.2-alpha.
o Minor bugfixes (man page, SocksPort):
- Remove dead code from the old "SocksSocket" option, and rename
SocksSocketsGroupWritable to UnixSocksGroupWritable. The old option
still works, but is deprecated. Fixes bug 24343; bugfix on 0.2.6.3.
o Minor bugfixes (performance):
- Reduce the number of circuits that will be opened at once during
the circuit build timeout phase. This is done by increasing the
idle timeout to 3 minutes, and lowering the maximum number of
concurrent learning circuits to 10. Fixes bug 24769; bugfix
on 0.3.1.1-alpha.
o Minor bugfixes (spec conformance):
- Forbid "-0" as a protocol version. Fixes part of bug 25249; bugfix on
0.2.9.4-alpha.
- Forbid UINT32_MAX as a protocol version. Fixes part of bug 25249;
bugfix on 0.2.9.4-alpha.
o Minor bugfixes (spec conformance, rust):
- Resolve a denial-of-service issue caused by an infinite loop in
the rust protover code. Fixes bug 25250, bugfix on 0.3.3.1-alpha.
Also tracked as TROVE-2018-003.
o Code simplification and refactoring:
- Update the "rust dependencies" submodule to be a project-level
repository, rather than a user repository. Closes ticket 25323.
Changes in version 0.3.2.10 - 2018-03-03
Tor 0.3.2.10 is the second stable release in the 0.3.2 series. It
backports a number of bugfixes, including important fixes for security
issues.
It includes an important security fix for a remote crash attack
against directory authorities, tracked as TROVE-2018-001.
Additionally, it backports a fix for a bug whose severity we have
upgraded: Bug 24700, which was fixed in 0.3.3.2-alpha, can be remotely
triggered in order to crash relays with a use-after-free pattern. As
such, we are now tracking that bug as TROVE-2018-002 and
CVE-2018-0491, and backporting it to earlier releases. This bug
affected versions 0.3.2.1-alpha through 0.3.2.9, as well as version
0.3.3.1-alpha.
This release also backports our new system for improved resistance to
denial-of-service attacks against relays.
This release also fixes several minor bugs and annoyances from
earlier releases.
Relays running 0.3.2.x SHOULD upgrade to one of the versions released
today, for the fix to TROVE-2018-002. Directory authorities should
also upgrade. (Relays on earlier versions might want to update too for
the DoS mitigations.)
o Major bugfixes (denial-of-service, directory authority, backport
from 0.3.3.3-alpha):
- Fix a protocol-list handling bug that could be used to remotely crash
directory authorities with a null-pointer exception. Fixes bug 25074;
bugfix on 0.2.9.4-alpha. Also tracked as TROVE-2018-001 and
CVE-2018-0490.
o Major bugfixes (scheduler, KIST, denial-of-service, backport from
0.3.3.2-alpha):
- Avoid adding the same channel twice in the KIST scheduler pending
list, which could lead to remote denial-of-service use-after-free
attacks against relays. Fixes bug 24700; bugfix on 0.3.2.1-alpha.
o Major features (denial-of-service mitigation, backport from 0.3.3.2-alpha):
- Give relays some defenses against the recent network overload. We
start with three defenses (default parameters in parentheses).
First: if a single client address makes too many concurrent
connections (>100), hang up on further connections. Second: if a
single client address makes circuits too quickly (more than 3 per
second, with an allowed burst of 90) while also having too many
connections open (3), refuse new create cells for the next while
(1-2 hours). Third: if a client asks to establish a rendezvous
point to you directly, ignore the request. These defenses can be
manually controlled by new torrc options, but relays will also
take guidance from consensus parameters, so there's no need to
configure anything manually. Implements ticket 24902.
o Major bugfixes (onion services, retry behavior, backport from
0.3.3.1-alpha):
- Fix an "off by 2" error in counting rendezvous failures on the
onion service side. While we thought we would stop the rendezvous
attempt after one failed circuit, we were actually making three
circuit attempts before giving up. Now switch to a default of 2,
and allow the consensus parameter "hs_service_max_rdv_failures" to
override. Fixes bug 24895; bugfix on 0.0.6.
- New-style (v3) onion services now obey the "max rendezvous circuit
attempts" logic. Previously they would make as many rendezvous
circuit attempts as they could fit in the MAX_REND_TIMEOUT second
window before giving up. Fixes bug 24894; bugfix on 0.3.2.1-alpha.
o Major bugfixes (protocol versions, backport from 0.3.3.2-alpha):
- Add Link protocol version 5 to the supported protocols list. Fixes
bug 25070; bugfix on 0.3.1.1-alpha.
o Major bugfixes (relay, backport from 0.3.3.1-alpha):
- Fix a set of false positives where relays would consider
connections to other relays as being client-only connections (and
thus e.g. deserving different link padding schemes) if those
relays fell out of the consensus briefly. Now we look only at the
initial handshake and whether the connection authenticated as a
relay. Fixes bug 24898; bugfix on 0.3.1.1-alpha.
o Major bugfixes (scheduler, consensus, backport from 0.3.3.2-alpha):
- The scheduler subsystem was failing to promptly notice changes in
consensus parameters, making it harder to switch schedulers
network-wide. Fixes bug 24975; bugfix on 0.3.2.1-alpha.
o Minor features (denial-of-service avoidance, backport from 0.3.3.2-alpha):
- Make our OOM handler aware of the geoip client history cache so it
doesn't fill up the memory. This check is important for IPv6 and
our DoS mitigation subsystem. Closes ticket 25122.
o Minor features (compatibility, OpenSSL, backport from 0.3.3.3-alpha):
- Tor will now support TLS1.3 once OpenSSL 1.1.1 is released.
Previous versions of Tor would not have worked with OpenSSL 1.1.1,
since they neither disabled TLS 1.3 nor enabled any of the
ciphersuites it requires. Now we enable the TLS 1.3 ciphersuites.
Closes ticket 24978.
o Minor features (geoip):
- Update geoip and geoip6 to the February 7 2018 Maxmind GeoLite2
Country database.
o Minor features (logging, diagnostic, backport from 0.3.3.2-alpha):
- When logging a failure to check a hidden service's certificate,
also log what the problem with the certificate was. Diagnostic
for ticket 24972.
o Minor bugfix (channel connection, backport from 0.3.3.2-alpha):
- Use the actual observed address of an incoming relay connection,
not the canonical address of the relay from its descriptor, when
making decisions about how to handle the incoming connection.
Fixes bug 24952; bugfix on 0.2.4.11-alpha. Patch by "ffmancera".
o Minor bugfixes (denial-of-service, backport from 0.3.3.3-alpha):
- Fix a possible crash on malformed consensus. If a consensus had
contained an unparseable protocol line, it could have made clients
and relays crash with a null-pointer exception. To exploit this
issue, however, an attacker would need to be able to subvert the
directory authority system. Fixes bug 25251; bugfix on
0.2.9.4-alpha. Also tracked as TROVE-2018-004.
o Minor bugfix (directory authority, backport from 0.3.3.2-alpha):
- Directory authorities, when refusing a descriptor from a rejected
relay, now explicitly tell the relay (in its logs) to set a valid
ContactInfo address and contact the bad-relays@ mailing list.
Fixes bug 25170; bugfix on 0.2.9.1.
o Minor bugfixes (build, rust, backport from 0.3.3.1-alpha):
- When building with Rust on OSX, link against libresolv, to work
around the issue at https://github.com/rust-lang/rust/issues/46797.
Fixes bug 24652; bugfix on 0.3.1.1-alpha.
o Minor bugfixes (onion services, backport from 0.3.3.2-alpha):
- Remove a BUG() statement when a client fetches an onion descriptor
that has a lower revision counter than the one in its cache. This
can happen in normal circumstances due to HSDir desync. Fixes bug
24976; bugfix on 0.3.2.1-alpha.
o Minor bugfixes (logging, backport from 0.3.3.2-alpha):
- Don't treat inability to store a cached consensus object as a bug:
it can happen normally when we are out of disk space. Fixes bug
24859; bugfix on 0.3.1.1-alpha.
o Minor bugfixes (performance, fragile-hardening, backport from
0.3.3.1-alpha):
- Improve the performance of our consensus-diff application code
when Tor is built with the --enable-fragile-hardening option set.
Fixes bug 24826; bugfix on 0.3.1.1-alpha.
o Minor bugfixes (OSX, backport from 0.3.3.1-alpha):
- Don't exit the Tor process if setrlimit() fails to change the file
limit (which can happen sometimes on some versions of OSX). Fixes
bug 21074; bugfix on 0.0.9pre5.
o Minor bugfixes (spec conformance, backport from 0.3.3.3-alpha):
- Forbid "-0" as a protocol version. Fixes part of bug 25249; bugfix on
0.2.9.4-alpha.
- Forbid UINT32_MAX as a protocol version. Fixes part of bug 25249;
bugfix on 0.2.9.4-alpha.
o Minor bugfixes (testing, backport from 0.3.3.1-alpha):
- Fix a memory leak in the scheduler/loop_kist unit test. Fixes bug
25005; bugfix on 0.3.2.7-rc.
o Minor bugfixes (v3 onion services, backport from 0.3.3.2-alpha):
- Look at the "HSRend" protocol version, not the "HSDir" protocol
version, when deciding whether a consensus entry can support the
v3 onion service protocol as a rendezvous point. Fixes bug 25105;
bugfix on 0.3.2.1-alpha.
o Code simplification and refactoring (backport from 0.3.3.3-alpha):
- Update the "rust dependencies" submodule to be a project-level
repository, rather than a user repository. Closes ticket 25323.
o Documentation (backport from 0.3.3.1-alpha)
- Document that operators who run more than one relay or bridge are
expected to set MyFamily and ContactInfo correctly. Closes
ticket 24526.
Changes in version 0.3.1.10 - 2018-03-03
Tor 0.3.1.10 backports a number of bugfixes, including important fixes for
security issues.
It includes an important security fix for a remote crash attack
against directory authorities, tracked as TROVE-2018-001.
This release also backports our new system for improved resistance to
denial-of-service attacks against relays.
This release also fixes several minor bugs and annoyances from
earlier releases.
All directory authorities should upgrade to one of the versions
released today. Relays running 0.3.1.x may wish to update to one of
the versions released today, for the DoS mitigations.
Please note: according to our release calendar, Tor 0.3.1 will no
longer be supported after 1 July 2018. If you will be running Tor
after that date, you should make sure to plan to upgrade to the latest
stable version, or downgrade to 0.2.9 (which will receive long-term
support).
o Major bugfixes (denial-of-service, directory authority, backport
from 0.3.3.3-alpha):
- Fix a protocol-list handling bug that could be used to remotely crash
directory authorities with a null-pointer exception. Fixes bug 25074;
bugfix on 0.2.9.4-alpha. Also tracked as TROVE-2018-001 and
CVE-2018-0490.
o Major features (denial-of-service mitigation, backport from 0.3.3.2-alpha):
- Give relays some defenses against the recent network overload. We
start with three defenses (default parameters in parentheses).
First: if a single client address makes too many concurrent
connections (>100), hang up on further connections. Second: if a
single client address makes circuits too quickly (more than 3 per
second, with an allowed burst of 90) while also having too many
connections open (3), refuse new create cells for the next while
(1-2 hours). Third: if a client asks to establish a rendezvous
point to you directly, ignore the request. These defenses can be
manually controlled by new torrc options, but relays will also
take guidance from consensus parameters, so there's no need to
configure anything manually. Implements ticket 24902.
o Minor features (linux seccomp2 sandbox, backport from 0.3.2.5-alpha):
- Update the sandbox rules so that they should now work correctly
with Glibc 2.26. Closes ticket 24315.
o Major bugfixes (onion services, retry behavior, backport from
0.3.3.1-alpha):
- Fix an "off by 2" error in counting rendezvous failures on the
onion service side. While we thought we would stop the rendezvous
attempt after one failed circuit, we were actually making three
circuit attempts before giving up. Now switch to a default of 2,
and allow the consensus parameter "hs_service_max_rdv_failures" to
override. Fixes bug 24895; bugfix on 0.0.6.
o Major bugfixes (protocol versions, backport from 0.3.3.2-alpha):
- Add Link protocol version 5 to the supported protocols list. Fixes
bug 25070; bugfix on 0.3.1.1-alpha.
o Major bugfixes (relay, backport from 0.3.3.1-alpha):
- Fix a set of false positives where relays would consider
connections to other relays as being client-only connections (and
thus e.g. deserving different link padding schemes) if those
relays fell out of the consensus briefly. Now we look only at the
initial handshake and whether the connection authenticated as a
relay. Fixes bug 24898; bugfix on 0.3.1.1-alpha.
o Minor features (denial-of-service avoidance, backport from 0.3.3.2-alpha):
- Make our OOM handler aware of the geoip client history cache so it
doesn't fill up the memory. This check is important for IPv6 and
our DoS mitigation subsystem. Closes ticket 25122.
o Minor feature (relay statistics, backport from 0.3.2.6-alpha):
- Change relay bandwidth reporting stats interval from 4 hours to 24
hours in order to reduce the efficiency of guard discovery
attacks. Fixes ticket 23856.
o Minor features (compatibility, OpenSSL, backport from 0.3.3.3-alpha):
- Tor will now support TLS1.3 once OpenSSL 1.1.1 is released.
Previous versions of Tor would not have worked with OpenSSL 1.1.1,
since they neither disabled TLS 1.3 nor enabled any of the
ciphersuites it requires. Now we enable the TLS 1.3 ciphersuites.
Closes ticket 24978.
o Minor features (fallback directory mirrors, backport from 0.3.2.9):
- The fallback directory list has been re-generated based on the
current status of the network. Tor uses fallback directories to
bootstrap when it doesn't yet have up-to-date directory
information. Closes ticket 24801.
- Make the default DirAuthorityFallbackRate 0.1, so that clients
prefer to bootstrap from fallback directory mirrors. This is a
follow-up to 24679, which removed weights from the default
fallbacks. Implements ticket 24681.
o Minor features (geoip):
- Update geoip and geoip6 to the February 7 2018 Maxmind GeoLite2
Country database.
o Minor bugfix (channel connection, backport from 0.3.3.2-alpha):
- Use the actual observed address of an incoming relay connection,
not the canonical address of the relay from its descriptor, when
making decisions about how to handle the incoming connection.
Fixes bug 24952; bugfix on 0.2.4.11-alpha. Patch by "ffmancera".
o Minor bugfix (directory authority, backport from 0.3.3.2-alpha):
- Directory authorities, when refusing a descriptor from a rejected
relay, now explicitly tell the relay (in its logs) to set a valid
ContactInfo address and contact the bad-relays@ mailing list.
Fixes bug 25170; bugfix on 0.2.9.1.
o Minor bugfixes (address selection, backport from 0.3.2.9):
- When the fascist_firewall_choose_address_ functions don't find a
reachable address, set the returned address to the null address
and port. This is a precautionary measure, because some callers do
not check the return value. Fixes bug 24736; bugfix
on 0.2.8.2-alpha.
o Major bugfixes (bootstrapping, backport from 0.3.2.5-alpha):
- Fetch descriptors aggressively whenever we lack enough to build
circuits, regardless of how many descriptors we are missing.
Previously, we would delay launching the fetch when we had fewer
than 15 missing descriptors, even if some of those descriptors
were blocking circuits from building. Fixes bug 23985; bugfix on
0.1.1.11-alpha. The effects of this bug became worse in
0.3.0.3-alpha, when we began treating missing descriptors from our
primary guards as a reason to delay circuits.
- Don't try fetching microdescriptors from relays that have failed
to deliver them in the past. Fixes bug 23817; bugfix
on 0.3.0.1-alpha.
o Minor bugfixes (compilation, backport from 0.3.2.7-rc):
- Fix a signed/unsigned comparison warning introduced by our fix to
TROVE-2017-009. Fixes bug 24480; bugfix on 0.2.5.16.
o Minor bugfixes (control port, linux seccomp2 sandbox, backport
from 0.3.2.5-alpha):
- Avoid a crash when attempting to use the seccomp2 sandbox together
with the OwningControllerProcess feature. Fixes bug 24198; bugfix
on 0.2.5.1-alpha.
o Minor bugfixes (denial-of-service, backport from 0.3.3.3-alpha):
- Fix a possible crash on malformed consensus. If a consensus had
contained an unparseable protocol line, it could have made clients
and relays crash with a null-pointer exception. To exploit this
issue, however, an attacker would need to be able to subvert the
directory authority system. Fixes bug 25251; bugfix on
0.2.9.4-alpha. Also tracked as TROVE-2018-004.
o Minor bugfixes (directory cache, backport from 0.3.2.5-alpha):
- Recover better from empty or corrupt files in the consensus cache
directory. Fixes bug 24099; bugfix on 0.3.1.1-alpha.
- When a consensus diff calculation is only partially successful,
only record the successful parts as having succeeded. Partial
success can happen if (for example) one compression method fails
but the others succeed. Previously we misrecorded all the
calculations as having succeeded, which would later cause a
nonfatal assertion failure. Fixes bug 24086; bugfix
on 0.3.1.1-alpha.
o Minor bugfixes (entry guards, backport from 0.3.2.3-alpha):
- Tor now updates its guard state when it reads a consensus
regardless of whether it's missing descriptors. That makes tor use
its primary guards to fetch descriptors in some edge cases where
it would previously have used fallback directories. Fixes bug
23862; bugfix on 0.3.0.1-alpha.
o Minor bugfixes (logging, backport from 0.3.3.2-alpha):
- Don't treat inability to store a cached consensus object as a bug:
it can happen normally when we are out of disk space. Fixes bug
24859; bugfix on 0.3.1.1-alpha.
o Minor bugfixes (memory usage, backport from 0.3.2.8-rc):
- When queuing DESTROY cells on a channel, only queue the circuit-id
and reason fields: not the entire 514-byte cell. This fix should
help mitigate any bugs or attacks that fill up these queues, and
free more RAM for other uses. Fixes bug 24666; bugfix
on 0.2.5.1-alpha.
o Minor bugfixes (network layer, backport from 0.3.2.5-alpha):
- When closing a connection via close_connection_immediately(), we
mark it as "not blocked on bandwidth", to prevent later calls from
trying to unblock it, and give it permission to read. This fixes a
backtrace warning that can happen on relays under various
circumstances. Fixes bug 24167; bugfix on 0.1.0.1-rc.
o Minor bugfixes (path selection, backport from 0.3.2.4-alpha):
- When selecting relays by bandwidth, avoid a rounding error that
could sometimes cause load to be imbalanced incorrectly.
Previously, we would always round upwards; now, we round towards
the nearest integer. This had the biggest effect when a relay's
weight adjustments should have given it weight 0, but it got
weight 1 instead. Fixes bug 23318; bugfix on 0.2.4.3-alpha.
- When calculating the fraction of nodes that have descriptors, and
all nodes in the network have zero bandwidths, count the number of
nodes instead. Fixes bug 23318; bugfix on 0.2.4.10-alpha.
- Actually log the total bandwidth in compute_weighted_bandwidths().
Fixes bug 24170; bugfix on 0.2.4.3-alpha.
o Minor bugfixes (performance, fragile-hardening, backport from
0.3.3.1-alpha):
- Improve the performance of our consensus-diff application code
when Tor is built with the --enable-fragile-hardening option set.
Fixes bug 24826; bugfix on 0.3.1.1-alpha.
o Minor bugfixes (OSX, backport from 0.3.3.1-alpha):
- Don't exit the Tor process if setrlimit() fails to change the file
limit (which can happen sometimes on some versions of OSX). Fixes
bug 21074; bugfix on 0.0.9pre5.
o Minor bugfixes (portability, msvc, backport from 0.3.2.9):
- Fix a bug in the bit-counting parts of our timing-wheel code on
MSVC. (Note that MSVC is still not a supported build platform, due
to cyptographic timing channel risks.) Fixes bug 24633; bugfix
on 0.2.9.1-alpha.
o Minor bugfixes (relay, partial backport):
- Make the internal channel_is_client() function look at what sort
of connection handshake the other side used, rather than whether
the other side ever sent a create_fast cell to us. Backports part
of the fixes from bugs 22805 and 24898.
o Minor bugfixes (spec conformance, backport from 0.3.3.3-alpha):
- Forbid "-0" as a protocol version. Fixes part of bug 25249; bugfix on
0.2.9.4-alpha.
- Forbid UINT32_MAX as a protocol version. Fixes part of bug 25249;
bugfix on 0.2.9.4-alpha.
o Code simplification and refactoring (backport from 0.3.3.3-alpha):
- Update the "rust dependencies" submodule to be a project-level
repository, rather than a user repository. Closes ticket 25323.
Changes in version 0.2.9.15 - 2018-03-03
Tor 0.2.9.15 backports important security and stability bugfixes from
later Tor releases.
It includes an important security fix for a remote crash attack
against directory authorities, tracked as TROVE-2018-001.
This release also backports our new system for improved resistance to
denial-of-service attacks against relays.
This release also fixes several minor bugs and annoyances from
earlier releases.
All directory authorities should upgrade to one of the versions
released today. Relays running 0.2.9.x may wish to update to one of
the versions released today, for the DoS mitigations.
o Major bugfixes (denial-of-service, directory authority, backport
from 0.3.3.3-alpha):
- Fix a protocol-list handling bug that could be used to remotely crash
directory authorities with a null-pointer exception. Fixes bug 25074;
bugfix on 0.2.9.4-alpha. Also tracked as TROVE-2018-001 and
CVE-2018-0490.
o Major features (denial-of-service mitigation):
- Give relays some defenses against the recent network overload. We
start with three defenses (default parameters in parentheses).
First: if a single client address makes too many concurrent
connections (>100), hang up on further connections. Second: if a
single client address makes circuits too quickly (more than 3 per
second, with an allowed burst of 90) while also having too many
connections open (3), refuse new create cells for the next while
(1-2 hours). Third: if a client asks to establish a rendezvous
point to you directly, ignore the request. These defenses can be
manually controlled by new torrc options, but relays will also
take guidance from consensus parameters, so there's no need to
configure anything manually. Implements ticket 24902.
o Major bugfixes (bootstrapping):
- Fetch descriptors aggressively whenever we lack enough to build
circuits, regardless of how many descriptors we are missing.
Previously, we would delay launching the fetch when we had fewer
than 15 missing descriptors, even if some of those descriptors
were blocking circuits from building. Fixes bug 23985; bugfix on
0.1.1.11-alpha. The effects of this bug became worse in
0.3.0.3-alpha, when we began treating missing descriptors from our
primary guards as a reason to delay circuits.
o Major bugfixes (onion services, retry behavior):
- Fix an "off by 2" error in counting rendezvous failures on the
onion service side. While we thought we would stop the rendezvous
attempt after one failed circuit, we were actually making three
circuit attempts before giving up. Now switch to a default of 2,
and allow the consensus parameter "hs_service_max_rdv_failures" to
override. Fixes bug 24895; bugfix on 0.0.6.
o Minor feature (relay statistics):
- Change relay bandwidth reporting stats interval from 4 hours to 24
hours in order to reduce the efficiency of guard discovery
attacks. Fixes ticket 23856.
o Minor features (compatibility, OpenSSL):
- Tor will now support TLS1.3 once OpenSSL 1.1.1 is released.
Previous versions of Tor would not have worked with OpenSSL 1.1.1,
since they neither disabled TLS 1.3 nor enabled any of the
ciphersuites it requires. Now we enable the TLS 1.3 ciphersuites.
Closes ticket 24978.
o Minor features (denial-of-service avoidance):
- Make our OOM handler aware of the geoip client history cache so it
doesn't fill up the memory. This check is important for IPv6 and
our DoS mitigation subsystem. Closes ticket 25122.
o Minor features (fallback directory mirrors):
- The fallback directory list has been re-generated based on the
current status of the network. Tor uses fallback directories to
bootstrap when it doesn't yet have up-to-date directory
information. Closes ticket 24801.
- Make the default DirAuthorityFallbackRate 0.1, so that clients
prefer to bootstrap from fallback directory mirrors. This is a
follow-up to 24679, which removed weights from the default
fallbacks. Implements ticket 24681.
o Minor features (geoip):
- Update geoip and geoip6 to the February 7 2018 Maxmind GeoLite2
Country database.
o Minor features (linux seccomp2 sandbox):
- Update the sandbox rules so that they should now work correctly
with Glibc 2.26. Closes ticket 24315.
o Minor bugfix (channel connection):
- Use the actual observed address of an incoming relay connection,
not the canonical address of the relay from its descriptor, when
making decisions about how to handle the incoming connection.
Fixes bug 24952; bugfix on 0.2.4.11-alpha. Patch by "ffmancera".
o Minor bugfix (directory authority):
- Directory authorities, when refusing a descriptor from a rejected
relay, now explicitly tell the relay (in its logs) to set a valid
ContactInfo address and contact the bad-relays@ mailing list.
Fixes bug 25170; bugfix on 0.2.9.1.
o Minor bugfixes (address selection):
- When the fascist_firewall_choose_address_ functions don't find a
reachable address, set the returned address to the null address
and port. This is a precautionary measure, because some callers do
not check the return value. Fixes bug 24736; bugfix
on 0.2.8.2-alpha.
o Minor bugfixes (compilation):
- Fix a signed/unsigned comparison warning introduced by our fix to
TROVE-2017-009. Fixes bug 24480; bugfix on 0.2.5.16.
o Minor bugfixes (control port, linux seccomp2 sandbox):
- Avoid a crash when attempting to use the seccomp2 sandbox together
with the OwningControllerProcess feature. Fixes bug 24198; bugfix
on 0.2.5.1-alpha.
o Minor bugfixes (denial-of-service, backport from 0.3.3.3-alpha):
- Fix a possible crash on malformed consensus. If a consensus had
contained an unparseable protocol line, it could have made clients
and relays crash with a null-pointer exception. To exploit this
issue, however, an attacker would need to be able to subvert the
directory authority system. Fixes bug 25251; bugfix on
0.2.9.4-alpha. Also tracked as TROVE-2018-004.
o Minor bugfixes (memory usage):
- When queuing DESTROY cells on a channel, only queue the circuit-id
and reason fields: not the entire 514-byte cell. This fix should
help mitigate any bugs or attacks that fill up these queues, and
free more RAM for other uses. Fixes bug 24666; bugfix
on 0.2.5.1-alpha.
o Minor bugfixes (network layer):
- When closing a connection via close_connection_immediately(), we
mark it as "not blocked on bandwidth", to prevent later calls from
trying to unblock it, and give it permission to read. This fixes a
backtrace warning that can happen on relays under various
circumstances. Fixes bug 24167; bugfix on 0.1.0.1-rc.
o Minor bugfixes (OSX):
- Don't exit the Tor process if setrlimit() fails to change the file
limit (which can happen sometimes on some versions of OSX). Fixes
bug 21074; bugfix on 0.0.9pre5.
o Minor bugfixes (path selection):
- When selecting relays by bandwidth, avoid a rounding error that
could sometimes cause load to be imbalanced incorrectly.
Previously, we would always round upwards; now, we round towards
the nearest integer. This had the biggest effect when a relay's
weight adjustments should have given it weight 0, but it got
weight 1 instead. Fixes bug 23318; bugfix on 0.2.4.3-alpha.
- When calculating the fraction of nodes that have descriptors, and
all nodes in the network have zero bandwidths, count the number of
nodes instead. Fixes bug 23318; bugfix on 0.2.4.10-alpha.
- Actually log the total bandwidth in compute_weighted_bandwidths().
Fixes bug 24170; bugfix on 0.2.4.3-alpha.
o Minor bugfixes (portability, msvc):
- Fix a bug in the bit-counting parts of our timing-wheel code on
MSVC. (Note that MSVC is still not a supported build platform, due
to cryptographic timing channel risks.) Fixes bug 24633; bugfix
on 0.2.9.1-alpha.
o Minor bugfixes (relay):
- Make the internal channel_is_client() function look at what sort
of connection handshake the other side used, rather than whether
the other side ever sent a create_fast cell to us. Backports part
of the fixes from bugs 22805 and 24898.
o Minor bugfixes (spec conformance, backport from 0.3.3.3-alpha):
- Forbid "-0" as a protocol version. Fixes part of bug 25249; bugfix on
0.2.9.4-alpha.
- Forbid UINT32_MAX as a protocol version. Fixes part of bug 25249;
bugfix on 0.2.9.4-alpha.
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