Tor 0.2.9.1-alpha is the first alpha release in the 0.2.9 development series. It improves our support for hardened builds and compiler warnings, deploys some critical infrastructure for improvements to hidden services, includes a new timing backend that we hope to use for better support for traffic padding, makes it easier for programmers to log unexpected events, and contains other small improvements to security, correctness, and performance.

You can download the source from the usual place on the website.

Packages should be available over the next several days. Remember

to check the signatures!

Please note: This is an alpha release. You should only try this one if

you are interested in tracking Tor development, testing new features,

making sure that Tor still builds on unusual platforms, or generally

trying to hunt down bugs. If you want a stable experience, please stick to the stable releases.

Below are the changes since 0.2.8.6.

Changes in version 0.2.9.1-alpha - 2016-08-08

New system requirements: Tor now requires Libevent version 2.0.10-stable or later. Older versions of Libevent have less efficient backends for several platforms, and lack the DNS code that we use for our server-side DNS support. This implements ticket 19554. Tor now requires zlib version 1.2 or later, for security, efficiency, and (eventually) gzip support. (Back when we started, zlib 1.1 and zlib 1.0 were still found in the wild. 1.2 was released in 2003. We recommend the latest version.)

Major features (build, hardening): Tor now builds with -ftrapv by default on compilers that support it. This option detects signed integer overflow (which C forbids), and turns it into a hard-failure. We do not apply this option to code that needs to run in constant time to avoid side-channels; instead, we use -fwrapv in that code. Closes ticket 17983. When --enable-expensive-hardening is selected, stop applying the clang/gcc sanitizers to code that needs to run in constant time. Although we are aware of no introduced side-channels, we are not able to prove that there are none. Related to ticket 17983.

