[tor-relays] BWAUTH weightings too volatile. . ."twitchy"

teor teor2345 at gmail.com
Sat Jun 6 18:12:18 UTC 2015


> Date: Sat, 06 Jun 2015 02:43:09 -0400
> From: starlight.2015q2 at binnacle.cx
> 
>> One reason this vexes is that I
> would like to see how well the relay
> runs with Address Sanitizer active.
> ASAN provides obvious benefits
> w/r/t security, but entails a
> performance trade-off.  With the
> BWauths throwing darts, eyes closed,
> when choosing weighting, it's
> impossible to gauge the performance
> impact of various adjustments.
>
Good timing!

Tor 0.2.7.1-alpha on x86_64 is currently Address Sanitizer and Undefined Behavior Sanitizer clean. I've just submitted a branch with instructions for building, running, and testing Tor with ASAN and UBSAN.
https://trac.torproject.org/projects/tor/ticket/15817#comment:8

The following known issues exist:

Two of the tests deliberately invoke undefined / illegal behavior, the instructions provide a blacklist file and an environmental variable to exempt them from ASAN/UBSAN.

Architectures without (x86?) 64-bit assembler use donna C code that left-shifts 1 bits into and past the sign bit of signed integers.
Until https://trac.torproject.org/projects/tor/ticket/13538
is resolved, this particular file can be exempted from UBSAN.

Please let me know how you go - the 0.2.6.x series should also be relatively ASAN and UBSAN clean, as Tor has been tested with them since late 2014.

teor

teor2345 at gmail dot com
pgp 0xABFED1AC
https://gist.github.com/teor2345/d033b8ce0a99adbc89c5

teor at blah dot im
OTR D5BE4EC2 255D7585 F3874930 DB130265 7C9EBBC7

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