[tor-bugs] #23061 [Core Tor/Tor]: crypto_rand_double() should produce all possible outputs on 32-bit platforms

[Tor Bug Tracker & Wiki]

#23061: crypto_rand_double() should produce all possible outputs on 32-bit
platforms
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.2.x-final
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.2.2.14-alpha
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-relay, security-low, privcount,  |  Actual Points:  0.5
  031-backport, 030-backport, 029-backport, 028  |
  -backport-maybe, 027-backport-maybe, 026       |
  -backport-maybe                                |
Parent ID:                                       |         Points:  0.1
 Reviewer:                                       |        Sponsor:
                                                 |  SponsorQ
-------------------------------------------------+-------------------------
Changes (by teor):

 * status:  new => needs_review
 * keywords:  tor-relay, security-low, privcount =>
     tor-relay, security-low, privcount, 031-backport, 030-backport,
     029-backport, 028-backport-maybe, 027-backport-maybe, 026-backport-
     maybe
 * actualpoints:   => 0.5


Comment:

 See my branch rand-double-029, which is based on maint-0.2.9. It comes
 with unit tests and a rewritten crypto_rand_double() that uses rejection
 sampling. The new unit tests pass for me on macOS 10.12 x86_64 and i386.

 We might want to backport this to 0.2.6, where we added laplace noise
 using this function. But when I tried to cherry-pick the commits, it was
 non-trivial. (Someone else is welcome to do this!)

 The only users of crypto_rand_double() before 0.2.6 are tests, so we don't
 need to backport it any further.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23061#comment:3>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online