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Re: [tor-bugs] #13696 [Tor]: Use syscall-based entropy reading where possible.



#13696: Use syscall-based entropy reading where possible.
-------------------------+--------------------------------
 Reporter:  nickm        |          Owner:  yawning
     Type:  enhancement  |         Status:  needs_revision
 Priority:  Medium       |      Milestone:  Tor: 0.2.???
Component:  Tor          |        Version:
 Severity:  Normal       |     Resolution:
 Keywords:  tor-relay    |  Actual Points:
Parent ID:               |         Points:
  Sponsor:               |
-------------------------+--------------------------------

Comment (by teor):

 Replying to [comment:13 teor]:
 > * /dev/random
 >   * sandboxed on iOS
 >     * source: https://www.mikeash.com/pyblog/friday-qa-2011-03-18
 -random-numbers.html#comment-3e4213b49fef1f45568897721e7ad921
 >     * I wonder what tor / OpenSSL does on iOS at the moment - does it
 have very poor randomness because reading /dev/random fails?

 Apparently this source is wrong, at least for modern iOS versions: iOS
 apps can read from /dev/random. (Which makes sense, as it's impossible to
 seed a CSRNG from /dev/random unless you can read from /dev/random. Unless
 there was some weird xpc / syscall trickery to a privileged process or the
 kernel.)

 I'm still ok with implementing the call to SecRandomCopyBytes on OS X /
 iOS, because it has better semantics (lower failure rate).

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13696#comment:14>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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