[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: [tor-bugs] #21010 [Applications/Tor Browser Sandbox]: Disable RDTSC/RDTSCP to limit side-channel attacks

#21010: Disable RDTSC/RDTSCP to limit side-channel attacks
----------------------------------------------+-------------------------
 Reporter:  cypherpunks                       |          Owner:  yawning
     Type:  enhancement                       |         Status:  new
 Priority:  High                              |      Milestone:
Component:  Applications/Tor Browser Sandbox  |        Version:
 Severity:  Normal                            |     Resolution:
 Keywords:                                    |  Actual Points:
Parent ID:                                    |         Points:
 Reviewer:                                    |        Sponsor:
----------------------------------------------+-------------------------

Comment (by cypherpunks):

 A small correction on my part.

 >The reason this happens is that a few syscalls, namely `getcpu()`,
 `gettimeofday()`, `time()`, and `clock_gettime()` use the `RDTSC`
 instruction

 The `getcpu()` and `time()` vDSOs do not use `RDTSC`. I meant to say they
 were all vDSOs, but those two are safe to call even with TSC instructions
 restricted to ring 0. `getcpu()` uses `LSL` instead of `RDTSCP` (since it
 works on all architectures), and `time()` consults a dynamically updating
 value in the VVAR.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21010#comment:3>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
_______________________________________________
tor-bugs mailing list
tor-bugs@xxxxxxxxxxxxxxxxxxxx
https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-bugs