[tor-bugs] #19316 [Applications/Tor Browser]: Make sure our updates are dealing with SSE requirement properly

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#19316: Make sure our updates are dealing with SSE requirement properly
-------------------------------------------------+-------------------------
 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  task                                 |         Status:
                                                 |  needs_revision
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  ff52-esr, tbb-7.0-must,              |  Actual Points:
  TorBrowserTeam201703                           |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by mcs):

 Replying to [comment:7 boklm]:
 > Replying to [comment:1 mcs]:
 > > Similar to the minSupportedOSVersion update manifest attribute that we
 added for the Mac OS 10.6 issue (see
 https://trac.torproject.org/projects/tor/ticket/13047#comment:3), we
 should add support for a new attribute such as: `minInstructionSet="SSE2"`
 >
 > I attached a first version of a patch to do that, but I did not test it
 yet, so it may not work.

 It seems like we just need one attribute in the update manifest, e.g.,
 minSupportedInstructionSet.

 Also, I think your patch is missing a !. Maybe just do something like:
 {{{
 if (!this.unsupported &&
 update.hasAttribute("minSupportedInstructionSet")) {
   let minInstructionSet =
 update.getAttribute("minSupportedInstructionSet");
   if (['MMX', 'SSE', 'SSE2', 'SSE3',
        'SSE4A', 'SSE4_1', 'SSE4_2'].indexOf(minInstructionSet) >= 0) {
   try {
     this.unsupported = !Services.sysinfo.getProperty("has" +
 minInstructionSet);
   } catch (e) {}
 }
 }}}

 (untested).

 > I think there will still be an issue with people upgrading to the new
 ESR52 version from Tor Browser <= 6.5.1 (skipping the version that added
 support for the minInstructionSet attribute), as their browser will not
 know this attribute. If we want to avoid this, we will need to change the
 `update_2` from the updates URL to `update_3` (similar to what we did in
 #13047).

 Do we really need to change to update3? We are not changing the request
 URL. We should add support for the new instruction set attribute to TB
 6.5.2 and then advertise to older Windows browsers an update to 6.5.2.
 Then, after that update is done, the 6.5.2 browser will recognize the new
 attribute and make the appropriate instruction set check. Mozilla does
 this kind of thing once in a while; they call it a step-wise update or
 flag day or something ;)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19316#comment:10>
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