[tbb-bugs] #24351 [Applications/Tor Browser]: Block Global Active Adversary Cloudflare

Tor Bug Tracker & Wiki blackhole at torproject.org
Wed Nov 29 16:31:01 UTC 2017

#24351: Block Global Active Adversary Cloudflare
 Reporter:  nullius                              |          Owner:  tbb-
                                                 |  team
     Type:  enhancement                          |         Status:
                                                 |  needs_information
 Priority:  High                                 |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Major                                |     Resolution:
 Keywords:  security, privacy, anonymity, mitm,  |  Actual Points:
  cloudflare                                     |
Parent ID:  #18361                               |         Points:
 Reviewer:                                       |        Sponsor:

Comment (by nullius):

 Replying to [comment:22 cypherpunks]:
 > Do you have any actual evidence that they intercepted these decrypted
 packets ''and'' used them for their own malicious goals, or those of other
 3-letter entities? Otherwise this talk is pure gossip, and it belongs on
 tabloids of the DailyMail.

 First off, I ''do'' have evidence that they “intercepted these decrypted
 packets”.  That is how Cloudflare works, period.  If you fail to
 comprehend this, then go back and reread this thread—or read Cloudflare’s
 own documentation—or for that matter, try learning how TLS actually works.
 Without full interception and decryption of each and every connection, it
 would impossible for them to scan application-layer requests for
 “attacks”, insert their own HTTP response headers, and return cache items
 from their own servers.  Even with their misleadingly named “keyless SSL”,
 their diagrams make explicit that they hold the TLS session keys
 (symmetric keys) for all sessions (only in that case, not the server
 certificate private keys).

 As for the rest:

 Absence of evidence is not evidence of absence; and your proposition is
 diversionary, whereas the real issue is one of ''trust'' and of the
 promises made by TLS.

 Fact:  Cloudflare performs mass decryption, then says in essence, ''Trust

 Evidently, you accept that.  For comparison, would you accept key escrow?
 There is no “actual evidence” that police agencies would abuse that power,
 or that blackhats would steal the escrowed keys.  (There is no such
 evidence, only because no such system has ever existed in the wild and at
 scale.)  Also, ''reductio ad absurdum'', would you accept centralized
 decryption of 100% of Web traffic?  90%?  At what threshold would you deem
 such a power a threat in itself?  Whom would you trust to have it?

 You have no evidence that Cloudflare does not misuse this power, other
 than their solemn promise that they don’t.  In other words, no “actual
 evidence”.  But that is beside the point:  Nobody should demand that level
 of trust, on today’s Internet, in today’s world.  The creation of a mass-
 decryption chokepoint is implicitly malicious.

 Sane people prefer to trust cryptographic algorithms.  That is exactly why
 we have such things in the first place.  Why even bother with TLS?  Why
 not simply trust large, reputable companies to deliver packets without
 peeking at them?

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24351#comment:23>
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