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Re: [tor-bugs] #23588 [Core Tor/Tor]: Write fascist_firewall_choose_address_ls() and use it in hs_get_extend_info_from_lspecs()

#23588: Write fascist_firewall_choose_address_ls() and use it in
hs_get_extend_info_from_lspecs()
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  neel
     Type:  defect                               |         Status:
                                                 |  needs_revision
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.5.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  prop224, tor-hs, single-onion,       |  Actual Points:
  ipv6, 034-triage-20180328,                     |
  034-removed-20180328                           |
Parent ID:  #23493                               |         Points:  1
 Reviewer:  teor                                 |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by neel):

 I think I know what the bug for `hs-v23-ipv6-md` is: some addresses are
 being marked as they don't make it through
 `fascist_firewall_allows_address_ap()` (I believe the main Tor codebase
 does not make addresses go though this now, nor does my old "simplified"
 address choosing code that got abandoned).

 A solution can be to add a flag like `verify_addr` to
 `fascist_firewall_choose_address_impl()`,
 `fascist_firewall_choose_address()`, and
 `fascist_firewall_choose_address_base()` that determines whether we should
 verify the addresses or not, and set this flag to `0` in
 `fascist_firewall_choose_address_ls()`'s call to
 `fascist_firewall_choose_address_base()` and `1` in other calls.

 In my solution, we end up choosing addresses by replacing code in
 `fascist_firewall_choose_address_impl()` from something like this:

 {{{
    if (fascist_firewall_allows_address_ap(a, fw_connection, pref_only,
                                           pref_ipv6)) {
 }}}

 to this:

 {{{
    if (fascist_firewall_allows_address_ap(a, fw_connection, pref_only,
                                           pref_ipv6) || !verify_addr) {
 }}}


 Would this be okay? I know this may not be a good solution, but it may
 help fix this bug we are talking about (and is similar to my previous
 address choosing code which worked, but with the
 `fascist_firewall_allows_address_*` family of functions).

 I also attempted to do a three-hop fallback, and merged it with this
 codebase (not committed at all), but it still crashed with the same error
 described. It is possible that my three-hop fallback is broken.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23588#comment:36>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online

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