[tor-bugs] #21005 [Applications/Tor Messenger]: Enforce Stronger Ciphers in Tor Messenger

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#21005: Enforce Stronger Ciphers in Tor Messenger
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 Reporter:  cypherpunks                 |          Owner:
     Type:  enhancement                 |         Status:  new
 Priority:  Medium                      |      Milestone:
Component:  Applications/Tor Messenger  |        Version:
 Severity:  Normal                      |     Resolution:
 Keywords:  Tor Messenger               |  Actual Points:
Parent ID:                              |         Points:
 Reviewer:                              |        Sponsor:
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Comment (by arlolra):

 Thanks for your pursuit.

 > an user should not enforce stronger ciphers by setting a higher security
 level

 Right, I reconsidered that here,
 https://blog.torproject.org/blog/tor-messenger-
 030b1-released#comment-220691

 As an experiment, I changed my settings to what you suggested above.

 When connecting to my accounts, I was presented with,

 {{{
 Error: An error occurred during a connection to
 freenodeok2gncmy.onion:6697.

 Cannot communicate securely with peer: no common encryption algorithm(s).

 Error code: <a id="errorCode"
 title="SSL_ERROR_NO_CYPHER_OVERLAP">SSL_ERROR_NO_CYPHER_OVERLAP</a>
 }}}

 That's freenode's onion (we need to consider IRC as well).

 Running `nmap -Pn --script ssl-enum-ciphers -p 6697 chat.freenode.net`
 gives me,

 {{{
 |   TLSv1.2:
 |     ciphers:
 |       TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (dh 2048) - A
 |       TLS_DHE_RSA_WITH_AES_256_CBC_SHA (dh 2048) - A
 }}}

 The first one on the list is recommended in RFC 7525, but not supported in
 NSS, see ticket:18129#comment:11

 > or deliberately use the ... server

 which would mean enabling `security.ssl3.dhe_rsa_aes_256_sha` as a
 distinguisher.  Someone suggested this isn't an issue because,

 > your email/xmpp provider already "knows" you

 https://blog.torproject.org/blog/tor-messenger-
 030b1-released#comment-221194

 but that's a global setting that's going to be advertised to all
 connections and might not play well with temporary accounts in #16606

 On another note about the `security.ssl3.*`, the rc4 suites aren't enabled
 despite saying `true`.  See ticket:18129#comment:7 for the client hello.

 Anyways, I think I agree with the spirit of the ticket.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21005#comment:1>
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