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[tor-bugs] #21005 [Applications/Tor Messenger]: Enforce Stronger Ciphers in Tor Messenger
#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 | Keywords: Tor Messenger
Actual Points: | Parent ID:
Points: | Reviewer:
Sponsor: |
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In considering to limit the standard ciphers to the ones recommended in
RFC 7525 from 2015 for torbirdy (ticket:20751), and to minimize the risk
of downgrade attacks, it might be advisable to find a similar solution for
tor messenger, too. (Maybe even a similar way of handling exceptions in
the UX)
Therefor I suggest the following standard settings (torbirdy,
ticket:20751)
1. tls version 1.2 (RFC 5246 from 2008, tls version 1.3 is is going to be
introduced next year)
{{{security.tls.version.min = 3}}}
2. recommended ciphers in accordance to RFC 7525 (from 2015)
{{{security.ssl3.* false}}}
{{{security.ssl3.ecdhe_rsa_aes_128_gcm_sha256 true}}}
{{{security.ssl3.ecdhe_ecdsa_aes_128_gcm_sha256 true}}}
3. Prevent Insecure Recognition
{{{security.ssl.require_safe_negotiation true}}}
{{{security.ssl.treat_unsafe_negotiation_as_broken true}}}
4. Certificate Pinning
{{{security.cert_pinning.enforcement_level = 2}}}
ticket:16494#comment:5 suggests to implement a tbb like slider for Tor
Messenger and to enforce a stronger set of ciphers just for the higher
security settings. As explained in https://blog.torproject.org/blog/tor-
messenger-030b1-released#comment-220689 to follow the recommendations of
the last RFCs tls version 1.2 has to be used (otherwise the recommended
ciphers can't be used). Today, most XMPP server support TLS version 1.2
and are able to use modern ciphers, allowing a downgrade of the ciphers
just allows downgrade attacks and weakens the overall security. Ie, an
user should not enforce stronger ciphers by setting a higher security
level, instead he should get a message in the moment the the server
doesn't support the (stronger) standard cipher than he can decide what to
do, ie either to use a different XMPP server (a server that doesn't
support tls v 1.2 in 2017, is just a bad choice and the server owner might
just do a bad job and even save password as md5 hash etc) or deliberately
use the xmpp sever (if the server used to support stronger encryption and
stops to do so, the user might even know that something is going wrong)
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21005>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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