[issue36484] Can't reorder TLS 1.3 ciphersuites

[Eman Alashwali]

Eman Alashwali  added the comment:

Thanks. Just to clarify regarding your comment: "Applications shouldn't
modify the cipher suites any more.":
I use python to develop scripts for running experiments, which requires me
to simulate specific clients precisely including their TLS 1.3 ciphers
order.
As you know, TLS 1.3 can not have weak ciphers and only 3 or 4 secure ones
are permitted by design. But still the order should be accurate in
simulation experiment settings. This is different from ordinary
development. It is a bit disappointing that the developer can re-order the
weaker ones (in TLS 1.2) but not TLS 1.3.
However, thanks again for your reply.

On Sun, Mar 31, 2019 at 8:46 PM Christian Heimes 
wrote:

>
> Christian Heimes  added the comment:
>
> I don't have plans to implement cipher suite selection for TLS 1.3 any
> time soon, maybe not at all. TLS 1.3 changed cipher selection a lot, making
> the API more complicated. The signature algorithm and key agreement groups
> are handled as separate extensions, resulting in three additional APIs.
>
> Applications shouldn't modify the cipher suites any more. These days TLS
> libraries provide a good and safe selection of suites. Weak ciphers should
> be disabled by either a security update of the TLS library or system-wide
> settings.
>
> There is one workaround: You can influence connection parameters with an
> OpenSSL config file [1][2] by setting OPENSSL_CONF env var. OpenSSL parses
> the file only once, so you have to set it before you start Python.
>
> [1] https://www.openssl.org/docs/manmaster/man5/config.html
> [2] https://fedoraproject.org/wiki/Changes/CryptoPolicy
>
> --
>
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> Python tracker 
> <https://bugs.python.org/issue36484>
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>

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[issue36484] Can't reorder TLS 1.3 ciphersuites

[Eman Alashwali]

New submission from Eman Alashwali :

Wen using the SSL module, I need to be able to reorder the ciphersuites list in 
TLS 1.3. I was able to do this with python using 
SSLContext.set_ciphers(ciphers) when working with TLS 1.2. But this is not 
possible with TLS 1.3 ciphersuites. The need to reorder the ciphersuites is 
needed because one might need a specific order to simulate specific TLS client 
that send the ciphersuites in specific order. Unfortunately this is seems not 
possible now in python with TLS 1.3 as the comment in the documentations says: 
https://docs.python.org/3/library/ssl.html#ssl.SSLContext.set_ciphers

Can you please consider this post as a feature request? Or clarify to me how to 
reorder the ciphersuites list when working with TLS 1.3?

--
assignee: christian.heimes
components: SSL
messages: 339188
nosy: Eman Alashwali, christian.heimes
priority: normal
severity: normal
status: open
title: Can't reorder TLS 1.3 ciphersuites
versions: Python 3.6

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