Re: [TLS] weird ECDSA interop problem with cloudflare/nginx

mrex@sap.com (Martin Rex) Tue, 26 July 2016 07:19 UTC

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Date: Tue, 26 Jul 2016 09:19:38 +0200 (CEST)
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From: mrex@sap.com (Martin Rex)
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Subject: Re: [TLS] weird ECDSA interop problem with cloudflare/nginx
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Correction--

I'm sorry, I mistyped the firefox config, this should have said
the chacha20_poly1305 (0xcc 0xa9) cipher suite was the only one enabled.


 
Martin Rex wrote:
> I've just run into a weird interoperability problem with an (alleged)
> cloudflare/nginx TLS server and my personal Firefox settings.
> 
> https://regmedia.co.uk/2015/07/14/giant_weta_mike_locke_flicker_cc_20.jpg
> 
> 
> Traditionally I have all TLS ciphersuites with ECDSA disabled through
> about:config, but it seems that recently two new TLS ciphersuites were
> added to FF, which caused complete loss of interop with regmedia.co.uk
> for me with my existing configuration. (Loss of pictures&media on the
> www.theregister.co.uk news site).
> 
> specifically, after the FF update, this new TLS ciphersuite:
> 
>    security.ssl3.ecdhe_ecdsa_aes_128_gcm_sha256  (0xcc, 0xa9)

    security.ssl3.ecdhe_ecdsa_chacha20_poly1305_sha256  (0xcc, 0xa9)
 
> was the only ECDSA cipher suite enabled in my Firefox 47.0.1, and this
> kills connectivity (TLS handshake_failure alert) with regmedia.co.uk.
> 
> It looks like a bug in the cloudflare/nginx cipher suites selection
> algorithm, which appears to blindly go for ECDSA, even though there is
> no actual ECDSA cipher suite available which the server supports.
> 
> 
> -Martin