[openssl-dev] [openssl.org #4524] [BUG] TLS 1.2 handshake hangs for TLS 1.0 only hosts

[Henrik Hofmeister via RT]

Hi there

I've recently come across what looks to be an internal bug in openssl:

Original symptoms was that neither "curl" or "wget" could access the following site: 

https://coverage.tre.se - this site is using TLS 1.0 (only) and does have some pretty crazy certificate issues - but does show up "green" in most browsers (Unless you're on a system with an openssl which supports TLS 1.2 ).

Accessing the site (curl / wget) hangs during SSL handshake.

I then tried: 
openssl s_client -connect coverage.tre.se:443 which hangs as well

By forcing the protocol to TLS1.0 it will correctly parse and see the certificate. By forcing protocol to TLS1.1 it'll correctly error out saying invalid protocol. Even just telling s_client to not include TLS 1.2 will make it work as expected.

So to sum up: 

My guess would be that some incompatibility between the 1.0 and 1.2 protocol causes 1.2 to not determine correctly that the server does not support it , and as such is unable to fallback to previous versions. 

I have verified this on several ubuntu 14.04 machines with the following openssl versions: 

OpenSSL 1.0.1f 6 Jan 2014


OpenSSL 1.0.2g 1 Mar 2016

And I've verified that it does work as expected on OSX which has a openssl version that does not support TLS 1.2: 

OpenSSL 0.9.8zg 14 July 2015

Hope this helps resolve the issue.

Kind regards, 
Henrik
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Ticket here: http://rt.openssl.org/Ticket/Display.html?id=4524
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