[stunnel-users] Safest suggested client/server stunnel configurations to prevent MITM attacks
leandro.avila at ymail.com
Mon Oct 22 21:50:07 CEST 2012
> From: Michael K. Avanessian <michael at mka.net>
>To: "stunnel-users at stunnel.org" <stunnel-users at stunnel.org>
>Sent: Friday, October 19, 2012 10:41 PM
>Subject: [stunnel-users] Safest suggested client/server stunnel configurations to prevent MITM attacks
>I’m currently tunneling SSH over SSL using stunnel.
>I thought that stunneled ssh data was safe. However, recently I’ve read that if going through a sophisticated http/https proxy, it’s possible to be hacked by a “legitimate” mitm attack to fool an SSL client.
Tunneled and not-tunneled SSH data _is_ safe. The SSH protocol is pretty secure by itself.
My understanding is that to pull off the type of SSL/TLS data inspection that you mention
there has to be some work done on the client side of the connection. (Install a custom
CA certificate in the trusted certificate store of the client machine)
So even if you were on such a network, as long as your "attacker" does not have control
of your machine. the SSL/TLS protocol will protect you because of the way keys (certificates)
are verified. (Notice the key word here is verified)
>Is it still possible to configure stunnel so that ssl can’t be compromised between both ends?
>I’m going to take a wild guess here; which I’m sure I’m probably wrong. But, could I just install stunnel; and, let it create automatically a self-signed (stunnel.pem) certificate file… then just copy that file to the stunnel install on the other end? That way both sides are already aware of each other’s public keys; and, wouldn’t be vulnerable during the initial unencrypted handshake?
>I’m sure I’m probably way off; and, there’s more I need to do in stunnel’s configuration to further ensure the SSL won’t be compromised.. such as the stunnel “verify” setting. I’m not sure which setting to have it; and, what it actually does.
>I’m hoping someone could shed some light on this with simple suggested clientà server configs that would keep ssl uncompromised as much as possible.
>Thanks in advance!
The configuration you are looking for stunnel involves the verify level 3 setting on the config
(Verify peer with locally installed certificate)
Plus the key management involved to set that up.
Take a look a this document. It is a little out of date. BUT the part about setting up the
certificates on client and server still applies. and is a good way to start
Hope this helps
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