full-disclosure - Re: [FD] SSH host key fingerprint

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Message-Id: <81DD2C0F-CB9E-43BF-9DA4-CD220FFA8980@dckd.nl>
Date: Mon, 1 Sep 2014 22:21:15 +0200
From: Jeroen van der Ham <jeroen@...d.nl>
To: Stephanie Daugherty <sdaugherty@...il.com>
Cc: fulldisclosure@...lists.org, bugtraq@...urityfocus.com,
	John Leo <johnleo@...ckssh.com>
Subject: Re: [FD] SSH host key fingerprint - through HTTPS

Hi,

On 1 Sep 2014, at 10:43, Stephanie Daugherty <sdaugherty@...il.com> wrote:

> Sure it shows me the fingerprint, but it doesn't tell me for sure if that's
> the RIGHT fingerprint or the fingerprint of an imposter,
> 
> It's entirely possible that both myself and that site are BOTH falling
> victim to a MITM attack.(routing attacks, DNS attacks, etc)
> 
> Proper host key verification (which nobody does) ideally means one or more
> of:
> * Verification that the SSH host key is connected via certificate chain to
> a trusted certificate,
> * Comparison to a fingerprint being posted on the organization's OWN https
> site
> * Comparison to a fingerprint provided with a GPG or S/MIME signature from
> the administrator of the machine.
> * Voice verification of the host public key or its fingerprint with the
> administrator of the machine.
> * Obtaining a printed copy of the host public key or its fingerprint
> directly from the administrator.
> 

There is a way now, using the “magic” of DNSSEC and SSHFP records: http://tools.ietf.org/html/rfc4255

You use the DNSSEC hierarchy to create a trust chain. You can then securely publish a signed fingerprint of your SSH host key for that specific machine.

Jeroen.

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