Re: [Acme] ACME vulnerabilities in SimpleHTTP due to common webservers' default virtual host semantics
Niklas Keller <me@kelunik.com> Fri, 08 January 2016 19:43 UTC
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References: <CANUQDCjc2pyD19pC+8F4dhommuaOtf=JpJWOYAh6He3RNK8+Xg@mail.gmail.com> <20160108172709.GA29864@al> <20160108182325.GM18430@eff.org>
Date: Fri, 08 Jan 2016 20:42:57 +0100
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From: Niklas Keller <me@kelunik.com>
To: Peter Eckersley <pde@eff.org>
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Cc: IETF ACME <acme@ietf.org>, Peter Wu <peter@lekensteyn.nl>
Subject: Re: [Acme] ACME vulnerabilities in SimpleHTTP due to common webservers' default virtual host semantics
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2016-01-08 19:23 GMT+01:00 Peter Eckersley <pde@eff.org>: > On Fri, Jan 08, 2016 at 06:27:09PM +0100, Peter Wu wrote: > > > Peter (Eckersley), you reported this concern with the premise that it is > > a common configuration mistake that impacts many hosting providers. Do > > you have scans backing up that concern? Websites that are managed by a > > single entity (i.e. not shared hosting providers) with this > > configuration "mistake' are not a problem. > > I haven't spent the time to conduct a thorough scan to get numbers, but > this type of configuration is very easy and natural to create, and manually > examining the https:// responses of a handful of Alexa top 100K domains > (starting in the middle of the list, not the top) showed a tremendous > diversity of strange behaviours for domains where https:// has not been > officially deployed. > > If someone wants to do a scan to try to characterise all of those > behaviours, go for it! > > > > > > > The restriction in the specification has an unfortunate consequence: > > sites which are only accessible over port 443/HTTPS (because other ports > > are blocked / not forwarded in a NAT network) can no longer be > > validated. > > That's not the case. You can use the TLS-SNI-01 challenge type on those > systems. > > The current language describing it in the spec is terrible and needs to > be rewritten, but it's quite simple: add an extra :443 vhost entry to > your server config, serving a self-signed cert created to pass the > challenge. Unfortunately, this requires a server configuration reload. http-01 is still a lot easier, it doesn't require any configuration change. I think it's best to allow http-01 over HTTPS on port 443 if port 80 is not reachable. This should eliminate the vulnerability, but allow verifying HTTPS-only sites with http-01. Best Regards, Niklas > -- > Peter Eckersley pde@eff.org > Chief Computer Scientist Tel +1 415 436 9333 x131 > Electronic Frontier Foundation Fax +1 415 436 9993 >
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Peter Eckersley
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Peter Wu
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Niklas Keller
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Peter Eckersley
- [Acme] ACME vulnerabilities in SimpleHTTP due to … Niklas Keller
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Niklas Keller
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Peter Wu
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Peter Eckersley
- Re: [Acme] ACME vulnerabilities in SimpleHTTP due… Jakub Warmuz