bug in Lynx' SSL certificate validation -> leaks password in clear text via SNI (under some circumstances)

[Carlo Strub]

Thanks a lot for your email. I added a vuxml entry to inform users.

Best,
Carlo


On Sat, 7 Aug 2021 at 17:07, Katherine Mcmillan <kmcmi046 at uottawa.ca> wrote:

> FYI
>
> ________________________________
> From: Lynx-dev <lynx-dev-bounces+kmcmi046=uottawa.ca at nongnu.org> on
> behalf of Ariadne Conill <ariadne at dereferenced.org>
> Sent: 07 August 2021 10:17
> To: oss-security at lists.openwall.com <oss-security at lists.openwall.com>
> Cc: Axel Beckert <abe at debian.org>; lynx-dev at nongnu.org <
> lynx-dev at nongnu.org>; security at debian.org <security at debian.org>;
> 991971 at bugs.debian.org <991971 at bugs.debian.org>
> Subject: Re: [Lynx-dev] [oss-security] Re: bug in Lynx' SSL certificate
> validation -> leaks password in clear text via SNI (under some
> circumstances)
>
> Attention : courriel externe | external email
>
> Hi,
>
> On Sat, 7 Aug 2021, Thorsten Glaser wrote:
>
> > Axel Beckert dixit:
> >
> >> This is more severe than it initially looked like: Due to TLS Server
> >> Name Indication (SNI) the hostname as parsed by Lynx (i.e with
> >> "user:pass@" included) is sent in _clear_ text over the wire even
> >
> > I *ALWAYS* SAID SNI IS A SHIT THING ONLY USED AS BAD EXCUSE FOR NAT
> > BY PEOPLE WHO ARE TOO STUPID TO CONFIGURE THEIR SERVERS RIGHT AND AS
> > BAD EXCUSE FOR LACKING IPv6 SUPPORT, AND THEN THE FUCKING IDIOTS WENT
> > AND MADE SNI *MANDATORY* FOR TLSv1.3, AND I FEEL *SO* VINDICATED RIGHT
> > NOW! IDIOTS IN CHARGE OF SECURITY, FUCKING IDIOTS…
>
> It turns out SNI is only marginally related to this issue.  The issue
> itself is far more severe: HTParse() does not understand the authn part of
> the URI at all.  And so, when you call:
>
>    HTParse("https://foo:bar@example.com", "", PARSE_HOST)
>
> It returns:
>
>    foo:bar at example.com
>
> Which is then handed directly to SSL_set_tlsext_host_name() or
> gnutls_server_name_set().  But it will also leak in the Host: header on
> unencrypted connections, and also probably SSL ones too.
>
> As a workaround, I taught HTParse() how to parse the authn part of URIs,
> but Lynx itself needs to actually properly support the authn part really.
>
> I have attached the patch Alpine is using to work around this infoleak.
>
> Ariadne
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