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

[Katherine Mcmillan]

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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