Date: Mon, 18 Jul 2016 22:33:59 +0300 From: Solar Designer <solar@...nwall.com> To: oss-security@...ts.openwall.com Subject: Re: A CGI application vulnerability for PHP, Go, Python and others On Mon, Jul 18, 2016 at 02:23:41PM -0400, Jan Schaumann wrote: > Richard Rowe <arch.richard@...il.com> wrote: > > > The consequence is that an attacker can force a proxy of their choice to be > > used. This proxy receives the full request for anything sent over HTTP > > using a vulnerable client. It can also act in a malicious way to tie up > > server resources (a "reverse slowloris"). > > I know you mentioned it on https://httpoxy.org/, but I think it's worth > stressing explicitly again: use of HTTPS for all requests made by the > application, internal as well as external, defeats this vulnerability > (provided certificates are actually verified). Certificates being actually verified doesn't help against use of this trick for host/port scanning or DoS attacks on third-parties. What does fully defeat this vulnerability is if the application or library only checks a different env var like HTTPS_PROXY for HTTPS connections. So I guess whether use of HTTPS fully defeats or partially mitigates the issue varies by the application or library invoked from a CGI program. Alexander
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