nanog mailing list archives

Re: AT&T mobile intercepting TCP sockets?


From: Ca By <cb.list6 () gmail com>
Date: Mon, 21 May 2018 13:53:43 -0700

On Mon, May 21, 2018 at 1:11 PM <lists () as23738 net> wrote:

IME ATT has intercepted virtually everything on mobile (this is on a
hotspot) -

If I curl a HTTP vs HTTPS site, I get a different IP on each (one is
obviously a shared web proxy); if I download images, they won't match
md5-wise with the original version, etc. I have trouble connecting to VPNs
that aren't standard SSL VPNs. They appear to MITM all web traffic they
can. Using third party DNS servers has questionable results.


AT&Fee is also a key player in undermining http2 security with their
“trusted proxy”

https://tools.ietf.org/html/draft-loreto-httpbis-trusted-proxy20-01





On Mon, May 21, 2018, at 12:35 PM, Chris Adams wrote:
I ran into an odd issue with access to a website I manage from AT&T
mobile devices this weekend.  The website worked for everybody not on
AT&T mobile, and AT&T mobile users could access other sites; the problem
was just this combination.

Android and iOS phones, as well as a Linux system tethered to an Android
phone, all had the same problem.  On the Linux system, I disabled IPv6
in Firefox, and it could then connect.  Browsers got various "connection
reset" type errors; on Linux, I could telnet to port 80 or 443, and it
would connect and immediately close.

The site does have an IPv6 address, but I had missed getting the
webserver to listen on IPv6 (my mistake).  Adding that looks to have
solved the problem.

When I ran tcpdump on the server and had someone try to connect from
their AT&T mobile iPhone, I saw three connection attempts a few tenths
of a second apart (all refused by the server).

My question is this: is AT&T mobile intercepting the TCP socket (and
not handling "connection refused" correctly)?  Is that a known thing?

--
Chris Adams <cma () cmadams net>



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