On 10/10/17 21:19, davide.motti wrote:
Hi to everybody,
Last week I've set up Squid as transparent Proxy and everything seems to
work fine, it cache HTTP and HTTPS connections without any problem.
The only think that "worries" me is that if I put the "intercept" flag
on the http_port and on the https port I'm not able to connect to any
site, but if I put off the "intercept" flag the I connect to all sites
in transparent mode (no settings on the client's browser).
The configuration you have is not a "transparent proxy" unless you have
the tproxy or intercept flags in squid.conf port lines. They are what
tells Squid to do the MITM "transparent" things.
Also, you do not have any https_port in this config. So port 443 traffic
cannot be received, no matter how it gets to Squid.
So I'm running Squid-3.5.27 on Ubuntu Server 16.04 LTS and it was so
compiled:
./configure --build=x86_64-linux-gnu --prefix=/usr --localstatedir=/var
--libexecdir=${prefix}/lib/squid --datadir=${prefix}/share/squid
--sysconfdir=/etc/squid --mandir=/usr/share/man
--with-swapdir=/var/spool/squid --with-default-user=proxy
--with-logdir=/var/log/squid --with-pidfile=/var/run/squid.pid
--with-open-ssl=/etc/ssl/openssl.cnf --with-filedescriptors=65536
--enable-ssl-crtd --enable-linux-netfilter.
The main squid.config file:
http_port
3128
http_port 192.168.21.111:3129
http_port 192.168.21.111:13130 ssl-bump generate-host-certificates=on
dynamic_cert_mem_cache_size=4MB cert=/etc/squid/ssl_cert/myRCA.pem
acl debian src 192.168.7.112
acl debian src fe80::a2ce:c8ff:fe1e:bfb8
acl localhost src 127.0.0.0/32
acl SSL_ports port 443
acl Safe_ports port 80
acl Safe_ports port 443
acl Safe_ports port 21
acl Safe_ports port 70
acl Safe_ports port 3128
acl Safe_ports port 3129
acl Safe_ports port 403
acl Safe_ports port 409
acl Safe_ports port 210
acl Safe_ports port 1025-65535
acl Safe_ports port 280
acl Safe_ports port 488
acl Safe_ports port 591
acl Safe_ports port 777
acl CONNECT method CONNECT
# HTTP ACCESS
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost manager
http_access allow debian
http_access allow localhost
visible_hostname 20150604-004.intern.modomoto.de
acl step1 at_step SslBump1
ssl_bump peek step1
ssl_bump bump all
sslproxy_options ALL
sslproxy_cert_error allow all
sslproxy_flags DONT_VERIFY_PEER
The above 5 lines disable *all* security that TLS has to offer. Chances
of your network being " p0wned " are quite high.
This is also possibly why the intercept *appears* to work.
sslcrtd_program /lib/squid/ssl_crtd -s /var/lib/squid/ssl_db -M 4MB
sslcrtd_children 10
Squid iptables rules:
# Generated by iptables-save v1.6.0 on Mon Sep 25 09:34:12 2017
*mangle
:PREROUTING ACCEPT [41705:23328287]
:INPUT ACCEPT [40269:23242848]
:FORWARD ACCEPT [6:2262]
:OUTPUT ACCEPT [32950:6122247]
:POSTROUTING ACCEPT [33060:6138510]
COMMIT
# Completed on Mon Sep 25 09:34:12 2017
# Generated by iptables-save v1.6.0 on Mon Sep 25 09:34:12 2017
*nat
:PREROUTING ACCEPT [2731:496529]
:INPUT ACCEPT [1440:370186]
:OUTPUT ACCEPT [3278:202202]
:POSTROUTING ACCEPT [41:2041]
-A PREROUTING -s $CLIENT_IP -p tcp -m tcp --dport 80 -j DNAT
--to-destination
$SQUID_IP:$HTTP_SQUID_PORT
-A PREROUTING -i $CLIENT_INTERF -p tcp -m tcp --dport 80 -j REDIRECT
--to-ports $HTTP_SQUID_PORT
-A PREROUTING -s $SQUID_IP -p tcp -m tcp --dport 443 -j DNAT
--to-destination $SQUID_IP:$HTTPS_SQUID_PORT
-A PREROUTING -i $CLIENT_INTERF -p tcp -m tcp --dport 443 -j REDIRECT
--to-ports
$HTTP_CLIENT_PORT
-A POSTROUTING -o $CLIENT_INTERF -j MASQUERADE
...
Why are you looping port 443 traffic outbound from Squid back into its
receiving port?
And you have replaced most of the other important details with variable
names. You have three HTTP ports (with various IPs) and zero HTTPS ports
in squid.conf so its not even clear what these variables are referring
to by name.
Please replace your iptables rules with the ones listed at
<https://wiki.squid-cache.org/ConfigExamples/Intercept/LinuxRedirect>
My client act as his own router and his iptables rules are the followings:
REDIRECT/DNAT erases the destination IP Squid is connecting to when in
"transparent" intercept mode. This is what you MUST NOT have any NAT
between the client browser and Squid machine. Packets MUST be routed
instead (possibly through a tunnel, but still routed).
As I told the intercept mode works without the "intercept flag" on the
http_port directive: I would like just to know if it's normal or I miss
something in my config.
That is not normal, and not good at all. It hints that; a) the client is
somehow sending proxy-format HTTP traffic over port 80/443 where only
origin-format is permitted, or b) the proxy has been hacked to disable
the CVE-2009-0801 hijacking protections.
Amos
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