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54 lines
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54 lines
2.3 KiB
ReStructuredText
.. _transparent:
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====================
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Transparent Proxying
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====================
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When a transparent proxy is used, traffic is redirected into a proxy at the
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network layer, without any client configuration being required. This makes
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transparent proxying ideal for those situations where you can't change client
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behaviour - proxy-oblivious Android applications being a common example.
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To set up transparent proxying, we need two new components. The first is a
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redirection mechanism that transparently reroutes a TCP connection destined for
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a server on the Internet to a listening proxy server. This usually takes the
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form of a firewall on the same host as the proxy server - iptables_ on Linux
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or pf_ on OSX. When the proxy receives a redirected connection, it sees a vanilla
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HTTP request, without a host specification. This is where the second new component
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comes in - a host module that allows us to query the redirector for the original
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destination of the TCP connection.
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At the moment, mitmproxy supports transparent proxying on OSX Lion and above,
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and all current flavors of Linux.
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Fully transparent mode
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======================
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By default mitmproxy will use its own local ip address for its server-side connections.
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In case this isn't desired, the --spoof-source-address argument can be used to
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use the client's ip address for server-side connections. The following config is
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required for this mode to work:
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CLIENT_NET=192.168.1.0/24
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TABLE_ID=100
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MARK=1
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echo "$TABLE_ID mitmproxy" >> /etc/iproute2/rt_tables
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iptables -t mangle -A PREROUTING -d $CLIENT_NET -j MARK --set-mark $MARK
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iptables -t nat -A PREROUTING -p tcp -s $CLIENT_NET --match multiport --dports 80,443 -j REDIRECT --to-port 8080
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ip rule add fwmark $MARK lookup $TABLE_ID
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ip route add local $CLIENT_NET dev lo table $TABLE_ID
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This mode does require root privileges though. There's a wrapper in the examples directory
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called 'mitmproxy_shim.c', which will enable you to use this mode with dropped priviliges.
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It can be used as follows:
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gcc examples/mitmproxy_shim.c -o mitmproxy_shim -lcap
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sudo chown root:root mitmproxy_shim
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sudo chmod u+s mitmproxy_shim
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./mitmproxy_shim $(which mitmproxy) -T --spoof-source-address
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.. _iptables: http://www.netfilter.org/
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.. _pf: https://en.wikipedia.org/wiki/PF_\(firewall\)
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