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Re: [tor-talk] orplug, an Android firewall with per-app Tor circuit isolation
Neat and thanks! Perhaps we can think about building this into Orbot,
since we already have a very basic VPN.
On Fri, Feb 12, 2016, at 08:31 AM, Rusty Bird wrote:
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> Hi,
>
> Maybe someone else will find this useful?
> https://github.com/rustybird/orplug
>
> Rusty
>
>
>
> orplug, an Android firewall with per-app Tor circuit isolation
>
> Not affiliated with the Tor Project.
>
>
> Short intro
>
> - - No GUI, please write one ;)
> - - Default deny pretty much everything. Combinable access policies for
> individual apps, whole Android user accounts, etc.: transparent
> torification (circuit-isolated per app), fenced off access to Socks/
> Polipo, LAN access, clearnet access
> - - Multi user account support
> - - Doesn't leak IPv6 traffic
> - - Clean DNS, but requires ANDROID_DNS_MODE=local ROM patch
> - - Logs blocked DNS queries and blocked other packets
> - - Input firewall allows sshd by default
> - - Should work with enforcing SELinux
> - - Includes the "--state INVALID" transproxy leak fix[1]
> - - Tested on CyanogenMod 13 (Android 6.0.1 Marshmallow)
>
>
> Longer intro
>
> Really no GUI, unfortunately I don't have any talent for that. There's a
> simple plain text configuration format[2] though, and the command line
> "orplug-reconf" script could work as a backend to a graphical app. (It
> accepts stdin as well as files for configuration.)
>
> Unconfigured processes may only communicate with localhost and the
> loopback interface. You can configure an individual app, a Unix user/
> group, or an Android account:
>
> - to be transparently torified, with circuit isolation per rule
> - to be allowed access to local TCP ports 9050/8118 for native Orbot
> support
> - to be allowed LAN access (except DNS)
> - to be allowed full clearnet access
>
> All of the above can be combined: Transparently torify a VoIP app as
> far as possible, but allow clearnet access for the remainder (UDP voice
> packets). Or, for a home media streaming app: transparent torification
> with LAN access.
>
> Rules can apply to the primary Android device user account or to other
> accounts.
>
> For incoming traffic, every port is blocked to the outside by default.
> But a hook loads files with raw ip(6)tables-restore rulesets, and one
> such ruleset allows TCP port 22 (sshd).
>
> The init script uses "su -c", which seems to set up everything properly
> SELinux-wise on CM13. I'm not really sure because I don't have a device
> that's able to run in enforcing mode.
>
>
> The DNS mess
>
> Android 4.3+ mixes DNS requests of all apps together by default[3]; when
> a request finally appears in Netfilter, it's unknown where it came from.
> orplug takes a strict approach and blocks this sludge, so it needs a ROM
> patched[4] to export the environment variable ANDROID_DNS_MODE=local
> during early boot.
>
> Unfortunately, ANDROID_DNS_MODE=local makes Android send DNS requests to
> 127.0.0.1, instead of the value of the net.dns1 property. Until this is
> somehow fixed, a rule has been added to redirect allowed clearnet IPv4
> DNS traffic to $ClearnetDNS (defaults to Google's 8.8.8.8).
>
> orplug blocks disallowed DNS requests by sending them to a local dnsmasq
> instance that only logs queries (logcat | grep dnsmasq), but doesn't
> forward them. This is how I noticed that CM13 with "everything disabled"
> nevertheless attempts to connect to the hosts stats.cyanogenmod.org,
> account.cyngn.com, and shopvac.cyngn.com. (Via UID 1000, in this case
> the Settings package.)
>
>
> Captive portals
>
> Enable clearnet access for either UID 1000 (beware of the random stuff
> apparently floating around there), or for a dedicated browser (and run
> "settings put global captive_portal_detection_enabled 0" as root).
>
>
> Installation
>
> 0. Set up some independent way to check for leaks, e.g. corridor[5].
> You've been warned...
> 1. Copy the orplug subdirectory to /data/local/ on your Android device.
> "chmod 755" 00-orplug, orplug-start, and orplug-reconf (all in
> /data/local/orplug/bin/).
> 2. Add the line ". /data/local/orplug/bin/00-orplug" (note the dot) to
> /data/local/userinit.sh and run "chmod 755 userinit.sh".
> 3. Copy the contents of /data/local/orplug/torrc-custom-config.txt into
> the clipboard, e.g. using File Manager. This file contains directives
> for tor to open 99 different TransPort and DNSPort ports.
> 4. In Orbot's settings, paste the clipboard contents into "Torrc Custom
> Config", disable "Transparent Proxying", disable "Request Root
> Access", and choose "Proxy None" in "Select Apps" (that last one only
> applies to current prereleases of Orbot).
> 5. Reboot your device.
> 6. Check that orplug has brought the firewall up: The output of
> "getprop orplug.up" is supposed to say "true". Log files are in
> /data/local/orplug/debug/ in case it didn't work.
> 7. Configure your apps by creating one ore more .conf file(s) in
> /data/local/orplug/conf/ (there's a commented user.conf.example[2]).
> 8. Run "su -c /data/local/orplug/bin/orplug-reconf". The output is
> supposed to say "orplug-reconf: populated". This will happen
> automatically if you reboot.
>
>
> Footnotes
>
> 1. "--state INVALID" transproxy leak fix
> https://lists.torproject.org/pipermail/tor-talk/2014-March/032507.html
>
> 2. Example orplug configuration
> https://raw.githubusercontent.com/rustybird/orplug/master/orplug/conf/rules/90-user.conf.example
>
> 3. Explanation of DNS in Android 4.3+
> http://forum.xda-developers.com/showthread.php?t=2386584
>
> 4. ANDROID_DNS_MODE=local patch (affects only "make bootimage")
> https://raw.githubusercontent.com/rustybird/orplug/master/system-core-ANDROID_DNS_MODE.patch
>
> 5. corridor, a Tor traffic whitelisting gateway
> https://github.com/rustybird/corridor
>
>
> Redistribution
>
> orplug is ISC licensed, see the LICENSE file for details.
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