Technicolor Hacks

A collection of configuration for detoxing and improving the Technicolor TG799vac modem. Firstly, we flash the modem and get root, using the publicised methods care of Mark Smith online. Then, we access the modem, switch back to more recent firmware, and then tweak that firmware to remove backdoors, telemetry, unecessary services, add features like SSH, modem UI improvements, disables LEDs so your night stays dark, changes your physical Status button, also known as the "easy reset" button, to toggle LEDs on/off, and more.

The configuration present may work on other devices, but it is specifically geared for the TG799vac. There are no guarantees made that any or all of the code will work for you or suit your needs. Test carefully and be prepared that some or all may not work on your device or your firmware.

Instructions are currently written for use on a *nix-style OS but have been successfully also used under Windows as well. If you're on Windows, you can can try with the Windows Subsystem for Linux or simply just do things manually (such as downloading zip files from GitHub instead of cloning and running scripts interactive using PuTTY).

How to

Setup

1. Disconnect any form of WAN connection from your modem, such as the xDSL line or Ethernet connection on the WAN port. This is super important in ensuring that the modem's firmware doesn't go auto-updating.

2. Have a computer or device on hand where you can set up the following tools. If you don't have Python (with tkinter support) or Git installed, you'll need to install them both or figure out a plan to proceed manually.

   Your device will need to have a GUI (eg not be a headless server) as well for at least when tkinter gets used for the autoflashgui tool. Everything else should work headless, if you're so inclined.

3. Get the latest version of these scripts; you'll need them for later:

   git clone https://github.com/davidjb/technicolor-tg799vac-hacks.git

   Make sure you do this on your computer/device rather than on your modem.

4. Get the latest version of autoflashgui, the firmware flashing and root tool. My fork has one fix awaiting a PR into the main repository which is why I'm using that for now:

   git clone https://github.com/davidjb/autoflashgui.git

   Again, make sure this is on your computer/device and not your modem.

5. Get the firmware for your TG799vac device. You'll need the two firmwares as indicated below. For completeness, here are the SHA-256 hashes:

   38b41546133b2e979befce8e824654289aa237446fc4118444f271423c35e3fa vant-f_CRF687-16.3.7567-660-RG.rbi
   0c9bf5e739600ceae61362eebc6ee271783ff85e5d60e3c3076f98bd37648d02 vant-f_CRF683-17.2.188-820-RA.rbi
   

6. Setup the autoflashgui tool:

   cd autoflashgui
   virtualenv .
   source ./bin/activate
   pip install robobrowser==0.5.3

Flash and get root

If your modem happens to be running a newer firmware version (such as an Over-The-Air [OTA] upgrade that happened) or you happen to get locked out for any reason, try a factory reset with the modem physically disconnected from the Internet.

To factory reset, get a paperclip and hold down the reset button for 15 seconds. Release the button and wait a few moments -- the modem will restore, all the LEDs will flash and the modem will reset.

1. Start the tool:

   python autoflashgui.py

2. Flash vant-f_CRF683-17.2.188-820-RA.rbi with the tool. This will fail to root (console will continually keep trying to connect and fail; this is okay). In my second attempt with a modem starting from firmware 15.3, this actually appeared to succeed and send comamnds to the newly-booted 17.2 firmware, but the SSH port wasn't open.

3. Kill the tool in the console with Control-C.

4. Flash vant-f_CRF687-16.3.7567-660-RG.rbi with the tool. This will take a little while as it authenticates, then flashes, waits for a reboot of the modem and then eventually proceeds to perform command injection on the modem.

   If at this point the modem is not allowing SSH connections, then you may need to reflash the version of 17.2 now when on what should be a rooted version of 16.3. This is something I observed when the firmware first started out at 17.2 on one specific device, so I suspect the flashing of 17.2 when already on some version of 17.2 meant the flash didn't take or apply correctly. In any case, reflashing 17.2 at this point (and then reflashing 16.3 again...) solved this for me. Once you do get an SSH session available, you can continue on.

5. When done, SSH to the modem as root and change the password immediately:

   ssh [email protected]
   # Now on the modem...
   passwd

6. Remove the pre-existing /etc/dropbear/authorized_keys file and ideally replace it with your own. This is a fun little backdoor the devs left there, judging by the comment TCH Debug on one of the keys.

7. Reboot the modem to complete disabling the services that were killed during the rooting process with autoflashgui.py

Root and switch to new firmware

By this point, your modem is now running 16.3 firmware and has the 17.2 firmware on board in its inactive, secondary flash partition. We'll now switch over to the latter firmware after injecting the ability to give ourselves root.

1. Re-connect to the modem's wifi network and SSH back in to run the contents of 01-root-and-switch-fw.sh:

   ssh [email protected] 'sh' < ./01-root-and-switch-fw.sh

   There are more secure ways to run the file, like actually inspecting the contents. It's up to you how safe you'd like to play it and mostly how much you trust me / GitHub.

2. Wait several minutes for the modem to reboot.

Reconfigure new firmware

At this point, the modem is back running 17.2 and SSH is available on port 6666. We can now go wild and clean up the modem.

1. Re-connect to the modem's wifi network and SSH back in. The password is currently root, which you'll change immediately:

   ssh [email protected] -p 6666
   # Now on the modem...
   passwd
   exit

2. Run the contents of 02-detox.sh on the modem the SSH session. The plan here is to disable and reset Telstra-based config on the device, disable OTA updates, close other security holes and backdoors, disable telemetry, replace the Telstra logo with Technicolor's logo and unlock various other features like SSH, web UI and so on. Consult the source to check the specifics if you want to opt-in to specific changes:

   ssh [email protected] -p 6666 'sh' < ./02-detox.sh

   There's a bit happening here in this script so I encourage you to check out the source to note what's being disabled and modified. In particular, you can confirm that TR-069/CWMP is disabled by following the comments in the script so that you're sure you've protected yourself against the relevant security risks associated with this protocol.

3. At this point, you can now SSH back into the modem whenever you'd like on the standard port 22:

   ssh [email protected]

4. Once you've confirmed you can do this, run the following in the SSH session on the modem to clear the original configuration we used to root the modem:

   echo > /etc/rc.local

   We do this last to be entirely sure you're not going to accidentally lock yourself out.

5. Add your own SSH public key into the file /etc/dropbear/authorized_keys on the modem. Edit on the modem via an editor like vi or SCP a file from your computer across.

6. Back on your host machine, copy the technicolor-logo.svg image to your modem's img directory such that it becomes available for use in the web interface:

   scp technicolor-logo.svg [email protected]:/www/docroot/img/

   If on Windows, you can use WinSCP to achieve this.

7. Reboot the modem again to finalise the configuration. This implicitly results in the SSH server on port 6666 no longer being started.

   ssh [email protected] 'reboot'

Futher customisation

The following are specific configuration items to using the modem as a basic modem only, with a few improvements like the ability to turn off the LEDs and speed boosts.

1. Run 03-configure.sh to set various additional settings:

   ssh [email protected] 'sh' < ./03-configure.sh

   It does the following:

   • Disables WWAN support
   • Disables Printer sharing
   • Disables Samba / DLNA
   • Disables Telephony (MMPBX)
   • Disables Traffice Monitoring
   • Disables Time of Day ACL rules
   • Explicitly disables Wake on LAN (not enabled by default)
   • Adds ability to turn LEDs on or using the physical Status button (via the newly added toggleleds.sh script)
   • Disables all LEDs by default (and on boot)
   • Enables OpenWrt repository feeds for opkg (only affects modems with Internet access [not bridged modems] and that there's limited storage space unless you configure extroot)

   You can opt-in or out of any of these changes by just running the bits you want or commenting out the bits you don't.

2. If on VDSL2 (eg FTTN/FTTC/FTTB), run 04-vdsl2.sh as well:

   ssh [email protected] 'sh' < ./04-vdsl2.sh

   Otherwise, you can go to the xDSL Config card in the UI and select your mode(s). If you do this, click Save and close the modal; the modal will look like it didn't work, but it will have saved.

3. Head to the web-based UI at http://10.0.0.138 and go to the Advanced tab. Go to the Gateway card and set the timezone. Disable Network Timezone and then choose the appropriate Current Timezone.

Getting Internet access

The last step in actually getting connected up the Internet comes down to on how you're planning on using the modem.

As a modem/router

Head to the web-based UI at http://10.0.0.138 and go to the Advanced tab.

Go to the Internet Access card and set the PPPoE username and password and the modem should connect automatically. You're done.

As a bridged modem

1. Connect an Ethernet cable between port 1 (far left) of the modem and your router's WAN port.

2. Head to the web-based UI at http://10.0.0.138 and go to the Advanced tab.

3. Go to the Local Network card and click the link in the card heading.

4. Scroll down to Network mode and click Bridged Mode.

5. Confirm this action and the modem will reboot automatically.

6. Whilst it reboots, go to your router's settings and configure your WAN to use PPoE with the relevant username and password. How you do this depends on your router.

7. Once the modem has restarted, your router should be automatically connected to the Internet.

From here, we need to reconfigure the modem a futher time to shut a few final services down like dnsmasq, WiFi and so on. In truth, most things are already configured to have been disabled (via uci configuration), but certain services like dnsmasq and odhcpd are still running, though they're not doing anything.

You can configure the setup however you'd like, but To make life simple, I put the modem on my main network so I can still SSH to it. If you don't want this, you could manually plug an Ethernet cable into the modem if you ever need to access it again.

1. Change the modem's IP address to be a static IP your router's subnet (such as 192.168.1.x) so it'll work as a device on the router's network:

   ssh [email protected]
   # Set your own LAN IP address and subnet here
   uci set network.lan.ipaddr='192.168.1.x'
   uci set network.lan.netmask='255.255.255.0'
   uci commit
   /etc/init.d/network restart

2. Connect an Ethernet cable between any port on the modem to a LAN port on your router.

3. Access your router's network and check you now access the modem at 192.168.1.x. The dashboard should load fine.

4. Once you've confirmed this, then run the final 05-bridge-mode.sh script to shut down the remaining services. Note: this includes terminating WiFi so make sure you're accessing the modem via Ethernet (eg via your router) at this point. Also make sure you use your new IP address.

   ssh [email protected] 'sh' < ./05-bridge-mode.sh

5. Check out your extremely slimmed down set of open connections with netstat -lenp: just Nginx for the web UI and Dropbear for SSH with network connections and underlying dependencies listening on UNIX domain sockets.

Even more

1. Install any other OpenWRT packages you want. At this point, your bridged modem probably doesn't have access to the web so download packages to your local computer, SCP them to the modem and run the following command on the modem to install them:

   opkg install ./package-name-here1.0_brcm63xx.ipk

2. Set the admin user's password in your modem's UI under the Maintenance tab. Once this is set, the UI will prompt for login instead of just showing the advanced dashboard automatically.

3. Improve the security on the web interface for the modem by installing the nginx.conf file present in this repo over the top of the existing config. This requires a little tweaking because of server name-specific configuration to workaround redirection in nginx:

   # Run this on your host machine
   IP=192.168.1.x
   HOSTNAME=modem.example.com
   sed "s/10.0.0.138/$IP/g" nginx.template.conf > nginx.conf
   sed -i "s/mygateway.gateway/$HOSTNAME/g" nginx.conf
   scp nginx.conf root@$IP:/etc/nginx/nginx.conf
   ssh root@$IP '/etc/init.d/nginx restart'

   This config hardens the Nginx instance by stopping listening on "assistance" port 55555 and port 8080 for proxying, as well as minor improvements as well with using HSTS, redirecting port 80 to 443 and running only over 443 / HTTPS.

   Note that the modem generated its own self-signed certificate so you might want to consider setting up your own Let's Encrypt certificate on the modem via acme.sh.

Notes

Introspection

To further investigate what's actually going on in this modem, the following are helpful:

• ps command - shows everything that's running
• netstat -lenp command - shows everything that's listening on sockets (TCP, UPD, Unix etc)
• uci show command - dumps the entire OpenWRT configuration for you to look at
• logread -f command - access logs for most services (which use syslog. Pass an argument of -e nginx to match log entries just related to Nginx, which is perfect for debugging errors in the web UI.
• /etc/init.d/* files - look at the services present; some of which may be enabled or not
• for F in /etc/init.d/* ; do $F enabled && echo $F on || echo $F **disabled**; done - display the status of all init scripts
• /etc/config/* files - generally the source files for uci show but displayed in a perhaps more human-readable fashion
• /www/* files - the source files for the Lua web interface
• /sbin/*.sh, /usr/bin/*.sh, /usr/sbin/*.sh files - the locations containing various executable files, many of which are custom-written for this hardware

Services

• transformer: critical service as it underpins the Gateway web UI. Stopping and disabling this service will crash/reboot the modem.

Compatible OpenWrt packages (opkg)

To confirm which version of OpenWrt you're running, look at the release file by running the following command on the modem:

cat /etc/openwrt_release

In my case, this looks like so:

DISTRIB_ID='OpenWrt'
DISTRIB_RELEASE='Chaos Calmer'
DISTRIB_REVISION='r46610'
DISTRIB_CODENAME='chaos_calmer'
DISTRIB_TARGET='brcm63xx-tch/VANTF'
DISTRIB_DESCRIPTION='OpenWrt Chaos Calmer 15.05.1'
DISTRIB_TAINTS='no-all busybox'

So I can see I'm using version 15.05.1, the release called Chaos Calmer. I can also see the chipset/architecture my OpenWrt and its packages were built for -- brcm63xx-tch. The -tch at the end implies something special for Technicolor (assuming TCH isn't some grand coincidence since they use TCH as their stock ticker, SSH key comments and so on) but in my experience, packages for the brcm63xx architecture all work fine.

The following packages from https://archive.openwrt.org/chaos_calmer/15.05.1/brcm63xx/generic/packages/ have been confirmed to work on this device:

• iperf
• iperf3
• openssh-client
• openssh-client-utils
• openssh-keygen
• openssh-sftp-client
• unzip

For other release versions or differing hardware, browse up the directory structure on that URL and find your own compatible packages.

Various backup copies of packages can be found in the pkg/ directory in this repository. I manually copy the packages onto my modem since my modem is configured as a bridge and is explicitly configured not to have Internet access.

Most other packages for this OpenWrt release/architecture should work, but some may conflict with existing packages or files on the device. There's also only 32MB of storage on the modem (24.3MB available on mine) so this is a pretty limiting factor in installing extra software. You could consider some sort of extroot configuration if you wanted to install larger or more packages.

VDSL2 Introspection

xdslctl --help
xdslctl profile --show

Note that running xdslctl configure makes the DSL line resync and possibly other things as well; reboot the modem after this to ensure any side effects don't persist.

From http://whrl.pl/Re6mCZ.

Bridging

brctl help
brctl show

Shows the current status of the bridge on the modem.

Telnet fallback

OpenWRT has a telnet fallback if your system is configured accordingly and Dropbear/SSH aren't running: it'll run telnet instead. If this isn't what you want, then you can disable it thusly:

/etc/init.d/telnet stop
/etc/init.d/telnet disable

Note that this might result in you being locked out later if say SSH were to crash on boot. Unlikely, but you never know.

VLAN for VDSL2

It's possible to add the VLAN configuration into the UI. For now, I don't need this but I'll consider formalising it later. Edit the file at /www/docroot/modals/broadband-modal.lp like so:

local lp = require("web.lp")
lp.setpath("/www/snippets/")

[...]

lp.include('broadband-vlan.lp');

and resart Nginx.

IPoE

There are various settings for IPoE within uci's settings (eg uci show). Evidence online says that IPoE is possible with this modem and may

Power configuration

pwrctl config --cpuspeed 8      # Default: 1  (UI shows 0)
pwrctl config --wait on         # Default: on
pwrctl config --sr on           # Default: off
pwrctl config --ethapd on       # Default: on
pwrctl config --eee on          # Default: on
pwrctl config --autogreeen on   # Default: on
pwrctl config --avs deep        # Default: off + doesn't do anything

In initial testing, teaking settings appeared to drop power consumption slightly but it's too soon to tell. The --avs (Adaptive Voltage Scaling) option doesn't appear to have any effect on the TG799vac; it always stays disabled.

Jumbo frames

uci set network.bcmsw.jumbo='1'
uci commit
/lib/network/switch.sh

(currently untested)

Credit and thanks

The root method is care of Mark Smith https://forums.whirlpool.net.au/user/686 and is greatly appreciated.

The basis for the tweak instructions come from Mark Smith, from Steve's blog at https://www.crc.id.au/hacking-the-technicolor-tg799vac-and-unlocking-features/ and various comments on this Whirlpool thread.

Contributing

Pull requests are welcome for adding features or fixing bugs. Open an issue to discuss improving the default choices. Note this is not a support forum so any questions or requests for help will be closed.

Licence

MIT, see LICENCE.txt

TODO

• Disable LED lights on Ethernet ports. This looks to be possible via ethswctl -c regaccess ... but we need to know the right offset and data settings.