53C70R

Since I use LineageOS without any google services some important feature was still missing to find my phone once I lost it. The idea was simple. Gain persistent access, call API requests to get the needed information and send it back to my Nextcloud. I noticed that being able to access the API directly you could actually start to script your own little snippets but we will get to this later.

Lets start with the transport problem. Somehow we have to get access to our smartphone at any time punching holes through firewalls. First method would be to use your own VPN like Wireguard or OpenVPN. But a much more convenient (but battery draining method) would be to use a tor hidden service maybe even using bridges to obfuscate its real intention (Maybe “Orbot”).

Install Termux, Termux:API and Termux:Boot on your Android.
Lets setup the SSH Server and install some dependencies we need later:

Open Termux on your phone and type in:

pkg install root-repo
pkg update
pkg upgrade
pkg install openssh termux-api jq zip
# this will set the password for first login but it is highly advised to use pub-key authentication for your later ssh session
passwd
sshd

Now you should be able to access your phones Termux environment by ssh’ing into it from your Notebook:

ssh root@your.mobile -p 8022

Lets make the ssh session persistent over boot and change some settings (I’ll just show you the content of my setup):

cd ~

~ $ cat /data/data/com.termux/files/usr/etc/ssh/sshd_config
PrintMotd yes
# set this to yes if you want to enable password authentication
PasswordAuthentication no
Subsystem sftp /data/data/com.termux/files/usr/libexec/sftp-server

~ $ cat ~/.termux/boot/start-sshd
#!/data/data/com.termux/files/usr/bin/sh
termux-wake-lock
sshd

After that you should open Termux:Boot once on your phone. Maybe reboot your phone to check if everything works so far. (ssh should be available after reboot)

Well, let us start to have some fun.

Go to app permission settings of your android and give all permissions to Termux:API.

Now ssh into your phone and execute:

termux-setup-storage

tabbing “termux-” will actually show all your tools you can use to control your phone. Should look like this:

~ $ termux-
termux-audio-info            termux-fix-shebang           termux-open                  termux-telephony-deviceinfo
termux-battery-status        termux-info                  termux-open-url              termux-toast
termux-brightness            termux-infrared-frequencies  termux-reload-settings       termux-torch
termux-call-log              termux-infrared-transmit     termux-reset                 termux-tts-engines
termux-camera-info           termux-job-scheduler         termux-sensor                termux-tts-speak
termux-camera-photo          termux-keystore              termux-setup-storage         termux-usb
termux-change-repo           termux-location              termux-share                 termux-vibrate
termux-chroot                termux-media-player          termux-sms-inbox             termux-volume
termux-clipboard-get         termux-media-scan            termux-sms-list              termux-wake-lock
termux-clipboard-set         termux-microphone-record     termux-sms-send              termux-wake-unlock
termux-contact-list          termux-nfc                   termux-speech-to-text        termux-wallpaper
termux-dialog                termux-notification          termux-storage-get           termux-wifi-connectioninfo
termux-download              termux-notification-list     termux-telephony-call        termux-wifi-enable
termux-fingerprint           termux-notification-remove   termux-telephony-cellinfo    termux-wifi-scaninfo

From this point it’s really up to the limitations of your imagination. Some examples could be…

Capture all telemetry and send it to your Nextcloud:

cd ~

~ $ cat scripts/get_telemetry
date="$(date +'%d-%m-%y_%H-%M-%S')"
path="/data/data/com.termux/files/home/records/$date"
echo "create dir..."
mkdir -p $path/txt
echo "get wifi..."
termux-wifi-scaninfo > $path/txt/wifi.txt
echo "get cellinfo..."
termux-telephony-cellinfo > $path/txt/cell.txt
echo "get all sensor data..."
termux-sensor -a -n 1 > $path/txt/sensor.txt
echo "get location..."
while :
do
        echo "trying..."
        termux-location > $path/txt/location.txt
        if [ -s $path/txt/location.txt ]
        then
                echo "got location..."
                break
        fi
done
echo "export to nextcloud..."
zip -r $path/$date.zip $path/txt >&- 2>&-
curl -u USERNAME:GENERATE_YOUR_NEXTCLOUD_APP_KEY -T $path/$date.zip https://cloud.53c70r.de/remote.php/dav/files/sector/termux/

Play presidential alert:

cd ~

~ $ cat scripts/presidential_alert
lat=$(termux-location | jq -r ".latitude")
long=$(termux-location -r last | jq -r ".longitude")
termux-notification -c 'SEE EMERGENCY INFORMATION' -t "LOST DEVICE"
setsid -f sh -c "while true; do termux-volume music 15; sleep 1; done"
termux-torch on
termux-vibrate -f -d 2000
sleep 2
termux-media-player play /data/data/com.termux/files/home/scripts/data/eas.mp3
sleep 11
termux-torch off
termux-tts-speak -s MUSIC "GPS coordinates. latitude: $lat, longitude: $long. WARNING. This system is for the use of authorized users only. Individuals using this computer system without authority or in excess of their authority are subject to having all their activities on this system monitored and recorded by system personnel. Anyone using this system expressly consents to such monitoring and is advised that if such monitoring reveals possible evidence of criminal activity system personal may provide the evidence of such monitoring to law enforcement officials."
killall sh

Some loud alarm:

cd ~

~ $ cat scripts/loud_alarm
setsid -f sh -c "while true; do termux-volume music 15; sleep 1; done"
setsid -f sh -c "while true; do termux-torch on; sleep 1; termux-torch off; sleep 1; done"
termux-media-player play /data/data/com.termux/files/home/scripts/data/alarm.mp3
termux-torch off
killall sh

Tested on Android 10.
Get a root shell to your android via adb and execute;

remount
ssh-keygen -A
mkdir /root
cp -r /data/ssh /root
cp /etc/ssh/sshd_config /root
chmod 740 /root
chmod 700 /root/ssh
touch /root/ssh/authorized_keys
chmod 600 /root/ssh/authorized_keys
chown root:root -R /root

Add your ssh pub-key to “/root/ssh/authorized_keys” than execute:

sed -i 's/\/data\//\/root\//g' /etc/ssh/sshd_config
echo "HostKey /root/ssh/ssh_host_ed25519_key" >> /etc/ssh/sshd_config

Add the file “/root/start” with content;

#!/bin/sh
/bin/sshd -f /root/sshd_config

Add our daemon under “/system/etc/init/sshd.rc”;

service sshd /system/bin/sh /root/start
    user root
    group root
    oneshot
    seclabel u:r:su:s0

on property:sys.boot_completed=1 && property:sys.logbootcomplete=1
    start sshd

Reboot your device, done.

(On LineageOS 18.1 sshd will crash at the moment)
https://gitlab.com/LineageOS/issues/android/-/issues/3437

signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
Cause: null pointer dereference
    x0  0000000000000000  x1  0000007b0bd1dfb8  x2  0000000000000008  x3  0000000000000010
    x4  0000000000000000  x5  8080808080808080  x6  fefefefefefefeff  x7  7f7f7f7f7f7f7f7f
    x8  0101010101010101  x9  ffffff84f42e2047  x10 0000000000000068  x11 000000000b52b678
    x12 000000004f1d3b2b  x13 0000007ff25268cb  x14 0000007b0b6ddd42  x15 0000ffff00000fff
    x16 00000058c010e3f8  x17 0000007b0b66bb30  x18 0000007b0c578000  x19 0000000000000000
    x20 00000058c0110000  x21 000000791b5241f0  x22 000000791b5248e0  x23 0000000000000000
    x24 00000058c00d9e8d  x25 0000007b0baa6ae0  x26 0000000000000001  x27 0000000000000003
    x28 00000058c0111000  x29 0000007ff2527910
    lr  00000058c01071c8  sp  0000007ff2527330  pc  0000007b0b66bb40  pst 0000000080000000

backtrace:
      #00 pc 000000000004ab40  /apex/com.android.runtime/lib64/bionic/libc.so (strlen_default+16) (BuildId: be9c72fe4db37cd191b589b74d090d13)
      #01 pc 00000000000361c4  /system/bin/sshd (main+1720) (BuildId: 610e2671bc203f1b61ef273d60564a86)
      #02 pc 000000000004988c  /apex/com.android.runtime/lib64/bionic/libc.so (__libc_init+108) (BuildId: be9c72fe4db37cd191b589b74d090d13)

cat /etc/fail2ban/filter.d/modsecurity.conf

# Fail2Ban filter for modsecurity
#
[Definition]

failregex = ^<HOST> \- \S+ \[\] \"(.*)\S+\" 444 .+$

will check for HTTP status code 444.

Add this to your “/etc/fail2ban/jail.local”:

[modsecurity]
port = http,https
logpath = %(nginx_access_log)s
enabled = true