How to enable Telnet on samsung TV's


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Telnet is an old-style way of communication between computers. Many embedded systems, including many Samsung TV's (not all) rely on this tool to connect to the outside world through a command line interface (CLI). By default, the telnet functionality is not enabled in our Sammy's, so some actions are needed to switch it on.

If you are not familiar with flashing firmwares, patching binary files etc., I recommend to take some time to read and understand what you are doing first! THIS CAN BRICK YOUR DEVICE !!

Read on for a detailed HowTo of the steps to be taken :

The Safe Way

  • Using SamyGO Telnet Enabler Samsung TV application, you can enable telnet of TV without changing firmware.

Enabling telnet with this program is not dangerous but with wrong telnet commands, still you have a chance to brick your TV. Download this program to your USB Flash, then plug it into your TV. Using the Content Library from the Pup-Up menu, select USB, then under Game menu, select and start the SamyGO application once. The TV will go black and then returns to the menu. This will enable your TV's telnet for one session only. When you reboot your TV (switch off and back on) you need to reopen telnet via the menus. I advise you to use the Automated script if you plan to do some development on your TV. If you just want to have look how things work, the safe way is better. Download SamyGO Telnet Enabler Program.

Prerequisites

(if you do not have ALL of these: Google is your friend, at least for the software):

  • a Samsung TV attached to your local network.
  • a hex editor.
    • Linux : okteta and many others
    • Windows: flexhex, neo, and many others.
  • a crc32 checksum calculator.
    • Linux : okteta 0.3 or later, check, minicrc, etc...
    • Windows: flexhex, be wary of little endian (byte-reversed) checksums, possibly others
  • xor encryption/decryption software.
    • Linux : okteta 0.3 or later, crypt-xor, xor-analyze, etc...
    • Windows: flexhex, possibly others
  • a normal ASCII editor.
    • Linux : emacs, vi, gedit and and many more.
    • Windows: notepad (Or a word processor. Be careful to save in ascii mode, .txt format)
  • a telnet client.

Hacking the Firmware

To acquire telnet access to your tv, do the following:

  • Download the firmware package for your tv from the Samsung website and unpack it. As an example in this HOWTO, the T-CHU7DEUC.exe file for a ue40b70xx is taken. This will also work on any other xor-encoded firmware. Just replace the T-CHU7DEUC in this howto with your firmware name. When working on a linux box, you can unpack it with wine, unrar, or p7zip (just run `7z x <exe>`).
  • Decrypt exe.img.enc in the T-CHU7DEUC/image directory using an xor decrypter with key "T-CHU7DEUC" (the firmware root directory name) and name it exe.img
  • Check the CRC32 checksum of your decrypted file (exe.img). It should match the checksum (8-digit hexadecimal number), <xxxxxxxx> given in validinfo.txt _exactly_:
*007_exe.img_xxxxxxxx*011_appdata.img_126fb41f

If the checksums don't match, check the following: Is the downloaded file not corrupted? Is your decryption flawless?

  • Using a hex-editor, make the following changes to the contents of rc.local in the decrypted exe.img file: locate the lines:
export KF_LOG=/dev/null #Remove engine logging.
cd /mtd_exe/

./exeDSP

and replace just the text element marked bold, as shown below: 

export KF_LOG=/dev/null;/etc/telnetd_start.sh&
cd /mtd_exe/

./exeDSP

-> For safety reasons it is recommended that you don't miss the "&" at the end ( this is not yet considered in the SamyGo Script YET! )

Make sure you do not change the length of the image file. To be on the safe side, replace any unprintable characters on the changed line with spaces, but _keep_ the linefeed (0x0a)

And remember: Think before you type.

  • Re-calculate the CRC32 checksum for the updated image.
  • Using a normal ASCII editor, update validinfo.txt in the T-CHU7DEUC/image directory with the new CRC information: Replace xxxxxxxx in this line with the newly calculated checksum (8 hexadecimal digits, be aware of leading zeros):
*007_exe.img_xxxxxxxx*011_appdata.img_126fb41f
  • Encrypt exe.img again, using xor encryption with key "T-CHU7DEUC" and copy it into the T-CHU7DEUC/image directory. Name it "exe.img.enc"

Flash to TV

  • Move the T-CHU7DEUC directory and all of its contents to an otherwise empty USB drive, plugin the USB drive into your TV and manually start the upgrade via the appropriate menu entry on your TV

Result

  • After upgrade, open a shell and start a telnet session on your tv:
$ telnet aaa.bbb.ccc.ddd

with aaa.bbb.ccc.ddd your tv's IP-address. when prompted, log in as <root> This is what you'll see, when connected: 

$ telnet aaa.bbb.ccc.ddd
Trying aaa.bbb.ccc.ddd...
Connected to aaa.bbb.ccc.ddd.
Escape character is '^]'.

localhost login: root
-sh: id: not found
#

You can now start typing commands. For available commands visit the normal places: /bin, /sbin, /usr/bin and /usr/sbin

Browsing the Firmware

Decoding the run.sh.enc script shows that a bunch of images may be present and will automatically be flashed if found. This includes the kernel, the root filesystem, the u-boot bootloader, and the aux filesystems (below). The former seem to require loading over the USB serial though?

The exe.img.enc file, once decrypted, can be mounted as a normal FAT filesystem. Under Linux, you can do: 

 $ mkdir exe-dir
 $ sudo mount -o loop -t vfat exe.img.dec exe-dir/
 $ ls exe-dir/
 Comp_LIB/   EXE_IMG_VER  JadeTarget      prelink.conf  samdrv.ko
 ddr_margin  Factory.dat  JadeTarget.cfg  rc.local      SpecialItemNumber.txt
 edid/       game_lib/    LifeScenario    ReleaseInfo   value.bin
 exeDSP      InfoLink/    prelink.cache   $rfs_log.lo$  YWidget_LIB/

The appdata.img.enc file, once decrypted, is a normal squashfs image (albeit an old 3.0 version). So if attempts to loop mount this image fail with: 

 $ mkdir app-dir
 $ sudo mount -o loop,ro -t squashfs appdata.img.dec app-dir/
 mount: wrong fs type, bad option, bad superblock on /dev/loop/1,
 $ dmesg | tail -n1
 SQUASHFS error: Major/Minor mismatch, older Squashfs 3.0 filesystems are unsupported

Then you can use unsquashfs from squashfs-tools to unpack it: 

 $ unsquashfs appdata.img.dec
 Parallel unsquashfs: Using 2 processors
 2203 inodes (4374 blocks) to write
 
 [===============================================/] 4374/4374 100%
 created 2190 files
 created 102 directories
 created 13 symlinks
 created 0 devices
 created 0 fifos
 $ ls squashfs-root/
 APPDATA_IMG_VER  Font/            lib/              resource/    widget/
 Demo/            Images_960x540/  QPI_DTV_AUDIO.ts  testPlay.ts


Automated Way

  • If you know what you are doing and are simply looking for a tool that will do all of the hacking for you, then you can use SamyGO Firmware Patcher.
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