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UnSHc

UnSHc - How to decrypt SHc *.sh.x encrypted file ?

Please note

I will not decrypt any file for people. Issues on GitHub are only to discuss about bug and/or improvement of the tool "UnSHc".

Due to the many problems since shc 4.0.3, there seems to be a need for clarification. In shc 4.0.3 many structural changes have been incorporated, so that shc now makes use of various security mechanisms provided by the linux-kernel itself. Therefore, it is now almost impossible to extract the original shell script at all with current UnSHc version, if the new shc version was used. This requires a more in-depth approach, which means that a modified bash or a modified linux-kernel is needed to bypass the security measures.

If you think you have found a bug, please provide me the encrypted file AND the unencrypted file corresponding. Without these two files I can't reverse it and analyze it. Add some information about the architecture where the encrypted file has been created (what linux distribution and version, what architecture x86 or x64, etc.).

All others "file decryption issues" will be closed directly.

SHc review

SHc (SHell compiler) is a fabulous tool created and maintained by Francisco Javier Rosales Garcia (http://www.datsi.fi.upm.es/~frosal/). This tool protect any shell script with encryption (ARC4).

wget -q http://www.datsi.fi.upm.es/~frosal/sources/shc-3.8.9.tgz
tar zxvf shc-3.8.9.tgz
cd shc-3.8.9
make

How to use SHc ?

root@server:~/shc/shc-3.8.9# shc -h
shc Version 3.8.9, Generic Script Compiler
shc Copyright (c) 1994-2012 Francisco Rosales <frosal@fi.upm.es>
shc Usage: shc [-e date] [-m addr] [-i iopt] [-x cmnd] [-l lopt] [-rvDTCAh] -f script
-e %s Expiration date in dd/mm/yyyy format [none]
-m %s Message to display upon expiration [&quot;Please contact your provider&quot;]
-f %s File name of the script to compile
-i %s Inline option for the shell interpreter i.e: -e
-x %s eXec command, as a printf format i.e: exec('%s',@ARGV);
-l %s Last shell option i.e: --
-r Relax security. Make a redistributable binary
-v Verbose compilation
-D Switch ON debug exec calls [OFF]
-T Allow binary to be traceable [no]
-C Display license and exit
-A Display abstract and exit
-h Display help and exit
Environment variables used:
Name Default Usage
CC cc C compiler command
CFLAGS C compiler flags
Please consult the shc(1) man page.

Encrypted shell script are named "*.sh.x" by default.

UnSHc is a tool to reverse the encryption of any SHc encrypted *.sh.x script.

How to use UnSHc ?

[root@server:~/unshc]$ ./unshc.sh -h
 _   _       _____ _   _
| | | |     /  ___| | | |
| | | |_ __ \ `--.| |_| | ___
| | | | '_ \ `--. \  _  |/ __|
| |_| | | | /\__/ / | | | (__
 \___/|_| |_\____/\_| |_/\___|

--- UnSHc - The shc decrypter.
--- Version: 0.6
------------------------------
UnSHc is used to decrypt script encrypted with SHc
Original idea from Luiz Octavio Duarte (LOD)
Updated and modernized by Yann CAM
- SHc   : [http://www.datsi.fi.upm.es/~frosal/]
- UnSHc : [https://www.asafety.fr/unshc-the-shc-decrypter/]
------------------------------

[*] Usage : ./unshc.sh [OPTIONS] <file.sh.x>
         -h | --help                          : print this help message
         -a OFFSET | --arc4 OFFSET            : specify the arc4() offset arbitrarily (without 0x prefix)
         -d DUMPFILE | --dumpfile DUMPFILE    : provide an object dump file (objdump -D script.sh.x > DUMPFILE)
         -s STRFILE | --stringfile STRFILE    : provide a string dump file (objdump -s script.sh.x > STRFILE)
         -o OUTFILE | --outputfile OUTFILE    : indicate the output file name

[*] e.g :
        ./unshc.sh script.sh.x
        ./unshc.sh script.sh.x -o script_decrypted.sh
        ./unshc.sh script.sh.x -a 400f9b
        ./unshc.sh script.sh.x -d /tmp/dumpfile -s /tmp/strfile
        ./unshc.sh script.sh.x -a 400f9b -d /tmp/dumpfile -s /tmp/strfile -o script_decrypted.sh

UnSHc can only decrypt SHc encrypted file on X86/x64 architecture.

• Demonstration in video :
  • https://www.youtube.com/watch?v=tmHVhMuG-Vg
• SHc (in french) :
  • https://www.asafety.fr/prog-and-dev/bashshunix-shc-le-compilateur-et-protecteur-de-script-shell/
• UnSHc (in french) :
  • https://www.asafety.fr/unshc-the-shc-decrypter/

UnSHc-MIPS

Thanks to @fffonion, a dedicated version of UnSHc has been released targeting SHc encrypted file on MIPS architecture. This UnSHc-MIPS version is available here : https://github.com/fffonion/UnSHc-MIPS

Thank you again for your work and contribution !

UnSHc-ARM

Thanks to @cliffalbert, a dedicated version of UnSHc has been released targeting SHc encrypted file on ARM architecture. This UnSHc-ARM version is available here : https://github.com/cliffalbert/UnSHc-arm

Thank you again for your work and contribution !