shellc

Tool for converting shell scripts into c code

Install

cc -s shellc.c -O2 -o shellc

Compile shell scripts and generate executable programs

shellc example.sh
cc -s example.sh.c -O2 -o example -lpthread

The generated C code is example.sh.c, which is the original file name followed by .c. For programs used in production environments, it is recommended to add the parameter -s when compiling to remove the symbol table in the executable program, increasing the difficulty of disassembly and reverse engineering.

I have tried the tools shc and shellcrypt, which can compile shell scripts into executable programs. The main problems are:

• The shc command actually calls the sh -c command. The source code can be seen through the ps -ef command. The length of the shell script cannot exceed ARG_ MAX .
• Shellcrypt does not support external parameter input, and the encryption algorithm is relatively simple. The generated executable program can be decrypted by XORing with 0x000C to obtain the source code.

In addition to solving the problems of the above two tools, shellc also adds code obfuscation, randomly generating effective character position calculation functions, random character encryption, and debugging to increase the complexity of disassembly and reverse engineering.

This program is suitable for shells that can define function syntax, such as ksh, bsh, zsh, etc., and does not support csh (csh does not support function definition).Currently, the program has been tested and has practical applications in AIX, UNIX, and Linux environments.It is recommended to conduct comprehensive testing on the compiled program to prevent production failures.

If the shell script involves human-computer interaction, some modifications need to be made to the original shell script, and read input needs to be changed to read input </dev/tty.

Warning: The compiled program does not support the $0 parameter because the actual command executed by the compiled program is similar to cat script.sh | $SHELL. The value of $0 corresponds to the SHELL environment variable name，not the pre compiled script program name.

Version 3 has added untraceable and tested the following tools for untraceable

OS	TOOL	SUPPORTED
AIX 7.1	dbx sdb	YES
SCO UNIX 5.0.6	dbx sdb adb	YES
Red Hat Linux7.8	gdb	YES
CentOS Linux6.4	gdb	YES
debian 12.4.0	gdb	YES
Fedora 39	gdb lldb	YES
FreeBSD 14.0	gdb	YES
openSUSE Leap 15.5	gdb	YES
OracleLinux R9	gdb	YES
ubuntu 22.04.3	gdb lldb	YES
NetBSD 10.0	gdb	NO
DragonFly 6.4	gdb	NO
macOS 13	lldb	NO

For systems that do not support anti debugging functionality, the generated code needs to use the - t option. BSD and LINUX variant systems require thread support to enable anti debugging functionality

History

• v0.3 2023-12-25

  Add untraceable

  Fix compilation warnings in some systems

• v0.21 2023-12-13

  Fix program bugs in the zsh environment

• v0.2 2023-12-12

  Changing the data structure from a structured structure to a string array reduces compilation time for large files

  Add code character encryption function

• v0.1 2023-12-01

  Initial version