% shc(1) shc user manual % % August 19, 2024
shc - Generic shell script compiler
shc [ -e DATE ] [ -m MESSAGE ] [ -i IOPT ] [ -x CMD ] [ -l LOPT ] [ -o OUTFILE ] [ -2ABCDHpPSUhrv ] -f SCRIPT
shc creates a stripped binary executable version of the script specified with -f on the command line.
The binary version will get a .x extension appended by default if OUTFILE is not defined with [-o OUTFILE] option
and will usually be a bit larger in size than the original ascii code.
Generated C source code is saved in a file with the extension .x.c or in a file specified with appropriate option.
If you provide an expiration DATE with the -e option, the compiled binary will refuse to run after the date specified.
The message Please contact your provider will be displayed instead. This message can be changed with the -m option.
You can compile any kind of shell script, but you need to supply valid -i, -x and -l options.
The compiled binary will still require the shell specified in the first line of the shell code (i.e. #!/bin/sh) to be available on the system,
therefore shc does not create completely independent binaries, it mainly obfuscates the source script.
shc itself is not a compiler such as cc, it rather encodes and encrypts a shell script and generates C source code with the added expiration capability.
It then uses the system compiler to compile a stripped binary which behaves exactly like the original script.
Upon execution, the compiled binary will decrypt and execute the code with the shell -c option.
It will not give you any speed improvement as a real C program would.
shc's main purpose is to protect your shell scripts from modification or inspection. You can use it if you wish to distribute your scripts but don't want them to be easily readable by other people.
-e DATE
: Expiration date in dd/mm/yyyy format [none]
-m MESSAGE
: message to display upon expiration ["Please contact your provider"]
-f SCRIPT : File path of the script to compile
-P
: Use a pipe to feed the script, with ARGV fixes. Enabled automatically
for python, perl and csh.
-p : Use a pipe to feed the script, without ARGV fixing.
-i IOPT
: Inline option for the shell interpreter i.e: -e
-x CMD
: eXec command, as a printf format i.e: exec(\\'%s\\',@ARGV);
-l LOPT
: Last shell option i.e: --
-o OUTFILE : output to the file specified by OUTFILE
-r : Relax security. Make a redistributable binary which executes on different systems running the same operating system. You can release your binary with this option for others to use
-v : Verbose compilation
-S : Enable setuid for root callable programs
-D : Enable debug (show exec calls, etc.)
-U : Make binary execution untraceable (using strace, ptrace, truss, etc.)
-H
: Hardening. Extra security flag without root access requirement that protects against dumping, code injection, cat /proc/pid/cmdline, ptrace, etc... This feature is experimental and may not work on all systems. it requires bourne shell (sh) scripts
-C : Display license and exit
-A : Display abstract and exit
-2
: Use mmap2 system call.
-B : Compile for BusyBox
-h : Display help and exit
These can be used to provide options to the GCC Compiler. Examples: static compilation, machine architecture, sanitize options.
CC
: C compiler command [cc]
CFLAGS
: C compiler flags [none]
LDFLAGS
: Linker flags [none]
Compile a script which can be run on other systems with the trace option enabled (without -U flag):
shc -f myscript -o mybinaryCompile an untraceable binary:
shc -Uf myscript -o mybinaryCompile an untraceable binary that doesn't require root access (experimental):
shc -Hf myscript -o mybinaryThe maximum size of the script that could be executed once compiled is limited by the operating system configuration parameter _SC_ARG_MAX (see sysconf(2))
Francisco Rosales frosal@fi.upm.es Md Jahidul Hamid jahidulhamid@yahoo.com
Note: Do not contact them, they are no longer actively involved